Seasonal water use and water productivity of millet-based cropping systems in the Nigerian Sudan savanna near Kano

Quantification of resource use in dominant millet–cowpea (M–C) and millet–sorghum–cowpea (M–S–C) intercropping systems in peasant agriculture was carried out using farmers’ practices, under the low rainfall and poor nutrient supply situations of the semi-arid zone of Nigeria. On-station trials were conducted at Minjibir near Kano during the 1994 and 1995 rainy seasons to determine the components of the water balance and compare water use (WU) and water productivity of millet planted sole (SM) at the recommended optimum densities and intercropped at farmers’ planting densities under two levels of soil fertility. Infiltration rates were generally high, with an overall mean in the porous sandy soil of 17 cm h−1. Deep drainage losses accounted for 15% of annual rainfall in a low rainfall season (1995) and an estimated more than 20% in the wet 1994 season. Additional top dress NPK fertilizers (OM+IF) to cereals prior to the commencement of reproductive stages, increased soil water extraction in the intercrops in the drier year, for which soil water status was, therefore, higher in plots where only organic manure (OM) was applied. The relatively higher annual rainfall in 1994 generally increased soil water use. Later maturity of sorghum in the M–S–C intercrop increased WU of this cropping system, particularly in 1995. SM produced significantly (P<0.01 in 1994 and P<0.05 in 1995) higher total dry matter (TDM) than the intercrops, a trend shown over the complete growing season most of the time, with the exception of OM SM in 1995. The total grain yield was significantly (P<0.01) higher in SM in the wet 1994 season. Millet, particularly when intercropped, used water more efficiently for grain production in 1995 along with other limiting resources. It showed better adaptation to moisture stress by producing similar (P=0.79) harvest indices (HIs) in sole and intercropped millet. HIs of the sole cereals and the OM M–C were relatively higher in the 1995 than in the wet 1994 season.