Here is some current information you may want to use while making crop adjustment.
Weather: Prior to bloom, we had several weeks of below average temperatures which put us approximately 9 days behind the long term average. Since bloom, we have had above average temperatures which have allowed us to catch up on heat units - although we are still approximately 3 days behind the long term average (see weather figure). The above average post-bloom temperatures in 2003 have also increased the rate of berry growth above the average. At the Fredonia Lab, 7/15/03 marks 20 days after bloom and berry weight should be approximately 25% of their final weight. However, current berry weight measurements are placing berry growth at approximately 30%. I even looked at one vineyard that might suggest more like 35% of final berry weight. Therefore, if you clean pick vines today (20 days after bloom) you should multiply the weight by 3.33 (100/30 = 3.33) to get your projected harvest weight. Do not multiply by 4 (100/25 = 4) to get your harvest weight as the average berry curve might suggest (see berry curve chart). Go to http://lenewa.netsync.net/public/Bates/071503_update.htm to see the graphs from Dr. Bates article.
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For example, a grower picks 50 pounds of fruit at 20DAB on 1/100th of an acre and used the easy method based on the average berry weight curve. 50 pounds times 4 (to get from 25% to 100% final) = 200 pounds. 200 pounds x 100 / 2000 = 10 tons/acre crop estimate. However, according to the 2003 actual berry weight information, 50 pounds times 3.33 (to get from 30% to 100%) = 166.5 pounds. 166.5 pounds x 100 / 2000 = 8.325 tons/acre crop estimate. Nearly 1.7 ton/acre difference.
If favorable weather continues, berry weights will most likely be more than 50% of final at 30 days after bloom. Therefore, the easy 'pick 1/100th of an acre and move the decimal place' may not be applicable at exactly 30 days after bloom. Stay tuned, I will send out more current 2003 berry curve information as it comes in.
Precipitation: We have had below average precipitation so far this year. In fact, precipitation is tracking similar to 2001. In the next 10 days or so, hand pruned Concord will reach 100% canopy fill and (given the temperature and day length this time of year as well as the high crop load) the vines will be demanding near their maximum amount of water. Intensive floor management is needed to conserve what soil moisture is left in the soil so that it may be used by the vines and not by the weeds. Once the water in the soil is gone the only way to get it back is through rain or irrigation. The goal is to remove weeds from the vineyard: thick mulch is better than herbicide is better than cultivation - but they are all better than any kind of weeds in the vineyard.