Table 4 Definition of the parameters in Eq. 1 for determining N fertilizer requirements with calculation example for high quality backing winter wheat according to Submodule 3.2
From: Web-Man – a new software for web-based nutrient management in organic farming
Parameter | Example | |||
|---|---|---|---|---|
Symbol | Name | Explanations | Data | Calculation [kg ha−1 N] |
FNR | Fertilizer N requirement | N fertiliser requirement, based on plant-available nitrogen | 64,0 | |
NRcor | N requirement, corrected | Crop and yield-specific N requirement, based on fertiliser application ordinance (BMEL 2021); Backing winter wheat has a fertiliser requirement value of 260 kg ha−1 N for a yield of 8 t and 15 kg h−1 N are deducted per t) | Backing winter wheat, yield level 5 t ha−1 | 215,0 |
SCI | Consideration of soil and climatic conditions | Soil and climatic conditions are taken into account with a surcharge or a discount + adjustment of the N requirement to the target yield and protein content (Kolbe 2022a) | Loess soils in the transitional areas (east), Adaptation of N contents to organic farming | −75,0 |
SMN | Soil mineral N stock at vegetation start | Soil mineral N stock determined by soil samples and laboratory analyses at the start of vegetation in spring | SMN 0–60 cm: 2% stone content SMN 60–90 cm: 90 cm rooting depth | −24,0 −4,0 |
SDpc | Subsequent delivery of the previous crop | N supply from crop residues and roots of the previous crop during the cultivation period of the winter wheat | Clover grass, clover content 30% | −18,5 |
SDppc | Subsequent delivery of the pre-preceding crop | N supply from crop residues and roots of the pre-preceding crop during the cultivation period of the winter wheat | Clover grass, clover content 30% | −6,4 |
PD | Plant development | Plant development is taken into account depending on the EC stage and plant density | EC-Stage 22 Plant density: normal | −3,0 |
OF1-4 | Organic fertilization in the last 4 years | The N-mineralization of organic fertilizers of the last 4 years is estimated and deducted from the fertilizer requirement | Organic fertilization from previous years | −10,0 |
OFa | Organic fertilization autumn | Organic fertilization already applied in autumn is deducted from the fertilization requirement | No organic fertilization in autumn | 0,0 |
CC/GM | Catch crop/green mass | Additional supply from catch crops and harvest residues | Harvest residues | −10,1 |
WPA | Consideration of the water protection area | If the field is located in a water protection are: limit the fertilizer requirement to 0 kg ha−1 N | No water protection area restrictions | 0,0 |
GFO | Consideration of GFO | The fertilizer recommendation must not exceed the legal regulations | Fertilizer recommendation is below the legal limit (177 kg ha−1 N) | 0,0 |