Influence of level of self-sufficiency on the nutrient budgets of an organic dairy farm (OF0180)

This is the final report of Defra project OF0180 In 1998, the organic dairy herd at Ty Gwyn, Trawsgoed was split into two herds to examine the physical and financial implications of adopting different feeding strategies and levels of feed self-sufficiency (DEFRA Project OF0146). A self-sufficient system (SS) in which cows were fed a high forage diet supplemented with home-grown cereals was compared with a system in which concentrate feeds were purchased from outside the farm (PC). The present study determined nutrient budgets for the two systems and used models to estimate the various forms of N loss. These studies were supported by field studies to provide additional information about areas of uncertainty identified in previous budget calculations. Specific objectives were: 1. To determine whole-farm budgets and internal flows of N, P and K for the SS and PC organic dairy systems at Ty Gwyn. 2. To measure the effect of slurry applications on N fixation in grass/clover fields at Ty Gwyn and effects on the uptake of P, K and Mg. 3. To measure possible changes in the P and K content of soils in the SS and PC systems at Ty Gwyn and evaluate recommended laboratory tests as indicators of P and K deficiencies in these soils. The attached main report starts with a detailed Executive Summary

Organic farming: technology transfer (Environmental impact and soil fertility) (OF0405)

This project covered two separate activities, but both were examples of technology transfer, relating to organic farming: 1. Developing a science-based report, which covered an assessment of the environmental impacts of organic farming. Defra’s Action Plan to Develop Organic Food and Farming included as Annexe 3 an assessment of the environmental impacts of organic farming. This paper was prepared by a Subgroup of the Action Plan for Organic Farming. Its purpose was to summarise the Subgroup’s views of the likely comparative effects of organic and conventional farming on the environment. However, to be robust and defensible, the assessment needs to be supported by scientific data. Although the report was based on such an assessment, the scientific data were not summarised and this needed to be done. The objective of this part of the project was therefore to collate and publish on the Defra website the evidence that underpinned the overall conclusions. 2. Preparation of a booklet to provide guidelines for managing soil fertility in organic farming. Organic farming aims to create an economically and environmentally sustainable agriculture, with the emphasis placed on self-sustaining biological systems, rather than external inputs. Building soil fertility is central to this ethos. ‘Soil fertility’ can be considered as a measure of the soil’s ability to sustain satisfactory crop growth, both in the short- and longer-term, and it is determined by a set of interactions between the soil’s physical environment, chemical environment and biological activity. The aim of recent Defra-funded projects has been, therefore, to provide a better scientific understanding of ‘soil fertility’ under organic farming, in line with Defra’s policy objective of greater technical support to organic farming. The aim here was to prepare a booklet based on the findings of Defra-funded project OF0164 ‘Soil fertility in organically farmed soils’

Legume based plant mixtures for delivery of multiple ecosystem services: An overview of benefits

As costs for mineral fertilizers rise, legume-based leys are recognised as a potential alternative nitrogen source for crops. Here we demonstrate that including species-rich legume-based leys in the rotation helps to maximize synergies between agricultural productivity and other ecosystem services. By using functionally diverse plant species mixtures these services can be optimised and fine-tuned to regional and farm-specific needs. Field experiments run over three years at multiple locations showed that the stability of ley performance was greater in multi-species mixtures than in legume monocultures. In addition, mixing different legume species in the ley helps to suppress both early and late weeds. Further, combining complementary phenologies of different legume species extended forage availability for key pollinator species. Finally, widening the range of legume species increases opportunities to build short term leys into rotations on conventional farms via cover cropping or undersowing

Development of the FBC model to estimate the nitrogen available from fertility-building crops in organic rotations

The FBC (Fertility Building Crops) model has been developed as a planning tool to provide organic farmers with information about how much nitrogen will be available in the soil at different stages following the ley phase of the rotation. It predicts the likely crop yields under this level of nitrogen supply and provides an estimate of how much nitrogen will be lost by leaching and denitrification so that if necessary the grower can examine the effects of modifying the rotation to improve the efficiency of nitrogen use and minimise losses. The model is easy to use and requires only the sort of information that is readily available to commercial growers. Although it appears to provide realistic simulations of a range of crop rotations and conditions, it has not yet been fully validated

Nutrient budgets as a tool for researchers and farmers.

This report was presented at the UK Organic Research 2002 Conference. Whole-farm budgets for N, P and K have been determined for the organic dairy farm at Trawsgoed in mid-Wales and used to assess the potential value of budgets as a management tool for optimising nutrient use. Most of the information needed by farmers to calculate whole-farm budgets is available on commercial farms but an important limitation is the difficulty of estimating N fixation. Whole-farm budgets do not provide sufficient information for use in managing nutrient flows, which requires moredetailed field budgets. Information for determining budgets at the field scale is less readily available. The studies have examined the use of farm and field budgets to provide an estimate of the nutrient content of animal manures and slurries produced on the farm