A better understanding of differences in nutrient recovery


Nutrient recovery, defined as the proportion of nutrients supplied that is taken up by the crop in above-ground parts, varies strongly from field to field. The general mechanisms are known, yet poorly understood in quantitative terms. Fertilizer recommendations, e.g. using QUEFTS, are based on simple rules of thumb for expected recovery fractions. These are typically derived from experiments that may not reflect on-farm field conditions very well. As such, fertilizer recommendations and expectations of crop yields are on average pretty good, yet come with large errors at farm level. Farmers may be more realistically informed about expected yield responses when fertilizer recovery is better understood, especially under poor soil fertility conditions with low yields.

In this project, we seek to better understand the mechanisms and evaluate available modelling approaches that describe plant-microbe competition and nutrient immobilization into organic matter or other pools in the soil. You will review literature and compare and test simple models to formulate hypothesis that help explain the difference between responsive and non-responsive soils. These models will be confronted with data from a long term experiment on 23 farms in Western Kenya.

Useful references

He, P., S.-Z. Wan, X.-M. Fang, F.-C. Wang and F.-S. Chen (2016). "Exogenous nutrients and carbon resource change the responses of soil organic matter decomposition and nitrogen immobilization to nitrogen deposition." Scientific Reports6: 23717.

Ichami, S. M., K. D. Shepherd, A. M. Sila, J. J. Stoorvogel and E. Hoffland (2019). "Fertilizer response and nitrogen use efficiency in African smallholder maize farms." Nutrient Cycling in Agroecosystems113(1).

Nguyen, M. H. (2003). Modelling of K dynamics in soils and K uptake by crops. In: Soil potassium dynamics under intensive rice cropping. A case study in the Mekong Delta, Vietnam. PhD thesis Wageningen University. Chapter 6. 

Njoroge, S., A. G. T. Schut, K. E. Giller and S. Zingore (2019). "Learning from the soil’s memory: Tailoring of fertilizer application based on past manure applications increases fertilizer use efficiency and crop productivity on Kenyan smallholder farms." European Journal of Agronomy105: 52-61.

Njoroge, S., A. G. T. Schut, K. E. Giller and S. Zingore (2017). "Strong spatial-temporal patterns in maize yield response to nutrient additions in African smallholder farms." Field Crops Research214: 321-330.

Wolf, J., C. T. de Wit and H. van Keulen (1989). "Modeling long-term crop response to fertilizer and soil nitrogen. I. Model description and application." Plant and Soil 120 (1989) 1.

Van Duivenbooden, N., C. T. de Wit and H. van Keulen (1995). "Nitrogen, phosphorus and potassium relations in five major cereals reviewed in respect to fertilizer recommendations using simulation modelling." Fertilizer research44(1): 37-49.




A successful completion of the course Analysing Sustainability of Farming Systems or QUALUS. Ability to use R or a strong interest in learning it is required.

Time and Location   

2019, Wageningen 


Tom Schut                                          0317-482454                                       tom.schut@wur.nl

Samuel Njoroge                                                                                                                                                                                  Samuel.njoroge@wur.nl