Yields of millet between shelterbelts in semi-arid northern Nigeria, with a traditional and a scientific method of determining sowing date, and at two levels of organic manuring

Abstract

Eucalyptus camaldulensis shelterbelts positively influenced yields of millet (Pennisetum glaucum) planted close to the belts. Only smaller distances between shelterbelts than used in semiarid Nigeria, certainly <100 m, can fully exploit crop protection from advected hot dry air. Yields in two years with completely different rainfall regimes, for a traditional determination of sowing date, based on the Ramadan, were statistically significantly less (20-40%) than those for a scientific method of determining sowing date, based on Kowal's method. Assistance in on-farm application of proper sowing dates is needed. Millet grown outside the influence of the belts yielded about 50% less when including both methods of determining the onset of the growing season. Soil moisture availability early in the season and its influence on growth, tillering, and grain filling most of all determined yield differences between plots. Substantial yield differences as function of distance from the belts could be explained by soil moisture at sowing and the effects of hot dry turbulent air generated by the belts on crop growth conditions. Compared to the best organic manuring that farmers could afford, half that amount gave yield losses near 35% in both years, suggesting that manuring is not yet optimum.