N-P-K? The Low-Down on Fertilizer

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N-P-K? The Low-Down on Fertilizer

Fertilizer is used to supply nutrients and fertility to plants, it comes in many different formulations of nutrients. Generally when we think of fertilizer we think of the values N-P-K which are usually listed on the bag or box for example 34-0-9 or 8-12-6. These values stand for nitrogen, phosphorus and potassium which are three major macro nutrients essential to plants. Calcium, Sulfur, and Magnesium are also macro nutrients essential to plant growth. Nutrition of plants just doesn't stop there though. Plants also require micro nutrients as well which include: boron, chlorine, copper, nickel, iron, manganese, molybdenum, cobalt, silicon and zinc. Understanding soil health and plant requirements can help you grow your plants to their full potential!

Nitrogen- N
Nitrogen is a component of chlorophyll making it necessary for photosynthesis to occur.  It is essential for green growth and foliar production. When plants are deficient in nitrogen plants leaves will display yellowing. An excess of nitrogen can burn plant tissue.  Natural sources of nitrogen include blood meal, feather meal, and manure. Always be carefully not to burn with excess nitrogen. Many turf fertilizers have a very high nitrogen content to ensure a good green-up of the lawn.

Phosphorous- P
Phosphorous is important for the growth of roots and stems. By helping root development it improves the efficiency of water uptake.  It also helps produce blooms and fruiting on plants. Root contact is important for phosphorous up-take. When a plant is lacking phosphorous it can cause stunted growth, spindly growth and leaves can turn bluish or reddish. High amounts of phosphorous can be toxic to plants. Phosphorous is slow to leech out of the soil and therefore can build up if used in high amounts. Natural sources of phosphorus are bone meal and bat guano. Due to the build up of phosphorous natrually in our soil many turf fertilizers do not contain it, many of the fruit, vegetable and all-purpose fertilizers still have a source of phosphoros as it is greatly needed for fruit and flower production. 

Potassium -K
Potassium is important for fruit and vegetable production in plants. It also increases resistance of plants to diseases and insects. Potassium is important for the movement of nutrients, water and carbohydrates in plant tissue. Deficiency symptoms include browning of edges which can also be accompanied by a striped appearance.

Calcium- Ca
Calcium helps neutralize toxic materials. It helps improve cellular structure and is important for the development of the root system and functioning of the plant. Calcium is important for any fruiting crop. Sources of calcium are gypsum, Neptune's Harvest crab meal and Off-The-Vine with added calcium fertilizer.

Magnesium is an essential ingredient in chlorophyll. It also helps in the uptake of other nutrients especially phosphorous. Plants that are deficient have less resistance to drought, cold and disease.

Several proteins include sulphur in them and are needed for making chlorophyll. It improves stress tolerance in plants. Deficiency symptoms include stunted growth and pale green leaves.

Having deficiencies in micronutrients is rare but can avoided by always adding organic matter to the soil and using amendments such as green sandglacial rock dust, and kelp meal. Glacial rock dust also helps the availability of nutrients in the soil helping your plants grow strong. Humic Acid can also be used to help availability of nutrients in the soil. Humic acid can unlock nutrients trapped in the soil and also stimulates and increases the micro life in the soil.  Kelp meal can be used as an organic source of boron for root crops and also helps build a stronger disease and insect resistance.

When it comes to plant health a diversity of amendments is important to have healthy crops and not just N-P-K values. Each growing season it is best to amend soils with composts, manures, etc along with ensuring you are fertilizing plants at proper intervals throughout the season. If problems with plants continue to persist a soil test can help provide more insight into just what's in there. 



can you suggest the appropriate fertilizer for growing carrot in only moderate rich soil (first yr)

Posted by Everett Russell on April 16th, 2015

Hi Everett,
The best fertilizer for root crops would be a garden fertilizer with boron 3-15-6.

Posted by Halifax Seed Company on July 31st, 2015

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