Lengths of Time of Rice Husk Biochar Incorporation before Planting Affect Soil Properties and Rice Yield

Abstract

A factor that causes inconsistencies in rice yield receiving biochar reported in the literature has been identified as the length of time after biochar incorporation into the soil prior to planting. There is limited information on the effect of the varying lengths of time on soil properties and rice growth. This study aimed to determine the effects of the length of time of incorporation of rice husk biochar (RHB) into an acidic paddy soil before rice transplanting on soil properties and rice yield. A greenhouse experiment was conducted using a highly weathered paddy soil subjected to incorporation periods of RHB at various lengths, including 0, 15, 30, and 60 days before rice transplanting (DBT). The RHB incorporation was under a soil moisture content of 70% of the soil water holding capacity. At harvest time (98 days after incorporation), increases in the length of RHB incorporation led to significantly higher Mg, Mn, and Si concentrations, but lower Ca and Fe concentrations in rice whole shoots. Increasing the length of RHB incorporation to 15, 30, and 60 DBT significantly decreased the total rice grain yield to 61.4 g hill−1, 62.5 g hill−1, and 54.4 g hill−1, respectively, compared to 76.0 g hill−1 found at 0 DBT. The depression of rice grain yield with increasing RHB incorporation periods was due to the antagonistic effects of Mg on Ca and Si on Fe. Immediate rice transplanting without a prior RHB incorporation period is recommended for its use as a soil amendment in acidic paddy soils.