N min
Under N min is defined as the content of a soil of available mineralized nitrogen .
N min method
With the N min method, a need-based amount of nitrogen fertilizer is usually determined for agricultural soils in spring. With this research method , the plant-available, currently mineralized nitrogen in the soil is determined by evaluating soil samples . The advantage of the method is a relatively exact recording of the mobile nitrogen content, which can be directly absorbed by the plants. Depending on the mineralization rate, this value will later be greatly changed during the growth phase of the plants due to the further temperature and moisture profile in the soil. This must be taken into account when fertilizing. If necessary, the mineralization can be estimated using an agro-meteorological forecast model.
In order to be able to make a meaningful fertilization recommendation, the soil samples for the N min analysis must be taken up to the root depth. The plant-available nitrogen is very mobile in the soil and is shifted to deeper layers when it rains and is transported to the surface by capillary action when it warms. For sampling up to a depth of 90 cm, the Pürckhauer boring tool is available for manual removal, and various variants are used for mechanical removal. In order to be able to precisely determine the N min content in the soil at the time of sampling , the samples taken must be brought to a soil laboratory immediately after they have been taken or temporarily stored at a temperature of 2–4 ° C. Otherwise the activity of microorganisms can lead to an increase in the N min value.
N min sampling with Pürckhauer boring stick
N min sampling with a light vehicle equipped with a generator, electric hammer and pulling device
N min samples must be protected from heat and solar radiation in insulating boxes in order to be able to make a meaningful fertilization recommendation.
The detection of the N min content in the soil enables economical, needs-based fertilization , avoids consequential damage from nitrate leaching into the groundwater and increases the quality of the plant culture - avoidance of over-fertilization (e.g. stored grain ).
Determination of the fertilizer requirement
If a crop like sugar beet is to receive 150 kg nitrogen / ha (target value), the N min value of the soil must be subtracted (for example 60 kg / ha). The result is the amount of fertilizer (90 kg nitrogen / ha) that has to be applied.
The Nmin target values are determined for most types of plants in fertilization trials. These target values can vary regionally depending on the expected yield and the local conditions. It is therefore recommended to correct the Nmin setpoints for grain, potatoes and maize with site-dependent surcharges or discounts. A system of crop-specific Nmin target values was developed for the cultivation of vegetables, which takes into account the special requirements of horticultural crop production.
Protected Areas and Compensation Ordinance in Baden-Württemberg
The Protected Areas and Compensation Ordinance (SchALVO) has been in force in Baden-Württemberg since 1988. This ordinance was amended on March 1, 2001 and regulates the protection of groundwater against impairment through the input of substances from land management. In particular, it is stipulated that fertilization and plant protection measures must be carried out in accordance with good professional practice in water protection areas. As part of the SchALVO, certain nitrate-soil values must be observed. Every year from October 15 to November 15, the soils are checked for nitrate residues. If the N min monitoring values are exceeded, this results in orders or requirements.
See also
Web links
- Nitrogen fertilization according to the N setpoint systems - Nmin, KNS and N-Expert. Retrieved July 4, 2013 .
- Bavarian State Institute for Agriculture
- Protected Areas and Compensation Ordinance (SchALVO)
Individual evidence
- ↑ G. Baumgärtel et al .: Recommendations for nitrogen fertilization according to the Nmin method. 2010. (online) ( Memento of the original from May 29, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ C. Feller, M. Fink, H. Laber, A. Maync, P. Paschold, HC Scharpf, J. Schlaghecken, K. Strohmeyer, U. Weier, J. Ziegler: Fertilization in outdoor vegetable cultivation. In: M. Fink (Ed.): Series of publications by the Leibniz Institute for Vegetable and Ornamental Plant Cultivation (IGZ). 3. Edition. Issue 4, Großbeeren 2011. (online)
