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Ag Starter



It is May 15, 2019 and in Northern California it is raining. The major production area for sweet cherries in California is in San Joaquin county. Cherry farmers there are very concerned about their crop when the cherries are ripe on the tree! Why?

Also, a local news station announced that other tree crop farmers like the rain because it will cause them to irrigate less. Is that an accurate statement?


  1. Sweet cherry growers are very concerned about rain when cherries on the tree are in the later stage of ripening. At that time of their development rain can cause the cherry to develop splits – particularly near the stem attachment to the fruit. Splits make the sweet cherry worthless in the fresh market which is the destination for most sweet cherries grown in California.
  1. Spits are not only cosmetically undesirable, but the split offers an entry point for diseases.
  1. The rainfall forecast for Woodland, Ca. (where I live) for today (Wednesday, May 15, 2019) is for 0.77 inches, 0.14 inches for Thursday, 0. inches for Friday, 0.55 inches for Saturday and 0.03 inches for Sunday; a total of 1.49 inches from today thru Sunday.
  1. I (the author of this AgStarter) make estimates of periodic irrigation requirements for local tree crops, including walnuts. Recent daily estimates have been calling for about 0.11 acre-inches of irrigation water per acre per day for walnuts (which is below typical historical needs of about 0.20 acre-inches of water per acre per day).
  1. If the rainfall forecast is accurate and we get 1.49 inches; and if walnut trees need about 0.11 inches*

per day during this period; then the rainfall will supply walnuts with about 14 days worth of irrigation

(1.49 inches “supplied” ÷ 0.11 inches per day needed = 13.6 days). So in this instance, I will have to

irrigate less and can rely on Mother Nature doing my irrigation.


  1. However……even though rainfall during this period can save irrigations, there are other

detrimental effects on crops and growing practices. Because moisture can trigger fungal diseases, rain

during this period of time may cause a grower to apply fungicides which is costly. Rainfall may also

preclude the grower from getting into an orchard to do routine tasks such as mowing weeds.


*Irrigation water requirements are acre-inches per acre per day, but may be shortened to inches per day.

Activities and/or problems

  1. What is the name of the predominant variety produced in California? What is the name of the variety

that is a “yellow cherry with a red blush and light yellow flesh”?


  1. How many 18-pound packages of cherries are harvested between April and June? What does that

convert to in tons of cherries. How many acres of cherries are grown in California? What percentage of

cherries are exported around the world. From the information above, what is the yield of cherries in

tons per acre.


  1. Can students list other impositions to farming practices in their area due to unseasonal rain?



  1. In Fact #4 above, you learned that walnuts are using approximately 0.11 acre-inches of water per acre

per day at this point in time. If there are 27,154 gallons in an acre-inch per acre, how many gallons

does an acre of walnuts use in a day at this point in time?

Bonus problem: If your walnut orchard has 75 trees per acre, how many gallons does one tree use at

this point in time?

references and USEFUL URLS


  1. Why do cherries split? Copy and paste the following URL into your browser:

Why do cherries split?


  1. Calcium chloride reduces splitting in sweet cherries. Copy and paste the following URL into your browser:


  1. Current South Sacramento Valley ET Report – May 10, 2019. Copy and paste the following URL into your browser:

Current South Sacramento Valley ET Report – June 7, 2019



  1. California Cherries. Copy and paste the following URL into your browser:

learning outcomes


  1. Students will learn of affects of rainfall on California sweet cherries near harvest season.
  2. Students will learn of other affects of rainfall to other crops during the same period of time.