Irrigation frequency effects on leaching of cations from gypsum amended coastal plain surface soils

In low Ca soils, gypsum is applied at flowering of peanut (Arachis hypogaea L.) to insure adequate availability of Ca in the fruiting zone (0 to 8 cm soil depth) during pod development. Effects of 15.2 cm water applied as 1, 2, 4 or 12 split applications over 28-d period following the application of gypsum on the distribution of Ca and other cations in the fruiting zone and immediately below the fruiting zone (8 to 16 cm depth) were investigated on the Lakeland and Tifton soils under controlled conditions in rainout shelter plots. In Lakeland soil, the fruiting zone Ca concentration was greater for the high frequency (15.2 cm in 4 or 12 split applications) irrigation treatments than for the low frequency (15.2 cm in 1 or 2 split applications) treatments at 7 d. Those differences became non-significant after 14 d. In Tifton soil, leaching of Ca below the fruiting zone was significantly greater for the low frequency irrigation treatments than for the high frequency treatments throughout the duration of this e experiment. High frequency irrigation of moderate quantities should result in low Ca losses from the fruiting zone. Irrigation following gypsum application decreased K and Mg concentrations in the fruiting zone for both soils. The gypsum-induced leaching of K or Mg was lower in high frequency irrigation treatments than in low frequency treatments. High frequency irrigation following gypsum application resulted in a decrease in soil pH during the initial 7 d.