STA0013: Research into increasing the use of recycled materials in the production of growing media

Creating markets for recycled resources STA13: Research into increasing the use of recycled materials in the production of growing media Research Report: Organics Report on the growing trial at Stockbridge Technology Centre, Cawood, Yorkshire: propagation of vegetables Written by: Peatering Out Ltd. Published by: The Waste & Resources Action Programme The Old Academy, 21 Horse Fair, Banbury, Oxon OX16 AH Tel: 1295 8199 Fax: 1295 819911 www.wrap.org.uk WRAP Business Helpline: Freephone: 88 1 24 April 25

Contents 1 Summary... 2 2 Introduction and objectives... 3 3 Methodology... 4 4 Observations... 6 4.1 Cabbage Castello... 6 4.2 Courgette Patriot... 11 4.3 Leek Jolent... 14 4.4 Lettuce Roxette... 18 4.5 Overall review... 21 5 Conclusions... 22 Appendix 1 Trial protocol... 23 Appendix 2 Analyses... 24 2.1 Treatment mixes... 24 2.2 Substrates... 25 Appendix 3 - Weighing sheet... 27 STC - POTSTC33 1

1 Summary General This report deals with a propagation trial on cabbage, courgette, leek and lettuce at Stockbridge Technology Centre (STC), Cawood, Yorkshire carried out between May and September 23. The trial was part of WRAP project STA13 which investigated the use of recycled materials in growing media at 14 UK sites. The treatments included two formulations based on 25% by volume fine green compost (GC) diluted with either composted bark fines (PF mix) or with fine peat (PR mix), and the nursery standard Levington F2 peat based growing medium. Each of the crops was laid out in a randomised block design in the propagation unit and the data collected was subjected to an Analysis of Variance to determine the statistical validity of differences between means. In accordance with convention, those differences which were found to be valid and unlikely to be due to chance are described as significant. Performance Germination Growing media incorporating a fine grade of green compost (less than 5mm) at 25% v/v, diluted with either fine peat or bark fines, matched the germination performance of a leading all peat proprietary potting medium in all crops except leek where it was 5% to 9% lower after 14 days. Seedling development There was a similar growth trend in all four crops. Generally, plants in all treatments grew well until approximately 14 days after sowing when those in the treatments containing green compost (PR and PF but notably the PR treatment) appeared to become of short of nitrogen, well before they were ready to be transplanted. This was marked in lettuce, cabbage and leeks and the latter two crops responded well to supplementary liquid feeding. Although there were significant differences in size (especially between the STD and PR treatments) at the end of the propagation stage, all unfed lettuce and courgette plants and all fed cabbage and leek plants were of acceptable quality for transplanting. Field performance The establishment of transplants in the field was unaffected by growing medium treatment. Cabbage, courgette and leek plants all established well and by the end of the growing season there were no apparent differences between the treatments. Overall conclusion The trial suggests that a variety of vegetables could be propagated successfully in peat reduced and peat free growing media containing 25% v/v green compost and a base dressing of ammonium nitrate. However, more formulation work is required, to ensure that sufficient nitrogen is added to meet the needs of the more hungry crops - without adversely affecting germination. STC - POTSTC33 2

