Wilson E. Judice, James L. Griffin, Michael E. Salassi and Charles W. “Chuck” Kennedy
In Louisiana sugarcane, row shoulders and middles are intensively cultivated to promote crop growth, eliminate ruts, incorporate fertilizer and control weeds. In a typical production system, fields are tilled in mid to late March, in mid April when fertilizer is applied, and in mid to late May. For each tillage operation, an area on the row top about 24 inches wide is not disturbed.
Although some form of reduced tillage is used in most agronomic crops, sugarcane growers have been slow to adopt reduced tillage practices because of concerns over reduced yields and weed control. The objectives of this research were to evaluate the effects of no-tillage and reduced tillage programs on sugarcane growth, yield and weed management and to compare the economics of reduced tillage programs with a full tillage conventional program.
In the first tillage study, experiments were conducted at the LSU AgCenter’s Sugar Research Station in St. Gabriel. The treatment factors included 1) spring tillage in late March or notillage, 2) DuPont K4 (a herbicide premix of hexazinone plus diuron) applied to a 36-inch band on the row top or broadcast immediately after the spring tillage operation, and 3) layby tillage in mid to late May or no-tillage. With these treatment combinations, one treatment would represent no-tillage for the entire growing season. Temperature probes were placed in the center of the sugarcane drill at a 2-inch depth in both the tilled and nontilled plots, and soil temperature was recorded from March through May both years of the study (2002-2003).
In the second tillage study, experiments were conducted in 2004 at five locations in Assumption, St. James, St. Mary, St. Martin and Iberia parishes. The treatment factors included 1) spring tillage in early March or no-tillage and 2) layby tillage in mid to late May or no-tillage.
For both the spring and layby tillage operations row shoulders and middles were mechanically worked using disk gangs, leaving an area approximately 24 inches wide on the row top undisturbed. For the layby tillage, soil was deposited on the row tops but sugarcane shoots were not completely covered. Crop residue from the previous year’s harvest had decomposed during the winter so it did not affect spring growth of sugarcane.
In the first tillage study, sugarcane initiated growth around March 1 each year. Average daily soil temperature measured at a 2-inch depth within the 24-inch wide noncultivated sugar cane drill was similar both years, whether or not sugarcane row middles and shoulders were tilled. This suggests that contrary to perceptions of sugarcane producers, March tillage did not promote increased warming of sugarcane beds when compared with no-tillage. Weed control was excellent when DuPont K4 was used and weeds were not a limiting factor in this study.
Since differences in sugar yield for the various tillage treatments in the first study were not observed, sugar yield data could not be used to calculate gross return. Tillage cost was figured at $7.84 ($4.16 variable and $3.68 fixed). Differences in net return were a function of the difference in tillage costs and in herbicide costs. Compared with a conventional tillage program (spring and layby tillage), elimination of a single tillage operation reduced cost $7.84 per acre. When both tillage operations were eliminated cost was reduced $15.68 per acre. If herbicide was broadcast instead of banded, herbicide cost would double, and net return would be reduced proportionally.
In this study weeds were effectively controlled whether herbicide was banded or broadcast. In the second tillage study, differences in net return for the tillage programs were a function of differences in sugar yield and in tillage costs. When March tillage was eliminated, sugar yield was increased 554 pounds per acre (7,009 pounds per acre versus 6,455 pounds per acre). When May tillage was eliminated, sugar yield was increased 518 pounds per acre (6,991 pounds per acre versus 6,473 pounds per acre).
The increase in gross returns per acre estimated at 50 percent grower share of yield times $0.20 per pound of sugar was $55.40 per acre when March tillage was eliminated and $51.80 when layby tillage was eliminated. Eliminating a single tillage operation also resulted in a cost savings of $7.84 per acre ($4.16 variable and $3.68 fixed). Using the increase in gross return plus the savings in tillage cost, elimination of March tillage increased net return $63.24 per acre and elimination of layby tillage increased net return $59.64 per acre. Any increase in net return associated with using reduced tillage can be expected only if weeds can be managed and not contribute to reduced yields.
In this research conducted at six locations and on soils ranging from very fine sandy loam to silty clay loam, elimination of March tillage did not negatively affect warming of beds, emergence and growth of sugarcane, or fertilizer application when injected on either side of the sugarcane drill using knives or coulters. Additionally, eliminating March tillage did not reduce sugar yield. In one study sugar yield was increased when March tillage was omitted. As growers search for ways to reduce input costs, the elimination of a single tillage operation would reduce cost $7.84 per acre. This cost would increase as the price of diesel fuel increases.
A no-tillage or reduced tillage program would be a viable option for sugarcane growers in plant cane or in stubble cane not rutted during the previous harvest. At this point it would not be recommended that a total no-tillage program be used in consecutive years because of concerns of soil packing and loss of row integrity. An alternative to a conventional full tillage program might be one where spring tillage is eliminated, fertilizer is knifed in, and tillage is performed at layby to rebuild rows.
Cost savings in fuel, equipment and labor along with a possible reduction in soil loss and an increase in soil moisture conservation would make reduced tillage programs a viable economical option. In this research weed control was excellent throughout the growing season regardless of tillage or herbicide program. Caution should be used in implementing reduced tillage programs where perennial weeds such as Bermuda grass, Johnson grass and nutsedge are problematic.
Wilson E. Judice, Former Graduate Research Assistant, and James L. Griffin, Lee Mason LSU Alumni Association Professor, School of Plant, Environmental & Soil Sciences, and Michael E. Salassi, J. Nelson Fairbanks Endowed Professor, Department of Agricultural Economics & Agribusiness, LSU AgCenter, Baton Rouge, La.
(This article was published in the spring 2008 issue of Louisiana Agriculture.)