E.M. Muya, 1 P.M. Radiro, 1 P. Kahiga, 1 S. Obanyi and 2 M. Ngutu. KARI-Marsabit, P.O. Box 147, Marsabit. Abstract

80 

Loading....

Loading....

Loading....

Loading....

Loading....

Full text

(1)

Translating The Kalacha Irrigation Design Into Efficient System For Improved Productivity Of Saline-Sodic Soils In Kenya Arid And Semi-Arid Lands

E.M. Muya, P.M. Radiro, P. Kahiga, S. Obanyi and 2M. Ngutu

Corresponding Scientist: E.M. Muya: Cell: 0721904432, email: edwardmuya@yahoo. com

1KARI-Kabete, P.O. Box 14733, Nairobi 2KARI-Marsabit, P.O. Box 147, Marsabit

Abstract

The approaches for translating the Kalacha irrigation design into productive and efficient system are presented, based on the conventional design criteria. This involved detailed physical, hydraulic and topographical characterization of the soils, as well as description of different scenarios on the basis of their expected benefits under irrigated agriculture. Based on this, the current irrigation design, preliminary layout of the scheme and detailed project layout was prepared. The current irrigation design was found to be consisting of the main lined up canal with varying flow rates which terminated into irregular and haphazard water distribution networks with varied dimensions. The average flow rate of the abstracted water from the source was found to be 7.6 l/s, which reduced to . l/s through the main canal with an efficiency of 14.5%. The detailed design of the proposed scheme consisted of the fabricated head control system box that distributed the water from the source into main pipe for irrigation, night storage tank, lined canal and domestic consumption pipe. The main pipe for irrigation emerged into four distributaries, serving four blocks of irrigated fields with regular shapes, totaling 31.2 ha. The design capacity of the main irrigation pipe from abstraction point was found to be 30 l/s, while the crop water requirement (water duty) was 25.1 l/s. Based on this, the proposed design was found to have 54.5% efficiency of water abstraction, relative to the potential water supply from the source of 55 l/s. From the main irrigation pipe, three sub-mains were developed, each serving at least 10 ha with over 50 irrigation units, each unit measuring 40 by 50 m. An irrigation cycle of 7 days was calculated for the scheme with at least thirty minutes duration for each unit. The designed irrigation system was superimposed on four clusters, differentiated and delineated on the basis of the degree of land degradation and hydraulic characteristics. For all the clusters, different land use alternatives are discussed for the purpose of fine-tuning management in terms of their expected social and environmental impacts.

(2)

Soil fertility conservation management: A farmer perspective on the courses of soil fertility decline in semi-arid south eastern Kenya

*Jacinta M. Kimiti and 2David W. Odee

1South Eastern University College (A constituent College of the University of Nairobi), P.O box 170-90200, Kitui, Kenya, Cell: +254 (0) 721473341, - 733881582

2Kenya Forestry Research Institute, P.O Box 20412-00200, Nairobi *Corresponding author: jmkimiti@yahoo.com, jmkimiti@seuco.ac.ke

Abstract

A study was carried out in the semi-arid south eastern Kenya to establish soil management conservation strategies and farmer perspective on the causes of soil fertility decline in the area. Four locations were selected and random household interviews were conducted using structured questionnaire. A total of 9 households were interviewed. Results indicated that about 90% of the farmers used farmyard manure erratically due to lack of adequate labour and only about 2% used inorganic fertilizers. The farmers used inorganic fertilizers strictly for vegetable production. In addition, about 85% of the farmers used conservation structures to check soil erosion. However, about 64% of the farmers felt that the main course of soil fertility decline in the area was soil erosion. The results further revealed that between 60 and 67% of household members had only primary school education. We concluded that the most probable cause of soil decline in the study area was nutrient mining since farmers indicated that use of farmyard manure was erratic, inorganic fertilizers were only used in vegetable production and soil conservation structures were commonly used to check the worst and commonest cause of soil erosion.

(3)

Policy constraints to Promoting Uptake and Scaling up of Integrated Soil Fertility Management (ISFM) Technologies in East African Region

S.K. Kimani, Saidou Koala2 and M. Odendo

1Kenya Agricultural Research Institute, P.O. Box 57811, Nairobi, Kenya 2Tropical Soil Biology and Fertility Institute, CIAT, The African Network for Soil

Biology and Fertility (AfNet), P.O. Box 30677, Nairobi - Kenya Corresponding author: Stephen Kimani, 2skimani@gmail.com

Abstract

Results from several decades of natural resource management (NRM) research have shown that farmers in different environments can increase their farm productivity by up to 5 times if they adopted sustainable technologies that are already available. One of these technology options is ISFM, a set of soil fertility management practices that use a combination of mineral fertilizers and organic inputs, improved germplasm, knowledge of how to adapt the practices to local conditions, and which ensures agronomic efficiency of applied nutrients in order to improve crop productivity. However, despite the availability of several technologies, including ISFM, little impact has been registered so far because only a small proportion of research results or good practices are accessed and utilized by the extension workers, farmers, Non Governmental Organizations (NGO’s), the Private Sector, and policy makers. With regard to ISFM, the challenges to scaling are more complex, due to the various components which define ISFM. The major challenges to adoption and scaling include inadequate community participation, high levels of poverty, cultural issues, poor infrastructure, marketing problems, and inappropriate mechanization. Other challenges of technology transfer include weak outreach programs, inadequate Human Resource capacity, inadequate credit facilities, ineffective Partners and partnerships as well as inadequate attention to product value chain concept, and policy-induced constraints. This paper highlights the main constraints with respect to scaling ISFM in the East Africa region and the key steps that stakeholders, including governments, need to take to remedy the situation. We emphasize the particular role of policy in addressing the constraints.

(4)

Climate Variability and Crop Production in Uganda Francis M. Mwaura & Geofrey Okoboi,

1 Economic Policy Research Centre, Makerere University, P.O. Box 7841 Kampala, Uganda

Abstract

In this paper, the relationship between climate variation and crop output in Uganda for the period 1981 to 2008 is examined. The time-varying ARCH model of the crop production function is used to estimate the relationships. Analysis of the incidence of rainfall and temperature variation from the long-term average indicates that it is insignificant. Estimates of the trend of rainfall and temperature suggest a gradual decline in volume of rainfall and record of temperatures in Uganda in the present and near future. ARCH model estimates show that a positive variation in rainfall and temperature has a positive influence of crop output, while exponential increase in rainfall has detrimental effect. Also, results confirm that extensive farming -through increase in area cultivated rather than intensive farming (through use of improved technologies) remains the predominant form of increasing agricultural output in Uganda. Policy recommendations suggested in this paper among others include (i) government to support farmers to adopt small-scale irrigation systems; and (ii) strengthen of capacity of weather forecast agencies to monitor and educate the public on present and potential near-future climate variations.

(5)

Evaluation of Suitable Substrates or Substrate Combinations for Improved Oyster Mushroom (Pleurotus ostreatus) Production in Kisii Central District P N Orangi, 2F.M Kihanda and 3P Kamau

1Corresponding Author: Box 19024-00100 Nairobi, Kenya. Email: jpierre@ yahoocom.

2 Box 27-60100 Embu, Kenya Email: kihandafm@yahoo.com 3 Box 267-60200 Meru- Kenya.Email: profkamau@yahoo.com

Abstract

Oyster mushroom (Pleurotus ostreatus) is an emerging crop in Kisii Central District which is of nutritional and medicinal importance. The overall objective of this study was to evaluate the suitable substrate or substrate combinations that can be used by smallholder mushroom farmers in Kisii Central District for improved production with consideration to availability and affordability. A survey was conducted on oyster mushroom farmers in Kisii Central District using a structured questionnaire; five substrates were identified as the most commonly used substrates by mushroom farmers in the District. There was no significant difference in terms of colonization between the hanging and shelf methods. However there was very high significant difference (p=0.0001) in quality of colonization among different substrates used. There was no significant difference (p=0.2293) in yield between the two methods of production, however significant differences (p=0.0001) in yield were found in five substrates used. The best combination for yield production (464g) was that of banana fibres and maize stovers at 50% each. Oyster mushroom farmers can utilize either maize stovers, bean straw or banana fibres as potential individual substrates or in combinations for improved mushroom yield and quality. There is a great potential for mushroom production in Kisii Central District considering that maize, common beans and bananas are the major food crops in the District, hence maize stovers, bean straw and banana fibres are available and affordable for use as substrates.

