A. Crop Water Use
Grapevine water use is estimated and monitored using a combination of direct and indirect methods that provide insights into the water needs of the vines and help growers optimise irrigation management.
Direct measurement methods:
Sap flow sensors measure the rate at which water moves through the xylem vessels of grapevine stems, providing real-time data on vine water uptake. By placing sensors on multiple vines across different blocks or varieties, growers can assess variations in water use and adjust irrigation accordingly.
Sap flow sensors measure the movement of water through xylem tissue
A sap flow sensor attached to a grapevine
Stem water potential measurements, typically taken using pressure chamber or pressure bomb techniques, indicate the water status of grapevines by assessing the tension or pressure within the plant’s vascular system. Monitoring stem water potential helps growers evaluate vine water stress levels and make informed decisions about irrigation scheduling.
A vacuum chamber is used to measure stem water potential
Indirect measurement methods:
Weather-based models: Weather-based models estimate grapevine water use (evapotranspiration, ETc) by integrating weather data such as temperature, humidity, solar radiation, and wind speed. These models, such as the Penman-Monteith equation or the FAO-56 methodology, provide daily or hourly estimates of crop water demand, allowing growers to adjust irrigation schedules based on environmental conditions.
Soil moisture sensors: Soil moisture sensors or probes measure the moisture content of the soil at various depths within the root zone of grapevines. By monitoring soil moisture levels over time, growers can assess irrigation needs and prevent both overwatering and underwatering. Soil moisture sensors can be integrated into irrigation management systems to automate irrigation scheduling based on real-time data.
Various types of soil moisture sensors are available to growers
Remote sensing technologies:
Satellite-based remote sensing platforms capture multispectral imagery of vineyards, allowing growers to monitor vegetation health, water stress, and canopy vigour over large areas. By analysing satellite data, growers can identify regions of the vineyard experiencing water stress and prioritise irrigation interventions accordingly.
Aerial drones equipped with multispectral or thermal cameras can provide high-resolution imagery of vineyards, enabling growers to assess crop health and water status at a finer spatial scale. Drone imagery can be used to detect early signs of water stress, monitor irrigation uniformity, and identify areas of vineyard stress or disease.
Remote sensing data can indicate exposed soil or poor plant growth, which will guide better irrigation in certain spots in the vineyard
Vineyard observations and field monitoring:
Growers regularly inspect grapevines for visual signs of water stress, such as wilting leaves, reduced canopy growth, or changes in leaf colour. Field observations complement quantitative data from sensors and models, providing qualitative insights into vine health and water status.
Vineyard managers may also conduct in-field measurements of soil moisture, canopy temperature, or leaf water potential using handheld instruments to supplement remote sensing and modelling approaches.
By integrating these estimation and monitoring methods, grape growers can gain a comprehensive understanding of grapevine water use dynamics, optimise irrigation management practices, and promote sustainable water use in vineyard operations.
B. Pressure and Flow Rate
Pressure and flow rate are critical parameters in irrigation systems, and checking and optimising them are essential for ensuring efficient water delivery to crops.
Checking pressure:
Pressure in an irrigation system is measured using pressure gauges installed at various points along the pipeline. To check pressure, growers can use pressure gauges to monitor the water pressure at key locations, such as at the pump, at the beginning and end of mainlines, and at individual emitters or drip lines.
Optimal pressure levels vary depending on the type of irrigation system and the specific requirements of the crop being irrigated. For example, drip irrigation systems typically operate at lower pressures (such as 10 to 30 psi) to ensure proper emitter performance and prevent emitter clogging, while overhead sprinkler systems may require higher pressures to achieve adequate coverage. If pressure levels deviate from the recommended range, adjustments may be necessary, such as regulating the pump speed, adjusting valve settings, or installing pressure regulators or control valves to maintain consistent pressure throughout the system.
Optimising pressure:
Optimising pressure involves adjusting the irrigation system to ensure that pressure levels are within the desired range for efficient water delivery and uniform distribution. Pressure regulators can be installed at key points in the system to maintain consistent pressure levels, reducing the risk of emitter clogging, water waste, and uneven irrigation.
Proper system design, including correctly sizing pipes, valves, and fittings, helps minimise pressure losses and maintain adequate pressure throughout the system. Regular maintenance of pumps, filters, valves, and other components is essential for ensuring optimal system performance and pressure regulation. Monitoring pressure trends over time and adjusting system settings as needed can help growers identify and address issues related to pressure fluctuations, leaks, or blockages.
