Submitted to: Soil Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/18/2007
Publication Date: 2/1/2008
Citation: Favaretto, N., Norton, L.D., Brouder, S.M., Joern, B.C. 2008. Gypsum amendment and exchangeable calcium and magnesium effects on plant nutrition under conditions of intensive nutrient extraction. Soil Science. V. 173(2):108-118. Interpretive Summary: Balancing plant nutrient through the use of various soil amendments has long been studied. The use of gypsum as a soil amendment to control soil erosion has been suspected to cause an imbalance of nutritional cations are therefore lead to deficiencies in plants. We studied solution and plant tissue concentrations of nitrogen (N), phosphorous (P), potassium (K), calcium (Ca) and magnesium (Mg) in corn shoots and roots in soil amended with gypsum to change the abundance of Ca relative to Mg. In a greenhouse experiment we compared various ratios of Ca to Mg, gypsum at 5 ton per hectare amendment and a control soil. All pots were amended with N at recommended rates while no P or K was required. The pots were harvested after 23 days of plant growth. We found that changing the Ca/Mg did affect the amount of each in the plant, meaning high Ca resulted in high Ca in plant etc., but it did not affect the K or N uptake. However, addition of gypsum increased both K and Ca uptake, decreased P and did not affect the amount of N or Mg taken up by the plant. Gypsum decreased the amount of P and increased the amount of Ca, Mg, K and ammonium in soil water but did not affect plant root or shoot growth either negatively or positively at the early stage of growth studied. The impact of this research is that soils can be amended with gypsum to control soil erosion without fear of nutrient deficiencies or negative effects on plant growth.
Technical Abstract: In general, the increase of one cation species in the soil solution can decrease the levels of other cations in the plant. The competitive effect of soil nutrients on plant absorption has been studied under diverse conditions, some studies focusing on the physiological and others on the plant nutrition aspects. However, there is not a common opinion concerning this subject and it is still the object of studies today. The objective of this research was to analyze the effects of gypsum amendment and soil exchangeable Ca/Mg ratios on the soil, solution and plant tissue concentration of N, P, K, Ca, and Mg, and on corn (Zea mays L.) root and shoot growth. A greenhouse experiment was carried out involving treatments with five different exchangeable Ca/Mg target ratios (90/10, 80/20, 50/50, 20/80, 10/90), gypsum (5000 kg ha-1) and a control. Calcium and Mg on the exchange complex were modified by saturation with CaCl2/MgCl2 solutions according to the target ratio followed by washing with CaSO4/MgSO4 solution to adjust the electrolyte concentration similar to the control. Before corn seeding, all pots (1 kg soil pot-1) received N fertilizer as NH4NO3 (88 mg N kg-1 soil). Phosphorus and K were not applied. Plants were harvested 23 days after planting, and shoots, roots, and soil samples were collected for analysis. Shoot and root dry matter, root length, and concentration of nutrients (N, P, Ca, Mg, and K) in plant, soil and solution were analyzed. Exchangeable Ca/Mg ratios affected Ca and Mg uptake but did not consistently affect K and N uptake or root and shoot growth. Compared with the control (unamended), gypsum increased K and Ca uptake, decreased P, but did not interfere with Mg or N uptake. Gypsum decreased P and increased Ca, Mg, K and NH4 water solubility; however, none of these differences affected corn root and shoot growth.