Our Agro-Ecology and Cropping Systems program focuses on the ecophysiological mechanisms of soil-plant-water interactions for improving water use efficiency and soil health in cropping systems. Our main research areas are:
- Characterization of plant traits for improved water acquisition, adaptation and resistance to abiotic and biotic stresses;
- Application of ground-based sensors for remote detection of soil, plant root and canopy features;
- Quantification of soil parameters that indicate microbial and root activities under natural and managed ecosystems; and
- Quantitative models that describe soil water movement, plant root water uptake in agricultural soils.
Shoot and Root Traits to Enhance Crop Growth
In the winter wheat varieties tested at the Uvalde center, the top two ‘picks’ were ‘TAM 305’ and ‘TAM 304’ out of 10 varieties evaluated. Two of the varieties: ‘TAM 112’ and ‘Fannin’ yielded the lowest, due to susceptibility to leaf rust infection. In relatively wet years, planting winter wheat under deficit irrigation or dry-land would not cause a significant yield loss in southwest Texas. Based on field tests conducted in Uvalde and Amarillo, we found a better way to predict leaf water use efficiency. Rather than evaluating the bulk leaf carbon isotopes, the team found leaf wax alkane concentration and compound-specific carbon and hydrogen isotopes best for predicting water use.
Our studies on corn and sorghum found after a two-year field study focused on the leaf and canopy traits that some of the modern corn genotypes achieved a water use efficiency that is 30% higher than sorghum genotypes when planted in the same field in southwest Texas.
Recently, in a study, we did on cotton we found in a field performance test of 12 commercial cotton varieties in Uvalde that a 35% reduction in the amount of irrigation did not affect seed cotton yields, but reduced fiber quality, such as fiber strength, fiber length, and elongation. The diminished fiber quality was prevalent with increased leaf dry matter content rather than leaf osmotic potential.
Field Phenotyping for Crop Improvements
We obtained an initial success in detecting fine root biomass of winter wheat and energy cane using the ground penetrating radar (GPR) system attached with a 1600 MHz antenna. This progress provides hope for predicting crop fine root biomass remotely under field conditions.
In collaboration with wheat breeders, we are developing methods for predicting leaf rust infection rate using ground-based phenotyping methods. We demonstrated that canopy reflectance at red-edge band reflects the presence of leaf rust in winter wheat during the flowering stage.
We are currently developing regression models to link the leaf water potential of field crops based on normalized difference vegetation index (NDVI) obtained from ground-based phenotyping tools. This will assist in crop improvement through rapid characterization of drought tolerance capacity of crop genotypes under field conditions.
Soil Management to Improve Water Use Efficiency
In our studies on soil management, we have found that deficit irrigation in early growing stages for cotton can promote root growth and save 16% of irrigation water over five years without reducing cotton lint yield. In a long-term cropping system experiment, we found using strip-tillage resulted in an increase in cotton and corn crops. In a study of tomato plants planted in soils affected by salinity and sodicity we discovered that several soil quality guides, from soil electrical conductivity to aggregate stability and infiltration rates, improved over a period of four months. Our current study is incorporating winter cover crops into the cropping system with different tillage regimes to improve soil health and cash crop productivity.
Crop Modeling to Increase Crop Production Efficiency
Our study of crop modeling is deepening our understanding of the process of transpiration by linking stomatal conductance to canopy energy transfers for field crops. Additionally, we are identifying options for improving cropping system productivity by using the DSSAT-Cropping System Models under various scenarios of water/fertility management and crop rotations. This study is helping us to characterize water use patterns of major field crops, such as corn, cotton, wheat, and sesame, by measuring and modeling root zone processes that govern water movement and transfer under field conditions and develop optimal irrigation scheduling tool for field crops considering rainfall uncertainty.
- Y. J. Zhang, M. Y. Hou, H. Y. Xue, L. T. Liu, H. C. Sun, C. D. Li and X. J. Dong. 2018. Photochemical reflectance index and solar-induced fluorescence for assessing cotton under water-deficit stress. Biologia Plantarum 62: 817-825. DOI: 10.1007/s10535-018-0821-4
- X. Liu, X. Dong, Q. Xue, D.I. Leskovar, J. Jifon, J.R. Butnor and T. Marek. 2017. Ground penetrating radar (GPR) detects fine roots of agricultural crops in the field. Plant and Soil 423: 517-531 https://doi.org/10.1007/s11104-017-3531-3
- X. Liu, S. Feakins, X. Dong, Q. Xue, T. Marek, D.I. Leskovar, C.B. Neely and A.M.H. Ibrahim. 2017. Experimental study of leaf wax n-alkane response in winter wheat cultivars to drought conditions. Organic Geochemistry 113: 210-223.
