Greenhouse gas emissions from soils under organic management

This report was presented at the UK Organic Research 2002 Conference. Land emissions of N2O, CO2 and NH3 have been subject to little study under organic systems, yet form important aspects of sustainability of such systems. We describe innovative methods developed at SAC to assess trace gas emission using both automatic closed chamber systems (intensive, short term monitoring) and manually-operated closed chamber systems (occasional, long term monitoring). Long-term data were collected from organic ley-arable rotation trials in North-east of Scotland. Short term data were collected to show the effect of timing and depth of ploughing-out of the ley phase on gas emissions. Ploughing gave a shortterm stimulation of CO2 and, more markedly, of N2O emission. Emissions of N2O from organic grass-clover leys were considerably lower than from conventional grass. However, some N2O emissions from organic arable are higher than from conventional systems, particularly in the first year after ploughing out ley. Ammonia emissions after spreading manure on grass were significant in the summer, though only short-lived

Recovery of the m-function from spectral data for generalized Sturm–Liouville problems

AbstractThe Sturm–Liouville problem −y″+qy=λy, y(0)cosα=y′(0)sinα, (y′/y)(1)=h(λ)/g(λ) is studied, where h and g are real polynomials. Generalized norming constants ρnk associated with eigenvalues Λn are defined and formulae are given for recovering the m-function from these constants. This leads to a uniqueness theorem for the associated inverse problem

q-Newton binomial: from Euler to Gauss

A counter-intuitive result of Gauss (formulae (1.6), (1.7) below) is made less mysterious by virtue of being generalized through the introduction of an additional parameter

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