On-farm assessment of a new early-maturing drought-tolerant rice cultivar for dry direct seeding in rainfed lowlands

摘要

Dry direct seeding of rice (DDSR) is becoming a common practice in drought-prone lowland areas where there is insufficient labor for transplanting, but early-season drought often causes poor crop establishment, which allows subsequent weed infestation. Although early-maturing drought-tolerant cultivars have been released in tropical Asia in the last decade, almost all farmers in these areas still use cultivars selected for irrigated lowlands. The objective of our study was to compare a new drought-tolerant cultivar (Rc348) and a popular cultivar of farmers (Rc10) in DDSR under rainfed lowland conditions. On-farm experiments in three villages in northern Luzon, the Philippines, showed that the yield of Rc10, but not Rc348, was negatively associated with soil drying. Although their average yields were comparable (Rc348, 3.03 t ha(-1); Rc10, 3.00 t ha(-1)), Rc348 yielded 34% more with moderate to severe weed infestation or soil dryness (3.12 vs. 2.33 t ha(-1)). Weed infestation increased with increasing soil dryness, but the weed pressure was more severe for Rc10 than for Rc348. Rc348 had a higher seedling emergence percentage, number of seedlings m(-2), and ground cover at 30 days after sowing than Rc10 in drought-prone fields at upper (drier) positions in the toposequence. These results were validated by an on station experiment with controlled drought stress at the International Rice Research Institute. We suggest that the adoption of newly released cultivars from the breeding programs for rainfed rice with reliable seedling emergence and early vigor in the presence of fluctuating soil moisture would stabilize the yield of DDSR in the target drought-prone areas.