The Spatial Variability of Upper and Lower Limits of Available Moisture Content as Affected by Different Tillage Systems

Abstract

To evaluate the effect of conventional tillage (CT) and zero tillage (NT) on the extent of available moisture; field capacity (FC) and permanent wilting point (PWP) and characterize the spatial variations of these soil properties, a field experiment was conducted at Al-Mishkhab Rice Research Station at Al-Najaf province during 2019-2020 rice season. The experimental site was located between N 0^o17^´4.5075 and E 40^o54^´29.6959. The moisture contents between FC and PWP designate available moisture profile and are determinants of crop production. Spatial variability of soil physical properties are studied, using geological statistics. The upper limit of moisture content at FC gave the highest C.V of the CT after harvest, which was 15.42% compared with the NT before planting, which gave the lowest CV of 8.86%, The moisture content at PWP gave the highest C.V of 34.94% for the NT soil before planting compared with the CT before planting, which gave the lowest CV of 28.13%. Strong spatial dependences of FC and PWP were found in the field. The application of Geostatistics methods with respect to statistical models showed that the spherical outperformed all other models (76.67%), Gaussian model (20.00%) and exponential model (3.33%).