Checking flow rate:
Flow rate, or the volume of water passing through the irrigation system per unit of time, is measured using flow meters installed at strategic points in the pipeline. Flow meters can be installed at the pump outlet, at the beginning and end of mainlines, and at individual zones or sectors within the irrigation system. By monitoring flow rates, growers can assess the overall performance of the irrigation system, identify leaks or blockages, and ensure that water is distributed evenly across the field.
Optimising flow rate:
Optimising flow rate involves adjusting the irrigation system to achieve the desired flow rates for efficient water delivery and uniform coverage. Proper system design, including correctly sizing pipes, pumps, and emitters, helps ensure adequate flow rates while minimising energy consumption and water waste. Regular maintenance of filters, valves, and other components is essential for preventing clogs and restrictions that can impede flow and reduce system efficiency.
Adjusting pump speed, valve settings, and irrigation schedules based on crop water requirements and soil moisture levels can help optimise flow rates and water use efficiency. Implementing technologies such as variable frequency drives (VFDs), which allow for precise control of pump speed and flow rate, can help optimise energy use and system performance.
By checking and optimising pressure and flow rate in irrigation systems, growers can ensure efficient water delivery, minimise water waste, and promote healthy crop growth while maximising water use efficiency and minimising operational costs.
C. Detecting Water Loss
A water loss detection programme involves several key steps to identify and mitigate water losses within an irrigation system. Firstly, visual inspections are conducted to examine the entire irrigation infrastructure, including pipes, valves, fittings, and emitters, to detect visible signs of leaks, damage, or wear. Additionally, monitoring devices such as water meters and pressure gauges are utilised to collect data on water flow rates, usage patterns, and system performance. This data is then analysed to identify anomalies or irregularities that may indicate leaks or inefficiencies.
A leaking pipe can cause unnecessary water loss and can disrupt the pressure of the entire irrigation system
Specialised leak detection equipment, such as acoustic sensors or thermal imaging cameras, may be employed to pinpoint the location of leaks within the system, and tests such as pressure tests or dye tests may be conducted to confirm the presence and severity of leaks. Once leaks or other sources of water loss are identified, corrective actions should be to repair leaks, replace damaged components, or address inefficiencies. Preventive maintenance measures, such as cleaning filters and inspecting seals, may also be implemented to prevent future leaks and ensure proper system operation. Continuous monitoring and analysis of system performance are essential for identifying new leaks or inefficiencies and making further improvements to the irrigation system over time. Through these efforts, water loss detection programmes help growers conserve water resources, improve irrigation system efficiency, and reduce operational costs.
Fertigation
A. Seasonal Fertigation Programmes
Seasonal fertigation programmes are adjusted throughout the grape growing season to meet the changing nutrient requirements of the vines and ensure optimal yield and quality.
Early season (bud break to pre-bloom):
During the early stages of the growing season, fertigation focuses on supplying essential nutrients to support vegetative growth and development. Nitrogen (N), phosphorus (P), and potassium (K) are applied to promote root development, canopy growth, and early fruit set.
Micronutrients such as boron, zinc, and manganese may also be included to address specific nutrient deficiencies and support overall vine health. Fertigation rates and frequencies are typically higher during this period to meet the increased nutrient demands of rapidly growing vines.
Mid-season (bloom to véraison):
As the vines transition from vegetative growth to flowering and fruit development, fertigation strategies shift to support reproductive growth and fruit set. Fertiliser formulations should be adjusted to include higher levels of potassium and calcium to enhance fruit quality, improve berry size, and reduce susceptibility to diseases such as botrytis.
Nitrogen applications can be reduced to prevent excessive vegetative growth and promote balanced vine development. Foliar nutrient applications may complement fertigation during this period to provide targeted nutrient delivery and address specific deficiencies.
Late season (véraison to harvest):
In the weeks leading up to harvest, fertigation programmes focus on optimising fruit ripening, flavour development, and sugar accumulation while maintaining vine health and vigour. Potassium applications are particularly important during this stage to promote sugar accumulation, improve berry flavour, and reduce the risk of potassium deficiency disorders such as uneven ripening or shrivelling.
Nitrogen applications should be reduced or discontinued to minimise excessive vegetative growth and enhance fruit quality. Adjustments to fertigation timing and rates may be made based on grapevine canopy and soil moisture status to avoid water stress and ensure optimal nutrient uptake by the vines.