2 Introduction and objectives WRAP project STA13 aims to increase the use of recycled materials in the production of growing media for both professional and amateur applications. To achieve this, demonstration growing trials on nurseries were seen as the best way to influence both the professional growers and the hobby gardener. This report describes one of the 2 demonstration trials on 14 UK sites covering a variety of regions, crops, conditions and production methods. The trials programme compares the performance of peat free (PF) and peat reduced (PR) formulations incorporating green compost (GC) with a nursery standard peat based growing medium (STD). The two formulations employing green compost were designed by Peatering Out Ltd. The substrates and fertiliser rates varied with the site to suit the crop type and growing conditions. However, the same generic descriptions and abbreviations are used for the three principal trial mixes used in each trial and these are described below under Terminology and substrates. This report deals with a propagation trial on four vegetable subjects at Stockbridge Technology Centre (STC), Cawood, Yorkshire. All plants were raised from seed in the STC plant propagation unit. The cabbage and leek were sown in 38 module trays and lettuce in 14 module trays. The courgettes were also sown in 14 modules but only using alternate cells (i.e. 52 plants per tray). The trays were raised 2cm above the floor to facilitate drainage and half of each batch of cabbage and leek plants received liquid feed beginning 21 days after emergence. The trials here compared the performance of formulations based on 25% by volume fine green compost diluted with either composted bark fines (PF mix) or with fine peat (PR mix), and the nursery standard Levington F2 peat based growing medium. Terminology and substrates The following table explains the growing media terminology used in this and the other trial reports: Terminology Abbreviation for mix Green compost 1 content Peat 2 content Other substrates Peat free PF 25-4% v/v Nil Bark 3-75% v/v Forestry residues 4-6% v/v Peat reduced PR 33-4% v/v 4-7% v/v Bark 3-75% v/v Forestry residues 4-6% v/v Standard 5 - growers peat based proprietary or nursery mix STD Nil 75-1% v/v Bark -25% v/v Composted wood residues -25% v/v Others (including loam) -6% Notes: 1. Green compost = a recycled product of composted green material from parks and gardens etc. (also known as composted green waste and composted yard waste). GC was sourced from one of three suppliers in the same region as the proposed trial sites who were either BSI PAS 1 certified or in the process of obtaining this certification. In 12 trials in the South and East of England, GC from Eco Composting Ltd. was utilised whilst material from Waste Recycling Group Ltd (WRG) was used for the remaining four mainland trials. For all four Northern Ireland trials, GC from Natural World Products Ltd. (NWP) was incorporated. 2. The peat used in all PR mixes and many peat based mixes was Shamrock medium grade. 3. Bark used in PF and PR mixes was sourced from Melcourt Industries Ltd. Generally the fine Grow Bark was used but where coarse bark was required (for example with HONS) Potting Bark was employed. 4. Forestry residues = composted material derived from branches and tops of felled trees (also known as brash or "lop & top"). The material used was Melcourt Sylvafibre, derived exclusively from pine grown in East Anglia. 5. About half of the Standard mixes utilised 1% peat with the remainder employing 75% to 85% peat; bark being the most common diluent. The peat free mixes were generally blends of GC with either forestry residues or bark but occasionally both. See methodology and the trial protocol (appendix 1) for precise details of the growing media used in these trials. STC - POTSTC33 3

3 Methodology Treatments: Design: Growing media 1 Green compost/composted bark 1 (25:75% v/v) 2 2 Green compost/sphagnum peat (25:75% v/v) 2 3 Standard proprietary peat based Levington F2 (1% v/v peat) 3 treatments x 8 replicates = 24 trays of each of 4 crops = 96 plants total Each plot was labelled and laid out in a randomised block design. NB There was a sub-treatment for cabbage and leeks, with half of each batch of replicates receiving liquid feed from 21 days after emergence until they were transplanted. Materials: 1. Green compost: <5mm, ex-eco Composting, Bournemouth, UK 2. Composted bark, Grow Bark, ex-melcourt 3. Peat: sphagnum, fine grade, Shamrock ex The Scotts Co. UK Ltd. 4. Nitrogen: ammonium nitrate (AN); 34.5% N (17.2% ammoniacal nitrogen and 17.3% nitric nitrogen) 5. Lime : ground magnesium limestone The green compost and other substrates were fully analysed and the results (appendix 2) used as a basis for the formulation of the treatment mixes in the weighing sheet (appendix 3). Treatments 1 and 2 were prepared at Peatering Out Ltd. Headquarters, Norfolk. Lime rate was adjusted to suit each treatment mix. The standard mix was manufactured by The Scotts Co. UK Ltd. It contained 1% v/v peat and was provided by the nursery. All treatment media were sampled at point of use and analysed, and the results are given in appendix 2.1. Crops: Cabbage Castello Courgette Patriot Leek Jolent Lettuce Roxette Seeds were sown in week 19, 23 as described in the trial protocol (appendix 1) and recordings continued for 21 to 32 days according to crop. On completion of these assessments, subsets of the courgette, cabbage and leek crops were transplanted to enable plant establishment, growth and potential field performance to be observed. Transplanting occurred on 4 th June, 17 th June and 3 th June 23 respectively. Nursery management: The plants were raised in the propagation unit and the plugs were watered by hand. A liquid feed solution of Nitram (at 3g per 1 litres of water) was applied twice per week via a watering can to a subset of the cabbage and leek crops from 21 days after emergence and the foliage washed with plain water to avoid scorch. No pest, disease or weed problems were encountered and no treatments were necessary. Crop assessments, scoring and statistical analysis: Courgette and lettuce were assessed at intervals between 9 th May and 3 th May 23 and cabbage and leek between 9 th May and 1 th June 23. The assessments carried out included: 1. Number germinated 2. Vigour score/index (-5); where = dead, 1 = small, very weak and underdeveloped and 5 = large, strong and healthy (see reference photographs in observations section of this report for grading) 3. Plant width, height and/or girth (depending on crop) 4. Fresh weight of five or ten plants (depending on crop) 5. Establishment and subsequent growth monitored after planting. For courgettes, this included an assessment of the number of fruit harvested. 12 1 Plus extra nitrogen (N) to prevent premature N-starvation. STC - POTSTC33 4

