A b s t r a c t. The purpose of the present study was to provide information about the effect exerted by fonofos pesticide on dehydrogenaseactivity of Mollic Gleysol, Eutric Fluvisol and Eutric Histosol soil samples. The effect of fonofos on dehydro- genase activity was evaluated taking into consideration the pesticide dose and soil incubation time. It was found that soildehydrogenaseactivity showed an inhibitory effect with increase of the pesticide doses. Dose on the level of 1µg g -1 of pesticide caused 5-21% inhibition of enzymatic activity, whilst ten times higher doses resulted in 17-44% drop of activity in comparison to the control. Increase of dehydrogenaseactivity was also connected with fall of redox potential (Eh). The results suggest a negative effect of fonofos on soildehydrogenaseactivity in the first stage after application.
0.20-0.40 cm layers of HC soil columns, were a consequen- ce of low rate of gas exchange with atmosphere caused by lower soil porosity (La Scala et al., 2009).
The root length distribution with depth at the 30th day of wheat growth is presented in Fig. 2. The differences between objects are the result of different soil compaction which reduces root growth rate by increased soil impedance to root growth. Impedance to root growth may be related to soil pe- netration resistance by steel cone, measurements of penetra- tion resistance are presented in Table 2. Penetration resis- tance of soil layers with density equal to 1.3 and 1.5 Mg m -3 were below value of 3 MPa usually assumed as a value abo- ve which root growth is impeded (Hakansson and Lipiec, 2000). 20-40 cm layers of HC soil column had penetration resistance above 3MPa, restricting root growth, what was re- flected in shorter roots within these layers.
Arbuscular mycorrhizal fungi (AMF) colonise roots of most plants; their extra-radical mycelium (ERM) extends into the soil and acquires nutrients for the plant. The ERM coexists with soil microbial communities and it is unresolved whether these communities stimulate or suppress the ERM activity. This work studied the prevalence of suppressed ERM activity and identi ﬁed main components behind the suppression. ERM activity was determined by quantifying ERM-mediated P uptake from radioisotope-labelled unsterile soil into plants, and compared to soil physicochemical characteristics and soil microbiome composition. ERM activity varied considerably and was greatly suppressed in 4 of 21 soils. Suppression was mitigated by soil pasteurisation and had a dominating biotic component. AMF-suppressive soils had high abundances of Acidobacteria, and other bacterial taxa being putative fungal antagonists. Suppression was also associated with low soil pH, but this effect was likely indirect, as the relative abundance of, e.g., Acidobacteria decreased after liming. Suppression could not be transferred by adding small amounts of suppressive soil to conducive soil, and thus appeared to involve the common action of several taxa. The presence of AMF antagonists resembles the phenomenon of disease-suppressive soils and implies that ecosystem services of AMF will depend strongly on the speci ﬁc soil microbiome.
* Author for correspondence (Email: firstname.lastname@example.org) Published online: 8 July 2009
Abstract: Mycorrhizalcolonisation of Douglas-fir and Corsican pine seedlings in soil from kānuka and mānuka dominated shrublands in Canterbury was studied using a bait plant technique. Soil cores were collected from 10 sites of each shrubland, transferred to a glasshouse, and sown with seed of both tree species. Mycorrhizalcolonisation was examined after 19 weeks’ growth. Overall, seedlings of Douglas-fir were larger than those of Corsican pine, but the amount of Corsican pine seedlings that were colonised (56%) was about twice that of Douglas-fir (29%). Across the sites, 7–61% of Douglas-fir and 16–81% of Corsican pine seedlings had mycorrhizas. Colonisation of the two tree species was correlated in soil cores from kānuka stands, but not from mānuka stands. Colonisation was significantly greater in kānuka than mānuka stands in Douglas-fir, but not in Corsican pine. Kānuka stands were of a lower overall elevation than mānuka stands and had higher levels of soil available phosphorus. Both factors may have contributed to the greater mycorrhizalcolonisation of Douglas-fir in kānuka stands. Differences in colonisation between sites could be partially explained by the proximity of sources of spores of mycorrhizal fungi. It is concluded that low numbers of mycorrhizal propagules may constrain mycorrhizal formation in environments distant from a spore source, but are ultimately unlikely to preclude it, or limit successful seedling establishment.
