Location: Sugarcane Research
2020 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
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.
Objective 1.A., ARS researchers at Houma, Louisiana, quantified sugarcane yield and crop residue returns in conventional, single-planted, and a wide-row, double-planted production system under naturally occurring rainfall conditions (e.g., no irrigation) for the second year’s field trials. The wider rows are more intensive, with 50% more linear cane per row. In each experiment, ARS researchers at Houma, Louisiana, monitored soil moisture changes continually using probes inserted into the soil at different depths (Milestone 1). Objective 1.B., ARS researchers at Houma, Louisiana, measured soil respiration throughout much of the growing season (March to October) using a long-term chamber developed by Li-Cor biosciences (Milestone 2). Objective 2, ARS researchers at Houma, Louisiana, continued to collect data from two eddy covariance towers to quantify carbon and water flux in the conventional sugarcane production system as well as an adjacent farm with wide-row, more intensive sugarcane production system. (Milestone 3). Flux data is currently being processed by collaborators at the University of Arkansas.
ARS researchers at Houma, Louisiana, continue work with the Long-Term Agroecosystem Network (LTAR) Lower Mississippi River Basin site. Two ARS researchers from Houma, Louisiana, participated in the 2020 LTAR Annual Meeting (virtual) in April 2020. Data from Objective 1.A. and 2 are being used to meet requirements for the Common Experiment, with both business as usual (conventional tillage and fallowing) and aspirational (reduced tillage, cover crops, chemical fallowing) production practices being investigated.
A third tower was added by ARS researchers at Houma, Louisiana, to sugarcane flux network in March 2020 at the Louisiana State Univeristy AgCenter Sugar Research Station in St. Gabriel, Louisiana. The tower is collecting climatic and flux data within a continuous sugarcane footprint located about 60 km north of the flux towers located near Houma, Louisiana.
Accomplishments
1. Legume cover crop impacts on sugarcane production. Sugarcane is a commercially important crop in Louisiana, Florida, and Texas, and the sugar produced is worth over $1 billion U.S. dollars annually. However, monoculture sugarcane production can degrade soils by reducing soil organic matter and enabling soil pathogenic microorganism proliferation. Therefore, cultural practices that improve sugarcane sustainability are needed to maintain yields in fields with degraded soils. Legumes, plants capable of producing their own nitrogen, can be grown as green manures to improve soil health during the normal fallow period between sugarcane crops. ARS scientists at Houma, Louisiana, in collaboration with scientists at Louisiana State University AgCenter and Alma Plantation, completed multi-year and location trials that investigated how sunn hemp and cowpea cover crops affected subsequent sugarcane yields. On average, the cover crops provided 4.3 tons per acre of dry biomass, and 200 pounds per acre of nitrogen. Cowpea generally improved subsequent plant cane yields, but the effects of sunn hemp varied. However, neither cowpea nor sunn hemp reduced cane or sucrose yields consistently in subsequent sugarcane crops. Legume cover crops should be viewed as an important component of sustainable sugarcane production practices. The practice is being implemented by growers in several parishes in Louisiana.
2. Sugarcane post-harvest residue production as a bioenergy feedstock. Sugarcane is the world’s largest biomass crop and is an enormously valuable component to sustainable, renewable energy production. The residue, or the extra leaf matter remaining after harvest, is often burned. But it can be used as a sustainable feedstock for bioenergy companies. However, information on how the quality of residue changes over time, and how residue can vary between sugarcane varieties, is limited. Therefore, ARS scientists in Houma, Louisiana, conducted a multi-year trial to determine residue quality of three commercial sugarcane varieties over the course of multiple harvest seasons. Sugarcane crops produced nearly two tons of dry biomass per acre per year. The average lignin, cellulose, hemicellulose, and ash content of residue were 4.7, 36.0, 31.5, and 0.7%, respectively. Variety affected biomass, lignin, cellulose, hemicellulose, and ash yield, indicating there is some genetic variation in residue. Overall lignin concentrations in sugarcane residue were low. Both residue yield and quality changes over time within a season were consistent with the three sugarcane varieties investigated in this study. Thus, sugarcane harvest can be focused on varieties with the greatest sucrose concentration, knowing that residue quality is stable across varieties. This can potentially impact growers by providing a new revenue stream.
3. Crop residue management improves water quality. A substantial amount of sugarcane leaf material, or crop residue, is left on the soil surface when sugarcane is harvested each year. The crop residue creates a mulch layer that prevents soil from drying or warming quickly in the spring, which can slow spring sugarcane crop growth and decrease cane and sucrose yield. The current best management practice is to burn the residue. But, burning is increasingly difficult due to urban encroachment. Many growers recognize the importance of the mulch layer to improving soil organic matter and retaining nutrients, as well as reducing soil erosion. Therefore, ARS researchers at Houma, Louisiana, evaluated the effect of residue management (mulch, burn, or sweeping into row furrows) sediment and nutrients in runoff as well as crop yields. Cane and sugar yields were similar regardless of residue treatment. Runoff was lowest in mulch fields, followed by burn, and swept fields. The results indicate that sugarcane growers can minimize soil and nutrient losses associated with runoff by retaining the mulch layer, and under the test conditions, expect similar yields with sweep or mulch residue management.
Review Publications
White Jr, P.M., Hoy, J.W., Gravois, K.A., Waguespack, H.L., Webber III, C.L. 2019. Chemical treatments improve billet-planted cane growth and crop yields under temperate climatic conditions. Journal of the American Society of Sugar Cane Technologists. 39:12-24.
Spaunhorst, D.J., Orgeron, A.J., White Jr, P.M. 2019. Burning post-harvest sugarcane residue for control of surface-deposited divine nightshade (Solanum nigrescens) and itchgrass (Rottboellia cochinchinensis) seed. Weed Technology. 33(5):693-700. https://doi.org/10.1017/wet.2019.65.
Selim, H.M., Elbana, T., White Jr, P.M., Arceneaux, A., Tubana, B. 2019. Sediment and nutrient loading from sugarcane fields in south Louisiana: Effect of residue management. Journal of Soil and Water Conservation. 74(5):477-486. https://doi.org/10.2489/jswc.74.5.477.
White Jr, P.M., Williams, G., Viator, H., Viator, R.P., Webber III, C. 2020. Legume cover crop effects on temperate sugarcane yields and their decomposition in soil. Agronomy. 10(5):703. https://doi.org/10.3390/agronomy10050703.
Yu, P., Huang, L., Li, Q., Lima, I.M., White Jr., P.M., Gu, M. 2020. Effects of mixed hardwood and sugarcane biochar as bark-based substrate substitutes on container plants production and nutrient leaching. Agronomy. 10(2):156. https://doi.org/10.3390/agronomy10020156.
