2008 ). Nitrogen fertilizer use in semi-arid southern Zimbabwe showed signiﬁcant maizeyield gains following the application of 10 kg N ha 21 on smallholder farms (Twomlow, Urolov, et al., 2008 ). Studies by Ncube, Dimes, et al. ( 2007 ) revealed signiﬁcant maizeyield gains through combining 3 – 6 t ha 21 of cattle manure with 10 kg N ha 21 . Maizeyield responses to N fertilizer were small in the wet 2005/2006 season and this can be attributed to the smaller quan- tity of 10 kg N ha 21 applied in a growing season that received above average and well-distributed rainfall. Some of the applied N could have been lost through leaching during a growing season with above average rainfall. Mapfumo and Giller ( 2001 ) report that leaching is a common pathway of N loss on light textured soils. In the 2005/2006 season, poor maize response to favour- able soilwaterconditions could have been caused by the inherent low fertility of the soils at all experimental sites. Soils at all experimental sites were acidic and below the recommended low- ermost pH level for maize growth. Maize grows well at soil pH of 5.5 – 7.8 and values below this range can cause nutrient deﬁciencies (Laﬁtte, 1994 ). There could have been deﬁciencies of other nutrients in addition to N and this reduced grain production despite the favourable soil moisture conditions in the 2005/2006 season. However, the importance of N in improving maize yields was conﬁrmed by the linear and quadratic relationships recorded in 2006/2007 and 2007/2008 seasons. Nitrogen increases grain production until a peak is reached and other factors become lim- iting, and this was illustrated by the quadratic relationship in the 2007/2008 season.
More frequent irrigation with smaller amounts of water, similar to the scheduling with drip irrigation in this thesis, has been suggested as a strategy to reduce deep percolation in coarse-textured soils (Linderman et al., 1976). However, the results in the present thesis indicate that this strategy may only be suitable during cold-dry cropping periods, i.e. underconditions with a reduced number of excess rainfall events. Moreover, concerns have been raised that drip irrigation cannot completely eliminate deep percolation and potential leaching of N below the root zone (Sui et al., 2015; Vázquez et al., 2006). Thus, recent research on strategies for irrigation in arid and semi-arid areas have focused on deficit irrigation as a way of obtaining significant water savings with a relatively small reduction in crop yield (Gheysari et al., 2017), while increasing water use efficiency. In the present thesis, such an outcome was significant in the hot-wet cropping period, when the use of reduced irrigation level in comparison to full irrigation resulted in a reduction in deep percolation of 22% and 37% for furrow and drip irrigation, respectively (Paper I). In the cold-dry cropping period, however, the influence of reduced irrigation level on deep percolation was estimated to be minor, as a result of small estimated values.
at higher mulch levels during the relatively wet 2005/06 growing season at Matopos (Figure 2). In the 2007/08 season the model predicted an increase in biomass yield with higher mulch cover at Matopos (Figure 2). The model is probably indicating soilwater benefits derived from mulching in 2007/08 season that was characterized by an abrupt end of rain in January 2008. The model is indicating that higher mulch cover conserve soilwater allowing the maize crop to reach maturity. However, observed maizeyield data did not show any significant influence of mulch cover on either the total biomass or grain yields in the 2007/08 season. The lack of yield response to mulching in the 2007/08 season could be attributed to the fact that some experimental plots were waterlogged between the end of December 2007 and mid-January 2008. This was observed at higher mulch levels (>2 t·ha –1 ) particularly in the planting basin and
Il ressort des différents résultats que les agrégats de surface issus des trois techniques culturales résistent mal lorsqu’ils sont soumis à une humectation rapide (éclatement). Les valeurs de DMP (0.37 à 0,41mm) présentées par ce test destructeur sont les petits comparativement aux autres tests (Fig. 4). Les résultats de ce test indiquent qu’il faut plus de temps dans les conditionssemi-arides du Maroc pour que le sol sous SD accumule suffisamment de MO afin qu’il puisse résister au phénomène de l’éclatement -.
