Contrasting Effects of Sorghum Biochars and Sorghum Residues on Soil Chemical Changes of Coastal Plains Ultisols With Winter Wheat

Although most soil properties were improved following application of crop residues and/or pyrolyzed crop residues, there is still a need to pursue additional research that will improve our understanding of the impact of soil fertility enhancement because the effect could vary greatly between uncharred sorghum (Sorghum bicolor L.) residues and pyrolyzed sorghum residues (SR). We hypothesized that sorghum biochars (SB) would deliver more significant impact on soil chemical changes than SR. The objective of this study was to evaluate the contrasting effects of SR and SB with or without supplemental inorganic P on soil chemical changes of Coastal Plains Ultisols with winter wheat. The application rates for SR and SB based on 13.5 Mg ha−1 yield goal for wheat were 13,000 and 5,200 kg · ha−1, respectively. Inorganic P was added at the rate of 40 kg P · ha−1. Our results fully support our hypothesis that SB would deliver more positive effect on the changes of soil chemical properties than the SR. Most of the chemical properties of soils were significantly affected by sorghum treatments (SB + SR) and also varied widely between soil types. Overall, application of SB had small, but significant effects on soil pH, soil electrical conductivity, total carbon, and total nitrogen. Quite notably was the significant difference of these soil properties between soil types. Other aspects of soil chemical changes including extractable P, K, Ca, Mg, Al, and Fe were significantly affected by sorghum treatments. Our results have demonstrated widely differing and contrasting effects between SB and SR on changes in soil chemical properties of Coastal Plains Ultisols.