Impacts of organic fertilization with a drip irrigation system on bacterial and fungal communities in cotton field

Abstract

The objective of this field study was to determine the effects of continuous four years of chemical fertilizer (CF) and organic fertilizers (i.e., cattle manure (CM), biofertilizer (BF)) application on soil bacterial and fungal communities (abundance, structure and diversity) in drip irrigated cotton (Gossypium hirsutum L.) field of the Xinjiang Autonomous Region in Northwest China. The six treatments were (i) unfertilized, (ii) only CF, (iii) 80% CF plus 3000 kg·ha−1 CM, (iv) 60% CF plus 6000 kg·ha−1 CM, (v) 80% CF plus 3000 kg·ha−1 BF and (vi) 60% CF plus 6000 kg·ha−1 BF. The 454 high-throughput sequencing approach and real-time quantitative PCR (qPCR) method were used to study the characteristics of soil bacterial and fungal communities. The combined application of 60% CF and organic fertilizers (especially BF) significantly increased the richness (Chao1 and Ace index) and α-diversity (Shannon index) of bacterial community (P < .05) but decreased those in fungal community compared to CF application alone. The 60%CF plus 6000 kg·ha−1 BF treatment had the highest bacterial abundance, whilst the CF treatment had the greatest fungal abundance. The soil receiving 6000 kg·ha−1 organic fertilizers had a greater bacteria/fungi ratios than that receiving 3000 kg·ha−1. The cotton yields were positively correlated with bacterial community (richness, diversity and abundance; P < .05) but not fungal community (P > .05). RDA analysis showed that soil organic carbon (SOC), pH and ammonium (NH4+) played the important role in shaping bacterial and fungal community structure after four-year's fertilization. Overall, organic fertilization (especially biofertilizer addition) could be considered as a sustainable practice for establishing healthy soil microflora (bacterial-dominated type) and subsequently improving the soil quality and crop production in drip irrigation agriculture.