There are fertilizers that are natural, like manure, and fertilizers that are man-made. NPK fertilizers are fertilizers that contain the elements nitrogen (N), phosphorus (P), and potassium (K).
Why these elements? Well, each element has been found to improve the health and appearance of plants. For example,
Nitrogen is good at making the leaves grow
Phosphorus improves fruit and/or flower production as well as root growth
Potassium is great for overall plant health
Often the soil the plants are growing in lacks some of these nutrients, so by adding them in as a fertilizer, plants do better. Let’s say you buy a 50 lb. bag of fertilizer that says 10-6-4 on it. The first number represents nitrogen, the second number is phosphorus, and the third is potassium. And, if it is a 50 lb. bag, the numbers indicate that 5 lbs. is nitrogen (or 10%), 3 pounds is phosphorus (or 6%), and 2 pounds is potassium (or 4%).
How N-P-K Affects Crops
Nitrogen (N) mainly affects vegetative growth and general health. Nitrogen ensures that leaves can grow. It is a nutrient that gives leaves their green colour and makes leaves produces oxygen. Nitrogen deficiency is recognized by the yellowing of leaves and slowing or stopping of growth. Excess of nitrogen is recognized by extremely fast growth, resulting in long and weak shoots with dark green leaves.
Phosphorus (P) is largely responsible for root growth and fruit and flower development. Phosphorus is used more heavily during blooming and seed sets. Phosphorus is easily unavailable to crops when the pH is slightly unbalanced. It is released in the soil through decomposing organic matter. Phosphorus deficiency is recognized by dull green leaves and purplish stems.
Potassium (K) is important for the general health of plants. Potassium is also known to help with disease resistance. It also stimulates root growth and the development of the trunk.
A limited field can be fertilized before planting by scattering fertilizer over the area and tilling it into the soil.
Broadcast pre-plant treatment is ideal for wider areas; after application, till the soil to incorporate the fertilizer and reduce the risk of run-off in the event of rain.
Dilute the fertilizer in a bucket of water to avoid poisoning the plants, particularly the tender young ones. That solution can be used to water your plants. This approach also makes it possible for the plant to consume it. Water the plant again since fertilizing it with fertilizer, except this time with normal water. This second watering is used to flush out any fertilizers that could have fallen onto the leaves and stems.
Pour the fertilizer into a clean, dry bucket and walk down the row, dropping the fertilizer next to plants. The chemicals in the fertilizer will burn plants if dropped directly on them. For small plants, use a small volume, about one tablespoon each.
A cultivator fitted with a side-dressing apparatus may be used to apply directly to row crops. A hopper with a wheel to drive a dispensing mechanism and chutes to guide fertilizer to the row make up this device.