Management of cracked soils for water saving during land preparation for rice cultivation

High water loss Juring land preparation of soils For rice (Oryza sativa L.) production results. from bypass flow through cracks. It was hypothesized t hat the losses can be reduced by measures that minimize crack development d uring the soil drying period or impede the now of water through these crack s. The effect of straw mulching and shallow surface tillage on crack format ion during the fellow period, and on water flow components during land prep aration was investigated in field experiments on an Epiaqualf and a Pellust ert in the Philippines. Cracks did not completely close upon rewetting, res ulting in high loss (152-235 mm of water) during land preparation of the co ntrol (i.e. no soil management treatment) plots. Straw mulching helped cons erve moisture in the soil profile, and reduced the mean crack width by 32% of the control. Mulching did not significantly reduce mean crack depth and the amount of water used in land preparation. Shallow tillage formed small soil aggregates which made the crack water now discontinuous and impeded gr oundwater recharge from the water flow through cracks, reduced total water input for land preparation by 31-34%, equivalent to about 120 mm of water. The average surface irrigation water flow advanced faster and less time was needed for land preparation in the shallow tillage plots compared to the c ontrol. Shallow tillage offers a practical means for improving water-use ef ficiency of irrigation systems. In rainfed areas, it may facilitate early c rop establishment and, thus, reduce the risk of late-season drought. (C) 20 00 Elsevier Science B.V. All rights reserved.