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Guidelines for farmers in nitrate vulnerable zones

Booklet 2: Fertiliser and Manure Plans - Part 2 - Manure Planning

1. What are the farm and field based limits?

The NVZ Action Programme rules set farm based limits for the amount of total nitrogen that can be applied each year in the form of organic manures. These limits are set out on page 5 of the Introductory Booklet. The Table below provides a summary:

* Note: Although the farm limits are averaged over the whole of the grassland or non-grassland area, applications of organic N cannot exceed 250kg/ha on any individual field within any 12 month rolling period. This individual field limit excludes any grazing deposition.

These are annual limits calculated for the period 19 December to 18 December and apply to all organic manure and wastes (e.g. livestock slurry, FYM, poultry manure and sewage sludge).

The step-by-step guides on the following pages show how to calculate whether there is enough land available for spreading organic manures.

2. Is there enough storage for slurry?

The NVZ Action Programme rules prohibit the spreading of slurry, poultry manure or liquid digested sewage sludge on sandy or shallow soils for the period between:

• 1 October and 1 November in any year where the land is in grass or is to be sown with an autumn sown crop

• 1 August and 1 November in any other case

You will need at least enough storage to cover these closed periods. If you have insufficient storage to cover the closed periods or any other period when organic manures cannot be applied to your land, then you may be considered for a 40% grant under the Nitrate Vulnerable Zone Grant Scheme (NVZGS). In order to be eligible for the scheme you must have prepared a Farm Waste Management Plan. Further details of the Grant scheme are available from your SEERAD Area Office.

These restricted periods do not apply to FYM (straw based manures). For definitions of "sandy" and "shallow" soils see Booklet 3, page 3.

Closed periods are fully explained at page 6 of the Introductory Booklet.

3. How much will manure applications reduce the requirement for inorganic fertiliser nitrogen?

The amount of nitrogen available to the crop following the application of manure depends on the type of manure, the soil type, the timing and the method of application. Guidance provided in the PEPFAA Code of Good Practice gives details of application rates and the risks involved in spreading slurry.

• The surface application rate should not exceed 50m ³/ha (4500 gallons/acre), although in practice, application rates seldom exceed 30m ³/ha (2700 gallons/acre)

• Any repeat application should not be made within three weeks

• Inorganic nitrogen fertiliser applications must be reduced to allow for additional nitrogen supplied by manures

Calculation guide: Is enough land available for spreading all organic manures?

Step 1: Complete Table C, entering the appropriate details for each field within the NVZ.

• Enter each FID into the first column.

• Enter the area of each grassland field into column 'a'.

• Enter the area of each non-grassland field into column 'b';

• Enter 'no-spread' areas, as appropriate into columns 'c', 'd', and 'e'.

• Buffers = field areas within 10m of either side of any watercourse (including ditches and piped ditches) or within 50m of any spring, well, borehole similar water supply.

• Slopes = field areas on very steep slopes where there is a high risk of runoff throughout the year.

• Other = field areas where the requirements of conservation management prohibit applications of organic manures or where spreading equipment cannot be used effectively. Land that has never had manure applications is unlikely to be suitable for spreading.

Step 2: Complete the following calculations:

1. Total column 'a' in box 'A'. This gives you the total area of fields in grassland.

2. Total column 'b' in box 'B'. This gives you the total area of fields not in grassland.

3. Calculate the area of each field that is available for spreading organic manure by deducting the 'no-spread' areas from the total field area. Enter the result in column 'f'.

4. Calculate the maximum amount of organic N that can be spread on each field by multiplying the column 'f' figure by 250. Enter the result in column 'g'.

Step 3: Calculate the Farm-based limits for the total grassland and non-grassland areas on the farm, using the information derived from Table C. Adding the two limits together gives us the overall farm limit, which can be compared with the actual amount of organic N produced by livestock on the holding.

These farm-based limits include grazing deposition. If a field is likely to change from (say) grassland to non-grassland use during the year, then the predominant land use through the year should be used to determine the appropriate field category.

