Review of Rice Response to Fertilizer Rates and Time of Nitrogen Application in Ethiopia

摘要

Rice productivity in Ethiopia is estimated at 2.8 t ha~(-1), which is much lower than the World's average of 4.4 t ha~(-1). Weeds, pests, soil nutrient deficiencies and terminal moisture stress are the major causes of low rice productivity in Ethiopia. Poor soil fertility is among the major factors limiting the rice production. Appropriate fertilizer application is an important management practice to improve soil fertility and production of rice. Availability of plant nutrients, particularly nitrogen at various plant growth stages is of crucial importance in rice production. Recommendations on different period of nitrogen fertilizer application were given for various production systems. Traditionally, Diammonium phosphate and urea (supplying nitrogen and phosphorus) were the major fertilizers used by farmers in Ethiopia, creating nutrient imbalances in soils. Therefore, to make the soil well supplied with all the plant nutrients in the readily available form and to maintain good soil health, it is necessary to use organic manures in conjunction with inorganic fertilizers to obtain optimum yields. The integrated use of NP and FYM gave higher yields than application of either NP or FYM alone for many crops production. Different experiments were conducted to tackle rice soil fertility constraints. The major focuses of the experiments include inorganic fertilizers application rates, application times and their integration with organic fertilizers. The review paper summarizes the results of the experiments conducted on rice fertilizer rates and timings of nitrogen applications.