Micro-Irrigation Systems (MIS) apply water through small devices which deliver it onto the soil surface very near to the plant, which means in this context the use of bubbler, mini–sprinkler and trickle irrigation systems.
From 2003 to 2006, 13 feddans of field research were established in sandy soil at Wadi EL Natrown On-Farm Irrigation Department Research Station operated by the Water Management and Irrigation System Research Institute, to evaluate the effect of MIS on olive trees. The experimental site was arranged in a split plots design. On 08-02-2003 olive trees (Olea europaea L, Calamata cv.) were planted in the center of an irrigated round base of 1 m diameter. The distance between the tree rows and the trees within the same row are 5ms. Each plot was divided into six replicates giving 18 experimental plots.
All the micro irrigation systems were designed with the same control head components which consists of non- return valve, flow meter, venturi, air valve, pressure relief valve and 3 pressure gauges. Regarding the distributor units technical specifications and their placement: 1) For the trickle treatment 4 emitters (12 l/h) per each tree placed on one lateral line PE 16 mm diameter passing through the center of the tree round base; where each emitter is 30 cm distant from the next one; 2) For the bubbler treatment one bubbler per each tree (100 l/h) placed in the tree round base , 25 cm distance from the tree stem moving monthly in 180° clockwise to maintain good water distribution; 3) For the mini- sprinkler treatment one mini-sprinkler (70 l/h) per each tree with the same procedure as the bubbler.
A comparison was made between the different systems taking into account the following points: olive trees morphology (plant height, stem diameter, shoots number/tree, leaves number/tree, shadow area and root distribution), number of fruits/tree, fruit weight, yield/tree, total yield per feddan, yield efficiency and both soil moisture content and soil salt distribution. Hydraulics characteristics for each type of MIS were also monitored.
The results obtained show the usefulness of trickle irrigation system in olive trees growing where the trees height increased (cm) by 10 and 9.2%, stem diameter (mm) increased by 6 and 14%, shoots number per tree increased by 8 and 14%, leaves number per tree increased by 13 and 17%, shadow area (cm2) increased by 6 and 13% compared with bubbler and micro irrigation system respectively.
Trickle irrigation systems demonstrate the highest values of sand soil moisture content which is about (18.19, 16.66 and 10.45% by weight) in the soil layers (00–30), (30-60) and (60-90) cm, respectively, whereas the bubbler irrigation systems were (16.66, 14.46 and 9.01% by weight) in the previous soil layers respectively, followed by mini-sprinkler irrigation systems treatment which were about (10.45, 9.01 and 6.58% by weight) in the same soil layers respectively. The olive trees root distribution under trickle irrigation showed more regularity than other types due to root distribution relative to the placement and the number of irrigation distributors.
The net effect of trickle-irrigation was to increase water saving for producing one kilogram of olive fruits with 18 and 35 % less than with bubbler and mini-sprinkler respectively. The number of fruits increased under trickle irrigation by 16 to 24% while the olive tree yield (kg/tree) increased by 18 to 32% compared with bubbler and mini sprinkler irrigation system respectively. Trickle-irrigation can be recommended as an efficient irrigation system for olive trees in the irrigation areas of Wadi El Natrown in the west of the delta region.