Plant height based evapotranspiration model for eucalyptus

Abstract

Bio-drainage is an environmentally favored cheaper option for managing waterlogged areas and does not involve specialized skills and techniques for design. It may be used for any type of soils and climate without any topographical disturbance where engineering measures may not be economical or practical solution.  It is being recommended for controlling water logging, salinity, intercepting seepage and as an alternative to subsurface drainage for successful crop production. The most common tree recommended for bio-drainage is eucalyptus due to its high ET demand, tolerance to waterlogging, salinity and sodicity. Annual budgeting of ground water extraction is required for designing bio-drainage belt. ET demand of bio-drainage belt is an essential plant input data required for planning and designing of the system. Eucalyptus is the most widely planted hard wood trees over the globe to meet the growing demand of timber and wood products. It is a fast growing tree with maximum annual increments of volume in eight year of its ten year economic life span. It has a very high evapotranspirative demand. A model to predict plant height will be useful in optimizing the tree produce, economic return and rotation period of plantation. A hypothesis was developed later translated to a governing differential equation and solved for height as a function of time. Evapotranspirative demand is the best measure of water use efficiency and over all physiological responses of the tree. With another set of hypothesis a model was further developed to calculate daily ET of eucalyptus tree. Characteristic constants of the models were worked out using lysimetric data for three years. Plant height model predicted maximum plant height of 17.12 m in seven year matching well with reported plant height data. The ET model predicted maximum ET demand in the month of May to be 6.28, 14.96, 39.91, 80.81, 124.89, 158.64, 177.99, 186.62, 189.69 and 190.57 L/day/plant over a period of ten year which fairly resemble with reported ET data.