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

Terrestrial organic carbon storage in a British moorland

Accurate estimates for the size of terrestrial organic carbon (C) stores are needed to determine their importance in regulating atmospheric CO2 concentrations. The C stored in vegetation and soil components of a British moorland was evaluated in order to: (i) investigate the importance of these ecosystems for C storage and (ii) test the accuracy of the United Kingdom's terrestrial C inventory. The area of vegetation and soil types was determined using existing digitized maps and a Geographical Information System (GIS). The importance of evaluating C storage using 2D area projections, as opposed to true surface areas, was investigated and found to be largely insignificant. Vegetation C storage was estimated from published results of productivity studies at the site supplemented by field sampling to evaluate soil C storage. Vegetation was found to be much less important for C storage than soil, with peat soils, particularly Blanket bog, containing the greatest amounts of C. Whilst the total amount of C in vegetation was similar to the UK national C inventory's estimate for the same area, the national inventory estimate for soil C was over three times higher than the value derived in the current study. Because the UK's C inventory can be considered relatively accurate compared to many others, the results imply that current estimates for soil C storage, at national and global scales, should be treated with caution

A Reassessment of General Lighting Practice Based on the MRSE Concept

A case is made for reassessment of the purpose of general lighting practice, involving a change from lighting standards specifying illuminance for high levels of visual performance, to providing for predictable assessments of surrounding brightness. Mean room surface exitance (MRSE) is proposed as a suitable metric for this purpose. This metric actually serves a dual role, in that apart from providing practitioners with the means to design for chosen levels of surrounding brightness, it would enable regulators to specify for perceived adequacy of illumination, PAI. The adoption of PAI specified in terms of MRSE as the prime criterion for specifying indoor illumination levels in lighting standards would invoke fundamental changes in general lighting practice. These are discussed, together with limitations of the MRSE concept and the need for both further research and feedback from industry professionals

Development and Evaluation of a New Interior Lighting Design Methodology.

This thesis examines the basis of professional practice involved in providing controlled distributions of artificial lighting to provide for the broad range of human activities conducted within buildings, and makes proposals for a new methodology. Current practice for specifying lighting requirements based on task performance is examined, and shortcomings are identified. Proposals that have been advanced for alternative forms of specification are reviewed, including those initiated by the candidate in the five publications that form the major part of this thesis. In these publications, the candidate proposes a basis for general lighting practice based on how lighting may influence the appearance of indoor spaces and their contents. Lighting metrics relating to peoples’ responses to the appearance of the lit environment are introduced, and application procedures that may incorporate lighting design objectives based on task performance are discussed. It is recorded that the candidate’s publications have aroused interest among the lighting profession, as well as having stimulated research investigations, notably at DIT. The findings from these investigations are evaluated, and it is concluded that while they generally support the candidate’s proposals, more research is needed to justify their adoption for general lighting practice, particularly as adoption would involve substantial changes from current practice. Specific recommendations for ongoing research are identified, and it is noted that such research is currently in hand at DIT

Using legume-based mixtures to enhance the nitrogen use efficiency and economic viability of cropping systems - Final report (LK09106/HGCA3447)

