Water Quality Effects on Soils and Alfalfa: I. Water Use, Yield, and Nutrient Concentration

Abstract

AbstractThe detrimental effects of salt buildup in northern Great Plains soils need quantification. This study was conducted to evaluate effects of irrigation water quality on alfalfa (Medicago sativa L.) yield, water use, and nutrient concentration during a 21‐mo period. Irrigation waters of seven qualities, totaling 4400 mm in wet/dry cycles, were applied to 20 by 60 cm undisturbed soil columns under green‐house conditions. Four loam soils representing moderate to moderately slow permeable drainage classes were used. The soils were: Williams loam (fine‐loamy, mixed Typic Argiboroll), Barnes loam (fine‐loamy, mixed Udic Haploboroll), Svea loam (fine‐loamy, mixed Pachic Haploboroll), and Parshall loam (coarse‐loamy, mixed Pachic Haploboroll). Effects of soil, water quality, and time on yield and water use were highly significant (R2 = 0.94*** [*** denotes significance at P = 0.001] and 0.93***, respectively). In all soils and waters, yield and water use decreased 30 to 60% by the end of the experiment. Mean nutrient concentrations, with the exception of Na, remained within 10% of the original values. Irrigation water with sodium adsorption ratio (SAR) of 20 and ionic concentration of 20 mmolc L−1 increased the alfalfa Na concentration to 15 times that with distilled irrigation water. Total Na added accounted for 84%*** of variation in relative yield. One‐half of the salt‐induced yield reduction appeared in the first third of the experiment. This underscores the inadvisability of irrigating with poor‐quality water that might be available during drought periods.