A b s t r a c t. The paper presents the influence of chromium forms (III) and (VI) on the soildehydrogenaseactivity. Enzyme activities can be considered effective indicators of soil quality changes resulting from environmental stress or management practices. It was found that chromium compounds have detrimental effects on soildehydrogenaseactivity. After the addition of chromium, a rapid and significant decrease in enzymatic activities was observed.
Several, mutually non-exclusive hypotheses have been proposed to explain the success of invasive plants in their new range (reviewed by Hierro et al. 2005, Mitchell et al. 2006): the enemy release hypothesis (Keane and Crawley 2002), the novel weapons hypothesis (Callaway and Ridenour 2004, Callaway et al. 2008, Wolfe et al. 2008), the evolution of increased competitive ability (EICA, Blossey and Nötzold 1995, Bossdorf et al. 2005), the theory of fluctuating resource availability (Davis et al. 2000), the framework of vacant niches (Moles et al. 2008), and the facilitation of further invaders as described in the invasional meltdown hypothesis (Simberloff and Von Holle 1999). More recently, attention has turned towards the soil biota as a possible mediator of plant-plant interactions in plant invasions (Klironomos 2002, Fitter 2005). Arbuscural mycorrhizal fungi (AMF) are particularly important in this respect due to their widespread occurrence and important role in communities and ecosystems (Brundrett 1991).
The toxic effect of pesticides on the cellulose decomposing bacteria probably appeared also in
2008 when their number in the soil of the CONFYM treatment was more than 2 times lower than that of the ORGFYM treatment. In 2009, the number of these bacteria, on the contrary, was significantly highest in the CONFYM treatment. It probably may be explained with the higher amounts of oat roots and straw residues because the grain yield from the CONFYM area (3.9 t/ha) was significantly higher than from the organic plots. The average results of four-year experiment showed that the application of cattle manure in the crop rotation significantly enhanced the abundance of cellulose decomposing bacteria whereas there were no differences between organic and conventional treatments.
In the perennial tree crop studies, nutrient regime had no impact on colonisation of tree roots by resident AMF species. Biochar applied as a soil amendment led to significantly increased AMF colonisation, while planting a combination of clover/grass in the tree row increased the presence of AMF arbuscules and vesicles. In the two cherry sites, mycorrhizalcolonisation was not affected by the nutrient regime. An interaction between nutrient regime and EM was observed, with EM application increasing colonisation in ‘Lapin’ cultivar roots when applied to alternative regime plots, but reducing colonisation in conventional plots. However the reverse occurred in the ‘Sweetheart’ cultivar roots. This difference between the two cultivars is most likely influenced by the different soil types in these two orchards. Properties of both apple and cherry fruit were influenced by AMF colonisation with a positive correlation between colonisation and both total soluble solids (TSS) and titratable acidity (TA) but a negative correlation with the ratio of TSS/TA. Soil nutrient levels were adequate in the alternative plots where humates were applied, and levels of some nutrients were higher in these plots than in the conventional plots. Hence it can be concluded that nutrient regimes based on application of humates, particularly in conjunction with biochar or EM inoculation have the ability to improve soil nutrient uptake, leaf nutrient levels and fruit properties in the presence of mycorrhizalactivity.
The objectives of the present study were the evaluation of the influence of the soil’s physical factors such as water status and bulk density on dehydrogenaseactivity and to determine the relationship between the enzyme activity and soil aeration parameters in a pot experiment with barley vegetation.
BENNEWITZ, E., GARRIDO, E., FREDES, C., GUTIERREZ, L., LOŠÁK, T.: Soil mineral concentrations and soil microbial activity in grapevine inoculated with arbuscular mycorrhizal (AM) fungus in Chile. Acta univ.
agric. et silvic. Mendel. Brun., 2008, LVI, No. 5, pp. 13–17
A two year-experiment was carried out to study an eﬀ ect of root inoculation with arbuscular mycor- rhizal (AM) fungus on soil mineral concentrations and soil microbial activity in grapevine (Vitis vi ni- fe ra) cv. “Cabernet Sauvignon” cultivated in Chile. Plants were inoculated with a commercial granu- lar inoculant (Mycosym Tri-ton ® ) and cultivated in 20 L plastic pots ﬁ lled with an unsterilized sandy clay soil from the Vertisols class under climatic conditions of Curicó (34°58´ S; 71°14´ W; 228 m ASL), Chile.
