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Title: MICROENVIRONMENTAL FACTORS CONTROLLING BOLL DEVELOPMENT IN COTTON: DIFFERENCES WITH IRRIGATION AND SUBSOILING

Author
item Sassenrath, Gretchen
item PRINGLE, H - DREC
item ALARCON, V - MSU

Submitted to: Biological Systems Simulation Group Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/15/2003
Publication Date: 3/15/2002
Citation: SASSENRATH COLE, G.F., PRINGLE, H.C., ALARCON, V.J. MICROENVIRONMENTAL FACTORS CONTROLLING BOLL DEVELOPMENT IN COTTON: DIFFERENCES WITH IRRIGATION AND SUBSOILING. BIOLOGICAL SYSTEMS SIMULATION GROUP PROCEEDINGS. March 2003. Mississippi State, MS. Vol. 32, pg 39-40.

Interpretive Summary: Remote sensing offers the potential for rapid, broad scale monitoring of crop status for improved management decision-making. We explored the potential of remote sensing for use in irrigation scheduling. To date, no reliable remote imagery system has been devised that adequately detects crop water status in the humid growing conditions of the Mid-South. While obvious differences in crop physiological performance are apparent between well irrigated and water stressed canopies, these differences are secondary, and result from extreme water stress. By the time these secondary factors are present, the potential loss to yield and quality is substantial. Since water is used for metabolic function as well as transpirational cooling, inadequate water supply increases the canopy temperature. Thermal sensors are available that remotely sense canopy temperature, and have been successfully deployed in arid regions for plant and soil water monitoring, and irrigation scheduling. However, the high humidity conditions of the Mid-South limit the ability of the plant to cool, and the sampling of a large area under consistent conditions of insolation requires rapid scanning. This study was undertaken to test the efficacy of a thermal sensor in detecting changes in canopy temperature under the humid growth conditions of the Mid-South. The sensor was mounted on a boom that could be positioned into the middle of the test plots and repositioned easily for rapid scanning of the crop canopy. Concurrent measurements of insolation, air temperature and georeferenced position were taken. The system was found to have a reasonably quick and accurate response to canopy temperature. Differences in plant growth with water stress were observed and corroborated with remote imagery.

Technical Abstract: Temperature plays a key role in many aspects of crop development, from seedling establishment to fruit maturation and plant senescence. Cotton (Gossypium sps.) shows significant reductions in growth at temperatures below 15 C, as well as high temperatures. It has been shown that high temperatures are particularly deleterious to boll retention. The canopy structure and plant physiological responses impact the intracanopy microenvironment substantially. High relative humidity may limit the ability of the plants to cool through evaporation, leading to an increase in leaf and canopy temperature. In cotton, the fruits have no mechanism of cooling and remain near the canopy temperature. Because of its role in evapotranspiration, soil water impacts the cooling potential of plants. In this study, we explore the potential of thermal measurements for determination of crop water status in a humid environment. We imposed different soil moisture regimes in controlled test plots through different tillage and irrigation treatments, and monitored soil moisture. Irrigation was supplied at regular intervals with an overhead lateral move sprinkler system. The microenvironment within the canopy was determined by recording soil and air temperature. Additional information on canopy temperature was recorded with an infrared thermometer deployed on a moveable tracking system. Crop performance was measured throughout the season, and yield and quality determined at final harvest. Differences in leaf area, fruit formation, and fruit retention were observed for the different treatments. Differences in canopy reflectance patterns observed with multispectral imagery were corroborated with differences in leaf area and light interception as a function of soil water status. The total lint yield was negatively correlated with cumulative heat units within the canopy.