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Root distribution patterns of reticulatus and inodorus melon (Cucumis melo L.) under subsurface deficit irrigation
- Sharma, Sat Pal, Leskovar, Daniel I., Volder, Astrid, Crosby, Kevin M., Ibrahim, A. M. H.
- Irrigation science 2018 v.36 no.6 pp. 301-317
- Cucumis melo, Mollisols, cantaloupes, crops, cultivars, deficit irrigation, developmental stages, evapotranspiration, field experimentation, fruit set, furrows, honeydew, microirrigation, rain, root growth, root systems, screening, Texas
- Information on root growth patterns is crucial to understand cultivar adaptations to deficit irrigation, particularly for subsurface drip-irrigated crops, where root systems are more confined than furrow or sprinkler systems. A 2-year field experiment evaluated the effect of deficit irrigation (50% vs. 100% crop evapotranspiration, ETc) on root growth of melon (Cucumis melo L.) cultivars (Mission, Da Vinci, and Super Nectar) on a mollisol soil in southwestern Texas, USA. Root length intensity (Lₐ; mm cm⁻²), and root length density (RLD; cm cm⁻³) were measured at different growth stages using the minirhizotron and soil core methods, respectively. A higher Lₐ was recorded in 2012 than in 2011 (3.71 mm cm⁻² vs. 0.50 mm cm⁻²), due to differences in temporal distribution of rainfall between years. Overall, deficit irrigation increased Lₐ as compared to 100% ETc, but significant effects occurred at depth (> 40 cm below the soil surface and > 25 cm below the subsurface drip tape). In 2012, moderate water deficit promoted deep root growth at the fruit setting stage but not in 2011, while root growth responses to cumulative deficit varied with cultivar. In 2012, deficit irrigation enhanced root growth in cv. Mission (cantaloupe; reticulatus) throughout the season, it was maintained in cv. Da Vinci (Tuscan; reticulatus), while it decreased in cv. Super Nectar (honeydew; inodorus) at the final harvest stage. Thus, the reticulatus melon cvs. Mission and Da Vinci can better adjust to moderate water-deficit conditions as compared to the inodorus melon cv. Super Nectar. Minirhizotron data provided useful information on root growth dynamics in deeper soil layers in a non-destructive way, which makes it a valuable tool in screening cultivars for water deficit adaptation.