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

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.