Evaluation of spatial variability of the integral energy of plant available water and its influential properties in paddy soil

Plant Available Water is the main concept for describing the existing water content in a soil profile. Along with this concept, Integral Energy shows the energy required for plants to obtain a unit mass of soil water at a specific water content (such as PAW). The spatial variability of E-I in paddy soils and the factors affecting it have not been studied yet. To determine the spatial variability of Energy Integral and its influential properties, the number of 104 surface soil samples was collected from paddy fields located in different irrigation districts in Guilan Province. The physical and hydraulic properties were analyzed using Principal Component Analysis to derive the patterns of similarity within the variables, and then the spatial variability was mapped by implementation of a well-known geostatistical approach. The variogram and ordinary kriging estimator were used as function describing the degree of spatial dependence and interpolation, respectively. The results showed that the first four main components including (PC1, PC2, PC3, and PC4) describe about 83% of the variability of soil conditions. Stepwise analysis indicated that among the properties affecting the regional variability, bulk density and mean pore diameter have more effect on the spatial variability of Integral Energy. The structural properties such as pore-size distribution and bulk density had direct and significant effects on the variability of Integral Energy. The aforementioned findings emphasized the importance of effects of puddling on the conversion of macro-structural pores to micro-texture pores, more water retention in paddy soils, and the ability of rice plants to absorb soil water.