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Guidelines for farmers in nitrate vulnerable zones

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Guidelines for farmers in nitrate vulnerable zones

Booklet 1: Fertiliser and Manure Plans - Part 1 - Determining crop and grassland N requirements

A Fertiliser and Manure Plan must be prepared and implemented each year. Detailed guidance on its preparation is provided in this Booklet.

To help you produce a Fertiliser and Manure Plan, this guidance pack includes appropriate reference material. This includes:

  • Blank Tables which, when completed, allow you to calculate the necessary information.

  • Reference Tables that contain all the necessary data to help you complete the blank tables. See Booklet 3, 'Nitrogen recommendation Tables for cereals, oilseed rape, potatoes and grassland'.

If you have applied livestock manures, then some of the information you require will be calculated separately, using Booklet 2 'Fertiliser and Manure Plan - Part 2, Manure Planning'.

  • Step-by-step guides that take you through the processes required for completing the blank tables and the various calculations, along with appropriate worked examples.

  • It is recommended that you read through this guidance with Booklet 3 and the blank Table A to hand, as this will help clarify the various steps and familiarise you with their use. All references to Table and page numbers, in this guidance, relate to Booklet 3 unless stated otherwise.

Note that the basic elements of the Fertiliser and Manure Plan must have been prepared in time for the start of the NVZ year i.e. by 19th December in each year.

  • You will be expected to have started the plan by entering the known cropping details for each field that was sown in the autumn or that will remain in grassland. You should also enter the intended cropping for fields that are to be sown in the Spring (the plan can always be adjusted if this changes for any reason).

  • You should have calculated the recommended N requirement, taking account of adjustments such as manure applications to the previous crop or winter manure applications made for the current/planned crop.

  • The plan should then be up-dated, as appropriate, to take account of factors such as winter and spring rainfall and spring livestock manure applications, which require further adjustments to the recommended N rate.

Step-by-step guide for cropped fields and fields where new grass is to be established

This guidance takes you through the steps required to complete Table A. Page and Table references refer to Booklet 3.

Step 1: Complete the basic farm details for the 12-month period which the plan covers. List each FID in column 1 and enter the appropriate cropping details in column 3/4.

Step 2: Enter the soil type for each FID into column 2. If you do not know the soil type, page 3 takes you through the steps required to assess it.

Step 3: Determine the residual N group. This is based on the previous crop (or management of grass/clover swards) and is determined from Table 4. Enter the result in column 5.

Step 4: Assess the N requirement for each crop. This takes account of the soil type and residual N group and is assessed using the relevant crop Table from Booklet 3.

Note that any seedbed requirement for a winter-sown crop is entered at column 6.

The figure entered into column 'a' is the basic N requirement for the crop in the year for which the plan is being prepared. The remaining steps are used to adjust this figure taking account of intended market, sowing date, rainfall and livestock manure applications.

Step 5: Adjust the N requirement for intended market, late sowing etc., using the information provided in the relevant crop Table. Enter any adjustments in column b.

Step 6: If no livestock manure has been applied for the planned crop, proceed to Step 7.

If livestock manure has been applied for the planned crop, calculate the N available from livestock manure applications. This information is calculated separately using Booklet 2, Manure Planning. Enter the figure to be deducted in column c.

Step 7: If no livestock manure has been applied for the previous crop, proceed to Step 8.

If livestock manure was applied for the previous crop, calculate the N available from previous livestock manures. This information is calculated separately using Booklet 2, Manure Planning. Enter the amount to be deducted in column d.

Step 8: Add columns 'b', 'c' and 'd', and enter the total N adjustments in column e.

Step 9: Re-calculate the required rate of N fertiliser (kg/ha) and enter in column f.

Step 10: Adjust in March for actual winter rainfall using the relevant crop Table from Booklet 3. Enter the figure in column g and enter the adjusted figure in column h.

Step 11: Adjust for spring rainfall where more than 200mm (8 inches) of rain has fallen between the first and final spring N dressing using the appropriate crop Table. Enter the figure in column i and calculate the updated application rate as appropriate, entering the result in column j.

You will now have calculated the N requirement for each crop on the holding.

Worked example: Assessment of N requirement for established fields and new grass fields

  • A crop of Spring barley is being grown for feed in a 3.83ha field on heavy soil, following seed potatoes.

  • 115m 3 of 6% dry matter slurry was applied in March (incorporated within 6 hours), prior to sowing the barley.

  • 115m 3 of similar slurry was applied in the previous February, prior to planting the seed potatoes.

