Temperate Forage Grass-Legume Mixtures: Advances And Perspectives

The paper summarises some of the advances which have been made a) in increasing understanding of the grass-legume association, especially grass-white clover, so that the association can be more predictably exploited and b) in overcoming limitations in the use of such mixtures. The contribution which forage legumes make to the N economy of mixtures is reviewed with estimates approaching 400 kg N ha-1 for some. Uptake by grass of legume- derived N (N transfer) reduces soil mineral N levels and increases the proportion of fixed N in the total legume N relative to legume monoculture. Although N transfer also causes inconsistent contribution of legume to mixed swards, models of the effect of legume derived N on the interaction between grass and legume are helping to predict likely grass-legume balance, even when grazed. The higher nutritive value and intake of legumes relative to grass is due to a range of factors including faster rate of particle breakdown, faster digestion in the rumen, more non- ammonium N reaching the small intestine and higher efficiency of energy utilization although efficiency of N utilization is lower. Poor utilization is not an issue with birdsfoot trefoil and sainfoin due to their herbage having a high content of condensed tannins which protect protein from degradation in the rumen. Breeding programmes using conventional and biotechnological methods are aiming to improve nutritive value such as increasing protein quality and introducing condensed tannins into clovers and lucerne. Breeding of legumes to reduce antiquality factors, such as bloat, is underway. Breeding to reduce oestrogenic effects has been successful in red clover and subclover. Advances are leading to improved legume consistency in mixture including improvement in tolerance to biotic and environmental stress by breeding and increased understanding of the role of companion grasses. Research which underpins management techniques to improve predictability of grass-legume balance is also discussed, including the positive and negative role of the grazing animal. The potential and limitations of grass-legume swards to reduce N loss, including NO3 leaching, in whole farm systems is evaluated where grass/white clover can reduce leaching by 50% compared with a high fertilizer N system at only 20% reduction in output. Other factors which may result in increased reliance on forage legumes, in addition to the improvements in forage legumes resulting from research, include de-intensification policy decisions to reduce stocking rates, increased uptake of organic farming, increased cost of N fertilizer relative to commodity prices. Shared research effort between countries is advocated to supply adequate resources to solve some of the remaining problems in grass/legume associations and effective technology transfer should include development of decision support systems due to the complexity of the association

Grass Growth Modelling: to Increase Understanding and Aid Decision Making On-Farm

Key points Crop and grass growth models have been developed over the last 50 years, or so, but general appreciation of their benefits and potential has been recognised only relatively recently. The most popular application of grass growth models has traditionally been for knowledge understanding. There is growing awareness of the potential of models in decision support systems (DSS) applications to aid pasture management and grassland budgeting on dairy farms. Although some models have been developed for DSS, their widespread uptake in industry has been slow; challenges still exist which need to be addressed in order to improve their precision and user-friendliness

GrassCheck: Monitoring and Predicting Grass Production in Northern Ireland

Grass budgeting is a key management practice on dairy farms to balance grass supply on paddocks with grass demand by the grazing herd. Grass budgets must be pre-emptive to be effective. The uncertainty of grass production and the difficulty in quantifying both current and forecasted rates of growth hamper effective budgeting and paddock management. Grass growth rates are highly variable both in time and space. Therefore, they vary greatly between locations at any given time and also across the season at any given location. Figure 1 shows the pattern of growth rates recorded at the Agricultural Research Institute of Northern Ireland (ARINI) in the two seasons before this project. The GrassCheck project was established in Northern Ireland to quantify current rates of grass growth and grass quality and to predict growth rates for up to 2 weeks in advance. The project will run from 2004 until 2006. This paper outlines the project and reports on its findings after one year

