hari is dependent on groundwater for irrigating is field he also use chemical fertilizer on is crops is he right doing its so what effect would such practices have on the groundwater?
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Answer:
Nitrate in drinking water, at high levels, causes "blue baby syndrome" or methemoglobinema. This is an acute illness that can occur in unborn infants and young children. It leads to low blood oxygen levels and possibly suffocation. In adults, long-term exposure to high nitrate levels in drinking water is potentially also associated with thyroid dysfunction and cancer. Where groundwater is the source of drinking water, nitrate may exceed the national drinking water standard of nitrate (45 mg nitrate per liter or, equivalently, 10 mg of nitrate-measured-as-nitrogen per liter).
For surface water sources of drinking water, nitrate generally does not exceed the drinking water standard. But nitrate in surface water - at levels much lower than the drinking water standard - may cause eutrophication. Eutrophication means that there are too many nutrients in the water, causing algal blooms, which in turn overuse the oxygen in streams, lakes, or oceans, ultimately leading to complete oxygen removal from these aquatic ecosystems ("hypoxia"), killing fish and other aquatic life (including the algae).
What are the sources of nitrate?
Nitrate is part of the earth's reactive nitrogen cycle. Nitrogen is a key ingredient in synthetic fertilizer. It is also part of any living materials (for example, proteins contain a lot of nitrogen). Human and animal waste, and dead plant and food waste materials therefore also contain nitrogen, typically as organic nitrogen or as ammonium. Fertilizer, human/animal waste, or other plant/food waste (e.g., compost) is commonly applied to land (for example, in septic leach field, wastewater percolation ponds, biosolids applied to cropland, wastewater effluent applied to cropland, synthetic fertilizers applied to crop). Once in the soil, nitrogen will travel to groundwater as nitrate unless it is used by plants, released into the atmosphere, or washed out in overland runoff. It may also be stored temporarily in the soil root zone or in growing perennial plants (trees, vines).
Where are the nitrate sources?
Nitrate sources are effectively everywhere - agricultural lands, natural lands, urban areas with leaky sewer lines, septic leach fields, and wastewater percolation basins. Not all sources pollute groundwater. There is great variability in nitrate loading to groundwater between different sources, between different management practices, and from locale to locale due to variable natural conditions that affect the fate of nitrogen.
How much nitrate does an average cow produce?
An average milking cow produces about 1 lb per day of nitrogen in its urine and feces. Cow manure is stored (solids in piles, liquids in storage lagoons) and then land applied. Between 20% and 40% of the excreted nitrogen will end up in the atmosphere, the remainder is land applied on forage crops or other crops. A dairy with 1,000 milking cows has about 300,000 to 400,000 lbs of fertilizer nitrogen available for land application via manure. Manure nitrogen is partly organic nitrogen, which is relatively difficult to manage as fertilizer. Part of manure nitrogen is ammonium, a commonly applied fertilizer.
How much nitrogen does a farmer use?
Nitrogen fertilizer applications depend, first, on whether the crop can "make" its own nitrogen (alfalfa, beans, other legume crops). If the crop needs an outside source of nitrogen, fertilizer is applied and the amount will depend mostly on the nitrogen demand of the crop. The more nitrogen is harvested with the crop, the larger the need for fertilizer. Grapes remove relatively little nitrogen with their harvest (less than 20 lb of nitrogen per acre per year). Where two non-leguminous forage crops are grown each year, or in vegetable crops, but also in nut crops (high protein content!) and some tree crops, relatively large amounts of nitrogen are harvested (200 to over 400 lb of nitrogen per acre per year). Fertilizer applications must be somewhat higher than the amount of nitrogen removed in the harvest. The over-application depends on many factors including what crop is grown, the soil type, the irrigation type, management practices, and a grower's tradition. Under good management practices, fertilizer applications are 120% to 150% of the amount harvested, although it is common that fertilizer nitrogen applications (including compost and other organic waste amendments) are 200% or more of the nitrogen harvested.
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