ISHS Acta Horticulturae 664: IV International Symposium on Irrigation of Horticultural Crops
USING INFORMATION FROM SAP FLOW MEASUREMENTS TO IMPROVE SOIL ADAPTABILITY TO DRIP IRRIGATION IN ORCHARDS |
| Authors: | C. Isbérie, B. Cabibel, C. Valancogne, T. Afonso Paço |
| Keywords: | irrigation scheduling, tensiometry, cherry (Prunus avium), peach (Prunus persica), deep percolation, coarse soil |
| Abstract:
If the soil cannot store all the water needed for the crop in the wetted drip irrigation "bulb", one possibility is to irrigate in the daytime, when the crop evapotranspires the most. In this case the soil does not need to store the whole quantity of daily crop water requirements, but only the cumulative difference between supplied and consumed water at each moment. We have studied the example of a 16 hour per day irrigation, i.e. 8 L per hour, and a tree evapotranspiring 130 L/day. On the basis of this experiment, it was possible to estimate the maximum and the minimum amount of water that has to be stored in the soil during an irrigation day: this depends on the hour of irrigation beginning, and of the sap flow variation at each time of the day. In this case, the maximum variation of water content in the zone humidified by drippers was 105 L, for one tree, during one day, while the minimum was only 25 L. So, choosing a good daily irrigation starting hour prevents some difficulties due to the soil, for example, an excessive permeability. Moreover, the water is then always at a high availability level for the crop, except from 6 to 8 p.m., where the cumulative balance of the day is negative; but this only occurs during about 2 hours, and in the evening when the climatic conditions are less harsh. By simulation, this reasoning can be adapted to many cases and another example is given here. It can help the farmer to choose the order to irrigate fields with different soils. This method also allows the limitation of deep percolation under the dripper. | |
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