How to Make Garden Fertilizer
Your garden needs nutrient rich soil to help your plants thrive. But growing in the same space each year can deplete certain vital nutrients over time. You need to fertilize your garden to keep in growing strong year after year. But buying fertilizer at the garden store can cost a lot. Luckily you can make your own fertilizer for your garden. Check out my three tips on how to make garden fertilizer.
Fertilizer From Animals
The easiest way to make garden fertilizer is to use animal manure. Animal manure is full of nitrogen and other nutrients that your garden needs. You can use some manure, like rabbit droppings, without any processing. If you raise rabbits, you can put their droppings directly in your garden. Other types of manure should be allowed to break down and compost before you can use it for your plants. Poultry manure is especially high in ammonia, which can actually burn your plants if you use it before it is aged. Livestock, like cows, horses, sheep, and goats can produce large amounts of manure. If you compost it properly, it can provide a rich source of fertilizer for your garden.
You can also make liquid fertilizer from animal manure. Basically you soak the manure in a bucket or barrel of water. Then use the nutrient-filled “manure tea” to water your plants. It can make a small amount of manure go farther in fertilizing. You also eliminate the composting step, so you get your fertilizer faster. You can also spray liquid fertilizer on the soil to provide nutrients after your plants are in place without disturbing their roots. If you cover your manure tea bucket and use it within a few days, you can prevent any odor or insect issues.
Fertilizer From Plants
Another easy way to make garden fertilizer is by composting plant matter. This can be kitchen scraps, coffee grounds, grass clippings, weeds, leaves, woodchips, sawdust, even shredded paper. The keys to making good compost is having enough oxygen and moisture and getting the carbon and nitrogen balance right. You can introduce oxygen by turning your compost and making sure the plant pieces are small. The more you turn your compost, the faster it will break down.
The compost pile should be the consistency of a wrung out sponge, not too wet or too dry. Covering the pile can help to keep moisture in during dry periods and prevent water logging in wet areas. Check the moisture levels often and add water if needed.
Getting the carbon and nitrogen balance right can be a little tricky. You can think of the carbon as the “browns” or they dry items like leaves or wood chips. The nitrogen are the “greens” or wet items like kitchen scraps or fresh grass clippings. You’re looking for about a 25 to 1 carbon to nitrogen ratio. This is almost exactly the ratio you would find in fresh weeds. That’s one reason that chop-and-drop fertilizer where you grow a cover crop, or chop the weeds in your bed and incorporate them directly into the soil can work well. Just make sure to chop before the weeds have gone to seed.
Just like “manure tea”, you can make liquid fertilizer from “compost tea”. Soaking a scoop of compost in a bucket and watering your plants with the tea can help your compost go farther. Depending on how “finished” your compost is, you may need to let your tea soak for a while to get all the nutrients out.
Chemical Fertilizers
If you don’t have access to enough animal manure or plant matter to compost, you can make garden fertilizer from various chemicals or soil additives. Your plants generally need nitrogen (N), phosphorous (P), and potassium (K) in significant quantities to grow well. In store-bought fertilizer, the bag will often advertise the ratio of the three main components like NPK 10-10-10 or 1-2-2 or whatever their preferred formula is. Your plants can also benefit from micronutrients and like calcium and magnesium.
Different soil additives have the different nutrients and minerals in different quantities. Nitrogen-rich sources include blood meal, fish meal, and feather meal. Phosphorous can be found in bone meal or rock phosphates. Potassium comes in wood ashes and sulfate of potash but be careful as these can be strong and mess with the acidity of your soil. Calcium comes in various kinds of lime or crushed oyster shells. Magnesium is also usually provided in salt form, and it’s easy to over do it, so be judicious unless you know through soil testing that you have a significant magnesium deficiency.
There is no definitive “perfect” ratio of the different soil nutrients, and different plants will need different amounts of nutrients for optimal growth. The commercial bags use ratios of weight, not volume, so measuring out a cup of blood meal, a cup of bone meal, and a cup of wood ashes doesn’t necessarily give you a 1-1-1 N-P-K fertilizer. You would need to check the relative percentages of each nutrient on the bag and weigh the fertilizers out to make sure your ratios are right.
The math can get complicated fast, so mixing your own chemical fertilizers may not be for everyone. Using a balanced fertilizer like 5-5-5 NPK can be a first step if you don’t know which nutrients your soil needs. But getting your soil tested and knowing what nutrients are low is the best way to make a custom mix that will help your garden thrive.
Not sure if your soil needs fertilizer? Check out my 5 Keys to Healthy Soil to step through the process of diagnosing soil issues. Enjoy!
Want more info on how to keep your plants thriving? Check out my Mission Healthy Plants mini course. It has everything you need to know to keep your plants healthy from seed to harvest.