(6)

Use of Aquacrop Model to Predict Maize Yields Under Depleted Rainfall and Elevated Temperature in a Semi-Arid Environment in Kenya

Joab Onyango Wamaria*, Lee Heng Khengb, Joseph Mutwiri Miritic aKenya Agricultural Research Laboratories, P. O. Box 14733-00800, Nairobi Kenya. bSoil and Water management and Crop Nutrition Section, Wagrammer Strasse 5 P.O. Box Vienna Austria Vienna 1010

cNationalAgricultural Research Centre, P.O. Box 3148-00200, Nairobi, Kenya

Abstract

There has been increasing concern that dryer and hotter seasons are becoming more frequent due to climate change especially in semi-arid environments causing adverse affects on subsistence agricultural production. Analysis of long-term (1980-2009) trends of rainfall in the first growing season (i.e. between March and July) at Katumani, Kenya showed that about 55% to the seasons were below the long-term average, with an all time low occurring in the year 2000. Although the wettest years (i.e. 1998, 1985 and 1990) had relatively higher percentages above the long-term average (i.e. 143.9%, 138.4% and 60%) compared to lower percentages (78.8%, 61.7% and 59.7%) of the driest years (1984, 2000 and 1987) the latter were relatively less in numbers (i.e. 45%). Mean seasonal temperatures however did not show high variation from the long term mean implying that rainfall was the main cause of yield variation in this area. The AquaCrop model (Ver. 3.1) was evaluated using three years (i.e. 1999, 2000 and 2001) of experimental results at Katumani gave reasonable estimates of above ground biomass and grain yield of Katumani composite maize variety. The model was then used to predict Katumani maize yields under 20% depletion of rainfall and 3oC temperature elevation scenarios. Biomass and grain yields simulated respectively ranged between 2.971 to 6.558 and 0.910 to 2.564 t/ha with probabilities of obtaining 3-5t/ha biomass and 1-2t ha-1 grain yields each dropping from 98 to 25%. Adaptation measures are given as management recommendations in line with the changed climatic scenario.

Keywords: Katumani maize composite, AQUACROP model, Semi-arid environment. Kenya

(7)

More People More Shifting Cultivation: Carbon Lost in Air and Poverty Left on Ground in Western Tanzania

F.M. Bagarama, Majule,A.E2, Kongo,V.3

1Tumbi Agricultural Research Institute, P.O. Box 306, Tabora, Tanzania Phone E-mail bagaramaf@gmail.com

2 Institute of Resource Assessment (IRA), University of Dar es Salaam, P.O Box 35097, Dar es Salaam, E-mail: amajule@ira.udsm.ac.tz

3Stockholm Environment Institute SEI Africa Centre, Institute of Resource Assessment University of Dar es Salaam,E-mail:vickongo@gmail.com

Abstract

This paper presents results of studies conducted on shifting cultivation fields in Kasulu District Western Tanzania. Shifting cultivation is the agricultural practice considered to increase land degradation. There are different forms of shifting cultivation in the Miombo woodland ecosystem cited in the literature. The shifting cultivation in the Miombo woodlands system in western Tanzania has not been investigated. The objective was to study the shifting cultivation practices as practiced by farmers in the Miombo woodlands in western Tanzania. The study was carried out in Chekenya village Kasulu, District, in Western Tanzania. The shifting cultivation in western Tanzania is characterized by complete destruction of all vegetation. The dominant species Brachystegia spiciformis, B.microphylla, B.busei, Isoberlinia globiflora and Pterocarpus angolensis are completely burnt into ash through a three phase process of debarking and tree drying, tree cutting and ash fertilization. Ash fertilization increase the soil CEC,Ca,Mg about fourfold, while soil available P is increased about 230%.However,poor agronomic practices including low plant populations, use of cultivars with low genetic yield potential and lack of adequate methods of crop pests control reduce the expected benefits of ash fertilization. The study shows that economic benefit was realized only in the year of cassava growing, maize and bean yields are low. Indicators of soil productivity decline during the cropping cycle include increased density of spear grass (Imperata cylindrica L. Beauv.), Bidens pilosa Linn. Ageratum conyzoides Linn and Hyparrhenia rufa (Nees) Stapf.The cropping cycle indicate the Land Use Factor of 10 characteristic of subsistence farming.

Key words: Ash fertilization, cropping cycle, economic benefit; miombo woodlands, shifting cultivation,

(8)

THE POTENTIALS FOR INVESTMENT IN MOUNTAIN AND OASIS AREAS OF KENYA ARID AND SEMI-ARID LANDS FOR IMPROVED PRODUCTIVITY OF SALINE-SODIC SOILS

E.M. Muya, S. Obanyi, P.M. Radiro, P.M.Kahiga 2H. Bulle, 2M. Ngutu, 2S. Kuria and 2M. Okoti

Corresponding Scientist: E.M. Muya: Cell: 0721904432, email: edwardmuya@yahoo. com

1KARI-Kabete, P.O. Box 14733, Nairobi 2KARI-Marsabit, P.O. Box 147, Marsabit

ABSTRACT

This paper provides the road map to the exploitation of the resources in mountain and oasis areas of Kenya arid and semi-arid lands through an assessment of biophysical production potentials of the area. This was achieved through soil survey carried out to identify and delineate different soil units, based on quantified soil quality attributes. Using GPS, soil units were delineated, based on the differences in the observed soil characteristics. Based on these characteristics and adaptive capacity of people to climate change, the potentials for investment were found in rainfed, irrigated and severely degraded areas. In rainfed areas, investment in wheat production, through adoption of the recommended technologies, was found to be the most viable enterprise, with maximum yield of 2,7 kg/ha. For irrigated areas, there were ample opportunities for commercialized production of crops and forage on condition that the soil structure degradation, due to high sodium concentration is addressed. In extremely degraded areas, natural occurrence of Acacia and Prosopis, offered the opportunities for environmental conservation and commercialized production of gums and resins as well as Prosopis products.

(9)

Quality characteristics of manures produced from the central Kenya highlands

Francis M. Kihanda and C.M. Rimui

Kenya Agricultural Research Institute, Embu, P.O. Box 27- 60100 Embu Kenya

E-mail: kihandafm@yahoo.com

Abstract

Soil fertility is one of the major problems leading to decline in crop productivity in central Kenya highlands. The farmers rely heavily on farmyard manure (FYM) to improve soil and crop productivity. A study was therefore conducted to characterize the manures produced and utilized at the farm level in terms of their nutrient content and N- mineralization patterns. A total of 48 manure samples were collected along a longitudinal gradient. The manures were categorized into three groups namely, low, medium, and high quality based on the C:N ratio of the manure. Using the three manure types and with two soil types, a pot experiment was designed using crop N- uptake as a measure of mineralization. The study indicated that FYM produced in the area were variable in their nutrient composition mainly total N, organic C, Ca and K and ash content. The FYM samples were found to be low in phosphorus. There was immobilization of mineral N derived from all the FYM tested in the first 4 weeks of incubation, higher immobilization being observed in FYM of high C:N ratio. The N mineralization from the FYM was between 0 and 40% of the total N in the FYM, the high mineralization being observed in the FYM of low C: N ratio and immobilization being observed in FYM of high C:N ratio during a 12-week incubation period. The soil type appeared to influence the mineralization of the three FYM types higher mineralization being observed in the near neutral soil than the acidic soil. The effect of the soil on the mineralization of the FYM were more pronounced in FYM of high C:N ratio.