Selected data was subjected to statistical analysis by Analysis of Variance to enable Least Significant Differences (LSDs) to be calculated. These have been calculated at the normal confidence level of P<.5 which signifies that there is only a one in twenty probability that the difference is due to chance. Where means differ by the LSD or more, the difference is described in the text as significant, which is shorthand for statistically significant. 2 Plus extra nitrogen (N) to supplement the N in the green compost Addition of liming material was less than for an all-peat product. STC - POTSTC33 5

4 Observations 4.1 Cabbage Castello The final assessment was completed on 1 th June 23, 32 days after sowing. The number of seeds germinated, plant vigour score, plant width and fresh weight of five plants in each treatment are shown in table 1. The reference material, examples of plants from each treatments and an overview of the transplanted crop are illustrated in photographs together with charts to aid interpretation of the data (figures 1 to 11). Table 1. Assessment Number Germinated (from 38) Vigour Score/Index Plant Width (cm) Weight per 5 (g) Cabbage: Summary of assessment data seven to 32 days after sowing, May and June 23 Medium Mean (SD) and LSD on day after sowing 7 1 14 21 32 STD 31.75 (2.31) 33.5 (.76) 34 () * PR 3 (3.85) 32 (3.2) 37.4 (1.8) * PF 299 (2.98) 31.13 (1.55) 33.75 (.7) * LSD.67 (df) 23 STD (F) 7 () STD (UF) 2 () 2 () 4 () 5 () 5.5 (.57) PR (F) 6 () PR (UF) 1.88 (.35) 2 () 3 () 3.25 (.46) 4.25 (.43) PF (F) 6 () PF (UF) 1.75 (.46) 2 () 3 () 4 () 4.5 (.57) LSD.16.24 (df) 23 23 STD 2.52 (.31) 3.42 (.42) * * * PR 2.46 (.25) 3.51 (.41) * * * PF 1.88 (.25) 3.24 (.21) * * * LSD.9 (df) 119 STD (F) * * * * 13.9 (1.64) STD (UF) * * * * 8.1 (1.89) PR (F) * * * * 1.69 (.95) PR (UF) * * * * 5.77 (1.52) PF (F) * * * * 11.96 (2.31) PF (UF) * * * * 6.98 (.67) LSD 1.1 (df) 23 F = plants received liquid feed twice a week from day 21 UF = plants received no liquid feed * = data not recorded STC - POTSTC33 6

Figure 1. Cabbage: Mean number of seeds germinated seven, ten and 14 days after sowing, May 23 35 Number number of cabbage germinated (from 38) Mean number germinated 3 25 2 15 1 5 d 7 d 1 d 14 There was a very small but significant difference in the germination of cabbage seed between the three treatments; PR being approximately 1% better than both STD and PR by day 14. Figure 2. Cabbage: Plant width seven and ten days after sowing, May 23 Plant Width - cabbage Mean plant width (cm) 4 3.5 3 2.5 2 1.5 1.5 d 7 d 1 At day 1, the width of plants in PR was significantly greater than STD (by 2.6%) and PF (by 8.3%). Figure 3. Cabbage: Vigour scores seven to 21 days after sowing and prior to feeding, May 23 6 Vigour Score - cabbage Mean vigour score 4 2 d 7 d 1 d 14 d 21 STC - POTSTC33 7

