Soil Structure Stability under Different Land Uses in Association with Polyacrylamide Effects

Abstract

Soil structural stability is a vital aspect of soil quality and functions, and of maintaining sustainable land management. The objective of this study was to compare the contribution of four long-term land-use systems (crop, bush, grass, and forest) coupled with anionic polyacrylamide (PAM = 0, 25, and 200 mg L−1) application on the structural stability of soils in three watersheds of Ethiopia varying in elevation. Effect of treatments on soil structural stability indices were assessed using the high energy moisture characteristic (HEMC, 0–50 hPa) method, which provides (i) water retention model parameters α and n, and (ii) soil structure index (SI). Soil (watershed), land use and PAM treatments had significant effects on the shape of the water retention curves (α, n) and SI, with diverse changes in the macropore sizes (60–250; >250 μm). Soil organic carbon (SOC) content and SI were strongly related to soil pH, CaCO3 soil type-clay mineralogy, exchangeable Ca2+, and Na+ (negatively). The order of soil SI (0.013–0.064 hPa−1) and SOC (1.4–8.1%) by land use was similar (forest > grass > bush > cropland). PAM effect on increasing soil SI (1.2–2.0 times), was inversely related to SOC content, being also pronounced in soils from watersheds of low (Vertisol) and medium (Luvisol) elevation, and the cropland soil from high (Acrisol) elevation. Treating cropland soils with a high PAM rate yielded greater SI (0.028–0.042 hPa−1) than untreated bush- and grassland soils (0.021–0.033 hPa−1). For sustainable management and faster improvement in soil physical quality, soil properties, and land-use history should be considered together with PAM application.

Determination of Mehlich 3 Extractable Elements with Visible and Near Infrared Spectroscopy in a Mountainous Agricultural Land, the Caucasus Mountains

“…The CaCO 3 content is largely variable (~84%), with a mean value of 2.91%. Such variability of SOC, clay, and CaCO 3 is attributed to the distribution of parent material depending on the topography, elevation (e.g., change in temperature, precipitation, pH by elevation), and dissolution and leaching processes [2,60]. Among the M3 elements, Ca, K, and P were largely variable (~50%), and others varied moderately (20-40%).…”

“…The results suggested that the M3 elements are related to the variation in soil type or texture and basic soil properties (mostly CaCO 3 and pH), along with coexisting metals that can reliably assist as predictive factors [61]. Moreover, the role of CaCO 3 (e.g., Ca and electrolyte sources, and pH modifier) on soil biogeochemistry is still overlooked in mountain soils and needs greater attention for the monitoring of land degradation and quality [2,60]. Thus, for the current study, the tested soil properties can be formally categorized into two groups.…”

“…Though soil organic matter and clay can act as buffers to resist pH variations, the leaching of free cations, oxides (e.g., Fe), and CaCO 3 , as well as the removal of cations (e.g., Ca, Mg and K) by plant uptake or harvesting, and the continuous formation of carbonic acid and application of acidic fertilizers can decrease soil pH, particularly in the higher elevated areas. This affects the soil buffering capacity and CEC, as well as the solubility and transport of M3 elements such as Fe, Mn, Cu, Zn, and P [2]. The variation in the land-use trend was also associated with the CEC/clay ratio of the samples (0.35-0.55 (63 samples) > 0.20-0.35 (40 samples) > 0.55-75 (12 samples)), revealing that mixed clay mineralogy (CEC/clay = 0.35-0.55) was the dominant parameter following illite + kaolinite mineralogy (CEC/clay = 0.20-0.35); samples with >0.55 (e.g., mixed clay mineralogy) were related to undisturbed areas with higher SOC or steep slope areas under shrub with the lowest clay content (<6%) as a result of clay loss or leaching.…”

“…Land-use intensification associated with land-use change and conventional agriculture significantly affects soil properties, quality, and ecosystem services, and hence comprises important aspects for future sustainable land management [1]. Therefore, monitoring soil properties in response to agricultural practices, land use, mining, and climate change is critical, especially in mountainous regions, where the soils are prone to severe land degradation processes, such as on-site and off-site impact, erosion, leaching clay particles and nutrients, and deterioration of water quality by chemicals [2]. Recent developments of site-specific crop management and precision agriculture have significantly heightened the need for more time-and cost-efficient techniques and methods of soil analyses [3].…”

Biodegradable Interpolycomplexes for Anti-Erosion Stabilization of Soil and Sand

“…5 mm in thickness, which prevents the removal of soil with water and wind [13]. For many years, polyacrylamide and copolymers of acrylamide with anionic monomers have been taken for soil stabilization [15][16][17][18].…”