2021-12-22_PERMIT FILE - C1981019 (2)

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5 5.0 DATA DISCUSSION Salt-affected soils develop from a wide range of factors including: soil type, field slope and drainage, irrigation system type and management, fertilizer and manuring practices, and other soil and water management practices. In Colorado, perhaps the most critical factor in predicting, managing, and reducing salt-affected soils is the quality of irrigation water being used. The primary effect of high EC water on crop productivity is the inability of the plant to compete with ions in the soil solution for water (physiological drought). The higher the EC, the less water is available to plants. Excessive soil salinity reduces the yield of many crops. This ranges from a slight crop loss to complete crop failure, depending on the type of crop and the severity of the salinity problem. Plants are usually most sensitive to salt during the emergence and early seedling stages. Tolerance usually increases as the crop develops. The salt tolerance values apply only from the late seedling stage through maturity, during the period of most rapid plant growth. Saline soils cannot be reclaimed by chemical amendments, conditioners or fertilizers. A field can only be reclaimed by removing salts from the plant root zone. In some cases, selecting salt-tolerant crops may be needed in addition to managing soils. Based on this assessment, salinity tolerances in the irrigated field subparts ranges from 2.43 (in alfalfa dominated fields) to 5.33 (in pasture grass dominated fields) ds/m. These field tolerances are based on the salt tolerant species planted in the fields. The 18 soil samples indicated EC ranging from 0.3 to 3.7 dS/m. Overall, the soil salinity presented on Table 2 is below the allowable salt tolerances (prior to crop reductions) presented on Table 1. Therefore, this indicates that crop yield reductions have not occurred. Collected crop yields, presented in Section 4.0 are a responsive to unpredictable volumes of irrigation water delivered to these fields, since they are junior water rights. Under irrigated conditions in arid and semi-arid climates, the build-up of salinity in soils is inevitable. The severity and rapidity of build-up depends on a number of interacting factors such as the amount of dissolved salt in the irrigation water and the local climate. However, with proper management of soil moisture, irrigation system uniformity and efficiency, local drainage, and the right choice of crops, soil salinity can be managed to prolong field productivity.