Summer has gone and the autumn sun isn’t warming up the soil enough for my outdoor gardens and container plants to thrive much longer. The annuals are pretty much finished, and the perennials are beginning to go to sleep. As I move some of my plants indoors for the winter, this is the time to take stock of how healthy they are, as well as the ones that will remain outside. I look for the usual suspects of bug infestations and diseases. Spotting nutrient deficiencies is what I am keen on this time of year. It will help me to remedy the nutrients needed and to adjust the PH of my soil for the spring.
What are the Nutrients Plants Need to Thrive?
All plants need the proper balance of nutrients just like all other living things to thrive. Plants rely on essential mineral nutrients from the soil absorbed through their roots. They actually make their own food or energy through the process of photosynthesis. Healthy soil, proper watering, adequate sunlight are all things that contribute to a plant’s ability to nourish itself.
A healthy soil is composed of a mixture of sand, silt, clay, and other organic material. The proper proportions of each soil component will assure that the inherent nutrients will not be washed away with watering or rain and the PH level of the soil will be ideal. If a soil is depleted of nutrients, they can be added in the form of commercial fertilizers. A more natural approach is to add organic materials that are available in local markets and garden supply centers. Rutgers University has compiled extensive research on types of fertilizers and organic materials that can be added to soil to replenish nutrients. This information can be found at http://mgofmc.org/docs/nutrientdeficiency.pdf. In this post we will focus on the organic materials suitable for home gardens and potted plants.
Plant nutrients are divided into two categories, macronutrients and micronutrients. Macronutrients are the primary elements that plants metabolize for nutrition. These include minerals, carbon, hydrogen, and oxygen. Micronutrients are considered as secondary mineral elements that are utilized less than the primary nutrients. There are 12 most common essential mineral nutrients.
Macronutrient minerals:
- Calcium (Ca)
- Magnesium (Mg)
- Nitrogen (N)
- Phosphorus (P
- Potassium (K)
- Sulfur (S)
Micronutrient minerals:
- Boron (B)
- Copper (Cu)
- Iron (Fe)
- Manganese (Mn)
- Molybdenum (Mo
- Zinc (Zn)
Identifying Nutrient Deficiencies
According to University of Arizona Cooperative Extension, too little or too much of any nutrient can be toxic to plants (http://extension.arizona.edu/sites/extension.arizona.edu/files/pubs/az1106.pdf). There are ways to identify nutrient deficiencies. The first is visual observation, which is ideal for the home gardener. The second is by soil testing done either through a laboratory or a home test kit. Soil testing is a bit more scientific and requires some meticulous watering and soil sampling over a 12 hour period. For the purposes of our needs we will explore the visual diagnosis method in more depth. Keep in mind that the characteristics of nutrient deficiencies can overlap. It is a good idea to research what a healthy plant is supposed to look like for comparison.
Macronutrient Properties, Deficiencies, & Remedies
Calcium
Calcium plays a role in leaf and root growth. It is vital to the hardiness of plants. Calcium promotes the metabolism of nitrogen.
A calcium deficiency is characterized by misshapen and lighter colored leaves at new growth.
Calcium can be added to soil in the form of crushed egg or oyster shells, ashes from wood, and bone meal.
Magnesium
Magnesium is needed for photosynthesis. It plays a key role in the absorption and utilization of the other nutrients, especially phosphorus and iron.
A magnesium deficiency is recognized when the edges of leaves turn yellow or brown while the veins remain green. Leaves may eventually die.
There are no known organic sources of magnesium to add to soils. The best source is in the form of magnesium sulfate, which is basically Epsom salts.
Nitrogen
Nitrogen is used by microorganisms in soil to decompose organic matter. It is essential for the chlorophyll that gives leaves there green color. Nitrogen is necessary for photosynthesis.
A deficiency is indicated when older leaves turn yellow and newer leaves have stunted growth.
Nitrogen can be added to soil in the form dried blood meal, used coffee grounds, or soybean meal.
Phosphorus
Phosphorus is required for root formation, flowering, and seed production. It improves the quality of edible plants. It is well suited to soils with a mid-range PH. It plays a key role in photosynthesis.
Phosphorus deficiency is characterized by the tips of new leaves drying up and older leaves turning dark green, red, or purple. Flowering may be less frequent.
