Introduction
Soil organic matter (SOM) contains a large part of the soil's reserve of nutrients; it enhances stability in unstable soils, improves drought tolerance on light soils and improves workability in heavy soils.

Soil health depends on the presence of a varied and active population of micro-organisms.  These release nutrients from soil organic matter and chemical compounds.  In addition, the micro-organisms break down SOM and crop residues and during this process create gums that cement soil particles together, thus stabilising soil structures. 

A decline in SOM will adversely affect soil structure and stability, water retaining properties, biological activity and the retention of crop nutrients.  It may also in the medium and long term, make the soil more vulnerable to erosion, compaction, acidification, nutrient deficiency and drought.

Over the last twenty to thirty years SOM has declined by a noticeable amount on many soils. The traditional intensive cultivations used for some crops have, over time, contributed to this decline by causing oxidation of soil organic matter.

Incorporation of crop residues by shallow cultivation rather than by deep ploughing will improve structural stability and, through microbial activity in this upper layer, encourage more nutrient cycling by releasing nutrients from the incorporated matter thereby releasing some nitrogen before planting.

Adding organic manures in compliance with NVZ rules is beneficial as they encourage soil organisms to release bonding agents which stabilise the soil and thus reduce the potential for erosion, capping and compaction.

Organic matter as it applies to different sectors 

Pigs
Outdoor pigs contribute important plant nutrients to the soil.  Most sites are occupied by pigs for a two-year period, however a significant proportion of the nitrogen deposited can be released in the second year, unless good crop cover can be retained.  Establishing grass cover in advance of the pigs arriving on site, perhaps using one year set-a-side, permits the cover to be largely retained for the two years.  The cover reduces nitrate leaching and in some instances phosphate losses as well as helping to reduce the likelihood of soil erosion which is the main cause of phosphorus loss.  In common with other livestock enterprises, the manure which pigs produce helps to maintain soil organic matter content.

BPEX Soil management plan for outdoor pig keepers    (127kb)

Potatoes
BPC Info on use of organic fertilisers and composts from R&D. 
Cross compliance meetings (1200 growers)
Compaction review includes information on relationship between surface capping and organic matter.

BBRO
Beet growers guide, sugarbeet portal, Beet review magazine

HGCA
Project progress 6: Using animal manures on arable crops 2 page doc (2000)

Topic sheet 64: Using manures and biosolids on cereal crops - summary of findings of HGCA sponsored research by ADAS (Winter 2002/2003). 2 page doc.

ARF workshop Sustainable use of organic wastes on agricultural land.
7&8th Sept 2004 for 40 invited delegates.
Field demos in 2000, 2001.
Report (£10) on integrating organic manures, slurries, biosolids as nutrient sources in arable rotations May 2003.
MDC
Grass+ programme

HDC
2 fact sheets on options for soil sterilization
Many fact sheets on soil-borne diseases specific to HDC crops

Web
SMI.org.uk - publications
Environmentsensitivefarming.co.uk - ppt on GAEC for soils, soil husbandry (2006)
word doc describing organic matter and GAEC (2005)
Publications: SMI - Contributions and interactions of cultivations and rotations to soil quality, protection and profitable production
NSRI - Reports maintenance of organic matter status

Workshops
Environment Sensitive Farming
SMI
LEAF
FWAG
NSRi

Courses
Harper Adams College
NSRI

IGER - Grassland Development Farms