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Irrigation


Table grapes 


Modern table grapes' vineyards require more intensive irrigation than wine grapes due to the use of training systems designed to accommodate large leaf area for higher production. The quality requirements for table grapes are different than those of wine grapes since appearance rather flavor and aroma is mostly desired. Contrary to wine grapes, large berry size is a major objective in this case and maintenance of high turgor during the period of berry development is essential. The maximal recommended pan evaporation coefficients in intensive table grapes vineyards is 0.6 - 0.7
The duration of such high irrigation rates vary according to the varieties. It is shorter in early ripening varieties and longer in the late varieties. High crop levels cause increased water loss from the canopy, therefore higher coefficients should be used in years with high crop levels. The harvest time is sometimes determined by the market demands and fruit might be held on the vines for extended periods, beyond their physiological ripening stage.

Irrigation of early varieties after harvest is normally aimed at maintaining the foliage in a good physiological state and thereby enables the formation of reserve sugars for the next season and cane maturation. Excessive irrigation after harvest may stimulate undesired vegetative growth. Such growth does not undergo efficient fruit bud differentiation and incomplete can maturation which may not survive the winter temperatures and weaken the vine.

Fertigation principles

Application of soluble fertilizers through the irrigation water is essential in drip irrigation regimes since the efficient occupation of the limited soil volume under the dripper accelerates the rate of mineral depletion. On the other hand, fertigation provides an efficient means for controlling the concentration of minerals in the immediate vicinity of the active root system. Plant roots can not read measures such as kg per hectare since the uptake of minerals is a function of mineral concentrations. Fertigation requires to look at the mineral concentrations in the irrigation water and in the irrigated soil volume in addition to the common measures of kg per hectare.
The efficient uptake of minerals in drip regimes is due to the maintenance of biological concentrations at high water availabilities, good aeration and formation of concentration gradients. Such mineral concentration gradients expose various parts of the root system to a wide range of concentrations so that part of the root system is always exposed to optimal concentrations and uptake rates. The efficient uptake is reflected in the entire root system due to exchange of water and minerals between individual roots. The fast depletion of minerals is reflected in a rapid response of the vines to the cessation of application of elements such as nitrogen which is known to accelerate vegetative growth.

Rates, time and amounts of applications

For grape vines the optimal concentrations of NPK in the irrigation water are 150, 20 and 150 ppm respectively. These concentrations are used for stimulating vegetative growth when needed while lower concentrations can be used when moderate growth is needed. It is not recommended to apply nitrogen after veraison since it may stimulate vegetative growth which is undesirable at this phonological stage due to assimilate competition between the growing tips and the ripening fruits.On the contrary, phosphorus and potassium may be applied throughout the entire season since they do not interfere with growth and are not as mobile as nitrogen. Microelements can be added according to the needs, the uptake of iron chealates is particularly efficient in drip irrigation regimes.
The selection of the nutrient composition is determined by the needs. Leaf mineral analysis on one hand and soil extractors on the other are very useful tools for this purpose. Petiole rather than blade analysis better reflects the nutritional status of the vines. Petiole sampling is normally done at full bloom, although veraison and pre harvest are suitable dates as well. Recommended levels for petiole and blades for each sampling season are available in the literature.
The advantage of full bloom sampling is the ability to apply the results at the same season. On the other hand, petiole nitrate nitrogen content is quite unstable at bloom time and does not always reflect the need for nitrogen fertilization while pre harvest analysis is more reliable and together with the vigor performance of the same season may serve for the next season's application policy. In early table varieties it is still possible to apply nitrogen at the same season provided the vegetative growth is insufficient as well. Autumn nitrogen application is not recommended in drip irrigation regimes since the rates of water applications in this season are rather low together with the higher leaching risk during the winter rains.
Potassium needs are also better reflected at harvest time since it is the major element in the fruit and its content in the petiole. High petiole potassium is well correlated with high potassium which is known to increase wine pH. In regions where wine pH tends to be high, it is it advisable to restrict the potassium application to the levels required for its physiological functions. However, in table grapes high potassium and high pH mask the sourness perception and may enable to harvest the grapes at lower sugar contents.
Phosphorous increases fruit bud differentiation and sugar accumulation but tends to reduce berry size. These are very important properties for wine grapes but may be useful for table grapes according to the local conditions and the varieties.

The use of soil extractors
Soil extractors are used for monitoring the concentrations of various minerals in the root zone. Extraction can be done only when the soil is saturated and concentrations may be read by the use of field kits. The use of such extractors is important particularly to monitor excessive concentrations which may result from the difference between the rate of application and uptake.

Netafim advanced wine crop solutions
With over 20 years of experience in vineyard irrigation across differing climates and terrains - Netafim has developed a series of custom-designed vineyard irrigation solutions:

Netafim UniWine
The most advanced pressure compensated dripper in the world, specially designed for vineyard use, including pre-installed hanger.
Highly resilient dripper for long-lasting reliability in harsh climates.
Ideal for subsurface application due to a unique anti-siphon mechanism which eliminates vacuum build-up at the end of irrigation and prevents dirt and impurities from entering the system.

Netafim RAM
Netafim's most popular integral pressure-compensated dripper.
Over 20 years of successful field experience.
Pressure-compensation maintains uniform flow rate at different inlet working pressures, ensuring exact distribution of water and fertilizers.
Self-flushing system provides improved resistance to clogging.
Highly-reliable, multi-vintage durability.

Netafim PCJ - Pressure Compensated Junior
Online button dripper specially suited for steep terrain, greater than 25% grade.
Compact pressure compensated dripper with or without anti-drain feature.
Self-flushing system, improves resistance to clogging.
Dripper can be positioned exactly where required and number of drippers can be increased so as to increase water quantity supply to meet specific vine growth rate requirement.
All Netafim pressure-compensated products discharge exactly at the same flow at pressure envelopes of 0.5-3.5 bar.

Product applications
Netafim viticulture irrigation experts work hand-in-hand with growers, designing and planning the optimal irrigation solution based on water availability and key environmental factors such as the following:

  • Soil type and depth
  • Climatic conditions and resultant evapotranspiration levels
  • Soil water holding capacity
  • Preferred planting density and spacing
  • Terrain contours, slopes, directions, etc.
  • Agro-technical conditions such as harvesting machinery, slopes, etc.

Netafim has custom-designed solutions for the three primary vineyard irrigation methods:
On-the-wire
- This is the most common vineyard drip irrigation application based on a dripline (integral or button) suspended 30-50 cm above the ground along the trunk line.
On-the-wire is especially suitable when weed control is accomplished by plowing since no laterals rest on the ground.
Applicable products: UniWine, RAM, PCJ (for slopes greater than 25%).
Surface
- The simplest, most cost-effective and most versatile form of drip irrigation. Surface drip is suitable especially when weed control is chemical under the vine. Driplines are laid on the soil surface under the vine along the trunk line.
Applicable Products: UniWine, RAM
Sub-surface
(SDI) - The most advanced, aesthetic, reliable, precise, and efficient vineyard irrigation drip technique. Sub-surface irrigation is based on integral dripperline buried 25 – 50 cm under the soil.
Drip laterals are laid parallel to the trunk row, 30 – 40 cm from the trunk or in the center of the inter-row. Sub-surface vine irrigation has some notable advantages:
Laterals
are protected from damage: vandalism, weather, and mechanical.
Evaporation water loss is reduced by 10 – 20% over surface drip.
Water is applied precisely to center of the root zone.
Reduced summer weed growth.
Applicable products: UniWine, RAM

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