磷添加对棉田土壤理化性质及其细菌多样性的影响

Effects of phosphorus addition on soil physicochemical properties and its bacterial diversity in cotton field

【目的】为了解不同磷肥施用量对棉田土壤理化性质及其细菌群落结构的影响,以连续6年不同磷添加的田间定位试验为背景,探讨土壤细菌群落与其理化性质的关系。【方法】试验共设5个处理:0 kg/hm^(2)(P0)、75 kg/hm^(2)(P1)、150 kg/hm^(2)(P2)、300 kg/hm^(2)(P3)和450 kg/hm^(2)(P4)。测定花铃期棉田土壤含水率、温度、容重、pH、电导率以及有机质等理化指标,运用高通量测序技术分析不同施磷水平0~20 cm土层细菌多样性及其结构组成。【结果】施磷可以降低pH和电导率含量,而对土壤容重和含水量均无较大影响;不同施磷水平对土壤有机质含量和温度均产生显著影响,且在P2时达到最高。细菌群落结构中,2个优势菌门为变形菌门和放线菌门,3个优势菌纲为γ⁃变形菌纲、α⁃变形菌纲和β⁃变形菌纲,2个优势菌目为假单胞菌目和根瘤菌目,2个优势菌科为假单胞菌科和慢生根瘤菌科,4个优势菌属为中华根瘤菌属、慢生根瘤菌属、链霉菌属和糖多孢菌属。P2处理的OTU数和Chao1指数分别为4702和6217.79,均为最高。说明磷添加可以增加土壤细菌群落的丰富度和多样性。具有溶磷作用的3个门(放线菌门、变形菌门和浮霉菌门)和2个属(慢生根瘤菌属和链霉菌属)相对丰度随磷肥施入而显著升高。RDA分析结果表明,土壤pH、电导率、有机质和容重与放线菌门呈显著正相关,与变形菌门呈负相关。【结论】与不施用磷肥相比,施用磷肥可显著提高土壤温度、有机质和细菌优势菌群(浮霉菌门、β⁃变形菌纲、慢生根瘤菌属和链霉菌属)相对丰度,降低土壤pH和电导率。其中,P2处理的土壤温度、有机质和α多样性明显提高,电导率显著下降,能够有效改善土壤生态环境,进而提高土壤肥力。

【Objective】In order to understand the effects of different phosphorus fertilizer application rates on soil physical and chemical prop⁃erties and bacterial community structure in cotton field,the relationship between soil bacterial community and soil physical and chemical properties was investigated by field positioning experiments with different phosphorus additions for six consecutive years.【Method】Five treat⁃ments were tested by field localization experiments with different phosphate gradients:0 kg/hm^(2)(P0),75 kg/hm^(2)(P1),150 kg/hm^(2)(P2),300 kg/hm^(2)(P3)and 450 kg/hm^(2)(P4),and the nitrogen and potassium fertilizer application amounts were the same for each treat⁃ment.The physical and chemical indexes of soil moisture content,temperature,bulk density,pH,conductivity and organic matter at the cotton bell stage were determined,and the bacterial diversity and structural composition of soil layers with different phosphorus application levels of 0-20 cm were analyzed by high⁃throughput sequencing technology.【Result】Phosphorus application could reduce pH and conduc⁃tivity content.Different phosphorus treatments had no great effect on soil bulk density and soil moisture content.Different phosphorus appli⁃cation levels had significant effects on soil organic matter content and temperature,reaching the highest at P2.In the bacterial community structure,2 dominant bacterial phyla were Proteobacteria and Actinomycetes,3 dominant bacterial classes wereγ⁃Proteobacteria,α⁃Proteobacteria andβ⁃Proteobacteria,2 dominant bacterial orders were Pseudomonas and Rhizobia,2 dominant bacterial families were Pseudo⁃monas and Bradyrhizobia,and 4 dominant bacteria genera were Sinobium,Bradyrhizobium,Streptomyces and Glycopolyspora.The number of OTU and Chao1 index processed by P2 were 4702 and 6217.79 respectively,both of which were the highest.The results indicated that phos⁃phorus addition could increase the richness and diversity of soil bacterial community.The relative abundances of 3 phyla(Actinomycetes,Proteobacteria,and Pontomyces)and 2 genera(Bradyrhizobium and Streptomyces)with phosphorus solubility increased significantly with the application of phosphorus fertilizer.The results of RDA analysis showed that soil pH,conductivity,organic matter and bulk density were positively correlated with Actinobacteria and negatively correlated with Proteobacteria.【Conclusion】Compared with non⁃application of phos⁃phorus fertilizer,the application of phosphorus fertilizer can significantly increase soil temperature,organic matter and the relative abundance of dominant bacterial groups(Planctomycetes,β⁃Proteobacteria,Bradyrhizobium and Streptomyces),and reduce soil pH and conductivity.Among them,the soil temperature,organic matter andαdiversity of P2 treatment are significantly increased,and the electrical conductivity is significantly decreased,which can effectively improve the soil ecological environment and soil fertility.