Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 3, 1997
Publication Date: N/A
Interpretive Summary: Nitrogen fertilizer is an important factor that cotton farmers must consider. Nitrogen is necessary for cotton to grow and produce good quality lint and seed, but too much nitrogen can cost the farmer money and cause water pollution. Nitrogen for crop production can come from the previous crop such as peanut, but it is more commonly added as fertilizer. Buried microirrigation tubing is a good method of incremental application of both nitrogen and water. The tubing can be buried in every row or in alternate middles. The water and nitrogen needs of the plant can be predicted by use of computer models. We conducted a four-year study to determine if peanut rotation, alternate middle buried microirrigation, and computer modeling of the plant's water and nitrogen needs would be good for crop production and reduction of excess nitrogen. Peanut did not help the nitrogen balance. The use of alternate middle microirrigation and the computer model reduced the amount of nitrogen applied by 36%. It also produced 2.3 bales per acre, which was equal lint and seed yields to the standard nitrogen management.
Technical Abstract: Cotton production, profitability, and environmental compatibility require good management of N and water. Precise applications of N and water by use of buried microirrigation and the GOSSYM/COMAX (GC) cotton growth model/expert system were investigated. Cultivar PD 3 was planted in May of 1991 through 1994 in peanut/cotton rotations and continuous cotton treatments. Each cropping-treatment split had eight sidedress-N and water treatments arrayed in a randomized complete block design with four replications. Each plot had eight, 0.96-m wide rows. Microirrigation laterals were buried 0.30 m below the soil surface either directly under each row (IR) or under the alternate row middles (AM). Sidedress-N was applied via microirrigation in one 112-kg/ha application (STD); five, 22-kg increments (INC); or 11- to 22-kg/ha increments when required by GC. The rotation treatment did not significantly affect any of the measured parameters. The IR-STD was the highest in seed N content, and it was better than expected for excess N returned to the soil (32 kg/ha/yr) as well as lint production (2.02 Mg/ha/yr). The AM-GC treatment was superior to the IR-GC for uptake of N (113 vs. 76 kg/ha/yr). The AM-GC treatment would be the treatment of choice; it had a lint yield of 1.26 Mg/ha, conserved N better than the irrigated STD or INC treatments, and had less capital cost than the IR-GC.