Free nitrogen for plants
In most gardens, nitrogen is nearly always the nutrient plants need. By virtue of the nitrogen cycle, microbes in the soil can decompose organic nitrogen from organic matter and crop residues and convert to nitrate and ammonium. This then becomes a plant-usable form of nitrogen. Very approximately, 60-80lbs of nitrogen is formed in the soil per acre per year this way. More ammonium is produced in warmer weather – just when the plants need it. So your plants will naturally be getting a good annual application of nitrogen just when they need it.
Blood, fish and bone
This waste product is often quoted as a great organic dressing. Bear in mind it needs acidic soil for the bone part to work, so if your soil has a pH above 7, then the bonemeal is locked up and useless. Very basically, the blood supplies the nitrogen (for four to six weeks), the fish the potassium and the bones the phosphate, supposedly in slow-release balanced format. If the fish part is supplied as an emulsion then it is a fast release, if it’s fish meal it is slowish. On my alkaline soil, this expensive additive would not add much benefit to my soil or plants.
Mycorrhiza
It has become popular to add a mix of beneficial fungi, especially with roses, to help prevent specific replant disease. Some studies in the States on these additives imply many of the supposed organisms are dead and much of what should be there is not. In Germany, Professor Traud Winkelmann from Hannover University says the results are variable, some positive, some even negative.
Homemade compost
This is highly popular and for good reason. It’s easy to make, whether you just have a pile on the ground or have ordered several large heaps. We all have the makings of it, so it’s free and highly valuable to the soil. I don’t turn mine. Some experiments were done comparing temperatures of turned heaps and non-turned heaps. Turned heaps sometimes got a degree or two warmer than unturned heaps immediately after turning, but this made no difference to how well the compost was formed. After a year, turned and unturned heaps both produced the same quantities of pretty much indistinguishable compost.
Everything you fling on the pile will be full of microbes; these will rot down and create a great inoculant that you can add to your soil.
Dr. Thomas Hughes is a UK-based scientist and science communicator who makes complex topics accessible to readers. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
