Comparison of crop stress and soil maps to enhance variable rate irrigation prescriptions

Authors: Vories, Earl; Sudduth, Kenneth - Ken; Evett, Steven - Steve; O`Shaughnessy, Susan; Alejandro, Manuel

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/20/2017
Publication Date: 10/16/2017
Citation: Vories, E.D., Sudduth, K.A., Evett, S.R., Oshaughnessy, S.A., Alejandro, M.E. 2017. Comparison of crop stress and soil maps to enhance variable rate irrigation prescriptions. Proceedings 7th Asian-Australasian Conference on Precision Agricultlure. Paper 170.

Interpretive Summary: Benefits of variable-rate application of agrochemicals, seeds, and nutrients can be partially masked by applying inappropriate amounts of water, and soil variability diminishes the effectiveness of conventional irrigation management. Center pivot irrigation systems can be equipped with variable rate irrigation capability and the systems have been shown to perform dependably. Soils information will need to be supplemented with measures of crop stress for in-season adjustment of irrigation. A field study was conducted by ARS scientists from Portageville and Columbia, Missouri, and Bushland, Texas, at the University of Missouri Fisher Delta Research Center at Portageville to compare soil and in-season stress maps to help determine their relationship. While additional data will be collected and used for statistical comparisons, measurements during the driest part of the growing season demonstrated spatial variability in canopy temperature and an integrated crop water stress index that appeared to be correlated with soil texture. These findings will be used to improve irrigation efficiency in the US and worldwide.

Technical Abstract: Soil textural variability within many irrigated fields diminishes the effectiveness of conventional irrigation management, and scheduling methods that assume uniform soil conditions may produce less than satisfactory results. Furthermore, benefits of variable-rate application of agrochemicals, seeds, and nutrients can be partially masked by applying inappropriate amounts of water. Center pivot irrigation systems can be equipped with variable rate irrigation (VRI) capability and commercial VRI systems have been shown to perform dependably. Soil properties will impact the optimal application rate for a given location, but that information will need to be supplemented with measures of crop stress for in-season adjustment. A field study was conducted at the University of Missouri Fisher Delta Research Center Marsh Farm at Portageville in 2016 with the objective to compare soil and in-season stress maps to help determine their relationship. Apparent soil electrical conductivity (ECa) data were used to estimate the clay content and infrared thermometers (IRT) were suspended from the center pivot system to measure canopy temperature. While much of the growing season had adequate rainfall that prevented high water deficit stress levels, measurements on 5 July demonstrated spatial variability in canopy temperature and an integrated crop water stress index (iCWSI) that appeared to be correlated with soil texture. While seed cotton yield incorporated more than just the factors discussed in this report, areas of lowest clay content corresponded with the lowest yields. Additional data will be collected under a range of conditions and used for statistical comparisons of the observed effects.