There were significant differences between plants grown in the three types of growing media; STD being one index point greater than PF, which in turn was.75 index points greater than PR by the end of the trial. As the latter were showing signs of N deficiency, half of each batch of plants was given supplementary feed. Post feeding data is shown in figure 5. Examples of plants graded 3 to 5 for vigour at day 21 are shown in figure 4. Figure 4. Cabbage: Vigour score reference material showing grades three to five on 3 th May 23 (day 21) Figure 5. Cabbage: Vigour scores 32 days after sowing with and without feeding, 1 th June 23 Vigour Score - fed & unfed cabbage plants Mean vigour score 8 7 6 5 4 3 2 1 fed unfed STC - POTSTC33 8

Figure 6. Cabbage: Examples of unfed plants from each treatment 32 days after sowing, 1 th June 23 PR PF STD Figures 7, 8 and 9. Cabbage: Examples of unfed and fed plants from each treatment at the final Assessment (day 32), 1 th June 23 STD PF PR At day 32, all fed plants were graded significantly higher than their unfed counterparts. In each case, the differences were approximately 1.5 index points. This shows clearly in Figures 7, 8 and 9. Irrespective of feeding STD plants were graded significantly higher than those in both PR and PF (by at least one index point). Figure 1. Cabbage: Fresh weight of five fed and unfed plants at end of trial (day 32), 1 th June 23 STC - POTSTC33 9

Mean weight per5 (g) Weight of five fed and unfed cabbage plants 14 12 1 8 6 4 2 fed unfed 32 days after sowing, all fed plants were significantly heavier than their unfed counterparts. There were also significant differences in fresh weight between all three types of growing media for both the fed and unfed groups of plants. In both groups, STD plants were heavier than PF plants and these were heavier than PR. Figure 11. Cabbage: Plants raised in all three treatments (with and without supplementary feed) six weeks after planting out in the field, 1 st August 23 Figure 11 shows the plants from all treatments (with and without supplementary feed) in the field towards the end of the growing season. There was no apparent difference between them. In summary, there was a very small but significant difference in the germination of cabbage seed between the three treatments; PR being approximately 1% better than STD and PR. Over the following 21 days, the vigour of the plants could be ranked in order STD, PF, PR. At that time, the plants in PR were showing symptoms of N deficiency and they responded well to the application of supplementary feed. At the end of the propagation phase, plants grown in STD were the most vigorous, although all plants that received supplementary feed were of acceptable quality. There was no apparent difference in growth after field planting. STC - POTSTC33 1

4.2 Courgette Patriot The final assessment was completed on 3 th May 23, 21 days after sowing. The number of seeds germinated, plant vigour score, plant width and height in each treatment are shown in table 2. Also included is the number of courgettes per plant in the field on 11 th July 23. The reference material showing examples of plants in each treatment and differences in root development are illustrated in photographs together with charts to aid interpretation of the data (figures 12 to 18). Table 2. 23 Courgette: Summary of assessment data 7 to 32 days after sowing, May and June Assessment Number Germinated (from 52) Vigour Score/Index Plant Width (cm) Plant Height (cm) Medium Mean (SD) and LSD on day after sowing 7 1 14 21 STD 53 (1.93) 5.13 (3) 52 (2.3) * PR 53.63 (.74) 53.13 (1.36) 52.88 (1.7) * PF 5.88 (2.75) 49.13 (3.23) 5.88 (3.4) * LSD 2.49 (df) 23 STD 1 () 2 () 4 () 5 () PR 2 () 2 () 3 () 3.38 (.52) PF 1.75 (.46) 1.5 () 3 () 4 () LSD.31 (df) 23 STD 8.9 (1.22) 11.8 (1.12) * PR 1.12 (.71) 11.3 (1.28) * PF 1.2 (.84) 11.6 (1.17) * LSD.31 (df) 119 Number of courgettes STD 6.6 per plant by 11 July PR 7. (day 63) PF 6.5 STD * * * 19.48 (2.25) PR * * * 13.68 (1.77) PF * * * 14.71 (1.63) LSD.49 (df) 119 * = data not recorded STC - POTSTC33 11

