Location: Sugarcane Research
2022 Annual Report
Objectives
1. Measure and model water-driven processes in agricultural production systems to predict and enable production under constrained conditions that affect ecosystem services.
1.A. Measure sugarcane growth, yield (tons and sugar), and residue in conventional (1.8 m) and wide row (2.4 m) production systems under ambient water conditions.
1.B. Identify field properties and utilization of resources that vary between row spacing including soil carbon and soil moisture content.
2. Measure and model fluxes of water and carbon in these systems and how they are affected by management practices.
Approach
Use field experiments to study the effects of water availability on sugarcane establishment, growth, and yield, and how row spacing-induced changes to water availability and crop physiology affects carbon cycling within the soil, plant, and atmosphere continuum. Laboratory experiments will evaluate how post-harvest crop residue, the largest soil carbon input in these field systems, cycling is impacted by the effects of water, temperature, mineral nutrients, and particle size.
Progress Report
This is the final report for project terminating in 2022 and replaced with 6052-13210-003-000D, Water and Soil Resources in Sustainable Sugarcane Production Systems for Temperate Climates. Milestones were met on both objectives and their subobjectives - all of which fall under National Program 211, Problem Area 4, Watershed Management to Improve Ecosystem Services in Agricultural Landscapes, Sub-heading C, measure and predict water-driven agroecosystem productivity and other ecosystem services.
The more intensive wide row configuration did not result in increased sugarcane yields or crop residue when compared to the traditionally spaced rows in the duplicated, replicated field trials completed in 2020. Yields were comparable for both cultivars evaluated (HoCP 04-838 and L 01-299). Results were published in 2021 in the Journal of the American Society of Sugar Cane Technologists (Volume 41, pp. 18-25) (Objective 1.A). The wider row spacing resulted in a greater amount of soil moisture available for plant growth, when compared to traditional row spacing. This is possibly due to the reduced number of wheel (drain) furrows in the wider row system, with more acreage being used for cane growth, when compared to the traditional system. However, neither row spacing experienced periods of drought in this water abundant region. The results were published in Agronomy MDPI in 2022 (Volume 12 online) (Objective 1.A).
Crop residue decomposition kinetics were evaluated in laboratory experiments at three temperatures (11, 25, and 33°C) and three soil moisture levels (within the range observed for nearby sugarcane fields). Increased temperature and moisture resulted in more rapid crop residue decomposition. Thus, moderate field conditions (no extremely low temperatures or saturated soil conditions) should result in sufficient crop residue decomposition to limit detrimental effects on ratoon cane yields. Results were published in 2017 in Sugar Tech (Volume 20, Issue 5, pp. 497-508) (Objective 1.B). Soil respiration measurements were completed for both row spacing systems and the data are currently being processed. Carbon flux data derived from the eddy covariance towers were used to compare sugarcane to various other crops grown in the U.S., including cotton, rice, soybean, wheat, and alfalfa as part of the Long-Term Agroecosystem Research network. Overall sugarcane resulted in the greatest net carbon uptake observed among the cropping systems. Results have been submitted to Agricultural & Forest Meteorology for publication (Objective 2).
Overall yield, carbon flux, and water use differences were minimal between the two row spacing systems used in Louisiana sugarcane production. However, sugarcane proved to be an excellent crop to sequester carbon and produce economical returns for growers under hot, humid conditions typically observed in Louisiana. Future climate change predicts increased rainfall and higher temperatures. Our future research will focus on selecting varieties that grow well, produce high yields, and display more efficient photosynthesis under these elevated moisture and temperature conditions.
This research directly impacts the Louisiana sugar industry because it is the first report of replicated field plot cane and sucrose yields. Economist will soon identify cost savings between the different row spacing systems using the data. The carbon flux measurements by eddy covariance are the first in Louisiana sugarcane. Collaborators use the data to calibrate plant growth models and in synthesis publications about carbon budgeting involving different U.S. row crops. Consultants use the data to estimate carbon sequestration to forecast potential carbon credits associated with Louisiana sugarcane. Louisiana sugarcane is one of a few ecotones in the U.S. with abundant water resources. Scientists created a new group within the Long-Term Agroecosystem Research (LTAR) network to study these water abundant agricultural areas.
