Many people may not be aware that gardening can actually harm the environment.  A large amount of carbon dioxide can be released through tilling the soil.  This contributes to global warming.  When you cultivating and compacting the soil, destroys good fungi.  Fertilizers like nitrogen and manure often leach out of the soil and pollute the water you drink.

Global warming

Did you know that the earth's soil gives out carbon dioxide in the atmosphere 10 times more than all human activity?  This comes from the pill bugs, microbes, fungi and worms when they breathe, digest food and then die. Although in the past plants have been capable of absorbing carbon dioxide caused by small-scale tillages, this isn't the case nowadays. 
The increase of the globe's average temperature is because of the carbon dioxide the soil emits when tilled. The good news is that tilling can be minimized by mulching or sheet composting.

Good Fungi

In untilled soil, there is beneficial fungi known as the vesicular-arbuscular-mycorrhizae or VAM for short. VAM actually formS a symbiotic relationship with plants.  Their filaments increase root hairs and provide nutrients to the plant.  They give out zinc, copper, potassium and phosphorus.  Plants provide carbohydrates for the fungi in return.  It is possible to grow a garden without tilling the sooiil at all by mulching heavily until the soil is soft and friable.

Surplus Nitrogen

Many gardeners waste nitrogen and manures; farmers do otherwise. Farmers only need a quarter to a third of nitrogen to mix with an inch of compost, horse, or cow manure.  Kate Burroughs of Sebastopol California, uses the same rule for her home-grown lettuce and sweet corns. When it comes to broccoli and pear trees, farmers only need a small amount.  Notice that gardeners apply larger amounts of compost and manure than farmers. Obviously, they are not only wasting their fertilizer but also their money. 

The best gardening advice that can be given to those concerned is to do all things with moderation. Keep in mind that too little and too much of something is not healthy. This is the most valuable advice one can have in gardening.