Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/5/2014
Publication Date: 3/13/2014
Citation: Evett, S.R., Oshaughnessy, S.A., Colaizzi, P.D., Schwartz, R.C. 2014. Crop water stress indices correlated with soil water storage: Implications for variable rate irrigation management [abstract]. International Soil Sensing Conference, Houston, TX, March 12-14, 2014.skp
Technical Abstract: Soil water sensing methods are now coming to be used for irrigation scheduling of whole fields. However, newly introduced variable rate irrigation (VRI) systems require information about soil water content in many areas of a field, each called an irrigation management zone. Commonly available soil water sensing systems are either too inaccurate, too expensive or otherwise impractical to apply in the many zones of a VRI scheduling system. Scientists with the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas, evaluated thermal crop water stress indices based on crop leaf temperature to see how well correlated such indices might be to soil profile water content. In particular, an index called the integrated crop water stress index (iCWSI) was shown to be well correlated with soil profile water content determined using the neutron probe (NP) in 48 zones under a center pivot irrigation system. The zones were irrigated at four different levels, from 100% replacement of crop water use on a weekly basis, to dryland (no irrigation). The correlation was weakest when the soil profile water content was determined for the entire 2.4-m depth sensed by the NP. Correlations became stronger as the profile depth considered became more shallow. The greatest correlations were obtained for profile depths in the range from 0.4 to 1.2 m. This made sense since root water uptake was limited to the soil from the surface to 1.2-m depth. Implications are that the iCWSI, determined using thermal sensors mounted on a moving irrigation lateral, may provide a field-wide map of crop water stress that can be useful even if soil water content can only be determined in a few key places in the field. Co-kriging on iCWSI and soil profile water content data may be used to develop maps of soil water content for an entire field.