CA in the UK

The world is steadily progressing with the idea of conservation agriculture (CA).  Current estimates are that there are over 125 million hectares of agricultural land under CA - still only 9% of the global cropped area but a positive start. However, as would be expected in the early stages of adoption, there are pockets of widespread adoption of CA and others where it has barely started.  The American continent has over 80% of the world area of CA, Australia and New Zealand have 15% while Europe has only 1%; and much of that is in permanent tree crops.

The CA concept has three basic principles:
  1. No tillage of the soil and only enough disturbance to place seed and fertilizer at the correct depths.
  2. Maintenance of organic soil cover throughout the year.  This means retaining crop residues and planting through them.  It can also mean planting crops specifically to maintain soil cover after harvest of the main crop.
  3. Diversifying crop rotations and associations as a means of controlling pests, diseases and weeds, and enhancing soil fertility.
The UK was, in the 1970s, a leader in the application and development of no-till agriculture.  This was before cereal straw burning was banned and the practice was to burn off crop residues and plant into the residual ash.  This was a quick, easy and cheap method of crop establishment and by 1974 some 200 000 ha of cereals grown in the country were sown with no-till drills.  One of the leading manufacturers of these machines was Bettinson and in fact, the design principles of the Bettinson 3D triple disc machine were incorporated into the Brazilian Semeato no-till machines following testing by Brazilian CA pioneers in the late 1970s.

There is little doubt that in the UK our soils are under threat.  Farmers appear to have a strong conviction that tillage is needed to control weeds, especially black-grass (Alopecurus myosuroides) and there is further suspicion that pests, especially slugs, thrive in crop residues.  Then the damage done to soil structure by the passage of farm machinery (including tillage machinery) which is not confined to controlled traffic lanes, requires tillage to ameliorate the problem.  As a result, destructive soil tillage is still practised even when the resulting damage is evident and energy costs are constantly on the increase.  For example, ploughing and planting up and down slopes is a sure way to provoke soil erosion and a consequent loss of soil fertility as the smaller, nutrient-laden particles are preferentially removed.  Lost nutrients need to be replenished and nitrogen fertilizer requires expensive fossil energy to produce.  N fertilizer prices increased fivefold between 2005 and 2008. Rising world cereal prices - wheat is currently (June 2011) at $US 326/tonne -  may mask the impact of rising production costs, but in a competitive global market such a production model is not viable.


The following photographs show examples of the deleterious effects of over-zealous soil tillage in the UK which I observed while walking the Icknield Way (IW), the Ridgeway (R), the Greensand Ridge (GRW), the John Bunyan Trail (JBT), the North Bedfordshire Heritage Trail (NBHT) and the Three Shires Way (TSW) in southern England recently (see relevant notes on the Walks page for further details).

 
 Ploughing and planting up and down slopes is a sure way to provoke soil erosion. (R14)  The consequences of ploughing steep slopes are evident in this picture as the uphill field headlands are starkly white and unproductive. (R9)  Soil on the up-slope side of this hedge remnant has, over the years, been retained and accumulated.  Sedimentation against a hedgeline is a clear indication of erosion processes in action. (R12)
 Another badly eroded headland. (R12)
 
 Soil bereft of organic matter. (R12)
 An example of over-deep ploughing. (R2) Heavy machinery destroys structure and compacts the soil at depth so limiting root growth and water storage capacity. (IW22)
In this picture straw bales have been split and spread over the soil as a protective and ameliorative measure. (IW22)
 
 

 
 
 Soil erosion from run-off in unprotected tractor wheelings (GRW8)  Ploughing at right angles to the contours (JBT1)  Black grass is a notorious weed of arable crops that can be controlled with no-till as part of CA (JBT7)  Beds formed after deep ploughing running up and down the slope provoke serious soil erosion.  Reduced tillage, permanent beds and organic soil cover will minimize the damge (JBT11)
 
 
 
 
 Soil with weakened structure as a result of ploughing will not withstand wheeled traffic when it is at field capacity.  Essential phytosanitary operations can result in deep deformation of structureless soils.  No-till and organic soil cover will help to ameliorate this situation  Hedge removal not only allows accumulated soil to be eroded, it also destroys windbreaks and, most importantly, wildlife habitat (NBHT4)  Cultivation (with ploughs, discs or tines) compacts soils, destroys soil biota and reduces pore spaces and natural channels.  Infltration rates can be cut by up to 50% and so runoff and soil erosion rapidly ensue during rain (NBHT3)  River banks should be protected against cultivation and cattle trampling.  Riparian woodland buffer zones help to dissipate stream energy, control erosion and reduce flooding whilst at the same time offering wildlife habitats (NBHT5) 
 

 
 
 

 Sheet erosion on sloping soils (NBHT6)  Sheet erosion will convert to rill erosion as runoff and slope increase (NBHT6)  Erosion of tilled soil resulting from impeded drainage (NBHT7)  Damage to physical works on an unprotected stream bank (NBHT10)
 
 

 

 
 Stream bank severely eroded due to the absence of vegetative cover  (NBHT10)  Severe rill erosion caused by the unprecedented rains of Jan & Feb 2014  Without stream bank protection with trees, grazing animals will cause damage and provoke erosion

There are, however, hopeful signs.  For example the use of agroforestry practices to combine and complement forestry, agriculture and livestock enterprises for environmental protection and biodiversity enhancement.
 
 
An agropastoral agroforestry system.  Such systems are good for both species conservation, biodiversity enhancement and hillside protection (R18)
 A hedge protecting a slope. (IW9)  A windbreak protecting fragile sandy soil in the Brecks (IW24) Oil seed rape broadcast on to wheat stubble with no tillage
(GRW4 & GRW9)
 
 
 
 A knife roller, used for bracken control but ideal for cover crop, weed and crop residue management as well! (GRW11)  No-till stubble will trap wind-blown snow and be a reservoir for crop growth in the following season (NBHT4)  A Claydon (www.claydondrills.com) strip-till seed drill at work in wheat stubble (NBHT6)  A field recently sown directly through last season's cereal residue.  Eliminating tillage helps timely planting and is especially useful in 'difficult' (cold and wet) seasons (NBHT8)
 
 
 
 
 No-till field beans emerge from cereal residue.  Rotating legumes and cereals is good CA practice (NBHT8)  Although grown for game birds, this mixture of Sorghum, Phacelia, Fagopyrum and Raphanus species would be an ideal CA cover crop (NBHT 16)  No-till winter wheat survived the heavy rainfall in the UK in early 2014  Claas combine with straw spreader for subsequent direct seeding (TSW 11)
 
 
 
 
 Autocast broadcaster for OSR behind the combine header (TSW 11) Cambridge roll to ensure good seed-soil contact after broadcasting OSR (TSW 11) Spreading FYM to increase soil OM and hence enhance structure, health and fertility (TSW 13) Dale 8 m Ecodrill direct drilling in stubble with crop residues and FYM applied to the surface (TSW 13)

 
 
These issues are being debated in the agricultural development community. Here are some of my contributions to the debate that have been published in Landwards, the professional journal of the Institution of Agricultural Engineers in the UK. 

Letter to the Editor: Landwards Vol 64 No 1 Spring 2009 page 9
Letter to the Editor: Landwards Vol 66 No 2 Summer 2011 page 10
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