Summarize the steps of the water cycle.4/14/2023 ![]() ![]() Steps are being taken in agriculture to reduce phosphate losses in order to maximise the efficiency of fertiliser and effluent applications.The water cycle describes how water is exchanged (cycled) through Earth's land, ocean, and atmosphere. Excess phosphate causes excessive growth of plants in waterways, lakes and estuaries leading to eutrophication. This phosphate ends up in waterways, lakes and estuaries. When fields are overfertilised (through commercial fertilisers or manure), phosphate not utilised by plants can be lost from the soil through leaching and water run-off. For example, adding lime reduces soil acidity, which provides an environment where phosphate becomes more available to plants. In New Zealand, superphosphate is made using rock imported mainly from Morocco.Īdjusting the pH of the soil for efficient plant uptake of phosphate should be done prior to fertilisation. Locally produced sulfuric acid is used to convert the insoluble rock phosphate into a more soluble and usable form – a fertiliser product called superphosphate. The phosphorus is obtained by mining deposits of rock phosphate. Many farmers replenish phosphorus through the use of phosphate fertilisers. Phosphate fertilisers replenish soil phosphorus Therefore, farmers replenish the phosphorus ‘pool’ by adding fertilisers or effluent to replace the phosphorus taken up by plants. In addition, crops are usually harvested and removed – leaving no decaying vegetation to replace phosphorus. Many plant crops need more phosphorus than is dissolved in the soil to grow optimally. If soils are less than pH 4 or greater than pH 8, the phosphorus starts to become tied up with other compounds, making it less available to plants. This depends on the acidity (pH) of the soil. pH: Inorganic phosphorus compounds need to be soluble to be taken up by plants.Desorption is the release of adsorbed phosphorus from its bound state into soil solution. ![]() Adsorption: Inorganic (and available) phosphorus can be chemically bound (adsorbed) to soil particles, making it unavailable to plants.Although other bacteria make phosphate available by mineralisation, the contribution of this is small. Bacteria: Bacteria convert plant-available phosphate into organic forms that are then not available to plants.The availability of phosphorus in soil to plants depends of several reversible pathways: A lot of the phosphorus in soils is also not available to plants. Since most of our phosphorus is locked up in sediments and rocks, it’s not available for plants to use. Once there, it can be incorporated into sediments over time. Phosphorus in soil can end up in waterways and eventually oceans.Within the soil, organic forms of phosphate can be made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus.When the plant or animal dies, it decays, and the organic phosphate is returned to the soil. Once in the plant or animal, the phosphate is incorporated into organic molecules such as DNA. The plants may then be consumed by animals. Plants take up inorganic phosphate from the soil.This inorganic phosphate is then distributed in soils and water. Over time, rain and weathering cause rocks to release phosphate ions and other minerals.Here are the key steps of the phosphorus cycle Phosphorus moves in a cycle through rocks, water, soil and sediments and organisms. Insufficient phosphorus in the soil can result in a decreased crop yield. It plays a critical role in cell development and is a key component of molecules that store energy, such as ATP (adenosine triphosphate), DNA and lipids (fats and oils). Phosphorus is an essential nutrient for animals and plants. The role of phosphorus in animals and plants
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