Soil biodiversity for agricultural sustainability
Brussaard, L. ; Ruiter, P.C. de; Brown, G.G. - \ 2007
Agriculture, Ecosystems and Environment 121 (2007)3. - ISSN 0167-8809 - p. 233 - 244.
ecosystem function relationship - microbial communities - functional stability - nitrogen mineralization - biological indicators - bacterial community - crusted soil - west-africa - diversity - productivity
We critically highlight some evidence for the importance of soil biodiversity to sustaining (agro-)ecosystem functioning and explore directions for future research. We first deal with resistance and resilience against abiotic disturbance and stress. There is evidence that soil biodiversity does confer stability to stress and disturbance, but the mechanism is not yet fully understood. It appears to depend on the kind of stress and disturbance and on the combination of stress and disturbance effects. Alternatively, community structure may play a role. Both possible explanations will guide further research. We then discuss biotic stress. There is evidence that soil microbial diversity confers protection against soil-borne disease, but crop and soil type and management also play a role. Their relative importance as well as the role of biodiversity in multitrophic interactions warrant further study. Henceforth, we focus on the effects of plant and soil biodiversity on nutrient and water use efficiencies as important ecological functions in agroecosystems. The available evidence suggests that mycorrhizal diversity positively contributes to nutrient and, possibly, water use efficiency. Soil fauna effects on nutrient and water use efficiencies are also apparent, but diversity effects may be indirect, through effects on soil structure. We present a conceptual diagram relating plant and soil biodiversity with soil structure and water and nutrient use efficiencies as a framework for future studies. We then consider how cropping systems design and management are interrelated and how management options might be interfaced with farmers¿ knowledge in taking management decisions. Finally, we attempt to express some economic benefits of soil biodiversity to society as part of a wider strategy of conserving and using agrobiodiversity.
Soil fauna and organic amendment interactions affect soil carbon and crop performance in semi-arid West Africa
Ouédraogo, E. ; Brussaard, L. ; Stroosnijder, L. - \ 2007
Biology and Fertility of Soils 44 (2007)2. - ISSN 0178-2762 - p. 343 - 351.
humid tropics - crusted soil - decomposition - earthworms - termites - quality
A field experiment was conducted at Kaibo in southern Burkina Faso on an Eutric Cambisol during the 2000 rainy season to assess the interaction of organic amendment quality and soil fauna, affecting soil organic carbon and sorghum ( Sorghum bicolor L. Moench) performance. Plots were treated with the pesticides Dursban and Endosulfan to exclude soil fauna or left untreated. Sub-treatments consisted of surface-placed maize straw ( C/N ratio= 58), Andropogon straw ( C/N ratio= 153), cattle dung ( C/N ratio= 40), sheep dung ( C/N ratio= 17) or compost ( C/N ratio= 10) and the control. Organic amendments were applied at a dose equivalent to the application of 40 kg N ha(-1). The presence of soil fauna increased soil total carbon by 32% and grain yield production by 50%. The interaction between high C/N ratio organic amendment, Andropogon straw ( SA), and soil fauna reduced soil carbon build-up. We suggest that this is due to a priming effect of SA on soil organic matter in the presence of soil fauna. We also suggest that the interaction between soil fauna and easily decomposable organic amendment led to the smallest decrease in soil carbon build-up. It is concluded that in semi-arid West Africa, in the presence of soil fauna, soil carbon build-up is more affected by the quality of organic amendments than the quantity of carbon inputs. Sorghum grain yield production was significantly reduced in the absence of soil fauna. High C/N ratio organic amendment interacted negatively with soil fauna in its effects on crop performance. We propose that the effect of soil fauna on soil carbon build-up and crop performance can be optimised by using high quality organic matter of supplementing low-quality organic matter with inorganic nitrogen in semi-arid West Africa.
Soil fauna and soil function in the fabric of the food web
Brussaard, L. ; Pulleman, M.M. ; Ouédraogo, E. ; Mando, A. ; Six, J. - \ 2007
Pedobiologia 50 (2007)6. - ISSN 0031-4056 - p. 447 - 462.
