Near infrared reflectance spectroscopy (NIRS) could be used for characterization of soil nematode community

Studying soil nematofauna provides useful information on soil status and functioning but requires high taxonomic expertise. Near infrared reflectance (NIR) spectroscopy (NIRS) has been reported to allow fast and inexpensive determination of numerous soil attributes. Thus the present study aimed at assessing the potential of NIRS for determining the abundance and diversity of soil nematodes in a set of 103 clayey topsoil samples collected in 2005 and 2006 from agricultural soils in the highlands of Madagascar. The morphological characterization of soil nematofauna involved extraction through elutriation then counting under binoculars and identification at family or genus level using microscopy, on ca. 150-g fresh soil samples. Taxa were assigned to five trophic groups, namely bacterial feeders, fungal feeders, obligate plant feeders, facultative plant feeders, and omnivores and predators (together). In addition, four ecological indexes were calculated: the Enrichment index, Structure index, Maturity index, and Plant parasitic index. Oven-dried (40 degrees C) = 2) or acceptable (RPD >= 1.6). Predictions were accurate, acceptable, or quasi-acceptable (RPD >= 1.4) for several of the six most abundant taxa, and to a larger extent, for most trophic groups (except facultative plant feeders); but they could not be made for taxa present in a small number of samples or at low abundance. By contrast, NIRS prediction of relative abundances (in proportion of total abundance), was poor in general, as was also the prediction of ecological indexes (except for the 2006 set). On the whole, these results were less accurate than NIRS predictions of soil attributes often reported in the literature. However, though not very accurate, NIRS predictions were worthwhile considering the labor-intensity of the morphological characterization. Most of all, NIRS analyses were carried out on subsamples that were probably too small (5 g) to allow representative sampling of nematofauna. Using larger samples for NIRS (e.g. 100 g) would likely result in more accurate predictions, and is therefore recommended. Scanning un-dried samples could also help improve prediction accuracy, as morphological characterization was carried out on samples not dried after sampling. Examining wavelengths that contributed most to NIRS predictions, and chemical groups they have been assigned to, suggested that NIRS predictions regarding nematofauna depended on constituents of both nematodes and preys' food. Predictions were thus based on both nematofauna and soil organic properties reflected by nematofauna

Earthworm Functional Groups, Residue Quality and Management Impact on Upland Rice Growth and Yield – An Experimental Study in the Madagascar Highlands

International audienceAims: In Madagascar, agroecological practices to increase and sustain upland rice productivity are based on an intensification of soil ecological processes. Study Design: The effects of earthworm presence and identity (Pontoscolex corethrurus, Dichogaster saliens, or no earthworms), residue presence and identity [Crotalaria grahamiana (Fabaceae), Desmodium uncinatum (Fabaceae), Stylosanthes guianensis (Fabaceae), Eleusin

Effects of living mulches or residue amendments on soil microbial properties in direct seeded cropping systems of Madagascar

There is growing recognition for the need to study the impact of agricultural land uses on biological and biochemical properties of soils. In Madagascar, cropping systems based on direct seeding with permanent vegetation cover provide a new means for sustainable agriculture to protect the environment and make the most of natural resources. This study assessed the effects of different direct seeding mulch-based cropping systems on soil microbial biomass and activities. The soil was andic Dystrustept. Samples of the soil were taken from 0 to 5 cm soil layer of three direct seeding mulch-based cropping systems (DMC using crop residues and living mulches). The samples were compared with samples from conventionally tilled plots (CT) and natural fallows (NF). The field experiments were carried out over a 12-year-period and two types of amendment were applied once a year at sowing, farmyard manure (FYM) and farmyard manure combined with an NPK chemical fertilizer. The C and N content, microbial basal respiration and biomass and p-glucosidase, urease and acid phosphatase activities were determined. The results showed that there was no interaction between soil management strategies and the use of fertilizer. Furthermore, the fertilizer did not affect the soil C and N content or the acid phosphatase and urease activities. Farmyard manure with added NPK had a significantly greater effect than farmyard manure on its own, increasing the microbial biomass, soil respiration and beta-glucosidase activity up to 26%, 52% and 20%, respectively but there was no significant difference between natural fallows and direct seeding mulch-based cropping systems. However, conventional tillage showed a significantly lower soil microbial biomass, C content, microbial respiration and urease activity than natural fallows. The results for direct seeding mulch-based systems varied according to the microbial activities measured. However, soil p-glucosidase and acid phosphatase activities were significantly higher for the direct seeding mulch-based systems using crop residues than for the direct seeding mulch-based systems using living mulches. Direct seeding mulch-based systems with Desmodiurn uncinatum living mulch had significantly lower microbial biomass and respiration than the other direct seeding mulch-based systems. There was less evidence of change in the soil between natural fallow and direct seeding mulch-based systems but a higher build-up of some microbial properties was obtained for direct seeding mulch-based systems soil than in conventionally tilled soils and natural fallow

