Abstract
Calcium perphosphate, ammonium nitrate, and potassium sulfate were added to Andosol and Gray Lowland Soil and mixed with different intensities like at 0, 0.5, and 5 or 10min with a rotary mixer and greens (Brassica pekinensis) were cultivated in 35-L containers. In the case of the 0-min mixing (non-mixing) plot, fertilizers and soil were put in layers alternatively in surface 10cm. The following phenomena were obtained with Andosol. The growth of greens was decreased with mixing time even as short as 0.5min and the dry yield of mixing plots was 62-75% that of non-mixing plot. Though the decrease of the amount of available P by BRAY'S 2nd method was not detected, P content and the amount of P uptake by greens in mixing plots was below 60% that of non-mixing plots. On Gray Lowland Soil, no such result was obtained. The growth inferiority of greens in mixing plots of Andosol was concluded to be due to the P defect, which is the result of P fixation by active Al of Andosol by mixing of P fertilizer and the soil. P fertilizer should, therefore, be applied with little mixing or ploughing in Andosol fields.