organic-matter dynamics - semi-permanent cultivation - sudano-sahelian conditions - habitable pore-space - crusted soil - phosphorus allocation - earthworm activity - microaggregate formation - nitrogen mineralization - ecosystem engineers
Over the last four decades, spanning David Coleman's career, and in no small measure thanks to him, soil ecologists have made tremendous progress in describing and understanding the overwhelming complexity of biological, biophysical and biochemical interactions in soil. These interactions shape the soil as a habitat for the soil food web and the vegetation and, thereby, regulate the two main life-supporting processes on Planet Earth: production and decomposition. Changes in decomposition and production processes are governed by (human-induced) changes in vegetation composition/cover, the amounts and quality of organic residues and (in)organic fertilizers entering the soil. Such modifications alter the physical environment and the soil biota. Hence, decomposition and production processes cannot be understood and/or manipulated without explicitly addressing the composition and activity of the soil food web. Using a conceptual model, we argue that quantitative understanding of biophysical interactions, in particular those between soil fauna and soil structure, are paramount to understanding biological and biochemical processes in soil and the availability of water and nutrients to plants. The need to increase the efficiency of crop production worldwide, to reverse soil degradation and to increase soil resilience will set the agenda for soil ecologists in the near future
Soil macrofauna affect crop nitrogen and water use efficiencies in semi-arid West Africa.
Ouédraogo, E. ; Mando, A. ; Brussaard, L. - \ 2006
European Journal of Soil Biology 42 (2006)suppl. 1. - ISSN 1164-5563 - p. S275 - S277.
crusted soil - termites
It is increasingly recognised that soil fauna have a significant role in soil processes affecting nutrient availability and crop performance. A field experiment was conducted in southern Burkina Faso (West Africa) to investigate the contribution of soil fauna to nutrient availability and crop performance after application of different organic materials with contrasting qualities. A split plot design with four replications was laid out. The main treatment was the use of insecticides, to establish plots without fauna next to plots with fauna. The sub-treatments consisted in the application of Andropogon straw, cattle dung, maize straw, compost or sheep dung and a control. Soil fauna significantly increased crop water use efficiency. Crop nutrient use efficiency was high with the use of easily decomposable organic material in the presence of soil fauna. Supplementing low quality organic resources with mineral nitrogen is required to optimise the effects of their interaction with soil fauna towards enhanced crop nutrient and water use efficiencies.
Effects of tillage, organic resources and nitrogen fertiliser on soil carbon dynamics and crop nitrogen uptake in semi-arid West Africa
Ouédraogo, E. ; Mando, A. ; Stroosnijder, L. - \ 2006
Soil & Tillage Research 91 (2006)1-2. - ISSN 0167-1987 - p. 57 - 67.
matter fractions - crusted soil - land-use - particulate - phosphorus - rehabilitation - management - quality - systems - mulch
Tillage, organic resources and fertiliser effects on soil carbon (C) dynamics were investigated in 2000 and 2001 in Burkina Faso (West Africa). A split plot design with four replications was laid-out on a loamy-sand Ferric Lixisol with till and no-till as main treatments and fertiliser types as sub-treatments. Soil was fractionated physically into coarse (0.250-2 mm), medium (0.053-0.250 mm) and fine fractions (<0.053 mm). Particulate organic carbon (POC) accounted for 47-53% of total soil organic carbon (SOC) concentration and particulate organic nitrogen (PON) for 30-37% of total soil nitrogen concentration. The POC decreased from 53% of total SOC in 2000 to 47% of total SOC in 2001. Tillage increased the contribution of POC to SOC. No-till led to the lowest loss in SOC in the fine fraction compared to tilled plots. Well-decomposed compost and single urea application in tilled as well as in no-till plots induced loss in POC. Crop N uptake was enhanced in tilled plots and may be up to 226 kg N ha-1 against a maximum of 146 kg N ha-1 in no-till plots. Combining crop residues and urea enhanced incorporation of new organic matter in the coarse fraction and the reduction of soil carbon mineralisation from the fine fraction. The PON and crop N uptake are strongly correlated in both till and no-till plots. Mineral-associated N is more correlated to N uptake by crop in tilled than in no-till plots. Combining recalcitrant organic resources and nitrogen fertiliser is the best option for sustaining crop production and reducing soil carbon decline in the more stabilised soil fraction in the semi-arid West Africa
Organic resources and earthworms affect phosphorus availability to sorghum after phosphate rock addition in semi-arid West Africa
Ouédraogo, E. ; Brussaard, L. ; Mando, A. ; Stroosnijder, L. - \ 2005
Biology and Fertility of Soils 41 (2005)6. - ISSN 0178-2762 - p. 458 - 465.
