Abstract
High air temperatures during the crop growing season can reduce harvestable yields in major agronomic crops worldwide. Repeated and prolonged high night air temperature stress may compromise plant growth and yield. Crop varieties with improved heat tolerance traits as well as crop management strategies at the farm scale are thus needed for climate change mitigation. Crop yield is especially sensitive to night-time warming trends. Current studies are mostly directed to the elevated night-time air temperature and its impact on crop growth and yield, but less attention is given to the understanding of night-time soil temperature management. Delivering irrigation water through drip early evening may reduce soil temperature and thus improve plant growth. In addition, corn growers typically use high-stature varieties that inevitably incur excessive respiratory carbon loss from roots and transpiration water loss under high night temperature conditions. The main objective of this study was to see if root-zone soil temperature can be reduced through drip irrigation applied at night-time, vs. daytime, using three corn hybrids of different above-ground architecture in Uvalde, TX where day and night temperatures during corn growing season are above U.S. averages. The experiment was conducted in 2014. Our results suggested that delivering well-water at night-time through drip irrigation reduced root-zone soil temperature by 0.6 °C, increase root length five folds, plant height 2%, and marginally increased grain yield by 10%. However, irrigation timing did not significantly affect leaf chlorophyll level and kernel crude protein, phosphorous, fat and starch concentrations. Different from our hypothesis, the shorter, more compact corn hybrid did not exhibit a higher yield and growth as compared with taller hybrids. As adjusting irrigation timing would not incur an extra cost for farmers, the finding reported here had immediate practical implications for farm scale adaptation to hot environments.
Highlights
Warming during the crop growing season has been shown to reduce grain yields for major crops such as corn, wheat and soybean worldwide [1,2,3,4,5]
We propose that a corn crop production system with an improved harvest index and water use efficiency, defined as the amount of marketable biomass obtained per unit of water transpired per unit of land area during the crop season, should use corn hybrids with compact plant architecture and irrigation should be applied at a night time to reduce night soil temperature
Soil temperatures measured at Uvalde, Texas at the top 10 cm were lower under night-time drip irrigation, when compared with day-time irrigation, as seen in the soil temperature time series during 8–13 June 2014 (Figure 2)
Summary
Warming during the crop growing season has been shown to reduce grain yields for major crops such as corn, wheat and soybean worldwide [1,2,3,4,5]. Crop growth and yield in response to warming depends on the nature and extent of plant acclimation to high temperature stress [12,13,14]. To mitigate the negative impact of increased growing season temperatures on crop growth and yield, especially in low latitude regions, heat- and drought-tolerant crop varieties, as well as modified farm management practices are needed, especially for the areas when irrigation is needed for crop production and irrigation water depends on the underground aquifers. In C4 plants such as corn, excessive photorespiration under high heat and high light conditions is limited
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