Wewillsee in this article whichparameterswe have to determinebeforeplantingourblueberries as well as the irrigation needs of blueberries.
Whenwe are gettingready to plant, we have to bear in mind the factthatblueberries have theirownspecificdemands. In order to besuccessful in the crop’s production, itis essential to make a verypreciseassessment and examination of the soil, availablemoisture content and climate:
• Soil inspection.
• Testing the water.
• Number of cold spellsduring the year.
• Orientation of the land.
• Risk of frost; especiallyduringflowering stage (April-May).
It isalso important to know the number of smallberry plantations locatednearyourfarm, the varietiesused, and, if possible, their marketing network.
• Soil inspection
• Selecting the correct varieties
• Installing an irrigation system
Soiltesting. Blueberriesprefer light, acidic and permeablesoils, which are rich in nutrients and humus. If the pH shouldbehigherthan the recommended value, thenwe have two options to reduce the pH by 1 point.
The first option wouldbe to addsulphur to the soil. Sulphuris one of the mostcommonelementsusedsoitisadvisable to applythisamendment 3 or 4 monthsbeforeplanting. The recommended dosage isbetween 800-1,200 kg of sulphur per hectare, depending on the soil structure. If weshould have to repeatthisoperation to achieve the correct pH for the blueberries, thenthereshouldbe a 6-month intervalbetween applications.
Furthermore, sulphur can improve the characteristics of the orchard as the plant develops and the fruits harden. However, on the other hand, sulphurincreases the conductivity of the soilswhenthisis high. The second option is to addacidifyingorganicmatter, such as pine bark or sawdust. Apart fromreducing the pH of the soil, theseelements are beneficial for the soil and help it to retain the organicmatter.
Water testin. As well as inspecting the soil, the water must betestedbefore setting up our plantation. We must keep an eye on the following concentrations:
• iron, manganese, sodium, calcium, sulphur. The iron content must belessthan 0.2 mg/l in the irrigation water, as recommended by the (FAO). Iron can cause oxidation and, therefore, lead to the development of ironbacteria (IronOchre), leading to the clogging of the filters and irrigation lines if the value shouldbehigherthan the abovementioned 0.2 mg/l.
Large quantities of calcium in the water can increase the pH in the soil and alter the pH of the peatprepared for the plantation. The main issue here for the producersiswhether to reduce the % content of theseelements to an acceptable value or whether to removethemcompletely? There are two possible options for resolvingthis issue, whichdepend on the producers and theiravailable CAPEX and OPEX.
1. Installing a pond or reservoirthatisoxygenated. Oxygenwouldprecipitate the iron in the water, allowing the Pyrolusite to functionproperly. I considerthatitis important to mention thatthisdissolvediron must oxidizeinto Fe3+ (non soluble) and becompletelyremoved by filtration.
2. The method for completelyremovingtheseelements, such as calcium, boron, sodium, chloride etc. is via physical/mechanical filtration with RO. Weprovide an Watertech OSM Station thatoffers a complete solution with 3 mechanical technologies + chemicaloxidation.
1) Oxidation (NaClO)
2) Pyrolusite (removing the Iron and Manganese)
3) Microfiltration (1 micron)
4) Reverse Osmosis.
These solutions mayappear to beexpensive at first, but many countries, such as Mexico, Chile and Peru. areimplementingthis solution in their plantations, increasingtheir production and profits, and gettingtheir return on thisinvestment by the second year.
Orientation of the land. Highbushblueberriesneed sunlight, just like anyothercrop, and a perfect orientation for growth and ripening, but thiswilldepend on the zone and the climaticparameters of this zone.
The common orientation in the Northernhemisphereisfrom North to South. For thisreason, wewill select the mostsuitablevariety for ourclimate and market (see table in article 1 for more information).
Setting-up the site. It is not necessary to installany protection during the planting stage; but once the plants start producing, itishighlyadvisable to shield the cropsfromwildanimals, using a cover or a scarecrow, to preventbirdsfromgettinginto the plantation area duringripening.
Blueberriesshouldbeplanted in mounds or raisedbeds of 15- 20 cm in height and 40-60 cm in widthwith a separationbetween the plants of 1.5 x 2.5 m. In the case of hydroponic plantations, the distance willbe shorter, increasing the density per hectare to 9,000 plants per hectare, i.e. almost 2 adult plants per square meter.
Planting. Blueberriesshouldbeplanted in the spring or autumn. Whenplanting in spring, irrigation helps the young plants to settle in the ground. Whenplanting in autumn, the plants must beprepared for the winter. A hole of 50 cm deep by 80 cm wide must bedug for eachyoungblueberry plant. Don’t forget to apply to the planting area a mixture of sawdust and acidicpeat, whichwill help the roots to developquicker.
BLUEBERRIES: IRRIGATION REQUIREMENTS
In this section, wewill cover the nextstep of the blueberry production project. I willexplainthree irrigation methods, for cropsplanted in the soil, soillessgrowing and SDI irrigation, and describe how to choosebetween one method or the other.
Blueberries have a tiny and superficial root system; the primaryrootsbeingresponsible for anchoring the plant to the ground and transportingnutrients to the part of the plant aboveground. The secondaryroots are slightlythickerthanhumanhair, theirfunctionbeing to enable the tertiaryroots to develop and create a linkbetween the tertiary and primaryroots. The tertiaryroots, with a short useful life, withdraw water and nutrientsfrom the ground. The roots are most dense in the first 30 cm of soil. Theymayextend down as far as 60-70 cm, but theywillbeless dense at thisdepth.
