Understanding Root Zone Soil Water Dynamics to Improve Root Water Uptake in Semi-Arid Cotton Systems

Date

2022-12

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Abstract

Understanding spatial and temporal patterns of root water uptake (RWU) in semiarid cotton (Gossypium hirsutum L.) fields under subsurface drip irrigation is critically challenging due to the complexity of interactive water flow, heat transport, root growth, and RWU processes and the difficulties associated with the field measurements of these multidimensional processes. However, using the numerical simulation model, such as the multidimensional numerical model HYDRUS (2D/3D) and the agricultural systems model Root Zone Water Quality Model (RZWQM2), can provide alternative tools to understanding the root zone water dynamics to address efficient soil water management in subsurface drip-irrigated cotton in semiarid environments, especially in West Texas. Therefore, the overall objective of this study was to understand the root zone soil water dynamics in upland cotton grown under subsurface drip irrigation and different agronomic practices using both multidimensional numerical and agricultural systems models. The specific objectives of this study were to (i) simulate root zone soil water dynamics under cotton-silverleaf nightshade competitive interactions in subsurface drip-irrigated cotton using the numerical simulation model HYDRUS (2D/3D) (chapter 2); (ii) evaluate the applicability of both numerical model HYDRUS (2D/3D) and agricultural system model RZWQM2 in analyzing root zone soil water dynamics and RWU processes of cotton grown under deficit subsurface drip irrigation in a semiarid environment (chapter 3); (iii) analyze and model the interactive effects of dynamic soil water and soil thermal environments (i.e., the moisture-thermal regime of soils) on the growth, development, yield and quality of early-season planted subsurface drip-irrigated cotton germplasms with cold germination ability (chapter 4), and (iv) evaluate and model interactive effects of dynamic soil water and soil thermal environments on the growth, development, yield and quality of early-season planted subsurface drip-irrigated cotton germplasms in biochar amended soils. This study reported that the validated HYDRUS (2D/3D) model simulations were found to agree with the measured volumetric water content, soil temperature, and soil water potential and their temporal variation at different soil depths under the cotton plant (CP), silverleaf nightshade (Solanum elaeagnifolium) plant (SNP) and cotton and silverleaf nightshade plants together (CP-SNP) treatments. The maximum RWU, evapotranspiration, and cumulative flux were in the order of CP-SNP > SNP >CP. A maximum value of RWU was observed for CP-SNP throughout the growing season, mainly during the cotton's leaf development and flowering stages, when RWU rates of the cotton-silverleaf nightshade root systems were the main contributor to actual evapotranspiration. Therefore, the timely management of silverleaf nightshade control measures during this period is critical to manage efficient soil water use for cotton and prevent potential yield losses. The study suggested that the HYDRUS (2D/3D) model provides an alternate tool for evaluating dynamic competitive water uses and RWU rates and determining cotton water stress and critical competition period of cotton growth stages under the cotton-silverleaf nightshade interactions in subsurface drip irrigated upland cotton production system to implement efficient water management and weed control measures. This study suggested that the HYDRUS (2D/3D) and RZWQM2 model simulations, calibrated and validated against field measurements (i.e., soil water content, soil water potential, and soil temperature data at different soil depths), agreed well with measured volumetric water contents, soil temperatures, and soil water potentials and their temporal variations at different soil depths for four different deficit subsurface drip irrigation levels or treatments, i.e., i) 50 mm (I1), ii) 130 mm (I2), iii) 200 mm (I3), and iv) 280 mm (I4). Actual transpiration (i.e., RWU rates) and evapotranspiration flux and their cumulative values predicted by both the models were in the order: I1 < I2 <I3 <I4, which could be explained by the enhanced root growth in I4 treatment as indicated by the higher root length density and maximum root length in I4 compared with other deficit irrigation treatments (i.e., I1, I2, and I3). Relative Evapotranspiration (i.e., simulated soil stress conditions) values predicted by the HYDRUS (2D/3D) and RZWQM2 correlated with the measured stem and leaf water potentials and further validated both models’ applicability of determining cotton water stress under different deficit subsurface irrigation levels. Multi-model simulations for semiarid cotton systems under different deficit subsurface drip irrigation levels suggested that both the HYDRUS (2D/3D) and RZWQM2 models could be used as alternate tools for effectively addressing efficient water management issues under water-limited cotton production systems. This study reported that Gossypium Diversity Reference Set (GDRS) accessions and FA mutant cotton germplasms (FA 306-8, FA 301-3, SA 3781, SA 1766, SA 0881, SA 1156) and 6X grown under early planting dates performed reasonably well for their seedling emergences and seedling development, physiological growth responses (plant height, LAI, and photosynthesis and transpiration rates), lint yields, and fiber quality parameters (Micronaire value, Uniformity, Bundle Strength (HVI test), and Short Fiber Content by Number, Fineness, and Maturity (AFIS test)). However, there was no significant difference among treatments for physiological growth responses of all the cotton germplasms with cold germination ability. The HYDRUS (2D/3D) numerical model, further calibrated (i.e., optimized both water flow and heat transport parameters) and validated against field measurements (i.e., soil water content and soil temperature data at different soil depths), predicted the temporal variations in the soil thermal-moisture regimes and its effects on the soil water dynamics and responses (i.e., seedling emergence, growth, and development, fiber quality) of early-season planted (at 15-day intervals for four planting dates beginning from April 5) subsurface drip-irrigated cold-tolerant cotton germplasms. The results suggested that the HYDRUS (2D/3D) could provide an effective research tool to analyze the interactive effects of temporal variations in soil water and soil thermal environments under semiarid climatic conditions for exploring the optimized soil moisture-thermal regimes (i.e., soil water dynamics coupled with heat transport, root growth, and RWUprocesses) that could enhance the plant growth and development, and yield and fiber quality of early-season planted cotton germplasms with cold ability. In this study, the cotton germplasms FA 301-3, FA 306-8, and 6X grown under early planting dates following the application of two different rates of Biochar amendments, i.e., Biochar @10 t ha-1 and Biochar @ 20 t ha-1 performed reasonably well for their seedling emergences and seedling development; however, no significant difference was observed among the planting dates and cotton germplasms during the first year of the experiment. The results suggested that the HYDRUS (2D/3D), further calibrated (i.e., optimized both water flow and heat transport parameters) and validated against field measurements (i.e., soil water content and soil temperature data at different soil depths), could be an effective tool to analyze the interactive effects of temporal variations in soil water and soil thermal environment under semiarid climatic conditions for exploring the optimized soil moisture-thermal regimes and evaluating root zone soil water dynamics in the soil-plant-atmosphere systems that could enhance the plant growth and development, and yield and fiber quality of early-season planted cotton germplasms with cold ability in biochar amended soils. Overall, this study conducted in multiple (from 2017 to 2021) cotton growing seasons under different soil textures suggested that both models used in this study (HYDRUS (2D/3D) and RZWQM2), especially the HYDRUS (2D/3D) could provide effective tools to analyze and model the root zone soil water dynamics of upland cotton grown under subsurface drip irrigation and different agronomic management practice considerations or scenarios for addressing efficient soil water management and conservation issues under the spatio-temporal variability of soil moisture and thermal regimes in semiarid environments.


Embargo status: Restricted until 01/2024. To request the author grant access, click on the PDF link to the left.

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Keywords

Cotton, HYDRUS (2D/3D), Root Water Uptake

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