S A about consequence of unscientific application of chemical fertilizers
Answers
consequence of unscientific application of chemical fertilizers
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. Nitrate is easily leached from soil and so presents the most opportunity for pollution.
Phosphorus
Phosphorus is a very stable element and moves only 1–5 mm from where it is spread. It binds quickly with soil minerals, so is unlikely to leach through soil except under high rainfall in very sandy soils. It is mainly lost from the soil by erosion when soil particles holding the phosphorus are blown or washed away. For this reason fertiliser phosphorus is unlikely to be a major contributor to phosphate pollution of waterways, unless erosion occurs.
Potassium
Potassium is taken up by plant roots very rapidly and is not used in great quantities, so represents little environmental threat. Bananas need large quantities of potassium and care needs to be taken to apply it in small amounts, often, so that the plant can use all of it.
Environmental hazards
Groundwater pollution
Nitrate leaching through the soil can present a serious health hazard and contributes to soil acidification. When high rates of nitrogen are used or where clover grass pastures fix substantial nitrogen, especially on sandy or permeable soils, inevitably some nitrate is leached and may enter groundwater if there is a watertable. If this groundwater is used for domestic supplies, the leaching presents a serious health hazard.
Eutrophication
Eutrophication is the enrichment of water by the addition of nutrients. The extra nutrients encourage the growth of algal blooms, particularly in stagnant water. Blue–green algae may produce toxins poisonous to animals, including humans. For this algae to grow, phosphorus must be present in the water above a certain level.
Phosphorus may be introduced into waterways in run-off from pasture, forests and fertilised land, and in drainage from irrigated land and urban areas. These sources, representing most of the total run-off, normally contribute low concentrations of phosphorus and are referred to as diffuse or non-point sources. Point sources, such as sewage effluent and drainage from dairies and feedlots, contribute smaller flows but contain much higher concentrations of phosphorus. These are frequently found to be the sources for most of the phosphorus found in waterways.
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.