Precision irrigation management of apple with an apple-specific Penman-Monteith model

Irrigation is essential for preventing water stress and small apple fruit size during dry summers that may occur even in humid climates like New York State. The use of the normal crop coefficient for apples has usually over-estimated water use in our climate with variable humidity. So, we eliminated the crop coefficient method and to overcome this problem we have developed an apple-specific Penman-Monteith model to calculate water use by apple trees. The new Cornell apple evapotranspiration model estimates more accurately apple tree water use from a discontinuous orchard. We have integrated the tree water use model into a new water balance irrigation model (Cornell Apple Irrigation Model) at a Cornell Internet site for use by apple growers in the northeastern USA. The model uses weather data from the network of grower owned weather stations to estimate water use by the trees, water input from rainfall, net water balance and micro-irrigation scheduling based on soil type. The model begins calculating water requirements at green tip stage and is scaled for each day of the growing season based on a leaf development curve. It also considers the effective rooting area of different age orchards to include only the portion of the effective rainfall.