Tillage Effects on Canopy Position Specific Cotton Fiber Properties on Two Soils

by the genetic potential of the cultivar and the environmental conditions existing during the development of The benefits of conservation tillage on soil water availability are the boll that allow expression of that genetic potential well established, but this soil management practice generally does not affect cotton (Gossypium hirsutum L.) fiber properties of the whole (Ramey, 1986). Cotton bolls are initiated over a long crop. The objective was to determine whether soil management prac- period of time during the season, and fiber properties tices affect canopy position specific fiber properties on two soils. A ofbollsonthesameplantscandifferbecauseofdifferent 3-yr field study was conducted with plots on two soil types [Bonneau environmental conditions during boll growth and develloamy sand (loamy, siliceous, thermic Arenic Paleudult) and Norfolk opment. Bennett et al. (1967) found substantial differloamy sand (fine-loamy, siliceous, thermic Typic Kandiudult)]. Treat- encesinfiberqualityamongbollsduetotheweekduring ments in the study were cover crop [none and rye (Secale cereale the season that flowering occurred. Also, Meredith and L.)] and tillage system (disk tillage and conservation tillage). Fiber Bridge (1973) hand-harvested all open bolls weekly and propertiesweredeterminedfromhandpickedsamplesatthreecanopy found fiber properties differed among the weekly harpositions (first sympodial position bolls at Mainstem Nodes 6 and 7, vested samples. 9, and 10, and 12 and 13). Yield and fiber properties of the whole crop were determined after machine harvesting. In two of the 3 yr, Fiber quality can also vary across fields. Johnson et conservation tillage had 34% higher yield than disk tillage. Conserva- al. (2002) reported considerable variation for fiber mition tillage had higher fiber length uniformity every year, but no cronaire and fiber length in a 0.5-ha portion of a field consistent differences between tillage systems occurred for the other in South Carolina. They found significant correlations fiber properties. Cover crop did not influence within-canopy fiber between several fiber properties and soil pH, soil P, and properties. When differences occurred between tillage systems for soil organic matter. Emphasis has been placed lately on fiber length at specific canopy positions, fibers from conservation reducing the amount of fiber property variability within tillage were about 1 mm longer than fibers from disk tillage. Fiber a cotton crop (May, 2002), as processing techniques length uniformity results were similar to those for fiber length. Disk require a more uniform fiber to increase throughput and tillage resulted in cotton with 0.22 lower micronaire units than conseryarnproduction.Agreaterunderstandingoftheamount vation tillage at Mainstem Nodes 6 and 7 when rainfall was plentiful in 1997, but had micronaire that was 0.82 units higher than conservation and causes of fiber quality variation may lead to better tillage at that canopy position during the dryer year of 1998. Within management practices for improved fiber quality. canopy variability for micronaire was greater on the more drought We hypothesized that soil management practices insusceptible Bonneau soil than on the Norfolk soil. Results indicate fluence fiber properties of bolls when measured at spethat tillage management can influence canopy position specific fiber cific fruiting positions. We tested this hypothesis on two property distribution. soil types that differ in soil water holding capacity and historical yield potential. Our objective was to determine whether soil management practices affect canopy