Tillage Effects on Evapotranspiration of Three Different Paddy Soils in Spring Season as Tested by Monolithic Weighable Lysimeters

Abstract

This study was conducted to evaluate the effect of tillage in spring season before rice cultivation on evapotranspiration (ET) of three different paddy soils. Precision weighing lysimeters, filled with three undisturbed paddy soils, were used, and each texture was silty clay loam, loam, and sandy loam. For tillage treatments, the hand tillage (HT) was conducted to a depth of 8 cm by using a spatula with a 5 cm width on Mar. 8, 2016. The no-tillage (NT) treatments were continuously kept as no-tillage conditions during the study period. In 2016 spring of this experimental field, two contrary periods in weather condition, dry period from Mar. 8 to Apr. 5 and rainy period from Apr. 6 to Apr. 30, were used to analyze the effects of tillage on soil water status and evapotranspiration in paddy soils. In dry period with rare rainfall, HT treatment had lower evapotranspiration loss than NT treatment except sandy loam soil. Especially, the soil water tension difference over the dry period between HT and NT was highest in silty clay loam soils, probably due to transection of crack by tillage. On the other hand, the significant tillage effect on ET reduction in all soils over total period, dry and rainy periods, was not observed with high flucturation of weed biomass. This is probably not only because frequent rainfall events in rainy period could cause the reconnection of capillaries through water dispersion of clods, but also because nutrient mineralization at rewetting after surface tillage could promote ET through better weed growth. Nevertheless, in drought condition, tillage operation in early spring could be useful to decease water loss by evapotranspiration. Periodically cummulative evapotranspiration amounts during spring (Mar. 8, 2016 - Apr. 30, 2016) periods for NT† and HT‡ treatments under the silty clay loam, loam, and sandy loam soils. Period Silty clay loam Loam Sandy loam NT HT NT HT NT HT ------------------------------------ mm ------------------------------------ Total 112.1ab¶ 92.6b 136.7a 119.2ab 111.6ab 114.4ab Dry (Mar. 8 - Apr. 5) 52.5de 32.9f 59.6d 44.6e 53.3de 43.2e Rainy (Apr. 6 - Apr. 30) 59.6g 59.6g 77.2g 74.6g 58.3g 71.2g †NT and ‡HT mean no-tillage and hand tillage practices, respectively, and ¶the same letter denotes a statistically insignificant difference above p-value > 0.05 from Duncan's Multiple Range test for every horizontal line.