THE BIOPHYSICAL BASIS FOR SPATIAL VARIABILITY OF YIELD AND QUALITY IN A COTTON PRODUCTION SYSTEM

Authors: Sassenrath, Gretchen; PRINGLE, H.C. LYLE - DREC, MISS. STATE; ALARCON, VLADIMIR - MISS. STATE UNIV.

Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/1/2002
Publication Date: 7/1/2002
Citation: SASSENRATH COLE, G.F., PRINGLE, H., ALARCON, V.J. THE BIOPHYSICAL BASIS FOR SPATIAL VARIABILITY OF YIELD AND QUALITY IN A COTTON PRODUCTION SYSTEM. INTERNATIONAL CONFERENCE ON PRECISION AGRICULTURE ABSTRACTS & PROCEEDINGS. 2002.

Interpretive Summary: To date, farmers in the Mid-South have adopted no standard protocol for scheduling irrigation. Continued success in production and maintenance of profitability are making wise water management techniques ever more important to Mid-South agriculture. To this end, we have undertaken a study to examine irrigation needs on the highly variable soils of the region, with an end to developing improved water monitoring tools and irrigation scheduling techniques. The work detailed in this paper describes a portion of the work examining the environmental changes in cotton crops for different soil conditions, and modifications with irrigation. Water is used for physiological growth processes, and also for evaporative cooling. We find that while water is important for crop success, an overriding consideration may be the impact of temperature changes in non-irrigated canopies. In the absence of adequate water, cotton crops show a marked increase in canopy temperature. This increased temperature leads to decreased fruiting, as a result of both reduced square formation and lower boll retention. The loss of yield for the non-irrigated crop was substantial. The results also show promise in the development of alternative technologies, such as thermal remote sensing, for rapid determination of crop water status. These techniques have been used successfully in arid regions, but have not been adapted for humid growing environments.

Technical Abstract: Canopy microenvironment is dependant on external environmental conditions, and is modified geospatially by soil and crop properties. This study was undertaken to explore the spatial variability of cotton (Gossypium hirsutum) yield and quality, and delineate the underlying biophysical components contributing to that variability. The alluvial soils of the lower Mississippi Delta range from excessively drained sandy loams, to the poorly drained heavy clays. Soil development, which includes frequent flooding, results in extremes in soil conditions occurring as alternating bands of sandy and clayey soils within a single field. These highly variable fields are potentially high yielding, but difficult to manage. We determined the microenvironmental conditions within cotton canopies for various soil conditions altered through management and soil physical properties. Differences in intracanopy temperature in excess of 10 C were observed during the hottest portion of the growing season. Canopies developing on sandy soils with less available water had reduced yields, and poorer fiber quality. While nutrient levels in the sandier soils were greatly reduced, the lack of nutrients appeared to present only a minor limitation to the development of the cotton crop. Lack of sufficient water resulted in a greater limitation to crop development. This has particular relevance when considering development of variable rate prescriptions for highly variable soils. Overriding limitations on water availability may supercede insufficiencies in soil nutrients.