Reducing Land Degradation
- Improving Availability Of Nutrients
(Page 2)

<< Page 1



By Professor Nils Nykvist

Soil enriched in villages and towns (continued)

Such enrichment of soil improves the availability of nutrients in the soil, which then enhances the growth of deep-rooted trees and shrubs planted around the latrine pits. The above-ground biomass of these plants can be utilized in the form of fruits and berries, without any risk of proliferation of intestinal bacteria. Leaves and branches can also be used as compost for increasing the growth of agricultural crops.


In communities with sewerage systems, many attempts have been made to pump out untreated sewage and spread it on surrounding farmlands. Although this method from a plant ecological point of view is good if the wastewater does not contain toxic substances, it can, from the hygienic point of view, be very inappropriate, because pathogenic bacteria can be spread by the wind when the soil dries out. On a smaller scale this risk can be prevented by infiltration of the wastewater deeper down into soil.

The use of chemical fertilizers

The depletion of nutrients in the soil can now easily be overcome by adding fertilizers.

Because of the so-called Green Revolution the yields from agricultural crops have in a short time risen sharply in several countries. These yield increases are often described in the media only as resulting from the creation of new, high-yielding varieties. It may therefore be appropriate to disclose the circumstances in which these so-called super crops have been formed.

The original varieties were adapted to low concentrations of plant nutrients in the soil by a large root system. In fertilized soil, the roots do not need to penetrate such large volumes of soil to take up enough nutrients. At sufficiently high fertilization rates, part of the root system is therefore superfluous. This creates conditions for the establishment of new high-yielding varieties where more of the organic substances formed through photosynthesis go to the parts of the plant that can be harvested, and less to the root system.

A reduced root system however means that the plant’s ability to take up water is reduced, which is especially important on coarse-grained soils where the plant’s uptake of water cannot be replaced by a capillary flow of water in the soil. For many high-yielding varieties, irrigation is therefore essential.

The high intensity and uniform crops are also more vulnerable to damage caused by different organisms, and therefore require larger amounts of chemical pesticides. In unfertilized soils, the new high-yielding varieties give a very low crop production because of the reduced root system.

In several countries with relatively good economies, the high-yielding varieties with accompanying high doses of chemical fertilizers, treatments with biocides, and irrigation have decreased food shortages considerably.


For the poorest farmers, however, the Green Revolution with expensive, patented super crops has mostly been too costly. However even small amounts of chemical fertilizers could increase the crop yields and be more profitable for the farmers. The varieties to be used should be the old varieties with larger root systems that can take advantage of even small amounts of fertilizers and utilize the soil water better.

Even small amounts of fertilizers could increase the crop yields and be more profitable for the farmers than the cost of the Green Revolution. The varieties to be used should be the old varieties with large root systems that can take advantage of even small amounts of fertilizer and utilize the soil water better.

Nitrogen fertilizers can to a greater or lesser extent be replaced by nitrogen-fixing plants that do not give rise to such high contents of the greenhouse gas dinitrogen monoxide (laughing gas) as do chemical fertilizers.

See the references for this article.


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