Least limiting water range as affected by soil texture and cropping system

• LLWR tested on two soils under long-term cultivation with either wheat or alfalfa.
• LLWR was smaller for sandy loam under wheat and higher for clay loam under alfalfa.
• Management modified unfavorable effects of soil texture by affecting soil porosity.
• LLWR was related to bulk density, percentage of clay, calcium carbonate and OC contents.
• LLWR could act as an indicator of the impact of management on soil conditions.

In this study the least limiting water range (LLWR) and associated measurements (water content at field capacity, θFC, wilting point, θPWP, air filled porosity, θAFP, and mechanical resistance, θSMR) were tested on two soils of clay loam (CL) and sandy loam (SL), each under long-term cultivation with either wheat (Triticum aestivum L.) or alfalfa (Medicago sativa). Water content at field capacity (θFC) and wilting point (θPWP) decreased slightly with an increase in bulk density (Db) in clay loam soils under wheat and alfalfa, whereas in sandy loam soils under the same cultivation, both values of θFC and θPWP strongly increased by increments of Db. The variation of LLWR was negatively related to Db in clay loam soils under wheat and alfalfa cultivation. The LLWR increased up to Db, equal to 1.56 Mg m−3 (when θFC = θ10kPa) and to 1.60 Mg m−3 (when θFC = θ33kPa) in sandy loam under alfalfa, and 1.42 Mg m−3 (both values of θFC) in sandy loam under wheat; LLWR then declined sharply with increasing Db. The highest value of LLWR was observed in the ranges of 0.034–0.167 cm3 cm−3 (when θFC = θ10kPa) and of 0.034–0.119 cm3 cm−3 (when θFC = θ33kPa) in clay loam under wheat. The lowest value of LLWR was observed in between 0.137 and 0.151 cm3 cm−3 (when θFC = θ10kPa) and between 0.087 and 0.111 cm3 cm−3 (when θFC = θ33kPa) in sandy loam under wheat. Linear regressions (Stepwise) showed that LLWR (when θFC = θ10kPa) was related to bulk density, clay, calcium carbonate (CaCO3) and organic carbon (OC) contents (r2 = 0.79). Considering θFC = θ33kPa, LLWR was related to bulk density, clay and OC contents (r2 = 0.48)