Figure 12. Courgette: Mean number of seeds germinated seven, ten and 14 days after sowing, May 23 6 Mean number of courgettes germinated (from 52) 4 2 d 7 d 1 d 14 There was no significant difference in the numbers of seeds germinated at day 14. Figure 13. Courgette: Vigour scores seven to 21 days after sowing, May 23 6 Vigour score - courgettes Mean vigour score 5 4 3 2 1 d 7 d 1 d 14 d 21 There were significant differences in the general vigour of plants at day 21. Those grown in STD were one index point better than PF, which in turn were.68 index points better than PR. Figures 14 and 15. Courgette: Vigour score reference material showing grades on 3 th May 23 (day 21) STC - POTSTC33 12

Figures 16 and 17. Courgette: Plant width and height during the trial, May 23 Mean plant width (cm) 14 12 1 8 6 4 2 Plant width - courgettes d 7 d 1 Mean plant height (cm) 25 2 15 1 5 Plant Height - courgettes d 21 At day ten, plants grown in STD were significantly wider than those grown in PR (by 4%) and similar in width to PF. At the end of the trial, there were significant differences in the height of plants between each of the treatments. Plants grown in STD were over 3% taller than those grown in PF, which in turn were nearly 8% taller than those in PR. There was a proliferation of root growth in PF, which is illustrated in the comparison with STD in figure 18 below. Figure 18. Courgette: Difference in root growth between the STD and PF treatments on 23 rd May 23 PF STD After planting in the field, all plants established well and there were no apparent differences in plant growth or development of courgettes by 11 th July 23 (day 63). The data is in table 2 but there is no photographic overview of the field crop. In summary, there was no significant difference in the germination of courgette in the three types of growing media but there were significant differences in their subsequent growth. By day 21, the three treatments could be ranked in the order STD, PF, PR. However, all the plants performed well after planting in the field and the numbers of fruit produced by day 63 were comparable. STC - POTSTC33 13

4.3 Leek Jolent The final assessment was completed on 1 th June 23, 32 days after sowing. The number of seeds germinated, plant vigour score, plant height and girth, and fresh weights of ten plants in each treatment are shown in table 3. Examples of plants in each treatment and an overview of the transplanted crop are illustrated in photographs together with charts to aid interpretation of the data (figures 19 to 26). Table 3. 23 Leek: Summary of assessment data seven to 32 days after sowing, May and June Assessment Number Germinated Vigour Score/Index Plant Height (cm) Plant Girth (mm) Fresh weight per 1 plants (g) Medium Mean (SD) and LSD on day after sowing 7 1 14 21 32 STD 266.75 (12.89) 277.75 (13.85) 292.75 (36.4) * * PR 273 (8.38) 275.75 (6.96) 278.88 (6.1) * * PF 261.5 (11.45) 269 (6.9) 269 (8.28) * * LSD 13.32 (df) 23 STD 1 () 2 () 2 () 3 () * PR 1 () 2 () 2 () 2.5 () * PF 1 () 2 () 2 () 2 () * LSD (df) 23 STD (F) * * * 22.2(3.5) STD (UF) * * * 13.86 (2.69) 21.5(2.6) PR (F) * * * 22.(2.84) PR (UF) * * * 13.52 (1) 18.61(2.9) PF (F) * * * 18.92(3.48) PF (UF) * * * 1.4 (1.3) 17.1(2.84) LSD.47.53 (df) 119 239 STD (F) * * * * 1.89(.3) STD (UF) * * * * 1.98(.34) PR (F) * * * * 2.11(.23) PR (UF) * * * * 1.81(.24) PF (F) * * * * 1.54(.3) PF (UF) * * * * 1.51(.35) LSD.5 (df) 239 STD (F) * * * * 6.12(.42) STD (UF) * * * * 5.96(.36) PR (F) * * * * 7.23(.64) PR (UF) * * * * 3.43(.31) PF (F) * * * * 4.35(.26) PF (UF) * * * * 3.15 (.79) LSD.32 (df) 23 F = plants received liquid feed twice a week from day 21 UF = plants received no liquid feed STC - POTSTC33 14

