More topics in this section. Nutrients Nitrogen On farmed land, most nitrogen is in organic matter which must first be mineralised by soil microbes into ammonium or nitrate to be used by plants.
Phosphorus Phosphorus is a very stable element and moves only 1—5 mm from where it is spread. Potassium Potassium is taken up by plant roots very rapidly and is not used in great quantities, so represents little environmental threat. Environmental hazards Groundwater pollution Nitrate leaching through the soil can present a serious health hazard and contributes to soil acidification.
Eutrophication Eutrophication is the enrichment of water by the addition of nutrients. Soil acidity There are three major acidifying processes in NSW agricultural systems: addition of nitrogen to the soil by fertiliser or fixation of atmospheric nitrogen, followed by loss of nitrate from the soil due to leaching or run-off production of organic acids from decomposing organic matter removal of alkaline products such as hay from the soil.
Contrary to popular belief, superphosphate does not cause soil acidification. You can take several actions to lower acidification rates in your soil. Use less acidifying nitrogen fertilisers: for example, use urea rather than ammonium sulfate. Incorporate stubbles into fallow to minimise net nitrification. Sow early to maximise the opportunity of the crop to recover soil nitrate. Use perennial deep-rooted plants able to rapidly absorb mineralised nitrate at the start of the growing season and maintain low soil nitrate levels throughout the year.
Use deep-rooted crops. Minimise water percolation below the root zone. Avoid excessive irrigation. Minimise removal of product from the soil. To prevent acidification you need to apply 55—60 kg of lime for every tonne of lucerne or clover hay removed; 35 kg of lime per tonne of grass hay removed; 22 kg of lime per tonne of cereal hay removed; and 3 kg of lime per tonne of cereal grain removed. Minimise manure removal from pastures, preferably leaving manure where the animals graze.
As humans, we get our nitrogen from the food we eat. High protein foods like meat, fish, nuts, or beans are high in nitrogen. Plants get their nitrogen from the soil and nitrogen is the most common nutrient to limit plant growth. However, even with all this natural nitrogen fixation , low nitrogen levels in soils often still limit plant growth. This is why most fertilizers contain nitrogen compounds and why industrial fertilizers are essential in order to produce enough crops to feed the human population.
As mentioned, most nitrogen on Earth is present as nitrogen gas, which is unusable for plants and animals. This industrial fixation is called the Haber-Bosch process. Almost all the nitrogen in industrial fertilizers is fixed through the Haber-Bosch process. This industrial fixation of nitrogen is performed in chemical laboratories and large factories all over the world. The Haber-Bosch process requires that nitrogen gas be mixed with hydrogen gas H 2 and put under enormous pressure times atmospheric pressure.
Sustaining these high pressures and temperatures requires a huge amount of energy. The short answer is that nitrogen-containing fertilizers help crop plants grow faster and helps to produce more crops.
This allows agricultural land to be used more efficiently because fertilized land produces more food. The crops take it up of course! Unfortunately, that is not the end of the story. So, while fertilizers make crops grow better and faster, half of the fixed nitrogen we add is lost. The lost nitrogen can end up in the atmosphere or it can be washed out of the soil and end up in waterways, such as groundwater, streams, lakes, rivers, and oceans Figure 2.
This lost nitrogen causes a variety of environmental problems [ 2 ]. Some soil microorganisms can transform nitrogen provided in fertilizers into nitrogen-containing gases, which get released into the atmosphere like the greenhouse gas nitrous oxide N 2 O.
Greenhouse gases are one of the main factors accelerating global warming. In waterways, the addition of external nutrients like excess nitrogen is called eutrophication. Eutrophication is an unwanted fertilization of a waterway and it promotes the growth of microorganisms, algae, and plants, just like the fertilization of soil. However, the fast growth of microorganisms and plants can use up all the oxygen in these waterways and turn them into so-called dead zones, because aquatic animals cannot live without oxygen.
Eutrophication can also lead to the growth of algal species that produce toxic chemicals, called harmful algal blooms. While we need nitrogen from fertilizers in our agricultural soils, we do not need or want additional nitrogen in our atmosphere or waterways. This means we have to balance the positive benefits of nitrogen fertilization more food with the negative consequences of excess fertilizer environmental problems [ 1 , 2 ].
High levels of nitrates can be toxic to livestock and humans. Nitrates are not adsorbed to soil materials, so they may leach to groundwater.
In some instances, stored or land-applied manures or nitrogen fertilizers have caused high concentrations of nitrates in water. Because nitrates freely leach down through the soil profile, nitrogen that is not used for crop or plant growth can reach the groundwater easily. Nitrate in itself is not toxic to animals, but at elevated levels, it causes a disease called nitrate poisoning. High levels of nitrates in drinking water are known to cause methemoglobinemia blue-baby syndrome in human infants and other warm-blooded animals.
In humans and livestock, nitrates interfere with oxygen uptake in the circulatory system. Manure odors can be a nuisance for nearby neighbors and communities. Constant nuisance odors can degrade the quality of life for anyone subjected to them. In addition, people have a wide range of susceptibility to health effects from odors.
Gases are emitted from facilities throughout the year but are released at the highest rates during agitation, pumping and application of liquid manure systems or during cleanout and application of solid manure systems. Volatilization of ammonia to the atmosphere may become a water quality problem near animal production facilities when it is returned to the earth dissolved in rainfall.
If managed properly, fertilizers and animal manures benefit crop production without causing environmental problems. In any management scenario, the manager must be aware of the possible negative consequences of mismanagement. Publications Accessibility. When nutrients and other pollutants associated with animal manures and commercial fertilizers are not managed properly, they can affect plant and animal life including humans negatively.
Some of these impacts include algae blooms causing the depletion of oxygen in surface waters, pathogens and nitrates in drinking water, and the emission of odors and gases into the air. Nutrients from manure and fertilizers enter lakes and streams through runoff and soil erosion. Generally, when soil-test nitrogen N and phosphorus P increase, greater amounts of plant-available N and P move with water. Runoff water from fields with high soil-test N and P may contain a high level of these dissolved nutrients, increasing the risk of contaminating streams, wetlands and lakes.
Oxygen Depletion When manure or commercial fertilizers enter surface water, the nutrients they release stimulate microorganism growth. Photo courtesy of North Dakota Department of Health Weed Growth and Algae Blooms The number of plants and algae in a lake, pond or other water body increase with an increased supply of nutrients, particularly N and P.
Photo courtesy of North Dakota Game and Fish Department In addition to oxygen depletion, the potential exists for the algae to be toxic. Ammonia Toxicity Ammonia-contaminated runoff from fresh manure application sites is toxic to aquatic life.
0コメント