CONSTRUCTION OF PEDOTRANSFER FUNCTION FOR PADDY SOIL BULK DENSITY BASED ON DIFFERENT GENETIC HORIZON

Bulk density (BD) is a key soil indicator for assessing agricultural sustainability; However, missing data are common due to the time-consuming, labor-intensive sampling, leading to frequent data gaps.Therefore, the objective of this study was to construct the pedotransfer function (PTF) based on other easily accessible properties of paddy soil to predict paddy soil bulk density in different occurrence horizons in Hunan.This study constructs the PTF for the whole profile, the plough horizon (Ap1), the plow pan (Ap2), and the underlying horizon (B horizon) using data on organic carbon (OC), sand, silt, and clay from 343 genetic horizons across 61 paddy soil profiles in Hunan Province.There were significant differences in soil BD and OC contents among different horizons, and also certain differences exist in soil particle compositions among different horizons, which led to the differences in factors affecting the BD among different horizons.BDs of all genetic horizons had moderate negative correlation with OC content (R = -0.425,-0.564, and -0.509, respectively, p < 0.01), while BD of B horizons had weak correlation with the content of sands, silts and clays (R = 0.292, -0.245, and -0.195, respectively, p < 0.01).PTFs of BD with the highest accuracy were in different forms for different horizons, in which the cubic function of OC was optimal for Ap1, BDAp1 = 0.915 + 0.048OC-0.003OC 2+ 3.87010-5OC 3 , the linear regression function of OC, silt and clay for Ap2, BDAp2 = 1.483-0.014OC+ 1.61510 -5 Silt + 9.66010 -5 Clay, and growth function of OC for B horizon, BDB = e (0.455-0.01OC) .