* = data not recorded Figure 19. Leek: Mean number of seeds germinated seven, ten and 14 days after sowing, May 23 Mean number of leeks germinated (from 38) Mean number germinated 35 3 25 2 15 1 5 d 7 d 1 d 14 At day 14, significantly more seeds had germinated in STD than either PF or PR by 5% and 9% respectively. Figure 2. Leek: Vigour scores seven to 21 days after sowing - before feeding, May 23 Vigour Score - leeks Mean vigour score 3.5 3 2.5 2 1.5 1.5 d 7 d 1 d 14 d 21 The vigour of plants was very consistent until day 14 and during this time there was no significant difference in growth between the three types of growing media. Thereafter, the PR and PF plants in particular appeared to be short of nitrogen and significant differences began to show between all the treatments, with STD best and PF worst. All the plants responded well to supplementary feed but those in the PF mix were still smaller at planting (figure 25). Figure 21 and 22. Leek: Plant height and girth of fed and unfed plants 32 days after sowing, 1 th June 23 STC - POTSTC33 15

Plant Height - fed & unfed leeks, d 32 Plant Girth - fed & unfed leeks, d 32 Mean plant height (cm) 25 2 15 1 5 fed unfed Mean plant girth (mm) 2.5 2 1.5 1.5 fed unfed Unfed plants grown in STD and PR were both significantly taller than PF plants by 3% or more and this pattern was repeated among the fed plants at the end of the trial 32 days after sowing. At the final assessment all fed plants in the GC based mixes (PR and PF) had significantly greater girth than their unfed counterparts but this was not true of the STD treatment. Plants in the PR mix responded most to supplementary feeding and by the end of the trial were significantly fatter and heavier than those grown in STD and PF, although this is not obvious from the plants illustrated in figures 24 and 25. Figure 23. Leek: Fresh weight of ten fed and unfed plants 32 days after sowing, 1 th June 23 Mean weight per 1 (g) 8 7 6 5 4 3 2 1 Weight of 1 fed & unfed leek plant fed unfed Figure 24. Leek: Examples of fed leek plants 32 days after sowing, 1 th June 23 PR PF STD STC - POTSTC33 16

Figure 25. Leek: Examples of fed leek plants on day 49, 27 th June 23 (three days before transplanting) PF PR STD Only the fed plants were planted out in the field. There was no apparent difference between them towards the end of the growing season (Figure 26). Figure 26. Leek: Plants raised in all three treatments (with and without supplementary feed) nearly 12 weeks after planting out in the field, 19 th September 23 PF PR STD In summary, germination was significantly better in STD than in either PF or PR, which were similar. Up to 14 days after sowing, there was no significant difference in growth between the three growing media treatments. All plants then began to suffer from shortage of N but this was most apparent for PF and PR. They all responded well to supplementary feed but, at the end of the propagation phase, fed plants in the PF mix were still significantly smaller, although of acceptable quality. Once transplanted, all treatments established well and there were no apparent differences in growth. STC - POTSTC33 17

4.4 Lettuce Roxette The final assessment was completed on 3 th May 23, 21 days after sowing. The number of seeds germinated, plant vigour score, plant width and height and fresh weight of ten plants in each treatment are shown in table 4. Examples of reference material and plants from each treatment are illustrated in photographs together with charts to aid interpretation of the data (figures 27 to 33). Table 4. Lettuce: Summary of assessment data seven to 21 days after sowing, May 23 Assessment Number Germinated (from 14) Vigour Score/ Index Plant Width (cm) Plant Height (cm) Weight per 1 plants (g) Medium Mean (SD) and LSD on day after sowing 7 1 14 21 STD 13 (1.6) 13.13 (1.13) 14 () * PR 13.25 (.71) 13.13 (.64) 13.88 (.35) * PF 95.63 (12.77) 97.38 (11.9) 98.25 (1.8) * LSD 6.43 (df) 23 STD 2 () 2 () 3 () 5 () PR 2 () 2 () 3 () 3 () PF 1 () 1 () 2 () 3.75 (.46) LSD.28 (df) 23 STD 2.52 (.31) 3.47 (.28) * * PR 1.83 (.21) 3.4 (.24) * * PF 1.84 (.29) 3.12 (.28) * * LSD.7 (df) 119 STD * * * 11.99 (.68) PR * * * 6.85 (.55) PF * * * 9.77(.49) LSD.15 (df) 119 STD * * * 32.76 (5.6) PR * * * 16.98 (2.47) PF * 23.2 (2.55) LSD 3.69 (df) 23 * = data not recorded There was much greater variation between replicates in PF than in either the STD or PR mixes, but there was no significant difference in the numbers of seeds germinated in the three treatments at day 14. STC - POTSTC33 18

