Richard

For many soils and fruiting plants, mulch is necessary to provide an environment for effective uptake of micronutrients -- unless perhaps you are delivering them by foliar spray.



There is a long history in my family of using seaweed extract as a summer foliar spray for this very purpose. When I built my garden here in San Diego, I purchased a fertigator so that I could neutralize my alkaline water and provide micronutrients as well. Until recently, all of my major mineral components have been supplied by granulars and meals (e.g., alfalfa). Now that my fertilizing needs are equivalent to about 100 fruit trees, I'm looking for something less labor intensive -- hence the search for inexpensive water soluble fertilizers.

I have long known two basic facts about the requirements for a mature semi-dwarf fruit tree (or its equivalent, e.g., 2 mature tomato shrubs or berry bushes): it needs 1 pound of available Nitrogen per year - and heavens not all at once, and it needs a useable source of potash, about 1.5 pounds per year. Until recently I had acheived this without questioning the phosphorus requirement, but knowing that some subtropicals do not tolerate high phosphorus. So earlier this year inkcube pointed out that (1) the P cation moves very slowly through the soil, (2) plants are slow in P uptake, and (3) post-harvest analysis of banana fruit shows a P to K ratio of about 1:24. The good news is that bananas also ignore surplus P, so over doing it doesn't hurt the plant -- but rather wastes your money and eventually pollutes the waterways and oceans with excess phosphorus. In fact, I wonder if all these high-phosphorus fertilizers are just a way for chemical companies to sell their hazardous phosphorus waste instead of paying for its disposal.

Anyway, I concluded that the "ideal" N-P-K for bananas would be 16-1-24, and then went off to read the publications from various agricultural Extension resources about minerals lost in the harvests and pruning of other fruits. It turns out that an N to P ratio of about 4 to 1 is plenty. This is interesting, because that ratio is low enough for most phosphorus sensitive plants as well. So when Chong came across a 20-5-30 water soluble fertilizer, I started thinking differently about my fertlizer choices in the past.

Well, if you read this long winded explanation and didn't get bored, you earned another garden geek gold star for the week.

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