Download the latest Smart Farming Soil Fertility Guide |
![]() | By soil testing, you can save €23/acre on fertilizer.1 This is on land with high P and K levels (Index 4) and stocked at 2 dairy cows/ha (0.8cows/acre) |
![]() | The annual cost of soil sampling is roughly 50 cents/acre/year.2 This is the same cost as 0.5 units/acre of P fertilizer |
Low soil pH will result in:
1) lower availability of the nutrients in the soil, and
2) poorer response to applied fertilizers.
![]() | Soils with P Index 3 will yield more grass DM than a soil in P Index 1. Approximately 0.6t/acre (or 1.5t/ha) This extra grass could be worth approximately €180/acre. |
What does “Soil Index” mean?
The soil Index system takes soil test results and simplifies them to show if a soil is either, low, medium or high in fertility for each nutrient.
The soil test report shows the “soil Index” for each nutrient.
The Index is given as a number: either 1, 2, 3 or 4.
Index | Description | Action Required |
1 | Very low | Sub-optimal fertility. Apply fertilizers to increase soil fertility levels as well as to feed the grass or crop. |
2 | Low | Sub-optimal fertility. Apply fertilizers to increase soil fertility levels as well as to feed the grass or crop. |
3 | Medium | Optimum fertility level. Aim to maintain soil in Index 3. Apply fertilizers to replace the nutrients removed by crops or animal produce. Only approximately 25% of soils are currently in Index 3. |
4 | High | High fertility level. Soil has more nutrients than required to grow the crop. Additional fertilizers are usually not required, as the soil nutrients are sufficient to feed the crop. The risk of losses to water is also increased. |
Index 1 and 2 soils (low fertility) will be underperforming and need to be improved by applying fertilizers.
Index 4 soils are a resource on your farm. Exploit them and save money on fertilizer.
A field might be Index 3 in one nutrient, but be low or high in another nutrient. Look at the requirements for each nutrient in each field individually.
![]() | Slurry spread efficiently could save you €27 per 1000 gallons |
Think about the nutrient value of manures produced on the farm in terms of a 50kg bag of chemical fertilizer:
Manure Type | Units | Value5 | ||
N | P | K | € | |
Cattle slurry (1,000 gals) | 6 | 5 | 38 | 27 |
Soiled water (1,000 gals) | 4 | 0.7 | 5 | 5 |
Pig slurry (1,000 gals) | 19 | 7 | 20 | 27 |
Farmyard manure (1 tonne) | 3 | 2.5 | 12 | 10 |
Broiler litter (1 tonne) | 11 | 12 | 24 | 30 |
Spent mushroom compost(1 tonne) | 3 | 5 | 18 | 16 |
![]() | If you are spreading slurry, ask yourself: “Would I be spreading bag fertilizer in this field if I wasn’t spreading slurry?” If the answer is no, then the slurry is not saving you money on fertilizer! |
Use slurry more effectively to save on fertilizer costs and to reduce losses to the environment.
Consider sourcing manures and slurry from other farms to save on fertilizer costs.
![]() | Spreading manure and slurry – Two Simple Questions: 1) Where to spread? 85% of the value of slurry comes from the P and K. Identify fields that have a requirement for the P and K in the manure/slurry. 2) When to spread? During the open season when losses of N to air are at their lowest (lower temperatures, moist weather). Spring is ideal! |
![]() | Target cool moist conditions to reduce nitrogen losses to the air. Aim for spring application. Cattle slurry applied in spring is worth €1.80 more per 1000 gallons than slurry spread in summer |
Where feasible, band spreader, trailing shoe, and injection application methods also improve the N availability after application.
![]() | What is meant by a “compound” or “straight” fertilizer? Compound fertilizers (also called NPK fertilizers) are mixtures of nutrients, usually N, P and K. The name of the compound reflects the % of N, P and K in the product. For example, 18-6-12 contains 18% N, 6% P, and 12% K. A 50 kg bag of 18-6-12 will supply 18 units of N, 6 units of P and 12 units of K. Straight fertilizers contain only one nutrient. Examples include CAN (27% N), Urea (46% N) and Muriate of potash (50% K). |
The grass or crop yield will be limited by the nutrient in the shortest supply. Excess application of one nutrient is wasteful if yield is being restricted by another nutrient and also increases the risk of runoff to water with the potential to cause water pollution.
Think of it as a barrel of water where each plank is a nutrient and the water level is the yield. The level of water can’t get higher than the shortest plank in the barrel, no matter how high the other planks are!
Consider using a variety of fertilizer types that suit your farm. Straight chemical fertilizers may be more suitable than compounds in some circumstances.
For example, if a field is very high in soil P fertility, straight N and K fertilizers or a compound fertilizer with no P would be a good choice to meet the N and K requirements without spending on unnecessary P.
![]() | Remember fertilizer is not just a product in a bag! Other sources of nutrients that can fertilise your grass and crops include nutrients in the soil, in manures and in slurry. These should be managed to ensure that all nutrients on the farm are recycled as efficiently as possible, and that the money you pay for chemical fertilizer is money well spent! |
Footnotes
Download the latest Smart Farming Soil Fertility Guide |
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