Numerical modeling of waterfluxes in the root zone of a mature pecan orchard

Sanjit K. Deb, Manoj K. Shukla, John G. Mexal

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

Little is known about the root zone soil waterdynamics in irrigated pecan [Carya illinoinensis (Wangenh.) K. Koch] within and outside tree canopies. Simulations were performed using the HYDRUS-1D model to quantify isothermal and thermal waterfluxes in the unsaturated zone of a mature pecan orchard in Las Cruces, NM, with and without root wateruptake. Simulated watercontents and soil temperatures correlated well with measured data at each depth. Isothermal waterflux dominated the soil watermovement in bare soil immediately aft erirrigation, while the contribution of vapor flux increased with increasing soil drying because of upward isothermal and much smallerthermal waterand vapor fluxes within the 20-cm depth. In contrast, isothermal waterflux was predominant throughout the under-canopy soil profile. Actual evaporation from bare soil displayed two distinct stages, immediately aft erirrigation and aft erevaporation continued to fall off with soil drying. Immediately aft erirrigation, trends of under-canopy actual and potential evaporation rates were similar. With the depletion of surface soil water, evaporation losses were lowerand actual transpiration due to root waterextraction substantially contributed to actual evapotranspiration. Relative evapotranspiration (actual/potential ratio) correlated (P < 0.05) with the pecan stem waterpotential. The root wateruptake pattern followed the root length density distribution immediately aft erirrigation. Patterns of uncompensated (waterstress index [ω] = 1.0) and compensated (0.0 < ω < 1.0) root uptake were similar during early periods aft erirrigation. Compensated uptake remained higherunderwater-stressed conditions, and the compensation from the deepersoil profile generally increased for lowervalues of ω, although not consistently for 0.1 < ω < 0.5.

Original languageEnglish
Pages (from-to)1667-1680
Number of pages14
JournalSoil Science Society of America Journal
Volume75
Issue number5
DOIs
StatePublished - Sep 2011

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