Manipulation of Grass Supply to Meet Feed Demand

End of Project ReportGrazed grass is generally the cheapest form of feed available for beef and milk production in Ireland. Grass growth is variable during the year with a peak in May/June and a secondary peak in August. There is little net growth from December to February. Grass growth is also variable across the country with higher grass growth in the south and south-west (14 to 15 t DM/ha/year) compared with approximately 11 t DM/ha/year in the north-east (Brereton, 1995). There is poor synchrony between grass supply and feed demand on beef and dairy farms. The feed demand curve for a calf to two year old beef system shows feed demand decreasing as grass supply increases, and grass supply decreasing as feed demand increases. Similarly, the feed demand curve of a spring calving dairy herd shows poor synchrony with grass supply, with a surplus of grass from about mid-April to mid-August, and a deficit for the rest of the year. Traditionally surplus grass produced during May and June is conserved as silage or hay and fed back to cattle and dairy cows during the deficit times of the year. This project examined the possibility of reducing the grass growth peak in May/June and increasing grass supply later in the year by altering nitrogen application pattern and extending autumn rotation lengths

SCUBA - A submillimetre camera operating on the James Clerk Maxwell Telescope

The Submillimetre Common-User Bolometer Array (SCUBA) is one of a new generation of cameras designed to operate in the submillimetre waveband. The instrument has a wide wavelength range covering all the atmospheric transmission windows between 300 and 2000 microns. In the heart of the instrument are two arrays of bolometers optimised for the short (350/450 microns) and long (750/850 microns) wavelength ends of the submillimetre spectrum. The two arrays can be used simultaneously, giving a unique dual-wavelength capability, and have a 2.3 arc-minute field of view on the sky. Background-limited performance is achieved by cooling the arrays to below 100 mK. SCUBA has now been in active service for over a year, and has already made substantial breakthroughs in many areas of astronomy. In this paper we present an overview of the performance of SCUBA during the commissioning phase on the James Clerk Maxwell Telescope (JCMT).Comment: 14 pages, 13 figures (1 JPEG), Proc SPIE vol 335

Oxidative Addition of Aryl Electrophiles to a Prototypical Nickel(0) Complex: Mechanism and Structure/Reactivity Relationships

Detailed kinetic studies of the reaction of a model Ni-0 complex with a range of aryl electrophiles have been conducted. The reactions proceed via a fast ligand exchange pre-equilibrium, followed by oxidative addition to produce either [(NiX)-X-I(dppf)] (and biaryl) or [Ni-II(Ar)X(dppf)]; the ortho substituent of the aryl halide determines selectivity between these possibilities. A reactivity scale is presented in which a range of substrates is quantitatively ranked in order of the rate at which they undergo oxidative addition. The rate of oxidative addition is loosely correlated to conversion in prototypical cross-coupling reactions. Substrates that lead to Ni-I products in kinetic experiments conditions. produce more homocoupling products under catalytic conditions

The Effect of Sward Height and Bulk Density on Herbage Intake and Grazing Behaviour of Dairy Cows

The effects of sward height and bulk density on herbage intake and grazing behaviour of dairy cows during 1 hour grazing periods was investigated. Sward factors had a marked effect on dry matter (DM) intake/bite, which ranged from 0.4 to 1.1 g, and this was reflected in hourly intake rates. Intake/bite was largely influenced by sward height, reflecting increased bite depth in taller swards, with inherent differences between swards at low sward heights largely attributable to differences in bulk density (BD). The results indicate that DM intake rates up to 4.0 kg DM/hour can be achieved in short term grazing studies with dairy cows grazing tall (180 mm+), dense (3.0 kg DM/m3), leafy perennial ryegrass swards

On a Modification of the Boundary State Formalism in Off-shell String Theory

We examine the application of boundary states in computing amplitudes in off-shell open string theory. We find a straightforward generalization of boundary state which produces the correct matrix elements with on-shell closed string states.Comment: Latex, 10 pages, refs added, minor typos correcte

Modelling Winter Grass Growth and Senescence

In temperate climates, because net grass growth in winter is low, most grass growth models deal with the main growing season (Mar-Oct in the N Hemisphere), with little emphasis on grass growth in winter (Nov-Feb). However, grass tissue turns over continuously (Hennessy et al., 2004) and the fate of herbage entering the winter is important in extended grazing season systems. This study aimed to model winter grass growth for the period 15 Oct 2001 to 28 Jan 2002 for a range of autumn closing dates (1 Sep, 20 Sep and 10 Oct) by modifying an existing model, so that the amount of green leaf could be predicted at intervals over the winter