(10)

Capacity Development in Soil Science Knowledge for Increased Food Production on Smallholder Farms in Central Kenya

Making agri-food systems work for the rural poor in Kenya

Peterson N. M. Njeru*, Immaculate Maina2, Maureen Miruka2, Josiah Gitari3 , Mabel Mahasi4, Henry Mwangi4, Stephen K. Kimani and Festus Muriithi2

1Kenya Agricultural Research Institute, Muguga south P.O. Box 30148-00100, City Square, Nairobi, Kenya; email: njerupeterson@yahoo.com, njerupeterson@gmail. com

2Kenya Agricultural Research Institute, Headquarters 3Kenya Agricultural Research Institute, Embu,

4Mabel Mahasi, Kenya Agricultural Research Institute, Njoro ABSTRACT

Soil fertility degradation remains the major biophysical cause of declining per capita crop production on smallholder farms in sub-Saharan Africa. Appropriate soil fertility regimes, are therefore, critical for improved crop productivity in central Kenya. A study was conducted to determine soil fertility status and present soil analysis results in an organized feedback workshop in Nyandarua North District, Kirinyaga West District and Mbeere South Districts of Kenya. Soil samples were taken at random from 6 farmers’ groups and 6 sole farmers’ fields in each district, at a surface depth (0–20 cm) for subsequent physical and chemical analyses. Results from the feedback workshop indicated that farmer’s soil management practices contributed to problem soils (acidic soils) in Nyandarua and Kirinyaga District. This was as a result of continuous use of DAP fertilizers which lead to low pH levels of 3.4 to 5.5. There was need therefore to have extension advisory services closer to the farmers to reduce the gap. The low knowledge by farmers on integrated soil fertility management regimes is problematic. Extension staffs also need to understand soil fertility management techniques, skills in understanding problem soils and recommended fertilization regimes. The gap between the farmers and extension services was as a result of few testing laboratories in Kenya, awareness to farmers and extension staff on soil analysis which are very expensive to smallholder farmers. There is need therefore to develop and implement mechanisms tailored to ensuring farmers adopt appropriate agronomic practices for enhanced crop production on smallholder farms in central Kenya.

(11)

The effect of soil and plant mineral nutrition on rice blast in Mwea Irrigation scheme of Central Kenya

Muriithi C, E.N. Mugai2 A.W.Kihurani and F.Kihanda 1Kenya Agricultural Research Institute, Embu

2Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya +Corresponding author; E-mail:cmuriith2005@yahoo.com

Abstract

Rice (Oryza sativa L) is a staple food for nearly-half of the world population contributing over 20% of total world calorie intake. In Kenya it is the third most important cereal after maize and wheat. However, rice blast, caused by Pyricularia oryzae is one of the most important rice disease in the wide. In Kenya the disease has been reported to cause over 50% yield loss. Work was carried out in Mwea Agricultural Development Centre (MIAD) in Kirinyaga district of Central Kenya to determine the levels of nutrients status in soil and plants tissue on infection of rice by Pyricularia oryzae. Soil and plants sample were obtained from (MIAD) in Mwea location in the fields that were infected with the rice blast and in a non-infected field. Soil was collected from 0-15 and 15-30cm. Both soil and plants were analyzed for nitrogen, phosphorous, potassium and silicon. Results indicated the level of phosphorous in the soil did not seem to influence the incidence of rice blast disease. However, it was observed that the highest infection of rice blast was in the soil that had high level of nitrogen and lowest where silicon was high in both top and sub soil. Similarly, rice blast infected plants infected plants had higher nitrogen and lower silicon concentration than in non-infected plants. Potassium too was higher in non-infected plants while infected plant indicated a lower concentration. There is need therefore to determine the optimal level of nitrogen and silicon to reduce the incidence of rice blast.

(12)

Establishing a Suitable Rate and Mode of Applying Lime to Reduce Soil Acidity in Western Kenya

Kiplagat J . K., J. R. Okalebo, C.K. Serrem, D. S. Mbakaya2, J. Bashir3 1 Moi University-Chepkoilel University college, Department of Soil Science, P.O. Box

1125-30100, Eldoret, Kenya.

2 Kenya Agricultural Research Institute KARI-Kakamega, P.O. Box 169 Kakamega 3 AGRA, Nairobi, P.O. Box 66773-00800, Westlands, Nairobi. Kenya. Contact author’s email: kigenj@gmail.com

Abstract

In Kenya, acid soils cover about 13 % of total land area and are distributed widely in the croplands of central and western Kenya regions. A study aimed at assessing the economics of four lime rates (0, 2, 4 and 6t/ha) and three application methods (spot, band and broadcast) in terms of maize performance in the two target districts of Western Kenya. On farm experiment was conducted in 2010 LRs and SRs at four sites within Siaya and North Kakamega district, laid out in a 3x4 factorial in RCBD with 4 replications. Lime was applied but with phosphorus as (TSP) and nitrogen as (CAN) applied as blankets at the rate of 26kg/ha P and 75kg/ha N. Application of lime lead to increase in soil pH in both districts, by 1.08 in Siaya district with broadcast of 6 t/ha lime and 0.78 with banding 6 t/ha lime reflecting the grain yield. Highest grain yield increased on average from 1.67 t/ha (control) to 4.37 t/ha (6 t/ha lime by broadcast method) in Siaya district. While in North Kakamega district it increased from 1.49 t/ha to 3.14 t/ha (6 t/ha lime applied by band method). The cost of applying lime differed with method, band was found to be cheaper and broadcast was expensive since a farmer has to tilth entire farm. Therefore, with the current results it can be inferred that the methods of applying lime for the two districts vary due to differences in soil type and climatic conditions.

(13)

Influence of Soil Organic Matter Quality on Temperature Sensitivity of Decomposition of a Tropical Forest-Cropland Chronosequence CALEB BASWETI*, NANCY KARANJA* and LOUIS VERCHOT§

*Department of Land Resources Management and Agricultural Technology, University of Nairobi, P.O. Box 30193, Nairobi, Kenya, §Centre for International Forestry Research

(CIFOR), P.O. Box 0113 BOCBD, Bogor 16000, Indonesia. Abstract

Temperature sensitivity of soil carbon decomposition is a key factor in determining the response of the terrestrial carbon balance to climate change. However, the effect of substrate on temperature sensitivity of decomposition has not been incorporated into the carbon cycle models because the differences between recalcitrant and labile carbon pools have not been demonstrated. The objective of the study was to evaluate the effect of organic matter quality on temperature sensitivity of soil organic matter (SOM) decomposition under three temperature levels and two soil moisture levels. A chronosequence approach was used to obtain organic matter with varying quality attributes across a cultivation chronosequence in which land-use history ranged from a recently converted primary forest to 80 years of continuous cropping in the highlands of Western Kenya. From each conversion time, soil was sampled to a 10 cm depth in three replicates in January 2009 and incubated for carbon dioxide (CO2) evolution at three temperature levels (10oC, 25oC and 33oC) and two soil water content levels (50% and 100% water holding capacity - WHC). Total carbon (C) and nitrogen (N) was analyzed using dry combustion method while SOM quality was characterized using Mid-Infrared spectroscopy. Total C and N loss for the past 80 years of cultivation was found to range between 60 and 70% in old cultivated soils. Decomposition rates increased linearly (R2 = 0.99; P<0.001) with temperature for both forest and cultivated soils with higher emissions coming from forest soils. The effect of water content on the rate of CO2 emission resulted to lower emissions at 100% WHC and highest at 50% WHC. Rates of emission per unit increase in temperature were higher at 50% compared to 100% water content with forest and recently converted soils recording higher rates in the first seven days of incubation. Proportions of recalcitrant carbon pools increased with cultivation period. Recalcitrant organic matter pools were found to influence (P<0.05) temperature sensitivity of decomposition at different incubation periods subject to water content levels. The Q10 values for both forest and cultivated soils were similar at 100% WHC while at 50% Old- and Mid- cultivated soils were more sensitive to temperature than recently cultivated and forest soils at the initial seven days of incubation. This study clearly indicates that soil organic matter decomposition is significantly affected by soil temperature, water content and soil organic matter quality which is influenced by the land-use change and the cultivation period. Incorporation of the three factors; temperature, water content and organic matter quality into carbon cycle models will help in predicting the effect of climate change on SOC storage. It will also help in managing SOC content in various landscapes through improved land management that will also reclaim C released to the atmosphere due to land use change.

