Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 22, 2005
Publication Date: January 9, 2006
Citation: Pettigrew, W.T., Johnson, J.T. 2006. Effects of Different Seeding Rates and Plant Growth Regulators on Early Planted Cotton. Journal of Cotton Science. 9:189-198. Interpretive Summary: An early planting cotton production system offer improved yield potential over that of the more traditional production systems. However, the various production nuances that go into the system still need to be fined tuned to consistently obtain the most yield benefits. Despite accelerating the maturity of the crop and reducing plant stature, the application of PGR’s did not improve yield. This situation is probably due to the longer growing season afforded by the early planting which allowed for late flower production from the untreated plants to set bolls that matured in time for harvest. Only the lowest seeding rate utilized in this study (7 plants per square yard) produced a measurable effect on yield; it reduced yield by approximately 5%. All the other seeding rates produced similar yields. Due to harsh conditions surrounding the seeds when planting early, a slightly higher seeding rate is needed with the early planted production system to achieve minimal optimal plant densities because of lower seedling survival levels and uneven plant distribution within a row. The results from this research demonstrate that, when cotton is planted early, producers may not need to apply plant growth regulators (a commonly utilized production input) to maximize yields and profits.
Technical Abstract: Although the early planted cotton production system offers improved lint yield potential, production techniques still need to be optimized to ensure consistent yield enhancement. The objectives of this study were to determine how varying seeding rates and application rates of mepiquat-type plant growth regulator compounds (PGR) affected cotton growth and production under early planted conditions. A field study was conducted under early planting conditions from 2001 through 2004 using four cotton varieties (PM 1218BR, Stv. 4691B, Stv. 4892BR, and DPL 555BR) and four seeding rates (7, 9, 11, and 13 plants per square meter). Depending upon the year, half the plots were treated with either mepiquat chloride or mepiquat pentaborate (plus PGR), while the remaining plots were untreated (no PGR). Dry matter partitioning, canopy light interception, bloom counts, lint yield, yield components, and fiber quality data were collected throughout the course of the experiment. Leaf area index (LAI) increased progressively as the seeding rate increase when PGR was not applied, but the LAI plateaued at 11 plants per square meter when PGR was applied. When PGR was applied to the crop, plant height was reduced 9% while the specific leaf weight was increased 4%. PGR treated plants produced more flowers early in the season while the untreated control plants produced more later in the season. This earlier maturity of the PGR treated plants was also reflected in the reduced nodes above white bloom (NAWB) data relative to the control plants. No yield response was observed from the PGR application, but the lowest seeding rate (7 plants per square meter) had a 5% lower yield than any of the other seeding rates. Few fiber quality differences were detected among PGR application rates or seeding rates. The longer growing season afforded with a early planting system allows for the late season flowers on the control plants to develop into mature open bolls and thereby result in equal yields between the control and PGR treated plants.