Dave Deppner was a former Peace Corps volunteer in the Philippines who went on to put up his own NGO called Trees For The Future. He was a good friend who had promoted for many years sustainable farming techniques in the Philipines, South America and Africa.
One time, he explained at the Agri-Kapihan that among the practices that damage the soil is excessive use of chemical pesticides and fertilizers. He maintained that insecticides and chemical fertilizers are unsustainable, temporary solutions that almost never improve the quality of the soil.
Pesticides, he said, often kill much of the insects and microbes in the soil that are needed for natural processes. He added that there are, in fact, many beneficial insects that eat many of the problem insects but insecticides kill everything indiscriminately.
On the other hand, chemical fertilizers cause long term damage, and they are often inadequate in their nutrient content. Soils need rich organic matter in the form of humus, compost, manure and others.
Deppner said chemical fertilizers cause at least four problems. (1) They kill the beneficial organisms that live in the soil. (2) Chemical fertilizers also cause the soil to become acidic which is often not conducive to plant growth. (3) Chemical fertilizers create hardpans which can form naturally or unnaturally under the soil. This could trap the water which can cause waterlogging and rotting of the roots. (4) Chemical fertilizers can also damage plant health. Sudden large increases in nitrogen levels combined with a lack of trace elements have been known to cause diseases in plants.
Overuse of chemical fertilizers inhibits the chemical and physical reactions that transfer trace elements into the plants through the root hairs.
That was one clear explanation that our good friend shared with us at the Agri-Kapihan. Unfortunately, Dave has now gone to his Creator.