Water Stress, Early Hullsplit, and Kernel Size

I have been getting a few reports of hull-split in almonds from varying points across the state. We were expecting an earlier than normal hull-split, but many would agree that this is earlier than expected. Much of the splitting trees are in the more stressed areas of the fields, or in orchards with reduced water allocations. Although I haven’t observed this until this season, early hullsplit induced by spring-time water stress has been described in the literature.

In many cases, when we discuss water stress in almonds, we tend to focus on the post harvest period and the impact on next year’s crop. There are, however, impacts on in-season yields which are dependent on stress timing. Severe tree stress rarely occurs during the initial period of stage one of fruit growth due to stored soil moisture, but if it does, smaller fruit (shell and hull) will be observed due to reduced cell division and expansion. Stress during stage two (Late April/early May through Late May/early June) leads to a reduction in carbohydrates being allocated for kernel fill, leading to smaller sized kernels.  Stress imposed during stage three will reduce kernel dry weights, leading to textured or shriveled almond kernels. This loss of kernel weight during stage three is not just due to a reduction of carbohydrates, but also a reduced assimilation of carbohydrates due to an accelerated hull split.

Although cultivar dependent, these two in-season factors – lower cell division or expansion and the disruption of carbohydrate transport into the kernel from an early hull split – contribute to reduced kernel size and yields.

Information sourced from FAO Irrigation and Drainage Paper 66: “Crop Yield Response to Water: Almond” Pgs 358-373.


Print Friendly, PDF & Email

5 thoughts on “Water Stress, Early Hullsplit, and Kernel Size

  1. Pingback: C.I.T FOODS – Commodities International Trading – California Almonds: What To Expect With Water Stress This Year

  2. I’d be interested to hear what you think of the fruit set in the stressed areas of the fields David. We’ve seen the 10-14day earlier onset of hullsplit in our water stressed trees for the last 5 years (experiment trees). An interesting effect also seems to be an increase in the number of flowers and kernels – albeit only filling to 2/3rds of the full irrigation trees. I think we might even see a greater apparent biennial bearing in trees that were stressed, with a large number of flowers and fruit in one year tending to be mostly vegetative in the next year.


    1. Dave,
      We are seeing the 10-14 day earlier hullsplit. Fields that are more severely stressed are ahead in their nut development. Some trees in the drier areas of the field are splitting, while others are still holding tight. Im not sure about the flowers and kernels. Will keep an eye on the trees as we enter into next year. I would suspect that our inability to adequately apply water during the postharvest period this year may impact floral bud development, reducing bloom density…but we will see.

  3. Pingback: Impact of Deficit Irrigation on Almond Kernels - The Almond Doctor

  4. Pingback: 2014 Top Ten Articles - The Almond Doctor

Leave a Reply

Your email address will not be published. Required fields are marked *