Chilling Requirements in Chill Portions for California Crops

Comments (8)

1. 

   Adam

   January 23, 2015

   I saw the chill portion number for Non pareil as 23 and range for almonds as 22 – 32. My question is what kind of yield did an orchard with a chill portion number of 23 have as compared to an orchard that had a chill portion number of 32 or higher. I have heard of orchards with chill portions in the 50s ending up with yields of over 3500 pounds/ac. I would appreciate your thoughts.

   Reply
   • 

     Katherine Pope

     January 24, 2015

     Great question, Adam. There’s no research that has looked at this directly, but I’m inclined to think more chill could harm you more than help you. We know that broadly speaking the more chill the buds get, the more compact the bloom. The shorter the bloom window, the tougher it is to get all those flowers pollinated. Most of the studies that estimate chilling requirements are based on bloom success or bloom timing. Researchers cut a dormant branch and put it in a growth chamber to replicate spring temperatures. If it blooms in 2 weeks, they say it has met it’s chilling requirement. Then they go count how much chill accumulated in the field before cutting the branch. I did some research that looked back at county crop report data. I found that on a county basis, yields can be above average in California with chill as low as 22 chill portions (counting Nov 1- Dec 31). Whether doubling that chill could take you from average to stellar yields – there’s no research on that. If anyone reading this wants to send me 30+ years of block-specific yield data, I could take a crack at it. But there’s obviously a lot between bloom and harvest that can interfere with high yields, so it’s hard to say.

     Reply

2. ‘Spring’ already? | Fruits and Votes

   January 27, 2016

   […] year, partly due to the youth of the trees, but probably mostly because the chill hours (or “chill portions“) were in the area were quite low last year (which is an ongoing trend). This winter, […]

   Reply
3. 

   Ron Bell

   December 12, 2017

   Question: if I was to apply a rest breaking agent on Non-Pareil and Monterey varieties, how many chill portions would you target as an application date? I am working on a block of almonds in Kern Co., with the warm winters the Sonoras are blooming sooner than the Non-Pareils and Montererys with poor or any overlap. We have applied Surround to the Sonoras without measurable success to try to slow the bloom. So this year I thought we would try to speed up the N.P. and Montereys.

   Reply
   • 

     David Doll

     December 15, 2017

     Ron,
     I am trying to get an answer for you, but which rest breaking agent are you planning to apply?

     We have done limited work with rest breaking agents due to minimal effect in plant response. Generally, the strategy described above would only assist with pollinating the Sonoras as Sonora pollen is already in the hive for the Nonpareil bloom. In contrast, it may negatively effect the Nonpareils and Montereys due to an accelerated bloom. I would approach with caution.

     David

     Reply
4. 

   Otniel

   January 7, 2018

   Hi,
   Could you say me what’s the chill portions requirement for grapes?
   and where can I found the requirements for each variety of grapes?

   Thanks

   Reply
   • 

     David Doll

     January 13, 2018

     Check out the Fruits and Nuts Center at UC Davis (http://fruitsandnuts.ucdavis.edu/). They should have that information there.

     David

     Reply
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   Reply