2015 年 59 巻 3 号 p. 146-153
The present study investigated a new cropping system for cultivation of off-season yam after lowland rice. The experiments were carried out at IITA in Ibadan, Nigeria. The institute is located in a derived savanna, with the rainy season occurring from April to November and the dry season from December to March. Rice and white yam crops were rotated. The dormancy period of seed tubers was shifted using vine propagation. The first crop in this experiment was rice (September 2009 to January 2010), followed by yam (February to September 2010), and then rice again (September 2010 to January 2011). Four treatments were applied: a control of rice–yam–rice rotation without nitrogen (N) application at any phase; rice without N, followed by yam with 60 kg ha-1 N followed by rice without N; rice with 30 kg ha-1 N followed by yam without N, followed by rice without N; and rice with 30 kg ha-1 N, followed by yam with 60 kg ha-1 N, followed by rice without N. Nitrogen application to the yam cropping increased tuber yield. The comparable yields between the first and second rice croppings in the control treatment indicated that the intervening yam cropping did not reduce the yield of rice. The yam cropping did not leave behind additional effective nutrients that would affect rice cropping. These results suggested that lowland rice–yam crop rotation is a suitable new system for sustainable land use for yam.