(14)

Effects of tillage on soil bulk density, crust strength, water content and yield of maize and cowpea on a sandy loam soil

J.M. Miriti*, G. Kironchi2, C.K.K. Gachene 2, A.O. Esilaba3 and D.M. Mwangi3

1Kenya Agricultural Research Institute (KARI), ARC Muguga South Centre, P.O. 30148-00200 Nairobi, Kenya

2University of Nairobi, Kabete Campus, P.O. Box 30197-00100 Nairobi, Kenya 3Kenya Agricultural Research Institute (KARI) Headquarters, P.O. Box 57811-00200 Nairobi, Kenya

*Corresponding author. Tel: +254 722 865 683, Fax: +254 20 4183344, Email: jmmiriti@yahoo.co.uk

Abstract

During 2007-2010, a field experiment was conducted to evaluate the effects of three tillage practices on soil water conservation and crop yield on a semi-arid sandy loam soil in eastern Kenya. Tillage practices namely tied-ridges (TR), subsoiling and ripping (SR) and ox-ploughing (OP) were evaluated under maize sole crop (SM), cowpea sole crop (SC) and maize-cowpea intercrop (MC) cropping systems. Treatments were arranged in split plots with tillage practices as the main plots and cropping systems as the sub-plots in a Completely Randomized Block Design (CRBD), replicated three times. The results showed that tillage significantly (Pd”0.05 influenced soil surface (0-5 cm) bulk density, crust strength and saturated hydraulic conductivity (Ks) between crop rows (inter-row) but not within rows (in-row). The inter-row soil under SR was more (Pd”0.05) compacted than the soil under OP and TR. Inter-row total porosity and Ks were lowest in TR and highest in OP tillage. The soil under OP conserved more soil water than the soil under SR but significantly lower than under TR. The average soil water content of 206.9 mm in SM treatments was significantly greater than the water content in MC (199.6 mm) and SC (197.9 mm). There was a significant interaction between tillage and cropping systems on soil water. Although maize and cowpea sole crop yields were not significantly affected by the tillage methods, TR did tend to have the highest yields while SR had the lowest. The intercrop yields under TR were significantly greater than the yields under SR and OP.

(15)

Does Crotalaria Residues Used as a Source of Nitrogen (N) for Maize Fertilization Require any Mineral N Supplementation?

J.N. Gitari*, J.G. Mureithi2, C.K.K. Gachene3 and D.N. Mugendi4 and J.B. Kung’u4 1Kenya Agricultural Research Institute, P.O Box 27-60100, Embu, Kenya. Email: gitarijosiah@yahoo.com (*Corresponding author).

2Kenya Agricultural Research Institute, P.O Box 57811, Nairobi, Kenya.

3Department of Land Resource Management and Agricultural Technology, University of Nairobi, Kenya.

4Department of Environmental Science, Kenyatta University P.O Box 43844, Kenya.

ABSTRACT

Degraded soils are a major constraint to agricultural production and food security in the central highlands of Kenya. Many of the smallholder farmers are low resource endowed giving them a narrow scope for implementing farm interventions based on purchased external inputs. The integration of crotalaria [Crotalaria ochroleuca G. Don] (a high biomass producing, N2-fixing herbaceous legume) is proposed as a useful means of overcoming the current trend in low soil fertility status. By integrating this legume into the existing maize planting patterns, the resultant legume herbage may be used as a source of N for maize crop nutrition and general soil fertility improvement. A field study was therefore carried out at Embu, Kenya to determine if there is need for mineral N supplementation to these legume residues. There were large seasonal variations in legume biomass generation. On average, about 2.0-4.5 Mg ha-1 of legume herbage contributing 30-80 kg N ha-1 was generated. These herbage quantities had some implication on maize responses for the individual cropping seasons. The effect of legume residue incorporation on maize growth was evident throughout the entire growth cycle of the maize crop. Plots with none or low quantities of legume residues where no mineral N was supplemented gave low grain and stover yields indicating the effectiveness of these residues as a source of N. Averaged across the five cropping seasons, plots with crotalaria residues alone (no mineral N) produced 2.3 times more grain than the unamended control. The study established that biomass quantities in excess of 2.0 Mg ha-1 may not require any mineral N supplementation.

Key words: Maize, crotalaria, intercropping, legume residues, Humic Nitisols, Central highlands of Kenya

(16)

Lake Nakuru’s Bacteria Diversity and their Ability to Degrade Polythene Lucy W. Wanjohi

Abstract

Waste management, especially the abundantly produced polythenes remains the biggest challenges in Kenyan urban areas and have become the main degraders of all ecosystems even the protected areas. Although a number of efforts are being sort in waste management none has addressed degradability of the wastes. This study focuses of identification of bacteria diversity in Lake Nakuru and available bacteria ability to degrade disposable plastics and polythene papers. Lake Nakuru is a saline lake suspected to be rich with halophilic bacteria, recognized for their ability to breakdown matter. Samples were collected in five different eco-zones at different water depth once every month for half a year. Chemicals and physical conditions were recorded at every site at every sampling time. Through laboratory procedures bacteria load were determined by counting the number of colonies formed (CFU). Different types of bacteria have been isolated forming colonies of different colours including white, cream, blue-green, yellow and orange. Bacteria load and diversity differed with ecozones, duration of sampling and depth of sample collection. Ability of bacteria to degrade plastic and polythene was influenced by different colonies.

(17)

Effectiveness of Liming and Phosphorus Fertilizer Materials on Maize Production in Western Kenya Acid Soils

V. S. OMENYO, J. R. OKALEBO, C. OTHIENO, J. K. KIPLAGAT, J. MBINGO-1, D. S. MBAKAYA2, B. JAMA3

1Moi University – Chepkoilel University College, P. O. Box 1125, Eldoret, Kenya 2Kenya Agricultural Research Institute Kakamega, P. O Box 159, Kakamega, Kenya

3AGRA, Eden square Block 1 5th floor, P. O Box 66773 – 00800, Westlands Nairobi, Kenya

Corresponding author: omenyoz@yahoo.co.uk ABSTRACT

Soil fertility depletion and acidity in smallholder farms is a fundamental biophysical root cause of the declining per capita food production, and has largely contributed to poverty and food insecurity in Kenya. Farmers have dismally low yields (<1t ha-1 season-1 maize) in comparison to the potential estimates of 6 – 8 t ha -1season-1. An on farm research was conducted during the 2010 long and short rains in selected sites (Kakamega North & Ugenya districts) to evaluate direct and residual effects of various lime sources on Phosphorous availability and maize yields. This comprised of agricultural lime from Koru, (20.8 % CaO) and Athi River, (45 % CaO), Minjingu phosphate rock (MPR) (38% CaO,) and Mavuno fertilizer (10% CaO,). Two separate experiments were carried out. First, the two agricultural limes were used to determine the effective lime rate affordable to the smallholder farmers. The second experiment tested the effectiveness of the four liming materials on P availability and maize yields. Results indicated significant (p<0.05) responses of pH and maize yield to the soil amendments material applied. At 3 t ha-1 lime, pH increased from 4.92 (control) to 6.22, 120 DAP in Ugenya and 4.63 (control) to 5.51 in Kakamega North. Maize yield increased from 1.04 (control) to 6.72t ha-1 (Ugenya), and .2(control) to 4.72t ha-1 (Kakamega North)where Mavuno was applied. The high yield by Mavuno could be due to additional nutrients it contains. An economic analysis is underway, for an effective and economical package for smallholder farmers in this region.

