Great thread Uncle Ben.
I thought you might like this from Maximum Yield magazine. If this article wasn't written about and for Cannabis growers, well than I will eat my hat.
So, now back to the question: “Who has determined the nutrient values and ratios in your crop feeding program?” All right, well most folks are likely to say “the manufacturer.” Okay, so the manufacturer determined the nutrient ratios. That beckons the question of how they were able to determine what concentrations and ratios of plant nutrient elements to provide for your particular crop and at what times in the vegetative and bloom phases of growth. Well from there you can only guess, unless you have information that says otherwise.
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Due to archaic field crop research crossed over into nutrient formulations intended for modern high producing indoor crops, there are some really huge misconceptions about what is optimal for nutrient ratios in the bloom phase for indoor crops grown in artificial environments. The simplest way to illustrate this fact is to look at one of the most popular types of products in the hydroponics industry, and that’s the “bloom booster.”
The majority of bloom boosters contain very high levels of phosphorous and moderate to lower amounts of potassium. They may also contain other macro and micro elements including magnesium, sulfur and iron. Growers begin to apply these types of products through the early bloom phase and late into flowering prior to “flushing” the crop before harvest. There seems to be a general consensus that the modern indoor containerized (or “systemized,” if you prefer) plant in the bloom phase needs abundant amounts of phosphorous relative to other nutrients. Well the truth is that they do not, because:
Phosphorous is highly available to containerized or systemized plants grown indoors relative to outdoor conditions where it is quickly leeched away from the root zone via mass flow.
When examining analytical reports charting the nutrient profile of a high yielding indoor crop at harvest (plant tissue analysis) it becomes clear that even in a variety of strains within the same plant type, that the plant requires nearly five times more each nitrogen and potassium relative to phosphorous.
For example, if the plants elemental profile at harvest time was analyzed to reveal that healthy yields consisted primarily of nitrogen, potassium and calcium relative to phosphorous, why then are growers applying so much phosphorous (relative to other nutrient elements) in the bloom phase, and more importantly, what effect is this over abundance of phosphorous having on crops?
To answer the first part of the question, as indoor growers we are applying too much phosphorous because the recommendations for applications and formulations have been based on outdoor field agriculture practices, which simply don’t apply directly to indoor gardens. In nature the soil is very deep, and roots do not occupy the entire body of soil as they do in containers, beds or systems found with indoor gardens. Phosphorous leeches from the root zone in natural soils quickly, washing away from the contact zone with plant roots, as it drains with water further into the depths of the earth. To ensure a healthy supply of phosphorous, outdoor conventional field agricultural growers do a sort of “over-application” of phosphorous, because it has been determined that much of it will be quickly leeched away from the plant roots; what remains at any given time can be taken up by the crop. From this, we can learn that excessive “P” values in our N-P-Ks are not necessary for indoor growers, where phosphorous maintains a high level of contact within the root zone of plants grown in artificial soils and in containers, beds and systems commonly found with intensive indoor growing environments.