  • Winter rainfall was 550mm and 40mm fell between the 1st and 2nd Spring N applications.

  • The barley was sown 10 days later than the optimum sowing date for the area.

Step 1: Enter the farm name, the farm code and the 12 month period of the plan. List each field and enter the current and previous crops.

Step 2: Assess the soil type using the guidance at page 3. In this case the soil type would be Other Mineral Soil.

Step 3: Using Table 4, the N residue group for seed potatoes is group 3.

Step 4: Using the relevant crop Table, determine the N requirement for the crop taking account of the soil type and the N residue group. In this case the relevant Table is Table 7 and the crop requirement is 110kg N/ha.

The first 4 steps provide us with the necessary information to complete the first 7 columns of Table A, as in the example below. The remaining steps are used to adjust the column 'a' figure as appropriate.

IACS Field Identifier (FID)
xx/xxxx/xxxx
1

Soil Type
2

Crop

N residue group 1-6
5

N for next crop

Planned
3

Previous
4

Autumn (kg/ha)
6

Spring (kg/ha)
a

Example/00001

OMS

SB(F)

SP

3

0

110

Step 5: Adjust the N requirement for intended market or late sowing date. In this case the crop was sown 10 days later than the optimum date. Using Table 7 the required adjustment is -1.5kg/ha per day i.e -15kg N/ha.

Step 6: The N available from current manure applications is calculated separately using Booklet 2 (see worked example at page 9 of Booklet 2). In this case 36kg/ha has to be deducted from the recommended amount.

Step 7: The N available from previous manure applications is calculated separately using Booklet 2 (see worked example at page 9). In this case, the slurry applied for the seed potatoes requires 9kg N/ha to be deducted.

Step 8: Calculate the total N adjustments. In this case 60kg N/ha have to be deducted.

Step 9: Taking account of the deductions, the revised N requirement is 50kg N/ha.

Step 10: Adjust for Winter rainfall. Using Table 7, locate the appropriate N residue group (in this case '3') and the appropriate soil type at the winter rainfall section (in this case 'All other soils'). The adjustment is +10kg/ha. This gives us a revised rate of 60kg N/ha.

Step 11: Follow the same procedure as above for Spring rainfall. In this case no adjustment is required.

The remaining columns of the Table would be completed as follows:

Adjustments of N (kg/ha)

Adjusted N rate (kg/ha)
a+e = f

Adjustments of N(kg/ha)

Updated N rate (kg/ha)
h+i=j

For intended market, etc.
b

Manure for planned crop
c

Manure for previous crop
d

Total
b+c+d = e

for winter rainfall
g

Updated N rate (kg/ha)
f+g = h

For spring rainfall
i

-15

-36

-9

-60

50

+10

60

0

60

Step-by-step guide for established grass fields, using Table B

This guidance takes you through the steps required to complete Table B. Page and Table references refer to Booklet 3.

Step 1: Complete the basic farm details and the 12-month period that the plan covers. List each FID in column 'a'.

Step 2: Enter the soil type for each FID into column 'b'. If you do not know the soil type, page 3 takes you through the steps required to assess it.

Step 3: Assess the site class.

  • To assess this you will need to refer to Table 2 and determine the annual rainfall, between April and September, for your area.

  • This information is then used, along with the soil type, to assess the site class using Table 3.

  • Enter the result in column 'c'.

Step 4: Determine the residual N group. This is based on the previous management of the grassland and is determined from Table 4. Enter the result in column 'd'.

Step 5: Assess the N requirement for grass in each field.

  • This takes account of the site class and residual N group.

  • It is assessed using Table 14 or 15, depending on clover content.

  • Enter the result in column 'e'.

The figure entered into column 'e' represents the basic N requirement for the crop. The remaining steps are used to adjust this figure taking account of intended management and livestock manure applications.

Step 6: Enter the intended management regime into columns 'f', 'g' and 'h', as appropriate.

Step 7: Adjust the N requirement for intended management.

  • Select the appropriate management regime from Table 14 or 15 and enter the required adjustment in column 'I'.

Step 8: If no livestock manure has been applied for the planned crop, proceed to step 9.

If livestock manure has been applied for the planned crop, calculate the N available from livestock manure applications. This information is calculated separately using Booklet 2, Manure Planning. Enter the figure to be deducted in column 'j'.

Step 9: If no livestock manure has been applied for the previous crop, proceed to step 10.

If livestock manure was applied for the previous crop, calculate the N available from previous livestock manures. This information is calculated separately using Booklet 2, Manure Planning. Enter the amount to be deducted in column 'k'.

