Plant Growth Pecan Model



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Model Description
Theory
              Pecan Plant Growth Model without nitrogen stress
               Pecan Plant Growth Model with nitrogen stress
Flow Chart for Model
               Pecan Plant Growth Model without nitrogen stress
               Pecan Plant Growth Model with nitrogen stress
Input for Model
               Pecan Plant Growth Model without nitrogen stress
               Pecan Plant Growth Model with nitrogen stress
Acquistion of Climate data
                 New Mexico Climate Center - full climate data base- Air Temperature, Humidity, Windspeed, Solar Radiation, rainfall to calculate Penman-Montheith Reference Evapotranspiration
               NCDC- climate data of Air temperature and rainfall to calculate Samani-Hargraves reference evapotranspiration
Inputs to model
              Pecan Plant Growth Model without nitrogen stress
              Pecan Plant Growth Model with nitrogen stress
Down load model ( This is an excel object based model and requires excel to run)
               Pecan Plant Growth Model with nitrogen stress , Oklahoma simulation
              Pecan Plant Growth Model with nitrogen stress , Texas simulation
Development of a Pecan model

Pecans [Carya illinoensis (Wangenh.) C. Koch] are an important cash crop in arid southwestern USA. The pecan is an alternate bearing tree and its water use is greater than that of most row crops. Irrigation, pruning amount, and timing must be effectively managed to reduce alternate bearing for maximum profits. A simulation model of pecan growth and yield is a potential tool for managing irrigation and pruning amounts and timing. An object based pecan growth model was developed and validated to simulate daily pecan tree dry matter production, biomass allocation to leaves, nuts, trunk, and branches, and alternate bearing according to inputs of weather data, soil condition, irrigation, and pruning operations. Daily dry matter production per unit of evapotranspiration (water use efficiency) was calculated as a function of average vapor pressure deficit. Biomass allocation functions were derived from tree growth measurements at an orchard near Las Cruces, NM. Alternate bearing was simulated as a function of the level of root starch reserves. It was theorized that the setting of pistillate flowers and subsequent nut yields are proportional to the level of root starch reserves in the preceding dormant phase (winter). Mathematical functions for the effects of irrigation and pruning on tree growth and yield were derived from the literature and available data.
Modification of the Pecan Model was made to include the nitrogen balance in the root zone, nitrogen uptake by the roots and nitrogen stress in the leaves that causes photosynthesis and evapotranspiration to decrease due to nitrogen stress.