- Improving Availability Of Nutrients
Below, Professor Nils Nykvist shared how the availability of nutrients in soil can be improved, mainly through combining agriculture with animal husbandry, taking advantage of soil enriched in villages and town, as well as through using chemical fertilizers.
By Professor Nils Nykvist
Combining agriculture with animal husbandry
Slash and burn agriculture is the main cause of fires
in the tropics. A transition to more permanent cultivation would therefore significantly reduce the occurrences of fire.
With permanent cultivation, however, the amounts of nutrients would after a few years of cultivation decrease so much that it is more profitable for the farmers to cut down and burn a new forest area and cultivate it. A permanent cultivation requires therefore that nutrients in one way or another be returned to the soil.
Before they began using chemical fertilizers in Scandinavia, the farmers solved the problem of soil depletion by combining farming with livestock. Plant biomass for feeding the animals was collected from fenced meadows in the surroundings and taken to the farm where the animals were kept during the winter. Manure from animals and humans were used to fertilize plots that could be cultivated year after year.
Thus, inorganic nutrients
from the surroundings were concentrated to the small, cultivated plots, whose size was determined primarily by the amounts of inorganic nutrients that could be obtained from the surroundings through the winter fodder.
The importance of this type of soil fertilization is well described in the old Swedish expression ‘the meadow is the mother of all cultivation’. With the exception of some years of severe drought and low crop production, this was a sustainable agricultural system for centuries until the early 1900s, when chemical fertilizers became more accessible to farmers in Scandinavia.
For many developing countries, this form of agriculture combined with livestock could be suitable for increasing the fertility of the often nutrient-poor arable land.
Unfortunately, it has been difficult to convince the farmers in developing countries about the advantages of this farming system, probably because the animals can graze outdoors during the whole year. The argument has often been: ‘Why should we collect their food? The animals have four legs and we have only two’.
Taking advantage of soil enriched in villages and towns
The plant nutrients that disappear from the surroundings through harvesting and collecting of firewood
actually accumulate at the settlements as latrines and ash (Fig. 24). As long as the villages moved from place to place within a larger area, the soil in a relatively large area could be enriched and utilized in later cultivations. Agriculture therefore does not lead to a significant depletion of the ground.
Figure 24. The best growth of crops is mostly near houses where plant nutrients have been enriched. Kenya.
However, as the settlements became more permanent, the closest farmland was impoverished, and the most fertile land became increasingly distant. In savannah areas of Africa, it is not uncommon that women have to spend many hours a day walking to and from their cultivations.
When the permanent settlements became larger, the accumulation of plant nutrients increased, leading to a greater loss through leaching. This loss increased further if the latrine pits became permanent, which in time became increasingly common, as many authorities recommended deep latrine pits to reduce the risk of snail fever (schistosomiasis).
Fortunately, in Asia, attempts were made as much as some thousand years ago to take advantage of the nutrients in the latrine and return it to farmland. Because of the disturbing odour, it was transported during the nights, which is why latrine contents became known as ‘night soil’. It is even said that farmers in China put out small cans along the roads, hoping that wayfarers would provide manure for the fields.
See the references
for this article.
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