Improving Yield and Fruit Quality with Precision Management Tools

By: Becky Garrison

At the United Wine Symposium Virtual Conference and Trade Show held online from January 26-29, 2021, Dr. Nick Dokoozlian, Vice President of Winegrowing Research at E&J Gallo Winery, Bob Thomas, Mesa Vineyard Management, and Dr. Lav Khot, Asso-ciate Professor of Precision Agriculture at Washington State University, offered their insights regarding precision management in vineyards. In their presentation, these ex-perts gave their perspectives regarding how growers seeking to thrive in this ever-changing market can produce high-quality fruit while reducing inputs through techno-logical inventions.

Addressing Yield Variability and Fruit Quality with Technology

  Dokoozlian described how E&J Gallo assesses the overall performance of their vine-yards. “Yield maps have been a vital and critical element to advancing precision prac-tices,” he said. They outfitted their mechanical harvester with yield monitors that pro-vide real-time monitoring of plant growth and canopy health, plant and soil water and nutrient status, pests and diseases. “We take that data and model it against other block data layers including soil type and plant available water content to better under-stand the causes of yield and fruit quality variability.”

  After a few years, Gallo developed a model that explained a good portion of their block yield variability. Not surprisingly, most of their vineyards showed significant variability, with up to 40% of the vines in a block producing below the mean block yield and 30% producing below the mean block fruit quality. The parameters driving this variability included plant available water, subsurface soil compaction, and soil texture.

  In Dokoozlian’s assessment, plant water availability in the soil is typically the most significant variable driving vineyard yield and fruit quality variability. Early season irrigation management is critical with low vigor vines, requiring irrigation more frequently and much earlier than high vigor vines. To determine those vines that need additional wa-ter, they began to understand the power of remote sensing. Through satellite images, they learned to spot those areas where the vines are stressed and need more water compared to other sites where the vines are not stressed and receive adequate water.

  Simply adding emitters to low vigor vines using a traditional drip system failed to pin-point these specific areas that need additional water. “When we flip the switch on our drip irrigation systems, we typically apply the exact same water to all vines in the block. We irrigate that block somewhere in the middle of those two ranges to hit the average. But the reality is we’re under watering or over watering many vines,” Dokoo-zlian said.

  Dokoozlian said precision irrigation (VRDI) is an effective tool to manage vineyard variability. VDRI can irrigate individual portions of the blocks independently from each other. After two months of using VRDI, they noticed improved canopy uniformity with yields increasing 10–15% and water use efficiency – tons produced per unit of applied water – increasing from 15-20%. Also, fruit and wine quality was maintained or im-proved.

  Despite these promising results, Dokoozlian points to the need for more research to optimize irrigation timings and amounts for desired vine response using VRDI and asess the impact of fruit quality uniformity on wine quality. At present, the cost and operational complexity of VRDI systems are the primary challenges for growers looking to adopt VRDI in their vineyards.

Variable Rate Fertilization

  In his presentation, Bob Thomas spoke to how variances in the soil due to different nutrients can be addressed by changing the methods used to fertilize the soil. The standard fertilization – adding nutrients through the drip system – works correctly in most instances. In this method, each vine receives the same nutrient addition with minimal application cost. Also, compost is usually applied by a spreader at a fixed rate.

  Through aerial imagery, Thomas illuminated how Mesa Vineyard Management could spot weaker growth in areas of lighter soil that they needed to address. “We looked at variable rate applications to apply different rates down the row,” he said.

  They started by putting the basic data on a bigger map to image the soil map. A prescription map featuring the flow rate was loaded into the platform to show the different zones along with the amount of compost they wanted to spread in each zone. This platform monitored tractor rotation in the field with compost applied at the prescribed rate.

  Calibrating the spreader is the most crucial step, according to Thomas. The compost was measured and adjusted to fit the desired rate of application. They set the spreader to apply the highest rate on their prescription map and slow the rate of discharge by closing the flow down to a lower rate. In Thomas’ analysis, this method can be used for pre-plant soil preparation to add soil. “A prescription map allows you to apply specifi-cally what is needed at the desired rate in the desired location.”

Benefits of Mechanical Pruning

  During Thomas’s talk, he noted that mechanical pruning works best when set up cor-rectly from the beginning rather than retrofitting later in the process. He briefly ad-dressed the pruning limitations on labor availability and how labor cost gave rise to mechanical pruning as an alternative. “If you track man-hours per acre, pruning can be one of the most labor intensive man-hours in the winery,” he said.

  Mesa Vineyard employed several methods to minimize the man-hours per acre, rang-ing from pre-printed coordinates to box pruning the entire cord using a variable rate pruning method. This method allows a technician to prune two rows simultaneously while adjusting the pruning blades’ location up and down or side to side as the blades move down the row.

  In Thomas’ estimation, “This method of pruning has the ability to leave a large number of growing plants, thus allowing for the potential of increased yields.” Also, hand cleanup after mechanical pruning is not necessary every season.

Use of Intelligent/Precision/Smart Sprayers

  Lav Khot addressed technological developments beneficial to growers when applying chemicals or pesticides. In particular, he pointed to the technological developments afforded by intelligent precision or smart sprayers. In addition to targeting the specific areas in the vineyard where these chemicals are needed, these sprayers also help cut down on any drift that can impact both the plant’s environment and the customer consuming the wine and grapes. “There’s a moral issue of reducing maximum residue limits or pesticide residues on the produce,” Khot said.

  Khot introduced the audience to the new laser-guided, variable rate intelligent sprayer. Khot briefly described the universal automatic control system that can be retrofitted on existing sprayers for those who wish to adapt an existing sprayer.

  He focused on how to make these sprayers both intelligent and effective. First, use a sensor that can read a canopy’s attributes, such as volume and density, and adjust the spray rate accordingly. “We’re already using what is called LIDAR (Light detection and ranging) to get the point cloud data of the canopies,” he said. One can also utilize remote sensing data to map the canopies using drones.

  A Pulse Width Modulation System can be employed to activate the nozzles on the back of the sprayer. This allows the sprayer to fine tune the individual nozzles by controlling the amount of liquid coming out of each nozzle. In this work, nozzle selection is critical to ensure accurate results. Once the base dosage – one ounce of liquid per cu-bic foot of canopy – is optimized for chosen crop and canopy architecture, this pro-cess reduces the need to estimate the dosage and application rates.

  In conclusion, Khot points to the necessity of educating those operating this equipment on how to utilize this technology best. “We need to have a service sector for growers to use this technology properly. In the next few years, we’ll see some of that happening as more growers try to use this technology,” he said.

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