1a. Objectives (from AD-416):
Study the effects of combined approaches of deficit irrigation scheduling and conservation tillage systems on cotton production in Australia and the U.S. The proposed research is a multi-disciplinary project involving the integration of breeding, whole-plant physiology, soil science, agronomy, and economics to test the utility of an integrated, producer-friendly irrigation scheduling tool in water-limited production environments. Additionally, this research will enhance our knowledge of whole-plant and system (soil and crop) responses to timed irrigation deficits, physiological impacts of these deficits on plant performance, and the resulting impact on yield and quality.
1b. Approach (from AD-416):
1. Field studies comparing irrigation scheduling treatments utilizing a number of different temperature thresholds embedded in the BIOTIC system. The results from these experiments will help to refine the most appropriate threshold for deficit irrigation systems with limited water in different growing environments. 2. Conduct field trials using BIOTIC scheduling approach in isolation and in combination with other crop measures used for irrigation scheduling (e.g., soil moisture, crop factors), and analyze metabolic and physiological response to these irrigation regimes. 3. Deliver to industry a comprehensive assessment of and guidelines for the use of the BIOTIC for irrigation scheduling in water-limited environments to improve yield, quality, and water use and the impacts on conservation tillage and cover cropping systems on cotton production in water-limited environments.
3. Progress Report:
The objective of this project is to study the effects of combined approaches of deficit irrigation scheduling on cotton production in Australia and the U.S. The proposed research is a multi-disciplinary project involving the integration of breeding, whole-plant physiology, soil science, agronomy, and economics to develop an integrated, producer-friendly irrigation scheduling tool. Additionally, this research will enhance our knowledge of whole plant and system (soil and crop) responses to timed irrigation deficits, physiological impacts of these deficits on plant performance, and the resulting impact on yield and quality. The cooperating investigator from CSIRO, Narrabri, NSW, visited CSRL in July to analyze 2010 data, collect data on 2011 Texas field trials, and plan future experiments. As part of this on-going collaboration, we have refined models for crop response to water-deficit using a canopy-temperature based heat unit model. The utility of cotton canopy temperature heat units was assessed by comparing decadal (2000 to 2009) air temperature heat unit variation with variation in canopy temperature heat unit accumulation due to variable irrigation data collected beginning in 2009. Irrigation-induced variation in canopy temperature heat units was similar to the decadal variation in air temperature heat units. Two heat unit-based management tools, 1) the assignment of irrigation crop coefficients and 2) the identification of a fiber thickening period, based on the work of the ARS and CSIRO investigators, were both found to be sensitive to irrigation-induced changes in heat unit accumulation. The inclusion of canopy temperature heat units resulted in variability in both indicators that reflected effects of irrigation and climate on plant performance. Additionally, the approach of the investigators was evaluated using archival data from genotype evaluation experiments for three sites across Texas (Lubbock, College Station, and Corpus Christi) for a period of 10 years from 2000 to 2010. With no modification to the prediction tool to account for regional variation, cultural practices, or cultivar, we were able to account for a significant proportion of the variation across the three sites and years (r2 = 0.35). The CSIRO investigator et al. reported r2= 0.34 for a similar analysis of Australian cotton. We are currently preparing a manuscript to report these findings. To further investigate the utility of a canopy heat unit model, seven sequential sowings of across 4 water levels (rainfed, 1.5, 3.0, and 6.0 mm per day (via SDI)) were established in Lubbock, Texas, at the USDA-ARS research farm. The initial sowing was May 15, and subsequent plantings were in 2-week intervals to achieve a matrix consisting of a range of soil moisture levels and temperature environments to examine the impact of these factors on fiber maturity. Fiber samples were collected for all treatments at the model-predicted heat unit value and at harvest, and submitted to HVI and AFIS analysis (on-going analysis). These preliminary data suggest that inclusion of canopy temperature measurements in heat unit accumulation may improve the utility of heat units. Furthermore, canopy temperature-based heat units may prove to be more mechanistic predictors of temperature effects on cotton growth and development. The practical implementation of a canopy temperature heat unit approach will require additional research to more fully develop the relationships between canopy heat units and crop development.