Factors affecting differences in the rainy season rice yield in a lowland area of a mountainous village in Lao PDR

The unevenness of rice productivity in lowland areas is caused by differences in farming techniques, accessibility of water, planting environment, and other field-specific factors. In order to increase rice production in low-productivity fields, this study examined the factors affecting yield reduction. In this study, the influence of water conditions, farming activities, and soil fertility on rice yield were analyzed in a lowland area located in the northern part of Lao PDR. A field survey was conducted in a village in Vientiane Province during the rainy season of 2013. Water conditions were observed (i) prior to land preparation, (ii) between land preparation and transplanting, and (iii) after transplanting. Farming activities were recorded in each lowland rice field weekly from June to August. Yield surveys were also conducted in 47 field blocks, and soil samples were collected for soil fertility analyses. The ponding of fields commenced in the middle of June, and extended from the upper part to the lower part of the lowland area. Transplanting was conducted following the distribution of surface water, and no serious water shortages were observed after transplanting in the surveyed areas. There was no correlation between grain yield and the content of total nitrogen or available phosphorus in the field soil. Significant differences in grain yield were detected between direct and plot-to-plot irrigation, early and late ponding, and transplanting in July and in August. The results suggest that water shortages and the delay of field ponding before land preparation led to late transplanting which caused yield reduction.