Soil Biodiversity, Soil Conservation and Agriculture

A view of cultivated farm and. Soil biodiversity is threatened by unsustainable land use systems and management practices. FAO Kagera project in Rwanda

Our agricultural activities exert an important influence on the soil biota, their activities and diversity. Clearing forested or grassland for cultivation drastically affects the soil environment and hence reduces the number and species of soil organisms. The reduction of quantity and quality of plant residues and the number of higher plants species leads to a reduction in the range of habitats and foods for soil organisms.

Different types of agricultural practices and systems affect the soil biota in different ways and the response may be either positive or negative depending on which part of the soil the biota, e.g. fungal or bacterial, is affected. For example, organisms which are sensitive to pH will be affected by the addition of lime; the bacterial: fungal ratio will be affected by the addition of fertilizers and manures which alter the C:N ratio as will the effects of tillage. Tilling the soil will reduce the number of fungal hyphens, because soil aggregates, which are held together by these hyphens, are broken down.

Response of soil biota to disturbance. The figure illustrates the effects of agricultural practices on the soil biota after an initial disturbance. These responses are dependent upon on local climate or soil conditions and not applicable to all of the soil biota.

About 99% of the world's food supply comes ultimately from land-based production with about 50-70% of the land devoted to agriculture. As the population is estimated to reach 9-10.5 billion by 2050 we cannot ignore the health of the 'soil organism' if we want to be able to provide food and feed for increasing consumption and sustain our soil resources. Modern agricultural methods such as plowing, fertilizer application and pesticides have often replaced biological soil functions and increased the reliance on external inputs to maintain productivity, which in the long run is unsustainable.