Soil Formation vs Soil Degradation

Soil formation is a slow process compared with the present rate of soil degradation, but the question remains - how can intensive farming avoid the latter while promoting the former?

The problem seems to lie (in part) with the tendency for researchers to over-simplify the system. Both soil formation and soil degradation are viewed largely in terms of simple processes like physical compaction or water erosion without any consideration for the interactions that occur between these actions and contributing factors that promote or inhibit them.

Another problem with agricultural science generally is that it relies too heavily upon correlations, when it remains one of the most important scientific principles that correlation does NOT establish causation!

Let me give you an example to show what this means:

There has been a long recognized correlation between permanent perennial pasture and fairly rapid increase in soil carbon levels, but the cause has only recently become understood. Research into the different types of carbon present in soils (and there residence times) showed and substantial proportion of carbon under pasture was un-decomposed root segments. This finding was especially important when carbon 14 dating showed residence times ranging from several decades to a couple of centuries.

These root segments result from grazing of pasture. When grasses are defoliated by grazing, the old tillers die and the starch reserves in their roots are mobilized to support growth of new tillers (that grow their own new roots). As the old roots decay, some segments remain - coated with clay particles - effectively sealed off from air and bacterial action. Only soil fungi can access this carbon source, which means that this process also helps drive the ecological succession in the soil community towards greater fungal dominance - something that is then also beneficial for sustained pasture productivity.

Recently, results from long-term U.S. trials with no-till corn production showed a correlation between high nitrogen input and soil carbon levels - apparently comparable to that observed under pasture. The researchers attribute this result to increased biomass production resulting from fertilizer use (336kg N/ha), but is this correct?

Two other actions of high Nitrogen input are also known. The first is inhibition of soil organisms that specialize in utilizing Cellulose. This would appear to somewhat similar to the process under pasture, in that carbon is being 'protected' from the effects of normal decomposition. However, most cellulose ultilizers are fungi, so this process may actually be driving ecological succession in the soil backwards - analogous to the way a fire does in a forest!

The other effect of high Nitrogen input is soil acidification - which in turn also reduces soil biological activity.

This example shows the risk associated with correlation based research. The results can be highly deceptive and lead us to develop production methods that lead us to believe we are promoting soil formation, when in fact soil degradation is the real result.