Water stress is a major constraint to maize production in semi-arid Kenya. A field study was conducted at two sites in semi-arid Kenya to evaluate a new commercial product containing a mixture of Trichoderma harzianum Rifaistrains (TH-S) on enhancement of maizeyieldunder drought conditions. Seed of an early maturing maize composite KDV1 was dressed with T. harzianum strains and planted under controlled irrigation conditions. A commercial strain of T. harzianum referred as EzySeed® was used for comparison as the industrial standard. The EzySeed® treatment had signficant higher numberof plants at harvest followed by the T.harzianum strains (TH-S) treatment. EzySeed out performed both TH-S and control on yield at the two test sites. The untreated control had the least number of plants. Maize treated with T.harzianum strains and EzySeed® had enhanced yield and root growth parameters in comparison to control indicating that an opportunity exists for further development of T. harzianum strains for management of drought stress on maize in semi-arid regions.
In 2014, regardless of the method of soil cultivation and plant fertilization, more N 2 O was emitted from the soil in Żelazna, Baborówko and Czesławice on the second test date than on the other dates (Figure 2). In Grabów, in the conventional cultivation and fer- tilization system, N 2 O-N emission from the soil was the lowest in the second test dates. In the ploughless system with subsurface application of fertilizers, the emission of this gas on the second test date was higher than on the first and third test date. In 2015, in Żelazna and Baborówko, an increase in N 2 O emission from the soil was observed between the first and the second test date, and a decrease on the third test date. In Czesławice, the emissions on the first and second test date were at a similar level and decreased on the third test date. In Grabów, however, the N 2 O emission from the soil in the field under conventional cultivation and fertiliza- tion was the lowest on the second test date. On the same date, the observed N 2 O emission from the soilunderreducedtillage was the highest.
In semi-arid areas, increasing CO 2 emissions are threatening agricultural sustainability. It is unclear whether differ- ent tillage practices without residue returned could help alleviate these issues while increasing crop productivity. This study aimed to quantify soil respiration under conventional tillage (CT); rotary tillage (RT); subsoiling (SS) and no-till (NT), all without residue returned in the Western Loess Plateau. The results showed that SS and NT significantly decreased soil respiration compared to CT, but the effects of SS was the greatest. As a result, SS de- creased carbon emission by 22% in 2014 and 19% in 2015 versus CT. The trends of net ecosystem production under different tillage systems were as follows: CT > RT > NT > SS. No-till increased net ecosystem production by 33% in 2014 and 12% in 2015 relative to CT. The SS treatment increased average grain yield by 27% and 23% over CT and RT, and enhanced water use efficiency by an average of 43%. On average, SS increased carbon emission efficiency by 60% and 43% compared to CT and RT, respectively. Thus, subsoiling management strategy is a promising option for the development of sustainable agriculture in semi-arid areas.
Despite of adoption of hybrid maize cultivation to a considerable level, maize yields in Pakistan are lower than other countries in the region. With others, maize cultivation under low soil fertility and without supplemental nitrogenous inputs is an important reason for low yields. This derives national maize breeding programs to develop low-nitrogen responsive maize cultivars. In this context, exotic maize open-pollinated varieties were introduced from CIMMYT for adaptability testing and subsequent adaptation. The trial including these OPVs was planted under zero nitrogen application. Correlation and path coefficient analysis was used to establish association of grain yield with its components to ascertain specific selection criteria which will be used to enhance efficiency of the future maize breeding and yield improvement programs using this germplasm. The results complemented with heritability estimates revealed that 100- kernel weight and shelling percentage together with kernel rows per cob can be utilized effectively for yield enhancement undernitrogen deficient conditions.
