Location: Water Management and Conservation Research
Project Number: 2020-13660-009-011-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Oct 1, 2022
End Date: Jun 30, 2023
In this research, we are conducting field studies to investigate the effects of a more efficient irrigation system (gravity drip) on crop water use, growth, and yield of cotton and guayule. For cotton, the main objective is to evaluate cotton water use, growth and yield under different irrigation rates (4.0, 3.0 and 2.0 acre-ft per season) and methods (gravity drip and furrow). Specific objectives of the cotton experiment are to 1) determine the optimum irrigation rate for cotton under gravity drip irrigation compared to flood, 2) determine the best irrigation system for germination and establishment, 3) use remote sensing based crop coefficients for irrigation water management of cotton, and 4) calibrate the PR2 soil moisture sensor using a neutron moisture meter and gravimetric soil water content data. For guayule, the main objective is to evaluate guayule water use, growth and yield under different irrigation rates (2.5, 2.0 and 1.5 acre-ft per season) with gravity drip and one rate (2.5 acre-ft) with flood irrigation. Specific objectives are to 1) determine the optimum irrigation rate for guayule under gravity drip irrigation compared to flood and 2) determine the best irrigation system for germination and establishment.
The cotton field experiment will be conducted at the University of Arizona's Maricopa Agricultural Center (MAC) near Maricopa, Arizona (33.07° N, 111.97° W, 361 m above sea level) in a 3.7-acre field. The experiment will include four irrigation treatments and three irrigation rates: 1) D4.0 [drip, 4.0 acre-ft], 2) D3.0 [drip, 3.0 acre-ft] and 3) D2.0 [drip, 2.0 acre-ft], and F4.0 [furrow, 4.0 acre-ft]. The field consists of a total of 12, 100-m long plots that will be 6.05 m wide each. Irrigation treatments will be arranged in a randomized complete block design. The field will be divided into three blocks, and four irrigation treatments will be randomly assigned within each block. The gravity drip irrigation system will be installed two weeks before planting. The system will be buried about 2”-4” below soil surface. The system is designed such that all three replicates of each treatment are connected and irrigated together. A flow meter will be installed to monitor water applied to each treatment. Access tubes for the PR2 and neutron moisture meter will be installed in each plot. Soil moisture data will be collected once a week then data will be used to determine soil water depletion. A soil water balance irrigation model will be used for irrigation scheduling. Plant growth parameters (canopy height and width) will be collected manually once a week from three different locations in each plot to monitor plant growth. Also, remote sensing data will be collected once a week by a small unmanned aircraft system carrying a multispectral sensor (Mica-Sense Altum) that has six bands (Blue, Green, Red, Near-Infrared, Red-Edge and thermal). Images will be processed using image processing software (Pix4DMapper). Then vegetation indices will be calculated and used for the prediction of crop coefficient, plant parameters and cotton yield. We expect that the use of the gravity drip irrigation system will result in saving at least 25% of water compared to flood irrigation while having the same or even better yield. Results will be presented in meetings and published in extension publications and peer reviewed journals.