SUGARCANE RESPONSE TO DEPTH OF SOIL COVER AT PLANTING AND HERBICIDE TREATMENT

Authors: Richard Jr, Edward; Dalley, Caleb

Submitted to: American Society of Sugar Cane Technologists
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2006
Publication Date: 5/9/2006
Citation: Richard Jr, E.P., Dalley, C.D. 2006. Sugarcane response to depth of soil cover at planting and herbicide treatment. Journal of the American Society of Sugar Cane Technologists. 26:14-25. Available: http://www.assct.org/journal/journal.htm

Interpretive Summary: In Louisiana, it is currently recommended that the depth of soil used to cover sugarcane during planting should be 8 to 10 cm. This depth of soil is recommended as it provides protection of sugarcane roots and underground bud shoots from: freezing winter temperatures, herbicide injury, and the uprooting of stubble pieces during mechanical harvesting. Due to slow emergence of the most widely grown sugarcane cultivar in Louisiana, LCP 85-384, many growers have adopted shallower planting practices to reduce time of emergence in the hopes of improving sugarcane establishment. Research was conducted over a three-year crop cycle to compare the use of shallow (5 cm) to conventional (10 cm) covering depths at planting using commonly used herbicides with varying potential to injure sugarcane [metribuzin (1.7 kg/ha), pendimethalin + atrazine (3.4+3.4 kg/ha), pendimethalin + diuron (3.4+2.9 kg/ha), terbacil (1.5 kg/ha), terbacil + pendimethalin (0.9+2.2 kg/ha), terbacil + diuron (0.9+2.9 kg/ha), azafenidin (0.7 kg/ha), and clomazone + atrazine (1.7+3.4 kg/ha)]. Yield was reduced during the first production year comparing 5 with 10 cm of soil cover when the herbicides terbacil, azafenidin, and terbacil + diuron were applied. In the second production year application of terbacil, pendimethalin + diuron, and terbacil + diuron reduced sugarcane yield comparing 5 cm with 10 cm of soil cover at planting. During the third production year, yields were similar when comparing depth of soil cover at planting for all herbicide treatments. While the objective of reducing depth of soil cover was to enhance early crop establishment and yield, we found that there was no advantage to shallow planted sugarcane over traditional coverage practices when based on end-of-year yield parameters. Additionally, using shallow cover often left sugarcane more vulnerable to herbicide injury from certain herbicides that resulted in reduced yields during the first and second production years.

Technical Abstract: Research was conducted to evaluate the effects of depth of cover at planting on sugarcane yield and response to preemergence herbicide treatments over a complete three-year sugarcane cycle. Two studies were conducted at the Welcome Plantation in St. James Parish, LA, using LCP 85-384 sugarcane planted on August 26, 1997 (StudyA) and Oct 4, 1998 (StudyB). Both studies were conducted on a Commerce silt loam, a soil with moderately low permeability. In a split-plot arrangement, sugarcane was covered with either 5 or 10 cm of soil at planting (whole plot), and eight different herbicide treatments (sub-plot) were applied soon after planting and in March or early April in the plant-cane, first-, and second-ratoon crops. The herbicide treatments included in this study were: metribuzin (1.7 kg/ha), pendimethalin + atrazine (3.4+3.4 kg/ha), pendimethalin + diuron (3.4+2.9 kg/ha), terbacil (1.5 kg/ha), terbacil + pendimethalin (0.9+2.2 kg/ha), terbacil + diuron (0.9+2.9 kg/ha), azafenidin (0.7 kg/ha), and clomazone + atrazine (1.7+3.4 kg/ha). These herbicides were selected because of their common usage, and their varying degrees in potential to injure sugarcane. In plant-cane, covering with just 5 cm compared to 10 cm of soil resulted in a loss of 5 t/ha gross cane yield, 3 kg/t TRS, and 1,100 kg/ha theoretical sugar yield, when averaged across herbicide treatments. When separated into herbicide treatments within each depth of cover treatment, only the herbicides: terbacil, azafenidin, and the combination of terbacil + diuron reduced gross cane yield comparing 5 with 10 cm of soil cover at planting. Theoretical sugar yield was also reduced by terbacil and terbacil + diuron applications when comparing 5 with 10 cm of soil cover. In the first-ratoon crop, terbacil reduced gross cane yield by 12 t/ha, and theoretical sugar yield by 1,900 kg/ha, and a 1,500 kg and a 1,000 kg/ha reduction in sugar occurred when pendimethalin + diuron, and terbacil + diuron were applied, respectively, comparing 5 with 10 cm of soil cover at planting. No differences in sugarcane yield were found in the second-ratoon crop due to depth of soil cover at planting. While the objective of using shallow cover at planting would be to reduce emergence time to improve establishment and plant-cane production we found that in no case were shallow planting practices superior to traditional practices and in many cases, shallow planting left the crop more vulnerable to herbicide injury resulting in poorer yields during the plant-cane and first-ratoon crops.