Saturday | March 25, 2017
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Garden Guy: Tips for boosting tangerine production

Greetings, enjoyed your article this morning. Any ideas about how to boost production for a tangerine harvest for next month that does not involve the use of triple 16? These trees have basically been uncared for a few years. I’d prefer not to use chemical alternatives —insufficient time nor rainfall to rinse out the fruit. Fish emulsion? Pointers appreciated!

Unfortunately, now is a little too late to boost production for a harvest that is 30 days away. A key time to apply nutrients is actually before bloom, with additional applications as the crop matures. Apply fertilizer, especially nitrogen, prior to bloom so it is available to the plant roots and in the plant when the tree flowers.

A soil analysis to check the levels of nutrients such as potassium and phosphate and even calcium and magnesium is strongly recommended. In rainy climates, nitrogen will always be low because of heavy leeching by the rain.

By all means, use organic fertilizers. But first, let me explain why the commercially produced inorganic fertilizers like triple 16, among others, have become popular. The main advantage is they are less expensive and require a much smaller dosage. In addition, they are obviously easier to handle than manures. Inorganic fertilizers often contain high percentages of the major nutrients and are applied on a pounds-per-acre basis. A typical citrus orchard may apply 200 pounds of urea per acre (that’s about 100 pounds of nitrogen).

On the other hand, organic fertilizers, including such products as manures and crop residues, have relatively low amounts of nutrients and are applied on a tons-per-acre basis. There are some exceptions of course, such as 23 percent phosphorus in bone meal.

Manures are low in nitrogen, phosphorus and potassium (N-P-K). The analysis for chicken mature (dry) is: nitrogen 2-4.5 percent, phosphorus 4.6-6 percent and potassium 1.2-2.4 percent. Even at 4 percent nitrogen, 25 pounds of manure is needed to supply one pound of nitrogen, whereas only 6 pounds of 16-16-16 fertilizer would be needed to supply the same one pound of nitrogen. For backyard gardens, applying 15-50 pounds of manure per 100 square feet is suggested. At the 50-pound rate, 10 tons of manure would be required for one acre.

Organic fertilizers, however, have many benefits other than supplying slow release nutrients — both macro and micro. They include improving the soil structure, water infiltration rate and water holding capacity of the soil. They also act as a food source for many beneficial microorganisms living in the soil.

Applying organic fertilizers can be expensive. Maximize the use of organic materials produced on your own property, for example, yard trimmings and kitchen waste.

The macronutrients are nitrogen, phosphorous, potassium, calcium, magnesium and sulfur. Zinc, iron, manganese, boron, copper, chlorine and molybdenum are the micronutrients.

I just bought some citrus, avocado and mango trees. It was recommended a buy grafted varieties. I’m also looking for some lilikoi vines; do they have to be grafted also?

The lilikoi, or passionfruit vines you buy will most likely be grown from seed.

No grafting or budding is required. You can also start your own from a good piece of tasty fruit. The seeds do not require cleaning, drying or storage, they can be planted immediately after being removed from the fruit.

Propagation of passionfruit can also be accomplished through air layering and cuttings.

A delightful cookbook of a hundred lilikoi recipes was recently compiled by local residents and published by the Larry Czerwonka Co. The book, “Lilikoilicious Cookbook,” can be purchased at Basically Books in downtown Hilo.


Saturday, February 8. I am teaching a class, ‘Vegetables in the Home Garden,” from 10 a.m.-12:30 p.m. Saturday, Feb. 8, at the University of Hawaii at Hilo, UCB 118. Topics include soil preparation, fertilization, transplanting versus direct seeding, the common diseases and insect pests that attack vegetable plants, and which vegetable to plant. Call 974-7664 or register online at There is a fee.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at


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