Abstract
The effects of the introduction of direct seeding, supplementary irrigation, and chemical fertilizers on rice grain yield were investigated in farmers’ paddy fields in a rain-fed rice-growing village in Northeast Thailand during the years 2002, 2003 and 2004. Since transplanting was carried out only under adequate water conditions, the unavailability of irrigation and small amount of rainfall during planting time limited the area transplanted, which accounted for less than 30% of the whole paddy field area. Nitrogen fertilizer was applied to paddy fields both with and without supplementary irrigation at approximately the same level per unit area. The yield survey in selected paddy plots showed that yields in direct-seeded paddy fields without supplementary irrigation were lower than those in other paddy fields with different planting methods and water regimes in 2002, when planted rice experienced a rain shortage from late June to late August. Similar results were obtained in 2003 and 2004 though there was no significant difference among yields statistically. Based on the crop performance evaluation for whole paddy field, direct-seeding method for rice was often inferior to the transplanting one, especially in paddy fields without supplementary irrigation. The recent prevalence of supplementary irrigation and application of chemical fertilizers was considered to contribute to the improvement of rice grain yield in unproductive paddy fields under rain-fed conditions. Direct-seeding method should be further improved in fields without supplementary irrigation.
