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Copy link Polysulphate Alfalfa Trial
10
Crude protein
Polysulphate improves the nitrogen content of alfalfa (lucerne) fodder, while at the same time improving the N:S ratio and the digestibility of fodder.
UK 2017
10
Key Conclusions
Polysulphate fertiliser improves nitrogen content of alfalfa, while at the same time improving the N:S ratio and the digestibility of fodder by 40%.
Objective
To investigate the effect of the application of Polysulphate on the nutritional quality of alfalfa, or lucerne (Medicago sativa). Specifically, to increase the S level and improve (tighten) the N:S ratio with the objective of increasing crude protein and improving digestibility.
Trial Details
Trial station
UK
Crop
Alfalfa
Product
Polysulphate®
Assessments
N:S ratio, crude protein, and digestibility
Treatments
- This was a split field trial.
- A standard broadcast spring application of a phosphate and potash (PK) fertiliser was compared with a treatment providing the same PK inputs, plus sulphate, magnesium, and calcium from Polysulphate.
- The nutrient application rates are shown in the table below.
| N | P2O5 | K2O | MgO | SO3 | CaO | |
|---|---|---|---|---|---|---|
| kg/ha | kg/ha | kg/ha | kg/ha | kg/ha | kg/ha | |
| Standard PK | 0 | 80 | 120 | - | - | - |
| PK+Polysulphate | 0 | 80 | 120 | 12 | 96 | 34 |
Treatments
- This was a split field trial.
- A standard broadcast spring application of a phosphate and potash (PK) fertiliser was compared with a treatment providing the same PK inputs, plus sulphate, magnesium, and calcium from Polysulphate.
- The nutrient application rates are shown in the table below.
| N | P2O5 | K2O | MgO | SO3 | CaO | |
|---|---|---|---|---|---|---|
| kg/ha | kg/ha | kg/ha | kg/ha | kg/ha | kg/ha | |
| Standard PK | 0 | 80 | 120 | - | - | - |
| PK+Polysulphate | 0 | 80 | 120 | 12 | 96 | 34 |
Results
- The N:S ratio of 20:1 with the standard PK fertiliser was narrowed to the desired 12:1 by the Polysulphate treatment. An N:S ratio of 20:1 is considered too wide for optimal fodder digestibility and for maximum nitrogen use efficiency by ruminant livestock.
- The nitrogen content of the fodder (measured as ‘crude protein’) was improved by the Polysulphate treatment, indicating that an adequate sulphur supply is necessary to enable alfalfa to fix and utilise nitrogen efficiently.
Alfalfa fertilised with Polysulphate has a more desirable narrow N:S ratio.
Polysulphate fertiliser increased alfalfa’s crude protein content.
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