Olive irrigation with water deficit.

Pastor M-C M, Hidalgo M. J J, Hidalgo M. J C, Vegas M. V. Olive irrigation with water deficit.

 IFAPA, Ministry of Innovation, Science and Business. Córdoba. Agricultural Advisory Service: Rural Caja Jaén. Industrial Estate. Real Mancha. Spain.

The availability of water for irrigation is scarce in most Spanish olive-growing areas. This research has attempted to quantify the influence of irrigation on the production of olive oil mill, studying the response to deficit irrigation treatments, trying to develop management strategies that optimize the use of scarce water resources. Deficit irrigation of olive allows substantial improvement of rainfed crop production. With respect to maximum ETM irrigation, irrigation deficit allows improving water use efficiency in the production of oil. Intensive plantations provide greater efficiency than traditional. We must say, finally, that good results can be generalized only to situations that have  availability of deep soils with adequate holding capacity and adequate average rainfall.

For eight years, fall 1995-2003, there have been two field experiments on farms Pichilín and Cortijo La Loma, both in the province of Jaén. In the first one we worked on intensive olive using  204 olives / ha of 25 year old variety ‘Picual’ and the second, in an centenary olive grove traditional using 64 olive trees / ha, also of that variety. In the two trials comparing the rainfed with four strategies different drip irrigation. The treatments were as follows:

a) cultivation in rainfed taken as reference                                                             b) irrigation for maximum ETc = ETM, applying the water balance methodology proposed by FAO (Doorenbos and Pruitt, 1977). To calculate the ETM crop, the term was used fortnightly (Orgaz and Fereres, 2001): ETc = ETo x Kc x Kr                                                            c) 1500-I, strategy is to apply annually to 1500 m3/ha in the traditional olive grove and 2500 m3/ha in the intensive irrigated during the period 15 September to 15 April plus a support irrigation of about 2 m3/olivo in pit hardening in July, according to the authorizations of CHG.           

d) 1500 – L, irrigation with a weekly application of constant water during March 1 to October 31, with a total water requirements  of 1500 m3/ha/year in the traditional olive and 2,500 m3/ha/year in intensive independent annual climatic conditions.                                        e) deficit irrigation, applying 750 m3/ha in traditional olive and 1,250 m3/ha in intensive attempts to avoid severe stress at times of maximum sensitivity to water deficit: before flowering and during fruit set , hardening of the bone and finally fall during ripening.

In both experiments we used an experimental design in randomized blocks, with three basic plots of 12 olive trees, 3 rows of 4 trees for each irrigation treatment, in which the two central trees monitored. Although it is considered that the olive tree is very tolerant to drought, the crop responds dramatically to irrigation, and when it reaches its maximum capacity can consume quantities of water that are close to those used for other woody crops irrigated as citrus and fruits, depending mainly consumption under distance of plantation and the volume of treetops and the zone where the olive is cultivated (ETo values and different PE), so it is not advisable extrapolations to large geographical areas with different climatic characteristics. When the availability of irrigation water are limited and are lower that demand for maximum crop ET, may be advisable to apply deficit irrigation strategies. Using these strategies can increase the irrigated area in a given volume of water, which will also improve the efficiency of irrigation water for the production of oil. The high efficiency achieved by this crop irrigation water use ensures a great economic and social benefits for each cubic meter of water used in olive.

These long-term tests have shown that water requirements of 750 m3/ha in traditional olive and 1250 m3/ha in intensive olive can be effective from the point of view of production, having achieved thanks to good management, high efficiency use of irrigation water. However, we believe that dose, should not be recommended citing this statement on the results obtained in other treatments where we have used a higher dose of water as very deficient involve a significant reduction in the profitability of Olive farms irrigated. We believe it is essential that this information is complete with a rigorous economic study which evaluated correctly, in each case, revenues and growing costs. The strategy is recommended when ensuring irrigation in autumn, and only applies in areas with average rainfall exceeding 450 mm and when it have deep soils and adequate moisture holding capacity. In intensive plantations with over 200 olive trees / ha,  a water requirements of 1,500 m3/ha/year is very insufficient in most agronomic conditions of Andalusia.

Under the experimental conditions studied, the largest responses to water requirements in the traditional olive plantations correspond to treatment that irrigated from the ETM and the treatment applied 1500 m3/ha annually in the period from 15 September to 15 April, this treatment deficit is considered the most efficient, as it allows greater water savings per hectare and increased production and additional olive oil per m3 of water applied. In intensive olive plantations, using larger number of trees per hectare, its require more water demand than traditional, finding the best respond to the irrigation treatments correspond to total applied water requirements  from 2500 to 4100 m3/ha, finding the best yield in applying average total of 4100 m3/ha.


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