Reevaluating the effects of soil organic matter and other properties on available water-holding capacity using the National Cooperative Soil Survey Characterization Database

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).

Modelling dynamic interactions between soil structure and the storage and turnover of soil organic matter

“…Changes in the SOM content may also affect the pore size distribution, although the magnitude of these effects across different ranges of pore diameter is still a matter of some controversy (e.g. Hudson, 1994;Rawls et al, 2003;Loveland and Webb, 2003;Minasny and McBratney 2018;Libohova et al, 2018).…”

Using woody organic matter amendments to increase water availability and jump‐start soil restoration of desertified grassland soils of Ningxia, China

“…Although the role of organic matter in soil water retention was historically contentious (Rawls et al, ), there has been growing acknowledgement over the past two decades of the benefits of organic soil amendments for increasing water retention (Libohova et al, ), along with soil fertility. Addition of livestock manure, compost, and other nutrient‐rich labile organic soil amendments has been used on farm fields for millennia; however, they break down rapidly and require frequent replenishment.…”

How specialized is a soil specialist? Early life history responses of a rare Eriogonum to site‐level variation in volcanic soils

“…In the greenhouse, attempting to water a variety of soil types evenly while maintaining adequate conditions for germination and seedling growth in all pots could have resulted in higher than optimal water content in poorer‐draining soils. Both organic matter and Mn have been shown to promote disease by either contributing to excessively moist conditions (Libohova et al, 2018; You et al, 2018) or by increasing virulence of pathogens under moist conditions (Falcon et al, 1984; Hasannejad et al, 2006; Orr and Nelson, 2018) and could have caused seed rot or failure of seedlings to emerge from the soil after germination. However, both organic matter and Mn are likely to be beneficial to plant growth in the native, drier environment of E. crosbyae (Marschner, 2011; Barker and Pilbeam, 2015).…”