ABSTRACT

Two field experiments were conducted in Western and Eastern Farms of the National Root Crops Research Institute Uniudike between 2006 and 2007, to investigate the response of maize (Zea inay.s L) and sweet potato (Ijioinoea ha/a/ar (L.) Lam) cropping systcm to nitrogen rates in Umudike in the Ilumid Tropical Environment of South-eastern Nigeria. Nitrogen lcvels of 0. 40, 80 and I 20kg/ha were applied. The treatments were laid out in a 2 x 4 factorial in randomized complete block design with three replicates. Soil and climatic data of (lie experimental sites were obtained for the study. Results of the experiment showed that in both years, sole cropping differed significantly (P < 0.05) from intercropping. 1-ligher yields were achieved in sole cropping (maize, 2.45t/ha; sweet potato, 1 8.3 1 t/ha) than intercrops (maize, 1. 1 Ot/ha; sweet potato, 8.99t/ha) in 2006. The corresponding values for 2007 were sole crops (maize, 2.49t/ha sweet potato, 15.701/ha) and intercrops (maize, I .831/ha; sweet potato, 8.221/ha). Interaction of cropping system x nitrogen rates showed that in maize, yields were highest with sole crop that received l20kgN/ha (3.76 and 3.801/ha) and lowest when the intercrop did not receive N (0.82 and 0.87/ha) in 2006 and 2007. respectively. In sweet potato they were highest with sole crop at l20kgN/ha application (27.16 and 23.33/ha) and lowest when intercrop at 0kg/ha (3.95 and 2.051/ha) in 2006 and 2007, respectively. Weed bioniass was not significantly (P>0.05) affected by the cropping systems and nitrogen rates except br total dry weight which were influenced by the nitrogen at I 20kgN/ha. Land equivalent ratio (LER) was >1.0 indicating yield advantage of the intercropping system except when maize was intercropped with sweet potato at 0kgN/ha where LER of 0.97 was obtained in 2007. This shows that OBA super 2 maize could be successfully inteucropped with sweet Potato TIS/0087 for optimum yield. Also optimum economic yields were obtained when maize was combined with sweet potato at 80 and l20kgN/ha.