Yield of sugar beet and changes in phosphorus fractions in relation to long term P fertilization in chestnut soil of Kazakhstan

Excessive phosphorus (P) application can alter soil P availability and limit plant growth by P fixation into different organic and inorganic P forms. However, it remains uncertain whether these changes happen after limited fertilization or an excessive rate applied under the crop rotation. The current study aimed to investigate the yield of sugar beet in response to long term P fertilization, and to investigate long-term P fertilization effects on soil P fractions after long-term fertilizations in chestnut soil of Kazakhstan. A long-term study (56 years) was conducted to assess the changes in total P, available P and inorganic P (Pi) fractions in response to different P rates applied to sugar beet. Inorganic P fractions were determined using the Ginzburg and Lebedeva (1971) and Ginzburg (1981) methods. Our findings demonstrated that different P rates significantly increased the total P and available P in the inorganic P fractions compared to N0P0K0 treatment (Absolute control). The N1P2K1 (100% of recommended level of NK but 200% of P) treatment had a maximum yield and sugar content of sugar beet. Compared with N0P0K0, the proportions of Ca-PI, Ca-PII, Fe-P and Al-P of total inorganic P fractions associated with under fertilizer treatments increased. The highest content of fractioned P was found in the form of Ca–PIII.