Planned crop yield volume, removal of nutrients by plants, content of available nutrients in soil, type and texture of soil have to be considered in order to estimate the amount of fertilizer that has to be applied.
Regional fertility rate achieved, climate conditions and natural soil fertility should not to be neglected as well.
In practice, the demand for nutrients is characterized by their removal by plants considering the by-products as well.
In practice, the demand of plants for nutrition elements is characterized by the nutrients’ removal. Removal is the amount of nutrients taken away from soil with the yield practically harvested ( for instance with the grain) including the by-products (for instance, chaff) and excluding the plant residues left on the field (for instance, roots and stubble) (see Removal).
Removal of major nutrients with the crop yield
|
Crop | Major production |
Removal with 1 t of yield and the corresponding amount of by-products, kg |
| N |
P2O5 | K2O |
CaO | MgO |
|
Ensilage corn | Green material |
3,3 |
1,2 |
4,2 |
1,3 |
1,0 |
Below are approximate indexes of the consumption of nutrients from soil and from fertilizers by corn plants that can be used to estimate the amount of mineral fertilizers for sod-podzol and gray wood soils.
Indexes of the consumption of nutrients from soil and fertilizers by plants (for sod-podzol and gray wood soils), %
|
Crop | From soil (with medium and higher nutrients content)* |
From mineral fertilizers during the first year | From organic fertilizers during the first year |
| P2O5 |
K2O | N |
P2O5 | K2O |
N | P2O5 |
K2O |
| Grain crops, annual and permanent grasses |
5 | 10 |
50−60 | 15−25 |
40−50 | 20 |
30 | 40−50 |
*The indexes can be one and a half or two times as much by low nutrients content in soil.
Example of estimation of amount of mineral fertilizers required in order to achieve the planned crop yield of winter wheat, ensilage corn and sugar beets.
|
Index |
Winter wheat |
Ensilage corn | Sugar beet |
|
N | P2O5 |
K2O | N |
P2O5 | K2O |
N | P2O5 |
K2O |
| Planned crop yield, c/ha |
40c/ha |
400 c/ha |
400 c/ha |
|
Removal of nutrients with the planned yield, kg | 115 |
45 | 80 |
132 | 50 |
168 | 160 |
65 | 260 |
|
Nutrients taken up from soil |
30 | 15 |
30 | 30 |
15 | 30 |
30 | 15 |
60 |
| Taken up from 60 t/ha of organic fertilizers, kg | - |
- |
- |
50 | 25 |
80 | 60 |
30 | 120 |
|
Mineral fertilizers required, kg/ha |
85 | 30 |
50 | 55 |
10 | 60 |
100 | 20 |
80 |
| Consumption of nutrients from mineral fertilizers, % |
65 | 20 |
50 | 65 |
20 | 50 |
65 | 20 |
70 |
| Amount of the major nutrient that should be applied with mineral fertilizers considering the consumption indexes, kg/ha |
130 | 50 |
100 | 85 |
50 | 120 |
107 | 100 |
115 |
| Amount to apply for ammonium nitrate, kg/ha |
370 | * |
* |
245 | * |
* |
305 | * |
* |
* Application dose (Dappl.) for various types of phosphorus and potassium fertilizers is estimated in accordance with the content of nutrition elements (e) in them using the following formula: Dappl. = (х*100)/e. Where х – dose on primary nutrient basis.
High yield grain crops with good quality characteristics are mostly influenced by the system of nitrogen fertilizers application.
