Rainwater Utilization Efficiency in Rain-Fed Lowland Rice

Abstract

Publisher Summary This chapter reviews the existing knowledge about improving rice yields per unit quantity of rainwater available. Nearly one-third of the world's lowland rice is rain fed; however, rain-fed rice comprises only one-fifth of the global rice produced. Insufficient or excess water is the major constraint in the production of rain-fed lowland rice. Coupled with this are problems of poor agronomic practices followed by farmers, socioeconomic constraints, and lack of technology suited to rain-fed lowlands. There are two aspects of increasing the efficiency of rainwater use under rain-fed situations: raising the yield of the rain-fed crop when rainfall is normal and preventing yield loss when rainfall is inadequate and drought occurs frequently. The technology for improving the efficiency of rainwater use in rain-fed lowlands aims at increasing in situ rainwater interception, soil infiltrability, and profile water storage; decreasing nonproductive water losses, such as percolation and seepage; collecting runoff water for providing supplementary irrigation at critical growth stages, if needed; and properly managing rice crops for efficient utilization of conserved soil moisture. These objectives can be achieved by proper soil, water, and crop management techniques and the chapter reviews some of the findings, possibilities, and challenges that are significant. Subsurface soil compaction before planting rice appears to be a practical way to decrease percolation losses and to improve profile water storage in coarse-textured soils. Water harvesting is an important component of rain-fed technology. Rainwater stored in suitable reservoirs can provide supplemental irrigation to rice during prolonged dry spells. The adoption of suitable agronomic practices is equally important in increasing the efficiency of rainwater use in growing rain-fed lowland rice. These include selection of crop variety, time of planting, plant populations, crop geometry, efficient fertilizer use, weed control, and insect control.