(18)

ISFM Knowledge Levels and Training Needs of Smallholder Farmers in The Central Highlands Of Kenya

Macharia1 J.M., Mucheru-Muna1 M., Mugwe1 J.N., Mairura2 F.S. and Mugendi1 D.N.

1 Kenyatta University, P.O Box 43844, Nairobi, Kenya

2 Tropical Soil Biology and Fertility, P.O Box 30677, Nairobi, Kenya Corresponding author: machariamjoseph@gmail.com

Abstract

Soil nutrient depletion has been recognized as one of the major biophysical constraints affecting agricultural production in Sub Saharan Africa. Despite past research that has developed various soil fertility management options, few technologies from past soil research have been adopted and utilized by target farmers. Poor technology adoption is associated with low levels of knowledge and awareness by farmers. This study was carried out to assess the knowledge levels and consequently the training needs of smallholder farmers on soil fertility technologies in Central Kenya where 300 farm households were randomly selected. Questionnaires and field observations were used to gather data. The data was analyzed using SPSS. Results indicate that majority of the respondents (69%) had moderate levels of knowledge on Integrated Soil Fertility Management (ISFM) technologies. A logistic regression model identified household size, number of groups, extent of training, and use of ISFM technologies to significantly influence the ISFM knowledge levels held by farmers.. The priority training needs of farmers included knowledge and skills in soil fertility testing, organic fertiliser utilization and liming, while their most preferred training methods were field days and on-farm demonstrations. There is need to improve farmers’ levels of knowledge through training, taking into account socio-demographic characteristics, especially gender, age, household size and labour availability, farming experience, group membership and farm size. Farmer training needs and preferred training methods should also be taken into account. Policies are needed so as to support practical and participatory approaches to ISFM technology dissemination. This will lead to enhanced ISFM adoption, increased crop production, poverty reduction and environmental conservation.

Key words: Demonstrations; Field days; Organic fertilizers; Socio-economic factors; Technology preference

(19)

Suitability of Soil, Manure, and Irrigation Water for Jatropha curcas Production in a Semi Arid Area in the Eastern Rift Valley of Kenya

Githunguri C. M, M. Radiro and A. Nguru Abstract

Jatropha curcas is a promising drought tolerant bio-fuels feedstock in Kenya. A study to establish the suitability of soil, manure, and irrigation water for Jatropha curcas production in a farm situated in a semi-arid area in the Rift Valley with a view to making appropriate recommendations on its improvement. The results indicate there is low cation exchange capacity in the soils of the farm. The soils had low levels of Ca2+, PO4-, Cu, and NO3-. The soils also had high levels of K+, Fe, Mn, and SO42-. The soils were very slightly alkaline and deficient in Ca2+ and Cu, which could be supplemented to ensure optimum Jatropha curcas growth and development. The soils had sufficient NO3, Mg2+, Na+, Zn and Mn. Results of the nursery indicate the 3 major nutrients NO

3, PO4-, and Ca2+ and a trace element, Cu, must be supplemented for proper growth and development of Jatropha curcas. The soils have sufficient Mg2+, Na+, and Zn but excessive K+, Fe, Mn, and SO42. Both cattle and goat manure in the farm had high pH and low levels of all nutrients, which ought to be fortified. There are low levels of Mg2+ and NO3and high levels of PO4- and K+ of irrigation water samples from the spring within the farm. The soil samples had 10 nematodes of Meloidogyne spp isolated per gram of soil, which was exceptionally high. Aspergillus spp and Botrytis spp, which are responsible for causing black and grey, moulds, respectively, were present in the soils.

(20)

Soil agricultural constraints evaluation using infrared scanning in east of Democratic Republic of Congo

Bashagaluke J*.1, 3, Mulumuna J,2, Walangululu J.,2, Mochoge B3, Mugwe J3 , Vanlauwe B4, Pypers P4. ; Boeckx P.2

1. Université Catholique De Bukavu (UCB), DR Congo.

2 Laboratory of Applied Physical Chemistry – ISOFYS, Faculty of Bioscience Engineering, Ghent University, Coupure 653, 9000 Gent, Belgium.

3. School of Agriculture /.of Kenyatta University, KENYA NAIROBI

4 Tropical Soil Biology and Fertility of the International Institute of Tropical Agriculture (TSBF-CIAT), Nairobi, Kenya.

*corresponding author: E-mail: bashbigabwa@yahoo.fr Abstract

Near infrared reflectance (NIR) and mid-infrared (MIR) spectroscopy techniques are rapid, convenient and simple non-destructive techniques for quantifying several soil properties. This study uses MIR method to predict pH, soil organic C, total N, exchangeable Al, Ca, Mg, and K, CEC and soil texture for soil samples collected in Sud-Kivu, Democratic Republic of Congo. A total of 536 composite soil samples were taken from two locations (Burhale and Luhihi) at two depths (0-20 and 20-40 cm) using a spatially-stratified random sampling design within an area of 200 km2. Differences in characteristics were evaluated between the two locations, land use (cultivated vs. non-agricultural land) and soil depth. A random subset of the samples (10%) were analyzed using standard wet chemistry methods, and calibration models developed using MIR data to estimate soil properties for the full soil sample set. Partial least squares regression (PLS) method gave acceptable coefficients of determination between 0.71 and 0.93 for all parameters. Soil organic matter levels were higher in cultivated plots in Luhihi (3.9% C) than in Burhale (3.0% C), suggesting lower levels of soil fertility in the latter area. This indicates high levels of acidity, which are likely to limit crop production in the area. Phosphorus deficiency is acute for Burhale (2.4 mg P kg-1) but less for Luhihi (5.4 mg P kg-1). In both locations, low levels of Ca and Mg indicate that soils may be susceptible to deficiencies in both elements.These findings provide new opportunities for monitoring soil quality in the region which can benefit multiple actors in the agricultural and environmental sectors.

Keywords: Near infrared, soil scanning, PLS regression, soil characterisation, soil map.

(21)

Assessment of ISFM Knowledge and Training Needs Of Smallholder Farmers in the Central Highlands Of Kenya

Macharia J.M. , Mucheru-Muna M. , Mugwe J.N., Mairura F.S. 2 and Mugendi D.N. 1Kenyatta University, P.O Box 43844, Nairobi, Kenya

2Tropical Soil Biology and Fertility, P.O Box 30677, Nairobi, Kenya Corresponding author: machariamjoseph@gmail.com Abstract

Soil nutrient depletion has been recognized as one of the major biophysical constraints affecting agricultural production in Sub Saharan Africa. Despite past research that has developed various soil fertility management options, few technologies from past soil research have been adopted and utilized by target farmers. Poor technology adoption has been associated with low levels of knowledge and unawareness by farmers as well

as lack of information on their training needs. This study was carried out to assess the knowledge levels and consequently the training needs of smallholder farmers on soil

fertility technologies in central Kenya, where 300 farm households were randomly selected. Questionnaires and field observations were used to gather data. The data was analyzed using SPSS software. Results indicate that majority of the respondents

(69%) had moderate levels of knowledge on Integrated Soil Fertility Management (ISFM) technologies. A logistic regression model identified household size, number of groups, extent of training, and use of ISFM technologies to significantly influence

the ISFM knowledge levels held by farmers. The priority training needs of farmers included knowledge and skills in soil fertility testing, organic fertiliser utilization and liming, while their most preferred training methods were field days and on-farm demonstrations. In order to achieve food security in Africa, there is need to improve farmers’ levels of knowledge through training, taking into account socio-demographic

characteristics, especially gender, household size, labour availability, group membership and farm size. Farmers’ training needs and preferred training methods

should also be taken into

account. Policies are needed so as to support practical and participatory approaches to ISFM technology dissemination. This will lead to enhanced ISFM adoption, increased crop production, poverty reduction and environmental conservation.

