Influence des pratiques agricoles sur la macrofaune du sol : Cas de l’enfouissement de la paille et du fumier

La macrofaune du sol sur un essai agricole de longue durée a été inventoriée en 2008, huit semaines après les semis. Cet essai agricole implanté en 1980 est situé au Centre Ouest du Burkina Faso, et estreprésentatif de la production du sorgho avec utilisation de deux types de matières organiques exogènes avec ou sans fertilisation azotée. L’objectif était d’étudier l’influence de ces pratiques agricoles sur la macrofaunedes sols, représentée par les termites et les vers de terre. Les termites ont été échantillonnés par la méthode des monolithes et par transect ; les vers de terre ont été échantillonnés uniquement par monolithes. Sept espèces de termites de la famille des termitidae et trois espèces de vers de terre de la famille des Acanthodrilidae ont été identifiées. L’apport des matières organiques exogènes s’est traduit par une augmentation du nombre d’individus par unité de surface pour les deux groupes de macrofaune. L’incorporation de la paille a été beaucoup plus favorable aux termites par rapport au fumier qui a été plus favorable aux vers de terre. Pour les deux types de matières organiques, l’apport d’azote a entraîné une augmentation du nombre d’individus par unité de surface. La macrofaune dans la jachère bordant le site a été plus diversifiée que dans les sites de culture

Potential side effects of biocontrol and plant-growth promoting Bacillus amyloliquefaciens bacteria on earthworms

After 1-2 months, survival, growth and reproduction of the earthworms were recorded. We found no effect of the treatments as compared to control without BA amendments. We conclude that the use of high doses of BA with concentrations at the same magnitude as maximally expected when the bacteria are used as PGPR and BCA, is not harmful to the soil dwelling earthworms tested in this project. Further studies of the ecological effects of PGPR and BCA bacteria on other non-target soil organisms are encouraged. The development of sustainable agricultural systems, where ecosystem services are optimized, has to be aided by a deeper knowledge of the combined effect of bacteria and earthworms on the promotion of plant health. (C) 2015 Elsevier B.V. All rights reserved

Concentrations of potentially toxic elements and soil environmental quality evaluation of a typical Prosecco vineyard of the Veneto region (NE Italy)

Purpose The aim of this work was to assess the concentrations of potentially toxic elements and to evaluate the soil quality of a typical Prosecco Denomination of Controlled and Guaranteed Origin vineyard of the Veneto region, NE Italy. Materials and methods Soil samples and leaves of Taraxacum officinale and Vitis vinifera were collected during spring–summer 2014. Element determination (Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, V, and Zn) were performed with ICP-OES after microwave digestion of samples. Soil quality was assessed via the biological soil quality (BSQ-ar) index. Lipid peroxidation test was performed to evaluate the vegetation oxidative stress, based on malondialdehyde (MDA) content via spectrophotometer. Results and discussion High concentrations of Al,Mg, and P were identified in soil, while high contents of Al, Cu, Fe, and Zn were found in V. vinifera leaves. The high concentrations in soil are probably due to agricultural activities, whereas those in leaves are probably due to atmospheric deposition and repeated use of foliar sprays in viticulture. The bioconcentration factor showed an effective transport of Cu, P, and Zn, from soil to leaf. The BSQ-ar values registered were similar to those obtained in preserved soils; hence, the biological class (VI) of these soils is high. The MDA content in T. officinale and V. vinifera leaves was below the reference value for T. officinale (2.9 ± 0.2 μM), suggesting that the metal content did not stress the vegetation in the investigated site. Conclusions The MDA value for V. vinifera (1.1 ± 0.7 μM) could be adopted as another control value for soil quality, which in our case is of Bgood quality.^ Moreover, our results suggest that high concentrations of elements detected in the analyzed samples do not influence negatively the quality of soil, but a better agronomic management could improve soil quality in the studied area

DYNAMICS OF SOIL NEMATODES AND EARTHWORMS IN URBAN VEGETABLE IRRIGATED WITH WASTEWATER IN THE NAIROBI RIVER BASIN, KENYA

The effects of heavy metals lead (Pb), Cadmium (Cd) and Cromium (Cr) on nematode communities and earthworm density and biomass were studied in the wastewater irrigated farms of the Nairobi river basin. The levels of Cr and Pb in the wastewater were below the threshold values considered to be toxic while those of Cd exceeded the permissible limit. Heavy metal accumulation in soils in the Kibera and Maili Saba farms  were Cd (14.3 mg kg-1), Cr (9.7 mg kg-1) and Pb (1.7 mg kg-1) and 98.7 mg Cd kg-1, 4.0 mg Cr kg-1 and 74.3 mg Pb kg-1, respectively. High heavy metal concentrations as well as soil organic matter were negatively correlated with plant feeding nematodes in the genera Criconema, Meloidogyne, Paratylenchus, Pratylenchus and Scutellonema. Bacterial feeding nematodes genera Rhabditis, Plectus, Cephalobus and Acrobeles were predominant in the gardens treated with wastewater. An average density of 198 m-2 earthworms and a biomass of 68 g m-2 and 102 earthworms m-2 with 33g m-2 biomass were recorded in Kibera and Maili Saba, respectively. The earthworms isolated from both sites all epigeic with the metal content in Maili Saba suppressing their populations. This study has demonstrated that the use of untreated urban wastewater for irrigation has an adverse effect on nematodes and earthworms diversity and abundance

Medium-term impact of tillage and residue management on soil aggregate stability, soil carbon and crop productivity

Conservation agriculture is widely promoted for soil conservation and crop productivity increase, although rigorous empirical evidence from sub-Saharan Africa is still limited. This study aimed to quantify the medium-term impact of tillage (conventional and reduced) and crop residue management (retention and removal) on soil and crop performance in a maize–soybean rotation. A replicated field trial was started in sub-humid Western Kenya in 2003, and measurements were taken from 2005 to 2008. Conventional tillage negatively affected soil aggregate stability when compared to reduced tillage, as indicated by lower mean weight diameter values upon wet sieving at 0–15 cm (PT <0.001). This suggests increased susceptibility to slaking and soil erosion. Tillage and residue management alone did not affect soil C contents after 11 cropping seasons, but when residue was incorporated by tillage, soil C was higher at 15–30 cm (PT*R = 0.037). Lack of treatment effects on the C content of different aggregate fractions indicated that reduced tillage and/or residue retention did not increase physical C protection. The weak residue effect on aggregate stability and soil C may be attributed to insufficient residue retention. Soybean grain yields tended to be suppressed under reduced tillage without residue retention, especially in wet seasons (PT*R = 0.070). Consequently, future research should establish, for different climatic zones and soil types, the critical minimum residue retention levels for soil conservation and crop productivity