Assessment of evapotranspiration and water balance during winter onion and Italian Ryegrass cultivations in monolithic weighable lysimeters with sandy loam texture

Assessment of water requirement through water balance analysis is important for efficient irrigation for crop cultivation.However, most relevant studies have been conducted for the summer crops, thus relevant information on the winter crops is rare.In this study, water balance was analyzed and water requirement was estimated for the winter crops of paddy (Italian ryegrass, Lolium multiflorum Lam.) and upland (onion, Allium cepa L.) using lysimeter systems from October 2023 to June 2024.During the study period, the available precipitation was 539.4 mm for paddy and 609.3 mm for upland, respectively.Drainage through percolation was higher for upland than paddy soils by 200 mm.This is because upland soils had more macro-pore and thus soil water retention capacity is lower and drainage rate is faster compared to paddy soils.The evapotranspiration was higher for paddy than for uplands by 60 mm due to 5-foild higher crop biomass of Italian ryegrass than that of onion.Runoff was 92 mm for paddy, whereas no runoff was in upland, resulting in more negative water balance for paddy (-178.2mm) compared to that for upland (-142.2mm).The water requirement was estimated to be 308.5 mm and 287.2 mm for Italian ryegrass and onion, respectively.In this study, the water requirement was lower than the available precipitation during the experimental period, thus precipitation was not limited.However, the water requirement might be affected by the initial soil water content and weather conditions; therefore, it is necessary to design irrigation scheme by considering both soil water characteristics and the weather conditions.