Nutrient requirements of rainfed lowland rice in Cambodia

摘要

In most rainfed lowlands of Cambodia, soils used for rice cultivation are low in available nitrogen (N), phosphorus (P) and potassium (K), and have low organic matter content and low cation-exchange capacity. Over the last 4 years, areas cultivated to rice have increased substantially from about 1.9 to 2.1 million hectares, of which rainfed lowlands comprise about 88%. The average rice yield increased from about 1.2 to 1.8 t ha-I , even though nutrient deficiency remains a serious constraint for lowland rice production. The paper reviews current understanding of the nutrient requirements of rain fed lowland rice in Cambodia. Field and greenhouse trials have classified widespread N and P responses and, on sandy soils, K and sulfur responses. Recommended fertilizer rates (in kg ha-1) for rice vary for the different nutrients: for N, from 20 to 120, for P, from 4 to 15, and for K, from 0 to 33. Recommendations are made for each soil type identified in the Cambodian Agronomic Soil Classification system. The need for further work on nutrient requirements of rice and other agricultural crops is also discussed.