Impact of Sugarcane Mulch on Soil Erosion

PROJECT LEADER: Richard L. Bengtson, Professor
Biological and Agricultural Engineering Department

PROJECT OBJECTIVE: The objective of this study was to evaluate the effectiveness of sugarcane management practices on the quality of the surface runoff flow from sugarcane fields in southern Louisiana.

The project is being conducted at the LSU AgCenter’s St. Gabriel Research Station. Because of the growing acceptance of the sugarcane combine harvester, the primary purpose of this project is to evaluate the effect of post-harvest residue (mulch cover) on crop yields and in improving surface-water quality from sugarcane fields. This project is evaluating three management practices with primary focus on mulch residue management and its effect on soil losses and surface-water quality. The study consists of three treatments and two replications. Two sites with different soil types are being used for the study. One site has a Commerce silt loam soil, which is a medium-textured soil, and the other site has a Sharkey clay, which is a heavy, clay soil. Surface runoff from 0.6-ha plots is being measured using sumps and water meters. The two sites each contain six plots that are surrounded by levees. The surface runoff from each plot flows into a sump were it is measured and sampled and then pumped into a drainage ditch. An automatic water sampler collects a 500 ml sample at 20-minute intervals during runoff events. These samples are analyzed for sediment, nitrogen, phosphorus, potassium, agricultural chemicals and biological oxygen demand (BOD). The treatments concern the mulch left on the field after harvest. The treatments include (1) burning the mulch after harvest, off-barring and cultivating in the spring; (2) sweeping the mulch off the top of the row after harvest, off-barring and cultivating in the spring; and (3) leaving the mulch on the field after harvest, off-barring and cultivating in the spring. Treatment one is the common method by which the sugarcane mulch is managed in Louisiana. Treatments 2 and 3 are proposed sugarcane residue management practices for use by Louisiana sugarcane farmers. Treatment 3 -- where the mulch residue is not removed -- may be best regarded as a no-till treatment, which is a commonly used soil conservation measure. Sugarcane population, yields and quality of runoff water are being measured for each treatment.

Results to Date:

The sugarcane was planted in September 19, 2001, and was harvested December 9, 2002, October 30, 2003, October 19, 2004, and October 25, 2005. For the 4 years, the burned treatment averaged 64,947 kg/ha biomass and 7,010 ka/hg sugar. The swept treatment averaged 61,753 kg/ha biomass and 6,495 kg/ha sugar. The mulch treatment averaged 60,240 kg/ha biomass and 6,386 kg/ha sugar. The burned treatment increased biomass yields by 7.8% and sugar yields by 9.8%. There was a reduction in biomass and sugar yields for the swept and mulch treatments. For the 4 years, the soil loss for the burned, swept and mulch treatments were 7,377, 7,448, and 7,119 kg/ha, respectively. The mulch treatment reduced soil loss by 4.4%. For the 4 years, the nitrogen loss for the burned, swept and mulch treatments were 14.6, 17.0 and 16.0 kg/ha, respectively. There was not a significant difference between treatments. For the 4 years, the phosphorus loss for the burned, swept and mulch treatments were 8.3, 9.4 and 8.9 kg/ha, respectively. There was not a significant difference between treatments.

Table 1: Annual Sugarcane (Biomass) Yields (kg/ha)

Table 2: Annual Sugar Yields (kg/ha)

Expected Results:

Successful completion of this project will significantly aid in the development of advisory products such as an accurate model of crop production impacts on watershed TMDLs, thus enhancing the decision-making process for environmental regulatory agencies. By providing baseline measurement of sugarcane production impacts on the TMDL of impaired watersheds, this proposed cooperative research will significantly contribute to our overall unit goal to develop and optimize integrated crop management systems that reduce off-site transport of agrochemicals while sustaining on-farm profits.