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Fertilizer requirement assessment - you have to consider that!
Katharina Rösner
The fertiliser requirement assessment stipulatiing limits in the context of Fertiliser ordinance (DueV) that you have to comply with. In this article, you can find out how to determine demand and what will change in 2025.
Every plant crop has an individual need for nutrients. Elementary are nitrogen and phosphate. So that too much of it is not applied to an area, there are minimum values for good yields and maximum values, to spare around the environmental as far as possible. Because the nutrient surpluses are washed out and get into groundwaters. Before fertiliser can be applied, the requirement must be precisely determined and documented. There are online tools or Excel templates that can be used to determine fertilisation requirements. The printout is considered as proof during an operational inspection. The documentation is obliging according to the fertiliser ordinance. Before fertilising, a soil sample be taken. If it delivers a value below the requirement limit, fertilisation may be carried out. The quantity available in soil, which is Nmin-Value, is deducted from the specified requirements of a plant crop. From 2025 on, these values will no longer be published by the Chamber of Agriculture. The cut-off date for determining the fertiliser requirement for the current fertilisation year is March 31.
Plants require potassium for resistance to pests, phosphorus for generative growth and nitrogen for vegetative growth. Some plants need more phosphate than others, such as spinach, potatoes or corn, to the rooting system to be able to train. Using nitrogen, they produce protein. It is particularly important at the initial stage of growth. For the photosynthesis and respiration plants need energy that they draw from it. Too little phosphorus causes small fruits, thin stems and root system as well as for leaf discoloration. Grass for grazing animals that has received too little phosphate also provides animals with a poorer source of nutrients. Most phosphorus from fertiliser It is bound in the soil while only a small part gets into the plant. Too much phosphorus harms both the plant and the soil.
The reason why fertiliser is necessary are the monocultures that are planted in agriculture. Their biological one-sidedness leaches the soil. There is no nutrient exchange taking place so that fertiliser is required. This also leaches the soil, which is why even more fertiliser must be brought in. On the other hand, a soil on which different plants grow at the same time exchanges various nutrients with them. Therefore, these soils are of better quality and do not require fertiliser.
One distinguishes mineral fertilisers and organic farm manure. The former is synthetic artificial fertiliser. The excessive use causes nutrient-poor soils. In addition, residues can also enter water bodies and thus into the water cycle. Producing mineral fertilisers is also resource-intensive because it requires crude oil and natural gas. They also contain heavy metals, which pollute the soil and then enter the food chain. The use of nitrogen, phosphorus and potassium is one-sided and represents an intervention in the natural composition of the soil.
In contrast, organic fertilise, to which manure, compost and manure belong. Harmful heavy metals, however, can also be contained in farm manure (= manure) and sewage sludge. Manure is also valuable in itself fertiliser because it is not synthetic and contains all the nutrients that plants need. However, it is important to avoid putting too much of it on the field.
The fertiliser requirement assessment is used to precisely calculate demand of nutritients that plants have. The fertilisation requirement is based on income value off. This is based on the average of the actual income value of the last 5 years. From the requirement the amounts of nitrogen are deducted, which at the start of the culture are located as available quantity in soil. This NminValues will no longer be published as of 2025. So far, the mean values from recent years have been calculated. Alternatively, this amount of nitrogen available in the soil can be determined by sampling. According to the Fertiliser Ordinance, the red areas must have the Nmin determined themselves. The quantities that are still available from organic fertilisation in the course of vegetation are also deducted from this. There are online tools for calculating fertiliser requirements. For this purpose, the operating yield level is entered in decitons per hectare (dz/ha) and the reference demand value of the crop is entered according to the DueV. Discounts are then made, i.e. demand is reduced.
Once you have calculated the nitrogen requirement in this way, it can only be exceeded by a maximum of 10 percent become. Especially in polluted areas, it is important to only add as much fertiliser to the soil as the plants need. However, there is often an excess of nitrogen in the soil, which is washed out and gets into groundwater. The fertilisation ordinance allows surpluses of up to 50 kg per hectare, but a maximum of 30 kg would be better. There is also criticism that farmers receive money to dispose of manure and that too many animals are kept, so that too much manure is also produced. For this purpose, it is imported from abroad. The regulation does not take the step of limiting the number of farm animals to the resulting compatible quantity of manure. In addition, antibiotic-resistant germs also enter the nutrient cycle via manure.
