Author
 |
Pettigrew, William |
|
Dowd, Michael |
|
Submitted to: Journal of Cotton Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 10/15/2014 Publication Date: 12/30/2014 Citation: Pettigrew, W.T., Dowd, M.K. 2014. Nitrogen fertility and irrigation effects on cottonseed composition. Journal of Cotton Science. 18:410-419. Interpretive Summary: Agricultural production inputs have steadily increased in prices during the past few years. Two inputs closely tied to price of fossil fuels, nitrogen fertilizer and irrigation, have seen considerable cost increases. Natural gas is used in the manufacture of most nitrogen fertilizers and diesel is used to power many of the irrigation pumps throughout the cotton production belt. Previous research has demonstrated how varying the irrigation regime or nitrogen fertilization rate impacted lint yield, yield components, and fiber quality. Although cotton producers receive the predominate portion of their income from lint production, the cottonseed produced has become an increasingly important additional revenue stream. In this study, ARS scientists at Stoneville, MS, and New Orleans, LA, conducted research to address how varying irrigation regimes and levels of nitrogen fertilization affected the composition of the cottonseed produced. Four cotton varieties were grown under either irrigated or non-irrigated conditions and treated with one of three nitrogen fertilization levels (0 lbs N acre-1, 50 lbs N acre-1, and 100 lbs N acre-1). Few variety interactions with either irrigation or nitrogen were detected. Irrigation increased the level of oil, but decreased the seed protein content. Unfortunately, irrigation also increased the seed gossypol concentration, a compound that is toxic to most mammals. In contrast, the highest rate of N fertilization increased the protein concentration, but decreased the seed gossypol and oil content. Appropriate irrigation and nitrogen fertilization offer the potential for improved yields, but these yield increases come with altered cottonseed composition. Although genetics still plays the predominant role in the determination seed composition, it is important to understand how production input allocation decisions and environmental influences impact cottonseed composition. Agronomists, crop physiologists, extension personnel, consultants, and producers will be able to utilize information from this research as an unbiased source of information to make decisions about input allocations for cotton production. Technical Abstract: Cottonseed products have become a valuable secondary revenue source for cotton (Gossypium hirsutum L.) producers, but how production practices impact cottonseed composition is not clear. This research evaluated how cottonseed composition was altered by varying irrigation and nitrogen fertilization regimes. Four cotton cultivars were grown from 2010 through 2012 under irrigated or dryland conditions and given a treatment application of either 0 kg N ha-1, 56 kg N ha-1, or 112 kg N ha-1. Ginned seed from the plots were analyzed for protein, crude oil, gossypol, soluble carbohydrates, and the oil’s fatty acid distribution. Few cultivar interactions with either irrigation or fertilization were detected. Irrigation increased seed gossypol (18%) and oil (8%) concentrations, but decreased protein levels (13%). In contrast, the highest rate of N fertilization increased protein concentration (18%) but decreased gossypol (14%), oil (9%), and soluble carbohydrate (3%). In addition, N fertilization shifted distribution of unsaturated fatty acids toward less linoleic acid and more oleic acid. Practices growers implement to optimize lint production, in most instances, also improve many of the seed composition traits. |
