Page 40 - Simply Vegetables Spring 2024

All peat-free – all good?
Comparison of yields from three makes of peat-free compost growing Phaseolus Coccineus in pots on hard standing. Outdoor trial at Waltham St Lawrence, Berkshire, 27 June–25 September 2023
This was Trial 6 in a series of annual trials of using a system enabling climbing runner beans to be grown other than in cultivated ground (for example in schoolrooms, occupational therapy units, hard standing areas in community and therapy gardens).
The system comprises self-assembly support frame with compost, pot,
saucer, seeds, and fertilisers. It is hoped that, through visibility in these settings, households without a garden may be encouraged to grow this popular vegetable – on patios, balconies, and decking (A recent Which? Gardening report1* on survey of over 4,500 gardeners stated runner beans to be the second most popular vegetable (grown by 50%) after tomatoes (75%)).
The frame design provides for the plants to grow mainly horizontally; the height is set at a suitable height for children of primary school age and for adults needing to remain seated – taking up minimal space.
While the focus of the trial was on the yields from each substrate, they (and other elements) were also assessed on suitability for the uses described above where areas need to be kept clean and dry as far as possible.
Cultivation-wise, the most important year to year change was a switch to using some peat-free substrates in 2019, and then peat free only in 2021, when three makes of peat-free compost from reputable producers were used and yields compared.
A large difference was noted between highest and lowest with the lowest being barely satisfactory at 566g per plant. Now, two years later peat-free composts are still said to be ‘unreliable, inconsistent resulting in poor or no growth’ (Article by Editor, Simply Vegetables, Autumn edition 2023) a.
In Horticulture Week (2 Nov 2023) The Responsible Sourcing Scheme for Growing Media called for industry-wide standards legislation.
This year’s trial used the most successful peat-free compost from 2021 and
Peat free composts used
compared the yield with results from two further makes in the hope of arriving at a reliable growing system to recommend to growers to use with the frame.
SCHEME OF TRIAL
Layout – see photographs.
MATERIALS AND METHODS
Peat-free composts
Incredipeatfree® Thompson & Morgan – the most successful of the three makes grown in 2021 trial – is packed in an unwieldy 70-litre bag. It is not available in garden centres. On opening the bags, this substrate was seen to be much drier than the others
Homebase peat-free, and Miracle-Gro® premium all-purpose peat-free – both ‘best buys’ last year in Which? Gardening. These come packed in convenient 10 litre bags. Both are available online. Miracle-Gro® (Evergreen Garden) is widely available in garden centres and supermarkets.
The Miracle-Gro® product was tried
with liquid fertiliser in 2020 and produced a satisfactory yield (777.5g per plant). A coir product (Growlite®) with same liquid fertiliser also produced a good yield – 835.2g). However, this requires hydrating 5Kg blocks to 60 litres of material) – laborious and untidy – so unsuitable for the circumstance in which it might be used).
Fertilisers
Early trials showed a significant improvement in yields from runner beans in pots when liquid fertilisers used with peat composts, and in 2020 they were used with peat-free composts also.
In house pots
However, growers found it difficult to keep an area clean and dry using the liquid fertiliser (Tomorite®) which requires one gallon of water per plant). More convenient slow-release granular fertilisers were used in 2021 and in this year’s trial.
a) Products from the makers of the
composts in the trial – with Miracle-Gro® continuous slow release plant food, and with Incredipeatfree® Incredicrop® slow release controlled plant feed. Directions for use of these were clear – 30g per
10 litres, 40g per 10 litres of compost
respectively.
b) There being no equivalent product
in the Homebase range, I chose a Which? Gardening best buy this year
– Osmocote® Controlled-Release Plant Food. Directions for use are 3–5 tablets for compost in a pot with 20cm diameter. Three tablets per pot were used in the absence of precise instructions.
Containers
Textile pots (Vigoroot®) were used successfully in 2021 but seepage through the fabric makes it hard to keep the area clean and dry. They were replaced by bamboo fibre pots in this year’s trial. Three of these, however, split and recyclable polystyrene will be used in future.
Propagation and potting up
The same compost used for both (to keep
the operation simple for the grower) – the compost used for sowing being re-used mixed into the compost for potting up, making a total of ten litres of compost per plant.
The fertilisers were mixed into the compost before planting the seedlings.
Pots were filled with to the rim of the pot, any compost remaining kept back and used to top up – objective being to ensure that ten litres of substrate were used for every plant.
Cultivation proceeded as in previous trials (Journal available) with foliage rimmed to 30cm above height of horizontal bar once plant fully grown.
Positioning of frames
Each of the sets formed a line running east to west thus having the very similar exposure to sun and weather (See photo).
Direction of growth
Stems were fed through loops of twine along the bars as previously. Directing stems down the second vertical proved difficult and produced relatively few beans.
40 Simply Vegetables
ANTHONY BOYD