Research looks at effects of organic and mineral fertiliser on soil health.

Tucked away in the murky depths of academia, there are often little gems of soil research that may not have made the headlines but they can still help point the way ahead.

One such is a paper written by Elif Yaganoglu and Aydin Adil, and published in the Turkish Journal of Agriculture and Forestry.

The aim was to investigate the effect of fertiliser, both organic and mineral, on soil health, with particular reference to three important enzymes found in the soil, either within microbes or as extracellular agents.

The research looked at three different soil types.

The overall effect on two different plant types, beans and maize was also measured, with the whole experiment conducted in a greenhouse environment rather than the field.

Although the method is carefully laid out and and the complex computations explained and discussed, it might be thought that the organic manure would be applied at an equivalent rate of nitrogen to the mineral fertiliser.

This, though, was not the case, as an arbitrary, but consistent, amount of manure was applied to each plot.

However, that small caveat aside, the results did show that both types of fertiliser increased soil health, according to the indicators being measured.

Higher rates of mineral fertiliser than used here may indeed have an adverse affect, especially if used over longer periods, but this could not be ascertained from the figures arrived at in this experiment.

Although the quantity of fertiliser was recorded, the actual rate of application was not, so no conclusions may be drawn on this assertion.

Yet, what does show support for those advocating a more natural system of farming is that the results indicated that natural manure was even more effective at promoting soil health.

The researchers note that with both fertiliser applications, organic matter, nitrogen (N), available phosphorus (P), exchangeable calcium, magnesium, potassium (K). and sodium, along with various microelements - iron, for example - all increased.

These changes in soil properties were more pronounced in the plots where organic fertiliser was added, according to the study.

To gain some idea of how the fertilisers affected total microbial activity, the level of dehydrogenase present in the soil was assessed.

Dehydrogenase-type enzymes are present in all microbes, so by measuring its level in the soil an indication of microbial activity can be gained.

It is when looking at these results that the benefit of applying organic manure becomes clear, as across all three soil types the increase in microbial activity was greatest when manure was applied.

This might seem a clear-cut result, but the researchers appeared not to take into account that, by adding manure, they were adding microbes, and so the analysis would be very likely to show an increase anyway.

In summary, the trials go towards confirming the general belief that manure adds more to the soil than just NPK, it also encourages biochemical reactions which in turn benefit plant growth.

Yet there is another aspect worth highlighting, which is that in addition to the plots with plants grown, there were controls when nothing was planted.

In these controls, the level of enzyme activity was significantly lower than in those which had plants growing, suggesting that the presence of roots is an important factor in encouraging a healthier soil.

This latter finding gives weight to the argument that keeping tillage fields green with the sowing of cover crops encourages a healthy soil along with retaining excess nitrogen.