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The use of recycled wastewater that has undergone various treatments (effluent) for irrigation is becoming one of the main means by which to mitigate the pressure on freshwater resources. The main objective of this study was to improve the basic understanding of the effects of irrigation with various effluents on the saturated hydraulic conductivity (Ks) of arid and semiarid soils. Clay, loamy, and sandy soils were sampled from experimental plots irrigated with freshwater or secondary effluent for >3 yr, and were used in column experiments. Leaching the loamy and clay soils with reverse osmosis (RO) effluent, which contained low electrolyte concentrations, led to clay swelling and dispersion and thereby decreased the soil Ks. In these soils, the high concentration of suspended solid particles and dissolved organic matter (DOM) in oxidation pond (OP) effluent caused significant pore clogging, which reduced the Ks. Leaching the soils with ultrafiltercd effluent maintained high Ks values due to the low concentration of suspended solid particles and DOM, their small sizes, and the relatively high electrical conductivity of this effluent. The relatively large average porr size in the sandy soil prevented pore clogging and Ks reduction when leached with RO and OP effluent. Secondary effluent irrigation increased the soil exchangeable Na percentage (ESP) compared with freshwater irrigation but did not change the organic matter content in the soil. In the loamy and clay soils, this higher ESP of the effluent-irrigated soils resulted in greater reductions in when leached with deionized water than occurred in freshwater-irrigated soils. [ABSTRACT FROM AUTHOR]

Increasing precipitation storage as plant-available soil water increases dryland crop yields on the semiarid southern Great Plains. The dominant soil in this region is a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll), which features dense subsoil layers that limit infiltration and root proliferation. Deep (∼0.7 m) plowing may eliminate these layers, but the duration of treatment efficacy must be sufficient to recoup costs. Our objective was to quantify the long-term effects of deep plowing on soil bulk density (BD), penetration resistance (PR), ponded infiltration, and crop yield. In fall 1971, paired 24- by 460-m level conservation bench terrace plots at the USDA-ARS Conservation and Production Research Laboratory, Bushland, TX (35°11′ N, 102°5′ W) were moldboard plowed to 0.7 m or untreated and, subsequently, maintained with conventional sweep tillage. Grain sorghum [Sorghum bicolor (L.) Moench] was grown intermittently during the next 34 yr for 15 paired yield comparisons. Compared with the control, deep plowing significantly decreased BD and PR and increased water infiltration. Long-term mean grain yield of 2.86 Mg ha-1 with deep plowing was greater (P < 0.05) than the 2.61 Mg ha-1 yield in control plots. Approximately 89% of the 15-yr 3.75 Mg ha-1 cumulative yield increase with deep plowing occurred during 4 yr with large early growing season rains. We attributed this yield increase with deep plowing to greater internal drainage that reduced crop injury during infrequent floods and not greater root growth through the dense subsoil. Thirty years after deep plowing, high water intake suggests that flow-limiting subsoil layers had not yet redeveloped. The sustained deep-plowing benefit extends the period to recoup the 1971 plowing costs of US$160 ha-1. [ABSTRACT FROM AUTHOR]