Outdoor growing nutrients are the modern grower’s most important tool for keeping their soil productive year after year. Knowing how to keep your soil healthy requires an understanding of plants’ nutritional needs, and how your chosen crops impact the soil. Here, we’ve put together all you need to know about outdoor growing nutrients.
What Nutrients do Plants Need?
By weight, plants are only 5% nutritional elements (3). The other 95% is carbon, oxygen, and hydrogen. That 5% of essential nutrition is commonly broken down into primary, secondary, and micronutrients.
The Big Three
Regardless of what you grow, all plants need some of the same nutrients. By far, the most heavily used nutrients for plants are Nitrogen, Phosphorous, and Potassium. This ‘gardening trinity’ is commonly known as NPK. NPK forms the basis of all general-duty fertilizers, and they are listed on the labels by the percentage of overall weight. For instance, a 50 lb. bag of 20-10-10 NPK would contain 10 pounds of Nitrogen, 5 pounds of Phosphorus, and 5 pounds of Potassium.
Nitrogen is responsible for the deep green in the grass and leafy vegetables. It is essential for Chlorophyll production. Phosphorus is needed in large quantities for many fruit-bearing crops. It is also needed for the vigorous development of young roots. Potassium makes the plant hearty and hale, helping it survive stressors such as drought, disease, or temperature variations.
The Secondary Nutrients
Calcium, magnesium, and sulfur are known as secondary nutrients. After the NPK trio, plants use more Sulphur than any other nutrient. Magnesium and calcium, although not needed in as great a volume, must be present in a certain ratio to one another.
Sulfur is used by plants in chlorophyll production and in protein synthesis. It also boasts a plant’s ability to resist disease. Legumes and clovers use it to fix nitrogen.
Plants need calcium for strong cell walls; they need Magnesium for photosynthesis and enzyme production. Balancing the ratio of these two nutrients is important. These two elements are in the same column of the periodic table, and in ion form, have similar bonding properties. Therefore, too much of one leads to not enough absorption of the other. The balance between these two elements is the subject of a great deal of study.
Beyond the primary (NPK) and secondary (Ca, Mg, S) nutrients, ten or so other elements are needed in very small amounts. These micronutrients include copper, zinc, iron, molybdenum, boron, manganese, and chlorine. Plants use them for slightly different purposes, but they generally have a role in either photosynthesis or enzyme production. Accurately identifying deficiencies in micronutrients requires soil testing.
Best Fertilizer for Outdoor Growing
Now that you know about all the nutrients that a plant needs, How do you know what you should use on your crops? When determining your fertilizing needs, you need to consider two main factors: the current state of your soil, and what you plan to grow. Different soil types tend to have certain nutritional deficits and surpluses, and plant families have various needs.
Soil and Nutrients
Before fertilizing, take samples of the soil you are working with. If you are cultivating a large area (such as a yard), take samples from several sections. Although you should use accurate chemical analysis, a physical examination should give you a general sense of what you are working with.
Soils vary widely, from heavy clay to crumbly loam to gritty sand. Your soil’s texture reflects likely nutritional value. Soil with a high clay content tends to be rich in mineral nutrients; sandy soil may have lost some of its nutrients due to rainfall leaching them deeper into the earth.
Another consideration when considering the nutrient quality of your soil is how many seasons it has been producing. Naturally, growing plants take nutrients from the soil; if you know the nutritional needs of the previous crops you can infer which nutrients may be deficient.
If you want a deeper understanding of how to analyze your soil accurately, visit the soil analyst cooperative.
Crops and Nutrients
After analyzing your soil, take a look at what you’re planning to grow. If you use a bed for multiple crops in a season, take all of them in consideration. Every plant has unique nutritional needs, but knowing a few major guidelines can help point you to the best outdoor growing nutrients for your garden.
If you are after a crop of deep, leafy greens, you need nitrogen-rich fertilizer. Photosynthesis relies heavily on nitrogen, so deep green leaves means your plants have access to plenty of nitrogen. Don’t overdo it though. Excess nitrogen can lead to leaf overgrowth at the expense of root development.
For juicy fruit and vibrant blooms, your plants need fertilizer high in phosphorus. It is also a key component of root development. Gardeners commonly add phosphorus during the flowering stage. Too much phosphorus is uncommon, but it may be the hidden cause of micronutrient deficiencies in zinc, iron, and copper (Table 1-4).
Best Organic Nutrients for Soil
Organic soil nutrients are too often overlooked, especially when growing with pre-packaged soil. Many veteran growers know a great deal about plants and mineral nutrients, but not much about the bacteria and fungi that aid plants in capturing and absorbing what they need. These microorganisms subsist on the contents of organic soil.
What is an Organic Nutrient?
Not to be confused with labeling food ‘organic’ if it is non-GMO, organic plant nutrients are the chemical components of decaying organic matter. Organic nutrients have two-fold benefits: they feed the plant directly, and they provide a growth medium for the good microorganisms.
Organic matter can include lawn clippings, compost, leaf mold, manure, and ash. Once these components decompose, and their molecules become the building blocks of next season’s crops. If you grow outdoors, you may not have to add organic fertilizer to your soil. But if you grow in pots or hydroponically, you will need plant food specially formulated with water-soluble organic materials
An excellent summary of the value of using organic matter as plant nutrients by Soil Science Specialist David Crouse: “Adding organic matter is a more economically feasible alternative for improving the soil. Adding organic matter does not change a soil’s texture—the percentage of sand, silt, and clay in the soil—but adding organic matter will alter soil structure by increasing the pore space and improving drainage.”
Best Fertilizer for Outdoor Grow
At this point, you should understand the basics of plant nutrients. You’ve tested your soil and examined its consistency. You’ve anticipated your chosen crop’s nutritional needs. Now take that knowledge and find the plant fertilizer with exactly what you need to make your plant grow. Here’s to healthy growing!