Since the introduction of the nitrates regulations in 2006, the application of nitrogen and phosphorus has been controlled and maximum application rates apply. A temporary exemption applied to pig and poultry manure and spent mushroom compost. This enabled farmers to apply phosphorus levels that were surplus to crop needs (potash is not controlled) and many farmers availed of this opportunity to improve soil fertility.

The option to do this was enabled by a transitional arrangement in the Good Agricultural Practice for Protection of Water Regulations (SI 31 of 2014). This arrangement allowed farmers to apply phosphorus in excess of crop requirement by 3kg/ha if it was applied from either pig or poultry manure or spent mushroom compost.

This temporary concession ended in December 2016 and it has implications for farmers who produce and use pig slurry, poultry manure or spent mushroom compost from this year onwards. Some may be considering using these products ahead of planting this spring, so it is essential to be aware of your phosphate allowances and the amount being applied through organic sources.

This also makes it important for farmers who import slurry/manure/compost to know exactly how much they can use/import at the start of the year without exceeding the restrictions on organic nitrogen from livestock manures (170kg/ha) or phosphorus (where the allowances are crop, soil and productivity dependent). This means getting the calculations done early in the year to ensure that you do not exceed allowances.

A crop allowance can be supplied by any combination of artificial or organic sources but the total applied should not exceed the combined farm allowance. Checks on limits that apply are calculated on a whole farm basis rather than an individual field basis. High application rates of high P organic manures must be taken into account when purchasing and applying artificial phosphorus.

Nutrient loading

The value of livestock manures relates to how much chemical fertiliser can be replaced and, to a fair degree, the equivalent cost of chemical nutrients. Teagasc put the fertiliser value of pig manure at 4.3% solids at €5.59/m3 where there is a requirement for N, P and K (Table 1). This translates into €25.37 per 1,000 gallons. A reasonable rule of thumb is that a thousand gallons of pig slurry is equivalent to a bag of 19:7:20. A lorry tanker carrying 25m3 (5,500 gallons) can be valued at €145 at 4.3% solids.

It is important to value all the nutrients in your fertiliser programme because that is what a cross-compliance nutrient inspection will do. The figures in Table 2 provide an indication of the official nutrient availability in different sources of organic manure. From this, you can see that 1,000 gallons of pig slurry supplies 19.1 units of N, 7.3 units of P and 17.3 units of K. Ten tonnes of farmyard manure supplies 27 units of N, 24 units of P and 120 units of K. Or three tonnes of layers litter (55% DM) supplies 69 units of N, 33 units of P and 72 units of K.

While Table 2 shows the official numbers, where these manures are applied to Index 1 or 2 soils the available P can be taken as half the amount supplied. The balance of the P does not have to be accounted for in the year of application but it will help to raise soil levels over time and will be reflected in soil test results over time.

Cost v value

For farmers, the application of any of these organic fertiliser sources can greatly reduce the requirement for artificial or bagged fertiliser. But the economics obviously depends on the transport cost involved. Cost is further influenced by the size of the transport vehicle and the distance involved. Teagasc estimates for the transport cost of pig slurry are shown in Table 3.

This provides a summary of the costs associated with a 3,000-gallon slurry spreader (based on a contractor cost of €50/hour) and 6,000-gallon lorry delivering slurry to a storage tank (using a cost of €72/ hour).

Similar evaluations need to be done for the different litters and composts but the numbers and distances will differ considerably due to the higher dry matter content and different bulk density of these products. A more complete evaluation of the content and value of different organic manures (based again on 2016 prices) can be seen in Table 4.

The technical value of slurry or manure must be calculated based on its ability to supply nutrients to your farm/field but their value to worn tillage land can be considerably higher than that, especially on low index soils. However, getting good value from this, or any fertiliser source, is dependent on having your soil pH high enough to make optimum use of all nutrients.

It is also important to try to place individual products with appropriate crop uses. Using high quantities of N-rich products in the autumn can lead to soft growth and increased challenges from diseases such as mildew.

In all instances, the ending of the derogation means that the maximum that can be applied is governed by the phosphate allowance of the farm/field. If you only grow winter barley and your highest recent yield was 10 t/ha, your P allowance is 38kg P/ha if your soil is Index 3, or 48kg P/ha at Index 2.

If you only grow one crop and you have no other land use then your total P usage per hectare cannot be more than these numbers.

  • New regulations pertaining to the importation of pig manure and poultry litter came into effect on 1 January 2017.
  • The phosphorous use allowance – tillage or grass – depends on many factors.
  • For tillage farmers, the maximum crop allowance for P in particular must not be exceeded by the combined application of organic and artificial fertiliser sources.
  • Grass farmers must also comply with the total organic nitrogen threshold of 170kg/ha but this is highly unlikely to be a practical constraint on tillage-only farms.
  • On livestock farms, no “livestock manure” may be imported if the intensity of stocking is above the equivalent of 170kg N/ha.
  • The availability of organic P is considered to be only 50% when applied to soils with a P index of 1 or 2. So if you have low P levels in your soils, you can use twice as much phosphorous from organic sources providing you do not exceed the organic nitrogen allowance. The applied nitrogen levels, which are stated in these tables, must also be accounted for.
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