Monocultures are difficult to endure

Elements and molecules, school book

128 6 AIR, WATER, SOIL - OUR ENVIRONMENT Alumosilicates Acids Al 3+ acids in the rain Increase in pests Effects of a MONOCULTURE Groundwater pollution Drinking water pollution Increased use of insecticides Damage to microorganisms Loss of humus Loss of humus Reduction of the water storage capacity, why 128.1 leaching of fertilizer salts is used hoped through “lime fertilization” to alleviate the forest damage! EXERCISES Fig. 128.2: Effects of a monoculture Fig. 128.1: Effects of “acid rain” In addition to the cycle with the air, the cycle through the rotting of plants or their utilization by animals plays the most important role. Plant protein is broken down (animal or bacterial). The end product of animal degradation is urea (in urine and faeces), which breaks down into ammonium salts. Ammonium compounds are also formed during bacterial degradation. These are oxidized by oxidizing microorganisms with atmospheric oxygen via nitrite to nitrate and are available as nitrate for the next generation of plants (Fig. 127.4). The pH value of the soil is also decisive for soil fertility. Lime ensures pH stabilization with its buffer capacity. Therefore, calcareous soils are less susceptible to acidic precipitation. Too much acidification of the soil mobilizes aluminum ions. (Fig. 128.1) As soluble salts, they disrupt the calcium balance of the plant roots. Therefore, in addition to the nutrients, lime is also fertilized on lime-poor soils. However, this is difficult to do over a large area in forests. Therefore, acidic air pollutants (both SO 2 and NO x) are seen as the main cause of forest death. The pollutants attack needles and leaves directly and also weaken the tree through soil acidification. Bog soils - for example in the Waldviertel - often do not contain any lime or clay (peat). They can be very acidic (pH 3–4). Only plant species adapted to these soils can exist there. However, these plants do not tolerate neutral or basic soils. However, a soil that is too alkaline also has disadvantages for most plants. The absorption of phosphate is then made more difficult because soluble hydrogen phosphates are converted into poorly soluble phosphates. The nitrogen content of the soil is partially converted into free NH 3 in the ammonium stage and escapes. The most important role for agriculture is a regular water supply. In our latitudes there is usually a sufficient amount of rainwater available. The excess water seeps away and is transported away with the groundwater streams and rivers. Artificially irrigation is required in dry areas. This can lead to major soil problems. If there is insufficient irrigation, the water evaporates instead of seeping away. Salts dissolve from deeper soil layers in the water. These salt solutions rise capillary. Due to the strong evaporation, the upper soil layer is increasingly enriched with salts (gypsum, sodium chloride). Salt bloom occurs and the soil becomes sterile. In soils that are used intensively for agriculture, fertility can suffer due to incorrect long-term cultivation concepts. Often only a few or only one fruit are grown annually in monocultures. This concept is known from the USA (wheat belt, corn belt, etc.). But it is also widely used in Austria. The advantage of using specialized machines profitably is offset by major disadvantages. The same nutrients are withdrawn from the soil every year and this is compensated for with the massive use of fertilizer salts or liquid manure from large pig farms. In the process, the soil is increasingly depleted in humus and thus in water storage capacity. Some of the fertilizer salts are washed out and pollute the groundwater, which then becomes unsuitable for obtaining drinking water. Monoculture encourages the unchecked reproduction of pests, for which food is available in abundance every year. (When the crop rotates, the next generation of insect pests will find no food source in the following year.) This necessitates an increased use of insecticides. Residues and degradation products of agrochemicals accumulate in the soil and damage the soil's microorganisms in the process. Many natural control loops fail, which makes further use of agrochemicals necessary (Fig. 128.2). The concept of integrated crop production can help here. Attention is paid to crop rotation and fertilizer salts are only used in the required amount according to soil analyzes. The cultivation of green manure plants as catch crops ensures humus formation. As a result, the soil never remains uncovered, which prevents erosion and promotes soil organisms. Insecticides are not used prophylactically, but only above a certain threshold for pest multiplication. Subject areas and self-test for chapter 6 see page 269 For testing purposes only - property of the publisher öbv

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