 Cavagnaro TR, Smith FA, Smith SE, Jakobsen I. Functional diversity in arbuscular mycorrhizas: exploitation of soil patches with different phosphate enrichment differs among fungal species. Plant Cell Environ 2005;28:642-80.
 Barrett G, Campbell CD, Fitter AH, Hodge A. The arbuscular mycorrhizal fungus Glomus hoi can capture and transfer nitrogen from organic patches to its associated host plant at low temperature. Appl Soil Ecol 2011;48:102-5.
The study aimed at evaluating some soil physicochemical properties of soil on dehydrogenaseactivity in the soil of the area which was achieved by assessing some selected physicochemical properties of soil and dehydrogenase activities, and determine the relationship between some selected physicochemical properties of soil and dehydrogenase activities of soil in the area. One square kilometer of irrigated land was selected randomly and then divided in to 10 grids square and samples were collected in each grid using composite method and analyzed using standard laboratory procedures. The results shows that, clay recorded mean values of 3.8 cmol/kg ±0.84, EC 1385 dSm-1 ±760, pH 7.66±0.46, OC 1.37%±125, total nitrogen 0.15%±0.04, CEC 2.8 cmol/kg±0.06 and DHA 0.005±0.06. The findings shows that, there is no significant relationship between clay, EC, pH, Oc, nitrogen and dehydrogenase activities using correlation analyses at p ˂0.05 probability level, while the regression analyses show that the coefficient of determination (r2) values obtained are 0.05, 0.44, 0.001, 0.03, 0.006 and 0.09 for clay, EC, pH, Oc, TN and CEC respectively. From the findings it was concluded that Ec, pH, OC, N and CEC have no significant effect on DHA of the soil in the area. It is therefore recommended that appropriate soil management practice should be encourage more to enhance microbial activity in the soil of the area.
Thirty nodulated root samples of both clover species, each with 3–4 mature nodules, were used. Each nodulated root sam- ple was excised from lateral roots by carefully cutting with sharp scissors late in the afternoon, leaving a sufﬁcient length of root to avoid damage to nodules. The nodulated root sam- ples were washed in distilled water, dried, and placed in three separate gas-tight vials each containing 10% acetylene, whilst a third nodulated root sample was placed in a vial containing no acetylene to account for root ethylene production. In addition, control samples were taken, containing only roots without nodules in order to detect any non-nodule related acetylene-reduction activity by the roots. Vials containing only air and acetylene were also used to ensure the absence of ethylene in the acetylene gas. Samples were assayed after 24 h for ethylene by injection into a Hewlett–Packard gas chro- matograph with a Poropak R column (shimadzu, GC-148B, Japan). Ethylene production per hour was ﬁnally related to the dry weight of the root nodules. These observations were replicated three times in three weekly samplings. Nodule dry weight was determined after oven-drying for 24 h at 70 C.
negative effect of Bt plants on AMF. De Vaufleury et al. (2007) found no difference in mycorrhi- zal colonisation between Bt (MEB307 expressing Cry1Ab toxin) and non Bt maize lines. Verbruggen et al. (2012) tested two maize cultivars (Cry1Ab) for their effects on soil AM fungal communities and the main conclusion of the experiment was that no consistent difference was detected between AM fungal communities associated with GM and non-GM plants. These results are in contrast with our findings. However, it should be noted that the different and contradictory findings of the studies available may result from differences in the cry toxins and AMF species used, as well as in the circumstances of the experiments.