Note: The column 'g' figure in table C represents the maximum amount of organic N that can be spread on an individual field within any 12 month rolling period. This individual field limit does not include any organic N deposited by animals whilst occupying the field.

Careful planning is required to ensure that total applications do not exceed either the individual field limit, or the farm-based limits for grassland and non-grassland areas.

Step 4: Calculate the total N likely to be produced, by completing Table D.

• Record the number of livestock in each stock category.

• Multiply the number of stock units by the total nitrogen excreted by 1 stock unit.

• The total nitrogen produced by livestock on the farm is then the sum of the category values.

You will now have an estimate of the total Nitrogen that will be produced by livestock on the farm.

Note: You will have to re-calculate your figures if there is a change to your normal stocking, e.g. if additional animals are brought on for fattening.

The actual amount of N produced by livestock may vary, depending on diet and other details of the production system. These factors may be taken into account when calculating the actual amount of N produced on the holding. However, if you decide to use different N excreta rates, you should keep adequate records, e.g. slurry and FYM analyses and details of diet.

A simplified assessment of compliance with the limits can be undertaken using Table E. This uses standard figures, which represent typical nitrogen excreta rates for different types of livestock. The table converts these standard figures into the animal numbers per hectare that equate with the Farm Based grass and non-grassland limits.

Step 5: Compare the amount identified at Step 4 with the Overall Farm limit identified at Step 3.

If the amount of N produced exceeds the permitted application limit you will have to utilise the excess manure elsewhere.

Step 6: Analyse the figures in terms of current/proposed spreading practices.

Step 7: If you import organic manures (including sewage sludge or other non-agricultural organic wastes), calculate the amount of organic N that can be imported.

Note: It is a legal requirement to maintain acceptable records where organic manures are moved off the farm on which they are produced or where they have been brought onto a farm. The records must be kept for 5 years and include details of the quantities, dates and the recipient or supplier. Detailed guidance on record keeping is provided in Section 2 of the Introductory Booklet.

Worked Example: Is enough land available for spreading all organic manures?

Dairy Farm

Step 1: Enter details for each field on the holding into columns 'a' to 'e' of Table C.

Step 2: Complete the various calculations within Table C as shown below:

Farm code xxx/xxxx

Step 3: Calculate the Farm based limits

Step 4: Enter the numbers for each category of stock expected to be on the holding throughout the year, into Table D.

Step 5: Table D demonstrates that 12,744kg N are likely to be produced by livestock on the holding. This is within the overall Farm limit, previously identified at Step 3, but further analysis is required to determine where spreading can take place.

Step 6: Analyse the figures in terms of current/proposed spreading practices.

In our example all of the organic N is currently being applied to the grassland, either by way of grazing deposition or in the form of slurry/FYM applications. The total organic N production is 12,744kg, compared to a Grassland limit of 12,500kg. Continuing with the current grazing and spreading practices would therefore result in a breach of the Action Programme Rules. In this case the solution would be to apply the 'surplus' manure to the arable land.

Further planning will be required to determine the fields where the organic manure can be spread and at what rate it can be applied. The last section in this booklet takes you through the steps required for calculating how much will organic manure applications reduce the need for inorganic fertiliser nitrogen. The same steps can also be used to explore alternative application strategies.

Calculation guide - Is there enough storage for slurry?

Step 1: Calculate monthly slurry production

The quantity of slurry produced each month is calculated by completing Table F. If some of the excreta is collected as solid manure and stored separately estimate the proportion handled as slurry.

• Enter the number of stock against each category

• Enter the proportion of waste collected as slurry, if not 100%

• Multiply the number of stock by the proportion of waste collected as slurry and then multiply by the monthly volume of slurry produced

• Total the figures for the different stock categories

You will now have calculated the total volume of slurry produced each month.

Step 2: Calculate the volume of rain draining to the slurry store. Drainage from the following areas should be considered, if it drains to the slurry store:

Exclude runoff from clean yard areas and roof areas if it is collected and discharged into a clean drain. Similarly, rainwater that has passed across a fouled concrete yard, but is collected separately from slurry, is not regarded as slurry under the NVZ rules and can be spread at any time, on any soil, subject to the requirements of the PEPFAA code.

