Growth analysis of diverse upland cottons in varied cultures

Abstract

A replicated field test was conducted in the Brazos River Valley in 1972 and 1973 to investigate the response of three varied American Upland cotton genotypes to cultural practices thought to be important to the evaluation of genotypes suitable for short-season cotton production in more humid areas of the cotton belt. A standard Delta-type variety and two experimental genotypes representing indeterminate, intermediate, and determinate growth habit were grown in all combinations of four planting geometries embodying three plant populations, two fertility levels, and two irrigation levels. Plant fraction, blooming, yield, and fiber data were collected; secondary growth parameters were derived. The most determinate genotype was precocious in plant development and fruiting, a response attributed to relatively short internodes, sustained rapid node production, and rapid elaboration of leaf area as measured by LAI response. The indeterminate Delta-variety developed and matured relatively more slowly, and had longest internodes but slowest node and leaf area production. The intermediate genotype exhibited the early season response of the determinate genotype through the first seven weeks of growth but after that its node production and leaf area production gradually declined. Yields of the determinate genotype equaled or exceeded those of the Delta-variety and earliness was related to relative precocity. Increased population size generally increased production of plant fractions on a unit land area basis but individual plant growth was reduced. Geometrical arrangement of drill-rows containing equally spaced plants was influential when populations were high (192.7 M/ha); more evenly distributed drill-rows enhanced early growth but retarded late season growth. High fertility and added irrigation generally enhanced growth; vegetative growth was favored. Secondary growth parameters including RGR, NAR, LAR, and CGR were more closely associated with vegetative growth than with lint yield and earliness. Final yields and relative percent lint at a selected harvest were not significantly influenced by plant population and spacing. High fertility and added irrigation slightly increased yield but reduced earliness. Yield responses of the two more determinate genotypes showed a more critical need for balanced fertility-irrigation inputs when grown under relatively high population and fertilizer rates. Total boll production was negatively associated with boll size and this reduction became an important factor in lint production. Ginning and fiber characteristics were not consistently influenced by variables other than genotype.