The Effect of Long-Term Continuous Cropping of Black Pepper on Soil Bacterial Communities as Determined by 454 Pyrosequencing.

Wu Xiong,Chao Xue,Hongjun Liu,Rong Li,Qirong Shen,Huasong Wu,Zhigang Li,Ruifu Zhang,Wenju Liang

doi:10.1371/journal.pone.0136946

Abstract

In the present study, 3 replanted black pepper orchards with continuously cropping histories for 10, 21, and 55 years in tropical China, were selected for investigating the effect of monoculture on soil physiochemical properties, enzyme activities, bacterial abundance, and bacterial community structures. Results showed long-term continuous cropping led to a significant decline in soil pH, organic matter contents, enzymatic activities, and resulted in a decrease in soil bacterial abundance. 454 pyrosequencing analysis of 16S rRNA genes revealed that the Acidobacteria and Proteobacteria were the main phyla in the replanted black pepper orchard soils, comprising up to 73.82% of the total sequences; the relative abundances of Bacteroidetes and Firmicutes phyla decreased with long-term continuous cropping; and at genus level, the Pseudomonas abundance significantly depleted after 21 years continuous cropping. In addition, bacterial diversity significantly decreased after 55 years black pepper continuous cropping; obvious variations for community structures across the 3 time-scale replanted black pepper orchards were observed, suggesting monoculture duration was the major determinant for bacterial community structure. Overall, continuous cropping during black pepper cultivation led to a significant decline in soil pH, organic matter contents, enzymatic activities, resulted a decrease in soil bacterial abundance, and altered soil microbial community membership and structure, which in turn resulted in black pepper poor growth in the continuous cropping system.

Highlights

Soil microbial communities are responsible to soil functions and the ecosystem sustainability [1,2]
The soil pH and organic matter (OM) content deceased with the long-term continuous cropping of black pepper, while the available N and available P contents increased overtime (Table 1)
Knowing the characteristics of soil physicochemical properties and enzyme activities in black pepper continuous cropping systems could be helpful to provide a better understanding of soil productivity in replanted black pepper orchards

Summary

Introduction

Soil microbial communities are responsible to soil functions and the ecosystem sustainability [1,2]. Many previous studies have shown that soil microbial community membership and structure are key determinants on soil health and can be affected by various agricultural management factors, including crop rotation and tillage [3], fertilizer regime [4], pesticide application [5], irrigation [6], and continuous cropping [7]. Long-term continuous cropping usually leads to plant growth inhibition and serious soil-borne diseases [13,14], which has been described as a continuous cropping obstacle ( known as replanting disease). Long-term continuous cropping causes poor growth, low yield, and serious soil-borne disease [16], severely hindering the black pepper industry in China

Methods

Results

Conclusion