Evaluation of crop and soil spatial variability in Louisiana sugarcane production systems

Authors: Johnson, Richard; Richard Jr, Edward

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 8/20/2002
Publication Date: 9/20/2002
Citation: Johnson, R.M., Richard Jr, E.P. 2002. Evaluation of crop and soil spatial variability in Louisiana sugarcane production systems. In: Proceedings of the 6th International Conference on Precision Agriculture. ASA-CSSA-SSSA, Madison, Wisconsin. 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 and fertilizer application, may offer an important tool to accomplish this task. In this study, soil analyses, an important tool in precision agriculture, was combined with sugarcane yield and quality to map the correlations among soil chemical and fertility properties, sugarcane quality, and sugarcane yield. Distinct relationships were found between soil properties and sugarcane yield. The yield correlations were particularly significant with respect to soil magnesium, soil potassium, soil organic matter and soil cation exchange capacity (a measure of the total soil fertility). Soil potassium and phosphorus were also strongly linked to sugar quality properties. These properties were also found to vary across the field. The observed variation was not random, but was instead found to be spatially correlated. Samples that were spaced at a distance less than the range of spatial correlation were more similar than those at distances greater than this range. To further study this variation, precision agriculture maps were constructed for each soil and sugarcane property. A strong relation was found between soil potassium, soil pH, soil calcium and soil sulfur and sugarcane yield and quality. These maps can also be used to develop variable rate fertilizer and lime programs. Sugarcane growers that adopt these methods may benefit from decreased fertilizer and lime costs, while minimizing the environmental impact of their application.

Technical Abstract: This study reports results from our evaluations of the spatial variability of soil chemical properties in selected sugarcane soils of Southern Louisiana. Sugarcane variety LCP 85-384 was grown in two locations, Rebecca plantation in Schriever LA and Gralyn plantation in Patoutville LA. Each field was harvested in a grid cell pattern with cell dimensions of 10.6 x 15.2 m. Individual cells were harvested with a single row, chopper sugarcane harvester with weights determined using a weigh wagon. In addition to weights, a grab sample of the harvested cane was obtained from each grid cell for sugar quality analysis. Soil samples (0-15 cm) were collected after harvest from each grid cell. Soil properties determined included: OM, pH, Ca, Mg, K, P, CEC and S. Yield, quality and soils data were analyzed by both conventional statistics and geostatistical techniques. At Rebecca, sugarcane tonnage varied from 35.8 to 134 Mg ha-1, TRS from 51 to 104 kg Mg-1 and Sugar from 2,644 to 14,568 kg ha-1. At Gralyn, tonnage ranged from 31 to 114 Mg ha-1, TRS from 41 to 115 kg Mg-1 and sugar from 3,007 to 12,433 kg ha-1. All soil properties, at both locations, were found to be spatially correlated. At Rebecca plantation all sugar yield and quality parameters were also spatially correlated. At Gralyn plantation only tonnage and sugar yield were spatially correlated. Kriged maps of sugarcane yield, quality and soil properties may prove useful in delineation of management zones for variable rate lime and fertilizer application.