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Use of Sprinklers to Study the Influence of Population Density Upon Seed Cotton Production in an Arid Area¹

The growing period for cotton (Gossypium hirsutum L.) has been shortened by 2 months in the Imperial Valley because of an invasion by pink bollworm. The law now requires that cotton residue be incorporated into the soil early to lower the number of overwintering larvae. The shorter period for floral development led to reexamination of yield potential under different plant spacing. Defoliants, fertilizer, desiccants, and insecticides for pink bollworm control and water were applied through the sprinkler system. Randomized block designs of ‘Stoneville 213’ and ‘Paymaster 111A’ included plant densities of 15,000, 60,000, 242,000, and 969,000 plants/ha on a flat soil surface. Seeds were placed by hand at 2 per dibble in a square grid pattern. The bolls per plant were significantly affected by plant density. The effect of plant density on boll weight was significant on Paymaster 111A but not on the Stoneville 213. The highest seed cotton yield occurred where the plants produced the greatest number of bolls per hectare. For both varieties the highest yield occurred in the 242,000/ha treatment, with 4,870 kg/ha in Stoneville 213, and 4,228 kg/ha in Paymaster 111A. A trend of lower micronaire in the highest density was noted in each variety.

Key Words: Pink bollworm • Cotton harvest • Grid planting

² and Farm Advisor, Agricultural Extension, Imperial County. The authors gratefully acknowledge support from Rain Bird and Johns Manville Corp. and Herman Meister, Farm Advisor — Entomology.

Received for publication May 30, 1972.