Tillage effects on canopy position specific cotton fiber properties on two soils

The benefits of conservation tillage on soil water availability are well established, but this soil management practice generally does not affect cotton (Gossypium hirsutum L.) fiber properties of the whole crop. The objective was to determine whether soil management practices affect canopy position specific fiber properties on two soils. A 3-yr field study was conducted with plots on two soil types [Bonneau loamy sand (loamy, siliceous, thermic Arenic Paleudult) and Norfolk loamy sand (fine-loamy, siliceous, thermic Typic Kandiudult)]. Treatments in the study were cover crop [none and rye (Secale cereale L.)] and tillage system (disk tillage and conservation tillage). Fiber properties were determined from hand picked samples at three canopy positions (first sympodial position bolls at Mainstem Nodes 6 and 7, 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, conservation tillage had 34% higher yield than disk tillage. Conservation tillage had higher fiber length uniformity every year, but no consistent differences between tillage systems occurred for the other fiber properties. Cover crop did not influence within-canopy fiber properties. When differences occurred between tillage systems for fiber length at specific canopy positions, fibers from conservation tillage were about 1 rum longer than fibers from disk tillage. Fiber length uniformity results were similar to those for fiber length. Disk tillage resulted in cotton with 0.22 lower micronaire units than conservation tillage at Mainstem Nodes 6 and 7 when rainfall was plentiful in 1997, but had micronaire that was 0.82 units higher than conservation tillage at that canopy position during the dryer year of 1998. Within canopy variability for micronaire was greater on the more drought susceptible Bonneau soil than on the Norfolk soil. Results indicate that tillage management can influence canopy position specific fiber property distribution.