Step 3: Calculate dirty water production from other sources e.g. milking parlour/dairy washings or washing down pig pens

Note: Dairy/parlour wash water, that is collected separately from slurry, is not regarded as slurry under the NVZ rules and can be spread at any time, subject to the requirements of the PEPFAA code.

If you know the actual amount of dirty water produced from cleaning operations, then use the actual figures. If you do not know the actual figures, use the following figures, which represent the typical daily quantity of water produced during cleaning operations.

• For Dairy cows the typical daily production is 18 litres per animal/day.
  Monthly production (m ³) = (number of milking cows x 18 x number of days in month) ÷ 1000.

• For cleaning out pig pens after each batch of pigs (10 pigs per batch), the typical production is 18 litres/batch.
  Monthly production (m ³) = (number pens cleaned per month x 18) ÷ 1000.

Step 4: Calculate the slurry storage requirement

For the purpose of the NVZ Regulations, this step is only applicable if you are affected by the closed periods for spreading slurry, poultry manure and liquid digested sewage sludge on Sandy/Shallow soils.

The slurry storage capacity must be sufficient to store all of the slurry production that cannot be spread, due to the closed period restrictions.

A simplified approach to calculating your minimum closed period requirement is:

1) Calculate the amount of slurry produced from the start of housing to the start of the closed period = a
(this gives some allowance for a safety margin)

2) Calculate the amount of slurry produced during the closed period = b

3) The total minimum storage required to comply with the closed periods then equals a + b

This approach takes no account of the amount of land that is available for spreading during the closed period and you will have to consider this, if your calculations show that you have insufficient storage capacity. Similarly, you may have to consider whether additional storage will be required to cover the time from the end of the closed period to the end of winter housing.

Preparation of a Farm Waste Management Plan (FWMP) will help you to decide where, when and at what rates you can spread organic manures. This is not mandatory within the NVZs, but it will enable you to determine your storage requirements by balancing the amount of slurry that can be spread, against the amount of slurry produced on a monthly basis.

Step 5: Calculate the amount of storage available

To estimate the existing slurry storage capacity for a store which is:

• Square or rectangular with vertical walls:

• Multiply its length (m) by its width (m) by its height (m) (the height should be reduced by 0.3m to allow for freeboard as a safety margin against increased risks of pollution from storm events)

• Circular:

• Measure the circumference.

• Calculate the radius by dividing the circumference by 3.142, then dividing by 2

• Calculate the floor area by multiplying the radius by the radius, then multiply by 3.142

• Multiply the floor area (m ²) by the height (m) (reduce the height by 0.3m to allow for freeboard) to give the capacity of the slurry store (m ³)

• Earth banked lagoon:

• Estimate the length (m) and width (m) and average depth (m), from the top of the bank to the base of the lagoon

• Reduce the average depth by 0.75m to allow for freeboard and to give the watering depth

• Reduce the measured length and width of the lagoon by enough to allow for the sloping sides

• Multiply the adjusted length by the adjusted width by the watering depth to obtain the storage capacity (m ³)

Step 6: Compare the amount of available slurry storage, with the actual amount likely to be produced during the closed period. If the amount of storage available is less than the amount of slurry produced, you will have to review your current storage.

Calculation guide: How much will organic manure applications reduce the requirement for inorganic fertiliser nitrogen

This guidance takes you through the steps required to complete Table G. The table is completed in conjunction with typical values obtained from Booklet 4, which also contains guidance on its use.

Step 1: Record details of actual or planned organic manure applications

Record all applications for each field that receives manure. This should be done as soon as possible after the manure is spread. The data that needs to be recorded is:

• Field number/identification (enter in column a). Note: Leave enough lines below each FID to allow for the maximum number of applications that are likely to be made to each field.

