Abstract:
Organic matter addition influences soil function (respiration/ decomposition) and
community structure (PLFA/ NLFA community profiles) which result in changes
to the provision of soil derived ecosystem services. Additions of organic matter to
gardens (e.g. composts, mulches, soil conditioners) is a widespread practice both
globally and in the UK. Research on the long-term cumulative impact of annual
additions to UK gardens is limited. A field trial, set-up in 2007, at the Royal
Horticultural Society’s Wisley Gardens site, was used to examine the changes to
soil chemical, physical and biological soil quality indicators following 12 years of
different soil organic matter additions. Additions varied in carbon-to-nitrogen
ratios (C/N), physical structure and macro/ micro-nutrient profiles. The
amendments used in the trial included composted bark, bracken, stable manure,
garden compost, spent mushroom growing compost, peat, fertiliser (rate adjusted
each year to meet plant growth requirements) and controls; no organic matter
addition and no plant sown, no organic matter addition and plant sown. Lab
studies were designed following analyses of amendment legacy effects in field
trial plots to further examine the effects of addition on microbiological indicators
of soil function, health and quality. Reviewing long term chemical and physical
data from the field trial highlighted significant effects of organic matter additions
on soil micro- and macro-nutrients. Recommendations for garden industry were
made from the findings and include the need for labelling standards for compost
material packaging to reduce unwanted environmental impacts of use. Organic
matter treatment to clay-loam textured soil significantly increased microbial
respiration and shifted microbial community structure. The effects were distinct
and dependent on composition of the organic matter applied. The horticultural
sector has outlined targets for reducing the impact of garden practise on drivers
of climate change. This study aligns with literature which seeks to understand
common practise in order to improve economic and environmental sustainability.
