Napa 2016: Analysis of climate conditions before bud break

bud break vine leaves

As we are now seeing bud break at many California vineyards, it is important to compare the climatic conditions this year with prior years in order to adjust your management practices later in the season. This blog post provides an analysis of the climatic conditions in Napa before bud break during the 2016 growing season. It aims at providing a reference to compare with 2017.

To begin with, let’s look at rain accumulation during the winter months to get a sense of water abundance at the start of the growing season. In 2016, Napa had a constant supply of rain between November 1st and March 1st, compared to 2014 and 2015 when drier periods were observed during the winter. In 2017, cumulated rainfall is higher and as we discussed in another here  and here, this should affect soil microbiological activity positively which in turn could increase plant nutrient availability.

Rain input before bud break

The 2016 thermal time before bud break showed somewhat similar growing degree day (GDD) accumulation to 2014 and 2015. The 2016 growing season saw a warmer November followed by a colder period relative to 2015 due to El Nino.

thermal-time-before-bud-break

Thermal time before bud break

Important rain supply combined with a temperature accumulation profile relatively warm (350 degrees days by March 1st), climatic conditions enhance nutrient mineralization rate and subsequent root uptake. When plant Nitrogen uptake is higher year N, we can expect higher yields year N+1, as it has been reported in the literature (Guilpart et al, 2014).   

On a more ecophysiological level, interesting questions to ask are:

  1. When a steady water supply is combined with warm soil conditions during the winter before bud break  (like 2016 or 2017 in California), how does it affect soil microbiological activity compared to a dry winter (like 2014 in California) ? “
  2. How are nitrogen mineralization and plant nutrient uptake affected by a greater soil microbiological activity?

We have pointed out earlier that the 2017 conditions so far may favor high nitrogen uptake and stronger vegetative growth. If this turns to be true, then it will be interesting to see:

  1. How different is the 2017 leaf nitrogen content from the 2016 season?
  2. How strongly will the resulting foliar development affect vine water needs in 2017?
  3. How does this impact yield variations in 2018?

Tracking your water use and nitrogen levels helps you determine the best strategy to use in your vineyard in response to variable weather conditions.

What have you done differently this season compared to last year? Share with us!

Fruition Sciences offers a full suite of products addressing a variety of vine health monitoring needs to enhance fruit and wine quality. Our DualexⓇ Signature product provides detailed nitrogen accumulation profile so that vineyards can apply fertilizer where and when it’s needed. Dualex recently won the 2017 Wine Business IQ Innovation Award.

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4 Comments

  1. I found this blog post interesting because Nitrogen seems difficult to monitor and manage. Nitrogen is a plant essential nutrient but Nitrates can contaminate groundwater. If we must wait to see how Nitrogen will effect yields in year N+1, then how control do vineyard managers actually have when applying fertilizer? How much fertilizer is too much fertilizer? How necessary is fertilizer after a wet winter in California?

    1. Hello Cameron,

      You can start asking yourself: do I really need to fertilize year N?
      as a winemaker or vineyard manager, what is your analytical method to decide that nitrogen level is too low? and at what time during the season is it appropriate to be making that judgement call?

      Regarding triggering an alert for fertilization: you may ask yourself 2 questions: are you willing to fertilize based on:
      – a higher threshold because you maximize plant photosynthetic activity (helping the plant to produce more leaves) or,
      – a lower threshold, because you want to improve fruit composition (in which case a moderate nitrogen deficit may be desirable, particularly for reds).

  2. Greetings! Very useful advice in this particular article!
    It’s the little changes that produce the greatest changes. Thanks a lot for sharing!

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