2020 amendments have been made to the fertiliser ordinance. In addition, the Fertilser Ordinance (DüV) committs state governments to declare red and yellow areas in the ”regional backdrop“. Red fields are nitrate-polluted areas and yellow ones encumbered with phosphorus. For them stricter requirements then apply. The Fertiliser Ordinance of 2020 requires that regions with polluted soils before fertilisation samples to take whether there is a need at all. In red areas, the available nitrogen in the soil must be measured by sampling every crop planted, including catch crops. The removal is at least 6 weeks after the last processing.
The blackout periods for fertilisation had already been prolonged in 2020:
In addition, the nitrogen requirement for the current fertilisation year must be determined and recorded by 31 March. There is a limit of 170 kg nitrogen/ha for one stroke. The phosphate requirement must be checked at least every 6 years or after each crop rotation in order to avoid an excess. However, this does not apply to the yellow areas. If certain values of phosphate are exceeded, only as much as is expected to be removed may be entered. These values are 20 mg per 100 g of soil using the CAL method, 25 mg using the DL method or 3.6 mg using the EUF method.
Since 2025 agricultural manure may only be entered with towing shoes or tubes. Namely, with the maximum of 20 cm away from the ground and in strips so that 50 percent of the area remains free from fertiliser. Ideal is the injection into the soil. Alternatively, it is only allowedto incorporate the fertiliser into the soil after one hour at the latest. That applies to permanent grassland, grassland, multi-cut forage crops such as grass or clover and cultivated arable land. Catch crops also belong to the ordered arable land. These measures are intended to ensure that the distribution is environmentally friendly. This means that the plants take up the nitrogen efficiently and less of it is washed out. In addition, ammonia emissions will be reduced.
Fines In the event of violations of requirements regarding blocking periods and upper limits, for example, amount to up to 150,000 euros.
Plants absorb nitrogen in combination with oxygen - i.e. as nitrate, that can pollute groundwater. The limit value for nitrate is 50 mg per liter of drinking water according to the EU Groundwater Directive on drinking water quality, which was also adopted by Germany in the same way. The EU also has its own nitrates directive. The limit is based on the needs of vulnerable groups, more specifically infants, who are more sensitive to nitrate than adults: it reduces oxygen transport in the blood. This value is also not increased to protect this group. If the three-quarter limit is reached, authorities must already take countermeasures.
A distinction must be made between drinking water, which is the most closely monitored foodstuff in Germany, and groundwater. There are many areas that are polluted with nitrate due, among other things, to agricultural land management. This value increased in 2016 because more measurement stations were set up. The value could then be reduced slightly. Where groundwater is withdrawn for drinking water without meeting the quality standards, it must be treated accordingly. For that water supplier are responsible. The individual countries commission water supply authorities and the health departmentwho are then responsible for the measures.
Nitrate polluted groundwater must therefore be purified. The more complex the process is, the more expensive it becomes. Drinking water supply therefore becomes more expensive for consumers when too much nitrate from used agricultural area is washed out and comes into groundwaters.
Alternatives to fertiliser can be intermediate sowing, permacultures or agroforestry. In the former, legumes are planted, for example, which reenrich the soil with nutrients. The second aims for a natural ecosystem in the soil, i.e. several plant crops are planted at the same time. However, this is necessarily done by hand, just like harvesting, which is not so easy for large companies. With the latter, trees are planted, which should have the same effect and also protects the soil from erosion. Small businesses may have the advantage that they keep fewer animals and so less manure is produced.
The Fertiliser ordinance regulates the use of fertiliser to improve agriculture as far as possible environmentally friendly to design. It also regulates the Fertilizer requirement assessment, which can be used to precisely determine the nutritional requirements of a plant crop. This is not only better for soils and groundwater, but is also cheaper. When it comes to organic farming, small farms can have an advantage.
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