Spatial Variability of Cotton Fiber Yield and Quality in Relation to Soil Variability

Abstract

Cotton fiber quality is important to the producer because reduced quality results in a significant monetary penalty. Therefore, to maximize profitability, the producer must also attempt to control the quality of the crop while maximizing yield. The tools of precision agriculture appear to be well suited to this task. The objective of this research was to measure the natural variability present in cotton fiber yield and quality parameters. Cotton, variety LA 887, was grown in a producer's field in Florence SC for two consecutive years. Soil (0–20 cm) and fiber samples (1 m row) were collected from a regular grid (120 * 40 m, 7.5-m interval). Soil properties determined included soil moisture, soil texture, organic matter, pH, Ca, Mg, K, P, and Na. Fiber quality was estimated by several methods, including the high volume instrumentation (HVI) method and the advanced fiber information system (AFIS). The HVI method is used by USDA-AMS to class and price cotton and the AFIS system is used primarily by cotton researchers. All fiber and soils data were analyzed by both conventional statistics (univariate and correlation) and geostatistical techniques (variogram analysis and kriging). Soils data was found to be non-normally distributed and spatially correlated. Fiber yield was normally distributed and spatially correlated and fiber quality varied in both its distribution and spatial correlation. Soil pH, soil phosphorus and soil organic matter were correlated with fiber yield and a number of fiber properties, including micronafis, immature fiber fraction (IFF), fine fiber fraction (FFF), cross-sectional area (An) and micronaire. Kriged maps of soil properties provided useful indicators of fiber yield and quality variation.