Project Summaries

12-111TX  Project Manager: E. M. Barnes


J. Tom Cothren, Texas AgriLife Research

Statewide cotton production could be significantly increased and become more stable with improved best management practices focusing on irrigation management and the use of improved drought-tolerant cultivars, as this would reduce the negative impacts of water deficits on yield and lint quality. Primary objectives of this project were: 1) characterize the water economy of a selected group of cotton genotypes provided by AgriLife's breeding programs and seed companies, discern the associated anatomical and physiological attributes controlling their water use, and transfer this information back to breeders and geneticists to advance the development of drought-tolerant cultivars; 2) evaluate the effects of irrigation methods on growth, lint yield, and fiber quality of commercial cotton cultivars in three cotton-growing regions of Texas (Rolling Plains, Brazos Bottoms, and Southern High Plains); and 3) develop quicker and more accurate methods to measure crop growth and leaf area for wider scale studies and potential farm use.

This is a coordinated workgroup project, and this report is specific to objective 2 through an experiment conducted at College Station using a sub-surface drip irrigation system supplying two levels of moisture: 80% and 60% of reference evapotranspiration (ET), plus an non-irrigated treatment. A particular emphasis at this site was to determine if hormone treatment could reduce the impact of drought stress. Ethylene is a naturally occurring plant hormone, implicated in fruit ripening, flower opening, and abscission of vegetative and reproductive structures. More recently, compounds such as 1-methylcyclopropene (1-MCP) have been studied due to their potential benefits in helping alleviate the negative impact of drought and high temperature stresses on crop yield. 1-MCP is widely used in fruit and vegetable markets to delay ripening during shipping and storage. This compound is known to have approximately 10-fold higher affinity for ethylene receptors in the plant when compared to ethylene itself. By binding to these receptors, 1-MCP delays and/or diminishes ethylene effects. The SmartField system recorded daily canopy temperatures and indicated stress levels occurring within the three treatments. Applications of 1-MCP were triggered by four treatments, defined as Control (C), SmartcropTM (S), forecasted maximum temperature of at least 3 days over 95° F (A95), and forecasted maximum temperature of at least 3 days over 100° F (A100).

The total amount of rainfall for the experimental site during 2012 was 41.1 inches, of which roughly half (19.8 inches) of the total precipitation fell within the growing season (from 04/10/12 through 09/04/12). The majority of total daily rainfall was around 0.1 to 0.4 inches. Rainfall events were very well distributed during the period studied and coupled with a few more intense events, were able to maintain soil moisture. For this particular season, rainfall was not considered to be a strong limiting factor for cotton growth and development. Also, due to plentiful water in the soil profile, canopy temperatures remained almost always well below air temperature.

Statistical analysis of water potential measurements failed to demonstrate any significant differences, at the 5% level of probability, among plots within the same irrigation regime (e.g., between plots grown under dryland conditions). Despite the fact that no significant differences were found in final seed cotton yield when comparing treatments and the control within an irrigation regime, it is interesting to note that consistent numerical differences were found. All plots treated with 1-MCP growing under dryland conditions had higher (numerical) yield than the control plots. Under irrigated conditions, the opposite occurred, and all plots treated with 1-MCP had lower (numerical) yield than the control plots. While no statistically significant differences were found, this data may indicate a potential benefit of 1-MCP applications and IRTs as tools to monitor and help alleviate negative impacts of drought and high temperature stresses on final cotton yield. Plant mapping and photosynthetic-related data collected are still being analyzed, and should provide a better insight into the crop responses to the stresses and 1-MCP applications.


Project Year: 2012

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