Reply on CC1

Abstract

Recycling of agricultural wastes to reduce mineral fertilizer input, in particular phosphorous (P), plays crucial role in sustainable agriculture production. Understanding the transformation of phosphorous (P) fractions and their bioavailability following soil application of different renewable P-contained fertilizers is very important for improving P use efficiency and reducing environmental risks. In this study, the effects of mineral P-fertilizer superphosphate and recycled P-fertilizers, i.e., poultry manure, cattle manure, maize straw and cattle bone meal, on their distribution to different soil P fractions, their transformation and the availability of soil P were determined by soil P sequential fractionation and 31P solution nuclear magnetic resonance (NMR). The results showed that addition of mineral P fertilizer, poultry manure and cattle manure increased P fixation in a red soil more than that in a fluvo-aquic soil. In both fluvo-aquic and red soils, cattle manure out-performed all other recycled P sources used in improving soil P availability. The concentration of Olsen-P in fluvo-aquic and red soils supplemented with cattle manure were increased by 41 %–380 % and 16 %–70 % than the other recycled P sources. A structural equation model (SEM) explained 95 % and 91 % of Olsen-P variation in fluvo-aquic and red soils, respectively. Labile P fractions had positive effects on Olsen-P of fluvo-aquic and red soils. 31P-NMR study showed that amount of orthophosphate was the main factor affecting the availability of P from different P sources. In summary, cattle manure was found to be a superior renewable source of P in improving bioavailable P in soil, and its use thus has considerable practical significance in P recycling.