|BOOKER, JON - Texas Tech University|
|ZARTMAN, RICHARD - Texas Tech University|
Submitted to: Precision Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2015
Publication Date: N/A
Interpretive Summary: Precision agriculture, also known as site-specific management, has evolved into a discipline that involves many aspects of crop production. For example, it includes remote sensing, geospatial data collection, geographic information systems, geo-statistics, and simulation modeling of the many interactions between the soil, the plant and the surrounding environment. However, the one component that unifies all these disciplines is the scale at which measurements are made. The premise is that the measurements should be made at the scale to which the results are to be applied. It follows that for production-scale irrigated cotton system the research-unit is a ¼-mile center pivot that covers 125 acres, i.e., landscape-scale. Management decisions regarding the spatially and temporally variable addition of agronomic inputs must be balanced with environmental interactions across the landscape and require simulation models that operate at the landscape-scale. Such a model is PALMSCot, a grid-based landscape-scale cotton model that captures both the spatial and temporal variability and interactions. For a 33 × 33 feet grid across 125 acres, this represents 5,000 cells, and for each cell the model calculates the input and output of all energy and mass exchanges between the soil-plant and atmosphere. In addition, calculations are made as a function of soil depth, giving a three-dimensional representation of the cotton field. The spatial component is also done as a function of time. For a 120-day cotton-growing season, PALMSCot calculates all energy and mass exchanges about 12,000 times for a 15-minute integration and 170,000 times for a one-minute integration. Thus PALMSCot gives a realistic and accurate spatial and temporal representation of how the cotton plant grows as a function of time while integrating the complexity of interactions that ultimately determine cotton lint yield. Our objective was to compare calculated values of soil water content and crop height with corresponding field measured values at multiple locations across a fine textured, pivot irrigated production cotton field through two growing seasons. The PALMScot model efficiently and correctly calculated soil water and crop height. We therefore conclude that PALMScot provides a site-specific management tool for cotton cropping systems.
Technical Abstract: Site-specific management of cotton (Gossypium hirsutum) cropping systems at the production-scale requires information regarding interactions between soil, plant, weather, and agronomic inputs. Management decisions regarding the spatially and temporally variable addition of agronomic inputs are most efficient when balanced with environmental interactions across the landscape. Landscape-scale cotton models could track these interactions and be integrated into future decision support tools designed to manage variable inputs; however, modeling of cotton systems across the landscape has not been evaluated. Our hypothesis was that the PALMScot model, a grid-based landscape-scale cotton model, would capture spatial and temporal variability and interactions within a 70-ha field throughout two contrasting growing seasons, without adjustment of input parameters for the model. Thus, our objective was to compare values of soil water content and crop height calculated by the PALMScot model with corresponding field measured values at multiple locations across a fine textured, pivot irrigated production cotton field through two growing seasons. The PALMScot model calculated values of soil water and crop height across the field with a mean absolute difference (MAD) for soil water content in the 1.0-m profile = 0.024 m3/m3 and positive modified efficiency coefficients. Values of MAD for crop height were = 0.11 m at all locations in 2010 and 2011. We conclude that PALMScot correctly and efficiently calculated soil water content and crop height across the field, throughout each season, and has potential as a site-specific management tool for cotton cropping systems.