Effects of polyacrylamide and biochar co-application on soil bacterial community, physical and chemical factors, and maize yield

Abstract:

[Background] Bacterial community plays an important role in soil nutrient cycling and meanwhile is affected by soil physical and chemical properties and crop yield. [Objective] To study the effects of co-application of polyacrylamide (PAM) and biochar on soil bacterial diversity and community structure, soil physical and chemical factors, and maize yield in Hetao irrigation area under drip irrigation. [Methods] We designed four treatments: control (CK, no polyacrylamide or biochar), 22.5 kg/hm² polyacrylamide+9 000 kg/hm² biochar (PB1), 22.5 kg/hm² polyacrylamide+ 13 500 kg/hm² biochar (PB2), and 22.5 kg/hm² polyacrylamide+18 000 kg/hm² biochar (PB3), to investigate the relationship among soil bacterial community, environmental factors, and maize yield by high-throughput sequencing technology. [Results] Compared with CK, PB1 and PB2 improved the alpha diversity indexes (Chao 1 and Shannon index) of soil bacteria. The co-application of polyacrylamide and biochar changed the structure of soil bacterial community, and the dominant groups of soil bacteria in different treatments were Proteobacteria and Subgroup_6. PB1 and PB2 significantly increased the content of available nitrogen and available potassium, respectively, and the comprehensive soil fertility was the highest in PB2 treatment. Redundancy analysis showed that pH was the main environmental factor affecting the bacterial community structure at the phylum and genus levels. The ear length, bald tip length, kernel number per row, and 100-kernel weight of maize in PB2 treatment were the highest. Actinobacteria, Subgroup_6, and RB41 played a positive role in increasing the kernel number per row, and Skermanella in increasing the ear length. [Conclusion] Under drip irrigation, co-application of polyacrylamide and biochar can directly or indirectly increase bacterial diversity and alter bacterial community structure by changing soil physical and chemical properties to improve maize yield, and PB2 treatment demonstrates the best performance.