June to July and February to March are the two growing seasons of okra. The total water requirement for okra in whole growing season is 500 mm  . For enhancing the germination of okra yield, the seeds were soaked for 6-8 h in water before sowing. After the soaking period, the seeds were sown manually on both sides of ridges with a plant x plant spacing of 25 cm. The sowing date of the okra was 8 th May, 2014. All agronomic practices were kept normal and uniform for both treatments. Okra requires a long and warm climate and is susceptible to frost. The seed usually does not germinate when the temperature is below 20º C. The plants started emerging after 3-4 d and were apparently visible after one week.
The effects of three tillage systems: no-tillage (NT), reducedtillage (RT) and conventional tillage (CT), and three levels of fertilization (0, 258 and 516 kg/ha NPK (58:18:24)), on the maizeyield during ten years (1999–2008) were analyzed on the chernozem soil type in Zemun Polje, Serbia. Statistical analyses showed significant effects of all three factors i.e., year, soiltillage and amount of fertilizers, and their interactions on the maizeyield. The ten-year averages showed that the highest yields were observed with CT (10.61 t/ha), while the averages with RT and NT were lower (8.99 t/ha and 6.85 t/ha, respectively). The results of the influence of the amount of the applied fertil- izers on maizeyield showed that the lowest yield was in the zero level of fertilization 7.71 t/ha, while the yield was raised when the 258 kg/ha and 516 kg/ha NPK were applied (9.18 t/ha and 9.56 t/ha, respectively). Analyzing the influence of the soiltillage systems on maize production with respect to the amounts of applied fertilizers, this research revealed the benefits of CT under the presented agroecological conditions, irrespective of the level of ap- plied fertilizer.
obtain grain yield over 3.8 tha . Soon et al. (2001) reported that N uptake by wheat increased with deep tillage than conventional tillage when following a legume crop. Abu-Kreshe et al. (1996) reporting similar results stated that alternate use of deep tillage in legume based cropping system increases the plant nutrient uptake and grain yield of sorghum. Jin et al. (1996) investigated the effect of cattle manure application on yield of maize and soil characteristics. It was observed that cattle manure application resulted in higher maizeyield than chemical fertilizer. Suri and Sarita (1996) concluded that addition of FYM reduces the requirement of NPK fertilizer. They reported that FYM lowered NPK fertilizer requirement for maize by 60,
Maize (Zea mays L.) is a very important forage source for livestock nutrition and the third most cultivated forage crop after alfalfa . Recently, China’s corn production is one of the world’s largest, driven mainly by growth in animal feed consumption, while consumption of staple grains is growing at a more moderate rate . Livestock is an important livelihood strategy in most countries  providing food and industrial products. Despite their importance, livestock are usually undernourished due to lack of feeds of sufficient quality and quantity; the consequences of which are low production, increased disease susceptibility, higher mortality rates and reduced fertility. This is typical of smallholder livestock production systems on the Loess plateau where livestock are kept by traditional farmers. Improvement in the management of crop−livestock systems is important for the livelihoods of small scale farmers  especially with the increases in demand for livestock products and the associated favorable prices . Many management systems, including N fertilization and plant density influence the yield and quality of forage maize . Nitrogen fertilization is one of the major strategies to increase production for the increasing worldwide demand for food . Nitrogen is the most deficient nutrient in forage crops and improving the nitrogen content in the soil is an important factor for growing quality forages. Adequate supply of plant available nitrogen will ensure higher photosynthetic activity and vigorous vegetative growth. The used of nitrogen fertilizer therefore, plays an important role in the establishment of viable feed sources . Iqbal et al.  reported a significant effect on forage quality, when nitrogen was applied either
one plot to the next when tillage was undertaken. At Mat- opos research site a new block was established for the experiment in 2005/06 as cowpea was planted on the 2004/05 block as part of a rotation, which is not the focus of this paper. Cowpea results will not be reported in this paper. Unfortunately, due to logistical problems it was not possible to establish a new block at Lucydale in 2005/06. Residues at the location were not enough to make fresh applications. As a consequence in 2005/06 we looked at the residual impacts of the previous season’s mulch lev- els. Digging of planting basins and ripping were carried out after applying mulch cover. Planting basins were dug at 0.6 m · 0.9 m spacing using a hand hoe and each basin measured 0.15 m (length) · 0.15 m (width) · 0.15 m (depth). Rip lines were opened at 0.9 m inter-row spacing using a ripper tine attached to the beam of a donkey-drawn mouldboard plough. The ripping depth achieved on both soils varied between 0.15 and 0.18 m. Cattle manure was applied in October each year at a rate of 3 t ha 1 in all plots under the three tillage treatments as basal soil fertility amendment. Manure was placed in the planting basins, dribbled along the ripline and broadcast under hand-dug planting basins, ripping and conventional tillage treat- ments, respectively. Conventional ploughing was done soon after the ﬁrst eﬀective rain (20–30 mm) in December each year using a donkey-drawn VS10 mouldboard plough. Planting furrows were then opened at inter-row spacing of 0.9 m. During the ploughing process most of the crop res- idue was incorporated into the soil.
