Main content area

A study of the basicity of dolomite, rock phosphate, and other materials in preparing non-acid-forming fertilizers

Cook, H.L., Conner, S.D.
Agronomy journal 1936 v.28 no.10 pp. 843-855
tillage, field crops, sandy loam soils, soil pH, liming materials, phosphates, NPK fertilizers, nitrification, soil analysis, leaching, losses from soil, application rate, application timing, leachates
Results obtained with Norfolk sandy loam soil may be summarized as follows: 1. Additions of the fertilizer studied increased the acidity of the soil as determined by every method used. 2. Cropping the soil increased acidity. 3. Additions of dolomite, calcium carbonate, and calcium silicate reduced the acidity by every method used. 4. The coarse dolomite was not as good as the fine dolomite in reducing acidity. 5. The fine dolomite was the best of the carbonates in all cases. 6. The calcium carbonate was slightly better than the coarse dolomite but was not as good as the fine dolomite. 7. Tricalcium phosphate showed some value by the Hopkins and Jones acidity methods and by pH in KCl solution, but none by pH in water or by percentage saturation. 8. The four treatments with raw rock phosphate showed some neutralizing value with the Jones and Hopkins methods, but none by any other method. 9. The raw rock phosphate showed more acidity than the fertilizer alone by the pH and percentage saturation methods. 10. The calcium silicates were better than any other neutralizing material. 11. The quenched calcium silicate was slightly superior to the raw. 12. Attention is called to the similarity between the different methods when applied to the same soil. Results obtained with Miami sandy loam soil may be summarized as follows: 1. Addition of fertilizer reduced acidity by the Jones and Hopkins methods. 2. Fertilizer increased acidity by the percentage saturation method but had no effect on pH. 3. Coarse dolomite reduced the acidity in all cases except pH, but was not as good as the fine dolomite. 4. Calcium carbonate reduced acidity in all cases except pH, in water. 5. Calcium carbonate was not as good as fine dolomite. 6. Tricalcium phosphate showed no benefit by any method except Hopkins acidity. 7. Tricalcium phosphate showed an abnormally large reduction of the lime requirement by the Hopkins method on the Miami soil. 8. The raw rock phosphate shows a neutralizing value by the Hopkins method but not by any other method. 9. The calcium silicates were good neutralizers by all methods. With the exception of the Hopkins acidity on the Miami sandy loam, there is a significant similarity in the trend of results between various treatments on both soils. On the Norfolk sandy loam, the better nitrification may be the reason why the raw rock phosphate showed negative effects by pH and percentage saturation. There was in all cases better nitrification with the fine dolomite, the calcium carbonate, the tricalcium phosphate, and the calcium silicates than with the fertilizer alone or fertilizer neutralized with raw phosphate. In general, the pH curves of the two soils are similar. As can be seen in Table 5 the addition of dolomite increased the amount of both magnesium and calcium leached from the soil. The fine dolomite caused a greater loss than the coarse.