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Plant-available water capacity (PAWC) is a key indicator of soil physical quality and water delivery. Yet, research data on these parameters from long-term field studies are scant. This study evaluated the legacy effects of organic amendments and cover cropping on PAWC and pore structure in an Alfisol under a 27-year no-till (NT) system in central Ohio, USA. Four treatments were examined: weedy fallow (no input), cover crop (annual and perennial ryegrass, red fescue, and Kentucky bluegrass), compost (15.3 Mg/ha/yr), and cow manure (23.3 Mg/ha/yr), arranged in a randomized complete block design with four replications. Soil samples were collected in 2024 from four replicated plots per treatment at 0–20 cm and 20–40 cm depths. Volumetric water content was determined at eight matric suctions using tension tables and pressure plate extractors, with three cores per plot analyzed separately and averaged for plot-level analyses (n = 4 per treatment and depth). PAWC was calculated as the difference between water content at field capacity (pF 2.5) and permanent wilting point (pF 4.2). Manure-treated soils exhibited the highest PAWC in the 0–20 cm layer (5.14 ± 1.31 cm), while fallow had the highest in 20–40 cm (5.88 ± 1.04 cm). Water content at pF 1.8 ranged from 44.4 ± 0.8 % (manure) to 35.8 ± 2.0 % (cover crop) in surface soil. Fallow showed the steepest dθ/dpF curves (R² = 0.97–0.98, p 0.05), suggesting occluded mesoporosity. PAWC was strongly correlated with storage pores (R² = 0.94–0.92, p < 0.001). Structural equation modeling showed that storage pores mediate the effects of soil physical properties on PAWC, with bulk density acting as the primary constraint on water availability in surface soil. These findings highlight the legacy effects of organic inputs, particularly manure, on mesoporosity, PAWC, and soil hydrologic function under long-term NT management.
Munna et al. (Thu,) studied this question.