Dynamics of effectiveness and guarantee of fertilizers in crop rotation on podzolic sandy-clay soil
1994
Valgus, T.
The dynamics of mineral fertilizer and manure effectiveness were studied in long-term fertilizer trials over 17 years. The trials were established on a highly cultivated podzolic sandy-clay soil. Field grass, a mixture of clover and timothy, constituted 33 per cent of the crop rotation, which helped to avoid the decrease in yield ability of the background. Therefore, the fertilizer effectiveness did not increase at the cost of a decrease yield from the background, but due to the after-effect of fertilizers. The results verify an earlier study, according to which in fertilized variants higher yields were accompained by higher fertilizer effectiveness. The correlation with yield was, in the case of mineral fertilizer effectiveness 0,77, and in the case of manure effectiveness 0,64. An earlier, 8 year long study, according to which the optimum manure dose per ha was 9,4 t, was completed. As the trial conditions were improved and trial period prolonged, the after-effect of manure increased, and the optimum manure rate on podzolic sandy-clay soil turned out to be 15 t/ha. The mineral fertilizer and manure effectiveness increased over 17 years due to the increase in the after-effect of fertilizers. The application of N60P21,8K49,8 resulted in the effectiveness of 17,5 feed units/kg N+P+K, which increased by 0,37 FU, i.e. 2 per cent per year. The application of manure (15 t/ha) gave the average effectiveness of 30 FU/t, which increased 2,4 FU, i.e. 8 per cent per year. The fertilizer effectiveness was better guaranteed over a longer trial period. An additional yield, obtained with mineral fertilizers or manure, could be obtained in the 1st rotation (1976-1981) with the frequency 2...4 times out of 10, but in the 3rd rotation with a frequency of 7 times out of 10
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