What about fertilizers?- Part 2: There are many organic fertilizers on the market these days and it can be hard to know whether you need any of them or what each is for. This week and next, we’re going to look at the most common organic fertilizers. First, we’ll look at nitrogen fertilizers. Nitrogen is one of the “big 3” plant nutrients and it is the most easily lost. There are 2 primarily nitrogen fertilizers that are widely available – blood meal and fish emulsion. We’ll also look at some non-commercial sources of nitrogen.
Blood meal is dehydrated blood from animal processing plants and it is usually purchased as a powder. It contains significant amounts of nitrogen and many trace minerals and it breaks down over time in the garden. Its down side is that it is an industrial by product and so can contain very tiny amounts of anything that would be in a slaughterhouse cow’s blood stream. Blood meal is applied in the early spring and can be added to planting holes for high nitrogen feeding transplants like cabbage, broccoli and cauliflower to give them a boost.
Fish Emulsion is pureed fish bits from a fish processing plant (think canned tuna and salmon). It contains both high levels of nitrogen and many trace elements. It is much more quickly available to plants compared to blood meal. It is generally a liquid that gets mixed with water and used as a spray-on fertilizer. Depending on the fish it is made from, it can have the same issues as blood meal with trace amounts of antibiotics or other industrial additives. Fish emulsion is often used as a foliar spray (spray on the leaves of plants) as well as a liquid fertilizer during the growing season. It leaches out of the soil more quickly than blood meal, so it must be reapplied during the growing season.
If you’re not interested in commercial organic nitrogen fertilizers, there are 2 other readily available sources. The first is fresh grass clippings. You can top dress your beds (mulch them) with several inches of freshly cut grass clippings to help smother weeds. In the process, the soil micro-life will break down the nitrogen in the grass and make it available to your plants. Just be careful that the clippings don’t have herbicide, fungicide or pesticide residue on them. The second readily available source of nitrogen is urea. Yes, that would be urine. Studies have shown that tomatoes watered with a 10:1 (10 parts water to 1 part urine) mix grow at about twice the rate of plants without. Human urine has lots of very readily absorbed nitrogen as well as a host of other minerals. This is a fertilizer best used fresh as the nitrogen will quickly change into a smellier form after about 24 hours. Interestingly enough, one person produces about enough urine in a year to fertilize the farm ground that produces their food. Funny that, don’t you think? If you’re not game for collecting your own urine, you can also buy dried animal urine (labeled urea) in some garden centers. This is also an industrial by-product similar to blood meal.
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