Precision Viticulture Applications
Canopy and Vigor Monitoring
Canopy and vigor monitoring is the area of greatest adoption by the growers and the wineries for several reasons. It is possible to get timely, high-resolution information during the growing period, which may be relevant for canopy management, fertilization, and irrigation.
Crop Load Management
Crop load management in vineyards is important for the consistent production of both quality fruit and mature wood. “Crop load” is the ratio of exposed leaf area to fresh fruit weight. Too much leaf area promotes shading and reduces fruit quality—and sometimes bud fruitfulness. Too little leaf area per unit of fruit delays ripening and reduces vine size. Measures of crop load are useful to growers in evaluating success of vineyard management practices. The Ravaz index—which uses the ratio of yield to pruning weight to estimate crop load—is one common metric.
Berry Quality Sampling
The NDVI image is an excellent tool to design quality, sampling zones based upon the NDVI classifications.
While an idealized goal of management is to provide uniform vineyard blocks, the reality is it takes time, and some blocks will just never be uniform.
Disease from insects, pathogens, and other infectious organisms can become a serious problem. In some cases, disease development on grapevines occur rapidly and results in entire vineyards incurring injury to various degrees. For example, grapevines are susceptible to powdery mildew infection early in the growing season.
Manually monitoring environmental parameters (e.g., humidity, temperature, soil moisture, etc.) in the vineyard is not only time consuming but difficult to respond to in a timely manner when conditions change rapidly over space and time. Wireless sensor networks (WSNs), have been found to be suitable for collecting real time data for different parameters pertaining to weather, crop, and soil in developing solutions for viticultural processes related to growing grapes. The development of wireless sensor applications in viticulture has made it possible to increase efficiency, productivity, and profitability of vineyard operations.
Deployment of Wireless Sensor Networks
WSN deployed in vineyards is used for monitoring site conditions such as temperature, wind speed, wind direction, rainfall, solar-radiation, relative humidity, soil-moisture, soil-temperature, sap flow, and leaf wetness, for management decision making purposes. For example, WSN is used in the following applications:
Wireless sensor networks consist of distributed, wirelessly enabled embedded devices capable of employing a variety of electronic sensors. The system architecture consisting of three layers namely, node, server, and application layers.
Node Layer: This layer consists of all the wireless sensor nodes and a base station. Each node, also known as a mote, in a wireless sensor network is equipped with one or more sensors in addition to a microcontroller, wireless transceiver, and energy source. The microcontroller reads the sensor data and, after processing and formatting, outputs the data to the onboard wireless transceiver to form an efficient system for relaying small amounts of important data with minimal power consumption.
Server Layer: Data are sent to the data server from the base station through the internet. Two main tasks performed by data server are to:
Application Layer: This layer allows users of the system to have remote access to WSN data using web browsers. This provides a powerful tool to visualize real-time WSN data such as temperature and soil data from each vineyard.
With water becoming a more scarce and managed commodity, better management is required. Most vineyard blocks do not have the same water requirements due to differences in soil type and topography within the same vineyard. Irrigation systems have been developed that can apply the correct amount of water where it is needed.
Normalized Difference Vegetation Index (NDVI)
By measuring the health and vigor of vegetation, NDVI can help vineyard managers fine-tune irrigation patterns. NDVI is directly related to the amount of photosynthetically active radiation that a plant may absorb.
Common tools for measuring water movement in vines are pressure chambers and leaf porometers. The chambers, often called pressure bombs, require a leaf with stem to be cut from the vine and put into a sealed container with a seal around the stem, and the gas pressure applied to push sap is used to calculate vine water usage.
In recent years, application of centimeter accuracy RTK-GPS has received a lot of attention because of its ability to provide extremely precise location information.
Personal digital assistants (PDAs) and other handheld computers utilizing the global positioning system (GPS) allow the grower to scout vineyards and upload geo-referenced data such as soil moisture, plant nutrient stresses, and pest thresholds.
Soil electrical conductivity (EC) has been widely used to interpret soil spatial variability. Initially used to assess soil salinity, the use of EC in soil studies has expanded to include: mapping soil types; characterizing soil water content and flow patterns; assessing variations in soil texture, compaction, organic matter content, and pH; and determining the depth to subsurface horizons, stratigraphic layers or bedrock, among other uses. Variation of conductivity across soil types is the one of the main advantages of using this technology.
Non-contact Sensor Measurements
Non-contact EC sensors work on the principle of electromagnetic induction (EMI). EMI does not contact the soil surface directly. The instrument is composed of a transmitter and a receiver coil, usually installed at opposite ends of the unit. A sensor in the device measures the resulting electromagnetic field that the current induces. The strength of this secondary electromagnetic field is proportional to the soil EC. These devices, which directly measure the voltage drop between a source and a sensor electrode, must be mounted on a non-metallic cart to prevent interference (See Figure 33.8).
Contact Sensor Measurements
This type of sensor uses coulters as electrodes to make contact with the soil and to measure the electrical conductivity.
Typical vineyards may be infested by up to 20 weed species, of which three or four are dominant in terms of number of plants and land area covered. The distribution of weed species across a vineyard is “patchy” in nature. Some areas will be densely populated by weed while others will have few or no weeds. Densely populated patches often occur along vineyard edges, but may be found anywhere in the vineyard where the environment and management have favored the establishment and survival of weeds. The composition of weed species varies across a vineyard, and different patches may be dominated by different species. In addition to weed density varying spatially in a vineyard, it also may vary temporally and can be strongly influenced by weather.
Yield monitoring refers to the “on-the-go” collection of both yield and positional data by the yield monitor and DGPS as the harvester travels along. The output in the form of yield maps allows growers and wine producers the ability to identify areas of different crop yield, and in some cases different fruit quality attributes, within individual vineyard blocks. Yield maps do not require ground truthing since they represent actual as opposed to surrogate measures. Ground truthing is the process of gathering data in the vineyard that either complements or disputes remote sensing data collected by aerial photography or satellite.
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