The key to growing fresh and healthy fruits and vegetables, abundant flowers, and gorgeous ornamental plants lies in the fertility of the soil. In terrace gardening it becomes all the more important to ensure fertility since the soil is limited to containers and its essential nutrients are depleted quickly. In this post, you can learn about the different types of organic fertilizers available in the market, the benefits of using the different types of fertilizers and tips on using organic fertilizers for your plants.
There are plenty of chemical fertilizers available in the market that provide quick solutions for soil replenishment. But over a period of time, the chemicals pollute the groundwater, make the soil toxic, kill off the soil microbes and make the soil unusable in the long run.
Organic fertilizers on the other hand release nutrients slowly into the soil, providing a steady flow of nourishment for plants; they increase the soil’s water and nutrient holding capacity, promote the growth of healthy microbes and micro-organisms and improves the condition of the soil over time.
So What Are Organic Fertilizers?
Organic fertilizers comprise of ingredients that are naturally occurring in the environment, from plant or animal matter. They can be animal waste or manure, and vegetable waste or compost, and naturally occurring minerals like peat and limestone.
Plant Based Fertilizers
Plant-based fertilizers usually do a great job of conditioning the soil than providing actual nutrients to the plants. Examples of plant based fertilizers include alfalfa meal, cottonseed meal, kelp or seaweed or compost tea and compost. These fertilizers add drainage and increase the moisture retention capacity of the soil.
Alfalfa meal is derived from alfalfa plants. It is a rich source of nitrogen and potassium but also contains minerals and growth stimulants. Roses, in particular, benefit from this fertilizer. You can also add this to your compost pile.
Compost adds organic matter to the soil and helps it nourishing the soil.
Kelp/seaweed is a sea plant that adds valuable micronutrients, growth hormones, and vitamins that increases the plant yield and reduces drought stress. Available in solid and liquid forms, it can be applied to the soil or as a foliar spray.
Animal Based Fertilizers
Animal based fertilizers include manure, bone meal or blood meal, and fish byproducts. They add plenty of nitrogen to the soil and are extremely helpful for strong growth of the plants.
- Blood meal is a byproduct of the meat-packing industry and is usually available steamed and dried. It is high in phosphorous. It should be applied just before planting and used sparingly.
- Bone meal is finely ground bones of cattle. It is a great source of calcium and phosphorous. It promotes a strong root system and flowering.
- Fish byproducts include liquid fish emulsion that is a 5-2-2 fertilizer that stimulates growth in young plants and seedlings and fish meal that is high in nitrogen and phosphorus.
- Bird and animal manure is a good source of microorganisms. It should be used when it is well aged or composted.
- Vermicompost is basically worm poo or castings from earthworms. It is an excellent natural source of nitrogen that inoculates the soil with beneficial fungi & microbes.
Mineral Based Fertilizers
Mineral-based fertilizers add nutrients to the soil and include calcium, and Epsom salt.
Epsom salt contains magnesium (10 percent) and sulfur (13 percent) and is a fast-acting fertilizer. It is available in a granular form or it can be dissolved in water and sprayed on leaves as a foliar spray. Tomatoes, peppers, and roses love this stuff!
Key Nutrients Needed by Plants
All plants basically need 3 key nutrients:
Macronutrients include nitrogen, phosphorus and potassium. Plants need these in large quantities in the soil.
- Nitrogen: It is needed for for plant growth, leaf development and is responsible for making plants lush green.
- Phosphorous: This is required for root growth and for the creation of fruit, seeds and flowers.
- Potassium: Also needed for root development and to provide resistance to drought and disease.
Secondary nutrients include oxygen, carbon, sulfur, calcium and magnesium. These are often available in the soil and air.
Micronutrients include iron, manganese, zinc, chlorine, boron, copper and nickel. They are needed only in very small quantities.
When you shop for fertilizers, it can be very confusing with the labels displaying all sorts of numbers and information. This is further complicated by the fact that different plants have individual nutrient requirements.
Usually, you will find 3 prominent numbers on a fertilizer pack referred to as NPK. It tells you the percentage of available macronutrients by weight in the package. NPK stands for:
- N stands for Nitrogen and is the first number on the label.
- P stands for Phosphorous and is the second number on the label.
- K stands for Potassium and is the third number on the label.
A 100 kg bag that is marked 10-10-10 contains 10kg each of nitrogen, phosphorous and potassium. If a 10 kg bag contains a label 16-4-8, it contains 6 kgs of nitrogen, 4 kgs of phosphorus and .8 kg of potassium. That is 16% of 10 = 6; 4% of 10=4 and 8% of 10=.8.
The rest of the bags content is inert material that helps distribute the fertilizer evenly and prevent chemical burn. There may also be some secondary nutrients or micronutrients in the remaining matter.
So when you buy an organic fertilizer with a label, you must read the percentage of macronutrients available in the pack, check if your plant needs an extra dose of N, P or K and accordingly choose the label.
Types of Organic Fertilizers
Typically, fertilizers are available in liquid, granular and solid form.
Liquid fertilizers are fast-acting fertilizers. Plants absorb them quickly into their vascular systems through the leaves or roots. They are usually milder and need to be applied every 2-3 weeks. This type of fertilizer is usually available as a concentrated solution. Ensure that you mix them with an appropriate quantity of water before applying. Liquid fertilizers work very well for container plants and are especially effective for vegetable plants that an extra boost during the growing season. Liquid seaweed and compost tea are two examples of organic liquid fertilizers.
Tips to Apply Liquid Fertilizers
- In the case of flowering and fruiting plants, you must foliar spray (spray directly on the leaves) during critical periods such as right after transplanting or during fruit production or in periods of drought or extreme temperatures. For leafy crops, I suggest a biweekly spray.
- When using liquid fertilizers, always follow the label instructions for proper dilution and application.
- The best times to spray are early in the morning or early in the evening. That’s when the liquids will be absorbed most quickly and won’t burn the foliage.
- Avoid spraying liquid fertilizers on a day when rain is forecast or when the temperatures are extreme.
- Spray until the liquid drips off the leaves. Pay particular attention to the undersides of the leaves where the pores are likely to be open and receptive to absorption.
- You can also pour liquid fertilizers around the root area of the plant.
Solid or Granular fertilizers
Solid or granular fertilizers usually take longer to dissolve in the soil and must be worked into the soil or sprinkled around the plant base. They are usually slow-release fertilizers or water-insoluble nitrogen (WIN) fertilizers that must be watered and waited upon to see the results. The microorganisms in the soil break down the nitrogen and convert them into nitrate or ammonium which are then absorbed by plants.
Tips to Apply Dry Fertilizers
- Apply sparingly, usually once or twice during the growing season to strengthen crops and give them a boost.
- You can rake the fertilizer onto the top soil or mix it with some fresh soil and add it to the top layer of the soil. After applying the fertilizer, lightly water the area.
- When potting a new plant, add a small amount to the base of the hole.
You should now have a fair bit of idea about the different types of organic fertiizers used in organic gardening. I hope this will help you make an informed decision when it comes to using them in your garden.
Remember, you don’t necessarily have to buy ready-made organic fertilizers from a nursery or online store. After all, you can never be 100% sure that they are organic as they claim to be. You can make use of common household items to create your own fertilizer mix. Keeping in mind your plants nutritional requirements, you can prepare a custom fertilizer solution for each plant or a one-complete-solution that will work on all plants.