Efficiency of phosphorus fertilizers: research results in long-term field experiments in Russia, Great Britain and China

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The results of research in long-term field experiments on the effectiveness of phosphorus fertilizers are presented. All experiments were based on the classical scheme and included, in addition to the control variant (without fertilizers), a nitrogen-potassium background, on which the effectiveness of phosphorus fertilizers was studied. At the same time, regional specifics were taken into account in each experiment: liming at the Experimental Station of the All-Russian Research Institute of Agrochemistry (Russia), the effectiveness of phosphorus fertilizers at increasing doses of nitrogen N100–300 at the Rothamsted Experimental Station (Great Britain), a combination of phosphorus fertilizers with manure at the Chinese National Soil Fertility Monitoring Base. In long-term experiments, the dynamics of changes in the content of mobile phosphorus, as well as individual fractions, taking into account the emerging balance of P2O5, are presented. It is shown that the redistribution of phosphorus between different soil fractions is reversible, and the direction of the processes depends on the emerging balance of P2O5. Phosphorus accumulated in more firmly held forms can subsequently be released and absorbed by cultivated crops. In all field experiments an increase in the yield gap between NK and NK + P variants was observed over time. On the one hand, this is due to a significant decrease in the phosphorus content in the background NK variant (in acidic soils – also an increase in Al mobility), in which phosphorus removal significantly exceeds control (without fertilizers), on the other – a significant increase in the content of P2O5 in the soil with a positive balance. In a long-term experiment at the Experimental Station of the Institute of Agrochemistry, the difference coefficient of phosphorus utilization from fertilizers was 25–27, at the Rothamsted station – 25–41, at the Chinese National Soil Fertility Monitoring Base – 45%. Attention is drawn to the high payback of phosphorus fertilizers in experiments at the Rothamsted experimental station (Great Britain) – 22–39 kg of grain/kg of P2O5 (when cultivating winter wheat in crop rotation). The main method of increasing payback in this case was the use of high doses of nitrogen – up to 200 kg N/ha. Studies have shown that liming acidic soils to a slightly acidic reaction, the use of zinc micronutrients, as well as phosphate-mobilizing microorganisms, are essential methods to increase the effectiveness of phosphorus fertilizers.