Post-harvest and dormancy:
After harvest, fertigation programmes may include applications of nitrogen and potassium to replenish soil nutrient levels and prepare the vines for dormancy. Foliar nutrient applications or soil amendments may be used to address any nutrient deficiencies identified during post-harvest soil testing.
Fertigation rates may be reduced or suspended during dormancy to minimise nutrient leaching and conserve water resources until the start of the next growing season. Throughout the grape growing season, fertigation programmes are adjusted to the specific nutrient requirements of the vines at each stage of development, considering factors such as soil conditions, weather patterns, and grapevine physiology. Regular monitoring of soil and tissue nutrient levels, along with careful observation of vine growth and fruit development, guides adjustments to fertigation practices to optimise grape yield and quality.
B. Monitoring Water Quality
Monitoring water quality for fertigation involves a comprehensive assessment of various physical, chemical, and biological parameters to ensure that the irrigation water meets the needs of the crops and does not pose any risks to plant health or soil fertility. One key aspect of water quality assessment is the measurement of pH levels, which indicates the acidity or alkalinity of the water. pH levels outside the optimal range (typically between 6.0 and 7.5) can affect nutrient availability and soil pH, leading to deficiencies or toxicities in plants. Regular monitoring of pH levels allows growers to adjust water acidity or alkalinity as needed through pH adjustment techniques such as acidification or liming.
Litmus paper can be used to conduct quick, on-site water pH tests
Electrical conductivity (EC) and total dissolved solids (TDS) are also important indicators of water quality for fertigation. EC measures the ability of water to conduct electricity, which is influenced by the concentration of dissolved salts, minerals, and nutrients. High EC levels can indicate elevated salt content, which may lead to soil salinity issues and affect plant growth. TDS measurements provide a quantitative assessment of the total amount of dissolved solids in the water, including salts, minerals, and organic matter. Monitoring EC and TDS helps growers assess water salinity levels and make informed decisions about water management practices, such as adjusting fertigation rates or using alternative water sources.
Furthermore, nutrient concentrations in irrigation water are evaluated to determine the natural nutrient content and potential fertilisation requirements. Essential nutrients such as nitrogen (N), phosphorus (P), potassium (K), and micronutrients play crucial roles in plant growth and development. Analysing nutrient levels in irrigation water allows growers to adjust fertigation programmes, accordingly, supplementing any deficiencies with additional fertilisers or adjusting application rates to avoid nutrient imbalances. Additionally, water quality testing may include assessments for potential contaminants such as heavy metals, pesticides, pathogens, and organic pollutants, which can adversely affect plant health and human safety. By monitoring water quality parameters regularly and taking appropriate corrective actions, growers can optimise fertigation practices, ensure healthy crop growth, and promote sustainable agricultural production.
C. Adjusting Fertigation to Water Quality
When water quality changes, fertigation programmes should be adjusted to maintain optimal nutrient delivery to crops and minimise potential adverse effects on plant health and soil fertility. One common adjustment involves modifying fertiliser formulations and application rates to compensate for variations in nutrient concentrations and ratios in the irrigation water. For example, if the water source has low levels of essential nutrients such as nitrogen (N), phosphorus (P), or potassium (K), growers may need to supplement these nutrients with additional fertilisers to meet the crop’s requirements. Conversely, if the irrigation water contains high levels of certain nutrients, adjustments may be made to the programme to reduce fertiliser inputs or select fertilisers with lower nutrient content to prevent nutrient imbalances and minimise the risk of over-fertilisation. By analysing water quality data and adjusting fertigation programmes accordingly, growers can ensure that crops receive the appropriate nutrients in the right proportions to support healthy growth and development.
In addition to nutrient adjustments, changes in water quality may necessitate modifications to irrigation management practices to mitigate potential negative impacts on plant health and soil fertility. For example, if the irrigation water has high levels of salts or minerals, growers may need to implement strategies to leach excess salts from the root zone or select salt-tolerant varieties to minimise salt stress. Similarly, if the water source contains contaminants such as heavy metals, pesticides, or pathogens, growers may need to implement additional water treatment measures or consider alternative water sources to avoid potential risks to plant health and food safety. Regular monitoring of water quality parameters and proactive adjustments to fertigation programmes and irrigation practices are essential for optimising crop production and ensuring the long-term sustainability of agricultural systems.
