Vineyard irrigation - Adapting to a changing climate and market requirements
Why irrigate vineyards?
During the past decades significant changes took place in the world wine market, especially to do with its production.
As the "New World" wine production reaches higher levels of quality and production consistency, and the effects of global warming on terroir become increasingly severe – European viniculturists (specialized in growing wine grapes) are re-examining traditional growing methods.
In order to secure long-term investment in terroir branding, to ensure stable and steady vintage quality, and ultimately compete in the mid-to-high-level global wine market – more and more "Old World" growers are turning to modern irrigation methods.
Another market trend has been created as bulk wine producers were looking to move into the lucrative mid-level quality market currently dominated by "New World" producers. Bulk wine producers have found that modern irrigation methods can assist them in consistently producing the quality yield needed to effectively build label brands.
The need for modern irrigation methods in traditional "Old World" growing areas is driven by both climatic and market imperatives. Across Europe progressive viniculturists are turning to advanced irrigation to assist them in continuing to consistently produce fine wine.
Keeping ahead of change
Even in sectors such as wine, where tradition has dominated for centuries, change is inevitable when market and environmental conditions play a predominant role.
For over 2000 years of tradition viticulture has been adapted to changing needs and tastes. The move to advanced irrigation in traditional grape-growing regions reflects a need to compete with consistent yield quality in a global market and to adhere to world climatic changes.
Netafim offers advanced drip irrigation solutions for viticulture. These solutions have been developed for over 20 years together with vineyard owners, growers and researchers represenring a large variery of climates and terrains.
Netafim wine vineyard irrigation solutions have been proven to reduce water expenses, lower unwanted vegetation growth, increase yield quality, and guarantee consistent wine vintages.
Vineyard irrigation approach - Restricted Deficit Irrigation (RDI)
Controlling irrigation application often involves supplying less water than required for optimal vine development. Known as Restricted Deficit Irrigation (RDI), this practice is designed to keep the vine under controlled water stress conditions, to increase wine grape quality. RDI allows grape growers to control the following elements:
- Berry size
- Vegetation and light regime
- Availability of assimilates, photosynthesis
- Turgor, solids concentration
Effective application of a RDI approach is contingent upon stringent and accurate irrigation control, possible only through use of advanced irrigation techniques like drip irrigation.
When opting for a RDI approach grape growers need to take into account numerous factors, including the vine canopy, soil resources, and climatic conditions of both the previous winter and current season. Specifically, environmental conditions such as rainfall (quantity and timing), water retention, and evapotranspiration should be analyzed.
Before rolling out the RDI approach, the following questions need to be addressed:
When to start?
Irrigation usually commences a certain period after the end of the rainy season and a number of factors determine when it is optimal to begin irrigating.
The other questions that Netafim knows to addres are questions such as How to start? How to best irrigate while the canopy is being built and fruit sets? Irrigation frequency? How to most effectively irrigate from the veraison to the end of sugar buildup? How should irrigation be modified after maturity? Irrigation after harvest? How to continue irrigation most effectively after harvest, if rains have not begun?
Frequency of irrigation
Unlike conventional irrigation methods, drip irrigation does not consist of utilizing the soil as a water reservoir since the horizontal water distribution is limited and depends on the hydraulic conductivity properties of the soil. Therefore, this method requires frequent irrigations in order to eliminate water percolation to soil layers bellow the major root zone.
The frequency is determined by three major factors; soil properties, evaportranspiration rate and water emission rate of the irrigation system.
Drip systems are normally designed to supply the water requirement of at least one day during the top season. At the beginning and at the end of the season, when the water requirements are low (due to low evaporative demands and low canopy surface irrigation), frequencies may vary between one and two per week. During the major season, frequencies may increase to daily or every other day. Sandy soils require more frequent irrigations than heavy soils. Accumulation of large deficits may require extended duration of irrigation hours and may result in water percolation or run off.
Tensiometers or other soil moisture sensors located at about 40 cm horizontal and vertical distance from the drippers may serve as useful tools for adjusting the rate of irrigation besides the use of meteorological data. Constant soil water readings indicate proper irrigation. Increasing or decreasing weekly readings indicate excessive or deficient irrigation respectively. In case of need for water stress applications during various stages of development along the season, reducing the amount of water per application is preferred rather than increasing the intervals. This way provides better control of the stress severity. Irrigation control by soil sensors can also be automated by the use of an irrigation computer which is capable of averaging the readings of few sensors and turn on and off the irrigation system at pre-determined threshold values.
In addition to soil water sensors for the determination of the threshold for irrigation, it is advisable to place a sensor at a depth of 1.2 m in order to monitor possible percolation. Water percolation to layers bellow the main rootzone is undesirable. It can cause miscalculations of the amounts of water and minerals supplied by fertigation, intended for consumption by the vines. Percolation of minerals, nitrogen in particular, may contaminate the ground water and cause environmental damage.
Table grapes irrigation
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 winegrapes, 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.
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 hectar.
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 phenological 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 inerfere 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 preharvest 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 rootzone. 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:
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'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.
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