Farming methods, varieties and seasons on soil nutrients and agronomic performance of direct-seeded rice in rainfed lowlands

Two farming methods (conventional, CFM and organic, OFM), and three lowland rice varieties (NSICRc110, IR64 and NSIC Rc 124 H) were grown in 2006-2007 wet and dry seasons plantings to determine their agronomic performance and soil nutrient status of direct-seeded rice in lowland rainfed conditions. Results showed that method of farming affected the growth during WS but not the growth and yield components of the rice plants in DS with CFM the most number of productive tillers. Lowland rice varieties affected both agronomic parameters in both planting season. NSIC Rc 110 produced the heaviest straw, most number of productive tillers and heaviest grain yield during WS. Both NSIC Rc110 and IR64 had comparable number of productive tillers, filled grains per panicle and 1000-grain weight but higher than NSIC Rc 124H in DS. NSIC Rc 124H produced more spikelets per panicle during WS, and longer panicle and more spikelets per panicle during DS plantings. Growth and yield component of the rice plant was generally affected by season. Recorded soil parameters were not affected by farming methods, although CFM has a slight increase in percentage OM was observed. Lowland rice varieties did not affect the soil parameter, with hybrid variety obtaining a slight accumulated OM content, while higher N removal was observed from NSIC Rc 110. The interaction effect between farming methods and lowland rice varieties was observed, with the highest pH (6.06) on OFM using IR64. Across season, percentage OM, percentage N and available P slightly increased in value towards the DS, whereas a decreasing value of pH (towards acidity) was observe in DS planting. In general, pH, P and K analyses in soil were still sufficient and conformed with the standard data, while percentage OM and percentage N including S were within the critical level of deficiency. This demonstrates that NSIC Rc 110 can be grown either in CFM and OFM with better performance and sustained soil nutrient status in both planting seasons under lowland rainfed conditions.