appressorium) is formed, marking the initiation of the symbiotic phase which terminates with the formation of arbuscules, where most of the nutrient exchange between the host plant and the AMF is thought to occur (Smith & Read, 2008; Wang et al., 2017). AMF are found associated with several key crop families (e.g. Gramineae, Palmae, Leguminosae and Rosaceae), including some tree species and many vegetable and ornamental plants (Prakash et al., 2015). AMF colonise the root cortex and produce extraradical hyphae that are specialised in the acquisition of mineral nutrients and increase the exchange surface between root and surrounding soil (Smith & Read, 2008). AMF associations are of high interest for agriculture and horticulture. In fact, AMF can support plants in increasing nutrient uptake, particularly of poorly mobile phosphate ions. AMF can also help plants in tolerating drought and metal toxicity, as well as pathogen and herbivore attacks both above- and below-ground (Smith et al., 2010; Prakash et al., 2015). More recently, AMF were shown to actively assist plant in nitrogen and zinc uptake (Hodge & Fitter, 2010; Prakash et al., 2015). In return, AMF obtain a carbon supply from their associated host plant. The importance of AMF in crop growth and development is becoming increasingly clear and AMF are now recognised as a vital component in agroecosystems. Traditionally, the role of AMF was believed to be one of nutrient provision only. However, it is now recognised that AMF contribute a wider range of benefits to their host plant as well as playing an important role in ecosystem services (Gianinazzi et al., 2010; Smith et al., 2010). One of these benefits is in priming, inducing or otherwise improving plant defences against attacks from pathogens and/or insects (Pozo et al., 2013).
K e y w o r d s: soil aeration status, dehydrogenaseactivity, triticale, redox potential, oxygen diffusion rate
Soil enzyme activity plays an important role in the maintenance of soil fertility [6,16]. Dehydrogenases are enzymes of respiration pathways of aerobic as well as of anaerobic microorganisms [4,23]. Soil management tech- niques influence microbial communities in soil and, indi- rectly, change the activity levels of many enzymes. The soil oxygenation status results from the equilibrium between the
In presence of glyphosate they found the drop of enzyme activity from 5 to 98%. The effect of glyphosate on the carbon dioxide concentration in soils headspace during incubation period is shown in Fig. 4a, b, and c. At the beginning of the experiment concentration of CO 2 varied from 0.11 to 0.96% and increased up to 12% at the end. In all cases in control samples an increase of CO 2 was gradual and reached the maximum between 35th and 42nd days of incu- bation. In Terric Histosols and Eutric Fluvisols, inversely than in Mollic Gleysols, in combination with addition of pesticide, the concentration of CO 2 was significantly lower than without it. The biggest differences were registered in Terric Histosols between 3rd and 21st day. Then CO 2 did not exceed 2%, whereas from 28th days reached up to 4%
soil aggregate stability through hyphal enmeshment of soil aggregates and the production of extracellular polymers (Rillig and Mummey, 2006).
Compared to topsoil, subsoil is subject to less disturbance that can disrupt hyphal networks, leading to a longer residence time of aggregate-protected OM (Lehmann et al., 2017). Therefore, stabilization of soil aggregates by mycorrhizal hyphae in the subsoil can contribute substantially to the protection and thus sequestration of soil organic matter (SOC). A better soil structure also improves soil pore connectivity, leading to increased interactions between soil microbes, and, consequently, likely increased competition for nutrients. If AM fungi could outcompete decomposers for nutrients, they would be able to indirectly reduce decomposition activity and thus potential loss of added or stabilized carbon.
Although the ecological and physiological aspects of arbuscular mycorrhizal fungal interactions with plants have been extensively researched, only a few studies have focused on the effect of AM fungi on the reproduction of a host plant. This includes flowers, seeds, and the survival of second generation plants in relation to the parental plant being colonised by AM fungi (Koide 2010). Preliminary experiments with the native wild plant Sonchus oleraceus (Chapter 3) showed that the association of S. oleraceus with mycorrhizas produced no enhancement of the growth of the parental plants and their offspring; yet, the morphological appearance of the second generation plants might point toward a beneficial impact of AM colonisation, possibly by favouring nutrient accumulation in S. oleraceus seeds and offspring, a suggestion that needs further investigation.
A b s t r a c t. Effects of sampling time, storage period, and three different methods of storage on dehydrogenaseactivity of the topsoil of Phaeozem and three Orthic Luvisols were studied. Analysis of seasonal variability showed statistically significant differences in the dehydro- genase activity between four seasons of the year in the Orthic Luvisol developed from silt. Differentiation among the activity of the soil samples taken in different seasons of the year is maintained for the 7 years of storage. The highest dehydrogenaseactivity of fresh soils was found in the Phaeozem where it was about four times higher than in the Orthic Luvisol developed from silt. That tendency was preserved in all the experiments irrespective the storage time and methods. Air-drying resulted in a considerable decrease of dehydrogenaseactivity after sample storage for a period from one to two months with a tendency to increase an increasing storage period exceeding about 20 months.