Changes of phosphorus fractionations in soil aggregates under long-term fertilization management on the Chinese Loess Plateau

Abstract: Phosphorus (P) is an essential non-renewable soil nutrient, important for plant growth and crop production. The primary productivity of agricultural ecosystems largely depends on the availability of P (P fractionations) in the soil. Thus, the identification of P fractions is indispensable for understanding the mobility and availability of P in agricultural soils. Widely used P fractionation schemes also allow the evaluation of the fate of P applied to soils and its relationship with plant’s P nutrition, forms of P, and uptake. Due to the potential mobilization and circulation of P fraction content in nature, it can aid the identification of P accumulation and eutrophication threat in the agro and aqua environment. So, evaluating P fractionation changes in certain soil aggregates under varied fertilization practices could imply the significant P status in the agroecosystem’s soil but has yet to be improperly clarified.This study was conducted in the long-term experiment field at the Changwu State Key Agro-Ecological Experimental Station was set up in 1984. Four distinct fertilization approaches, including CK, control (no fertilizer); P, phosphorus fertilizer; NP, mixed nitrogen and phosphorus fertilizer; and NPM, organic manure mixed with mineral fertilizers, were designed to apply in the wheat field. Soil samples were collected from three soil depths of each treatment to the maximum depth of 60 cm with an interval of 20 cm. All the soil samples were classified into four aggregate size groups by using a settling tube: >250 μm, 125–250 μm, 63–125 μm, and <63 μm. Finally, we focused on widely recognized Hedley’s sequential P extraction procedure to determine different P fractionations content.

i) Aggregate size distribution is significantly influenced by different fertilization practices where >250 µm aggregate and NPM treatment are mentionable. 

ii) Compared with the unfertilized plot, the average TP concentration increased by 250%, 220% and 328% in P, NP and NPM, respectively.

iii) A decreasing trend of overall P fractions content (Pi & Po) with aggregate size decreasing establish this rank order: (˃250 µm) ˃ (125-250 µm) ˃ (63-125 µm) ˃ (˂63 µm). It is also mentioned that Pi and Po content in ˃250 µm aggregate groups of NPM is 5 and 3.6 times higher than CK, respectively.

iv) SOC significantly impacts P fractions.

Authors: Milon Barmon ,Guo Shengli
Keywords: P fraction, Pi and Po pool, long-term fertilization, settling tube, Loess Plateau.
Journal Name: Northwest A&F University
Sponsoring Org.: APFNet
Publication Year: 2021