Optimisation of phosphorus and potassium management within organic farming systems (OF0114)

This is the final report from Defra project OF0114. The scientific objectives of the project were to 1 - Assess the balance between inputs and offtakes of P and K within a range of UK organic farming systems 2 - Evaluate chemical and bioavailability indices used to assess P and K status of soils 3 - Assess the availability of a range of P and K fertilisers to grass-clover leys and tillage crops 4 – Develop a process-based simulation model and integrate with whole farm nutrient budgeting to allow P and K management decisions to be made for the whole farm. 5 - Provide guidelines for farmers on the use of phosphorus and potassium fertilisers for organic systems. Farm gate budgets for P and K were collated using farm records, measurements and standard tables of nutrient contents for a number of organic farms and rotations on organic farms. An integrated series of incubation, greenhouse and field experiments was carried out with a range of fertilising materials selected to give a range of likely availabilities for plant uptake and to give a mix of mineral and organic sources of P and K on soils representing the range of soil types under organic management. Organic farming systems can show both P and K surpluses and deficits depending on management. In mixed systems, manures represent a significant resource of both P and K, which are supplemented through imports of feed and bedding. However, manure handling also therefore gives significant opportunity for losses, particularly of K from the system. K deficits are common in organic rotations, but not necessarily at the whole farm level. These deficits are close to the level which can be sustained from the weathering of mineral reserves in many UK soils. However, more consideration needs to be taken of the potential of soils to supply K when rotations and management plans are designed. There is no reason why organic farming systems, operating within the current UKROFS standards, cannot achieve a nutrient budget in line with long-term sustainability of soil P and K. However, continued monitoring of soil P and K levels in long-term organic trials is necessary to demonstrate these conclusions. Results of the simulation modelling are further summarised in the executive summary at the start of the main report. The complex interactions between nutrient cycles in organic farming systems means that the process based simulation model of P and K turnover was necessarily very simplified and the data collected in this project was not long-term enough to allow a full evaluation of all the factors, which influence P and K offtake, particularly the impact of crop establishment and management practices influencing spatial and temporal P nd K management. However, practical guidelines were drawn up for farmers and their advisors. The project has produced 4 scientific papers and contributed to others. 10 presentations were made at scientific conferences and 5 presentations to farmers’ meetings. The project has also been responsible for simulating debate and encouraging the use of good scientific data in the development of future UK organic farming systems

Impacts of farming practice within organic farming systems on below-ground ecology and ecosystem function

Maintaining ecosystem function is a key issue for sustainable farming systems which contribute broadly to global ecosystem health. A focus simply on the diversity of belowground organisms is not sufficient and there is a need to consider the contribution of below-ground biological processes to the maintenance and enhancement of soil function and ecosystem services. A critical literature review on the impacts of land management practices on below-ground ecology and function shows that farm management practices can have a major impact. A particular challenge for organic farming systems is to explore to what extent reduced tillage can be adopted to the benefit of below-ground ecology without critically upsetting the whole farm management balance

Utilising the concept of nutrients as a currency within organic farming system

This report was presented at the UK Organic Research 2002 Conference.Within organic systems, the successful management of nutrients at the field level is crucial for maximising production and minimising the environmental impacts. This requires that the farmer makes the best possible use of nutrients excreted by the grazing or housed livestock. In addition, the farmer must successfully manage the nutrients built-up in the ley phase of the crop rotation over the whole of the arable phase period. To analyse these complex flows, a nutrient budget model has been developed that describes the spatial and temporal flows within the organic farming system. The concept is analogous to treating nutrients as a currency where the flow of nutrients represents a cashflow. A spatial nutrient budget permits the analyses of the performance of the nutrient flows to be examined for the housing, manure, livestock, rotational land and permanent pasture to be analysed separately. This analysis will allow the farmer to better understand the weaknesses in the system, and hence take preventative measures

Indicator systems - resource use in organic systems

A balanced use of resources within organic farming systems is required to maintain sustainable systems. Hence, it is essential to have tools that can assess the use of resources within the farming system and their impact on the environment. The range of tools that have been developed include those assessing local farm-scale issues together with those that assess impacts at the global scale. At the global scale assessments are usually made on the basis of a unit of product whereas at the local scale assessments can also be made on an area basis. In addition, the tools also assess a variety of issues, e.g. biodiversity, pollution potential, energy and water use. The level of detail required for the different assessment tools differs substantially; nevertheless it is essential that the indicator systems developed are based on sound knowledge, are acceptable to the farmers and can guide their future actions