Phosphorus can be added to soil in the form of bone meal or manure.
Potassium
Potassium is what gives plants their vitality, hardiness, and disease resistance. It is important for fruit formation and protein synthesis.
A potassium deficiency is recognized by spotty wilting leaves.
Potassium can be added in the form of wood ashes or dried and ground sea vegetables.
Sulfur
Sulfur helps to maintain the dark green color of leaves. It is important for plant respiration, root growth, and seed production. Sulfur helps with the development of vitamins and enzymes.
A sulfur deficiency is seen as the entire plant begins to turn yellow, starting with new growth first and followed by older leaves.
Sulfur can be added to soils in the form of plant residues.
Micronutrient Properties, Deficiencies, & Remedies
Boron
Boron promotes the production and quality of fruits and vegetables. It is necessary for cross pollination, and is required for the utilization of calcium.
A Boron deficiency is characterized by buds dying off prematurely. New growth leaves are paler green and may be misshapen. Flowering may be reduced.
Boron can be added to soil in the form of fresh green manure or plant residues.
Copper
Copper is required for photosynthesis and plant respiration. It intensifies plant color and enhances flavor in fruits and vegetables.
A copper deficiency appears as leaves being stunted and darker green in color. Stems and leaves may be twisted.
There are no known organic sources of copper to add to soils. The best source is in the form of copper sulfate.
Iron
Iron is required for chlorophyll formation and maintenance. It is a carrier of oxygen.
An iron deficiency is apparent when new leaves begin to turn yellow between the green veins. Older leaves will tend to remain green.
Iron can be added to soil in the form of iron chelates.
Manganese
Manganese is required for photosynthesis and chlorophyll production. It is needed for the absorption of calcium and phosphorus.
A manganese deficiency is characterized by new growth leaves turning yellow or white between the green veins. Plant growth may be stunted. Necrotic spots or patches may appear.
Manganese can be added to soils in the form of manganese chelate.
Molybdenum
Molybdenum is required for nitrogen metabolism. It is advantageous to the production of legumes.
A molybdenum deficiency appears as yellowing of the more mature leaves. New leaves remain green. Leaves may become twisted.
There are no known organic sources of molybdenum to add to soils. The best reported source is in the form of sodium molybdate.
Zinc
Zinc is necessary for the production of seeds and plant starches. It is plays a key role in the production of chlorophyll.
A zinc deficiency is evident when terminal leaves become distorted and yellow or white between veins. Newer leaves may be reduced in size and older leaves may have spots.
Zinc can be added to soils in the form of manure, sewage sludge, or zinc chelate.
Fertilizing your Soil
Now that you have diagnosed your nutrient deficiency and soil PH, either visually or through testing, the next step is to adjust the nutrients in your soil. Putting together an ideal mix can be an arduous task, unless you really enjoy the chemistry involved. Mother Earth News has detailed instructions on how to make your own Complete Organic Fertilizer (http://www.motherearthnews.com/organic-gardening/garden-fertilizer-zmaz06jjzraw?pageid=1#PageContent1).
There are pre-mixed commercial fertilizers and composts available to enrich your soil. Some of these products are organic and include the materials listed in each nutrient description above. You might also consider taking your nutrient deficiency notes to your local garden center and ask them to make a customized mix for you. I have had success with this. Though, not all centers are expertly equipped to do that.
Timing is important. Outdoor gardens can benefit from fertilization in both the autumn and early spring. Indoor plants tend to “rest” in winter and don’t necessarily need extra nutrition or watering as winter approaches. Of course, you need to take into consideration your particular climate and seasonal changes.
Conclusion
Identifying and correcting nutrient deficiencies in your garden and potted plant soils is an ongoing process. It comes with a learning curve. By trial and error, you will begin to better understand what your soil needs to support healthy and productive plant life. In addition to just observing your plants year-round, I recommend making detailed notes of your observations twice a year in spring and autumn. A garden journal is a good way to keep track. In that journal, include any nutrient-dense formulas you have added to your soil and how the plants have reacted over a period of 1 to 3 months. This will help you to make informed adjustments seasonally.
Plants need TLC. Though they can’t speak, they are pretty clever at letting us know what they need to thrive. Nurture them. Mostly, have fun with your gardening.