Synnøve Rivedal

Research Station Manager

(+47) 975 85 474
synnove.rivedal@nibio.no

Place
Fureneset

Visiting address
Fure, 6967 Hellevik i fjaler

Abstract

In Norway, the effect of drainage on grassland yields has received little attention for decades. Low level of drainage may be a reason for low grassland production. Therefore, a drainage experiment was established in a western Norwegian ley, on a sandy silt soil with a high capacity for water storage. The plots had six and twelve meters drain spacing, as well as undrained. There were two or three cuts, and fertilization of 190 or 290 kg N yr-1 ha-1. Drainage intensity gave a small significant increase in yield. N loss in drainage water increased with drainage intensity. The yield increase is likely too small to justify drainage, but the intervention might still be worthwhile due to increased N efficiency and a more manageable risk of compaction. A precise quantification of the hydrological effects is hard due to inherent soil variability.

Abstract

Inclusion of clover in grasslands increases functional diversity, N yield and forage quality and has been advocated for mitigating nitrous oxide (N2O) emissions. However, boreal grass-clover leys often show poor winter survival with considerable aboveground losses of nitrogen (N) and carbon (C). Little is known about how these losses affect off-season N2O emissions. Here we report field experiments over two winters, conducted at two coastal locations in Western and Northern Norway. N2O emissions were measured in plots with 0, 30 and 100% red (T. pretense) and white clover (T. repens) in a timothy - meadow fescue mixture. Overwinter N loss from the sward was quantified by comparing N contents in roots, stubble and herbage in autumn and spring. Additional treatments were removal of above-ground biomass in autumn and soil compaction. Off-season N2O emissions correlated positively with estimated overwinter N loss from herbage, which in turn depended on the fraction of clover in the ley. Pure grass leys emitted less N2O than leys that contained clover. Corrected for background emissions from pure grass, up to 13% of the above-ground N loss was emitted as N2O–N when clover was grown in pure stand. This fraction was much smaller, however, when clover was grown in mixture with grass (1.9 ± 0.9%), suggesting reassimilation of inorganic N. Indeed, we found significant increases in root and stubble N in mixtures throughout winter. Removal of above-ground biomass in autumn appeared to reduce the sward's ability to retain N throughout winter, and hence had no or a stimulating effect on N2O emissions. Soil compaction increased off-season N2O emissions 1.3–1.6-fold. Our results show that boreal grass-clover leys can be a significant source of N2O during winter, intricately controlled by loss and reassimilation of N. This underscores the importance of off-season plant-soil management for reducing the greenhouse gas (GHG) footprint of animal production in high latitude ecosystems.

Abstract

The open landscapes produced over centuries by small-scale farming in Norwegian coastal and fjord areas are threatened by agricultural abandonment, raising public concern for maintenance of the species-rich and valuable coastal grasslands. Semi-natural grasslands, traditionally grazed in the spring and fall and mown in summer, are most affected. Two linear programming models, one for small-scale sheep and one for small-scale mixed dairy and meat farms, both described in a separate method article, were developed. In the models is studied effects on production, grazing and land utilization, of altering government financial support among leys on arable land, enclosed farm pasture, grazing animals, and altering the (regulated) prices farmers pay for concentrate feed at the farm level. Sheep grazing can be expanded by intensification through increased fertilization and purchase of concentrate feed. Raising steers instead of bulls on dairy and beef farms with a milk quota would result in more mixed grazing by both sheep and steers, which is advantageous for the landscape. Steers are currently quite rare in Norway and their numbers can be increased with more subsidies for grazing, (Grazing Support (GS)) or by increasing the Regional Environmental Support (RES), a policy instrument targeting local projects for more grazing in specific areas. The current Agriculture and Cultural Landscape (ACL) subsidy payment places a higher value on arable land compared to the more biodiverse farm pastures, resulting in weaker incentives for keeping farm pasture in production. Raising the rate for farm pasture relative to that of arable land in the ACL scheme would result in stronger incentives for keeping such farm pasture in production, and likely increase biodiversity and landscape values. Increased GS for sheep might lead to more purchase of concentrate to keep more animals through the winter and eventually needs to be counteracted with higher prices for concentrated feedstuffs.

Abstract

A future wetter climate in Northern Europe may increase soil compaction from traffic of heavy machinery. This study investigated the impact of tractor traffic on grassland yield, soil physical properties and penetration resistance in three experimental field trials in Norway; on medium sand at Tjøtta, Nordland, on silty medium sand at Fureneset, Sogn og Fjordane and on silt at Løken, Oppland. The experiments were conducted in a split-plot design with three levels of two wheel-by-wheel passes with tractor traffic after each cut: no traffic, light tractor or heavy tractor on large plots, and three different seed mixtures on small plots. The yield reduction by tractor traffic was 26% at Løken, 4% at Fureneset and 1% at Tjøtta. There was a positive correlation between soil moisture content and yield reduction by traffic. Tractor traffic reduced pore volume and air capacity and increased bulk density, compaction degree and penetration resistance with the largest effect at Løken and the smallest at Tjøtta. There were no statistically significant differences in yield or soil physical properties between light and heavy tractor. The study shows that soil texture and soil moisture content are major factors explaining traffic effects on soil physical properties and grassland yield.