Trends in productivity and nutrient dynamics under improved soil nutrient management techniques for rice in the rainfed lowlands of Cambodia

摘要

Increasing rice yields in rainfed lowlands of Cambodia relies on better understanding of balanced nutrition and matching crop demand with nutrient supply. A field experiment was conducted for 6 successive seasons on a sandy soil (Plinthustalf) to assess the effects on soil properties, rice yield and profits under organic (O), inorganic (I), and combined organic and inorganic (OI) supply systems. In each system, there were four nutrient regimes: application once to the first crop (FR1); application to the first wet season crop only and land fallow in the dry season (FR2); applied to every wet season crop (FR3), and; applied to every wet and dry season crop (FR4). Composted cow manure was applied at 5 t/ha, whereas N, P and K were applied at recommended rates. Under the O system, the yield accumulated after 6 crops was5.9, 5.0, 8.7, and 11.7 t/ha for FR1, R2, FR3, and FR4 regimes, respectively. Under I system, yields increased by 49-59 %. Under the OI system, the cumulative yields were 8.6, 7.3, 14.3, and 16.3 t/ha for FR1, FR2, FR3, and FR4 regimes, respectively. After 6 crops, soil pH, soil organic C and exchangeable K increased, there was no change in soil N, and extractable P increased with the OI system. The combined OI system was the most productive and profitable nutrient management approach.