by Courtney Llewellyn
Do you want to save inputs while seeing better yields? Variable rate fertilization – among other practices for precision management – may be the answer. They’ve seen proof of this in vineyards and they discussed it at the 2021 Unified Wine & Grape Symposium.
Mesa Vineyard Management in California is both organic and biodynamic, according to Bob Thomas, vineyard manager at Castoro. They analyzed soil samples and found they needed additional compost on their weaker soils. They used Ag Leader technology to look at specific activity in specific zones and the amount of compost they wanted to spread in each zone. Calibrating their spreader was the most important step, and they utilized a flow control valve to apply specifically what was needed. That is the essence of precision management.
It’s ultimately about analytics driving management and optimization. The three Ms are in play: measure, model and manage. To measure, you want to collect integrated, geospatial measures for real-time monitoring of plant growth and canopy health, plant, soil, water and nutrient status and pests and diseases. Modeling uses plant responses to key parameters by determining geospatial relationships among key plant performance metrics and impactful environmental and physiological parameters. Managing variable rate applications for optimization means developing and deploying variable rate management systems (fertilization, irrigation and pesticide spraying) to maximize productivity and quality within each production block.
Consider mechanical pruning. “If you track man hours per acre, pruning can be one of the most labor intensive actions at a vineyard,” said Thomas. To make the task more efficient, they’ve employed the V-Mech trailer, which involves less hand labor (but in his experience, some is still needed). “This method of pruning has the ability to leave a large number of growing points, leaving the potential for a large yield. It’s less expensive than trimming by hand, and it doesn’t need to be used every season.”
Thomas noted that the same process behind variable rate fertilization can be used to determine variable rate shoot thinning. Growers can use the cluster counting method to verify. It’s all about turning data into actionable events.
It all begins with taking critical measurements, explained Nick Dokoozlian of E&J Gallo Winery in California. Model your measurements against pruning, irrigation, etc., and see how they vary based on your desired production outputs.
For example, at their vineyards they found 46% of their variance came from the soil’s water holding capacity, so they focused on irrigation and switched to variable rate drip irrigation (VRDI). They used satellite imagery to determine irrigation amounts. Doing so provides the farming efficiency of one large block with the irrigation efficiency of many small blocks.
“When we think about the basis of precision agriculture, it’s based on yield maps,” he said. “They’re a vital element in developing technology.” How vital? The information gathered which led to VRDI improved vineyard uniformity after only two months. Yields increased 10% – 15% in their trials; fruit and wine quality was maintained or improved; and water use efficiency, measured in tons produced per unit of applied water, increased 15% – 20%.
Dokoozlian added that early season irrigation management is critical, because low vigor vines require irrigation more frequently and much earlier than high vigor vines. The good news is research is continuing on optimizing irrigation timings and amounts for desired vine responses.
Precision is required in sprayers too, and the technology is advancing there as well. Washington State University Assistant Professor of Biological Systems Engineering Lav Khot said intelligent sprayers are needed because of changing vineyard architecture/training systems and application technology (considering efficiency and economics, maximum residue limits and consumer awareness). To work properly, however, intelligent sprayers need canopy sensing, geolocation/ground speed measurement, an easy-to-use user interface for rate/flow control and the appropriate nozzles. The machinery could use ultrasonic sensing (sound waves bouncing off objects to measure time of flight to distance), but a lot more has been done using LiDAR (a method for measuring distances by illuminating the target with laser light and measuring the time the reflection of the light takes to return to the sensor).
New (and sometimes expensive) machinery isn’t always needed for precision. Dr. Heping Zhu of USDA-ARS said universal automatic control systems can be retrofitted on existing sprayers. They use an embedded computer, touchscreen and switch box, algorithms, a speed sensor, a laser sensor, a variable-rate flow control valve and a flow controller to better apply pesticide and fungicide sprays. On-farm tests demonstrated intelligent sprayers minimized off-target losses (up to 87% reduction in airborne spray drift and between 68% and 93% reduction in spray loss on the ground); reduced pesticide use by 47% – 70%; and resulted in annual chemical savings of $140 – $281 per acre, all with comparable control of pests and diseases.
The technology for precision management is here now, and only getting better. The biggest needs it has are more training and outreach.