Location: Dale Bumpers Small Farms Research CenterTitle: Reevaluating the effects of soil organic matter and other properties on available water-holding capacity using the National Cooperative Soil Survey Characterization Database
|LIBOHOVA, ZAMIR - Natural Resources Conservation Service (NRCS, USDA)|
|SEYBOLD, CATHY - Natural Resources Conservation Service (NRCS, USDA)|
|WYSOCKI, DOUG - Natural Resources Conservation Service (NRCS, USDA)|
|WILL, SKYE - Natural Resources Conservation Service (NRCS, USDA)|
|SCHOENBERGER, PHILIP - Natural Resources Conservation Service (NRCS, USDA)|
|WILLIAMS, CANDISS - Natural Resources Conservation Service (NRCS, USDA)|
|LINDBO, DAVID - Natural Resources Conservation Service (NRCS, USDA)|
|STOTT, DIANE - Natural Resources Conservation Service (NRCS, USDA)|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2018
Publication Date: 7/1/2018
Citation: Libohova, Z., Seybold, C., Wysocki, D., Will, S., Schoenberger, P., Williams, C., Lindbo, D., Stott, D., Owens, P.R. 2018. Reevaluating the effects of soil organic matter and other properties on available water-holding capacity using the National Cooperative Soil Survey Characterization Database. Journal of Soil and Water Conservation. 73(4):411-421. https://doi.org/10.2489/jswc.73.4.411.
Interpretive Summary: This article describes the interaction of soil properties influence available water holding capicity in soils. The database at the National Soil Survey Center was utilized to examine the relationship between sand, silt, clay and organic matter on plant available water. The most important finding is that the data indicates that only a small amount of variability in available water be attributed to increases in organic matter. The single most important soil property contributing to available water is the total silt content. The role of organic matter in contributing to available water is complex as there are instances where organic matter contributes to the available water and instances where apparently it does not, and the latter predominates The role of soil organic matter in changes to the available water showed complex interactions with clay minerology, texture, bulk density and structure. An increase of 1% organic matter can increase, on average, the available water by about 1.5% depending on texture, clay mineralogy, structure and organic matter amount. The increase of available water was more pronounced for sandy soils than that for clayey and silt loam soils. Clay mineralogy can affect the influence of organic matter on the available water. The increasing organic matter may influence increasing inflitration which can decrease erosion, increase water entering the soil and generally improve soil conditions; however, the soil organic matter increase do not result in significant increases in available water holding capacity.
Technical Abstract: Soil organic matter (SOM) has been known to hold water and be an important factor in contributing to the available water-holding capacity (AWHC). Recently, however, there have been overestimates of this amount. The objective of this research was to reevaluate the relative contribution of SOM to AWHC as influenced by soil physical properties (particle size, texture, and bulk density) and mineralogy using the National Cooperative Soil Survey (NCSS) Soil Characterization Database and also to elucidate on the theoretical capacity of SOM to hold water. Silt content had the greatest correlation with AWHC (r = 0.56). AWHC increased with decreasing soil bulk density (r = -0.34), but the relationship was highly variable depending on SOM and soil texture. Soil organic matter was weakly correlated with AWHC for samples between 0% and 8% SOM (r = 0.27) but moderately correlated (r = 0.62) for all samples (0% to 100% SOM). The increase of AWHC was more pronounced for sandy soils than for silty clay loam and silt loam soils. For soils with clay contents greater than 40%, the correlation varied by minerology class: mixed (r = 0.24), smectitic (r = 0.08), and kaolinitic (r = 0.49). In general, a 1% increase in SOM content increased AWHC, on average, up to 1.5% times its weight, depending on soil texture and clay mineralogy. These values were consistent with the theoretical calculations that showed that the potential AWHC increase (on a volumetric basis) from a unit increase in SOM (% weight) is about 1.5% to 1.7% for the 0% to 8% SOM range. This equates to 10,800 L of water for each additional 1% increase in SOM (up to 8% SOM) for a layer thickness of 15 cm covering 0.4 ha area (an acre furrow slice).