On-Farm Trial Network Generating Site-Specific Recommendations in Ghana

On-Farm Trial Network Generating Site-Specific Recommendations in Ghana

The 4R Solutions Project seeks to address the problem of variable yields in smallholder fields by providing a platform for the development of site-specific fertilizer recommendations for maize and rice, two of the major cereal crops produced in northern Ghana. The project has established multiple maize and rice Nutrient Omission Trials (NOTs) aimed at quantifying and explaining differences in maize and rice yields under varying soil fertility and farm conditions.

Low soil fertility has been identified as one of the major constraints to crop productivity in northern Ghana. Continuous cropping with minimal application of organic or inorganic nutrient sources in smallholder farms of northern Ghana has resulted in a decline in soil fertility beyond levels required to sustain good crop yields on most farms. The use of fertilizers to sustain soil fertility and restore crop productivity in smallholder farms of northern Ghana is often limited by the high cost of fertilizers, and limited access to available fertilizers.

Recent government initiatives have however led to increased access to, and affordability of fertilizers, resulting in increased fertilizer application. However, increased fertilizer application has not always generated the expected increase in crop productivity, particularly for key cereal crops such as maize and rice. This has been attributed to differences in crop yields between fields following the application of similar types and quantities of fertilizers.

While good yields have been attained on some farms, other farms have been characterized by below average yields, limiting opportunities to sustainably enhance crop productivity across the entire region. Differences in crop yields between farms are often the result of fertilizer recommendations that fail to consider the often-observed strong variations in soil fertility and farm conditions between farms, reflecting the need for site-specific fertilizer recommendations.


The 4R Solutions Project has established maize nutrient omission trials in all four of the project’s focal districts of Nanumba North, Nanumba South, East Gonja, and Kpandai, while rice nutrient omission trials have been established in the rice-growing districts of Nanumba North and East Gonja. Data from these trials will allow for the fine-tuning of current maize and rice fertilizer recommendations for nitrogen, phosphorus, and potassium, the three key nutrients that primarily limit crop productivity. These nutrient omission trial sites also have the dual role of serving as farmer training centers. Farmers will use the experimental plots to help identify and interpret visual crop nutrient deficiency symptoms, and understand the contribution of balanced nutrient application based on the science-based concept referred to as 4R nutrient stewardship. Put into practice, this concept helps to educate farmers on how they can meet and sustain their productivity goals by applying the Right sources of nutrient at the Right rate, Right time, and in the Right place.

The 4R Solutions project’s implementing partners are Fertilizer Canada, Cooperative Development Foundation of Canada (CDF-Canada), Global Affairs Canada (GAC), IPNI Canada, and African Plant Nutrition Institute (APNI). The project’s local cooperators in Ghana are Send Ghana and Savanna Agricultural Research Institute (SARI).

APNI Contributor: Dr. Samuel Njoroge, Project Manager – Nutrient Stewardship


Related links

4R Solution Project https://4rsolution.org/