Drainage of a Tropaqualf Before and After Water Extraction by a Crop

Abstract

To improve production of crops planted after lowland rice (Oryza sativa L.) in monosoonal Asia, there is a need to understand more clearly the drainage pattern during the transition from the wet to the dry season. For crops of 75 to 80 d maturity, the top 750 mm of soil contains the bulk of the root system. This study determined the flux of water across the 750‐mm plane and the water table recession patterns during the transition from wet to dry season and again after a crop had removed water from the soil. The study was conducted in three phases on a 9‐m by 9‐m plot of an Aeric Tropaqualfs. In the first phase, the soil was field saturated, covered with plastic sheeting, and drained for 30 d. In the second phase, a cowpea (Vigna unguiculata L. Walp) — sorghum (Sorghum bicolor L. Moench) intercrop was grown for 42 d. In the third phase, 22 mm of water was applied and soil was again covered and drained for 15 d. Volumetric water changes were determined by neutron scattering at 150‐, 300‐, 600‐, 900‐ and 1200‐mm depths. Tensiometers were placed at the same depths. The plot was surrounded by flow barriers to a 750‐mm depth. Drainage through the 750‐mm plane during the first phase amounted to only 11 mm. A perched water table formed in and above the B horizon at 600 mm. The ground water table receded at 30 mm d−1 after it appeared below the perched water table on day 10. During the second phase roots penetrated at about 25 mm d−1 suggesting that the initial high water content was not a major impediment to root development. After a 22‐mm irrigation, the drainage rate during the third phase was 1.2 mm d−1, with drainage apparently coming both from applied water and water remaining in the profile prior to irrigation. The results suggest both opportunities and problems for using soil water remaining after rice harvest during the transition from wet to dry season.

Zero Flux Plane Recession under Monocropped and Intercropped Cowpea and Sorghum

“…The average zero flux plane penetration rates were 24 mm d-1 for the cowpt:a monocrop and 22 mm d-1 for the intercrop. The intercrop rate was 20o/o slower than that reported by Klodpeng and Morris (1984) for a cowpea-sorghum :intercrop grown in similar atmospheric and soil conditions. Plant densities of the intercrop grown by Klodpeng and Morris were about double those used in this study.…”

“…1. For a similar soil in an adjacent field, Klodpeng and Morris ( 1984) reported saturated hydraulic conductivities of 1.5 to 1. 7 mm d-1 in horizons above 0.56 m. Saturated hydraulic conductivities of the horizons below 0.56 m were 4 to 6 times saturated hydraulic conductivities of overlying horizons.…”

“…Unless used by an upland crop or weeds, water remaining in the soil profile at rice harvest continues to drain even when the true water table has fallen below 1 m. Klodpeng and Morris (1984) observed that internal drainage from an unplanted paddy soil covered to prevent evaporation was less than 0.5 mm d-1 during the wet season when the water table was near the soil surface. A cowpea-sorghum intercrop grew vig-oro~sly when planted after removal of the evaporation bamer.…”

Effect of Seeding Depth and Soil Mulching on Growth and Yield of Peanut Grown after Rice in the Post-Monsoon Season of Northeastern Thailand

“…The productivity of these crops depends largely on successful crop establishment and the availability of soil water (Zandstra, 1982) . The amount of water potentially available to dryland crops depends on both the amount of water stored and addition from rainfall or upward movement of water from a shallow water table (Angus et al, 1983;Klodpeng and Morris, 1984). Several studies have shown that dryland crops such as mungbean, cowpea, soybean and peanut grown after rice in Northeastern Thailand produced a poor yield, because the crops experience water stress during the seed-filling phase (Polthanee and Marten, 1988;Polthanee, 1998).…”

Growth of Soyabean (Glycine Max) and Mungbean (Vigna Radiata) in the Post-Monsoon Season after Upland Rice

“…Several studies have shown that dryland crops grown after rice can extract substantial amounts of stored soil water (e.g. Angus et al, 1983;Klodpeng and Morris, 1984).…”