Location: Coastal Plain Soil, Water and Plant Conservation Research
Project Number: 6082-13000-011-002-R
Project Type: Reimbursable Cooperative Agreement
Start Date: Jan 1, 2023
End Date: Dec 31, 2023
Objective:
Determine the effects of tillage and cover crop management, on the cotton rhizosphere’s ability to remain resilient, or rebound, in the face of drought stress.
Approach:
This work represents the first year of study focused on assessing the impacts of conservation tillage and cover cropping on drought tolerance in cotton root-associated microbial communities. The experiment is designed in plots located at the Coastal Plains Soil, Water, and Plant Research Center. This study's test field consists of three soil managements typically used by cotton growers: 1) conventional tillage; 2) conservation tillage; and 3) conservation tillage with cover crop. The cover crop is a blend of rye, crimson clover, and tillage radish. Managements are arranged in a randomized, complete block experimental design, with four replicates of each under the three described tillage managements and continuous cotton. The experiment was designed to document the early adaptation of microbial communities to these practices. To examine the influence of management on cotton drought tolerance, plastic sheeting will cover approximately a quarter of each plot (3 m x 5 m) and will be placed around cotton stems with the goal of inhibiting water infiltration four weeks before anticipated cotton flowering. These subplots will serve as a drought simulation. After flowering, the plastic sheeting will be removed, and drought stressed soils will be irrigated to examine microbial responses. At the same time, additional 3 m x 5 m subplots will be established diagonally to the drought simulation subplots and will receive a minimum of 2” of water each week either by irrigation or rain-fed. Time-domain reflectometry (TDR) sensors and temperature loggers will be placed in the top 5 cm in each subplot to measure soil moisture and temperature respectively in 60-minute increments. Microbiological analyses will be performed on bulk and rhizospheric soil samples. Phospholipid fatty acid (PLFA), for bacterial community analysis of bulk and rhizospheric soils will be used to determine microbial biomass. Microbial activity, from both bulk and rhizospheric soils, will be measured using a combined soil enzyme assay. Drought stress subplots will be used to determine how quickly microbial populations reach original activity levels (microbial rebound) by measuring substrate-induced respiration (SIR) and fluorescein diacetate (FDA) hydrolysis twice weekly for two months post-irrigation. To determine if the microbial communities are easy to perturb (microbial resistance) and determine how quickly microbial composition recovers (microbial resiliency) after drought-like conditions, bulk soil samples will be taken immediately before and after, installation of the plastic sheeting, weekly for the first two months, and then monthly until the start of the next growing season, both from drought simulated, and non-drought simulated portions of each plot. The DNA will be extracted from these samples, and microbial diversity will be analyzed using high-throughput DNA sequencing. To measure microbial resiliency, root-associated microbial populations (both bacterial and AMF) will be compared annually.
