ABSTRACT
Conditions during stand establishment and early development can have lasting impact on growth and, ultimately, yield. However, there are some areas where less ideal conditions may not be critical. Cotton is known for its ability to compensate for low plant densities. Acala SJ-2 and the shorter more determinate Acala SJC-1 both responded to variable density and within row skips equally. Both were able to fully compensate for multiple skips of up to three feet as long as the plant density averaged one plant per foot under these conditions of good growth. We also verified that leaf area of California Acala cotton does not limit growth during the early stages of development. Cotton seedlings had similar final plant height, number of nodes, leaf area index, leaf weight, total dry weight, and yield as long as leaf loss did not exceed 50 percent prior to first square. Loss of 57 percent of the leaf area before first square did delay maturity 2.4 days at the time of first harvest. The major impact on subsequent growth is due to cool temperatures during planting. This can be due from the combined influences of soil pathogens, poor seed quality, or chilling injury. A relationship was developed between heat units 5 days after planting (HU), the combined warm and cool germination percentages (W+C) and field emergence. Results from three years of testing a total of 74 seed lots indicated less than 10 HU would result in poor performance, 10 to 15 HU was marginal and would only be successful with seed with W+C of 160, and that optimum early growth occurred when 20 HU was received in the 5 days following planting. The interaction between HU and W+C was significant with HU having only a minor impact on seedling performance when W+C was high, but a major impact when W+C was low. This information can be directly applied by growers as the NBAA weather service broadcasts the 5 day HU prediction during the planting season, and the W+C can be obtained from seedsmen in the San Joaquin Valley.
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