On-Farm Evaluation of Nitrate-Nitrogen Dynamics Under Maize in the Northern Guinea Savanna of Nigeria

Abstract

SummaryNitrate-nitrogen was analysed over two cropping seasons in 57 farmers' fields in the northern Guinea savanna of Nigeria. Differences between fields were at least five-fold and often ten-fold irrespective of fertilization rates. Average concentrations were highest at the beginning of the rainy season. Loamy soils had a later peak for nitrate release and maintained high concentrations for a longer period after the start of the rains than the more sandy soils. Nitrate-N was not correlated with soil organic carbon or total nitrogen content. Grain yield of maize was closely associated with nitrate-N in the soil but not with organic carbon or total N. Four patterns of nitrate-N release over the season could he differentiated using cluster analysis. Soil texture, soil pH, soil organic carbon, stover management and cropping history contributed most to a differentiation of the four cluster groups in a discriminant model. There was wide variability in the inherent soil-nitrate level and in its importance in explaining differences in yield among farmers' fields. The development of technologies resulting in improved nitrogen availability or better nitrogen utilization should be based on research of inherent soil processes. For the transfer of such technologies, recommendation domains should be defined based on different native patterns of soil-nitrogen availability.