Step 10: Add columns 'i', 'j' and 'k', and enter the total N adjustments in column 'l'.

Step 11: Re-calculate the required rate of N fertiliser by adding the values from columns 'e'+'l'. Enter the updated N requirement into column 'm'.

You will now have calculated the N requirement for each grass crop in each field on the holding.

Worked example: Assessment of N requirement for established grass fields

  • A 15ha grass field with a low clover content is being used for silage production.

  • It is intended that 2 cuts will be taken and one application of chemical N will be made to the aftermath.

  • The soil type in the field is 'other mineral soil' and average local rainfall, from April to September, is 450mm.

  • The field is entering its third year in grass and has received an average of over 150kg/N ha in the previous 2 years. It has not been grazed in the last 2 months, or in September or October.

  • A total of 450m 3 (i.e. 30m 3/ha) of 6% dry matter dairy slurry was applied in the Spring.

Step 1: Enter the farm name, the farm code and the 12 month period of the plan. List each field in column 'a'.

Step 2: Enter the soil type into column 'b'. In this case the soil type is OMS.

Step 3: Assess the site class using Table 2 to determine the rainfall and Table 3 to assess the site class. From the average Summer rainfall and the soil type, this is a site class 2.

Step 4: Determine the residual N group using Table 4. Previous N applications and the grazing regime put this into the '1-2 year high N ley' category. It is therefore in N residue group 3.

Step 5: Assess the N requirement. The sward has a low clover content, so use Table 14. The N requirement for grass growing on a site class 2 field, with N residues falling into group 3, is 200kg N/ha.

Step 6: Enter the intended management regime into columns 'f', 'g' and 'h'. Columns 'a' to 'h' would now be completed as follows:

IACS Field identifier orField Name

Soil type

Site class 1 - 5

N residue group 1 - 6

N requirement (kg/ha)

Intended Management

f. enter whether grazing, silage or hay
g. enter no. of cuts, if silage or hay
h. enter number of N applications to be made to grazing/aftermath grazing

Column a

b

c

d

e

f

g

h

Example/00002

OMS

2

3

200

silage

2

1

Step 7: Adjust the N requirement for intended management. 2 cuts of silage, with one application to the aftermath grazing, requires an additional 100kg N/ha.

Step 8: The N available from manure applications for the planned crop is calculated separately at Booklet 2 (see worked example on page 9), In this case the adjustment is -27kg N/ha.

Step 9: No livestock manure was applied in the previous year.

Step 10: Sum columns 'i', 'j' and 'k'. The total adjustments amount to +73kg N/ha.

Step 11: Recalculate the required rate of N fertiliser. In this case the adjusted requirement is 273kg/ha. Columns 'i' to 'm' would be completed, as below:

Adjustments of N (kg/ha)

Manures for planned crop

Manures for previous crop

Total adjustment (kg/ha)
= (i+j+k)

Updated N rate
(kg/ha) = (e+l)

For intended management

i

j

k

l

m

+100

-27

0

+73

273

In field composting of vegetable crop residues to minimise nitrate leaching

Introduction

These paragraphs give an outline of how in-field composting of leafy vegetable residues can reduce nitrate leaching, and some examples of how the process works. More details are available in the SAC Technical Note (T487) "Incorporation of C-rich organic amendments with N-rich vegetable crop residues to minimise nitrate leaching".

Why use in-field composting?

Nitrogen returns from vegetable crops are much higher than from cereals, and are extremely variable depending on the harvest index and the amount of crop that can be marketed as well as fertiliser and management practice. Soil mineral N analysis at harvest to a depth of 50cm will give an estimate of the residual mineral N in the soil. Table A (below) shows typical potential N leaching from crop residues for a range of vegetable crops.

A: Nitrogen content of vegetable crop residues and potential leaching of nitrate-N.

Crop

N content of crop residues
(kg/ha)

Potential leaching from residues
(kg/ha)

Onion

13

6

Lettuce (round)

21

12

Carrot

66

19

Celery

50

21

Spinach

34

23

Cabbage (green)

57

25

Iceberg Lettuce

49

30

Leeks

61

35

Green Beans

89

45

White Cabbage

142

66

Red Cabbage

145

69

Broccoli

135

78

Savoy Cabbage

152

80

Brussels Sprouts

215

99

Peas

200

104

Cauliflower

163

104

  • Nitrogen leaching from crops may be reduced by the incorporation of straw or Paper Mill Sludge (PMS)

  • The N is "locked up" to be released at a later date

Assessment of the amount of locked up N and timing of release

Some of the nitrogen locked up will be released later. The amount of lock up depends on the organic carbon and nitrogen contents. This nitrogen can be considered as extra nitrogen available for vegetable crops planted in the spring. Tables B and C on the next page show the potential amount of lock-up of nitrogen from September till the end of December by a one tonne DM/ha application of waste material, when incorporated with vegetable crop residues at the end of September. It also gives figures for the potential for release of this N from January to June.

