LINK Integrated Farming Systems (a field-scale comparison of arable rotations) Volume II: The economic evaluation of input decisions

Abstract

This report outlines the results from a five-year study, which commenced in April 1993. The study was designed to strengthen the economic interpretation of the main integrated Farming Systems project (0068/1/91) by checking the validity. of each major input decision. The project was located at four sites: ADAS Rosemaund, Hereford; ADAS Boxworth, Cambs.; ADAS High Mowthorpe, North Yorkshire; Pathhead, Midlothian.

The LINK funded, Integrated Farming Systems experiment compared a conventional rotation with a sustainable, integrated farming system (IFS). The conventional practice reflected local practice offarmers who where 'technically competent, financially aware and risk-averse'. The IFS system incorporated where possible the latest results of research and development to optimise inputs in an 'advanced management system'. The objective was to maintain profitability, while reducing off-farm inputs, by a process of modifying the crop rotation and management techniques to minimise or avoid major pest and disease problems and nitrogen leaching. The validation experiment was designed to check the validity of each major input decision. For each decision made on the IFS rotation, a single factor comparison between the basic IFS and an alternative 'test' treatment was made. This resulted in 87 individual experiments on all sites, spread over six crop types, resulting in a total of 757 comparisons. Assessments were done in each experiment to establish the efficiency of treatments on disease, pest or weed incidence, and to measure yield and crop quality. A financial evaluation was also done.

Trial design began as randomised blocks but the design was altered in 1996 and 1997 to improve the precision (i.e. the power to detect .significant differences between treatments). The majority of the trials were a designs (optimal set of incomplete blocks), a few trials were designed with fractional factorial treatment structures. The statistical evolution of the validation experiments over time has allowed the accurate estimation of differences between any two of the treatments. The information on experiment design from this study should be applicable in the wider arable experimentation context and it is recommended that it be considered by other researchers for other projects.

The use of the validation experiment has allowed testing of alternative or 'conventional' treatments. This information can then be used in future years to refine decisions made in the developing IFS system. The inclusion of these trials has provided a valuable management tool in determining the factors limiting further reductions in inputs, and optimising profitable output.

The validation experiment has indicated areas of importance to be considered when developing an Integrated Farming system. Overall, this study demonstrated that the treatment adopted in the LINK-IFS project had been bettered by alternatives selected for test in the validation studies in only 7.0% of cases. Showing that decisions were optimised in the LINK­ IPS project in the vast majority of cases. In cereals, variety choice has a key impact on the profitability of the farming system when reducing inputs. Initially, herbicide decisions in the Integrated system moved away from the use of autumn residual herbicides to try and minimise the risk of pesticide leaching, and contact-acting products (with a theoretically lower leaching risk) were used in the spring. The validation experiments demonstrated that where early weed control was important, then autumn residual herbicides produced better more consistent results. A prediction system to indicate the numbers and species of weeds to be tackled would be a valuable tool in development of an Integrated Farming System. Generally nitrogen rates calculated from use of ADAS Fertiplan and soil nitrogen analysis were optimal for winter wheat, However in the small number of cases where estimates were sub-optimal, yield losses were severe and profitability severely decreased. Nitrogen rates calculated from soil nitrogen analyses were 30 kg/ha too low overall on spring barley at Pathhead.

The fungicide programmes applied within IFS have been optimal, only 6.3% of alternative validation decisions resulted in higher yields than the IFS. There were limited occasions for the use of insecticides but only one validation treatment out of 41 comparisons in wheat lead to a higher yield than the integrated system, this was due to prevention of re-infestation by aphids during grain filling.

Weed control in spring beans was very difficult in the absence of pre-emergence residual herbicides, where opportunities for post-emergence control are limited and expensive. Information on appropriate fungicide dose for disease control in winter beans is limited and more research is required to optimise fungicide inputs and evaluate effects of disease control, which may not always be economically viable in such crops.

Mechanical weeding in potatoes was a successful technique used in most seasons when soil conditions were dry at the time of the first weed flush. It was most successful when used in conjunction with low-dose post-emergence herbicides. There were less opportunities to use mechanical weeding in combinable crops due to the combination of dry soil conditions, small non-tap rooted weeds and early crop growth stage which are required to optimise its effectiveness.

The majority of decisions (93%) made on the winter linseed were correct, but there is a need to increase the information on disease control programmes for winter linseed, a relatively new crop in the UK, to optimise crop output.

The results from the main LINK-IFS report state a non statistically significant production margin difference between the conventional and integrated systems of only £17 /ha. From the validation experiment yield was significantly bettered by alternatives in only 7.0% of cases, but these were not always associated with improvements in gross margin. The results indicate scope for improving the gross margins of the l'FS system up to the level of the conventional system, through optimising weed control, better prediction of nitrogen requirements and maximising production from breakcrops. Generally improved decision making is needed to refine Integrated Farming Systems and minimise inputs by allowing better targeting, and better prediction of problem situations, allowing growers to balance risks with the benefit of the best information available. Decision support systems which can give growers more information about the likely risk of decisions would help to give growers confidence about their decision making and allow them to more readily adopt integrated systems. Thresholds used in such systems must be well established and robust if growers are to have the confidence to move to more integrated systems. As well as sophisticated decision support systems, growers also need access to simple biological information about pests and diseases to allow identification and determination of pest and disease levels.

The information from the validation study has quantified the effects of some of the risks taken within the LINK Integrated Farming Systems project. A technique such as the validation study should be used extensively within any field scale experiments with limited replication. The statistical design has been shown to be an important factor in this type of study and the field experimenter and statistician should work closely to optimise benefits from the research.