AHDB CP107b Field Lab impact of digestates on soil health 29 June - - PowerPoint PPT Presentation

AHDB CP107b

Field Lab – impact of digestates on soil health

29 June 2017

Agenda

10.00 Arrival, tea and coffee 10.20 Welcome, brief introduction to the GREAT soils project and the Field Lab at Mid Coul 10.30 Preliminary results from soil health testing in field trial (impact

• f digestates on soil health, crop growth and yield)

10.50 Field walk to look at digestate trials 11.40 Digestates – characteristics of different types and their likely impact types on soil health and quality 12.00 How to maximise the financial value of digestates and minimise the risk of damage to soil health through inappropriate application strategies. 12.20 Compliance with the law and farm assurance scheme rules 12.30 Future topics for discussion at remaining meetings 12.45 Lunch 13.30 Finish

Project Partners

Funder:

AHDB horticulture

Leader:

Soil Association

Ben Raskin, Liz Bowles, Simone Osborn Partners:

The Organic Research Centre

Anja Vieweger and Bruce Pearce

Earthcare Technical

Audrey Litterick and Martin Wood Duration: 1 April 2015 – 31 March 2018

Aims of the project The project is:

• Evaluating soil assessment methods for growers
• Improving growers’ confidence in ‘reading the signs’
• Offering the opportunity to practise assessment methods with

colleagues and advisors

• Developing methods and approaches for practical soil analysis

and evaluation to enable confident choice of management

• ptions.
• Engaging with, and disseminating methods and approaches to a

wide range of levy payers, growers, advisors and other stakeholders

Aims of the project Benefits for growers:

• Improved health assessment of their soils;
• Ability to follow a more accurate and integrated strategy for soil

management, specifically adapted to their own conditions;

• Better-informed decisions when aiming to optimise inputs, increase

soil fertility and increase soil organic matter.

• Where growers are able to optimise and maintain soil organic

matter levels, the benefits can be financially and environmentally

• significant. Improved soil health management can increase yields

and potentially reduce costs as the land will become more productive.

Aims of the project

• What is available out there? Critical review and

evaluation of existing methods and approaches for assessing, benchmarking and improving soil health.

• What is actually useful in UK soils? Determine the

usefulness, efficiency and practical applicability of the methods and approaches during initial consultation and project as a whole.

• Comparison of most relevant approaches. Six sites/farms

have been selected for field trials (one in Scotland) and comparisons of soil management and soil assessment tools are being made in two project years (2016/2017 and 2017/2018)

Moray coast veg growers Field Lab

Aim: To determine whether the application

• f whole digestate made

from farm-produced energy crops has an impact on the health of soils in Moray coast vegetable rotations.

Moray Coast veg growers “Field Lab” Progress and plans:

• Grower has applied digestate in Autumn 2016 and Spring 2017 to

two fields

• Will make additional one or two applications (weather-dependent)

to same two fields later in 2017.

• Control strips (no digestate applied) are being left in each field for

comparison.

• Treated and untreated areas of soils in the fields have been

assessed and sampled prior to the first digestate application and around 1 to 3 weeks after two of the subsequent digestate applications.

Assessment methods

• Routine analysis (Soil pH, extractable P, K, Mg)
• Soil structural evaluations
• Earthworm counts
• Soil respiration
• Quadrat weed counts in treated areas
• Germination tests (weeds germinating in samples of

known volume of digestate spread onto sand or growing media)

• Bait lamina sticks
• Underpants tests (!)
• Crop growth and quality assessments?

Moray Coast Field Lab

Moray Coast Field Lab

Soil nutrient status

Table 2. M8 field soil analysis results Digestate? Parameter Unit No Yes What does this mean? pH1

• 6.1

6.0 pH is slightly below the target of 6.5 for vegetable rotations. Organic matter % 4.2 3.7 Fairly typical SOM level for this soil type in this region. Would be benefit in increasing it. Extractable nutrients P (status)3 mg/l 3.5 (L) 3.0 (L) Well below target of “high” for P K (status)3 ″ 57 (L) 85 (M-) Below or well below target of “high” for K Mg (status)3 ″ 140 (M-) 154 (M-) At target for Mg CO2 evolution5 mg/kg 40 62 Soil has variable, low microbial respiration Soil texture SL SL Sandy loam

Soil nutrient status

Table 2. M10 field soil analysis results Digestate? Parameter Unit No Yes What does this mean? pH1