Improving supply and phosphorous use efficiency in organic farming systems

Phosphorus (P) is an essential plant nutrient that needs to be managed carefully in organic systems so that crop yield and quality remain sustainable without contributing to environmental damage, particularly that associated with eutrophication. Under organic regulations, minimally processed rock phosphate (PR) can be used to amend low P fertility soils, although the solubility is extremely low at optimum soil pH for most crop growth (pH 6.5). This paper describes a project (PLINK) which aims to develop methods of improving P efficiency on organic farms, although the same approaches may also be applicable on conventional and low-input farms. The methodologies that the project is developing include the fermentation and composting of crop waste material with PR in order to solubilise P and make it more available to the crop. Some initial results are described here. In addition, the project will investigate the alteration of the rotation to include crops or varieties with high P uptake efficiency, or roots that possess acidifying properties which improve P availability for following crops

A Study of Compact Radio Sources in Nearby Face-on Spiral Galaxies. II. Multiwavelength Analyses of Sources in M51

We report the analysis of deep radio observations of the interacting galaxy system M51 from the Very Large Array, with the goal of understanding the nature of the population of compact radio sources in nearby spiral galaxies. We detect 107 compact radio sources, 64% of which have optical counterparts in a deep H$\alpha$ Hubble Space Telescope image. Thirteen of the radio sources have X-ray counterparts from a {\em Chandra} observation of M51. We find that six of the associated H$\alpha$ sources are young supernova remnants with resolved shells. Most of the SNRs exhibit steep radio continuum spectral indices onsistent with synchrotron emission. We detect emission from the Type Ic SN 1994I nearly a decade after explosion: the emission ($160\pm22 \mu$Jy beam$^{-1}$ at 20 cm, $46\pm11 \mu$Jy beam$^{-1}$ at 6cm, $\alpha=-1.02\pm0.28$) is consistent with light curve models for Type Ib/Ic supernovae. We detect X-ray emission from the supernova, however no optical counterpart is present. We report on the analysis of the Seyfert 2 nucleus in this galaxy, including the evidence for bipolar outflows from the central black hole.Comment: 22 pages, 8 figures (5 color) in separate files, AASTeX. Full resolution figures and preprint may be obtained by contacting [email protected]. AJ accepte

Both Myoblast Lineage and Innervation Determine Fiber Type and Are Required for Expression of the Slow Myosin Heavy Chain 2 Gene

AbstractSkeletal muscle fibers express members of the myosin heavy chain (MyHC) gene family in a fiber-type-specific manner. In avian skeletal muscle it is the expression of the slow MyHC isoforms that most clearly distinguishes slow- from fast-contracting fiber types. Two hypotheses have been proposed to explain fiber-type-specific expression of distinct MyHC genes during development—an intrinsic mechanism based on the formation of different myogenic lineage(s) and an extrinsic, innervation-dependent mechanism. We developed a cell culture model system in which both mechanisms were evaluated during fetal muscle development. Myoblasts isolated from prospective fast (pectoralis major) or slow (medial adductor) fetal chick muscles formed muscle fibers in cell culture, none of which expressed slow MyHC genes. By contrast, when muscle fibers formed from myoblasts derived from the slow muscle were cocultured with neural tube, the muscle fibers expressed a slow MyHC gene, while muscle fibers formed from myoblasts of fast muscle origin continued to express only fast MyHC. Motor endplates formed on the fibers derived from myoblasts of both fast and slow muscle origin in cocultures, and slow MyHC gene expression did not occur when neuromuscular transmission or depolarization was blocked. We have cloned the slow MyHC gene that is expressed in response to innervation and identified it as the slow MyHC 2 gene, the predominant adult slow isoform. cDNAs encoding portions of the three slow myosin heavy chain genes (MyHC1, slow MyHC 2, and slow MyHC 3) were isolated. Only slow MyHC 2 mRNA was demonstrated to be abundant in the cocultures of neural tube and muscle fibers derived from myoblasts of slow muscle origin. Thus, expression of the slow MyHC 2 gene in thisin vitrosystem indicates that formation of slow muscle fiber types is dependent on both myoblast lineage (intrinsic mechanisms) and innervation (extrinsic mechanisms), and suggests neither mechanism alone is sufficient to explain formation of muscle fibers of different types during fetal development