Post-rice soybeans and peanuts differ in performance, water use, and water-use efficiency in the rainfed lowlands

Abstract

This study examined patterns of water use and water-use efficiency in soybeans (Glycine max) and peanuts (Arachis hypogaea), for which data are rare, to assess their suitability as post-rice (Oryza sativa L.) crops in the rainfed lowlands. A field experiment was conducted at Pakse in southern Lao PDR, comprising two irrigation regimes (weekly and as needed), three surface mulch treatments (nil, straw, and plastic), and two species (soybeans, peanuts), in a split–split design with three replicates. Volumetric soil water content was measured using time-domain reflectometry. Water deficit was more severe under as needed irrigation, Nil cover, in soybeans, and late in the life cycle. Water use was highest in soybeans under nil cover and weekly irrigation (432 mm) and was lowest in peanuts under plastic cover and as needed irrigation (225 mm). Soybeans were responsive in plant height (41.5–62.7 cm), while peanuts were responsive in grain yield (1.05–1.81 Mg ha⁻¹). Water-use efficiency was lowest in soybeans under nil cover and weekly irrigation (2.48 kg ha⁻¹ mm⁻¹), and highest in peanuts under plastic cover and as needed irrigation (8.04 kg ha⁻¹ mm⁻¹). The paper concludes that peanuts should have a role as a post-rice crop in the rainfed lowlands, with access to supplementary irrigation.