Once, the only things we added to the soil to help us grow our crops for food was a bit of manure and some compost. Since when plants grow, they take their nutrients from the soil. Farmers used to manage their fields to make sure they produced healthy plants for future harvests, by rotating the crops around different fields. If necessary, they also grew plants like clover because of their special ability to help nutrients become more available in the soil and used the greenery from them to feed their cattle. Very close to how organic agriculture works now.
Nowadays though, conventional farming has become big business around the world, becoming much more about churning out as much food as possible, as fast as possible with as much profit as can be made.
Farms rarely mix keeping animals for meat or milk with growing crops in the commercial world – they tend to specialise in meat, milk or crops. This means growing plants just for animals to eat isn't usually worth it, unless they're doing it as their main venture, and crop rotation seems too slow. Grow it fast farming stresses the soil which cannot quickly replace the nutrients needed to produce strong, nutritious and healthy plants. So in order that the living soil can keep up with how much farmers are taking from it, artificial fertilisers and nutrients are used a lot, rather like us living only on vitamin and mineral supplements instead of natural food. To stop bugs and small animals from eating the crops, farmers spray regularly with pesticides and insecticides – poisons designed to kill insects and small creatures.
To most governments and farmers, this seemed like a really clever idea at first, but people are starting to realise that there are consequences to this fast, wasteful and chemical dependent way of farming.There is another article about some of the often unnoticed consequences of intensive farming, but here we're going to concentrate on fertilisers and pesticides, looking at the dangers they pose to our environment and to us.
One of the main problems with fertilisers is that when we put them into the soil, the rain can wash them off the land and into streams and rivers, where they generally create excessive plant growth and decay, favouring certain weedy species over others, and may cause a severe reduction in water quality. This called eutrophication.
Put simply, fertilisers cause a massive overgrowth of algae and plants in the water, which then die and start to decay, causing there not to be enough oxygen for the other water creatures to survive. It can happen with natural fertilisers too, and the best way to avoid it happening at all is to only use small amounts of fertiliser, during the growing period of the plants so that the plants use it up fast – meaning it's less likely to get washed into streams.
Pesticides are designed to kill small creatures, so it won't surprise you that they are toxic.