Subsoil compaction to improve water use efficiency and yields of rainfed lowland rice in coarse-textured soils

Abstract

Field experiments during the 1992 and 1993 wet seasons examined in situ water conservation in rainfed lowland rice ( Oryza sativa L.) grown on a loamy sand by comparing subsoil compaction (C) with puddling (PUD), a plastic sheet barrier at 40 cm depth (PLS), and dry tillage (DT). Soil was compacted with six (C6) or nine (C9) passes of a 12-ton road roller over the soil surface with (+V) or without (- V) roller vibration. After compaction, soil was tilled to 20 cm depth. All plots except DT were puddled manually to 15 cm depth. Rice seedlings (Cultivar KDML105) were transplanted in all plots. Degree and depth of compaction increased with number of passes and with vibration of the roller. Treatment C9 + V compacted soil to at least 60 cm depth. Percolation decreased from 11.8 mm d −1 in DT and 6.3 mm d −1 in PUD plots to 1.4 mm d −1 in C9 + V plots. Compaction increased total days with surface water accumulation from 44 days in DT and 68 days in PUD plots to 90 days in C9 + V. Rice in plots with subsoil compaction had nearly twice the root length and root mass densities in the 0–20 cm soil layer and significantly increased shoot growth as compared with rice in DT and PUD plots. As compared with PUD, the standard tillage practice of farmers, treatment C9 + V increased grain yield by 1.48 Mg ha −1 (59%) in 1992 and by 0.98 Mg ha −1 (88%) in 1993, with 1.6 times greater water use efficiency (WUE) in 1992 and 1.9 times greater WUE in 1993. Treatment PLS yielded more grain than PUD, but less than C9 + V. We conclude that subsoil compaction technology is applicable at a field scale for rainfed rice grown in coarse-textured soils.