Saline Cooling Tower Water for Irrigation in Minnesota: I. Crop and Soil Effects
1985
Engel, R. E. | Malzer, G. L. | Bergsrud, F. G.
Saline cooling tower water (CTW) from the Northern States Power coal-fired plant in Sherburne County, MN was used to irrigate a Hubbard loamy sand (Udorthentic Haploboroll). The objectives of this study were to determine the changes in soil solution salinity, to measure salt accumulations in the soil profile (0- to 240-cm), and to assess the impact of CTW on crop production. In a 3-yr field study, CTW (2.2 dS m⁻¹) was applied at two rates to alfalfa (Medicago sativa L.), corn (Zea mays L.), and fallow areas. Analysis of the soil water for electrical conductivity (ECₛw) at 75 cm indicated that an increase in salt concentration occurred over the growing season. Maximum seasonal ECₛw at 75 cm in the cropped areas (3.0–4.0 dS m⁻¹) were higher than in the fallow areas (2.0–2.5 dS m⁻¹). Rainfall between the growing seasons, however, was adequate to leach the upper 75 cm of this coarse-textured soil and prevent a stepwise buildup of salts from one year to the next. After an initial buildup, ECₛw at 225 cm was relatively stable. For the last 2 yr, ECₛw at 225 cm was consistently higher under alfalfa than corn or fallow areas. A seasonal buildup of SO₄ occurred during the growing season. In the fall, SO₄ accumulations in the 0- to 60-cm soil layer were highest under corn. By the following spring, there was no difference between the three cropping systems. Rainfall was very effective in leaching seasonal accumulations of SO₄ from the soil. A lower Ca/Mg ratio in the CTW, as compared with the soil, resulted in increased concentration of Mg in the 0- to 60- and 60- to 150-cm soil layers. Corn grain and alfalfa production averaged 8440 and 8230 kg ha⁻¹ for the last two seasons, respectively, and were not adversely affected by salinity produced from the CTW application.
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