It is important that the waste material is applied before the end of September.

Potential autumn lock-up of nitrogen and release in spring after application of paper mill sludge and straw in September.

Table B: Paper mill sludge

N content
%

Potential autumn lock-up of N
(kg N/ha)

Potential spring release of N
(kg N/ha)

0.6

-3.9

-0.2

0.8

-2.0

0.5

1.0

-0.4

0.8

1.2

1.2

1.1

Table C: Straw

N content
%

Potential autumn lock-up of N
(kg N/ha)

Potential spring release of N
(kg N/ha)

0.6

-9.7

-0.4

0.8

-8.1

-0.1

1.0

-6.5

0.2

1.2

-4.9

0.5

Note: Positive values imply increase in mineral N availability for crop uptake or leaching; negative values imply decreased availability.

Applications after the end of September will not be as effective, the locking-up process may then continue into the spring reducing nitrogen availability for early spring growth.

Precautions

It is important to realise that the composition of Paper Mill Sludge (PMS) is very variable depending upon the type of paper being created. The carbon:nitrogen ratio can vary considerably and some types of PMS may contain toxic elements. An analysis of the PMS prior to application is essential in order to ensure that it is suitable for incorporation into the soil.

The Paper Federation of Great Britain has produced a Code of Practice for Land-spreading Paper Mill Sludge, which you should consult. SEPA are also producing guidance and you should take account of the general guidance on waste disposal contained within the PEPFAA Code.

Calculation of the quantity of straw or PMS to apply

Calculating suitable amounts of cellulose based waste to apply to vegetable crop residues is illustrated in the examples on the next page.

Worked Example: Estimating quantities of cellulose based wastes and their impact on N availability

Broccoli crop residue incorporated in September. The residual soil mineral at harvest is 42kg/ha. after soil analysis. Paper mill sludge containing 0.6% nitrogen is to be used.

  • Calculate the expected nitrogen release by adding the amount of potential leaching from residues to the amount of soil mineral residue nitrogen at harvest. Using Table A, the potential leaching from broccoli crop residues is 78kg/ha. The expected N release (potential for leaching) is:

42 + 78 = 120kg/ha

  • Calculate the quantity of waste material applied by dividing the expected nitrogen release by the potential autumn lock-up. Table B on the previous page gives a lock-up figure of 3.9kg N/tonne DM PMS. The suitable waste material application is:

120 ÷ 3.9 = 30.8 t PMS/ha

  • Calculate the expected extra release of nitrogen by multiplying the waste application rate by the potential spring release of nitrogen found from Table B. For this example, Table B gives a value of -0.2:

30.8 x (-0.2) = -6.16kg N/ha

  • The negative figure indicates that lock up is still occurring, so a small increase in fertiliser nitrogen the following year may be appropriate.

Worked Example: Estimating quantities of cellulose based wastes and their impact on N availability

Iceberg lettuce crop residue incorporated in September. The residual soil mineral at harvest is 46kg/ha. After soil analysis. Straw containing 1% nitrogen is to be used.

  • Calculate the expected nitrogen release by adding the amount of potential leaching from residues to the amount of soil mineral residue nitrogen at harvest. Using Table A, the potential leaching from crop residues is 30kg/ha. The expected nitrogen release (potential for leaching) is:

46 + 30 = 76kg/ha

  • Calculate the quantity of waste material applied by dividing the expected nitrogen release by the potential autumn lock-up. Table C on the previous page gives a lock-up figure of -6.5kg N/tonne DM straw. The suitable waste material application is:

76 ÷ 6.5 = 11.7 t DM Straw/ha

  • Calculate the expected extra release of nitrogen by multiplying the waste application rate by the potential spring release of nitrogen found from the tables on the previous page. For this example, Table C gives a value of 0.2:

11.7 x 0.2 = 2.3kg N/ha

  • i.e. so a small downward adjustment in fertiliser nitrogen the following year can be made.

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Page updated: Wednesday, September 14, 2005