摘要：

Biochar may improve soil physical properties for crop growth, but multiyear, multicrop field studies are lacking. To determine the effects of biochar on soil physical properties, we applied 0, 10, 20, 40, and 80 Mg ha<sup xmlns:mrws="http://webservices.ovid.com/mrws/1.0">−1</sup> biochar with/without NPK fertilizer to the surface 15 cm of 1 × 1 m<sup xmlns:mrws="http://webservices.ovid.com/mrws/1.0">2</sup> plots in a single association of fine-loamy, siliceous, subactive, thermic Oxyaquic and Aquic Paleudults under a 2-year corn-winter wheat–double-crop soybean rotation. After 3 years, we sampled soil to 7.6 cm, measured bulk density and water retention, and then derived pore-size distribution and related physical and water retention model parameters. Fertilizer had little to no effect. Among the statistically significant results, biochar increased structural porosity (3- to 59-μm effective pore diameter [EPD]) but neither matrix- (0.2- to 3-μm EPD) nor macro (EPD >59 μm) porosity . Biochar ≥40 Mg ha<sup xmlns:mrws="http://webservices.ovid.com/mrws/1.0">−1</sup> decreased bulk density 16%; 80 Mg ha<sup xmlns:mrws="http://webservices.ovid.com/mrws/1.0">−1</sup> increased total porosity 14%. However, it also increased water content at −1,500 kPa 22.5%. Biochar ≥40 Mg ha<sup xmlns:mrws="http://webservices.ovid.com/mrws/1.0">−1</sup> increased the drained upper limit (DUL) by 15%; relative field capacity, 3%; and total and structural plant-available water (PAW: held between the DUL and −1,500 kPa), 7 and 18%, respectively. Increases were greatest at −10 kPa and least at −33 kPa. At −10 kPa, 80 Mg ha<sup xmlns:mrws="http://webservices.ovid.com/mrws/1.0">−1</sup> biochar increased total PAW 4.0-mm equivalent depth compared with 5.7 mm for structural PAW, approximately 0.5-day demand for actively growing corn. Modeled saturated water content increased with total porosity . Biochar improved plant-soil-water relations, but required high rates.

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