Soil stabilisation by water repellency under no-till management for soils with contrasting mineralogy and carbon quality

Abstract

No-till soil management is common around the globe, but the impacts on soil structural quality varies depending on cropping practice and inherent soil properties. This study explored water repellency as a driver of soil stabilization, as affected by soil mineralogy, granulometry and organic carbon quality in three Mollisols and one Vertisol under no-till management and with different levels of cropping intensity. The studied soils were located along a west-east textural gradient in the northern part of the Pampean region of Argentina. Cropping intensity treatments evaluated in each one of the soils were: Poor Agricultural Practices (PAP) close to a monoculture, Good Agricultural Practices (GAP) involving a diverse crop rotation and more targeted inputs, and the soil in the surrounding natural environment (NE) as a reference. NE had the greatest aggregate stability (MWD) of all cropping intensities, with GAP being more stable than PAP for Mollisols and PAP being greater than GAP for the Vertisol. This trend matched the Repellency Index (R index), with greater R index associated with greater MWD, including the difference between the Mollisols and Vertisol. However, the persistence of water repellency, measured by the Water Drop Penetration Time (WDPT) test followed the trend NE > GAP > PAP regardless of soil type. The increases in R index and MWD were related to higher intensification as measured by the Crop Sequence Index, and decreased with greater soybean occurrence in the sequence. Both WDPT and R index were closely related to aggregate stability, particularly for Mollisols. These results highlight the importance of considering the inherent soil characteristics texture and mineralogy to understand aggregate stabilization mediated by water repellency. Good correlations between soil water repellency, organic carbon fractions and aggregate stability were found. Under no-till, crop rotations can be altered to increase soil stability by inducing greater water repellency in the soils. The findings suggest that water repellency is a major property influencing soil structure stabilization, thus providing a useful quality indicator.

Prokaryotic Community Composition and Extracellular Polymeric Substances Affect Soil Microaggregation in Carbonate Containing Semiarid Grasslands

“…In general, hydrophobic rather than hydrophilic components of OM are assumed to improve aggregate stability (Piccolo and Mbagwu, 1999;Chenu and Cosentino, 2011;Kraemer et al, 2019). Especially in the case of water-stable microaggregates (as in our study), a relation between the wettability and microaggregation could be expected.…”

“…Flemming and Wuertz (2019) estimated that about 80% of soil prokaryotes live in biofilms. Furthermore, the nature of the binding factors plays an important role in the overall aggregate stability strength, since hydrophobic rather than hydrophilic components of OM improve aggregate stability (Piccolo and Mbagwu, 1999;Chenu and Cosentino, 2011;Kraemer et al, 2019). By the properties of the bonds between the units of an aggregate, it can be assumed that with decreasing diameter of the aggregates, the stability increases.…”

Factors governing soil water repellency under tillage management: The role of pore structure and hydrophobic substances

“…Hallett et al (2001) and Cosentino et al (2010) found that SWR was mainly controlled by hydrophobic compounds rather than pore structure when they used ethanol sorptivity as an indirect indicator of pore structure. However, other researchers have reported that SWR, when measured by the WDPT method, was more affected by pore structure than hydrophobicity (Behrends et al, 2019). However, these conclusions were not based on the direct measurement of pore structure and their results were only obtained from indirect indicators associated with pore structure.…”

“…Microbial biomass carbon (MBC) can have a more useful and sensitive response to soil processes than the SOC (Sparling, 1992). It has been previously shown that there is a positive correlation between SWR and soluble carbohydrates linked to biological activity in soil (Behrends et al, 2019;Wander, 2004). Seaton et al (2019) also found that soil microbial community composition strongly influenced SWR that could be induced by microbes in a shorter time.…”

“…In addition, the porosity of same sized pores has different impacts on hydraulic conductivity under different degrees of SWR (Nyman, Sheridan, & Lane, 2010), which suggests that SWR behaviour can be influenced by pore-size distribution. Behrends et al (2019) used the water drop penetration time (WDPT) method to establish that the time needed for a single water drop to infiltrate a soil sample, which shows the degree of SWR, was controlled by pore structure as well as hydrophobic substances.…”