2019 Year 12 IB Extended Essays

Research Question: What is the tolerance of grain crops to nitrates and salinity and how can this be used to determine suitability and dilution levels of grey water for use in treating saline soil and growing commercial grain crops?

Background Research:

What is greywater? Greywater refers to the waste water produced by a household that contains a low organic load compared to sewage (Sustainable, 2018). It includes dirt, hair, food particles and a range of various washing solutions (Greywater Action, 2018). Modern detergents have a high amount of nutrients in the form of nitrates and as there is a high level of detergents in greywater, it can be used as a method of fertilisation (Metrowater, 2018). How do plants use nitrates? Plants absorb nitrates from the soil in the form of nitrates. These nitrates are used to grow their foliage and also to develop their seeds and flowers. The nitrogen is also a key component of proteins within the plant and also plays a role in photosynthesis as they also make up the chlorophyll. How do high levels of Nitrates affect plant growth? As plants use the nitrogen present in Nitrates to produce chlorophyll, if the levels of nitrates are increased, then the plant begins to increase its foliage size to maximize area for the pigment to occupy. But as all the energy produced by the plant is being used to grow the leaves, the roots and reproductive organs don’t receive any energy, slowing the root growth rate, making it more likely for the plant to get uprooted. Immature reproductive organs could mean that the plants will be unable to produce seeds and therefore will be unable to multiply. If the high nitrate level remains constant over a period of time, then the plants could develop leaf burn, whereby the nitrate salts get accumulated in the leaves, causing them to yellow and wilt (Rodriguez, A, 2019). High levels of Nitrate could also have the same effect as salt, with osmosis causing the water from within the plant to get drawn from a

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