2013 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.
All first- and second-ratoon nitrogen experiments from the fourth year were harvested in October and November 2012. The combined data from all nitrogen experiments clearly show that Louisiana sugarcane growers could save money by reducing nitrogen rates in both plant and stubble crops, while maintaining crop yields. This addresses the first project objective, which is to develop new crop and soil management techniques for sugarcane production that overcome limitations in soil and nutrient resources and maximize production efficiency.
The final studies 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 harvested in October and November 2012. Rust and other disease levels were monitored through visual ratings and by taking leaf samples and determining percent rust lesions with image analysis software where applicable. The combined data from Cu and Ni studies demonstrate positive yield effects with both Cu and Ni in plant-cane and ratoon trials. This addresses objective one by developing new soil management techniques to overcome limitations in soil resources.
ARS scientists (Houma, LA) worked with a Kansas State University agriculture engineer to develop and test an optical yield monitor to predict cane yields under field harvest conditions. Results demonstrated that there was a linear relation between the optical sensor response and actual cane yields. The yield monitor was not influenced by variety or harvester speed and appeared to require minimal maintenance. This technology will allow sugarcane producers to map within field variability, identify areas requiring additional inputs, and help to maximize production efficiency, thus addressing objective one.
Multiple post-harvest residue studies were initiated to determine the best management options. Data indicates that residue management strategies will vary depending on if cane is grown for sugar or biofuels. Data from glyphosate carryover and residue management experiments indicate that the stresses of glyphosate carryover and full residue retention appear to be additive as indicated by reductions in cane and sugar yields. Ratoon seedlings were screened for their tolerance to residue and for early defoliation. Preliminary data indicates that residue decomposition is not enhanced with early defoliation and cane quality was not improved. All commercial varieties screened for residue tolerance showed a yield loss with full retention, but variety L 99-226 yielded significantly better than all other varieties with full residue retention. A new method of mechanical removal using a modified rake produced yields similarly to burning, with both yielding an additional 1120 kg/ha than full retention. Where burning was not an option, additional nitrogen did increase yields relative to traditional rates, but this response was inconsistent over the years depending on weather patterns. Addresses objective two, which is to identify methods to mitigate the current yield loss associated with post-harvest residue retention and ripener usage in sugarcane production.
Elevated soil salinity levels negatively impact sugarcane yields. In an effort to determine the potential magnitude of these effects in South Louisiana, ARS scientists at the Sugarcane Research Unit in Houma, LA, conducted two trials in commercial sugarcane fields (Dularge, LA) that were subjected to salt water intrusion during recent hurricanes. To determine actual yields, selected rows from each field were harvested in 23-meter increments using a single-row chopper harvester. Results from 2009 showed that both cane and sugar yields exhibited significant variability with yields ranging from 0.7 to 102.6 Mg/ha and 53.6 to 10,490 kg/ha, respectively. In 2010, cane and sugar yields also exhibited significant variability with yields ranging from 14.6 to 89.6 Mg/ha and 1,680 to 10,660 kg/ha, respectively. The greatest effects on cane and sugar yields appeared to occur in the lower elevation regions of the fields where flood waters remained for the longest time. The combined results from this study indicate that elevated salinity levels resulting from salt water intrusion events associated with hurricanes (or tidal movement of salty water) can have a negative effect on both cane and sugar yields.
Sugarcane post-harvest residue (PHR) is a high quality feedstock for biofuels production. When sugarcane is harvested, stalks are separated from leaves. ARS scientists at the Sugarcane Research Unit, Houma, LA, initiated a study to determine the quantity and quality of PHR as a biofuels feedstock. PHR was collected every two weeks during the three-month harvest season in 2009 and 2010 from the three main varieties of sugarcane grown in Louisiana. When averaged over the study period and across the three varieties utilized, the biomass components were relatively stable and within the current ranges based on other feedstocks being used for biofuels - such as Miscanthus.