Location: Sugarcane Research
2024 Annual Report
Objectives
Objective 1: Determine and evaluate critical water efficiency optimization parameters that impact sugarcane crop production systems in temperate environments.
Sub-objective 1.A: Improve crop coefficients for reference ET models that are reliable along the sugarcane life cycle and across sugarcane growing areas in U.S. with differing climatic zones and water regimes, including deficit and excess-water conditions.
Sub-objective 1.B: Improve ET models for water management at field to regional level by separating transpiration and soil evaporation fluxes using stable isotopes of hydrogen and oxygen in water.
Objective 2: Develop holistic stochastic optimization models and decision support tools to improve the sustainability of sugarcane production systems in temperate environments.
Objective 3: Evaluate and/or develop conservation best management practices that positively influence soil water and carbon cycling in sugarcane production systems in temperate environments.
Sub-objective 3.A: Characterize how long-term (16+ y) sugarcane crop residue management affects soil moisture storage, C sequestration, and crop yield.
Sub-objective 3.B: Characterize how new tillage and fallow cover cropping practices affect soil moisture storage, C sequestration, and crop yield.
Approach
Through greenhouse and field experiments, improve crop coefficients for reference evapotranspiration (ET) models that are reliable along the sugarcane life cycle and across sugarcane growing areas in U.S. with differing climatic zones and water regimes, including deficit and excess-water conditions; and Improve ET models for water management at field to regional level by separating transpiration and soil evaporation fluxes using stable isotopes of hydrogen and oxygen in water. Employ data collected in the field to populate DSSAT input modules to evaluate how changing climatic conditions will affect sustainable sugarcane production. Characterize how long-term (16+ y) sugarcane crop residue management affects soil moisture storage, carbon sequestration, and crop yield. Characterize how new tillage and fallow cover cropping practices affect soil moisture storage, carbon sequestration, and crop yield.
Progress Report
Year 2 of the new project has been productive. The mobile lab for housing the water isotope analyzer and multiplexer was built and prepared for measuring hydrogen and oxygen isotope composition in evapotranspiration in August and September in the field. To better understand the relationship between photosynthesis and transpiration in water use efficiency and the leaf level factors that affect water loss (transpiration and stomatal conductance) from the leaves, a survey of sugarcane genotypes was completed. This study highlighted the importance of stomatal behavior, regarding how quickly they reopen after a disturbance. The rate of reopening measured as as the time to reach maximum photosynthetic rate was found to be an important trait in both leaf level water loss and photosynthesis. As part of this study, carbon isotope composition of sugarcane leaves was found to be related to water use efficiency. These experiments are ongoing in a controlled environment to compare water use efficiency at the leaf and plant levels for further comparison to the measurements made in the field at the agroecosystem level. This year second ratoon roots were imaged in the minirhizotrons for part of the year. Unfortunately, malfunctioning equipment necessitated repairs that took considerable time to repair and resume imaging. So far nearly 40,000 images have been taken. Through a collaboration with a professor and graduate student at the University of Texas at Arlington, a computer method using deep learning and artificial intelligence is being developed to extract the roots from the soi background in the thousands of minirhizotron images and analyze various root traits. Using a stable isotope analysis, depth of water uptake by sugarcane was measured in the minirhizotron plots to compare to the presence of roots measured by minirhizotron imaging. To further understand the influence of soil texture on water source use, water source use was measured at sites having the two predominant soil types: a heavy clay and a silt loam. Last year was the first year of the study and proved to be a very dry year, which allowed for the measurement of water source use under drought conditions. This year the study is being repeated to measure depth of water uptake under more typical precipitation levels to compare to last year’s water source use under drought conditions. The expectation is that the depth of water uptake will be higher this year than last year where the sugarcane was taking water deep in the soil profile during the entire growing season. DSSAT templates were constructed from existing weather data. This involved redesigning the usual data management template to accommodate DSSAT entry requirements. This task is completed for weather data and is near complete for crop management and plant data templates. Entry of 2022-2023 data is on-going. Soil samples were collected and frozen prior to analysis for chemical parameters. This is pending determination of soil microbial analyses to be completed as part of the Long-Term Agro-ecosystem Research network collaborative project with Mississippi and Arkansas ARS scientists. Sugarcane harvest was complete and crop residue management was conducted. The second ratoon crop is growing and will be harvested in 2023.
Accomplishments
1. Measuring leaf level photosynthesis and water use efficiency. The purpose of the research was to create a link in water use efficiency across leaf, plant, and ecosystem scales. A necessary component of understanding the role of sugarcane plants in sugarcane agroecosystem is to determine the leaf and plant level relationship between photosynthesis and transpiration and stomatal conductance at the leaf level and between growth and water use at the plant level. Sugarcane had ample variation in photosynthetic rate, transpiration rate, and stomatal conductance across varieties to allow for selection of these traits. Additionally, this research showed the importance of the rate of stomatal closure and reopening in total photosynthesis and water loss in that leaves with stomates that quickly reopened after disturbance had greater photosynthesis but not water loss than leaves with stomates that slowly reopened after disturbance. Therefore, in humid Louisiana, stomates that are slow to close during disturbances and quickly reopen following disturbance maintain greater photosynthesis, and this is a potential trait for increasing photosynthesis in sugarcane. This study showed that stomatal conductance was the principal factor regulating water use efficiency in sugarcane, but photosynthetic capacity has a minor effect as well. Therefore, this study showed that water use efficiency in sugarcane can be increased by a combination of selecting for lower stomatal conductance and higher photosynthetic rates, and stable isotopes of carbon can be used as a more rapid measure of long-term water use efficiency.