Influence of Lime Sources and Rates on ‘Coastal’ Bermudagrass Production, Soil Profile Reaction, Exchangeable Ca and Mg1

Abstract

AbstractThe effects of liming on ‘Coastal’ bermudagrass (Cynodon dactylon (L.) Pers.) production, soil profile pH, and exchangeable Ca and Mg levels were studied on Cecil sandy loam under high N fertilization conditions. During the 7‐year study, a total of 5,605 kg/ha of N as NH4NO3 was applied to the experimental area.Maximum Coastal bermudagrass production was associated with a soil pH of 4.8 or higher. During the last year of study, average forage production was 1,592 kg/ha higher at pH 4.8 than at pH 4.3. No significant forage yield increases were measured above pH 4.8.Without lime, soil pH as well as exchangeable Ca and Mg were sharply reduced in the top 45 cm of soil. Exchangeable Ca decreased from 1.22 to 0.15 meq/100 g and Mg from 0.31 to 0.15 meq/100 g in the surface 15 cm of soil. Below 45 cm a buildup of Ca, but not of Mg, occurred. There were net losses of both Ca and Mg from the entire soil profile on the unlimed plots between 1957 and 1963.Ca and Mg depletion from the soil profile was largely prevented by application of 20.2 tons/ha of dolomitic limestone. Calcitic limestone, as compared with dolomitic, effected higher exchangeable Ca levels throughout the soil profile and also had a greater effect in increasing soil pH; however, soil profile Mg content decreased to levels corresponding to those of the unlimed treatments.These results indicated that lime rates of 20.2 tons/ha applied initially or 24.7 tons/ha split over the 7‐year period, although generally considered excessive for this soil, did not reduce forage yields. In fact, these rates appear necessary under high N fertilization to prevent the development of soil acidity and serious depletion of Ca and Mg from the soil profile.