Loss of Soils
The imperceptible loss of a millimeter in the thickness of cultivable soils on the surface of one hectare would be equivalent to removing between 11 and 16 tons of agricultural soil per hectare. In other words, 10 cubic meters of fertile soil per hectare would be lost. Likewise, the loss of one centimeter in the thickness of cultivable soils on the surface of one hectare, would be equivalent to
eliminating between 110 and 160 tons of agricultural soil per hectare. In other words, 100 cubic meters of fertile soil per hectare would be lost.
Erosion in agricultural soils is an increasing problem. Global climatic changes lead to variations in the amount of rain that sometimes occurs intensely for short periods. Erosion from rain or poorly applied irrigation causes many of the nutrients in the soil to remain in the lowlands, which are generally not cultivable because they are flooded. Large growing areas offer more area for water and wind to flow causing erosion. Soils without vegetation cover are fully exposed to erosion, either by water or wind, which carry nutrients from agricultural soils.
Even though soil movement is a natural process, it must be taken into account that during the last 40 years, the land and the ways of cultivation have changed. It is currently cultivated under less favorable conditions. The cereal harvest encourages the soils to remain uncovered and exposed to the action of rain and wind. Likewise, the abandonment of
farmland, due to crises in the countryside, and inadequate forms of agriculture, leaves
the soil without organic matter. Rain patterns have certainly changed in recent years, but not as much as agricultural practices.
The movement of soils caused by rain and wind brings with it material that contains essential organic and inorganic nutrients for vegetables and the beings that consume them. Nutrient loss occurs, even when the water running over agricultural soils appears transparent and there is no clear physical evidence of erosion. These nutrients, together with agrochemicals, will be deposited in lowlands and rivers. We know that movement and erosion due to rain affects more in sandy soils, especially those with little organic matter, which maintains the structure of agricultural soils. Erosion and movement begins when the soils are completely saturated with water, which can even happen with moderate rainfall. The speed of movement is greater in sandy soils,and can worsen on steeper terrain. Thus, as a result of rain or poorly applied irrigation, accumulates sand in the lower parts of the terrain.
Experiment
Through the following simple experiment it is possible to know the approximate amount of soil that remains in cultivated fields:
- Put a fist of earth into a clear bottle and fill it with water. Shake the bottle and let it stand. About 5 minutes, the sand and stones will be at the bottom of the bottle. The water will remain cloudy with soil particles in it. Suspension: It will take a few hours for the larger soil particles in suspension to settle in the bottle on sand and stones, and a few days for the smaller soil particles to settle in the bottle. Let us remember that the soil particles contain nutrients of enormous importance in agricultural production.
Loss Reduction
In the European Union the following measures are popular with farmers and ranchers to reduce losses and promote soil conservation:
- Sowing grasses together with cereals and between harvests. Good drainage system to reduce the available area to rain erosion. Vegetable cover in the soils to offer resistance to erosion by rain and wind. Conservation tillage to improve drainage and aeration in Soils. Cultivation lanes at minimum levels. Seeding beds not too thin, because compacting reduces porosity in soils and increases rain erosion. Soils covered with straw or other residual plant material.
The methods of minimum tillage or conservation tillage, make the earthworm burrows remain in the soil, promoting the existence of organic matter and better drainage. Regular monitoring is necessary to learn about soil structure and nutrient loss, especially when earthworm activity is insufficient. In
autumn-winter crops it is advisable to sow as soon as possible to ensure that the soil is kept with vegetal cover.
Organic material
Good structure in agricultural soils is better maintained as more organic matter exists in them. This is because humus helps to maintain the consolidation of particles in soils, particularly in sandy soils. Incorporating manure, and minimum tillage or conservation practices, add enormous benefits to the structure of the
floors. Soils are compacted due to the trampling of livestock and the passage of machinery and vehicles. In compact soils, water only penetrates a few centimeters into soils, without going as far as vegetables require it. Likewise, there are soils of a compact nature, the structure of which can be improved by applying organic matter. In some regions of England, waste fish and seaweed have been incorporated into the soil for centuries as organic matter to preserve fertility and
structure on agricultural land.
