Verification of the method of potential diagnostics of phosphorus nutrition of grain crops on the chernozem of the Novosibirsk Region’s Ob River area

Abstract

The research findings on the evaluation of chemical methods of soil diagnostics regarding phosphorus nutrition of grain crops on leached chernozem of the Novosibirsk Region’s Ob River area are discussed. Three methods were tested: Chirikov (0.5 N CH₃COOH), Karpinsky-Zamyatina (0.03 N K₂SO₄), Nikolov (0.2 N C₄H₄O₅ (NH₄)₂). In two-year small-plot field experiments (9 m²) in the Ordynskiy District of the Novosibirsk Region, against the background of N₆₀K₆₀, ammonium phosphate fertilizer was applied to spring wheat of the Novosibirskaya 31 variety at the rate of 30, 60 and 90 kg ha of the active ingredient. The initial supply of P₂O₅ in the soil according to Chirikov indicated no need for additional phosphorus application to grain crops, while the methods of Karpinsky-Zamyatina and Nikolov showed its deficiency. The field studies revealed a high positive effect of phosphorus fertilizers on spring wheat yield. On two-year average, grain yields increased by 24% and 28%, respectively, with 30 and 60 kg of phosphorus as compared to the control. Increasing the fertilizer application rate to 90 kg ha increased grain yield by 40% in 2021 and by 50% in the 2022 trial. The results of a structural analysis of the yield showed that the increase of wheat yield through phosphorus fertilizer application was primarily due to ear weight. The applied fertilizers did not affect plant number or thousand-kernel weight. The research data on the dynamics of mobile phosphorus in the arable soil layer allowed for a preliminary assessment of the chemical diagnostic methods being studied. The actual phosphate status of the soil was reflected by the methods of Karpinsky-Zamyatina and Nikolov. The standard chemical method of Chirikov was unsuitable for periodic diagnostics on leached chernozem in the Novosibirsk Region’s Ob River area.