Corn, cotton, and peanut response to row spacing, seeding rate, and irrigation system

Authors: Sorensen, Ronald - Ron; Lamb, Marshall; Butts, Christopher - Chris

Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2022
Publication Date: 7/4/2022
Citation: Sorensen, R.B., Lamb, M.C., Butts, C.L. 2022. Corn, cotton, and peanut response to row spacing, seeding rate, and irrigation system. Journal of Crop Improvement. (37)3:323-340. https://doi.org/10.1080/15427528.2022.2093809.
DOI: https://doi.org/10.1080/15427528.2022.2093809

Interpretive Summary: The use of subsurface drip irrigation (SSDI), laterals buried about 12 inches deep, may have serious limitations to seed germination in drought conditions and with small shallow planted seeds, i.e., cotton. If SSDI tubing is placed at 12 inches soil depth with a 72-inch lateral spacing (alternate row middles with crop rows spaced 36 inches apart), water would need to move up and laterally over 20 inches (hypotenuse) for corn and peanut planted 2 inches deep and over 21 inches for cotton planted 0.5-inch deep. Water movement this distance can be quite challenging for seed germination especially when the soil has been tilled or in a sandy soil texture. Shallow subsurface drip irrigation (S3DI), drip tubing buried just beneath the soil surface, has proven to be inexpensive and effective way to irrigate corn, cotton, and peanut in the. With drip tubing buried 2 inches deep, water movement to the seed would reduce the distance to just 18 inches compared with the SSDI system described above. Changing the crop row width from 36 to 30 inches would bring the crop row 3 inches closer to the drip tubing when using S3DI. However, this reducing the crop row spacing would increase seed expense and the number of drip laterals increasing the expense of the drip irrigation system. Another possible scenario would be to have narrow crop row widths but leave drip tube lateral spacing the same. For instance, reduce an existing 36-inch crop row to 30 inches spacing but leave drip tube lateral spacing at 72 inches. Tractor wheel spacing along with other wheeled equipment would not have to be changed. Harvesting equipment of combines/pickers/inverters for corn, cotton, and peanut, respectively, would not have to be adjusted. The final dimensions could be a 30-inch crop row with 42-inch middles. The water flow path to the crop rows would then be reduced to 15 inches instead of 18 inches for the normal 36-inch row with S3DI compared with 20 to 21 inches for a SSDI system. The objective of this research was to document the yield response of corn, cotton, and peanut planted at two different row spacings, two different seeding rates, on three different soil types, and two types of irrigation systems. This research was conducted at four different locations in southwest GA, USA. Tractors used in this research were GPS capable such that two row equipment (strip till) and larger (field cultivator, planters, sprayers) would match row patterns. All plots were planted with a vacuum type seeder at specified seeding rates and row spacings. In addition, all crops were planted at the recommended timing across all years and locations. Two identical vacuum planters were used, one set for the 30-inch row width and another for 36-inch row width. Strip tilled areas were typically prepared one to two weeks in advance of planting. The recommended seeding rates used for corn, cotton and peanut were 2.2, 3, and 6 seeds/ft (32,000, 43,500, and 87,000 seeds/ac), respectively, and the half-recommended rates had the planters adjusted to reduced seeding rate appropriately. Fertilizers and soil amendments (lime) were applied at recommended rates as determined by soil test for each farm and each plot. Nitrogen was applied in either two or three split application events depending on weather conditions and manpower or equipment availability to the four farms. All pesticides and fungicides were applied at recommended timing and rates determined by field scouting and manufacturer guidelines for each individual crop. Irrigation events were scheduled using either soil water potential sensors or IrrigatorPro computer program depending on location. Harvest occurred when individual crops were physiologically mature. Crop yield was determined using accepted practices for each individual crops. Crop quality was determined by USDA classifications services. Individual sites, years, crop

Technical Abstract: Planting seed closer to a drip line water source should result in increased seed development, greater crop yield, possible water savings, and may reduce seeding rate without affecting yield, resulting in lower seed costs. This research documents the yield response of corn, cotton, and peanut planted in two crop row spacings (0.76 and 0.91 m), at two seeding rates (1X and 0.5X), at four locations, and two irrigation systems (sprinkler and drip). Crops were managed using best management practices for maximum yield. Irrigation events were scheduled to minimize soil water stress. There was no yield response across all crops, locations, or irrigation systems for 0.76 versus 0.91-m crop row spacing. The 0.5X seeding rate in drip irrigation and across all sites reduced corn yield and revenue by an average 1572 kg/ha and $-94/ha, respectively. The 0.5X seeding rate in drip irrigation did not decrease yield in cotton or peanut and revenue above seed cost averaged $16 and $95/ha, respectively. It should be noted that in cotton and peanut, the 0.5X seeding rate may impose a greater risk for yield loss due to low germination due to drought (cotton) and increased disease (peanut). In conclusion, moving the seed row closer to a drip lateral had no effect on yield and using 0.5X seeding rates for these crops may not always be economical.