Exogenous phosphorus compounds interact with nitrogen availability to regulate dynamics of soil inorganic phosphorus fractions in a meadow steppe

Liu, Heyong; Wang, Ruzhen; Wang, Hongyi; Cao, Yanzhuo; Dijkstra, Feike A.; Shi, Zhan; Cai, Jiangping; Wang, Zhengwen; Zou, Hongtao; Jiang, Yong

Here we investigated the effects of P compounds (inline-formulaKH2PO4 and inline-formulaCa(H2PO4)2) with different addition rates of 0, 20, 40, 60, 80, and 100 kg P hainline-formula−1 yrinline-formula−1 and inline-formulaNH4NO3 addition (0 and 100 kg N hainline-formula−1 yrinline-formula−1) on soil labile inorganic phosphorus (IP) (dicalcium phosphate, inline-formulaCa2-P), moderate-cycling IP, and recalcitrant IP fractions in a calcareous grassland of northeastern China. Soil moderate-cycling IP fractions, not readily available to plants but transforming into soil-available P quickly, include variscite (Al-P), strengite (Fe-P) and octacalcium phosphate (inline-formulaCa8-P); recalcitrant IP fractions include hydroxylapatite (inline-formulaCa10-P) and occluded P (O-P). Soil labile and moderate-cycling IP fractions and total P significantly increased with increasing P addition rates, with higher concentrations detected for inline-formulaKH2PO4 than for inline-formulaCa(H2PO4)2 addition. Combined N and P treatments showed lower soil labile IP and moderate-cycling IP fractions compared to ambient N conditions, due to enhanced plant productivity. Moderate-cycling IP was mainly regulated by P addition and plant P uptake to further enhance labile IP and total P concentrations with inline-formulaKH2PO4 and inline-formulaCa(H2PO4)2 addition. Soil labile IP was also directly and negatively affected by soil pH and plant P uptake with inline-formulaCa(H2PO4)2 addition. inline-formulaCa(H2PO4)2 addition significantly increased the soil recalcitrant IP (inline-formulaCa10-P) fraction, while inline-formulaKH2PO4 addition showed no impact on it. A significant positive correlation was detected between soil labile IP, moderate-cycling IP fractions and soil Olsen-P which illustrated that labile IP and moderate-cycling IP fractions were important sources for soil-available P. Our results suggest that moderate-cycling IP fractions are essential for grassland P biogeochemical cycling and the chemical form of P fertilizer should be considered during fertilization management for maintaining soil-available P.

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Liu, Heyong / Wang, Ruzhen / Wang, Hongyi / et al: Exogenous phosphorus compounds interact with nitrogen availability to regulate dynamics of soil inorganic phosphorus fractions in a meadow steppe. 2019. Copernicus Publications.

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