2010 Annual Report
1a.Objectives (from AD-416)
The first objective of the research is to develop new crop and soil management techniques for sugarcane production that overcome limitations in soil and nutrient resources and maximize production efficiency. These techniques will incorporate elements of precision agriculture and remote sensing. The second objective of the research is to identify methods to mitigate the current yield loss associated with post-harvest residue retention and ripener usage in sugarcane production.
1b.Approach (from AD-416)
To address the first objective, a series of experiments will be initiated to investigate the response of sugar and energy-canes to variations in macro- and micronutrients. Results from these experiments will be used to identify critical fertility components and to optimize fertility rates for both sucrose and biomass production. Initial macro-nutrient experiments will focus on nitrogen (N), a critical component of a sugarcane fertility program whose cost has risen dramatically. Initial micronutrient experiments will focus on nickel (Ni) a nutrient that is associated with increases in disease resistance and copper (Cu) which is associated with increases in both cane and sugar yields and may also influence disease resistance. In addition, experiments will be conducted on commercial farms to investigate the utility of electrical conductivity (EC) and soil pH mapping, zone sampling, and variable-rate (VR) application techniques to optimize nutrient availability. All treatments will be arranged in randomized complete block design (RCBD) with six replications. Finally, we will investigate the utility of a newly designed yield monitor and leaf reflectance measurements, from multi-band aerial imagery and from direct hyperspectral measurement as potential indicators of cane biomass levels and sucrose content and to identify crop stresses associated with improper fertility levels of sugarcane dedicated for either sugar or bioenergy. To address the second objective, studies will be initiated to investigate the carry over response of sugar- and energy-cane crops to post-harvest residue and ripener applications made in the previous crop year. The response of energy-canes and newly-released sugarcane varieties to these factors has not been tested. In addition, studies will be implemented to screen basic and commercial germplasm for tolerance to post-harvest residue retention and to screen for self-defoliating clones that may expedite the natural decomposition of leafy residue prior to harvest. Finally, a study will be initiated to investigate in crop N application rate effects under various post harvest residue management schemes to include: partial removal, complete removal by burning, and no removal.
Project receives support from the American Sugar Cane League (6410-21000-014-04T) through a Trust Fund Cooperative Agreement, “Improving Sugarcane Production Efficiency”. Additional details of research can be found in the reports of the subordinate and parent projects.
First–ratoon nitrogen trials were initiated and sites for repeated plant-cane trials were also located and treatments applied. Leaf samples will be collected for reflectance and nitrogen analysis in July and cane and sugar yields will be determined by harvesting the experiments in November and December 2010. All plant-cane nitrogen experiments from the first year were harvested in November and December, 2009. Preliminary results suggest that Louisiana sugarcane growers could save money by reducing nitrogen rates in both plant and stubble crops, while maintaining crop yields. The energy cane variety L 79-1002 did not exhibit a response to nitrogen, which is encouraging since energy cane is intended to be produced with reduced inputs.
Studies initiated to determine the influence of nickel (Ni) and copper (Cu) fertilizers on cane and sugar yields and also on the incidence of sugarcane diseases, particularly brown rust, were repeated in 2010. Rust and other disease levels are being monitored through visual ratings and by taking leaf samples and determining percent rust lesions with image analysis software. Cane and sugar yields will be determined by harvesting plots in November and December, 2010. All Ni and Cu studies from the first year were harvested in November and December, 2009. Preliminary results with both Ni and Cu suggested positive, although not significant, yield effects. Initial yield monitor data was collected on commercial sugarcane farms in the fall of 2009 and preliminary results indicated that the system was effective at predicting and mapping cane yields.
An experiment that evaluated the interaction of glyphosate carryover and residue management was initiated. Preliminary data indicate that the stresses of glyphosate carryover and full residue retention appear to compound each other as indicated by reductions in stalk number and stalk height during early growth stages. Other studies were initiated to screen both basic and commercial germplasm to identify clones tolerant to the cool, wet conditions caused by the retention of post-harvest residues and to determine if self-defoliating varieties could be used as an alternative to burning. Cane quality was assessed by determining the amount of leaf trash in the sample. A study was also initiated to determine if additional nitrogen applied to different alternative methods of residue management would produce yields equivalent to where the residue was removed by burning. Full retention of residue reduced shoot counts and photosynthetic rates compared to where the residue was burned. Sites for 2010 planting have been identified and are currently being prepared for planting in the early fall.
Early Harvest Affects Ratooning Ability in Louisiana. The number of sugarcane processors in Louisiana has decreased over time forcing growers to begin the harvest season earlier for fear of complete cane loss at the end of the harvest period due to freezing temperatures. Experiments were conducted to investigate effects of early harvest on ratooning ability and to determine differential effects of early harvest among Louisiana varieties. Averaged across all varieties, the October harvest of plant-cane reduced sugar yields of the first-ratoon (7,700 kg/ha) compared to the mid-season harvest date (10,100 kg/ha.) Averaged across all varieties, the October harvest of both plant-cane and first-ratoon reduced sugar yields of the subsequent second-ratoon (5,500 kg/ha) compared to the December harvest (10,000 kg/ha). Both harvest dates for L 97-128 had equivalent yields, so this variety is best suited for early harvest if only harvested early once in a four-year cycle. All cultivars had decreased yields with consecutive years of early harvests. When developing harvest schedules, growers should consider the potential 24 to 45% yield loss in subsequent ratoons associated with the early harvest of plant-cane and first-ratoon crops.
Leaf Reflectance Provides an Estimate of Sugarcane Sucrose Levels. Current methods used to estimate sugarcane stalk sucrose levels prior to harvest are labor and time intensive. Reflectance data ware collected from the leaves of predominant sugarcane varieties that were sampled throughout the harvest season (during the 2005 and 2006 crop years) to determine sucrose accumulation (maturity). Leaf reflectance was effective at predicting sucrose in 36 to 79% of the cases if varieties were combined, and in 65 to 100% of the cases if the varieties were considered separately. Regression analyses also identified several spectral regions that appeared to be important in describing stalk sucrose levels, including: ultraviolet, blue, green and yellow, orange and red, and the near-infrared wavelengths. These combined results indicate that it may be possible to utilize remote sensing techniques to estimate sugarcane maturity prior to harvest which would allow growers and mills to more effectively manage field and varietal harvest schedules to insure maximum sucrose yields.
Johnson, R.M., Richard Jr., E.P. 2010. Variable rate lime application in Louisiana sugarcane production systems. Precision Agriculture. 11:464-474. DOI: 10.1007/s11119-009-9140-2.
Viator, R.P., Dalley, C.D., Johnson, R.M., Richard Jr, E.P. 2010. Early harvest affects ratooning ability in Louisiana. Sugar Cane International. 28(3):123-127.