Importance of Phosphate Buffer Power for Phosphate Uptake by Rye

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Abstract
As soil test data for available P are often unsatisfactory, it was investigated whether the integration of the P buffer power of soils would improve the information from soil tests. The P buffer power of eight soils differing widely in their characteristics was assessed by plotting the calcium‐lactate exchangeable P (P quantity) vs. the electro‐ultrafiltration extractable P (P intensity). After dressing these soils with increasing amounts of soluble phosphate, they were analyzed for available P after an incubation period of 1 week by extracting P using electro‐ultrafiltration (EUF‐P) and calcium‐lactate (CAL‐P). The P concentration in the tops and the P uptake of young rye (Secale cereale L.) plants grown on these soils in pots supplied with five increasing P rates were correlated with the EUF‐P and CAL‐P soil test data. Significant and highly significant correlations between soil test and the P uptake and soil test and P concentration in rye seedlings, respectively, were obtained. These correlations were further much improved when the P buffer power of soils was integrated into the computation in the form of a multiple regression analysis. The R2 thus obtained was about 0.8, showing that about 80% of the variance in P uptake and P concentration in plant tops can be related to the variance in the P soil test data (CAL or EUF technique) and to the variance of the P buffer power of soils. It is concluded that soil tests for available soil P can be substantially improved by taking into consideration the P buffer power of soils.