- X. Liu, X. Dong and D. I. Leskovar. 2016. Ground penetrating radar for underground sensing in agriculture. International Agrophysics 30: 533-543. doi: 10.1515/intag-2016-0010
- Leskovar, Y. Othman, and X. Dong. 2016. Strip tillage improves soil biological activity, fruit yield and sugar content of triploid water melon. Soil & Tillage Research 163: 266-273 https://doi.org/10.1016/j.still.2016.06.007
- X. Dong, W. Xu, Y. Zhang, D. Leskovar. 2016. Effect of irrigation timing on root zone soil temperature, root growth and grain yield and chemical composition in corn. Agronomy 6, 34. doi: 10.3390/agronomy6020034
- X. Dong. 2016. How to put plant root uptake into a soil water flow model. F1000Research 5,43 doi: 10.12688/f1000research.7686.1
- Z.-S. Zhang, X.-J. Dong, B.-X. Xu, Y.-L. Chen, Y. Zhao, Y.-H. Gao, Y.-G. Hu and L. Huang. 2015. Soil respiration sensitivities to water and temperature in a revegetated desert. Journal of Geophysical Research – Biogeosciences 120: 773-787 DOI: 10.1002/2014JG002805
- X. Dong and B. D. Patton. 2015. Predicting soil water retention curves based on particle-size distribution using a Minitab macro. African Journal of Soil Science 3(1): 079-085.
- X. Dong, J. Patton, L. Gu, J.-Z.Wang and B. Patton. 2014. Leaf photosynthesis and plant competitive success in a mixed-grass prairie: With reference to exotic grasses invasion. Journal of Ecosystem & Ecography 4: 152. doi:10.4172/2157-7625.1000152.
- X. Dong, D. Leskovar, K. Crosby and T. Marek. 2014. Quantifying crop water use in arid and semi-arid regions: Opportunities based on soil-plant water relations. Journal of Arid Land Studies 24-1: 141-144.
- Y. Sun, L. Gu, R. E. Dickinson, S. G. Pallardy, J. Baker, Y. Cao, F. M. DaMatta, X. Dong, D. Ellsworth, D. Van Goethem, A. M. Jensen, B. E. Law, R. Loos, S. C. V. Martins, R. J. Norby, D. Weston, K. Winter. 2014. Effects of mesophyll conductance on fundamental photosynthetic parameters and their relationships estimated from leaf gas exchange measurements. Plant, Cell & Environment 37: 978-994.
- X. Dong, J. Patton, G. Wang, P. Nyren and P. Peterson. 2014. Effect of drought on biomass allocation in two invasive and two native grass species dominating the mixed-grass prairie. Grass and Forage Science 69: 160-166.
- W.-H. Wang, J. Chen, T.-W. Liu, J. Chen, A.-D. Han, M. Simon, X.-J. Dong, J. He, H.-L. Zheng. 2014. Regulation of the calcium-sensing receptor in both stomatal movement and photosynthetic electron transport is crucial for water use efficiency and drought tolerance in Arabidopsis. Journal of Experimental Botany 65: 223-234
- M. A. Liebig, S. L. Kronberg, J. R. Hendrickson, X. Dong, and J. R. Gross. 2013. CO2 efflux from long-term grazing management systems in a semiarid region. Agriculture, Ecosystems & Environment 164: 137-144.
- X. Dong, F.-C. Cheng, D.-J. Wang, G.-J.Wang, B. D. Patton and P. E. Nyren. 2013. Mixed-grass prairie rhizome biomass is influenced by cattle grazing intensity. Grass and Forage Science 68: 199-204.
- X. Dong, B. Patton, A. Nyren, P. Nyren and L. Prunty. 2010. Quantifying root water extraction by rangeland plants through soil water modeling. Plant and Soil 335: 181-198.
- X. Dong, P. Nyren, B. Patton, A. Nyren, J. Richardson and T. Maresca, 2008. Wavelets for agriculture and biology: A tutorial with applications and outlook. BioScience 58: 445-453.
- Patton, X. Dong, P. Nyren and A. Nyren, 2007. Effect of grazing intensity, precipitation and temperature on forage production. Rangeland Ecology and Management 60: 656-665.
- X. Dong and X. Zhang. 2001. Some observations of functional adaptations of the sandy shrubs to the arid environment in the Mu Us Sandland: leaf water relations and anatomic features. Journal of Arid Environments 48: 41-48.
- X. Dong and X. Zhang. 2000. Special stomatal distribution in Sabina vulgaris in relation to its survival in a desert environment, Trees: Structure and Function 14: 369-375.