1. Q. I would value your opinion about certain "miracle products"--soil conditioners--being sold in this area? Are they worthwhile?
A. Home gardeners are bombarded with advertisements for a plethora of products billed as soil conditioners, stimulants, inoculants, etc. The common claims made are that these products either (a) contain beneficial soil microorganisms, (b) stimulate the existing microflora into greater activity, � provide certain micronutrients or (d) all the above. The advertised advantages include higher yield, improved soil structure and better fertilizer utilization. To my knowledge, there is no credible evidence whatever that any of these products actually deliver measurable results. The exceptions are inoculants containing nodulating bacteria which are proven to improve the growth of certain legumes.
Some general conclusions can be drawn on the efficacy of these products based on these facts:
(1) Agricultural soils commonly contain 2,000 to 4,000 pounds of microorganisms per acre, including hundreds of different kinds of microbes. At the recommended rates of soil conditioner/stimulator application, the maximum mass of organisms added would increase the microbial content of a typical soil less than 0.2 per cent.
(2) The survival and multiplication of microorganisms in the soil are controlled by environmental factors such as organic matter content and composition, temperature, water content, nitrogen availability, etc. If these factors are favorable, microbial activity will abound. If unfavorable, no chemical stimulant will be able to increase activity.
(3) Micronutrients such as iron, zinc and manganese are required for plant growth, but yield increases due to their application will only occur when a deficiency exists. Most soil conditioners contain such low levels of micronutrients that doses far in excess of label direction recommendations would be required to correct a deficiency.
It is clear that any product that claims to increase microbial population or activity, 'unlock' unavailable nutrients or 'condition' the soil, when applied at low rates, is suspect. In most cases, an equal amount of manure could be more beneficial and considerably less expensive.
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