Use of Physical Properties to Predict the Effects of Tillage Practices on Organic Matter Dynamics in Three Illinois Soils

Abstract

This work builds on a previous study of long-term tillage trials that found use of no-tillage (NT) practices increased soil organic carbon (SOC) sequestration at Monmouth, IL (silt loam soil) by increasing the soil's protective capacity, but did not alter SOC storage in DeKalb, IL (silty clay loam), where higher clay contents provided a protective capacity not affected by tillage. The least limiting water range (LLWR), a multi-factor index of structural quality, predicted observed soil CO2 efflux patterns. Here we consider whether LLWR can predict sequestration trends at a third site, Perry, IL (silt loam soil) where SOC content is lower and bulk density is higher than in previously considered sites, and determine whether pore size characteristics can help explain the influence use of NT practices has had on SOC sequestration at all three locations. At Perry, LLWR was again related with differences in specific soil organic carbon mineralization rates (RESPsp) (2000-2001). Reduced RESPsp rates explain increases in SOC storage under NT management observed only after 17 yr. Trends in RESPsp suggest use of NT practices only enhance physical protection of SOC where soil bulk density is relatively high (approximately 1.4 g cm(-3)). In those soils (Monmouth and Perry), use of NT management reduced the volume of small macropores (15-150 microm) thought to be important for microbial activity. Physical properties appear to determine whether or not use of NT practices will enhance C storage by increasing physical protection of SOC. By refining the functions used to compute the LLWR and our understanding of the interactions between management, pore structure, and SOC mineralization, we should be able to predict the influence of tillage practices on SOC sequestration.

Conservation Agriculture and Soil Carbon Sequestration: Between Myth and Farmer Reality

“…Yoo et al (2006) concluded that the use of zero tillage practices only enhances physical protection of SOC where soil bulk density is relatively high (approximately 1.4 g cm −3 ) and when the use of zero tillage management reduces the volume of small macropores (15-150 µm), thought to be important for microbial activity. This notion is supported by the findings of Strong et al (2004) who observed rapid decomposition of C in the pores with neck diameters between 15 and 60 µm.…”

“…There may be a threshold value for bulk density that must be exceeded before pore-dependent processes are constrained and protect SOC. By refining our understanding of the interactions between management, pore structure and SOC mineralization, we should be able to predict the influence of tillage practices on SOC sequestration (Yoo et al, 2006).…”

Root Parameters Show How Management Alters Resource Distribution and Soil Quality in Conventional and Low-Input Cropping Systems in Central Iowa

“…The effect of soil strength on root distribution has been observed to be stronger for grass species than for tap-rooted species [34]. Lack of oxygen may also limit root growth, particularly in fine-textured soils [35]. If root growth is limited by low oxygen, RLDs could be expected to be low in areas where the percentage of water-filled pore space (%WFPS) exceeds 60% [36].…”

Soil water availability for plants as quantified by conventional available water, least limiting water range and integral water capacity

“…da Silva and Kay (1997) showed that plant growth is more vulnerable to environmental conditions (such as climate and rainfall) in soils which have a narrow LLWR than those soils, which have a wide LLWR. Yoo et al (2006) consider whether LLWR and pore size characteristics could explain the influence of notill practices on the increase of soil organic carbon sequestration. They concluded that pore size distribution may provide useful information about the mechanistic relationship between soil structure and microbial activity but LLWR is easier to determine than the pore size distribution as long as appropriate pedotransfer functions, which rely on soil water retention and mechanical resistance curves, are available.…”