L iming has a long history of improving peanut yields in the soils of the Coastal Plain. In 1948, it was reported that dolomitic lime top dressed at seedling emergence was as effective as gypsum applied at bloom in two of three cases. In 1982, some researchers reported two examples from sandy soils where limed plots yielded higher than gypsum-treated plots under leaching conditions. Lime can improve soil conditions for peanut growth through reducing Al, Mn, and Zn toxicity, or through increases in soil Ca and Mg levels.
The limited solubility of lime led some to believe that it could not supply available Ca to the fruiting zone as effectively as gypsum. This was reinforced by studies showing limited responses to lime. Lime application in the seed furrow at planting or applications in the fall prior to moldboard plowing were ineffective in supplying sufficient Ca to virginia type peanuts not only because of their greater Ca requirement, but also because of spatial unavailability. Timing of applications is also important. Applications at bloom are not effective, since the lime has insufficient time to react with the soil before the critical uptake period. In many cases, results from virginia market types were erroneously extended to smaller seeded cultivars.
Numerous studies conclusively show that lime can provide adequate Ca for maximum yield of runner-type peanuts when applied and incorporated into the pegging zone after moldboard plowing prior to planting. Where recommended to correct low pH, lime incorporated in the surface after moldboard plowing can also supply Ca (at a lower cost) and eliminate a trip across the field before bloom. Lime applied in the spring is less subject to leaching than gypsum, and the possibility of missing a needed gypsum application because of wet fields or scheduling problems is averted. Lime is not the most appropriate supplemental Ca source in all cases. Applying lime on freshly plowed soil is difficult, increases maintenance costs for spreader trucks, and can lead to undesirable compaction. High flotation equipment is better suited to this task, but very few of these expensive units are available. Many dealers have tractor-pulled spreaders available for farmer use, but timing can become a problem for growers with large acreage. They must turn the land, lime, and apply herbicides before incorporation.
Overliming can become a serious problem in some areas. If poorly drained sands of the Atlantic Coast (Aquults) are overlimed Mn deficiences are frequently observed. Greatly reduced pod yield has been found at pH 6.8 in comparison to pH 6.0 due to Mn deficiency. For this reason, excessive use of limestone as a Ca source should be avoided. In Georgia, North Carolina, South Carolina, and Virginia, growers are advised to keep pH below 6.3 in susceptible soils. When soil pH is adequate, Georgia recommends a pod zone (0-3 in.) soil sample at 10-14 days after planting. If soil test Ca is <500 lb/acre (250 ppm) gypsum application is recommened at first bloom for runner-type peanuts. Gypsum is always recommended for virginia-type peanuts and any peanuts to be used for seed.
From Hodges, S. C., G. J. Gascho, and G, Kidder (1993) Calcium and Magnesium, Chap. 6 in Southern Cooperative Series Bulletin No. 380 "Research-based Soil Testing Interpretation and Fertilizer Recommendations for Peanuts on Coastal Plain Soils". C.C. Mitchell, Editor.
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