The effect of tillage on performance of upland rice varieties in northern Laos

Abstract

The tradition of farmers in the uplands of Laos is to cultivate upland rice under slash and burn systems by planting rice for only one or two seasons and then allowing the soil to regenerate fertility. However, the recent government policy is to eliminate the slash and burn cultivation and to encourage farmers to adopt more permanent rice cropping systems. Under such continuously cropping of upland rice, the yields become low and unstable. Soil compaction caused by planting without tillage could be one of the factors to decrease upland rice productivity. Therefore, tilling the soil for better root penetration may have the potential to increase upland rice yields in continuously cropped rice systems. The objectives of this study were (1) to observe whether a mild tillage treatment (soil disturbance around each hill at planting) could increase upland rice productivity as compared to the traditional dibbled planting technique; to determine the performances of five rice varieties grown under such tillage and no-tillage conditions. The experiment was conducted in 2004 on the plots with the history of continuous planting of upland rice for 2 years at two locations on sloping land in Luang Prabang province, northern Laos. The experimental designs were similar at both locations being a split-plot with three replications. The main plots were under either treated with tillage or no-tillage soil preparations. Sub plot treatments were five upland rice varieties i.e Chaomad, Laboun, Makhinsung, Nok and Vieng. The result from the experiment did not indicate any significant difference between upland rice yields obtained from tillage or no tillage practices in either location. However, there was a highly significant difference (P<0.01) in yields between the five rice varieties under both soil conditions at both locations. çChaomadé rice variety gave the highest yield in both treatments and both locations. The results of the study also suggest that the current dibble stick technique of planting did not cause soil compaction serious enough to decrease yield of upland rice.