Weed management in grain legumes using an intercropping approach

Grain legumes benefit the farming system via symbiotic N2 fixation and subsequent residue incorporation contributing to soil fertility together with their effect as break-crop in cereal rich rotations. However, grain legumes are weak competitors towards weeds and consequently weeds constitute a major problem. Since the European policies for reducing the negative effects of agricultural plant production on the environment point to reductions in pesticide use (Mortensen et al., 2000), there is a requirement to further develop strategies to reduce weeds. Intercropping involves the simultaneous growing of several plant species in the same field and the cropping strategy is known to involve interspecific interferences increasing the use of plant growth resources in space and time (Ofori and Stern, 1987) improving crop competitive ability towards weeds (Hauggaard-Nielsen et al., 2001). The main objectives of the present study was to determine the effects of grainlegume-cereal intercropping on the weed biomass production as compared to the respective sole crops using successive harvests in a three-year field study

Competitive ability of grain legume-barley intercrops towards volunteer crops and weeds

Field pea (Pisum sativum L.) and blue lupin (Lupinus angustifolius L.) were either sole cropped or inter-cropped with barley (Hordeum vulgare L.) at two levels of nitrogen application to determine the effects of interspecific interaction in an intercrop and nitro-gen fertility on competitive ability towards volunteer crops - exemplified by red clover (Trifolium pratense). The dynamically change of competitive ability by intercropped species over time was shown to be im-portant in order to reduce opportunities for growth of volunteer crops and weed

Why diversify annual biomass production for energy – exemplified by green house gas emissions from the Danish IBUS bioethanol production concept

There is a need for integrating the biomass starting point into the energy manufacturing steps. It will secure that bioenergy is produced with limited use of non-renewable fossil fuel to secure that in the application of biomass a net emission reduction of green house gasses take place along the whole chain. Intercropping, defined as the cultivation of two or more species simultaneously on the same area of land, is an traditional practice still widespread in the tropics and common in developed countries before the ‘fossilization’ of agriculture. This cropping strategy is based on the manipulation of plant interactions in time and space to optimize resource use and productivity. It is regarded as the practical application of basic ecological principles such as diversity, competition and facilitation (Hauggaard-Nielsen et al., 2007). Cereal-legume annual intercropping show the possibility to increase input of leguminous symbiotic nitrogen (N) fixation into cropping systems reducing the need for fertilizer N applications (Jensen, 1996). Moreover, less need for pesticides are obtained due to improved competition towards weeds (Hauggaard-Nielsen et al., 2001) and less general damages on intercropped species by pest and disease organisms (Hauggaard-Nielsen et al., 2007). Intercropping is a more adaptive management practice as compared to the present arable crop rotations consisting mainly of sole crops. Perennials like clover-grass intercrops or mixtures are obviously more diversified than traditional annual crops. Clover-grass leys are important in many agroecosystems today due to quality as feed for livestock, a high dry matter production (10 t ha-1 yr-1 unfertilized, where 95% of the N accumulation is N2 fixed by clover (Jørgensen et al., 1999) providing a nitrogen-rich residue, which may significantly reduce fertilizer requirements for the succeeding crop when mineralized (Hauggaard-Nielsen et al., 1998). Furthermore, clover-grass lays can be harvested several times a year and processed to ethanol throughout the year. It is very much questioned whether bioethanol is a sustainable energy resource that can offer environmental and long-term economic advantages over fossil fuels, like gasoline or diesel. The aim of the present presentation is to debate the substitution of fossil fuels by crop biomass requiring the right selection of plant species according not only to chemical quality for efficient conversion but also to secure the development of ecologically benign farming system including biomass for energy

Alfred Sidgwick\u27s \u27rogative\u27 approach to argumentation

Few, if any, logicians deserve the title \u27precursor of modern argumentation theory\u27 more than the largely neglected English logician, Alfred Sidgwick (1850-1943). Sidgwick developed a coherent and original theory of argumentation with a distinctly \u27mo dern\u27 flavour. This paper outlines his idea of a \u27negative\u27 view of logic, an important aspect of which is the thesis that the distinctions and inference schemata of formal logic should not be applied as criteria of the validity or invalidity of natural language arguments, but rather \u27rogatively\u27--as suggesting the kinds of objections or demands for clarification that are relevant at specific stages of a discussion

Quantification of root fungi using signature fatty acids

Both deleterious (pathogenic) and beneficial (mycorrhizal) fungi inhabit plant roots with strong impact on plant growth and health. Various methods have been used to quantify these fungi, such as indirect measurements of plant parameters, disease index, staining techniques and serological/genetic/biochemical markers. The objective of this work is to evaluate the possibility of using signature fatty acids to quantify root-inhabiting fungi in planta and in soil. Different fatty acid-based methods can be used to quantify fungi. Phospholid fatty acids (PLFA) can be used for biomass estimation and neutral lipid fatty acids (NLFA) for estimation of fungal energy reserves and the NLFA/PLFA ratio can give information on the physiological status of the fungus. It is quite laborious to make PLFA and NLFA analyses; so whole cell fatty acid (WCFA) analyses, which are much faster, can be used as a faster alternative to give information of root infection intensity. Signature fatty acids have been used to quantify arbuscular mycorrhizal fungi (16:1ω5) and the pea root pathogen Aphanomyces euteiches (14:1ω9). Recently, we have further used arachadonic acid (20:4) to estimate root infection intensity of the plasmodiophorids Plasmodiophora brassica, causing club root in cabbage and Spongospora subterranea, the vector of mop top potato virus. Specificity of the various signature fatty acids of root-inhabiting fungi are discussed in relation to quantifying these fungi in both controlled greenhouse pot experiments and in the field. Furthermore, the possibility of using signature fatty acids to estimate soil inoculum potential of root-inhabiting fungi are discussed

Biomass production, symbiotic nitrogen fixation and inorganic N use in dual and tri-component annual intercrops

The interspecific complementary and competitive interactions between pea (Pisum sativum L.), barley (Hordeum vulgare L.) and oilseed rape (Brassica napus L.), grown as dual and tri-component intercrops were assessed in a field study in Denmark. Total biomass production and N use at two levels of N fertilisation (0.5 and 4.0 g N/m2), were measured at five harvests throughout a growing season. All intercrops displayed land equivalent ratio values close to or exceeding unity, indicating complementary use of growth resources. Whereas both rape and barley responded positively to increased N fertilisation, irrespective of whether they were grown as sole- or intercrops, pea was strongly suppressed when grown in intercrop. Of the three crops barley was the strongest competitor for both soil and fertiliser N, rape intermediate and pea the weakest. Faster initial growth of barley than pea and rape gave barley an initial competitive advantage, an advantage that in the two dual intercrops was strengthened by the addition of N. Apparently the competitive superiority of barley was less strong in the tri-component intercrop, indicating that the impact of the dominantmay, through improved growth of both rape and pea, have been diminished through indirect facilitation. Interspecific competition had a promoting effect on the percent of nitrogen derived from N2 fixation of pea, and most so at the low N fertilisation level. Results indicate that the benefits achieved from the association of a legume and nonlegume, in terms of N2 fixed were greatest when pea was grown in association with rape as opposed to barley which could indicate that the benefits achieved from the association of a legume and nonlegume are partly lost if the nonlegume is too strong a competitor