Effects of Chicken Farming on Soil Phosphorus Availability and Associated Microbial Properties in Lei Bamboo (Phyllostachys praecox) Forest Ecosystems
Authors: Gai Xu , Li Shaocui , Zhang Xiaoping , Bian Fangyuan , Yang Chuanbao , Zhong Zheke 
Published: January 2021

Abstract
Background: Bamboo-chicken farming (BCF) is a popular bamboo complex management model in Southeast Asia owing to its high economic benefits. However, the effects of BCF on phosphorus (P) availability and the associated microbial communities in soil remain poorly understood. In this study, we compared the soil properties, P fractions, phosphatase activities, and bacterial community compositions in the surface soil (0–20 cm) of a typical bamboo (Phyllostachys praecox)-chicken farming system under different grazing densities (represented as distances of 5, 15, 25, and 35 m from the henhouse, respectively). The variables were also compared with the soil measurements from an adjacent pure bamboo forest without chicken framing (control site).Results: We observed a significant increase in soil pH, cation exchange capacity (CEC), total N (TN), total P (TP), and available potassium (AK) with increasing grazing density, while soil organic carbon (SOC) showed no significant difference between the sites. The total P accumulation of the soil was also more rapid than that of SOC and TN with increasing grazing density. Labile P and moderately labile P dominated the soil P accumulation under BCF. In particular, Resin-Pi (labile P), NaHCO3-Pi (labile P), and 1 M HCl-Pi (moderately labile P) increased by 100–233%, 83–183% and 414–1314%, respectively, compared with the control values. In contrast, the contribution of labile or moderately labile organic phosphorus to the total phosphorus (Pt) content decreased significantly with increasing grazing density from 38.54% (control) to 17.65% (5-m site). Phosphatase activity also increased with increasing grazing density, which suggests that BCF effectively promoted the mineralization of soil Po. A redundancy analysis showed that the changes in bacterial community structure were closely related to Resin-Pi and 1 M HCl-Pi (r2 = 0.938 and 0.958, respectively). The relative abundances of the phosphobacteria Flavobacterium, Pseudomonas, Streptomyces, and Arthobacter increased with increasing grazing density, while the abundance of Burkholderia decreased at the 5-m site. Inorganic P (Resin-Pi, NaHCO3-Pi, and 1 M HCl-Pi) was positively correlated with the abundances of Flavobacterium, Pseudomonas, and Arthrobacter but negatively correlated with the abundance of Burkholderia; this highlights the different functional bacteria involved in P cycling. Conclusions: We conclude that BCF generally increases soil P availability and supply, and the changes in the P forms were closely related to the changes in soil bacterial community composition. However, excessive grazing density or long-term BCF practices can cause soil nutrient imbalance, labile and moderately labile P accumulation, and P leaching. Therefore, appropriate grazing densities and/or an interval of no grazing are required under the BCF model for effective and sustainable bamboo forest management.