Yield Responses of Maize to Fertilizers in Ghana

Low soil productivity is one of the key challenges limiting maize yields in Ghana. A wide yield gap exists between farm and potential yields across most of the agroecological zones (AEZs) of Ghana. Despite low soil fertility challenges, the low use of fertilizers still predominates the smallholder farming system. To improve crop performance, there is a need for integrated soil fertility management across the AEZs. This calls for site-specific fertilizer recommendations that provide all nutrients in balanced proportions as per the nutrient status of the soil. However, current fertilizer recommendations were developed decades ago and mainly focused on macronutrients (NPK). These recommendations in the current context of soil fertility are considered blanket recommendations and do not take care of site-specific crop nutrient requirements. Secondary data of experimental trials of almost 1,700 data points were used to explore maize yield responses to different fertilizer treatments across various AEZs of Ghana. Maize yield responses to fertilizers were estimated, factors explaining yields were explored, and spatial yield maps were generated. Low to very high (2-10 t ha-1 ) yield responses were observed across the AEZs. Between 60 and 130 kg N ha-1 applied in combination with 45-90 kg P2O5 and 45-90 kg K2O ha-1 gave the highest yield responses. Yield responses were even higher where sulfur was applied in combination with NPK. The dataset used did not contain many experiments with micronutrients and therefore could not allow comparisons of yield responses on this aspect. There were observed relationships of soil properties with yield under control (i.e., zero fertilizer application) treatments, though the yields of control plots against percentage of soil organic carbon (% OC), percentage of soil total nitrogen (% TN), available phosphorus (Av. P), and pH varied from low to high, irrespective of their values. This implies that soil property data give us an index of nutrient levels but it is difficult to only rely on these to arrive at fertilizer recommendations. Other factors, such as maize variety potentials in nutrient utilization, rainfall pattern, and disease occurrence should be considered as well. Apart from the impact of individual soil properties on yield, interactions between soil nutrient content and/or other soil properties could also impact crop yields
Fertilizers, Soil properties, Maize
Bua, S., El Mejahed, K., MacCarthy, D., Adogoba, D.S., Kissiedu, I.N., Atakora, W.K., Fosu, M., Bindraban P.S., 2020. Yield responses of maize to fertilizers in Ghana. IFDC FERARI Research Report No. 2