Effects of subsurface drip irrigation on alfalfa (Medicago sativa L.) growth and soil microbial community structures in arid and semi-arid areas of northern China

Abstract

Water shortage is a common environmental stressor encountered by agricultural production in arid and semiarid areas of the world. Under this situation, the impacts of different irrigation methods on the forage yield, select soil physiochemical properties, and soil microbial community structures were identified after alfalfa was planted for three years in Ningxia, northern China. The experiment consisted of five irrigation methods/treatments with three replicates for each treatment, including flood irrigation (FL), sprinkler irrigation (SP), and three subsurface drip irrigation systems, with drip tapes buried at a depth of 10 cm (SSL), 20 cm (SSM) and 30 cm (SSD). The results showed that all water-conserving irrigation methods increased the soil water content compared with FL, but only SSM and SSD presented higher potential in increasing alfalfa yield by improving soil water content, pH value and available P. Moreover, compared with FL, SSM and SSD also presented greater effects in altering microbial community structures, such as the α-diversity, β-diversity, and bacterial composition at the order level, but did not significantly affect microbial taxon composition at the phylum level. Among all determined parameters, alfalfa yield was detected as the strongest factor, which simultaneously associated with the bacterial and fungal community composition, α-diversity, and β-diversity. Moreover, the abundance changes of predicted microbial functional genes revealed that improved alfalfa growth also resulted in more nutrient exhaustion and organic matter depletion in those soils under SSM and SSD treatments. In addition, the changes in bacterial community structure were more sensitive than those in the fungal community structure to soil physicochemical properties and alfalfa growth. In conclusion, the SSM and SSD treatments have great potential to improve alfalfa growth and alter soil microbial community structures in the arid and semiarid areas of northern China.