However; this study agree with that of  who reported that LAI of maize was significantly affected and increased in linear fashion with increase plant population. Other workers found results which disagree this finding.  reported maximum LAI from the lowest plant density and minimum LAI from the highest plant density. In this case, increase in number of plants per unit area beyond optimum level could probably reduce the amount of light availability to the individual plant, especially, to lower leaves due to shading. Generally, consistent increments in LAI were observed with increased plant population density. This dramatic increase in LAI with reduced intra row spacing or with increase in the plant population density might be due to occupation of more unit area by green canopy of the plants.
Five plants were selected at random from each plot and their height was measured from ground surface to top with the help of a meter rod and the average height was calculated. Five randomly selected plants from each plot were tagged and stem diameter from the base, middle and top was measured with Vernier caliper and then average was calculated. Five representative cobs from each plot were taken; cob length was calculated and averaged. Numbers of grains per cob were counted from five randomly selected cobs from each treatment and then average was calculated. Thousand grains were taken from seed lot of each plot and then weight was recorded in grams by using automatic electric balance. After harvesting and threshing, the clean maize grains were air-dried, bulked and weighed to record the grain yield. The grain weight was adjusted to 14% moisture contents and expressed in t ha -1 . The crop
The use of cover crops influenced the amounts of ammonium (p<0.01) but did not impact the levels of available N and nitrate in the 0.00-0.10 m layer. Similarly, there was no effect of the topdressing-N and fertilization × cover crop interaction (Table 2). As soil collection was carried out at the end of the crop cycle (maturation stage of corn), most mineral N had possibly been absorbed by the crop or leached into the deeper layers of the soil profile, especially nitrate that is more mobile in soil. The ammonium content in the soil in this layer (0.00-0.10 m) cultivated with U. ruziziensis was 3.4 to 4.2 times higher than in the soil where other cover crops were planted (Table 2), indicating a high rate of nitrogen mineralization of its residues. Our data showed that U. ruziziensis has higher concentrations of compounds with high mineralization rates, which might provide more available nutrients for plants. In the 0.10-0.20 m layer, there was an effect of the cover crops and topdressing-N for available-N (p<0.01). Moreover, there was also interaction between topdressing-N and the cover crops on the nitrate ammonium levels in the soil (Table 3).