Key words: Demonstrations; Field days; Organic fertilizers; Socio-economic factors; Technology preference; food security

(22)

Genetic Diversity of Indigenous Rhizobia and Rhizobial Inoculants And Effects Of Inoculation On Biomass Yield And Nodulation in two Legume Species In

Kenya

Samuel Mathu , 2, Pieter Pypers , Laetitia Herrmann , Viviene Matiru 2 Romano Mwirichia 2 and Didier Lesueur 3

1Tropical Soil Biology and Fertility Institute of CIAT, World Agroforestry Center, P.O. Box 30677-00100 Nairobi – Kenya.

2Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000-00200 Nairobi- Kenya.

3CIRAD, Persyst department UPR 80 “Ecosystems of plantations”, Tropical Soil Biology and Fertility institute of CIAT, World Agroforestry Center, P.O. Box

30677-00100 Nairobi – Kenya. ABSTRACT

Small scale farmers in Kenya are faced with declining soil fertility, high fertilizer costs and inadequate inoculant use, the identification of effective indigenous Bradyrhizobium strains which nodulate cowpea and green gram could be useful in the development of inoculants. The objectives of this study were, to assess the genetic diversity of indigenous Bradyrhizobium strains and those in rhizobial inoculants based on Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) of the 16S-23S rDNA intergenic spacer (IGS) region, and evaluate their effect as compared with rhizobial inoculants on biomass yield and nodulation. Two experiments were set up under green house conditions, for the first experiment, soils were collected from ten sites in Kenya to trap indigenous rhizobia using cowpea and green gram as trap hosts. A second experiment was set up to evaluate the response of both crops to commercial rhizobium inoculants in soil from Coastal Kenya. Inoculation had no significant effect on shoot dry weight and nodule fresh weight in both crops. Genetic diversity of strains nodulating the two legume species in both experiments was assayed using the PCR-RFLP analysis. Strains with identical restriction fragment profiles were classified into the same IGS group. 19 and 6 IGS groups were distinguished respectively, from both experiments. Predominant IGS groups in the first experiment were I and II. In the second experiment, nodule occupancy by indigenous strains was 100 % in both crops. IGS group III was predominant in nodules from both legumes and present in all treatments. The diversity identified in Bradyrhizobium populations in the soils represent a valuable genetic resource that has potential utility for the selection of competitive and effective strains to improve BNF and thus increase legume yields at low cost.

(23)

Effects of soil management technologies on rice production in Mvomero District, Morogoro, Tanzania

E. Laisser, S. T. Ikerra2, L.L.L. Lulandala3.

1Sokoine University of Agriculture, P.O Box 3000, Morogoro, Tanzania; 2Agricultural Research Institute, P.O Box 5088, Mlingano, Tanga. 3 Sokoine University of

Agriculture,P.O Box,3000, Morogoro, Tanzania

ABSTRACT

A study was conducted in Mvomero District, Morogoro Region to assess the effects of soil management technologies on rice production. The study employed a Randomized Completely Block Design (RCBD), three replications and 12 treatments. The plot size was 3m x 3m. Seedlings transplanted at a spacing of 20cm x 20cm. Treatments included the followings: Control; (30kg P; 40kg N; 80kg N; 30kg P+40kg N ; 30kg P+80kg; FYM; 30kg P+ FYM; 40kg N+FYM; 80kg N+FYM; 30kg P+40kg N +FYM; and 30kg P+80kg N+FYM) ha-1. Fertilizers were applied at transplanting, N fertilizer was applied in two splits, during transplanting and during rice booting. Data collected include, soil analysis before planting and after harvesting, FYM analysis. Other data include days to 50% flowering, plant height, tillers and panicles number plant-1, panicle weight, a 1000 grain weight, % grain filling and grain yield. Concentration of total N and P in plant tissues were determined. All data collected were subjected to statistical analysis using MSTAT-C statistical program. Duncan’s New Multiple Range Test was used to compare differences between treatment means. Results indicated that a combination of 30kg P ha-1+80kg N ha-1+ FYM significantly recorded highest grain yield, also had higher values of the studied parameters. Plots which received farm yard manure alone significantly yielded better than the control plots. Also in plots where FYM combined with inorganic fertilizers, crop response in yields was better compared to when either of the sources was applied alone. Integration of nitrogen fixing plants and other sources of FYM should also be considered.

(24)

Response of rice to different levels of nitrogen and lablab on soils of Morogoro rural, Morogoro region, Tanzania.

M. K. mzimbiri, S. T. Ikerra2 and J. R. M. Semoka3

1ARI-Uyole, P.O Box 400, Mbeya, Tanzania; 2ARI-Mlingano, P.O Box 5088, Tanga, Tanzania; 3Department of Soil Science, Sokoine University of Agriculture, P.O Box 3008, Morogoro. (e-mail: mhamadimzimbiri2000@yahoo.co.uk; susikera@yahoo. com; semoka@yahoo.com)

Abstract

Inadequate supply of N is an important constraint to productivity of lowland rice. Limited or no information is available on the use of green manure especial lablab on increasing Nitrogen in rice fields. A study was conducted in response of rice to different levels of nitrogen and lablab on soils of Morogoro. Field and pot experiment were conducted at Kiroka village and SUA in screen house, respectively. Twelve treatments were arranged in a RCBD with three replications. The treatments were Absolute control , N40 (Urea) + P30, N40 (Lablab) + P30, N20 (Urea) + N20 (Lablab) + P30, N80 (Urea) + P30, N80 (Lablab) + P30, N40 (Urea) + N40 (Lablab) + P30, N120 (Urea) + P30 , N120 (Lablab) + P30, N60 (Urea) + N60 (Lablab) + P30, N6.0 (roots) + P30 and N80 (Lablab) + P0. Routine soil analysis showed that, fertility status of the site was rated as medium to high except for N and OC which showed very low and low, respectively. The soil fertility monitored after incorporation of lablab improved Nitrogen from 0.06 to 0.37 % and Phosphorus from 17.00 to 28.29 mg/kg. The results of this study revealed that rice receiving 120 kg N/ ha through Urea gave the highest yield (4.1 t/ha) followed by treatment with partially through lablab 60 kg N/ha and 60 kg N/ha from urea (3.7 t /ha). Control treatment gave 2.0 t/ha. Nitrogen application significantly increased rice grain yield, growth characters and yield parameters. Good correlations were found between grain yield and other yield parameters. It is concluded that, lablab incorporated into the soil increased plant nutrients like N and P significantly. Its combination with inorganic fertilizer like urea can increase rice grain yields. Keywords: Rice grain yield, green manure (lablab), soil and plant nutrients

(25)

The Potential of fuel in Uganda: An Assessment of Land Resources for Bio-fuel Feedstock Suitability

Isabirye M*., Kitutu M2., Yemeline V3.

