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Efficient Vineyard: Fertilizer Application

By Kevin Martin

The Efficient Vineyard project offers the opportunity to use sensor technology to improve viticulture decision-making, particularly within vineyard blocks.  To best describe the approach, I like to borrow the philosophy and words of former Fed Chair Janet Yellen, “data-dependent decision making”.  This project has two primary goals.  One is to provide growers with the tools to get relevant data.  The other is to learn and show growers how to effectively implement that data to improve viticulture decisions.  Effectiveness and efficiency involves both viticulture and economics.  As we talk about implementation of data dependent viticulture, we want to make sure sensor-technology improves vineyard profitability.

The federal reserve has been working for the better part of a century to figure out how to actually use data to improve decision-making.  Hopefully, with this project, we can work a little more quickly.  It does provide some context though, data by itself is not particularly useful.  Variable rate management has the potential to provide some assistance.  It unloads some of the complexity of decision-making onto computers.  While the vineyard manager sets parameters, the operational details of machine action fall to the tractor computer.

Variable Rate Spreader owned by Betts Farms LLC

One specific area that has vineyard managers and industry collaborators excited is variable rate fertilizer management.  This particular practice is easier to visualize impacts than others; it has also already been adopted in field crops.  It is likely that utilizing variable rate technology borrowed from other applications could be useful to spread fertilizer.  The tractor computer, sensors and GPS can all be purchased for more economically significant practices and then used for fertilizer applications.

In bulk juice and wine production fertilizer materials cost for maintaining healthy soils is approximately $150 per acre.  This represents around 10% of the total cost of production and can easily be recouped by higher yields associated with healthy soil.  The benefits of variable rate from the perspective of saving fertilizer, therefore, are somewhat limited.  Work really needs to be done to understand how much potassium and soil pH vary spatially within vineyard blocks.  By understanding that variability we can begin to understand if there is an economic justification for variable rate fertilization.

The limits on the economic benefit are set by the bounds of fertilizer recommendations.  Recommendations for applications in bulk juice range from $220 per acre – $75 per acre.  Rarely do test results justify material costs outside of that range.  Spatial application of fertilizer also costs more.  Soil and petiole test results usually increase from $1.50 per acre to $5-$10 per acre.

Vineyards already stratifying soil samples based on sensor data, without an organized research trial, did observe spatial variability.  While it appears likely that research trials could find statistical differences, I am skeptical the results will be economically meaningful.  I find it more likely, in the majority of cases, that savings will be limited because fertilizer inputs are already fairly efficient.

The opportunity for a meaningful impact will require research to determine actual variability in soil health as well as the ability of fertilizer to mitigate those soil health issues.  It is more likely, in bulk juice and wine, this savings will be a result of increased spending on fertilizer and higher yields.  Vineyards in this sector typically operate with a mission to minimize inputs already.  It is likely that perspective is causing them to under-apply most nutrients. 

As growers consider variable rate technology, conversations with the Efficient Vineyard extension team is a good place to start.  My role has been in developing both traditional fertilizer budgets as well as variable rate budgets to compare the material costs of both operations.  Individually, so far, growers have had very different capital needs to transition from traditional application to variable rate.  Capital costs range from $1,500 – $40,000, depending on the current equipment owned by the grower.  For growers that already have variable rate technology, modifications to some fertilizer spreaders will be minimal.  Particularly if these growers already take a significant number of soil samples, adding variable rate technology will cost less than $2,000 for the entire operation.  Their biggest costs will be the time of and lab fees for additional soil tests, if necessary.

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