Farm Table says:
The Overview of a Long Term Management Trial
Evidence suggests that organic arable cropping systems generally produce lower, more variable yields than systems employing synthetic fertilisers and chemical crop protection measures. The use of data from a factorial systems trial has enabled an assessment of the relative importance of the crop protection, fertilisation and pre-crop related factors affecting yield and quality of potatoes grown under organic farming systems.
The main objectives of the study presented were:
- quantify the relative effects of fertilization regimes (mineral NPK versus composted cattle manure) and crop protection practices (based on standard pesticide, fungicide and herbicide treatments or mechanical weed control and Cu-fungicides only)
- investigate interactions between fertilization regimes and crop protection regimes
- investigate the relative effects of climatic and agronomic drivers on potato yield and quality parameters
The study has demonstrated that inefficient nutrient supply (especially N) from organic fertilizers contributed more than the limited use of chemo-synthetic crop protection products to the lower yield in organic compared to conventional potato production. In particular, it appears that the effects of late blight on yield were lower than previously thought. Results also indicated that climatic drivers may affect yields in organic systems more than in conventional systems (e.g. via their effect of N-mineralization rates from organic matter in soil), but results from a wider range of years would be required to model the relative yield stability in contrasting potato production systems.
These findings suggest that research focused on:
- identifying improved fertilization regimes for organic systems (e.g. the use of organic fertilizers with a greater available N-content)
- breeding for improved N uptake and utilization efficiency from organic fertilizers is at least as important as on-going efforts to breed for resistance to late blight (and other diseases and pests)
- develop novel crop protection products/approaches for organic potato production systems.
Rapidly increasing cost and the limited availability/non-renewable nature of mineral fertilizers are likely to result in an increase in the recycling of organic waste to agricultural land and an overall increase in the use of organic fertilizers, with countries such as China already setting targets for increases in organic fertilizer use. Improving the nutrient use efficiency of organic fertilizers in crops such as potato is therefore an important goal for both organic and conventional production systems.