Least Limiting Water Range and Compressibility of the Soil in Irrigated Organic Agroecosystems.

The physical quality of the soil is essential to the sustainability of irrigated agricultural systems. This study aimed to evaluate the least limiting water range and compressibility of the soil in and between rows of irrigated acerola, in areas with 1 (A1), 6 (A6) and 10 (A10) years of organic cultivation. The following were evaluated at depths of 0.00-0.10 m and 0.20-0.30 m: degree of compaction (DC), maximum density (D_Smax), critical moisture (U_crít), least limiting water range (LLWR), preconsolidation pressure (σ_p), compression index (Cc), total organic carbon (TOC) and the stocks of light organic matter (E_lom) and of light organic matter carbon (E_Clom). The LLWR of the areas showed that plant growth was limited mainly by the resistance of the soil to penetration. The rows under A1 and A6 showed higher values for LLWR and Cc (p< 0.05) than those between the rows, which may be linked to the higher values for TOC (A1 p< 0.10, A6 p< 0.05) and to the absence of traffic in the rows. Under A10, the areas between the rows showed a greater LLWR than under A1 and A6. This result suggests that the use of micro-sprinklers has beneficial effects on the structural quality of the soil. The σ_p was similar in and between the rows of crops. In the top soil, A1 displayed a higher value for DC than A6 and A10 (p<0.15), suggesting that soil compaction was promoted by the type of soil management and irrigation adopted. The LLWR was more sensitive in detecting changes in soil structure than DC or σ_p.