Previous research with bioregulants indicated that potential exists to greatly influence cotton yields by establishing a season-long growth regulation strategy. Field trials conducted in Arkansas from 1985 through 1988 with the bioregulants PGR-IV, ACM-111, PPG-1721, M667ASX (Cytokin), and DCPTA indicated that bioregulant effectiveness may be significantly enhanced if these materials are formulated together or with foliar fertilizers, or applied sequentially with some materials being applied at early growth stages followed by others applied at later growth stages.

Formulation strategies for 1989 are being based upon laboratory and field evaluation data generated over the last 4 years. From 1985 through 1987, PGR-IV has proven to be an effective yield enhancer (12 to 18% increase) when properly applied at a rate of 4 oz/A, early square (ES), followed by 4 oz/A, early bloom (EB). However, effectiveness appeared to be decreased by moisture and nutrient stresses. Also, PGR-IV increased boll numbers which may lead to diminished upper boll size. ACM-111, a material containing 3 aromatic nitro compounds, is a membrane effector. The material stimulated ion uptake under laboratory conditions and significantly increased yields when applied to cotton grown under high nutrient levels. Yield was decreased when the material was applied to cotton grown under low nutrient levels. PPG1721, a benzoic acid derivative, is also a membrane effector. The material has been shown to decrease ethylene biosynthesis and membrane integrity. Under field conditions it has been erratic, generally increasing yield by 17% to no effect on yield. Moisture stress appeared to be the main confounding variable. M667ASX, a cytokinin containing material, was field tested in 1987 and 1988. The material increased yield by 7 to 16% when applied at EB and again at full bloom (FB). The material appeared to increase boll retention and favorably influenced the nutrient status of the plant. DCPTA is a auxin type material. Under laboratory conditions, the material significantly, but only moderately, stimulated ethylene production. This response is typical of auxin type materials and DCPTA could be classified as a weak, probably slowly biodegradable auxin. Other researchers have reported that DCPTA increased the enzymes for photosynthesis, increased root growth, and that yield can be significantly enhanced with DCPTA when applied at 2nd true leaf and again at 4th true leaf. In our field test, DCPTA increased yield when applied alone and when applied with PGR-IV and ACM-111. In a foliar fertilizer study, Crop Booster (12-8-4 plus micronutrients) and Crop Booster + (12-8-4 plus micronutrients and 1 oz PGR-IV/qt) significantly enhanced yield with crop Booster + performing well under non-irrigated conditions.

Based upon this previous research, a formulation strategy can be generated for cotton yield enhancement. Apply DCPTA (14 to 28 g ai/A) at the 2nd and 4th true leaf, followed by PGR-IV (4 oz/A) applied at ES and EB, followed by M667ASX (1 pt/A) and PPG-1721 (56 g/A) applied at EB and FB, followed by Crop Booster (1 qt/A) applied at EB,FB, and upper boll development (UBD), followed by ACM-111 (i pt/A) applied at UBD. This strategy would apply to irrigated cotton. Rates would probably be decreased for rain-fed cotton. Also, Crop Booster + should replace the second PGR-IV treatment and the Crop Booster treatment in rain-fed cotton. The hypothesis for this strategy is that DCPTA will increase early season growth, PGR-IV will promote fruiting and growth, M667ASX and ACM-111 will enhance nutrient uptake, PPG-1721 will influence photosynthesis, and Crop Booster and Crop Booster+ will help in providing nutrients.

In 1989, we will be field testing this strategy. Among our concerns are that the materials must be compatible with each other and insecticides, and the modes of action of each bioregulant must not be antagonistic. The total cost of this system is not known. However, we envision a yield increase of 25% plus and a quality increase if the system is utilied under proper management.