|Richard Jr, Edward|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2008
Publication Date: 11/7/2008
Citation: Viator, R.P., Johnson, R.M., Richard Jr, E.P., Waguespack, H.L., Jackson, W. 2008. Influence of nonoptimal ripener applications and postharvest residue retention on sugarcane second ratoon yields. Agronomy Journal. 100(6):1769-1773. Interpretive Summary: Sugarcane encounters stress during different parts of the growing season. Some of this stress is grower applied, such as cane ripeners, in order to increase sugar levels in the cane plant or allowing leaf litter to remain on the cane after harvesting. The purpose of this research was to determine the effect of ripener applications and retention of post-harvest leafy material on the yields of the first- and second-ratoon crops. Glyphosate, a common ripener throughout the international sugar industry, was applied to first-ratoon sugarcane and harvested at 40, 50, and 60, days after application. After harvest, the blanket of leafy material was either removed from the top of the row or left in tack. Waiting until 60 days to harvest the ripener-treated cane did not increase cane or sucrose yields in the first-ratoon crop and reduced sucrose yields by 5% in subsequent second-ratoon crop compared to where ripener was not applied. Retaining leafy material produced during the harvest of the first-ratoon crop reduced cane and sugar yields by 4% in second-ratoon crop compared to where it was removed from the row top. Growers must realize that non-optimal ripener management and failure to remove leafy material from the row-top, can reduce yields in the subsequent ratoon crops.
Technical Abstract: Retention of sugarcane (interspecific hybrids of Saccharum spp.) post-harvest residue and certain types of glyphosate ripener applications have independently been shown to reduce yields of the subsequent ratoon crop. The objective of this experiment was to determine the combined effects of post-harvest residue retention, ripener application, and ripener treatment to harvest intervals (THI) on yields of the treated first ratoon and the subsequent non-treated second ratoon. Whole plots consisted of either a non-treated control or a 0.21 kg a.e./ha application of glyphosate to first ratoon LCP 85-384 in 2003 and 2004. Split-plots consisted of THI of 40, 50, and 60 days for the first ratoon. Split-split plot treatments consisted of mechanical repositioning of post-harvest residue into the wheel furrow compared with complete retention of residue in the second ratoon. At a 40 and 60 day THI, sucrose yield was not significantly increased due to ripener application, but at a 50 day THI glyphosate application increased sucrose yield (8140 kg/ha) compared to the control (7400 kg/ha) in the first ratoon. In the second ratoon, there was a glyphosate by THI interaction on sucrose yield indicating that these stresses do compound each other. Harvesting at a 60 day THI in the first ratoon reduced cane and sugar yield of the second ratoon (54.2 Mg/ha and 6900 kg/ha) compared to the 40 (59.1 Mg/ha and 7800 kg/ha) and a 50 day THI (60.2 Mg/ha and 7800 kg/ha) for glyphosate-treated cane. Furthermore, waiting until a 60 day THI reduced sucrose yields by 300 kg/ha compared to the non-treated control in the second ratoon. The fact that there was no interactions between post-harvest residue retention and ripener application on yields of the subsequent second-ratoon crop indicates that these stresses act independently of each other. Full residue retention reduced cane and sucrose yield by 2.3 Mg/ha and 300 kg/ha compared to partial removal. Until tolerant varieties are identified, producers should remove post-harvest residue to mitigate yield losses in subsequent ratoons. In addition, delaying the harvest of ripener-treated cane due to uncontrollable climatic conditions until a 60 day THI will negate the yield advantage associated with a ripener application in the harvested crop and will decrease yields in the subsequent crop.