1Faculty of Natural Resources and Environment, Namasagali Campus, Busitema University, P.O. Box 1 Kamuli

2National Environment Management Authority, P.O. Box 22255, Kampala 3UNEP/GRID-Arendal, Norway

* Corresponding author: isabiryemoses@yahoo.com Abstract

Bio-fuel production is rooting in Uganda amidst problems of malnutrition and looming food insecurity, and environmental degradation. Meanwhile, controversy surrounds the sustainability of bio-fuels as source of bio-fuel in Uganda with proponents and opponents having convincing reasons. There is concern that bio-fuel feedstock production is likely to aggravate food insecurity and environmental degradation. It is also apparent that bio-fuels can provide clean transportation fuel while contributing to rural poverty alleviation. Given the above circumstances, adequate studies are required to determine the amount of feedstock or energy the agricultural and forestry sector can sustainably provide, the adequacy of land resources of Uganda to produce the quantity of biomass needed to meet demands for food, feed, fiber and also to provide energy. This study was conducted under the framework of the National Environment Information Network with a major objective of assessing the suitability of land resources for bio-fuel production and identifying relevant policy options that seek to integrate bio-fuel feedstock production into the land use planning process.

Focusing on Jatropha, Sugarcane, Oil palm and Maize as bio-fuel feedstocks this report presents the suitability of land resources for bio-fuel feedstock and implications for food availability, rural poverty alleviation and environmental degradation. Areas of research focus and policy review options are highlighted.

(26)

Per Capita Cost Of Soil Erosion Trends in Uganda 2000 - 2010 Isabirye M*., Magunda M2., Kitutu M3., Mpabulungi P3., Opio J2

1Faculty of Natural Resources and Environment, Namasagali Campus, Busitema University, P.O. Box 1 Kamuli

2National Agricultural Research Organisation,

Kawanda Agricultural Research Institute, Kampala, Uganda.

3National Environment Management Authority, P.O. Box 22255, Kampala * Corresponding author: isabiryemoses@yahoo.com

Abstract

Failure to translate results of biophysical assessment has been observed as a key communication hurdle hindering the use research results by policy makers and stakeholders. Research products of soil erosion have largely been reported as quantities of soil loss per hectare per year. Fewer attempts have been made to translate these losses into economic terms. Soil loss at a National level was determined using the Universal Soil Loss Equation. Economic analyses done where translated into pa capita soil loss. The average annual cost of soil erosion pa capita is USD 4.3 and it is on the decline. The annual risk of soil erosion pa capita is USD 470; a value higher than the GNI per capita of USD 420. The declining rates reflect the increasing impact of mitigation measures in place by various stakeholders.

Keywords: Soil erosion, economic assessment, mitigation measures

(27)

Soil erosion rates in tropical villages: A case study from the Lake Victoria Basin, Uganda

A. De Meyer*, J. Poesen, M. Isabirye2, J. Deckers, D. Raes

1Katholieke Universiteit Leuven, Department Earth and Environmental Sciences, Celestijnenlaan 200 E, 3001 Leuven, Belgium;

2National Agricultural Research Organisation, Kawanda Agricultural Research Institute, Kampala, Uganda. ABSTRACT

In an effort to pinpoint the sources of sediment pollution in Lake Victoria, the contribution of sediment from compounds, landing sites, unpaved roads and footpaths is determined in the catchment of Nabera Bay and Kafunda Bay at the northern shore of Lake Victoria in southern Uganda. The volume of soil loss is determined in 36 compounds, 1 school and 1 landing site by the reconstruction of the original and current soil surface using botanical and man-made datable objects. The soil loss rates are then calculated by dividing the eroded soil volume by the age of the oldest datable object. Considering all compounds and landing sites in the study area, the average soil loss rate in compounds amounts to 107 Mg ha-1 year-1 (per unit compound) and in landing sites to 207 Mg ha-1 year-1 (per unit landing site). The soil loss from footpaths and unpaved roads is calculated by multiplying the total length of footpaths and unpaved roads with the average width and soil loss depth. The mean soil loss rate on footpaths is 34 Mg ha-1 year-1 and on unpaved roads equals 35 Mg ha-1 year-1. Compounds, landing sites, footpaths and unpaved roads occupy a small fraction of the study area (2.2 %), but contribute disproportionately to the total soil loss (i.e. 85 %) in the study area. It is concluded that compounds, landing sites, footpaths and unpaved roads are very significant sources of sediment pollution to Lake Victoria. This needs to be considered when designing strategies to reduce sediment production in the area.

(28)

Soil loss due to cassava and sweet potato harvesting around Lake Victoria, Uganda

Jolijn Leen, Moses Isabirye, J. Deckers, J. Poesen, M. Magunda Abstract

Soil loss due to crop harvesting (SLCH) has been established as an important soil erosion process that has significantly contributed to soil degradation in highly mechanised agriculture. Preliminary investigations into soil loss due to cassava roots and sweet potato as a case study from low input traditional agriculture in Uganda has shown that soil loss was negligible for sweet potato but considerable for cassava (3.4 t ha−1

yr). With this study we aim to come to a more comprehensive understanding of SLCH in Uganda. This study was conducted in Eastern Uganda with the following objectives: () To assess the magnitude of SLCH for cassava and sweet potato under low input agriculture and the amount of nutrients lost due to SLCH, (2) to investigate the factors that determine the magnitude of SLCH, by doing further research under a broader variation of soil texture types and soil moisture conditions and investigate other possible factors as well, (3) to look at possible differences in SLCH between small-scale farmers and commercial farmers, and (4) to investigate if the soil lost along the road or at markets contributes to the eutrophication and siltation of Lake Victoria. As commercial farmers transport sweet potatoes and cassava from the field to the market, possible losses along the route were distinguished. During heavy rain storms, the soil lost along the road and in markets is washed away down the road into the swamp that finally drains into Lake Victoria. Samples were taken at markets and in fields. Soil sticking to the roots was washed and the soil suspension was oven dried to estimate the amount of soil lost after harvesting.Mean annual soil loss was negligible for sweet potato (0.8 t hayr) but considerable for cassava (3.4 t hayr). Clay content and gravimetric soil moisture content (GMC) appeared to be the most important factor controlling SLCHspec (the soil loss value per unit of crop mass) in this study. SLCHspec was larger for commercial farms than for small-scale farms. This could possibly be due to a lower sand content for the samples taken at commercial farms.Soil lost along the road was 2.5 t ha yr for cassava and 0.8 t ha yr for sweet potato. The estimated amount of nutrients gathering the lake through SLCH loss along the road ranges from 1.1 to 3.5 kg N ha yr and 0.02 to 0.06 kg P ha yr. From this study we can

(29)

Termite mound removal in western Uganda as a land degradation process H. Erensa*, J. Wanyamabc, B. Mujinyaa, M. Isabiryeb, J. Poesenc, J. Deligned, E. Van

Ransta, P. Boeckxe, J. Deckersc.

a Laboratory of Soil Science, Department of Geology and Soil Science (WE13), Faculty of Sciences, Ghent University, Krijgslaan 281/S8, B-9000 Gent, Belgium (*

Corresponding author, e-mail: erensh@gmail.com) b Busitema University, PO BOX 236, Tororo, Uganda

c Department of Earth and Environmental Sciences, Katholieke Universiteit Leuven , Celestijnenlaan 200E, B-3001 Leuven, Belgium

d Laboratoire de Biologie Animale et Cellulaire, CP160/11, Université Libre de Bruxelles, 50 Avenue F.D. Roosevelt, B-1050, Bruxelles, Belgium

e Department of Applied Analytical and Physical Chemistry, Faculty of Agricultural and Applied Biological Sciences, Ghent University, Coupure 653, B-9000 Gent,

Belgium

f National Agricultural Laboratories, Kawanda, P.O. Box 7065, Kampala Abstract

Fungus-growing termites (Isoptera, Macrotermitinae) are often referred to as keystone species or ecosystem engineers because of their large pedological and ecological impact. Despite this importance, termites are still commonly perceived as pests because they consume agronomic and forestry products. In pastoral agroecosystems of semi-arid savannas, Macrotermitinae form a very obvious competitor for space and nutrients. This is the case in western Uganda, where land-use intensity is high, and livestock keepers are prone to remove termite mounds from their pastures. To understand this pattern, local livestock keepers were probed for their knowledge and perception of termites. The results show they are only partly aware of the role these insects play in maintaining the fertility of their pastures. They did however knew of many ways to use termite mounds to their advantage. Despite these uses to the community, most livestock keepers would rid their land of mounds if they had the means. The consequences of termite mound removal can only be estimated, as no long term experiments exist. From the ecological impact of Macrotermitinae documented in literature, the following scenario is deemed probable: Initially, spreading the nutrient-rich mound soil will provide a fertility increase, while more grass and space is available to livestock. In the long run however, reduced macroporosity will hamper infiltration and increase erosion. As no more clay and nutrient-rich sub-soil is recycled, overall fertility will ultimately decline, together with the habitat heterogeneity created by the mounds. The final result can be seen as a decline in the productive capacity of the land, which meets the definition of land degradation.

