ISHS Acta Horticulturae 278: Symposium on Scheduling of Irrigation for Vegetable Crops under Field Condition
TIMING OF ONION IRRIGATIONS USING BELLANI ATMOMETERS |
| Authors: | F.D. Moore, A.E. McSay |
| Abstract:
The model requires soil profile recharge information, as well as a measure of evaporative demand ED on a daily basis. An empirically derived coefficient converts Bellani plate atmometer readings, cumulative evaporative demand (  ED) to soil matric potential, SMP. A time extrapolation of a first, second, or third order polynomial selected by a stepwise regression algorithm is used to predict irrigation date based on a user selected SMP threshold, SMPT. Coefficients and thresholds change according to growth stage; currently 0–50 and 50–130 days after planting.
An override of the computer assisted model may be invoked when chronological and physiological times do not coincide.
The ED-SMP model begins forecasting irrigations beginning with the first day after planting.
A unique feature of the model's development is that careful mathematical growth curve analyses were used to quantify beginnings and endings of growth stages. Also, the model includes windows to permit adjustment for available water holding capacity of the soil, soil salinity, and irrigation water quality. Further study is needed in order to properly account for these site specifics. It is suggested that implementation be at the farm level. | |
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