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Fertilizer phosphorus (P) is generally added to agricultural soils to meet the needs of crop production. In this study, the crop yield and soil Olsen P were measured every year (5-18 years) at 16 winter wheat (Triticum aestivum L.) -maize (Zea mays L.) crop rotation sites in cinnamon soil (Luvisols in FAO system). The mean agronomic critical value of Olsen P for maize was 14.2 mg kg−1 and for winter wheat was 14.4 mg kg−1 when using the Liner-plateau and Mitscherlich models. The change in soil Olsen P was positively linearly correlated with the P budget (P < 0.01), and an increase of 4.70 mg kg−1 in soil Olsen P for each 100 kg ha−1 of P budget in the 0-20 cm soil layer. A model of P fertilizer recommendation rate that integrated values of the change in soil Olsen P in response to P budget and the agronomic critical value of Olsen P was used, in order to adjust current levels of soil Olsen P to the agronomic critical value at the experimental sites over the next 5 years, P fertilizer application rate should be in the range of 0-87.5 kg P ha−1. [ABSTRACT FROM AUTHOR]

A rhizobox experiment was conducted to investigate the effects of phosphorus (P) sources on the rhizosphere soil characteristics of two wheat genotypes Xiaoyan54 (P-efficient) and Jing411 (P-inefficient), which were colonized with an arbuscular mycorrhizal fungus and grown in Cumulic Haplustoll. The four P sources included a control (no added P), OP [organic P: sodium (Na)-phytate], IP [inorganic P: monopotassium phosphate (KH2PO4)], and OPIP (Na-phytate plus KH2PO4). The results showed that when no exogenous P was added the shoot biomass of Xiaoyan54 was 28% significantly higher than Jing 411. The acid phosphatase activity (APA) in the rhizosphere soil was significantly depressed when inorganic P was added; the APA for Xiaoyan54 was higher than that of Jing411 in most of the layers regardless of the P source. Inorganic and organic P fertilizer conditions did not significantly impact the soil pH relative to the control, and the pH did not significantly differ between the two genotypes. In conclusion, when no exogenous P was added, shoot biomass of Xiaoyan54 was greater than Jing411. This increase was promoted by greater soil APA but not soil acidification. The rhizosphere soil pH was not altered across different wheat genotypes or P sources, but APA was increased in the soil of control and OP-treated plants compared with IP- and OPIP-treated plants. The APA of Xiaoyan54 was higher than Jing411 for all of the P sources. The response mechanism of rhizosphere soil acidification is different from acid phosphatase exudation in plants receiving different P sources under arbuscular mycorrhizal fungus inoculation. [ABSTRACT FROM AUTHOR]

A glasshouse study was conducted to compare the rhizosphere characteristics of two wheat genotypes, Xiaoyan54 (XY54) and Jing411 (J411) on two soils. The results showed that supplying phosphorus (P) increased the biomass and P content of two wheat lines significantly on alkaline soil, but P fertilization altered their biomass and P content on acidic soil only slightly. XY54 decreased rhizosphere pH more significantly than J411 on Fluvo-aquic soil without P addition, but similar acidity ability was shown when P applied. On red soil, two wheat genotypes showed similar rhizosphere pH. Two wheat lines showed similar rhizoshphere phosphatase activity on alkaline soil, whereas XY54 demonstrated greater rhizoshphere phosphatase activity than J411 on acidic soil. Rhizoshphere phosphatase activities of two wheat lines on acidic soil were greater than alkaline soil. Therefore, stronger acidity on alkaline soil and greater phosphatase activity on acidic soil are principal rhizosphere mechanisms for XY54 to adapt to low-P soils. [ABSTRACT FROM PUBLISHER]