Proximity to subsurface drip irrigation emitters altered soil microbial communities in two commercial processing tomato fields

Abstract

Subsurface drip irrigation (SDI) systems that deliver on-farm water savings can alter soil physico-chemical properties and reduce yields of processing tomatoes (Lycopersicon esculentum Mill). We hypothesized that soil microbial communities will also be modified with proximity to SDI emitters. Bacterial and fungal alpha and beta diversity were analysed using soil samples near to (within 15 cm) and distant from (45 cm laterally) SDI emitters in two adjacent fields used for commercial processing tomato production. One field had an established SDI system and four seasons of cropping under irrigation while the second field had a recently installed SDI system and one season of cropping. Bacterial diversity was significantly reduced near the emitter only in the recent SDI field. Bacterial community structure was also determined by proximity to the emitter in both fields. Several bacterial genera contributed to the dissimilarity of communities near and distant from the emitter including Acidobacteria subgroups 3 and 6, Gaiella, Gemmatimonas and Flavobacterium. Fungal alpha diversity was not significantly affected by emitter proximity in the two fields though it was lower overall in the established SDI field. Fungal community structure was also significantly different based on emitter proximity in both fields. Several fungal genera that contributed to the dissimilarity of communities near and distant from the emitter including Glomus, Preussia, Embellisia, Podospora, Gibberella and Plectosphaerella. Redundancy analysis identified pH, available phosphorus (Colwell P), potassium and magnesium as predictors of bacterial and fungal community structure in the two fields. This study has identified that SDI emitter proximity modifies the abundance of specific bacterial and fungal genera implicated in plant and soil health, thereby providing new information to improve the management of SDI systems for sustained yields of processing tomatoes.