In previous articles, we have alreadyexplainedthatblueberries are extremely sensitive to water stress and theyneed the correct amount of water during the flowering, fruit set and ripening stages. Therefore, the implementation of an irrigation system in blueberrycropsisalmostobligatory in order to obtain a satisfactorylevel of production during the 30-year life expectancy of thiscrop.
There are four points to considerbefore setting up an irrigation system
1. Water availability. This willalwayspredetermine the surface area and location of the plantation.
2. The soil type indicateswhether the soil texture and pH issuitable for blueberries (seemyprevious article for more about soil conditions).
3. Topography. In areas with a large topographical variation itisadvisable to use pressure compensatedemitters (CNL).
4. Energy. We can use the rule of single-phase system for lessthan 3 ha and three-phase for more than 3 ha.
The irrigation design depends on:
• the ET0 (referenceevapotranspiration). This value, whichdepends on the climate, isestimated for a 10cm-tall well-watered area of grass.
• Kc (Crop Coefficient) phenological stages.
• Fc (FractionalVegetationCoverage), whichis the shaded of the cropcanopy.
ETc = ET0 x Kc x Fc
To give us an idea of the averageevapotranspiration values, it can be 4.5l/h in Mexico, while in Huelva (Spain) itis 4 l/h. Weshouldalsoconsiderthat the maximum duration of each application (pulse) shouldbebetween 2-5 minutes.
The irrigation emitterplays a key role in soilless irrigation. It must be pressure-compensated and anti-drainage (CNL) becausethis irrigation methodrequires a constant flow for all of the plants of the sectorsimultaneously. If the pipeline becomesemptyevery time it stops, thenitwillbe impossible to obtainuniformity over all the sectors. Only PC CNL drippers can offerthesequalities.
Selecting the Irrigation Method. Wealready know that irrigation is essential, sowenow have to select the mostsuitablemethod for our production. Sprinkles are used for blueberry plantations, but I amgoing to focus on a much more effective system: high frequencylocalized irrigation (irrigation of soil-grown or soillesscrops). I amgoing to considerthatour goal is to achieve maximum efficiencywith the consumption of less water and fertilizers.
Soilless Irrigation. Growing blueberrieswith the soillessmethod has becomeverypopular over the last 10 years, mostly in countries and regionswhereblueberries are not native (Peru, Mexico, Morocco, and the south of Spain).
Some of the advantages of irrigating a soillesscrop are as follows:
• Viable production whensoil conditions are not suitable for growingblueberries.
• More rapid production times.
• Better control of the pH, root aeration and the plant health aspect.
Soillessblueberriesshouldbeplantedin 27- to 40- litre pots. The substrateshould have a mixture of peat, coco peat and perlite. The structure shouldbeporouswith a slightlyacidic pH.
Organic or conventional fertilization?
Many of the fertilizersused on the market are used in a solidform (powder or granules), especiallyorganicfertilizers. Thesefertilizers have verylowsolubility in irrigation water; therefore, weshouldprovide the fertilizer tank with an agitatorratherthanusingoxygen injection, whichmayprecipitate certain elements, such as iron.
Ideally, whenusingorganic fertilisation, the injection equipmentshould have a Venturi device, whichis as large as possible. To filter out the many and frequent TSS particles, we must have several filtration points, includingfilters at the outlets of the tanks or reservoirs, at the head end and in the hydrants of eachsector.
• Filter size: 130 microns.
• Emitters: CNL emitters are the mostsuitable for irrigatingsoillesssystems, with a labyrinth large enough to preventanyclogging and a fast flow rate of 2-4 l/h.
• Plant layout: between 0.5 x 2.5 m (9,000 plants/ha) – 0.5 x 2.5mt (10,000 pl/ha).
Irrigating soil-grown plants
Surface Drip Irrigation. As with the soilless system, aboveground irrigation uses the sametechnicalfeatures for meeting the water requirements of the blueberries as well as the use of fertilizers and filtration equipment.
The main differenceisthatthere are twodriplines, one on eachside of the plant row, with a PC-AS emitterdelivering 1.6 to 2.3 l/h with a spacing of 33 cm, as commonlyused in Huelva (Spain). The irrigation run time willvaryaccording to the periods of peak water demandduring the day
Subsurface Drip Irrigation. In the case of SDI, itisvery important to know the exact amount of water and fertilizersrequired by the plant, since the water won’tbe visible. The use of soilmoisturesensorsisstronglyadvised, as well as checking verycarefully the water meterspositioned in the hydrants or main linesleadingfrom the pumping station.
The depth of the irrigation linesshouldbebetween 20-30 cm. The spacingbetweenemittersshouldbe 50 to 75 cm, depending on the soil texture and the depthselected. It isadvisable to installtwo irrigation PC-AS driplines per plant bedwith a total flow rate of 4 l/h. It isvery important to have a large, self-cleaninglabyrinth to avoidanyclogging.
The distance between the driplines and the plants willdepend on how large wewantour plants to bein 10 years (the furtherthey are from the plant, the wideritwillgrow). If ouraimis, for example, to have a plant thatis 1m. in diameter, thenwe must bury the driplines 50 cm from the plants.
Anotherinteresting question wouldbewhetherwe are going to plant on mounds or raisedbeds. If thisshouldbe the case, then the width of the mound mayprevent the installation of SDI systems. If mounds or beds are not used and the cropisplanteddirectly onto the ground, SDI mightbe a viable choice.
As mentioned in this article, in order to maximizeincome, weneed to look verycarefully at the climate, soil and water so as to select the mostsuitablevariety and takeintoaccount the fertigation.
Beforedeciding on the irrigation methodfrom the threedescribed in this article, we must carry out a properanalysis of the soil and water beforecalculating the dimensions. These analyses will help to determine the best method to suit our conditions.