D. Pipeline Sanitation Programmes
Sanitation programmes for drip irrigation pipelines are essential for maintaining the cleanliness and functionality of the system, preventing clogs, biofilm formation, and the spread of pathogens. These programmes typically involve regular cleaning and disinfection procedures to remove organic and inorganic deposits, algae, bacteria, and other contaminants that can accumulate within the pipelines. One common sanitation practice is the use of chemical cleaners and disinfectants to flush the system and eliminate biofilm and microbial growth. Phosphoric acid, hydrogen peroxide, or peracetic acid solutions are commonly used for this purpose, applied either as a periodic shock treatment or continuously injected into the irrigation water to maintain sanitation levels. Chlorine dangerous for plants
Physical cleaning methods such as flushing, backwashing, and scrubbing are also employed to remove debris and sediment from the pipelines. Flushing involves running pressurised water through the system to dislodge and flush out accumulated solids and organic matter. Backwashing reverses the flow of water through the emitters or filters to dislodge and remove trapped particles. Additionally, mechanical scrubbing devices or brushes can be used to physically agitate and remove biofilm and deposits from the inner surfaces of the pipelines. Regular maintenance and inspection of filters, valves, and other components are essential for ensuring proper system operation and preventing clogs and blockages.
Moreover, implementing preventive measures to minimise contamination and maintain water quality is integral to sanitation programmes for drip irrigation pipelines. These measures may include using filtered or treated water sources, installing screen or disc filters to remove particulate matter, and implementing irrigation scheduling practices that minimise prolonged periods of water stagnation. Periodic monitoring of water quality parameters, including pH, electrical conductivity (EC), and microbial counts, can help growers assess sanitation levels and identify potential issues before they escalate. By implementing comprehensive sanitation programmes and preventive measures, growers can ensure the cleanliness and integrity of drip irrigation pipelines, optimise system performance, and promote healthy crop growth while minimising the risk of contamination and disease spread.
E. Fertigation Safety
Mixing:
The mixing of agrochemicals involves combining different substances to create a solution or mixture suitable for application. The relevant apparatus for this process includes a calibrated measuring container, such as a graduated cylinder or measuring jug, to ensure accurate measurement of the agrochemicals. Additionally, a clean and dedicated mixing tank or vessel is essential for blending the chemicals thoroughly. A mixing stick or paddle is often used to agitate the solution, ensuring even distribution of the components. Personal protective equipment (PPE), including gloves and goggles, is crucial during the mixing process to prevent direct contact with the chemicals. It is important to follow the manufacturer’s guidelines regarding the order of adding chemicals, mixing durations, and any specific instructions to maintain the efficacy and safety of the agrochemical mixture.
Agrochemicals should be used and prepared according to the instructions provided on the label(s). Any other use of agrochemicals is a criminal offence, and this needs to be communicated to the workers clearly. Only the quantity of spray mixture required for one specific application should be prepared. When containers with concentrated formulations are transported to filling points away from the agrochemical store, it is important to lock them securely in a metal or galvanised mesh trunk. This trunk must be chained securely to the tractor and the filling point during spray operations.
Filling:
A dedicated filling station should be available, which allows spacious manoeuvring of tractors and implements, storage tanks, and the filling of trailers. Filling may occur with the help of pipes in the case of liquids, or large funnels in the case of solids. Safety considerations include the following: It is essential to keep the area where spray equipment is mixed and filled away from any water sources. The filling area’s floor must be non-porous, for instance, concrete with damp coursing, and must have a retaining wall to prevent spillover. Rinse liquid from measuring vessels should be poured into the spray tank. It is crucial to ensure that soil and water sources are not contaminated by spillage or runoff. An evaporation pit that is non-permeable and either filled with stones or covered with a metal grid should be built to channel contaminated runoff water.
Adding a handful of lime increases the pH, and ultra-violet radiation from the sun, combined with the high pH, breaks down active ingredients, and water evaporates. The pit should be covered when it rains to prevent rainwater from filling up the pit. Alternatively, a tank for contaminated water can be installed and emptied by a professional hazardous waste disposal company. According to the Department of Water Affairs and Forestry, it is unacceptable to use soak-aways and French drains for disposing of pesticide-contaminated runoff water.
Fertigation relies on adding fertilisers into the irrigation system. This is done in specialised tanks and equipment