• 6.4

6.5 pH is pretty much at target of 6.5 for vegetable rotations. Organic matter % 4.5 4.0 Fairly typical SOM level for this soil type in this region. Would be benefit in increasing it. Extractable nutrients P (status)3 mg/l 5.6 (M-) 7.8 (M-) Below target of “high” for P K (status)3 ″ 89 (M-) 47 (L) Below or well below target of “high” for K Mg (status)3 ″ 141 (M-) 115 (M-) At target for Mg CO2 evolution5 mg/kg 98 40 Soil has variable microbial respiration Soil texture SL SL Sandy loam

Soil structure assessments (VESS, Ball et al., 2012)

Table 2 Visual assessments of soil structure in the 2017 grass clover leys Sampling zone score Field area 1 2 3 4 5 Mean score What does this mean? M8 No digestate 3 2 2 2 3 1.6 Structure typical of fields which are in intensive vegetable rotations. Could be better, though recent dry weather is probably making the structure seem worse than it is. M8 Digestate 2 3 3 2 3 1.6 As above M10 No digestate 2 2 3 3 3 1.8 As above M10 Digestate 3 2 2 2 3 2.2 As above

Soil compaction probe readings

Table 3 Compaction as measured by a Dickey John compaction probe (2017 grass crops) Probe reading Field 1 2 3 4 5 Mean score What does this mean? M8 No digestate 280 300 280 310 290 292 Compaction present, soil very firm in

• places. Almost certainly less bad than it

looks – readings probably high due to recent dry weather. M8 Digestate 290 300 310 320 280 300 As above M10 No digestate 310 300 290 290 320 302 As above M10 Digestate 190 260 250 280 270 250 As above

Earthworm counts

Table 4 Earthworm counts in the 2017 grass clover leys Total no. of worms found of following sizes Total no. of worms Mean count per pit Juvenile (cm) Adult (cm) 1 2 3 4 0-3 3-7 7-10 >10 <7 7-12 >12 Field area M8 No digestate 2 1 0.8 2 1 M8 Digestate 3 1 1 2 1 M10 No digestate 1 0.3 1 M10 Digestate 1 0.3 1

Soil respiration measurements

mg CO2/g soil/day

10 20 30 40 50 60 70 80 90 M8 No Digestate M8 Digestate M10 No Digestate M10 Digestate

Moray Coast veg growers “Field Lab” Quadrat weed counts:

• Six 1m2 quadrats were thrown down at random across the

treated area and no weeds were found in any quadrat (although there were some weeds in the fields)

• There is no evidence that use of digestate is resulting in

increased weed growth in the grass clover leys.

Moray Coast veg growers “Field Lab” Germination tests:

• Digestate was applied to the surface of wooden trays (25 x 25 cm x 10

cm depth) at the equivalent of 20 t/ha (2 kg/m2 or 500 g per tray).

• The digestate was either mixed thoroughly into the soil (1 tray) or it

was spread across the soil surface in lines 20 cm apart, as it would be when spread using a band spreader (1 tray).

• An equivalent amount of available N, P and K were used in a 3rd tray so

that a fair comparison could be made with soil not treated with digestate.

• 100 mustard seeds were sown in each tray and their germination and

growth was measured after 3 weeks and 7 weeks.

• Trays were left out of doors on the soil surface and were watered

regularly or rain was allowed to fall on them naturally.

• Over 90% of the mustard seeds germinated in all trays.
• There was no obvious difference in germination or growth between

digestate-treated trays and straight-fertiliser trays.

Moray Coast Field Lab

• Nutrient additions: Crop-based liquid digestate

contains significant quantities of nutrients, especially N and K, but also P, Mg and S.

• Analysis to date has shown that this is true here,

(though significant amounts of nutrients, particularly N and K are ending up in the fibre) Nutrient content (kg/fresh tonne) of Kerrowgair separated

liquid digestate N Phosphate Potash SO3 MgO 3.4 1.4 5.6 0.6 ?

Moray Coast Field Lab Nutrient additions (kg/ha) when Kerrowgair liquid digestate is applied at 10, 20, 40 and 60 t/ha (in total) Application rate N (Crop-available N at 60%) Phosphate Potash SO3 10 t/ha 33 (20) 14 56 6 20 t/ha 66 (40) 28 112 12 40 t/ha 132 (79) 56 224 24 60 t/ha 198 (119) 84 336 36

Future work

Assessments:

• 1. Crop yield and/or quality
• 2. Bait lamina sticks and pants
• 3. Post-last digestate appln.

a) Routine analysis and SOM b) Soil structure assessments c) Soil compaction probe d) Worm counts e) Soil respiration (Solvita test with plate reader)

Final grower meeting for Moray Coast Field Lab

Due spring 2017 (pre 31 March 2018):

preferred date?

Topics:

• 1. Present and discuss results
• f Field Lab
• 2. Present and discuss results

from other UK field trials and field labs

• 3. Other?

Moray Coast veg growers “Field Lab”

Thankyou!