agricultural intensification - humid tropics - agroecosystem function - soil biodiversity - crusted soil - mulch - decomposition - termites - quality
A field experiment was laid out in Burkina Faso (West Africa) on an Eutric Cambisol to investigate the interaction of organic resource quality and phosphate rock on crop yield and to assess the contribution of earthworms (Millsonia inermis Michaelsen) to P availability after phosphate rock application. Organic resources of different quality were applied at a dose equivalent to 40 kg N ha¿1 with or without phosphate rock from Kodjari (Burkina Faso) at a dose equivalent to 25 kg P ha¿1, and were compared with control and single phosphate rock treatments in a factorial complete block design with four replicates. Sorghum (Sorghum bicolor L. Moench) variety SARIASSO 14 was grown. Sheep dung had the highest impact on earthworm casting intensity followed by maize straw. Combining organic resources with phosphate rock reduced earthworm casting activities compared to a single application of organic resources or phosphate rock. Addition of phosphate rock to maize straw reduced P availability in earthworm casts whereas combining sheep dung or compost with phosphate rock increased P availability. The contribution of earthworms to Kodjari phosphate rock solubilisation mainly occurred through their casts, as the available P content of casts was 4 times higher than that of the surrounding soil
Long-term effect of tillage and manure application on soil organic fractions and crop performance under Sudano-Sahelian conditions
Mando, A. ; Ouattara, B. ; Sédogo, M. ; Stroosnijder, L. ; Ouattara, K. ; Brussaard, L. ; Vanlauwe, B. - \ 2005
Soil & Tillage Research 80 (2005)1-2. - ISSN 0167-1987 - p. 95 - 101.
matter dynamics - crusted soil - west-africa - rehabilitation - residues - mulch
Human-induced degradation of natural resources in general and of soil in particular, is a major problem in many regions, including the Sudano-Sahelian zone. The combined effects of tillage and manure application on Lixisol properties and on crop performance were investigated at Saria, Burkina Faso, to find efficient soil management practices to improve soil fertility. A randomized block design with four treatments (hand hoeing only, hand hoeing+manure, ploughing only, oxen ploughing+manure) in three replications was started in 1990. Ten years later, total soil organic (SOC), particulate organic matter and C mineralization were measured. Initial SOC concentration was 4 mg/g and dropped to 2.1 mg/g soil in ploughed plots without manure and to 2.5 mg/g soil in hoed plots without manure. Manure addition mitigated the decrease of SOC in ploughed plots and even built up SOC in hoed plots, where it increased to 5.8 mg/g soil. Manure had a large effect on the fractions in which SOC was stored. In ploughed plots, a large amount of SOC was stored in physical particles >0.25 mm, while in hand hoed plots the maximum SOC was stored in finer fractions. In the topsoil, hoeing and manure resulted in a higher SOC than ploughing with no manure. However, in the 15¿25 cm layer, particularly in September, particulate organic matter was greater in ploughed plots with manure than in hoed plots with manure. Crop yields were highest on ploughed+manure plots and lowest on ploughed plots with no manure. We conclude that applying manure annually mitigates the negative effect of ploughing and hand hoeing on SOC and related properties and therefore can contribute to the sustainability of the agricultural system in the Sudano-Sahelian zone
Wind effects on spatial variability in pearl millet yields in the Sahel
Sterk, G. ; Stein, A. ; Stroosnijder, L. - \ 2004
Soil & Tillage Research 76 (2004)1. - ISSN 0167-1987 - p. 25 - 37.
crop growth variability - west-africa - erosion control - semiarid niger - surface characteristics - farmers knowledge - crusted soil - transport - residue - sediment
Growth and yield of pearl millet (Pennisetum glaucum) in the West African Sahel are characterized by significant spatial variability at short distances (5-20 m). Several studies have suggested that this variability is caused by aeolian redistribution of relatively fertile topsoil material. The objectives of this study were (i) to quantify storm-based erosion/deposition patterns within a Sahelian millet field and (ii) to determine the effects of topography, erosion and deposition on millet growth and yield. An experiment was conducted at a research station in southwest Niger, on a sandy, siliceous, isohyperthermic Psammentic Paleustalf. Twenty-one sediment catchers were installed in a 40 m x 60 m plot within a pearl millet field. Four wind erosion events occurred during the 1993 growing season. Maps of wind-blown mass transport were created for each storm by applying a geostatistical space-time procedure. Maps showing the spatial distribution in erosion and deposition were derived by differentiation of mass transport in the direction of the mean wind. For 21 sub-plots of 4 m x 5 m the elevation, wind-blown mass balance, millet growth and yield were quantified. A correlation analysis showed neither a significant relationship between millet yield and topography, nor between millet yield and erosion/deposition. It is concluded that only wind-blown sediment transport occurring within one growing season cannot explain the spatial variability in millet growth and yield. A new hypothesis is defined that suggests aeolian erosion/deposition patterns as observed in previous studies were not the cause but more likely the result of spatial variability in millet growth. (C) 2003 Elsevier B.V. All rights reserved.