Candidate plants to help soil pest control in conservation agriculture: potential effects of 21 species used as cover crops in Madagascar

International audienc

Earthworm Functional Groups, Residue Quality and Management Impact on Upland Rice Growth and Yield – An Experimental Study in the Madagascar Highlands

International audienceAims: In Madagascar, agroecological practices to increase and sustain upland rice productivity are based on an intensification of soil ecological processes. Study Design: The effects of earthworm presence and identity (Pontoscolex corethrurus, Dichogaster saliens, or no earthworms), residue presence and identity [Crotalaria grahamiana (Fabaceae), Desmodium uncinatum (Fabaceae), Stylosanthes guianensis (Fabaceae), Eleusin

Development of a multi-criteria evaluation of agroecological practices involving soil biodiversity, agronomic performance and farmer perception

International audienceAn experiment has been designed in the Highlands of Madagascar withthe aim to produce multi-criteria indicators of performance ofagroecological practices. In this experiment, different traditionaland innovative practices were tested in field conditions with theassumption that practices that enhance soil biodiversity and soilecological processes are the one that best promote plant production,yield and sustainability. Both ecological and agronomic performanceswere confronted with socio-economic performance defined by farmers inorder to propose innovative practices adoptable by farmers.A 2-year field experiment with 16 different practices, replicated 4times, was designed in the Highlands of Madagascar with upland riceas the main crop. Many soil and plant parameters were measured: 73parameters to describe soil biodiversity and soil ecologicalprocesses, 19 descriptors to measure rice production, nutrition andyield, and 8 socio-economic descriptors.This study led to the production of a useful indicator allowing toevaluate an agroecological practice on the way it promotes soil healthand especially soil biodiversity, crop yield and socio-economicalrequirements which are the main limits for practice adoption. Wemeasured interesting relations between soil ecological descriptorsand agronomic descriptors

Development of a multi-criteria evaluation of agroecological practices involving soil biodiversity, agronomic performance and farmer perception

International audienceAn experiment has been designed in the Highlands of Madagascar withthe aim to produce multi-criteria indicators of performance ofagroecological practices. In this experiment, different traditionaland innovative practices were tested in field conditions with theassumption that practices that enhance soil biodiversity and soilecological processes are the one that best promote plant production,yield and sustainability. Both ecological and agronomic performanceswere confronted with socio-economic performance defined by farmers inorder to propose innovative practices adoptable by farmers.A 2-year field experiment with 16 different practices, replicated 4times, was designed in the Highlands of Madagascar with upland riceas the main crop. Many soil and plant parameters were measured: 73parameters to describe soil biodiversity and soil ecologicalprocesses, 19 descriptors to measure rice production, nutrition andyield, and 8 socio-economic descriptors.This study led to the production of a useful indicator allowing toevaluate an agroecological practice on the way it promotes soil healthand especially soil biodiversity, crop yield and socio-economicalrequirements which are the main limits for practice adoption. Wemeasured interesting relations between soil ecological descriptorsand agronomic descriptors