Murcia, 2014

In agriculture, it is necessary to identify the optimal consumption and the most appropriate application strategy for the development of the plant in order to obtain the most profitable production.
Water is the most determining factor in production and, therefore, the one that most determines economic sustainability. The irrigation system determines efficiency in a decisive way. In gravity irrigation efficiencies do not exceed 60% and in sprinkler irrigation the efficiencies hardly surpass 80%.

In the case of localized irrigation, efficiencies of 95% can be achieved, therefore, adapting drip irrigation to arable crops can be a good strategy to improve productivity. Although the installations of drip irrigation in extensive crops are very similar to the facilities in woody crops, they present some peculiarities that we are going to analyze. Separation of the branches

The separation between branches and the spacing of the drippers within each branch will be determined by the size of the bulb that each dripper develops, and this size will depend on the flow of the dripper, the time of irrigation and the characteristics of the terrain.

To know the size of the bulb it is essential to carry out a field test. The bulb is usually measured at a depth of 30 cm, although it is advisable to measure it at the depth where the root density is maximum, in most plants it is about 60 cm. In underground drip the wet radius is lower than the superficial one (10%), however the wetted volume is much higher. The separation of the branches for these crops can range between 0.5 and 1.75 m. In some soils, one branch must be used for each planting line. If you want to rotate crops it seems advisable to place them 1 m away in clay soils. The separation of the dropper inside the branch can be between 30 and 75 cm, depending on the terrain and the instantaneous flow that you want to contribute. The usual is between 40 and 60 cm.

Droppers

The flow of the dropper should be chosen according to the characteristics of the floor and the hydraulic design. Although the lower flows allow greater length of the branches, making the installation cheaper, it is convenient to choose the most appropriate flow rate for the ground parameters. The drippers can be turbulent or self-compensating. The former have a lower manufacturing variation coefficient and are cheaper per linear meter. The self-compensating drippers maintain the constant flow rates despite the unevenness of the terrain and allow branches with longer lengths (80% more) to the turbulent drippers.

In underground irrigations, the drippers will be self-compensating (with antidrug and antisuction mechanism) because the membranes prevent the entry of dirt when the installation is stopped. In drip irrigation installations, turbulent drippers are recommended because increased pressure can provide higher flow rates, which is highly recommended in the first germination springs.

Depth of the branches In underground irrigation, the depth depends on soil characteristics and crop techniques. It is essential to analyze the conditions of each plot before carrying out any installation. Installations The underground drip irrigation installations are designed with the same criteria as the surface ones. It is convenient that the branches end in a collector comb with automatic or manual purge valves, to avoid the accumulation of particles. In order that there is no recirculation and dirt is not distributed throughout the irrigation grid, it is advisable to install a smaller diameter than the one that feeds the branches.
A suction cup will also be installed in this pipe. It is convenient to install fertilizer injectors with volume control.

Extended and collected branches

With the underground systems we avoid the works of extension and collection of the branches of irrigation and lengthen its useful life. Tillage and sowing techniques that allow working with extended branches are currently being tested.

Conclusions   

– It is not advisable to carry out a drip irrigation installation without knowing the characteristics of the ground in which you are going to install. It is advisable to carry out a test to check the size of the irrigation bulb. The design must be adapted to the ground parameters.

– In areas with sandy-gravel subsoil, buried branches should not be installed.

– In certain soils and climates, with good design and efficient irrigation management, water savings of close to 20% and an increase in production of 15% can be achieved, compared to sprinkler irrigation. Water savings are greater in areas with frequent wind. The pressure requirements are 25% lower.

– Fertigation is essential in these systems. The production improvements will be achieved with adequate fertilization at each stage of crop development. The saving of fertilizer can be important.

– It is convenient, especially in the underground system, a regular control of the moisture content of the soil or the hydric state of the plant.

– The current challenge is to ensure that these techniques are implemented widely in the production culture, for which it is necessary that the irrigator has the information and advice necessary to be able to carry it out successfully.

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