As costs for mineral fertilisers 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 rotations helps to maximise 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. Replicated field experiments were conducted over three years at multiple locations, testing the performance of 12 legume species and 4 grass species sown in monocultures, as well as in a mixture of 10 of the legumes and all 4 grasses (called the All Species Mix, ASM). In addition, we compared this complex mixture to farmer-chosen ley mixtures on 34 sites across the UK. The trials showed that there is a large degree of functional complementarity among the legume species. No single species scored high on all evaluation criteria. In particular, the currently most frequently used species, white clover, is outscored by other legume species on a number of parameters such as early development and resistance to decomposition. Further complementarity emerged from the different responses of legume species to environmental variables, with soil pH and grazing or cutting regime being among the more important factors. For example, while large birdsfoot trefoil showed better performance on more acidic soils, the opposite was true for sainfoin, lucerne and black medic. In comparison with the monocultures, the ASM showed increased ground cover, increased above-ground biomass and reduced weed biomass. Benefits of mixing species with regard to productivity increased over time. In addition, the stability of biomass production across sites was greater in the ASM than in the legume monocultures. Within the on-farm trials, we further found that on soils low in organic matter the biomass advantage of the ASM over the Control ley was more marked than on the soils with higher organic matter content. Ecological modelling revealed that the three best multifunctional mixtures all contained black medic, lucerne and red clover. Within the long term New Farming Systems (NFS) rotational study, the use of a clover bi-crop showed improvement to soil characteristics compared to current practice (e.g. bulk density and water infiltration rate). Improvements in wheat yield were also noted with respect to the inclusion of a clover bi-crop in 2010, but there was evidence of a decline in response as the N dose was increased. Cumulatively, over both the wheat crop and the spring oilseed rape crop, the clover bi-crop improved margin over N. The highest average yield response (~9%) was associated with the ASM legume species mix cover cropping approach

A method-centric 'User Manual' for the mitigation of diffuse water pollution from agriculture

We describe the development of a manual of methods for mitigating diffuse water pollution from agriculture and its important influence on policy and practice in England and Wales. The objective of the ‘User Manual’ was to provide policy makers and those implementing policies with information about the cost, effectiveness and applicability of potential methods in a form that would be readily understood by non-specialists. The ‘User Manual’ was based on earlier reports synthesizing available research data and, where data were unavailable, used expert elicitation. The outcome generated 44 potential methods (under the broad categories of land use, soil management, livestock management, fertilizer management, manure management and farm infrastructure) and described the simultaneous impact of applying each method on losses of nitrate, phosphorus and faecal indicator organisms relative to baseline losses. Estimates of cost and effectiveness were presented at the whole-farm level for seven model farm types. Methods differed widely in their cost-effectiveness and applicability to the different model farms. Advantages and limitations of the approach are discussed and subsequent developments of the original ‘User Manual’ are described, together with the opinions of catchment officers who have used the ‘User Manual’ to implement mitigation methods on farms

How Will Removal of the Non-Organic Feed Derogation Affect Nutrient Budgets of Organic Livestock Farms in Wales?

Agri-environment schemes encourage organic farming in Wales. The National Assembly Government second organic action plan has a target of 10-15% land in organic production by 2010. Although forage based, many organic livestock farmers buy in concentrate feeds, which are important sources of nutrients to the farm. The current derogation allowing organic producers up to 10% approved non-organic feed ends in 2005. Many organic farmers are beginning to make management changes to comply with this. The aims of this study were to construct simple nutrient budgets on different organic livestock farms, investigate any planned system changes, look at impacts on nutrient budgets and create awareness amongst farmers of the value of nutrient budgeting, in addition to soil testing, for planning sustainable organic farming systems

A review of farm-scale nutrient budgets for organic farms as a tool for management of soil fertility

On organic farms, where the importation of materials to build/maintain soil fertility is restricted, it is important that a balance between inputs and outputs of nutrients is achieved to ensure both short-term productivity and long-term sustainability. This paper considers different approaches to nutrient budgeting on organic farms and evaluates the sources of bias in the measurements and/or estimates of the nutrient inputs and outputs. The paper collates 88 nutrient budgets compiled at the farm scale in 9 temperate countries. All the nitrogen (N) budgets showed an N surplus (average 83.2 kg N ha-1 year-1). The efficiency of N use, defined as outputs/inputs, was highest (0.9) and lowest (0.2) in arable and beef systems respectively. The phosphorus (P) and potassium (K) budgets showed both surpluses and deficits (average 3.6 kg P ha-1 year-1, 14.2 kg K ha-1 year-1) with horticultural systems showing large surpluses resulting from purchased manure. The estimation of N fixation and quantities of nutrients in purchased manures may introduce significant errors in nutrient budgets. Overall, the data illustrate the diversity of management systems in place on organic farms, and suggest that used together with soil analysis, nutrient budgets are a useful tool for improving the long-term sustainability of organic systems