Date of Award

5-2023

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant and Environmental Science

Committee Chair/Advisor

Michael Plumblee

Committee Member

Michael Jones

Committee Member

Michael Marshall

Committee Member

Sruthi Narayanan

Abstract

Seed size, seeding rates, pre-emergence (PRE) herbicides, planting dates, and maturity groups are all important factors that growers must consider before planting cotton or soybean. Previous research has suggested that seed size and seedling vigor are positively correlated and having greater seeding vigor may compensate for adverse planting conditions, pest and disease pressure, and potentially injury from PRE herbicides. Seeding rates and planting dates for cotton are dependent on the variety, environmental conditions, and grower goals. Planting date and maturity group selection are also important considerations for soybean growers in SC as in many cases soybean is planted in rotation with other higher value crops or double cropped behind cereal grains, often leading to delayed planting. Two trials were conducted in Florence and Blackville, SC to determine the influence of seed size, seedling vigor, seeding rate, and planting date on cotton growth, yield, and injury from pre-emergence herbicides, and one trial was conducted to determine the optimum planting date x maturity group combination for soybean produced in SC. Data on biomass, stand count, plant height, yield, and fiber quality were collected from both cotton trials each year, and height, node, stand counts, and yield data were collected from the soybean trial each year. In both cotton trials, the larger seed had greater seedling vigor than the small. However, this increase in seedling vigor did not result in higher lint yields than the small-seeded variety. Late planting resulted in higher yields in two years of the study and increased seeding rates resulted in higher yield in one year and in one location only. Increased seedling vigor may be beneficial when weather conditions at planting are poor or when PRE herbicide injury is expected. Results from the soybean trial indicate that soybeans can be planted as early as late-March and as late as late-June to achieve optimal yields in SC.

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