The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 287

of leguminous green manures demonstrated that cut and mulched
red clover can supply up to 370 kg N ha −1 year −1 (Stopes et al ., 1996b).
Although the green manures may supply adequate nitrogen for the crop
rotation, little was known about the maintenance of soil organic matter and
the levels of phosphorus and potassium in the absence of either livestock
manures or soluble fertilizer inputs. With the increasing interest in stockless
farming systems, Elm Farm Research Centre (EFRC) established, in 1987,
an organic stockless trial to examine the agronomic and environmental
implications for organic all-arable farming systems.

Materials and Methods

The trial site was established at Elm Farm Research Centre (national grid
reference, SU414 654) at an altitude of ~60 m, with an average annual
rainfall of 710 mm year. The soil type was a clay loam of the Wickham
series (Jarvis et al ., 1984) with organic matter levels that range from 2.42 to
5.7% across the farm.
The whole farm site was converted to organic production, with Soil
Association certification in 1985. The farm operated a 4-year grass-clover
ley, 1 year winter wheat and 1 year winter oat rotation. The trial site had
previously been in a 5-year white clover-grass ley. In 1987, three 4-year
rotations were established in three complete randomized blocks (Table
4.9.1). Every course of every rotation was present in each year, giving a total
of 36 plots, each 20

12 m.
Ploughing, seedbed preparation, drilling, planting, in-crop weed con-
trol and potato harvesting were carried out using standard farm equipment,
in accordance with farm practice. Cereal crops and the field beans were
harvested using a trial plot combine harvester. Throughout the experiment,
and in accordance with Soil Association Standards, rock phosphate was
applied to a maximum rate of 180 kg ha −1 of P 2 O 5 during the green manure
phase of the rotations, the rate chosen according to soil analysis and the
requirement of the subsequent crops. Lime was also applied to a maximum
rate of 2 t ha −1 of CaO per year. Only crop residues were returned and there

×

Table 4.9.1. Stockless rotations in the EFRC replicated experiment 1987-1998.

Course

Rotation 1 2 3 4

A Red clover Winter wheat Winter wheat Spring oats

B Red clover Potatoes Winter wheat Winter oats

C Red clover Winter wheat Winter beans Winter wheat