Figure 27. Lettuce: Mean number of seeds germinated seven to 14 days after sowing, May 23 Mean number of lettuce germinated (from total of 14) Mean number germinated 12 1 8 6 4 2 d 7 d 1 d 14 Figure 28. Lettuce: Vigour score seven to 21 days after sowing, May 23 Lettuce - vigour score 6 5 Mean vigour score 4 3 2 1 d 7 d 1 d 14 d 21 Until 14 days after sowing, plants grown in STD and PR were similar and both were graded significantly above those grown in PF. However, the situation had changed by day 21 when STD was significantly more vigorous than PF, which in turn was significantly more vigorous than PR. Examples of plants from each vigour grade at the final assessment are shown in figures 29 and 3. Figures 29 and 3. Lettuce: Examples of plants in vigour grades three to five and plants from the three treatments at the final assessment, 3 th May 25 PR PF STD STC - POTSTC33 19

Figures 31 and 32. Lettuce: Plant width and height seven to 21 days after sowing, May 23 Lettuce - plant width Plant Height - lettuce Mean plant width (cm) 4 3 2 1 d 7 d 1 Mean plant height (cm) 14 12 1 8 6 4 2 d 21 Ten days after sowing plants grown in STD and PR were similar and both significantly wider (by approximately 1%) than those grown in PF. At the end of the propagation trial, there were significant differences in the height of plants. Plants grown in STD were significantly taller than those grown in PF (by 23%), which in turn were significantly taller than those in PR (by 43%). Figure 33. Lettuce: Fresh weight of ten plants at 21 days after sowing, 3 th May 23 Mean weight of 1 plants (gm) 35 3 25 2 15 1 5 d 21 At this final assessment, plants grown in STD were significantly heavier than those grown in PF, which in turn were significantly heavier than those in grown in PR (by approximately 4% in both cases). In summary, there were no significant differences in the germination of lettuce in the three types of growing media but there were significant differences in their subsequent growth. In the early stages, growth of plants in STD and PR were similar and both were marginally better than PF. However, the situation had changed by the end of the trial when there were large and significant differences between all three treatments. The differences show clearly in Figures 29 and 3 and the treatments can be ranked in the order STD, PF, PR. A comparable decline in performance of plants in PR towards the end of the trial was also observed with cabbage and leeks (sections 4.1 and 4.3). In those cases, the plants improved considerably when provided with supplementary feed - suggesting they had been deprived of nitrogen. STC - POTSTC33 2

4.5 Overall review Lettuce and courgette germinated equally well in all three growing media. Cabbage germination was marginally better in PR, while leek germination was best in STD. Seedling growth followed a similar trend in all four crops. Generally, plants in all treatments grew well until approximately 14 days after sowing, when those in the treatments including green compost (PR and PF but notably PR) appeared to become short of nitrogen, well before they were ready to be transplanted. This was most marked in cabbage and leeks and these crops responded well to the supplementary liquid feeding they were given. Although there were significant differences in size (especially between the STD and PR treatments) at the end of the propagation stage, all unfed lettuce and courgette plants and all fed cabbage and leek plants were of acceptable quality for transplanting. When transplanted in the field, all cabbage, courgette and leek plants established well and subsequent growth was by unaffected by the growing medium treatment. Overall, the trial suggest that a variety of vegetables could be propagated successfully in peat reduced and peat free growing media containing 25% v/v green compost and a base dressing of ammonium nitrate. However, more formulation work is required, to ensure that sufficient nitrogen is added to meet the needs of the more hungry crops - without adversely affecting germination. Although no data is presented, it was observed that the treatments containing green compost (PR and PF) produced particularly robust root balls and this was most evident when the transplants were allowed to dry back. No pest, disease or weed problems were encountered. STC - POTSTC33 21

5 Conclusions Germination Growing media incorporating a fine grade of green compost (less than 5mm) at 25% v/v (PR and PF), diluted with either fine peat or bark fines, matched the germination performance of a leading all peat proprietary potting medium in all crops except leek. Seedling development Good quality transplants can be produced in green compost formulations (PR and PF) provided sufficient base nitrogen is added to prevent premature starvation and the need for earlier supplementary feeding of the more hungry crops. Post planting establishment Field establishment was unaffected by growing medium treatment. STC - POTSTC33 22