Accomplishments
1. Optimizing row spacing can improve yields when sunlight and water are limited. Sugarcane (Saccharum spp.) is the world’s largest biomass crop producing over thirty tons per acre each year in Louisiana and sequesters high levels of carbon dioxide (CO2), an important greenhouse gas. Sugarcane in Louisiana is normally grown on rows spaced 1.8 m apart, but interest in planting on 2.4 m rows is increasing. In this study, ARS researchers in Houma, Louisiana, hypothesized that wider row spacing results in greater water availability due to a decrease in the number of field drains with wider rows. Soil moisture sensors were placed at three depths in fields planted on 1.8 and 2.4 m row spacings with two commercial sugarcane varieties. Soil moisture was monitored over three years. Yields in the two row spacings were similar. As expected, the soil water content was greater in the wider rows (2.4 m), when compared to the normal-spaced rows (1.8 m). However, in both row spacings, plant-available water was always present in the top 45 cm, even during periods of low rainfall. Potentially, high water availability provides an opportunity to increase photosynthesis in sugarcane varieties by selecting for greater photosynthetic capacity and CO2 uptake through increased stomatal conductance. This in turn could increase crop yield and sequestration of carbon.
2. Plants remove carbon dioxide from the atmosphere to produce biomass, a process known as gross primary production. Researchers need to estimate it accurately to understand the agricultural carbon cycle and how it relates to climate change. Multiple plant growth models are available; however, most are coarse (low to moderate spatial resolution) and are not crop specific. The research paired carbon dioxide measurement towers in Louisiana, USA, and Sao Paulo, Brazil, sugarcane fields with different satellite images obtained from NASA to calibrate plant growth models across spatial resolutions. The NASA satellite images were from the Moderate Resolution Imaging Spectroradiometer (MODIS) at 500 m resolution; Landsat at 30 m resolution; and Sentinel-2 at 10 m resolution. Results indicated that plant growth models estimated using each type of satellite image correlated well with measurements obtained from gas towers. These site-level analyses provide a foundation for constructing plant growth models using satellite images at the field scale over many parts of the U.S. and world.
3. Biochar, a carbon-rich solid formed by pyrolysis of excess bagasse, can be added as a soil amendment to improve agronomic yields. However, the impacts can range from negative to positive and the majority of research is based on large application rates that may not be economically feasible (over 13 tons per acre). ARS researchers in Houma, Louisiana, demonstrated the effects of sugarcane byproduct-derived biochar to soil chemical and physical properties, and crop yield, when applied at rates of less than 1 ton per acre. Cancienne silt loam (Schriever), Coushatta silt loam and silty clay loam (Bunkie), Schriever clay (Cade), and Loreauville silt loam (St. Martinville) with and without biochar (0.4 or 0.7 tons per acre) were incubated for 4 weeks prior to soil chemical evaluation. Soil chemical properties were not affected by the addition of these rates of biochar. A second laboratory study evaluated the effects of biochar (0.7 tons per acre) on Cancienne silt loam over a range of moisture content. Soil osmotic and matric water potential was not affected by biochar. A field experiment was conducted on Cancienne silt loam between 2013 and 2017 using 0.4 or 0.7 tons of biochar per acre applied at planting to commercial sugarcane (HoCP 96-540). Cane and sucrose yields were less affected by biochar addition in the plant cane and first ratoon crop; however, more impacts were observed in the second and third ratoon crops. Over the crop rotation biochar increased cane and sucrose yield by 17% and 20%, respectively. More field research is needed to confirm these results. Overall, biochar applied at economical rates had the least impact on soil water potential, when compared to soil chemical properties and yield.
