Effect of excess MgSO4 or Mg(HCO3)2 in irrigation water on corn growth |
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| Abstract: | Abstract Some irrigation waters have a high Mg/Ca ratio. The objective of the experiment reported herein was to compare the effect of high Mg in combination with different anions and different EC levels on the growth of corn (Zea mays L.). Corn was grown in the greenhouse in a calcareous soil equilibrated and irrigated with the following waters: 1) tap water (check, EC = 0.078 dS/m, SAR = 0.1); 2) Mg(HCO3)2, EC=1 dS/m; 3) Mg(HCO3)2, EC = 3; 4) MgSO4) EC=1; 5) MgSO4, EC=3; 6) MgSO4, EC = 6; and 7) and 8) mixed salts (Ec = 3 & 6 dS/m, SAR = 5, Ca: Mg = 3: 1, Cl: SO4 = 2: 1). Yield depressions of top growth caused by mixed‐salt waters (EC = 3 & 6) were 17 and 26%, respectively, compared to yields obtained with tap water. Single‐salt MgSO4 waters (EC = 1, 3 & 6) reduced corn tops 19, 38, and 59%, respectively, more than the mixed‐salt solutions at equivalent soil salinity levels probably due to Mg‐induced Ca deficiency. The Mg(HCO3)2 waters (EC = 1 & 3) reduced top growth 45 and 87% more than the mixed salt solutions. Thus Mg (HCO3)2 was more than twice as depressive on corn top growth as MgSO4. Corn root growth depression was similar to top growth depression. Leaf Ca: Mg ratio was related to their ratio in the soil solution. The leaf Ca and Mg concentrations were almost the same for plants irrigated with Mg(HCO3)2 or MgSO4 at EC = 1. Therefore, Mg: Ca ratio of leaves did not explain the yield differences between the two Mg salts. Nutrient imbalances and a high pH of 9 were possibly responsible for the lower yields in the presence of Mg(HCO3)2. |
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