If you manage an orchard, a lot goes into ensuring you have healthy crops from year to year. This can include taking proper steps in the fall and winter to ensure your irrigation system is in top shape for the spring , as well as careful pruning to encourage new spurs and strategically remove old growth.
Proper fertilizing can be an essential part of your orchard management. Fertilizer provides nutrients directly to your trees. Plants don’t eat fertilizer they drink it. This why it is important to know what you are feeding your trees. Trees convert sunlight in photosynthesis and provides carbohydrates as a food source for plants. However, depending on your soil composition and health, your plants may not have optimized levels of nutrients. Trees absorb nutrients to assist with plant and fruit growth. However, when we harvest that fruit and remove leaves and other organic materials from the local ecosystem, those nutrients don’t have the opportunity to break down and restore nutrient levels. This is where fertilizer comes in. Typically, when we talk about nutrients in fertilizer, we’re talking about nitrogen (N), phosphorus (P), and potassium (K).
Considerations for proper fertilization
Just like over-pruning can stimulate too much green growth, meaning your tree has fewer resources to develop flowers and fruit, over-fertilizing has downfalls. Too much nitrogen can promote the overgrowth of woody material and leaves, but not many flowers and fruit. When large quantities of excess nitrogen enter waterways, it also creates harmful algal blooms and dead zones.
Caring for your soil is an important aspect of total orchard care. Fruit trees like fertile, well-drained soil. In Southern California, growers usually apply fertilizer in the spring right before the bloom and through May. Testing your soil will tell you which nutrient deficiencies your soil has, determining what fertilizer composition is ideal for your orchard. If you need fertilizer for your orchard, it’s critical to understand your options.
Different types of fertilizer
There are a few options of fertilizer types that will provide the amount of N, P, and K your trees require. You have plenty of specially-formulated fruit tree fertilizers on the market, and your orchard management operations and goals will help you determine which kind to get. With any fertilizer, calculate how much you need and follow instructions precisely.
Powdered fertilizer is a top choice for orchards. It can be applied around your trees’ bases in powder form or diluted in water. Powdered fertilizers are economical and straightforward to apply across large operations.
Like powdered fertilizer, granular fertilizer comes in specifically-formulated solid granules. Unlike powdered fertilizers, granular fertilizer is not meant to be diluted in water but applied as-is to your soil. Each granule has equal quantities of nutrients, facilitating consistent nutrient distribution around your root systems.
Using liquid fertilizers means you don’t need to mix your own concoction, as you would if you were choosing to dilute powdered fertilizer with water. It’s a versatile option that you can blend with crop protection products. Some liquid fertilizers can be foliar applied which allows for great nutritional uptake. However the crops need cannot all be fulfilled with just foliar application, so soil applied liquid fertilizer will complete the crop needs. Not all soil liquid fertilizer are all the same, consult with crop consultant to assist with choosing the correct fertilizers.
You can find fertilizer spikes that you drive into the ground that are supposed to release nutrients into your soil over time slowly. While this option is convenient, nutrients’ ability to travel through the soil is limited, and one area of the roots may get high quantities of nutrients while the rest of the root system gets little or no nutrients. Liquid and dry fertilizers ensure the even distribution of nutrients to the roots of your trees.
Organic vs. synthetic fertilizers
There are many options on the market for both organic and synthetic fertilizers. Organic fertilizers are plant or animal-based and release nutrients more slowly over time, reducing your risk of root scorch. Organic fertilizers generally mimic nature’s processes of breaking down residual harvest and leaves into nutrients in the soil. You can find fruit tree-specific formulations or select a general option like composted chicken manure, feather meal, or soybean meal. Synthetic fertilizers contain higher levels of nutrition availability to the crop. The potential problem with synthetic fertilizers is the way they are manufactured. The potential is higher salt levels which can lead to crop burn. Please consult with your Crop Consultant or your PCA (Pest Control Advisor) for additional support.
Compost green manure and composted animal manure is another option to provide for your trees. Compost offers soil microbes that any of the conventional fertilizers don’t offer. When fertilizers are applied plant cant take it up in solid form. Plants don’t have teeth. The plant nutrition need to be soluble form for plant to be taken up by the roots. The ground has some native microbes in the soil but compost adds so much microbes to the soil and allows for better uptake.
How much fertilizer to apply?
Consider how much fruit you pull off the trees. With the average California yield of 22,500 lbs/acre, which corresponds to 300 boxes of 75 lbs, between 26 and 42 lbs N are removed from the field. Also consider how much you prune before you apply fertilizer. If you prune a tree significantly, reduce how much fertilizer you use to avoid extra growth. Be mindful when you are fertilizing not to over-irrigate, either. Unlike Potassium and Phosphate to much water will leach Nitrogen past the root zone. Soil that’s too wet can also lead to root rot and a lack of growth when roots can’t access proper quantities of oxygen.
Regardless of what type of fertilizer you choose, follow instructions to the T. You might need to calculate how much fertilizer your trees need, depending on your soil test results. This resource from Colorado State University walks you through calculating exactly how much nitrogen your soil needs depending on soil test results or annual growth rate. Also please consult with your crop adviser collect tissue and soil samples to provide the correct prescription for your trees.
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