Many vegetarians, vegans, and just plain healthy eaters like myself want to opt out of agricultural systems that are cruel to animals and/or hazardous to the environment. I have used animal-based organic fertilisers for years, and while I’ve been happy with their performance, their origins have been a sticking point. Most organic fertilisers use animal-based ingredients made from bone, blood, feathers, or manure that originate in the confined animal industry. Hence my search for plant-based fertilisers or soil amendments that work as manure alternatives.
Using Plant-Based Fertilisers
Before going further, it’s important to understand that when you use grain meals or other plant-based fertilisers, you are feeding soil microbes, which will transform that food into nutrients for plants. Nutrient conversion will be fast and sure when the soil is warm and damp, with less activity in cold or dry soil. Like other organic soil amendments, plant-based fertilisers work best in biologically active soil that is regularly enriched with compost, cover crops and decomposing mulches.
Cover Cropping with Alfalfa Pellets
I cover crop small areas of my garden when I can, but green manuring is the soil-building technique that most often eludes me in my intensive vegetable garden. This is where alfalfa pellets come in. Sold as a food supplement for horses, goats, and other ruminants, alfalfa pellets contain enough nitrogen to get them rotting fast when they are mixed into the soil. Moisture makes alfalfa pellets triple in size, so the result of adding them to soil is similar to turning under a lush green cover crop. The nutrients in alfalfa pellets are released slowly, over a period of three years, so there is little risk of burning plant roots. Some gardeners mix alfalfa pellets with water and use the green slurry as mulch.
Shop for alfalfa pellets at a feed store that sells horse and goat feed. They are quite affordable! A fifty pound (22.5kg) bag that will last me a year cost only US$20 (about AUD$30), and the only storage challenge is keeping the pellets dry.
Fertilising with Chicken Feed
Last year we bought a cheap bag of feed that my chickens refused to eat, so I decided to try fertilising with chicken feed. The label revealed a combination of soybean and grain meals that computed out to about 6 percent nitrogen, so I figured why not? I dug a generous scattering of pellets into the soil, waited a rainy week, and then planted tomatoes and peppers. Maybe it was luck, but the plants grew beautifully with no signs of nutrient stress. This year I’m looking forward to repeating my success.
A word to the wise: For the first week or so after chicken feed or other rich plant meals are mixed into soil, they explode with biological activity that includes the release of ammonia, which can be lethal to germinating seeds or tender plant roots. This is why corn gluten works as a natural pre-emergent herbicide.
You can prevent problems by adding pellets or plant meals to soil as early as possible, preferably two to three weeks before planting. How fast the meals or pellets decompose depends on moisture and temperature, though in my experience things move along quickly, with soy-based pellets disappearing in about a week.
Grain meals have long been recommended as plant-based fertilisers, but organic soybean meal or even cornmeal can be difficult to find. Organic animal feeds provide a cheap and handy supply, though it’s important to read the label to ensure there are no unwanted added ingredients such as fats or oils. If you’re a veganic gardening purist, watch out for fish meal as an ingredient, which is added to some chicken and rabbit feeds to raise their protein content.
Plant-Based Liquid Fertilisers
I have always felt squeamish about making liquid fertilisers from compost or manure because of the likely presence nasty bacteria, but I feel safe and confident fermenting plant materials and using the liquid as a plant food. It’s a simple procedure. Mix fresh green grass clippings, alfalfa pellets, chicken feed pellets or another organic grain with water, let the mess ferment for three days, and then pour off the liquid. Because the exact nutrient and salt content of the liquid is unknown, I dilute it with an equal amount of water before using it to feed plants.