• Soil type (enter in column b)

• Incorporation time, if applicable. Use the 'over 6 hours' or 'over 24 hours' figures, if there is no incorporation e.g. grassland that is not being ploughed up. (enter in column c)

• Manure type reference number (enter in column d)

• Season of application (enter in column e)

• Total area spread (often the same as the available field area). (enter in column f)

• Total quantity applied (tonnes or m ³) - see Appendix II of the Introductory Booklet for conversion factors from imperial units (enter in column g)

• Organic manure application rate. (= Quantity applied ÷ Field area) (enter in column h)

Step 2: Calculate available N in spring/summer after spreading organic manures

Using the information calculated above and the values in Tables A to D, you can now calculate:

• The nitrogen content of the manure (kg/t) (enter the value in column i). The total nitrogen application rate
  (= Manure application rate x N content of the manure) (enter in column 'j')

• The percentage of the manure's nitrogen that is available to the crop. (enter in column 'k')

• The nitrogen available to the crop (kg/ha) (= Total N application rate x % available N) (enter in column 'l'). This figure is entered as an adjustment in the Fertiliser and Manure Plan. The figure is entered as a negative adjustment into column 'c' of Table A or column 'j' of Table B

• The nitrogen available to the next crop (= 10% of the total N applied to the crop) (enter in column 'm'). This figure is carried forward to the next year's Fertiliser and Manure Plan and entered into column 'd' of Table A or column 'k' of Table B.

Step 3: Adjustment of the crop requirement for inorganic fertiliser

• The crop requirement for fertiliser nitrogen must be reduced by the amount of available nitrogen supplied by the organic manure application.

• The amount of available nitrogen must not exceed the nitrogen requirement of the crop.

Note: Table G can be used to record actual applications or for planning different application strategies.

Worked example: N available in spring, from livestock manure applications

The examples show how to calculate the values used in the Fertiliser and Manure Planning examples. It may be helpful to refer to 'N available from livestock manure applications', whilst reading through this example.

• Example 1: Spring barley crop grown for feed in a 3.83ha field, on 'OMS' soil. 115m ³ of 6% dry matter dairy slurry was applied to the field in March, prior to sowing and incorporated within 6 hours. 115m ³ of similar slurry was applied to the previous crop.

• Example 2: 15ha silage field on 'OMS' soil. 450m ³ of 6% dry matter dairy slurry was applied in the spring.

Step 1: Record details of actual organic manure applications.

• Columns a, b, c, e, f and g can be completed from the information above.

• The 'Ref. No.' in Column d is determined from the slurry type, the incorporation time and the % dry matter. In the case of the examples, the slurry type and dry matter content are the same, but the incorporation time is different. The manure 'Ref No' for 'example 1' is 18 and for 'example 2' it is 21.

• The application rate is worked out by dividing the total amount applied by the field area. In both of the examples the application rate = 30 m ³/ha. Columns a to h would be completed, for each field, as below:

Step 2: Calculate available N in spring/summer after spreading organic manure

• From the fourth column of the tables, the total N content is 3kg/m ³ for Ref. No. 18 and 21.

• The total nitrogen application rate for both fields is therefore 90kg/ha i.e. the manure application rate (30m ³) multiplied by the N content of the manure (3kg/m ³).

• To determine the percentage of nitrogen available to the crop we use the manure 'Ref No.', soil type and the time of application.

• Both fields in the examples had slurry applied in the spring.

• The availability of N from manures applied in the spring is the same across all soil types.

• The slurry applied in 'example 1' comes under 'Ref. No.' 18. The % of the N available to the crop is therefore 40%. The total N available = 40% x 90 = 36kg/ha.

• The slurry applied in 'example 2' comes under 'Ref No.' 21. The % of the N available to the crop is therefore 30%. The total N available = 30% x 90 = 27kg/ha. The remaining columns are completed as below:

Step 3: The values in column 'l' are used to adjust the N requirement in the Fertiliser and Manure plan. 10% of the total N applied (the column 'j' figure) is entered into column 'm' and carried froward to the next years plan. Note that the N available from the previous years application in 'example 1' will be 9kg/ha, as the same slurry type was applied at the same rate.

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