Soil pH and Gypsum Peanut Notes No. 54 2018
Low soil pH is often considered the “silent killer” in crop production, especially for peanut and soybean. On page 24, table 3-3 in 2018 Peanut Information we show crop response to soil pH. The numbers jump around but look closely at peanut and soybean. At pH 5.4 a 10-17% reduction in yield was observed for these crops compared with yield at optimum pH (5.9). Ten to 17% can be considered the profit margin. Certainly it is impossible to adjust pH for the 2018 peanut crop, but also look closely at table 3-4. When pH is lower than ideal we can create problems even with a typical application of gypsum. Although not documented in our work, gypsum lowers pH in the pegging zone, and an already low pH forced even lower by gypsum for a short period of time (the sulfate component of gypsum often decreases pH for several weeks after application) adversely affects peanut enough to cause a decrease in yield. Ultimately the recommendation is to keep pH at optimum levels. Doing so often opens the door for peanut to respond positively to other inputs, including gypsum.