Maximum Yield Australia/New Zealand March/April 2023 | Page 40

Ammonium-N is often incorporated into hydroponic nutrient products and formulations specifically to produce a pH buffering effect . In hydroponic systems pH tends to gradually increase as the plants take up nutrient ions , requiring acidification for pH control . Ammonium-N reduces the rate of pH increase , giving a greater buffering capacity to pH change in the nutrient solution and slowing or preventing the natural rise in pH that occurs over time . The uptake of ammonium by roots can result in a lowering of the pH in the nutrient solution as plants release positive hydrogen ions to balance the change in the root zone . For systems which may be using a hard water source that has a high alkalinity and thus requires a greater volume of acid to keep the pH down and within range , this pH buffering effect of ammonium-N can be particularly useful .
Nitrogen Fertiliser Sources
Overuse of nitrogen in the fruiting stages should be avoided to maintain a good vegetative / generative balance .
In traditional hydroponics , nitrogen sources include the fertiliser calcium nitrate , potassium nitrate , ammonium nitrate , ammonium sulphate , and ammonium phosphate , however , with the increased interest in organic hydroponics , aquaponics , and various natural supplements such as amino acids , nitrogen can be added via several different compounds . What is important to understand is that organic sources of nitrogen supply the exact same N ions for plant uptake as chemical fertiliser . Whether the nitrogen has originated from an organic material , or amino acid solution , or from a chemical fertiliser , the plant roots all take up the nitrogen in the same format as plant-usable nutrient ions , nitrate , or ammonium . The only difference is the organic material , solution , or additive must be first broken down by microbial action to release nutrient ions into a form plants can take up . This form is exactly the same as the nitrogen forms supplied by fertiliser salts . With organic nitrogen sources having this requirement for microbial break down , or ‘ mineralisation ,’ before they become available for plant uptake , organic nutrients or supplements need some specific conditions for use as nitrogen sources . These must either be processed by microbial action before being used in the hydroponic system , so the nitrogen sources are readily available for immediate uptake , or undergo mineralisation after being added to the system . Use of biodigester systems , composting , and vermiculture ( worm farm ) systems are all forms of pre-processing organic nitrogen sources via ammonification and nitrification
Careful and balanced use of the ammonium form of nitrogen can give a growth boost to winter-grown greens .
by microbial action . Small additions of organic nitrogen sources such as amino acid supplements can be successfully used in many hydroponic systems , as microbes naturally exist in soilless systems which will break these compounds down and release the nitrogen for plant uptake . This process , however , is somewhat slower than using traditional fertiliser salts which immediately dissociate when dissolved into water to give plant-available nitrogen for rapid root uptake . So , correcting a nitrogen deficiency in a hydroponic crop is much more speedy and accurate when using traditional hydroponic fertiliser than if organic materials are to being used .
Understanding how the different forms of nitrogen are utilised inside the plant and how this can be used to a good advantage is one of the many skills hydroponic growers can use to their benefit . While an excess of ammonium-N can potentially be quite damaging to plant growth , a certain level — applied under the right conditions — can work to boost growth and help buffer changes in pH in the nutrient solution . Recognising the signs and symptoms of the overuse of ammonium-N is another important lesson as problems such as leaf damage , tip burn , and blossom end rot caused by ammonium toxicity are not always correctly identified . Experimenting with nitrate-to-ammonium ratios for different crops and under different growing conditions is one way of maximising the potential benefits of these nitrogen sources .
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