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

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

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