Effect on a peat soil of application of superphosphate at various rates

Authors

• Armi Kaila University of Helsinki, Department of Agricultural Chemistry

DOI: https://doi.org/10.23986/afsci.71475

Abstract

The effect on a fen soil of superphosphate applied for 34 years at the annual rates of 0, 100, 200, and 300 kg/ha was studied. The material consisted of samples from a field trial at the Leteensuo Experiment Station. The soil samples from the ploughing layer were collected in autumn 1956, and the hay samples from the crop harvested in 1957. The hay yields from the treatments with 200 or 300 kg/ha of superphosphate were about 7400 kg/ha, and the phosphorus content of the hay 1.69 and 1.85 per cent, respectively. The treatment with 100 kg/ha of superphosphate yielded only about 5100 kg/ha of hay dry matter with a very low phosphorus content, 0.96 per cent. The yield from the untreated plots was almost negligible. Also the biological and chemical soil tests showed that the untreated soil was almost depleted of available phosphorus. The phosphorus conditions in the soil annually treated with 100 kg/ha of superphosphate were not significantly better than in the untreated soil. An annual anplication of 200kg/ha of superphosphate was able to maintain a more satisfactory rate of available phosphorus in the soil, but only the treatment with 300 kg/ha of superphosphate resulted in markedly higher test values than those for the lower treatments. The total phosphorus content of the soil was the higher the larger the amount of superphosphate applied. About 40 to 50 per cent of the differences between the total phosphorus content of the treated and untreated samples was due to organic phosphorus. The potassium content of the hay was the lower the higher the superphosphate treatment. The hay from the treatment with 300 kg/ha of superphosphate contained only 1.25 per cent potassium. The possibility that potassium was a minimum factor in this treatment was discussed.