IACR-Long Ashton Research Station, University of Bristol, Bristol BS18 9AF, UK

Background and objectives
Integrated production is an alternative approach to crop production and crop protection that places emphasis on a whole-systems approach, rather than on the individual disciplines within them. It involves defining, integrating and exploiting the main variables and component interactions of crop husbandry practices that minimize the risk of diseases becoming sufficiently severe, and thereby offer greater flexibility in disease control options [1]. A carefully selected crop rotation with crops established using minimum tillage, combined with cultivar resistance and rational manipulation of crop structure by adjustments in sowing date, nitrogen amounts and timing, offers opportunities to decrease the incidence, rate of development and severity of attack of a range of arable crop diseases that limit production.

Materials and methods
Established in 1989, the Less-Intensive Farming and Environment (LIFE) project at Long Ashton is a long-term, farm-scale experiment occupying 23 ha. It now comprises 21 field units (each ca 1 ha) in order to compare, over seven-course arable crop rotations, a conventional production system which aims to achieve optimal yields and maximize profits, with advanced integrated production systems which are designed to be less reliant upon agrochemical inputs and to be more environmentally benign [2]. In the conventional system, high-yielding crops are established in mid-September, following a traditional plough, then grown under recommended practices for integrated crop management (ICM) to reflect current farmer practice and input levels. In the advanced integrated production systems, disease-resistant crops are established in October, using a two-pass soil conservation tillage system, and managed thereafter according to strict guidelines for integrated production.

Results and conclusions
Within the LIFE project, selection and placement of specific crops in crop sequences, by growing only first wheats and optimizing the use of profitable break crops, reduced potential carry-over and infection frequency of soil- and trash-borne, splash-dispersed diseases from crop to crop. In addition, delaying sowing dates of all winter cereal crops from September until October reduced primary disease incidence. Furthermore, the more judicious use and modified timing of applied nitrogen in spring influenced crop canopy structure and leaf susceptibility sufficiently to reduce subsequent progress and severity of attack of major foliar diseases (powdery mildews, rusts, Septoria spp., Rhynchosporium and net blotch). Minimum tillage techniques leave much infective crop debris on or near the soil surface, often leading to increased inoculum potential, and incidence and autumn severity of trash-borne diseases in continuous cereals. However, this risk is minimized by the selected crop rotation. In addition, the presence of surface crop residues provide semi-natural habitats for increased numbers of polyphagous predators which, when combined with later sowing, reduce the autumn ingress, survival and secondary spread of the aphid vectors of barley yellow dwarf virus, thereby providing natural regulation and acceptable control of this disease without chemical intervention. This whole-systems approach has led to the development of alternative strategies that permitted exploitation of the most appropriate fungicide and dose in order to interrupt cyclic regeneration of pathogens or protect crops until the end of grain filling. Intervention decision models were either targeted to scaled-up disease thresholds or nitrogen-induced crop disease response, and provided cost-effective disease control with significant reductions in both the frequency of applications and the amounts of active ingredient applied.

1. Jordan VWL, Hutcheon JA, 1995. In Hewitt HG, ed., A Vital Role for Fungicides in Cereal Production. Bios Scientific, Oxford, pp. 129-139.
2. Jordan VWL, Hutcheon JA, Donaldson GVD, 1997. Aspects of Applied Biology 50, 419-429.