Simulation and verification of soil moisture of root distribution functions for alfalfa

Root distribution has a significant impact on soil moisture and nutrient uptake. It is time and effort consuming to measure root distribution, but it is easy to study root distribution by empirical functions. Soil column experiments in field were conducted to measure alfalfa root distribution. Empirical root distribution functions were compared with measured data, and they were respectively incorporated in the Hydrus-1D software to simulate soil water movement. Consequently, the applicability of empirical root distribution functions and the effect of empirical root distribution functions on soil moisture dynamic change were verified and analyzed by comparing of measured and simulated values of soil moisture. The results showed that the simulated values of root density by functions of fitting root distribution, Prasad distribution and Hoffman and van Genuchten distribution were coincide well with measured values below 36 cm. The value of Raats root distribution was different with other distribution function values and the measured values. Different distribution functions resulted in nearly identical soil moisture, and the average relative root mean square error were below 3.5%. Raats root distribution, Prasad distribution and Hoffman and van Genuchten distribution all can describe the practical root distribution of alfalfa under non-stress growth condition