Globally, a range of agronomic factors have been reported to have an impact on the performance of conservation agriculture (CA) and often determine its performance in relation to conventional agriculture (CONV). To assess this performance in Zimbabwe, 48 CA experiments were conducted by the International Crops Research Institute for the Semi-Arid Tropics in the semi-arid areas of southern Zimbabwe from 2004 to 2010, to calculate the weighted mean difference (WMD) through meta-analytical methods. The two CA practices, planting basins (Basins) and ripper tillage (Ripper), were compared with CONV. It was hypothesised that CA results improved yield compared with CONV and that the effect of CA practices on yield is affected by soil type, rainfall amount and distribution and selected management practices, which included rates of inorganic fertilisers and manures and mulching. Basins were superior to CONV in 59% of the experiments and the overall effect was significant (p < 0.001). The effect of Ripper was non-significant. The hypothesis that CA practices result in improved maize grain yield over CONV was accepted for Basins. The WMD for experiments conducted on sandy soils was 0.365 t ha −1 for Basins and 0.184 t ha −1 for Ripper, and in both cases was significant (p < 0.05). For clay soils, only the WMD for Basins was significant. A higher rainfall regime (500–830 mm) resulted in a lower WMD for Basins (0.095 t ha −1 ) and Ripper (0.105 t ha −1 ) compared with 0.151 t ha −1 for Basins and 0.110 t ha −1 for Ripper under lower rainfall (320–500 mm). The overall effect of Basins under the higher rainfall regime was not significant. There was better yield performance for Basins when the rainfall was well distributed; the reverse was noted for the Ripper. The application of 10–30 kg ha −1 of N (micro-dose range) resulted in a higher WMD for Basins than zero N application. Without N application, the WMD of Basins was not significant. For zero manure application in Basins, the WMD was 0.043 t ha −1 compared with 0.159 t ha −1 when manure was applied. The application of mulch depressed the WMD in Basins by 44% and Ripper by 89%. The hypothesis that yield performance under CA is influenced by soil type, rainfall amount and distribution, inorganic fertiliser and manure application was accepted.
Rectangular shaped planting basins with a length of about 30 - 35 cm and width of about 10 - 12 cm (based on the width of the hoes that were used during land preparation) were prepared using hand hoesto a depth of about 20 - 25 cm. This depth was used to help break any compacted soil layers below the surface. The basins were made in rows spaced at 70 cm (0.7 m) between rows and 50 cm (0.5 m) between basins in each row giving a total of 1143 planting basins in a 20 m × 20 m. Under zero-tillage, no soil disturbance was done during plant- ing. The seeds were drilled directly into the soil using machetes or pangas. In the plots under conventional til- lage, the crop residue from the previous season was gathered and burned. The plots were then ploughed. In plots with planting basins and zero tillage, crop residue and coppiced legume tree biomass were returned on the ground as mulch. Ridges were constructed using hand hoes by splitting the ridges from the previous season. This is because farmers have always used ridges in their field from one season to another for improved soil moisture retention and erosion control, especially where ridge height was well maintained. Plant residue and coppiced tree biomass were incorporated under the new ridge.
Microbial biodiversity was found to be greater under RT than TT (Table 4). In soil samples from both treatments a total 197 taxa of diatoms were identified. RT was richer in species (139 taxa) than TT (102 taxa) and this diffe- rence suggests that some taxa are more sensitive to tillage than others. Two main factors may have contributed to this difference. Firstly, there is the effect of soil mixing dur- ing tillage. The surface layer, where the diatoms live, was mixed with 25 cm of soil in TT but only with 10 cm of soil in RT. Secondly, the soil surface layer in RT had greater SOC content as shown in Table 3 and as found by Stanek- Tarkowska et al. (2015). Greater SOC content also leads to improved soil physical properties. Table 4 enables the dia- tom communities under RT and TT to be compared. In the very dry years (2015 and 2016) under RT, dominant species exceeded 20%, but under TT were less than 20% (Table 4). Comparable results were obtained by Stanek-Tarkowska and Noga (2012a,b) in RT and TT systems undermaize in a field experiment in Dąbrowa (voivodship Podkarpackie, Poland) on a silty soil. They observed greater biodiversity of diatoms (62 taxa) under RT than under TT (38 taxa) in a silty soil. The soil algae, including diatoms, produce ami- no acids, organic acids, polysaccharides and vitamins. Their biomass is a source of humus and nitrogen compounds.