Ag Professional. November 2014. A new study conducted by two agricultural economists brings to light the top reasons that crop growers apply gypsum to cropland. The study cites increased yields, valuable sulfur fertility and soil quality improvements as key benefits of gypsum use, contributing to positive financial returns.
“On average, gypsum users received $1.68 in return for every dollar invested in gypsum. In addition, gypsum significantly improved the productivity of their soil,” said Marvin Batte, PhD, professor emeritus of The Ohio State University. “Many gypsum users, especially longer-term users, experienced even higher returns. Plus, there were significant environmental benefits as well.”
The study involved an extensive review of published scientific literature, in-depth interviews with several long-time gypsum users, and a survey of US farmers. The survey was conducted among readers of No-Till Farmer, as well as farmers that were known purchasers of gypsum.
Big returns for yield, improved fertility
“Returns were highest for alfalfa where users experienced dramatic increases in yield,” said Batte. “In alfalfa, returns per dollar of gypsum cost were often 5:1 or higher. In corn, 2:1 or higher. And there were also excellent returns in other crops, such as soybeans and wheat.”
Producers also found that gypsum improved the effectiveness and efficiency of other plant nutrients, including nitrogen, phosphorus and potassium.
Improved soil characteristics
While increased yield and improved fertility were among the easiest benefits to measure, improved soil quality was viewed by many – especially long-time gypsum users – as the most important benefit, according to study authors. Gypsum improves soil tilth and water infiltration, especially in soils with higher levels of clay or silt.
The most valuable soil improvement benefits, rated by a majority of users surveyed, included such items as improved plant rooting, improved seedling emergence, increased soil water retention, reduced runoff and improved absorption of nutrients. Enhanced soil biological activity was also noted.
“In all, there were more than 20 soil improvement characteristics that many gypsum users rated as ‘important,’” Batte said.
Long-term users apply more gypsum
The researchers found that gypsum’s economic returns and other benefits increased over time. Farmers who adopted the practice of applying gypsum prior to 2010, for example, gave higher scores for all benefits tested than did newer users, according to Batte and Forster.
Nearly 30 percent of longer-term users applied gypsum to all of their farm acreage in 2012 or 2013. Long-term growers applied gypsum to 45.7 percent of their cropland compared with newer users who applied it to 33.8 percent on average.
The research showed that gypsum provided environmental and societal benefits, too. Soil-applied gypsum may serve as a means to stabilize phosphorus in the soil and reduce downstream effects of phosphorus movement, a nutrient blamed for excessive plant growth in streams, lakes and coastal waters.
“Realizing that gypsum easily pays for itself in yield increases alone will give growers confidence in adopting this practice,” Chamberlain says. “But yield is only part of the story. Many operators also experience improvements in fertilizer efficiency, less nutrient loss and improved drought tolerance due to improved moisture retention. Those are benefits to their bottom line and to the environment.”
Growers have used gypsum to some extent since colonial times. Recent use has grown dramatically due to the availability of larger quantities of low-cost gypsum. While gypsum is a naturally occurring mineral that is mined, it is also produced as a by-product in several industrial processes, as well as in the scrubbing of sulfur from coal-fired power plants.