Subj: {OHG} What is NPK?  
Date: 6/23/2003 3:29:04 AM Eastern Daylight Time 

What is NPK?

How well soil supports plant life determines its fertility. Three 
basic nutrients are essential to plants: nitrogen, phosphorus and 
potassium. 

(N) NITROGEN:
Nitrogen is essential for plant growth.  Nitrogen  is a part of every 
living cell. The two forms of nitrogen which plants take up are in 
the ammonia (NH4) and nitrate (N03) ion forms. Most agronomic crops 
take up most of their Nitrogen in the nitrate ion form.  Plants will 
utilize N in the (NH4) ion form if present and available to the plant.

Nitrogen is the first major element responsible for the vegetative 
growth of plants above ground. With a good supply, plants grow 
sturdily and mature rapidly, with rich, dark green foliage.  Too much 
nitrogen can cause plants to become leggy. Too little will stunt 
growth. 

Key roles of NITROGEN (N):
Nitrogen is necessary for chlorophyll synthesis and as a part of the 
chlorophyll molecule is involved in photosynthesis.  
Nitrogen is also a component of amino acids.
Nitrogen is needed for growth of plants

Lack of nitrogen and chlorophyll means that plants cannot utilize 
sunlight as an energy source to carry on essential functions such as 
nutrient uptake.   Research has proven foliar or leaf applications of 
Nitrogen is one form of application that can supplement a plants 
nitrogen requirements during the growing cycle.

(P) PHOSPHORUS:
Phosphate is a very important plant nutrient (macro-nutrient) needed 
for the plant to complete its normal production cycle. The highest 
level of P in young plants is found in tissue at the growing stage. 
As plants mature most of the P moves into the flower and then to the 
seed or fruit.
     
The second major element in plant nutrition, phosphorus is essential 
for healthy growth, strong roots, fruit and flower development, and 
greater resistance to disease. 

Key roles of PHOSPHORUS:
needed for photosynthesis.
needed for plant respiration.
needed for energy storage and transfer.
needed for cell division.
needed for cell enlargement.
several other plant processes.

(K)POTASSIUM:
An important function of Potassium is its influence in water use 
efficiency.  It helps in the process of opening and closing of plant 
leaf pores, called the stomata.  Potassium is found in cell walls 
which surround the stomata.  Adequate amounts of Potassium can 
increase stress conditions on plants during drought conditions.  
Potassium is also responsible for supplying quality to crops.

Potassium (K) is a word derived from potash (chemical symbol K). In 
the past, this nutrient was applied to gardens in the form of wood 
ashes.

It helps plants to resist diseases, protects them from the cold and 
protects during dry weather by preventing excessive water loss. 
(Wheat straw rots down into organic K).

Key roles of POTASSIUM(K):
Potassium is essential for protein synthesis.
Potassium is important in the breakdown of carbohydrates. (A process 
which provides energy for plants).
Potassium helps to control ionic balance.
Potassium is important in the translocation of heavy metals.  IE Iron 
(Fe)
Potassium helps plants to overcome the effects of diseases.
Potassium is essential in the fruit formation stage.
Potassium helps improve shelf life.
Potassium is involved in the activation of more than 60 enzymes which 
regulate the rates of major plant growth reactions.

CATIONIC:
In this stage of the plants life from flowering to harvest, the plant 
is in the production mode and no longer actively growing.  Higher 
PHOSPHORUS & POTASH is needed in this stage.

The availability of nutrients to your plants can heavily depend on 
acidity or alkalinity of the soil. This is measured in terms of pH. 
The scale ranges from 0.0 pH (most acidic) to pH 14 (most alkaline). 

A pH of 7 is neither alkaline or acidic and is referred to as pH 
neutral. Most plants prefer a pH of 5.5 to 6.5. pH can be easily 
measured by using a pH kit. Once pH has been checked soils can be 
adjusted using lime (to raise pH) or sulphur (to lower pH). It can be 
very difficult to lower pH of soils with pH over 8.3.

One indicator of healthy soil is the number of earthworms it 
supports. When a lot of organic matter is present, earthworms abound. 
Healthy soil is bursting with microorganisms breaking down organic 
matter into a usable form by plants. (Nitrates). Only where you find 
earthworms will you find rich, healthy soil with high amounts of 
organic matter and vice versa.  Earthworms simply cannot proliferate 
and flourish in areas where chemical fertilizers and pesticides are 
paramount.  Earthworms, actually, act as a barometer for soil health.

Natural organic fertilizers provide nutrients and encourage 
microorganisms to thrive. The organic materials turn into humus as 
microorganisms in the soil break them down. 

Synthetic fertilizers deplete organic matter in the soil, which leads 
to a more compacted soil. They also interrupt the ecology of the soil 
with the quick release of nutrients. Beneficial microorganisms are 
harmed, while harmful microorganisms are encouraged. 

Farmers are seeing that long-term use of NPK fertilizers creates 
compacted lifeless soil and builds up salts to toxic levels. 

Grow Organic.

Jon Wood-Founder of OHG, and an Organic Homestead Gardener.

References:
Personal knowledge of horticulture, agriculture, soil science, 
botany, and biology.
USDA
Advanced Master Gardeners Training
Owning and operating a working farm with truck crops.
And a few websites.

