Pollution

Advantages

• Chemical fertilizer can be made much faster unlike the natural fertilizer
• It has much more NPK, usually around 20 to 60 percent, natural fertilizer usually only has a max. of about 14 percent
• If it is made according to the soil that it will be used on, it will do nothing but grow a healthy plant

Disadvantages

• Puts acid in the soil
• Strengthens pestecides(they become stronger and more resistant to chemicals that should keep them away)
• Other than NPK it contains inert filler and maybe some unnesesary chemicals
• It has very little carbon which is a key element in plants
• It has no energy, so it can only help the plant when there is enough organic matter around from where it can get the energy, otherwise it burns the roots and destroys the plant
• Chemical fertilizer also get a lot of water out of the soil which it contaminated and therfor pollute water
• It degrades ecosytems
• It releases a green house gas called nitrous oxide

So in total, chemical fertilizer is worse than natural fertilizer

this site below helped me a lot, also for pros and cons about natural fertilizers

http://www.malcolmbeck.com/books/gv_method/FertilizerOrganicNaturalversusChemicalInorganic.htm

So what is the advantages and disadvantages of fertilizers ?

Most plants, especially modern varities, will pull more fertilizer molecules out of the ground than what is naturally resupplied. In a forest, the decomposing leaves and bark will feed the soil and give ferns (growing below the trees) enough fertilizer to live on. However, in a garden where you grow vegetables or flowers, these plants typically consume large quantities of fertilizer.. higher amounts than nature can naturally resupply.

in order for the plants to grow properly, they need the right amount of fertilizer available in the soil. If there is too little, growth may be stunted and flowers and fruits may not develop properly. The plants become suceptible to attack by insects and disease. A plant which is fed well is often able to survive better. This is the same with humans: people who are starving is often plauged by disease compared to people who get all the nutrients they need.

Therefore the gardener must manually fertilize the plants to ensure they have enough food to grow on. Plants which are fertilized often are bigger, stronger and produce more fruits and flowers than plants which are not fertilized. Fertilized plants are generally often also more disease resistant than unfed plants.

There really is no disadvantages to fertilizing, and most home owners should fertilize plants such as vegetables, fruits and flowers because these - persumably modern hybrids - tend to consume much more fertilizer than nature can provide.. This also goes for lawns, for example, which has individual grass plants growing very close together - much closer than grass plants would in nature - and therefore have to compete with each other for nutrients.

However, if you give TOO MUCH fertilizer the plants can suffer just as they would if they get too little. For example, both magnesium and calcium molecules are needed by the plants, but given too much calcium, for example, can interfer with the plants ability to take up magnesium and the other way around, too.

If you add fertilizer to certain plants when the soil is dry or the temperature is very hot, you also risk damaging the plants.

While there are no specific disadvantages to fertilizing if doing it correctly, you do need to know approximately which type of fertilizer (which nutrients) the plant require, how much to add, and when to add it. It also needds to be watered in to avoid that the plant dies from thirst (plants which grow in fertilizer rich soil without water will cause water to exit the plants and kill them).