Appendix 1 Trial protocol PEATERING OUT PROJECT Trial Protocol Trial type: Crop type: Site: Nursery Vegetable propagation Stockbridge Technology Centre, Cawood, Yorkshire. Trial No: POTSTC33 Start Week: 19/3 End Week: 22/3 (Courgette and Lettuce) 24/3 (Leek and Cabbage) Title: Replacement of sphagnum peat in the nursery mix using green compost +/- composted bark Treatments: Crops: Design: Uniform Treatment: Records: Distribution: Peatering Out Ltd John Adlam Arnie Rainbow Growing Media 1. Peatering Out Ltd PF 2. Peatering Out Ltd PR 3. STC s standard mix (peat-based) Cabbage Castello Courgette Patriot Leek Jolent Lettuce Roxette 3 treatments x 8 replicates = 24 trays of each of 4 crops = 96 plants total A sub-treatment for cabbage and leeks will be incorporated, with half of each batch of replicates receiving liquid feed twice weekly from 21 days after emergence. 1. Hand watered cell trays 2. Standard pest and disease programme 1. Analysis of each treatment mix before use, plus green compost, composted bark and peat, for nutritional and physical properties 2. Germination 3. Subjective assessment of plant vigour against graded standards 4. Plant width, height, girth and fresh weight 5. Establishment after planting in a field situation 6. Photographs of root balls and foliage STC Rob Jacobson STC - POTSTC33 23

Appendix 2 Analyses 2.1 Treatment mixes Units PF PR STD Lab. compacted bulk density g/l 42 315 438 Moisture content g/l 194 196 249 ph 1 6.6 6.2 5.8 Electrical conductivity 1 µs/cm 34 25 4 NH 4 -N mg/l 47 16 28 NO 3 -N mg/l 86 196 147 NH 4 + NO 3 N mg/l 133 212 175 1 1:5 extraction ratio STC - POTSTC33 24

2.2 Substrates Units Eco Melcourt Shamrock Green Grow Fine compost Bark peat Lab. compacted bulk density g/l 542 338 256 Moisture content % m/m 52.9 46.2 54.9 Moisture content g/l 287 156 14 LOI/DM % m/m 72.5 94.8 98.3 Total N % DM 1.27.35 1.16 C:N :1 13.1 13.3 34.1 ph 8.4 5.5 4.2 Electrical conductivity µs/cm 55 75 8 Extractable in water NH4 mg/l 8 <1 16 NO3 mg/l <5 <5 26 NH4+NO3 mg/l <13 <6 42 Chloride as Cl mg/l 48 25 4 Extractable in CaCl2+DTPA solution Phosphorus as P mg/l 65.7 5 Potassium as K mg/l 19 218 5 Magnesium as Mg mg/l 142 89 149 Sodium as Na mg/l 14 41 39 Calcium as Ca mg/l 114 Sulphur as S mg/l 21 12 14 Iron as Fe mg/l 48 23 19 Copper as Cu mg/l 1.2.1 Zinc as Zn mg/l 18 5.2 1.6 Manganese as Mn mg/l 26 12 2.5 Boron as B mg/l 1.5.7.4 Molybdenum as Mo mg/l <.1 <.1 <.1 CEC me/litre 179 134 167 Cellulose % DM 29.5 71.5 63.1 Lignin % DM 8.6 14.8 23.4 Hemicellulose % DM <2 <2 <2 Organic C by dichromate % DM 14.2 31.6 35.6 Organic C by LOI % m/m 16.6 36.1 38.5 PSD %w air-dried sample passing 31.5 mm 1. 1. 1. 16. mm 1. 1. 98.88 8. mm 98.72 1. 83.88 4. mm 9.74 99.26 71.4 2. mm 68.49 79.61 61.34 1. mm 29.13 51.6 5.46 Physical contaminants %w air-dried sample retained on 2. mm sieve Glass STC - POTSTC33 25

Metal Plastic Stone.1 Other 4.2.28 Total 4.2.28.1 STC - POTSTC33 26

Appendix 3 - Weighing sheet STC - POTSTC33 27