Impact of deficit irrigation and organic amendment on soil microbial populations and yield of processing tomato

Authors: RODRIGUEZ-RAMOS, JEAN - University Of Oklahoma; TURINI, THOMAS - University Of California Agriculture And Natural Resources (UCANR); Wang, Dong; Hale, Lauren

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2022
Publication Date: 8/10/2022
Citation: Rodriguez-Ramos, J.C., Turini, T., Wang, D., Hale, L.E. 2022. Impact of deficit irrigation and organic amendment on soil microbial populations and yield of processing tomato. Applied Soil Ecology. 180. Article 104625. https://doi.org/10.1016/j.apsoil.2022.104625.
DOI: https://doi.org/10.1016/j.apsoil.2022.104625

Interpretive Summary: In response to water scarcity, deficit irrigation (DI) strategies can reduce irrigation inputs at non-critical times for crop productivity, but may also impact soil microorganisms that are important for nutrient cycling and promote plant health. This study evaluated the capacity of biochar with and without compost to buffer the impacts of DI treatments (50% and 75% of full irrigation regimes) on soil microbial communities and tomato quality and yield. Bacterial/archaeal community composition diverged more in response to DI than to soil organic amendments. However, in contrast to the 50% DI treatment the 75% treatment posed less of an impact on microbial community structure and the abundances of soil microbial groups and did not reduce tomato yield, irrespective of soil amendment. Overall, our results provide insight that moderate DI can be a sustainable strategy for crop production in water-scarce years.

Technical Abstract: Projected changes in precipitation patterns, together with increased water demands from urban, industrial, and environmental needs can reduce the volume of irrigation water available for agriculture. Strategies that reduce irrigation water inputs, e.g., deficit irrigation (DI), need further evaluation to determine potential impacts on yield and soil microbial communities, driving critical soil biogeochemical cycles supporting plant nutrition. Also, it is currently unknown whether and how organic soil amendments can stabilize the effects DI has on microbial communities. For two growing seasons, we profiled soils in processing tomato beds either unamended or amended with a one-time application of biochar or biochar with compost and irrigated using each of three regimes: full, at 100% of plant water demand, or DI treatments at 75% or 50% of 100% irrigation. Soil bacterial/archaeal community compositions, their C and N metabolic potentials, and biomass of microbial groups were determined based on high throughput sequencing of 16 rRNA genes and phospholipid fatty acid analysis. We tested the discrete and interactive effects of DI and soil amendments on soil chemistry, soil biological properties, and crop yield. Relationships among these parameters were determined using correlation analysis. Bacterial/archaeal community composition diverged more in response to DI than to soil organic amendments. However, 75% DI did not strongly affect bacterial/archaeal community composition or the total and individual biomass of microbial groups, conditions that also increased irrigation water productivity based on marketable yield. Although soil amendments did not stabilize the compositional shifts induced by DI, four to five years from their incorporation, their recalcitrant C still had residual effects on the bacterial/archaeal community composition. Furthermore, DI augmented the amendments’ C and N soil residence time, possibly through negative effects on the C and N metabolic potential of the bacterial/archaeal community. Overall, our results provide insight into water-saving mechanisms that could increase profit margins in water-scarce years without affecting microbial populations that support plant growth and productivity.