Fertilizers
On This Page:
- Plant Nutrition
- Primary & Secondary Nutrients
- Slow Release or Liquid Fertilizer?
- Organic Fertilizers & Amendments
- Make Your Own Fertilizer Recipe
Like all living things, plants need proper nutrition
to grow. There are 19 nutrients considered essential for plant growth.
Carbon, hydrogen and oxygen are supplied by air and water. Plant roots
absorb the remaining 16 from the surrounding soil. While some soils
may already contain these nutrients, they may not be in a form available
for plant growth. The
benefits of regular fertilizer application are: Vigorous growth,
vibrant color, bigger blooms and healthier plants which are more
resistant to droughts, insects and diseases.
Plant Nutrition
The mineral nutrients are divided into three groups based on their relative abundance in plants:
- Primary Nutrients (or Major Nutrients)
- Secondary Nutrients (or Minor Nutrients)
- Trace Nutrients (or Micronutrients)
Although the major nutrients are needed in the greates quantities, a deficiency of any one nutrient can prevent growth or make plants more susceptible towards disease.
Reading A Label
Whether in a bag or a box, organic or not, most all fertilizers have three analysis numbers listed somewhere on the package, e.g. 5-3-3. These are the percentages (by weight) of the Primary Nutrients: Nitrogen, Phosphorus and Potassium, in that order. You will hear this called the N-P-K ratio. The letters represent their listing in the periodic table.
Where Did the Phosphorus Go?
You may have noticed, when looking at fertilizer products recently, that Phosphorus is slowing disappearing from the store shelves. Why is this? The uptake of phosphorus by plants is highly dependent upon the pH of the soil. Soil pH should be neutral for phosphorus to be taken up efficiently by plant roots. Over the years fertilizer products have included varying amounts of phosphorus (i.e., "Bloom Booster" fertilizers with very high percentages of phosphorus). It has been determined that we have been adding too much phosphorus to our soils. What we should have been doing is adjusting our soil pH so that the plants can take up the phosphorus which occurs naturally. Phosphorus is expensive to produce, and in excess, is harmful to our environment (Canada has already banned it, the U.S. may soon follow).
Some Secondary & Trace Nutrients
Slow Release Pellets or
Liquid Fertilizer?
Not sure which to use?
Liquid Fertilizer?
Not sure which to use?
Slow Release Pellets (like Osmocote) are great to use at the time of planting. Mix it in with the soil in your pots or in the hole if planting in the ground. This will ensure that the fertilizer is down where the plant roots can get it easily. Read your labels! Most slow-release fertilizers will say something like "lasts for 4 months!" Reading the fine print will tell you that it will last for 4 months at 70 degrees F. As the temperature increases, so does the rate at which "slow-release" fertilizers release their nutrients!
Liquid fertilizers
are also good. A benefit of liquid fertilizers is that you can combine
your watering and fertilizing tasks into one activity. The down side
is that any fertilizer not used immediately by the plant will leach
away. When using liquid fertilizer remember that you must use it every
time you water. If you are using an inorganic liquid fertilizer to
water containers (you know, the ones that turn your water blue) you must
remember to occasionally flush your pots with fresh clear water. This
will help to eliminate salt build-up in your pot.
Organics
Organic fertilizers and soil amendments are any material derived from plant, animal or mineral origin which offer nutritional value to plants. In order for organics to work they must first be digested by microbes found in the soil and released in a form that plants can absorb through their roots. This process has several benefits:
Improves Soil Structure - digestion of nutrients by microbes creates humus which enhances the soil's capacity to hold water, air and nutrients.
Long-Lasting, Slow Release - this process make take several months. Microbial activity rises with soil temperatures ensuring that plants receive the proper amount of nutrition when they need it.
Safe to Use - organics are non-toxic and safe for the enivronment. Organics contain secondary and trace nutrients often not contained within inorganic fertilizers.
Won't Burn - organics have very low salt content which lowers the risk of "burning" plants during drought or through over-fertilization.
Improves Soil Structure - digestion of nutrients by microbes creates humus which enhances the soil's capacity to hold water, air and nutrients.
Long-Lasting, Slow Release - this process make take several months. Microbial activity rises with soil temperatures ensuring that plants receive the proper amount of nutrition when they need it.
Safe to Use - organics are non-toxic and safe for the enivronment. Organics contain secondary and trace nutrients often not contained within inorganic fertilizers.
Won't Burn - organics have very low salt content which lowers the risk of "burning" plants during drought or through over-fertilization.
Won't Leach Out of Soil - plants only absorb nutrients when they need it. Unused inorganic fertilizers will leach out of the soil, organics however, do not leach out of the soil and are consistently available when the plants need them.
Organic Soil Amendments
Peat Moss: Low in nutrients but is a good soil conditioner.
Manure: Is both a soil conditioner and fertilizer. Never use fresh...compost first. Rabbit and poultry manure are twice as rich as that of horses, cows and pigs. Sheep and goats sit somewhere between the two. Good source of nitrogen.
Sewage Sludge: Milwaukee's Milorganite is a good commercial fertilizer. Not recommended for use around vegetables as they tend to be higher in heavy metals.
Leaf Mold: Composted leaves are high in micronutrients and is a good soil conditioner.
Fish Emulsion: High in nitrogen. Can be absorbed through leaves or roots. Also has positive effect on plant growth and overall plant health. Can be a little smelly.
Bonemeal: Contains mostly phosphorus. Very slow acting.
Sawdust: Works as a soil contitioner but ties up soil nitrogen until it becomes composted. Do not use cedar, redwood or walnut sawdust as they contain chemicals which inhibit the growth of other plants.
Wood Ash: Added to soils to raise a low pH. Can be spread around plants to keep slugs at bay.
Blood Meal: Nitrogen fertilizer.
Compost: Excellent soil conditioner. Compost creates carbon-dioxide which helps plants grow.
Feeling thrifty? You can make your own fertilizer at home from some common household items. Try some of the following recipes:
General Foliage Plant Food:
1/4 tsp instant tea
1/2 Tbsp ammonia
1/2 Tbsp hydrogen peroxide
1 capful bourbon
Put in 1 gallon warm water.
Label the container. When using, mix 1 cup of this mixture with a gallon of water. For flowering house plants, use vodka instead of bourbon.
Natural Plant Food:
5 drops liquid fish fertilizer
4 tsp instant tea
1/2 tsp liquid dish soap
Put in 1 gallon of warm water.
Label the container. Use this mixture at full strength.
Balanced Chemical Plant Food:
4 tsp instant tea
1/10 tsp 15-30-15 fertilizer
1/2 tsp ammonia
1/2 tsp liquid dish soap
Place in 1 gallon of water.
Label the container. Use this mixture at full strength.
5 drops liquid fish fertilizer
4 tsp instant tea
1/2 tsp liquid dish soap
Put in 1 gallon of warm water.
Label the container. Use this mixture at full strength.
Balanced Chemical Plant Food:
4 tsp instant tea
1/10 tsp 15-30-15 fertilizer
1/2 tsp ammonia
1/2 tsp liquid dish soap
Place in 1 gallon of water.
Label the container. Use this mixture at full strength.
