Abstract
Phosphorus status of soils is regarded a component of soil fertility. This component can be influenced by cropping measures. In 1983 a number of Swedish fields with a high P status were identified. In all there were 17 fields chosen distributed over Sweden. On these fields P fertilizer experiments were started with the treatments 0, 15 and 30 kg P ha-1 yr-1. In average of all experimental sites the starting P-AL value was 19.6 mg 100-1g soil. Typically P-AL in Swedish arable soils are less than 10 mg, so the 19.6 average is a high value, pH varied from 5.1 to 7.3 with 46% of the sites having initial pH values less than 6.2. With no P applied the P-AL values decreased significantly with time. The slope of the regression line indicates that P-AL in the top soil decreased with 0.5 units year-1. The decline was statistically significant at the 5% level. When 30 kg P year-1 was applied the decline was insignificant. In the high pH range (≥ 6.2) the decline in P-AL was 0.67 units year-1 compared with 0.18 in the low pH group. Measurement of the uptake and removal of P with harvest products was chosen as the best method to analyse the crop response with time. When the experiments were pH grouped and the effects in cereals were analysed a positive effect on the P uptake with time was found.
Published Version
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