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Biochar, Manure, and Sawdust Alter Long‐Term Water Retention Dynamics in Degraded Soil
Author(s) -
Lentz Rodrick D.,
Ippolito James A.,
Lehrsch Gary A.
Publication year - 2019
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2019.04.0115
Subject(s) - biochar , manure , loam , sawdust , amendment , soil water , agronomy , chemistry , environmental science , water retention , soil conditioner , soil science , pyrolysis , organic chemistry , political science , law , biology
Core Ideas Biochar's long‐term water retention effects on soil are poorly understood. The temporal effects of biochar, manure, and sawdust on water differed. Biochar and nonpyrolized organics all had long‐lasting effects on water. Water retention dynamics were influenced by the repellency and particle size of the material. Water retention in the first or second years may not reflect the material's long‐term potential. Biochars are porous but more recalcitrant than nonpyrolyzed organic materials, possibly causing more persistent alterations to soil water dynamics. In this 6‐yr outdoor study, we amended an irrigated calcareous silt loam with a single 1 or 2% dry weight application of hardwood biochar, manure, sawdust, or acidified sawdust; 1% biochar + 2% manure; or a control. Soil water retention and plant‐available water (PAW, g H 2 O per g dry soil) were measured in spring. Across all years, 1% biochar + 2% manure produced the greatest PAW (0.262), with PAW in the order: 1% biochar + 2% manure > 2% rates > 1% rates > control (0.222). In most years, the 2% treatments increased PAW relative to the control. The PAW ratios (treatment PAW/mean annual control PAW) for the 2% rates varied with amendment and year ( P < 0.0001): 2% manure peaked in Year 1, declining to a minimum in Year 3; the other 2% treatments were least in Year 1 and peaked between Years 3 and 5; 1% biochar + 2% manure consistently had a ratio near the maximum. Amendment effects on soil water retention were immediate but the peak benefits were delayed because of the differing hydrophobicity of the original materials and their particle sizes, where greater sizes slowed the removal of hydrophobic surface coatings. Biochar's effects on PAW were no more persistent than those of nonpyrolyzed amendments; however, adding biochar and manure had a mutually stabilizing effect, producing a large, more consistent retention increase over time.