DRIP IRRIGATION IN LOIRE VALLEY ORCHARDS (FRANCE): ADVANTAGES AND LIMITS
The growing scarcity of water urges growers to develop new methods of irrigation scheduling. In the same experiment several methods were tested: soil tensiometers (a), predawn leaf water potential (b), daily micrometric variations of trunk diameters (c) and weekly measurements of the fruit growing (d).
The (a) method is suitable in a normally rainy year and it can be automated. On the contrary tensiometers fell down during the 1989–1991 years specially in clayey or very sandy soils. The (b) and (c) methods are not very acute. They are difficult to make use of. And they apply to vegetative parts whose behaviour towards hydric stress is somewhat different from fruits. The safest method is to follow regularly the swelling of the fruits (d) but it is very demanding. Its automation is possible but expensive.
Consequently a very acute microirrigation scheduling seems possible but because of the cost and the growing complexity of measurements, it should be kept for a few orchards in charge of collecting data by crosschecking through different methods for a regional warning network.