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Wageningen, Netherlands

Kessler C.A.,Soil Physics and Land Management | van Duivenbooden N.,Wageningen University | Nsabimana F.,Reseau Burundi 2000 Plus | van Beek C.L.,Wageningen University
Nutrient Cycling in Agroecosystems | Year: 2015

Integrated soil fertility management (ISFM) is generally accepted as the most relevant paradigm for soil fertility improvement in the tropics. Successes however are mainly reported at plot level, while real impact at farm level and beyond remains scattered. As a consequence, many Sub-Saharan African countries continue experiencing soil nutrient mining and insecure and insufficient agricultural production. Since technology-driven projects at the plot level failed to bring ISFM to scale, a different approach is needed. This paper describes a bottom-up approach developed in Burundi, the “PIP approach”. It starts at farmer family level with the creation of an integrated farm plan (Plan Intégré de Paysan in French—PIP) and aims at wide-scale spreading of farmers’ intrinsic motivation to invest in activities that make the household more resilient and profitable, while moving towards sustainable agricultural intensification based on concepts of ISFM. As such, and once firmly embedded in and supported by village or district plans, agriculture becomes a business rather than a default activity inherited by parents, and ISFM an intrinsic aspect of farm management. In this paper the PIP approach as currently being implemented in Burundi is explained and discussed, with special reference to soil fertility management and some preliminary promising results. © 2015 The Author(s) Source

Schotanus D.,Soil Physics and Land Management | Meeussen J.C.L.,Nuclear Research and Consultancy Group | Lissner H.,Friedrich - Schiller University of Jena | van der Ploeg M.J.,Soil Physics and Land Management | And 4 more authors.
Environmental Science and Pollution Research | Year: 2014

Transport and degradation of de-icing chemical (containing propylene glycol, PG) in the vadose zone were studied with a lysimeter experiment and a model, in which transient water flow, kinetic degradation of PG and soil chemistry were combined. The lysimeter experiment indicated that aerobic as well as anaerobic degradation occurs in the vadose zone. Therefore, the model included both types of degradation, which was made possible by assuming advection-controlled (mobile) and diffusion-controlled (immobile) zones. In the mobile zone, oxygen can be transported by diffusion in the gas phase. The immobile zone is always water-saturated, and oxygen only diffuses slowly in the water phase. Therefore, the model is designed in a way that the redox potential can decrease when PG is degraded, and thus, anaerobic degradation can occur. In our model, manganese oxide (MnO2, which is present in the soil) and NO3- (applied to enhance biodegradation) can be used as electron acceptors for anaerobic degradation. The application of NO3- does not result in a lower leaching of PG nor in a slower depletion of MnO2. The thickness of the snowcover influences the leached fraction of PG, as with a high infiltration rate, transport is fast, there is less time for degradation and thus more PG will leach. The model showed that, in this soil, the effect of the water flow dominates over the effect of the degradation parameters on the leaching at a 1-m depth. © 2013 Springer-Verlag Berlin Heidelberg. Source

Schotanus D.,Soil Physics and Land Management | Van Der Ploeg M.J.,Soil Physics and Land Management | Van Der Zee S.E.A.T.M.,Soil Physics and Land Management
Hydrology and Earth System Sciences | Year: 2013

Transport of a tracer and a degradable solute in a heterogeneous soil was measured in the field, and simulated with several transient and steady state infiltration rates. Leaching surfaces were used to investigate the solute leaching in space and time simultaneously. In the simulations, a random field for the scaling factor in the retention curve was used for the heterogeneous soil, which was based on the spatial distribution of drainage in an experiment with a multi-compartment sampler. As a criterion to compare the results from simulations and observations, the sorted and cumulative total drainage in a cell was used. The effect of the ratio of the infiltration rate over the degradation rate on leaching of degradable solutes was investigated. Furthermore, the spatial distribution of the leaching of degradable and non-degradable solutes was compared. The infiltration rate determines the amount of leaching of the degradable solute. This can be partly explained by a decreasing travel time with an increasing infiltration rate. The spatial distribution of the leaching also depends on the infiltration rate. When the infiltration rate is high compared to the degradation rate, the leaching of the degradable solute is similar as for the tracer. The fraction of the pore space of the soil that contributes to solute leaching increases with an increasing infiltration rate. This fraction is similar for a tracer and a degradable solute. With increasing depth, the leaching becomes more homogeneous, as a result of dispersion. The spatial distribution of the solute leaching is different under different transient infiltration rates, therefore, also the amount of leaching is different. With independent stream tube approaches, this effect would be ignored. © 2013 Author(s). Source

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