Winter wheat roots grow twice as deep as spring wheat roots, is this important for N uptake and N leaching losses?

Cropping systems comprising winter catch crops followed by spring wheat could reduce N leaching risks compared to traditional winter wheat systems in humid climates. We studied the soil mineral N (Ninorg) and root growth of winter- and spring wheat to 2.5 m depth during three years. Root depth of winter wheat (2.2 m) was twice that of spring wheat, and this was related to much lower amounts of Ninorg in the 1 to 2.5 m layer after winter wheat (81 kg Ninorg ha-1 less). When growing winter catch crops before spring wheat, N content in the 1 to 2.5 m layer after spring wheat was not different from that after winter wheat. The results suggest that by virtue of its deep rooting, winter wheat may not lead to high levels of leaching as it is often assumed in humid climates. Deep soil and root measurements (below 1 m) in this experiment were essential to answer the questions we posed

Defoliation and Soil Compaction Jointly Drive Large-Herbivore Grazing Effects on Plants and Soil Arthropods on Clay Soil

In addition to the well-studied impacts of defecation and defoliation, large herbivores also affect plant and arthropod communities through trampling, and the associated soil compaction. Soil compaction can be expected to be particularly important on wet, fine-textured soils. Therefore, we established a full factorial experiment of defoliation (monthly mowing) and soil compaction (using a rammer, annually) on a clay-rich salt marsh at the Dutch coast, aiming to disentangle the importance of these two factors. Additionally, we compared the effects on soil physical properties, plants, and arthropods to those at a nearby cattle-grazed marsh under dry and under waterlogged conditions. Soil physical conditions of the compacted plots were similar to the conditions at cattle-grazed plots, showing decreased soil aeration and increased waterlogging. Soil salinity was doubled by defoliation and quadrupled by combined defoliation and compaction. Cover of the dominant tall grass Elytrigia atherica was decreased by 80% in the defoliated plots, but cover of halophytes only increased under combined defoliation and compaction. Effects on soil micro-arthropods were most severe under waterlogging, showing a fourfold decrease in abundance and a smaller mean body size under compaction. Although the combined treatment of defoliation and trampling indeed proved most similar to the grazed marsh, large discrepancies remained for both plant and soil fauna communities, presumably because of colonization time lags. We conclude that soil compaction and defoliation differently affect plant and arthropod communities in grazed ecosystems, and that the magnitude of their effects depends on herbivore density, productivity, and soil physical properties

Yield, nitrogen recovery efficiency and quality of vegetables grown with organic waste-derived fertilisers

More sustainable production of high-quality, nutritious food is of worldwide interest. Increasing nutrient recycling into food systems is a step in this direction. The objective of the present study was to determine nitrogen (N) fertiliser effects of four waste-derived and organic materials in a cropping sequence of broccoli, potato and lettuce grown at two latitudes (58° and 67° N) in Norway during three years. Effects of anaerobically digested food waste (AD), shrimp shell (SS), algae meal (AM) and sheep manure (SM) at different N application rates (80 and 170 kg N ha–1 for broccoli, and 80 and 60 kg N ha–1 for potato and lettuce, respectively) and residual effects were tested on crop yield, N uptake, N recovery efficiency (NRE), N balance, N content in produce, mineral N in soil, product quality parameters and content of nitrate in lettuce. Mineral fertiliser (MF) served as control. Effects on yield, N uptake, NRE, N balance and product quality parameters could to a great extent be explained by estimated potentially plant-available N, which ranked in the order of AD>SS>SM>AM. Results for crops fertilised with AD and SS were not significantly different from MF at the same N application rate, while AM, in agreement with its negative effect on N mineralisation, gave negative or near-neutral effects compared to the control. No residual effect was detected after the year of application. The results showed that knowledge about N dynamics of relevant organic waste-derived fertilisers is necessary to decide on the timing and rate of application.acceptedVersio