(30)

Tree Species composition and population structure among Smallholder farms in the Lake Victoria Catchments, Uganda

B. Isabirye*, N. Wajja-Musukwe3, S. Tabuti, V. Muwanika, D. Kimaro2, M. Isabirye3 1 Makerere University Institute of Environment and Natural Resources, P.O. Box 7298,

Kampala

2 Sokoine University of Agriculture, P. O. Box 3003, Morogoro, Tanzania 3 Busitema University, P.O. Box 236 Tororo, Uganda

*Corresponding Author. e-mail: brianisabirye@hotmail.com Abstract

Agriculture is often seen as the villain with respect to biodiversity and it has been argued that modern agriculture often homogenizes landscapes by relying on a few crops. The extent to which smallholder farms have impacted on tree species composition was documented in the Mayuge Lake Victoria catchments. The ecological status of tree species among smallholder farms in the Lake Victoria catchments was also investigated. Thirty smallholder farms were randomly selected in the Mayuge catchments and on-farm tree inventories taken. Fifty six tree species in an area of 51 hectares (30 farms) were recorded. The average farm size was .7 hectares and the average number of species per farm was 11 (Shannon-Weaver diversity indices of 2.7). Species on farm were evenly distributed, with a mean evenness of 0.18. On average, forty trees per farm were recorded. Most of these species are indigenous to Uganda. Moraceae and Markhamia lutea dominated other families and species respectively. Exotic trees were ecologically more important than indigenous species. Homesteads were more diverse (Shannon-Weaver diversity indices of 2.57) than gardens (Shannon-Weaver diversity indices of 2.25), with fruit and multipurpose trees dominating in both cases. The curve for the diameter at breast height shows a general reverse-J shaped distribution, characteristic of species with good rejuvenation and continuous replacement of themselves.

Keywords: Tree Species Composition, Population Structure, Smallholder farms, Lake Victoria catchments

(31)

Effectiveness of Selected Vegetation Buffer Strips as Sediment Filters on Sheet and Rill Runoff along Lake Victoria Shoreline1

D.N. Kimaro, M. Isabirye2, O. Semalulu2, E. Masanja, F.C. Kahimba, J. Poesen3, and J. Deckers4

1 Makerere University Institute of Environment and Natural Resources, P.O. Box 7298, Kampala

2 Sokoine University of Agriculture, P. O. Box 3003, Morogoro, Tanzania 3 Busitema University, P.O. Box 236 Tororo, Uganda

*Corresponding Author. e-mail: brianisabirye@hotmail.com Abstract

Many studies have shown that pollution in terms of sediment is a major problem in the Lake Victoria basin. Alteration of the natural transition zones namely riparian zones around Lake Victoria has rendered the protective nature of these areas ineffective or even detrimental to the health of the lake waters. Management and restoration of vegetative riparian buffer zones around the Lake can minimise sediment and nutrient delivery from intensively cultivated areas. However, lack of quantitative data on the appropriate vegetation cover types and buffer zone strip width that can be effective in reducing sediment delivery into the Lake Victoria and other similar lakes in East Africa is a major challenge facing policy makers and users of the basin. Therefore, a research aimed to assess the effectiveness of selected vegetation cover types and their corresponding vegetation strip widths that can be used in filtering sediment delivery from agricultural lands and for establishment of buffer zone around the Lake Victoria shoreline was conducted in Magu and Mayuge Districts in Tanzania and Uganda respectively. In both Distircts, Magu, Tanzania and Mayuge, Uganda, sediment laden runoff plots measuring 2 m by 20, 15, 12.5 and 10 m were established to determine the effectiveness of the selected vegetative buffer strip filters and strip filter widths set at 10, 5 and 2.5 m against a standard width of 10 m which was planted with maize (Zea mays). The vegetative buffer strip filters evaluated include elephant grass (Pennisetum sp), and Lemon grass (Cymbopogon citratus) Variables collected over a one year period include: daily sediment for the rainy days, daily rainfall, infiltration rates, plant vigour of the vegetative buffer strip filters (plant height (cm), and percent vegetation cover of the vegetative buffer strip filters. Data was analysed statistically using Excel, SAS and SPSS statistical packages. The results demonstrate that mass of sediment delivery decreases exponentially with increasing vegetative filter widths for all tested vegetation types both in Magu and Mayuge Districts with correlation coefficient (R2) ranging from = 0.7 to more than 0.9. The trapping efficiency of the tested vegetative filters increases logarithmically with increasing vegetative filter widths. Sediment trapping efficiency increased from 24 % at 2.5 m to over 80 % at 10 m vegetative filter widths for all tested vegetation types. The study show that the amount of sediment trapped by Vegetative Buffer Strip Filters and their corresponding widths are

(32)

of VBSFs to trap sediment from agricultural fields is a function of vegetation and site characteristics. Also, the results demonstrate that Vegetative Buffer Strip Filters (VBSFs) like the lemon, and elephant grass can be effective filters in removing sediment inputs to surface waters of Lake Victoria by restricting a minimum land area not exceeding 10 m under the tested VBSFs. The tested VBSFs have the potential to purify water from sediment that has been transported into the riparian zone from the agricultural lands. Areas of further research are recommended.

(33)

Relationship between Socio-Economic Characteristics and on-Farm Tree Species Conservation: A Case of Lake Victoria Catchments B. Isabirye*, Wajja Musukwe, V. Muwanika, D. Kimaro2, M. Isabirye3 1Makerere University Institute of Environment and Natural Resources, P.O. Box 7298,

Kampala

2Sokoine University of Agriculture, P. O. Box 3003, Morogoro, Tanzania 3Busitema University, P.O. Box 236, Tororo, Uganda

*Corresponding author. Tel.: 256-41-345299/ 256-772-352739: fax: 256-41-345299: e-mail: brianisabirye@hotmail.com

Abstract

Inadequate information on the relationship between socio-economics and on-farm conservation of tree species hinders the successful formulation and implementation of policies to promote tree diversity among traditional agricultural systems. This study investigated the relationship between selected farm characteristics and on-farm tree composition. Structured interviews were conducted in two riparian villages in the Lake basin, comprising of 60 respondents, while an inventory of tree species was done to estimate on-farm tree species diversity. The results in the survey indicate that socio-economic factors have various implications on on-farm tree diversity and local community livelihood. Factors such as farm size per household, age, education level, gender, family size, livestock, duration under current head, farm labor, farm spatial distribution of household, food security, market forces, off-farm opportunities, land tenure system, play a leading role in agro diversity conservation. The most significant explanatory social factor for tree conservation was age of head. Farms headed by ageing respondents (>40) were significantly more diverse than those headed by young ones (<40).The regression model for the dependence of tree density on social economic factors (independent) was significant (F = 2.061, p< 0.088). That for the Species richness was highly significant (F = 2.757, p< 0.03). The model for tree abundance explained about 44% (p< 0.088) of the total deviance. There was a strong correlation between farm size and abundance of trees, which was also correlated with tree species diversity.

Figure

Updating...

References

Updating...

Related subjects :