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Crop Response to Different Soil Fertility Levels in a 5 by 5 by 5 by 2 Factorial Experiment: II. Peanuts¹

ABSTRACT

Four years' data are reported from a 5 by 5 by 5 by 2 experiment in which nitrogen, phosphorus, potassium and lime respectively, were the variables. The experiment was conducted on Red Bay fine sandy loam in west Florida.

No response to nitrogen was obtained.

There was a negative response to potash every year when more than 15 pounds of K₂O per acre as potassium chloride were applied. The level of exchangeable potassium in the soil did not seem to be responsible for the negative response. Ninety pounds of exchangeable potassium per acre was adequate for maximum yields. The lack of response to potassium may have been associated either with the application of the fertilizer potassium in the peanut row or with increasing rates of phosphorus applied as superphosphate. Since high rates of phosphorus are necessary for maximum yields of other crops grown in rotation with peanuts, excess potassium, equivalent to that removed by the peanuts, probably should be applied to the other crops in the rotation.

There was a significant yield response to phosphorus every year. When the soil was adequate limed, maximum yields were obtained when the soil contained 45 pounds per acre of P₂O₅ extractable with 0.002N H₂SO₄ buffered at pH 3 with (NH₄)₂SO₄ or 110 pounds per acre of P₂O₅ extractable with 0.03 N NH₄F in 0.1 N HCl; 10 of extractant to 1 of soil.

Calcium gave significant yield responses three out of four years. Three tons per acre of dolomitic lime were better than one. One ton per acre of lime raised the pH from 5.3 to 5.6 and the exchangeable calcium from 300 to 500 pounds per acre of Ca approximately. When 3 tons per acre of lime were applied, the pH was 6.2 and the exchangeable Ca 850 pounds per acre.

Phosphorus interacted with lime. Less fertilizer phosphorus was necessary to give maximum yields on limed than unlimed soil.

¹ Contribution from the Florida Agr. Exp. Sta. Published with the approval of the Director as paper No. 324 of the Journal Series.

² Assistant Soils Chemist, Gainesville; Vice-director in Charge, West Florida Sta., Jay; and former Associate Professor, Agronomy Dept., Univ. of Florida, respectively. Latter, now with Biometrical Service, U.S.D.A. Beltsville, Md.

Received for publication November 1, 1954.