Read the following passage and answer the items that follow. Your answers to these items should be based on the passage only.
The law in many parts of the world increasingly restricts the discharge of agricultural slurry in to water courses. The simplest and most economically sound practice returns the material to the land as semisolid manure or as sprayed slurry. This dilutes its concentration in the environment to what might have occurred in a more primitive and sustainable type of agriculture and converts pollutant into fertilizer. Soil microorganisms decompose the organic components of sewage and slurry and most of the mineral nutrients become available to be absorbed again by the vegetation. The excess input of the nutrients, both nitrogen and phosphorus – based, from agricultural runoff (and human sewage) has caused many ‘healthy’ oligotrophic lakes (low nutrient concentrations, low plant productivity with abundant water weeds, and clear water) to change to eutrophic condition where high nutrient lead to high phytoplankton productivity (sometimes dominated by bloom-forming toxic species). This makes the water turbid, eliminates large plants and, in the worst situations, leads to anoxia and fish kills; so called cultural eutrophication. Thus important ecosystem services are lost, including the provisioning service of wild-caught fish and cultural service associated with recreation.
The process of cultural eutrophication of lakes has been understood for some time. But only recently did scientists notice huge ‘dead zones’ in the oceans near river outlets, particularly those draining large catchment areas such as Mississippi and North America and the Yangtze in China. The nutrient enriched water flows through streams, rivers and lakes and eventually to the estuary and ocean where the ecological impact may be huge, killing virtually all invertebrates and fish in areas up to 70,000 km2 in extent. More than 150 sea areas worldwide are now regularly starved of oxygen as a result of decomposition of algal blooms, fueled particularly by nitrogen from agricultural runoff of fertilizers and sewage from large cities. Oceanic dead zones are typically associated with industrialized nations and usually lie off countries that subsidize their agriculture, encouraging farmers to increase productivity and use more fertilizer.
According to the passage, what are the effects of indiscriminate use of fertilizer?
The passage explicitly details the consequences of indiscriminate fertilizer use, which align with statements 1, 3, and 4.
1. Addition of pollutants to the soil and water: The passage describes "excess input of the nutrients, both nitrogen and phosphorus – based, from agricultural runoff" leading to significant ecological damage, including the transformation of healthy lakes into eutrophic conditions and the creation of oceanic "dead zones." These excess nutrients, when causing environmental harm, function as pollutants. The text also mentions that proper management "converts pollutant into fertilizer," implying that unmanaged or excessive application results in pollution.
3. Nutrient enrichment of water bodies: The passage directly states that "excess input of the nutrients... from agricultural runoff... has caused many ‘healthy’ oligotrophic lakes... to change to eutrophic condition where high nutrient lead to high phytoplankton productivity." This clearly describes the nutrient enrichment of water bodies.
4. Creation of algal blooms: As a direct consequence of nutrient enrichment, the passage notes that "high nutrient lead to high phytoplankton productivity (sometimes dominated by bloom-forming toxic species)." Furthermore, it mentions "decomposition of algal blooms, fueled particularly by nitrogen from agricultural runoff of fertilizers," confirming the creation of algal blooms.
2. Destruction of decomposer microorganisms in soil: The passage states, "Soil microorganisms decompose the organic components of sewage and slurry and most of the mineral nutrients become available to be absorbed again by the vegetation." This indicates that soil microorganisms are active in the decomposition process, facilitating nutrient cycling, rather than being destroyed by the indiscriminate use of fertilizers.