Initial soil structural development under different types of vegetation

In September 2007, undisturbed soil cores were taken from experimental fields in The Netherlands and in Northern Sweden that had been under different types of vegetation during four years. From these cores, thin sections were prepared to study the initial soil structural development, changes in organic matter distribution and soil biological activity in relation to plant species growing on the plots. In the Swedish samples, differences between plots with Poa pratensis and Phleum pratense were striking. The Poa plot showed more filled biological burrows, more rounded soil aggregates and also the amount of fine disperse organic matter seemed higher, whereas under Phleum the individual mineral grains more often showed a thin coating of very fine organic matter. Plots with Trifolium repens showed a slightly less pronounced development when compared to the Poa plots. The plots of Trifolium pratense plots and the mixed plot showed highest amounts of biological activity and soil structural development. The samples taken from the clay soils from The Netherlands showed similar biological activity under pure Lolium perenne and binary mixtures of L. perenne with the legumes T. repens, T. pratense and Medicago sativa from a trial that was not fertilized with N. A high activity of Lumbricus festi was shown by common excremental pellets in channels. In contrast, under Achillea millefolium in an adjacent N fertilised experiment, this activity was completely absent

Fatty Acids, α-Tocopherol, β-Carotene and Lutein Contents in Forage Legumes, Forbs, and a Grass-Clover Mixture

Fresh forages are an important natural source of vitamins and fatty acids in ruminant diets, and their concentrations in forage species are important for the quality of animal-derived foods such as dairy and meat products. The aims of this study were to obtain novel information on vitamins and fatty acids (FA) in a variety of forage legumes and non-legume forb species compared to a grass−clover mixture and to explore implications for animal-derived products. Seven dicotyledons [four forbs (salad burnet (Sanguisorba minor), caraway (Carum carvi), chicory (Cichorium intybus), and ribwort plantain (Plantago lanceolata)) and three legume species (yellow sweet clover (Melilotus officinalis), lucerne (Medicago sativa), and birdsfoot trefoil (Lotus corniculatus))] and a perennial ryegrass−white clover mixture were investigated in a cutting trial with four harvests (May−October) during 2009 and 2010. The experimental design was a randomized complete block, and analyses of variance were performed. In addition, three other forbs were grown: borage (Borago officinalis), viper’s bugloss (Echium vulgare), and chervil (Anthriscus cerefolium). Lucerne and yellow sweet clover had the lowest α-tocopherol concentrations (21−23 mg kg−1 DM) and salad burnet and ribwort plantain the highest (77−85 mg kg−1 DM); β-carotene concentrations were lowest in lucerne, salad burnet, and yellow sweet clover (26−33 mg kg−1 DM) and highest in caraway, birdsfoot trefoil, and ribwort plantain (56−61 mg kg−1 DM). Total FA concentrations were lowest in lucerne, ribwort plantain, chicory, and yellow sweet clover (15.9−19.3 g kg−1 DM) and highest in caraway and birdsfoot trefoil (15.9−19.3 g kg−1 DM). Birdsfoot trefoil had the highest (53.6 g 100 g−1 FA) and caraway and lucerne the lowest (33.7−35.7 g 100 g−1 FA) proportions of n-3 FA. This study demonstrated higher vitamin concentrations in some forbs compared with major forages such as lucerne and grass−clover, more total FA in salad burnet, caraway, and birdsfoot trefoil than in lucerne, and higher n-3 FA concentrations in all forbs than in lucerne. Opportunities are discussed to develop novel biodiverse pastures for particular product quality characteristics

Seasonality of Growth in Grass-Clover Swards Under Repetitive Nitrogen Application

The cohabitation of grass and clover is possibly due to asynchrony in their growth patterns, and to the beneficial effects of fixed nitrogen (N) on grass. Incompatibility of clover persistence with N fertilisation has been frequently reported (Nassiri and Elgersma, 2002). However, limited information is available regarding the effect of repetitive application of N in mixed swards. This research aims to study the balance between species in response to application of increasing rates of N throughout the growing season

Modelling the Effect of a Variable Light Extinction Coefficient and Leaf Dispersion on Light Partitioning Between Species in a Grass-Clover Mixture

Light partitioning in a grass-clover mixture was studied using a general competition model. The model assumes a fixed extinction coefficient (k) and no leaf dispersion. This was compared with modelling the effect of different k of both species over height as well as the effect of type of leaf dispersion. These new assumptions led to a better estimation of the light partitioning between both species. For grass the effect of variable k and leaf dispersion was similar and in both cases the total absorbed light was lower than under default conditions. For clover the new assumptions led to a higher absorbed radiation than in the original model. However, in this case the effect of leaf dispersion was more important

Comparison of methods for determining the fatty acid composition of photosynthetic tissues

The fatty acid (FA) composition of photosynthetic tissue differs from that in other plant or animal tissues. In leaves, the lipid fraction constitutes less than 10% of the dry weight and is mostly located in the chloroplasts. An extraction solvent should dissolve polar lipids readily, but should also overcome interactions between the lipids and the tissue matrix. A mixture of chloroform/methanol (C/M) is commonly used. However, less toxic alternative methods such as hexane/isopropanol (H/I) and ethanol (E) have been suggested. In this preliminary study we compared the effectiveness of these three methods which are used as standard extraction protocols for FA analysis of plant material at three different European Universities. C/M extraction gave the highest total FA content and H/I the lowest, suggesting that C/M is indeed the best general-purpose lipid extraction solvent. Significant differences were also observed for FA composition including the ratio of saturated to unsaturated FA indicating selectivity of the various solvents in extracting different individual FA. Further and more detailed investigations are required to confirm this hypothesi