The 22-year long-term P-exhaustion field experiment was set up in 1972 in a split-plot design with 12 replications on pseudomyceliar chernozem soil with poor original supplies of phosphorus at the Experimental Station of the Institute in Nagyhörcsök, with build-up P rates of 0, 120, 240, 360, 480, 600 and 720 kg P2O5·ha-1. The indicator crops were winter wheat in the first 8 years, millet in the 9th year, alfalfa in years 10-12, spring barley in the 13th year and winter wheat again in years 14-22. The design of the experiment made it possible to observe decreases in the efficiency of previous P fertilization over time on the basis of initial "old" P doses applied in autumn 1972, which formed the basis of the experiment on P residual effects. In order to determine the fresh applied superphosphate-equivalency of the two-, four-, six-, eight-... twenty-year residual effects, the increasing "old" P levels in parallel plots in the 12-replication experiment were fertilized every two years from 1974 to 1990 with 0, 40, 80 and 120 kg P2O5·ha-1, one "old level in a time. By 1990 there were thus 36 different P treatments, and the number of replications was reduced to three.For four years after the application of build-up rates of P fertilizer, there was an intensive reduction in the AL-P contents, followed by a three-year equilibrium on this calcareous soil, which only weakly bound the P. This was followed by a further three years of more moderate P fixation, and then by another six years of equilibrium.The residual effects of the 240, 480 and 720 kg P2O5· ha-1 rates provided satisfactory P supplies ensuring high yields of winter wheat (1.2-1.5 t·ha-1 yield surpluses) for four, six and eight years, respectively. The residual effects of P fertilization could still be detected between the 9th and 20th years, though at lower and lower yield levels.Over the years the "fresh" P equivalency of the previous P application gradually declined. The "half-life" of the "old" P fertilizer, i.e. the time required for its effect to be reduced by half, could be estimated at 3-4 years. In a continental climate in the temperate zone, the decrease in the residual effects of previous P fertilization can be attributed to plant P uptake and to the fixation of P fertilizer in the soil.As time went by, the P balance indicated that an increasingly small proportion of the fertilizer-P remaining in the soil was still available to the plants (i.e. in AL-soluble form) due to the transformation of water-soluble monocalcium phosphates into less soluble calcium phosphates and the more intensive P fixation.When studying the efficiency of P fertilization, a knowledge of the utilization percentage of the P fertilizer could be extremely useful. After the 22nd year of the experiment, the amount of 53, 43 and 36%, respectively, of the 240, 480 and 720 kg P 2O5·ha-1 P rates could be detected over and above the P uptake of plants in the P control (NK) plots (the natural P supplies of the soil).When planning P fertilization, attention should be given to the P-supply of the soil, to soil properties influencing P fixation (texture, pH, lime status, etc.) and to the price of P fertilizers. In the present economic climate, it is not advisable to apply P in advance for periods of more than 2-3 years, even on soils with a lower rate of P fixation.
|Translated title of the contribution||The 22-year residual effect of phosphorus fertilization on pseudomyceliar chernozem soil|
|Number of pages||16|
|Journal||Agrokemia es Talajtan|
|Publication status||Published - Jun 1 2013|
ASJC Scopus subject areas
- Agronomy and Crop Science
- Soil Science