Linda Benedict, Arceneaux, Allen | 7/31/2013 8:44:09 PM
H. Magdi Selim and Allen Arceneaux
The shift of sugarcane harvesting practices over the past 20 years from burning leaves to leaving leaves on the soil surface is raising several economic and environmental concerns. In the traditional whole-stalk harvest system, whole stalks of sugarcane are cut, piled, burned, picked up and transported to the mill. The new system involves the use of a combine harvester (Figure 1) that cuts the cane stalks into small pieces called billets, which are directly loaded into wagons for transport to the mill. Fans in the combine harvester separate leaf material from billets, and the residue is blown onto to the soil surface.
This study investigated the long-term effect of several postharvest crop residue management practices on the yield of sugarcane hybrids. The treatments were burning the mulch after harvest and cultivating in the spring, sweeping the mulch off the top of the row and cultivating in the spring, and leaving the mulch on the field and cultivating in the spring. Figure 2 is a photo of burning sugarcane residue after harvest.
This study was carried out on two experimental sites at the LSU AgCenter Sugar Research Station in St. Gabriel. Six 0.6-acre leveed plots were located on a Commerce silt loam. Six 0.3-acre leveed plots were located on a Sharkey clay soil. Sugarcane was grown for two six-year growing cycles on Commerce soil. The sugarcane variety HoCP91-555 was planted in September 2001, and the sugarcane variety L97-128 was planted in August 2006. One sugarcane cycle was grown on Sharkey clay soil with the sugarcane variety HoCP91-555 planted in October 2003. The treatments were applied after each harvest, and yields were measured each year.
For sugarcane grown on Commerce soil, the average biomass for 2003-2005 growing seasons were 26.9 tons per acre for the burn treatment, 24.4 tons per acre for the no-till treatment and 25.4 tons per acre for the sweep treatment. The lower yields for the no-till and sweep treatments compared to the burn treatment were consistent for all three growing seasons.
Sugar yields for the first-year plant-cane averaged 6,871 pounds per acre. In subsequent years, average yields were 5,769 pounds per acre for the burn treatment, 5,042 pounds per acre for the no-till treatment and 5,251 pounds per acre for the sweep treatment. Sugar yield for the burn treatment was 12.6 percent higher than no-till and 9 percent higher than the sweep treatment.
Yield results for sugarcane grown on Sharkey clay soil for four growing seasons showed similar results. Corresponding biomass yields were 26.3 tons per acre for the burn treatment, 25.7 tons per acre for the no-till treatment and 25.5 tons per acre for the sweep treatment. The corresponding average sugar yields were 5,350, 5,017 and 4,818 pounds per acre. Sugar yield in the burn treatment was 9.9 percent higher than no-till and and 6.2 percent higher than the sweep treatment.
For the second planting on Commerce soil, the average biomass yields in tons per acre were 26.7 in 2008, 24.7 in 2009 and 26.7 in 2010. The corresponding average sugar yields were 6,199, 6,126 and 5,358 pounds per acre. Sugar yield with the burn treatment was 13.6 percent higher than no-till and 1.2 percent higher than the sweep treatment.
Table 1 shows biomass yield and sugar yield averages for each treatment over nine crop years. These results indicate that the burn treatment produced significantly greater biomass and sugar yields than the mulch treatment; the swept treatment was not significantly different from either of the others.
H. Magdi Selim is the A. George & Mildred G. Caldwell Professor of Soil Sciences in the School of Plant, Environmental & Soil Sciences.
(This article was published in the spring 2013 issue of Louisiana Agriculture magazine.)