|Richard Jr, Edward|
Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/18/2004
Publication Date: 11/20/2005
Citation: Johnson, R.M., Richard Jr, E.P. 2005. A comparison of conventional and variable rate lime application methods in South Louisiana sugarcane fields. In: Proceedings of the International Conference on Precision Agriculture. 7th International Conference on Precision Agriculture, July 25-28, 2004, Minneapolis, Minnesota. 2005 CDROM.
Interpretive Summary: Louisiana sugarcane producers, like most U.S. agricultural producers, have faced increased economic pressure in recent years. Growers must find ways to decrease costs and maximize profits. Precision Agriculture, specifically, variable rate lime application, may offer an important tool to accomplish this task. An experiment was conducted in two locations, Schriever and Plaquemine Louisiana, to determine if variable rate lime application could benefit the sugarcane industry. In the variable rate method, soil samples are taken in a grid pattern in the field and are used to predict how much lime is needed in different areas of the field. In the traditional method, only one rate of lime (based on an average of several soil samples) is applied to all parts of the field. In both years at the Schriever study there was a significant yield benefit to applying lime by either the variable rate or traditional method compared to no lime additions. The traditional method resulted in yields that were slightly higher the variable rate method; however, in the second year the difference between the two methods was much lower. In the Plaquemine study a difference in sugarcane yield was not seen, although the variable rate method did increase the sugar content of the cane. These combined results are promising, because if similar yields can be obtained with the variable rate system, which is actually applying less inputs, then an overall increase in profitability will be observed. The results also indicate that further research on the VR application method is required to achieve maximum yields. Sugarcane growers that adopt these methods may benefit from decreased fertilizer and lime costs, while minimizing the environmental impact of their application.
Technical Abstract: Louisiana sugarcane producers continue to face increased economic pressure. Growers must find ways to decrease costs and maximize profits, while minimizing potential negative environmental impacts. Precision agriculture, specifically, variable rate lime and fertilizer application, may offer an important tool to accomplish this objective. Two studies were conducted in plant-cane crops on commercial sugarcane farms in South Louisiana. The first study was initiated in 2002 in a 20-ha field at Schriever, LA and the second study in 2003 in a 12-ha field at Plaquemine, LA. In each study, a conventional (uniform rate) lime application method was compared to a variable-rate (VR) application method and a no lime control. Prior to lime application, soil samples (0-20 cm) were taken from each site on a 0.4-ha grid. A random soil sample was also collected from each field to determine the lime rate, based on current extension recommendations for the conventional treatment. Soil properties determined included pH and lime requirement. Treatments were applied in strips that were 14 rows (~ 25 m) wide and ranged from 300 to 450 m in length. Lime for both conventional and variable rate treatments was applied with an Ag-Chem Terra-Gator at recommended rates. Each plot was harvested in 30-m sections to enable mapping of results. Plots were harvested with a single-row, chopper harvester with weights determined using a weigh wagon. In addition to weights, a random grab sample of cane billets was obtained from each section for sugar quality analysis. Yield, quality, and soils data were subjected to analysis of variance to determine treatment differences. Results from the Schriever study in 2002 for the plant-cane crop showed an advantage to both the conventional and VR treatments in terms of sugar yield as compared to the no-lime check with yields of 7,650 and 6,550 kg ha-1 compared to 6,110 kg ha-1. In 2003 sugar yields in the first ratoon crop were 9,000, 8,560 and 8,080 kg ha-1 for the conventional, VR, and no-lime treatments, respectively in the Schriever study. In the Plaquemine study there were no statistical differences with plant-cane yields of 10,740, 10,700, and 10,370 kg ha-1 for the no-lime, conventional, and VR treatments, respectively. Although the VR treatment decreased total lime applied by targeting application to only areas where lime was required, yields were not equal to the uniform application. Additional research is needed to refine the VR lime application method.