INTEGRATION OF RICE CROP RESIDUE INTO SUSTAINABLE RICE PRODUCTION SYSTEM

Rice is the staple food for nearly 40% of the world's population. In M alawi, rice is ranked second only to maize as a cereal food crop. In r ainfed areas of Malawi, grain yields typically average 1.0-1:5 t ha(-1 ) while potential yield is 4-5 t ha(-1). To bridge the gap between cur rent and potential yields, several novel nutrient management systems w ere studied. Many research reports indicate that rice responds to sili con (Si) application as well as to nitrogen (N), phosphorus (P), and p otassium (K) which are commonly applied. Rice crop residues (straws an d hulls) are rich in Si and K, but are not utilized currently in rice production. The effect of rice-hurl ash, rice straw, and method of N a pplication (prilled or briquetted urea) on a transplanted rice crop wa s studied through field experiments in Malawi during 1995 and 1996. Ap plication of urea in briquette form increased rice grain yield by 1056 and 122 kg ha(-1) compared to prilled urea in the 1995 winter and 199 6 summer experiments, respectively. However in the 1996 winter experim ent, prilled urea was superior to urea briquette and increased the ric e grain yield by 307 kg ha(-1). Incorporation of rice straw significan tly sincreased rice grain yields over the control in three consecutive experiments. Rice-hull ash alone increased the rice grain yields in a ll three experiments up to 12%; however, the increase was not statisti cally significant. The combination of rice straw and rice-hull ash alo ng with optimum N rates (60 kg ha(-1)) increased the rice grain yields significantly in 1996 winter season but the increase was not signific ant in the other two experiments.