Curt Pierce, UCCE Glenn, Tehama, Colusa, and Shasta Counties
Franz Niederholzer, UCCE Colusa and Sutter/Yuba
Jaime Ott, UCCE Tehama, Shasta, Glenn, and Butte Counties

 

With good prices and good bloom weather, prunes are looking to have another profitable year. To make the most of that, set yourself up for success by producing a large crop of large fruit. By far the three most important management decisions dictating fruit size and crop size (and therefore grower returns) are 1) cropload management, 2) irrigation, and 3) nutrient management (especially potassium). Give these “Big Three” the attention they deserve to make the most of this year’s crop.

 

1. Manage cropload appropriately. This looks to be another year where reference date fruit thinning will be an important tool for producing an economically viable crop. Despite our large crop last year, many orchards had a good return bloom and good percent set. Thinning fruit on or just after reference date has been shown to increase profits by increasing the number and tonnage of A and B screen fruit. See this article for information on assessing cropload and determining a need for thinning. Even if you think your crop is light, it is worth stripping a tree or two to verify cropload.

During thinning, the most crucial decision is how much fruit to leave on the tree. Be realistic about the tonnage per acre and the number of fruit each tree can size: if the trees carried 6T/acre in the past few years but you had too many undersized fruit, it is unlikely that the trees will be able to adequately size a 6 T/ac crop this year. 3-4 T/ac of good-sized fruit will likely pay better and will lead to less stress on your trees.

2. Manage irrigation for fruit size. When considering early season irrigation in prune, the best approach is to monitor tree water status to determine the timing of irrigations whenever possible. Too much soil moisture early in the growing season can result in leaf yellowing from iron chlorosis. An excellent start to the 2024 water year and rainfall persisting into late spring may equate to soil moisture contents being higher in the effective root zone than expected. While well-placed soil moisture sensors provide useful information, only pressure chamber readings of the tree water status will let you know when the trees are ready for additional irrigation.

Your goal with irrigation should be to balance soil moisture, keeping it neither too wet nor too dry. Partially wet soils in the root zone allow for maximum growth of the new roots, which can best uptake water and nutrients from the soil. Saturated soils inhibit root development, leading to root rot. It is also critical to not allow orchards to dry out fully, as drought stress reduces final fruit size.  Read this article for more information on drought stress effects on fruit size. Rewetting soils that have previously thoroughly dried out can lead to end cracking on fruit later in the season. Balance in soil moisture is of the utmost importance, and managing tree water status with a pressure chamber, combined with the use of soil moisture sensors to help inform your irrigation plan, is the key to healthy, productive trees.

 

3. Maintaining prune orchard nutrition is critical to producing a large, high-quality crop and maintaining good orchard health. The key nutrients in prune orchards up and down the Sacramento Valley are nitrogen (N), potassium (K), and zinc (Zn). Other nutrients may be important in individual orchard sites, but these are the three to focus on.

Potassium is particularly important to fruit production and prune orchard health. Deficiency of this nutrient can result in series of terrible events for a prune orchard– leaf loss, sunburn of now exposed wood bark, Cytospora infection of sunburned bark, and tree death as the Cytopsora spreads and girdles the scaffold or trunk.  Cytospora can stay active in the tree over a number of years (unless a very good pruning crew can see and cut it all out). Don’t sleep on potassium nutrition, especially in a heavy crop year following a heavy crop year.

These are tough times for tree crop growers in the Sacramento Valley. Trimming nutrient costs, where necessary, not eliminating them is recommended. Instead of “saving” by eliminating or sharply reducing fertilizer application, the recommendation is to focus on efficient application practices to trimming costs while maintaining orchard health and productivity. Examples of these practices include multiple small N and/or K fertigation “shots” timed to match tree nutrient needs or a foliar zinc spray in the spring or fall with a proven fertilizer such as zinc sulfate or basic zinc sulfate (neutral zinc).

 

Find Small Improvements: The 5% Rule

After years of removing acreage to adjust to a changing market, California prune growers are now receiving a higher price. Data from USDA-NASS shows that prune price received has been trending upwards for the past few years (Figure 1). However, rising production costs continue to squeeze profit margins.

 

The five percent rule can be an effective principle for improving profits. The rule advocates for small improvements across multiple aspects of an operation rather than striving for large gains in one or two areas. Coined by Danny Klinefelter, the rule suggests that a 5% increase in price received, a 5% decrease in costs, and a 5% increase in yield will often produce more than100% increase in net returns. This outcome is possible because the effect of these small improvements is cumulative, multiplicative, and compounding, and not a simple 15% (5%+5%+5%) increase.

Below is a simple per-acre illustration of how small improvements in yield, price, and cost together can lead to big gains in profits.

Together, these 5% improvements increase profit from $1,000/acre to $2,018/acre— a 102% increase in profit. Many individual producers are price ‘takers,’ so they do not have control over the price they receive for their product, even when their cost of production increases. In this illustration, if cost can be cut by 5%, yield increased by 5%, and price remains the same, then profit will increase by 65%.

The whole idea is to focus on achieving small, incremental changes across multiple areas of your operation and not chase drastic improvements in only some aspects, which can be expensive, risky, frustrating, or lead to missed opportunities.

Start by conducting a thorough evaluation of your operations to identify opportunities for small improvements. It is dangerous to get stuck in the mindset of “We’ve always done it this way,” as Kristjan Hebert emphasizes in his presentation ‘5% Rule-Baby Steps to Bigger Profits.’ Actively seek out recommended practices that could potentially boost your production efficiency and yield. For example, timely thinning and harvesting are key to large, high-value fruit production, while also reducing harvesting and drying costs. Optimize your fertilizer usage by applying small doses throughout the season rather than in large slugs at one time. Decrease weed management costs by reducing the frequency of spraying or mowing, rather than cutting weed management all together. Generally, growers should continuously assess all aspects of their operation, seeking opportunities for cost reduction, yield improvement, and potentially commanding a higher price.

Consistency is key to adhering to the 5% rule. It is an ongoing process and cannot be achieved overnight. It requires consistently striving for small improvements year after year, to experience the big cumulative effect.