Use of the electroultrafiltration (EUF) technique to study the potassium dynamics of wetland soils and potassium uptake by rice

Abstract

Potassium uptake by rice was studied in relation to the K dynamics of two soils (Pili clay and Maligaya silty clay loam) from the principal rice growing provinces in the Philippines (Camarines Sur and Nueva Ecija). The K dynamics were determined by means of the EUF technique and by establishing the K buffer capacities of both soils. Although the Maligaya silty clay loam was higher in exchangeable K, the K uptake by the crop, particularly at the early growing stage, and the K concentrations of the young crop were higher in the Pili clay. This was consistent with the EUF extractable soil K (EUF-K), indicating that the EUF-K was a better indicator of K availability than the exchangeable K. The Maligaya silty clay loam showed a higher K buffer capacity than the Pili clay. This higher K buffer capacity also contributed to higher K uptake, especially during the later growth stage. Maximum grain yields, however, were obtained when the value of the Total EUF-K Fractions was above 40 ppm K at the maximum tillering stage of the rice crop.