Effects of Gypsum Application Rate and Frequency on Corn Response to Nitrogen

Abstract

1109 Gypsum is commonly used as a soil amendment and as a fertilizer in agriculture. In fact, it is one of the earliest forms of fertilizer used in the United States, and its use dates back more than 200 yr (Wallace, 1994). Gypsum is an excellent source of calcium (Ca) and sulfur (S) for plant nutrition, as Ca2+ and SO4 2− ions become readily available in soil solution after its application (Shainberg et al., 1989; Chen and Dick, 2011). Recently, there has been an enhanced interest in using gypsum as a S source due to a potential for S deficiency in crops resulting from reduced S inputs (Chen et al. 2005, 2008; Buckley and Wolkowski, 2012; Kim et al., 2013; Steinke et al., 2015; Sutradhar et al., 2017). Gypsum as a soil amendment or conditioner, is known to provide a multitude of benefits by promoting soil aggregation and enhancing soil physical structure. Gypsum can reduce soil dispersion, prevent soil crust formation, promote better seedling germination, facilitate better water infiltration and soil aeration, improve crop water relations, increase soil drainage, reduce soil erosion and runoff, and also improve water quality by decreasing phosphorus (P) losses from soils (Shainberg et al., 1989; Wallace, 1994; Amézketa, 1999; Amezketa et al., 2005; King et al., 2016; Kost et al., 2018). Gypsum application aids in the alleviation of aluminum (Al3+) toxicity and promotes better plant growth in soils affected by subsoil acidity (Toma et al., 1999). Gypsum can, therefore, favorably modify soil physical and chemical properties to provide better growing environments for plants. This could, in turn, facilitate plant root exploration into greater soil volumes and to deeper depths of the soil profile resulting in better water and nutrient use efficiency and might reduce nutrient input needs (e.g., N) (Dick et al., 2006; Watts and Dick, 2014). Given its wide range of benefits, producers are interested to incorporate gypsum as one of the management practices to improve agricultural production and sustainability. The benefits associated with gypsum applications are, however, both shortand long-term and depend on the purpose for which it is being used. Nutritional benefits (i.e., S fertilization) associated with gypsum are short-term (1–2 yr), direct and require lower application rates. Changes in soil physical and chemical properties require more time (>3 yr) and often repeated gypsum applications at higher rates, to produce any yield benefits (Watts and Dick, 2014). Annual application rates can therefore range from 100 kg ha–1 when gypsum is used as a nutrient source to several megagrams per hectare if used as a soil conditioner (Chen and Dick, 2011). Effects of Gypsum Application Rate and Frequency on Corn Response to Nitrogen