Current challenges to global food security require sustainable intensification of agriculture through initiatives that include more efficient use of nitrogen (N), increased protein self‐sufficiency through homegrown crops, and reduced N losses to the environment. Such challenges were addressed in a continental‐scale field experiment conducted over 3 years, in which the amount of total nitrogen yield (Ntot) and the gain of N yield in mixtures as compared to grass monocultures (Ngainmix) was quantified from four‐species grass–legume stands with greatly varying legume proportions. Stands consisted of monocultures and mixtures of two N2‐fixing legumes and two nonfixing grasses. The amount of Ntot of mixtures was significantly greater (P ≤ 0.05) than that of grass monocultures at the majority of evaluated sites in all 3 years. Ntot and thus Ngainmix increased with increasing legume proportion up to one‐third of legumes. With higher legume percentages, Ntot and Ngainmix did not continue to increase. Thus, across sites and years, mixtures with one‐third proportion of legumes attained ~95% of the maximum Ntot acquired by any stand and had 57% higher Ntot than grass monocultures. Realized legume proportion in stands and the relative N gain in mixture (Ngainmix/Ntot in mixture) were most severely impaired by minimum site temperature (R = 0.70, P = 0.003 for legume proportion; R = 0.64, P = 0.010 for Ngainmix/Ntot in mixture). Nevertheless, the relative N gain in mixture was not correlated to site productivity (P = 0.500), suggesting that, within climatic restrictions, balanced grass–legume mixtures can benefit from comparable relative gains in N yield across largely differing productivity levels. We conclude that the use of grass–legume mixtures can substantially contribute to resource‐efficient agricultural grassland systems over a wide range of productivity levels, implying important savings in N fertilizers and thus greenhouse gas emissions and a considerable potential for climate change mitigation.

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 (N inorg ) and root growth of winterand spring wheat to 2.5 m depth during 3 years. The roots of the winter and spring wheat penetrated the soil at a similar rate (1.3 mm o C day −1 ) and by virtue of its longer growing period, winter wheat reached depths of 2.2 m, twice that of spring wheat (1.1 m). The deeper rooting of winter wheat was related to much lower amounts of N inorg left in the 1 to 2.5 m layer after winter wheat (81 kg N inorg 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 due to its deep rooting, winter wheat may not lead to as 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.

No abstract

No abstract

The concept of sustainable intensification has recently been developed to raise productivity (as distinct from increasing volume of production) while reducing environmental impacts. This means increasing yields per unit of inputs (including nutrients, water, energy capital and land) as well as per unit of undesirable outputs (such as greenhouse gas emissions, water pollution or loss of biodiversity). It is thus helpful to understand ‘intensification’ as referring to ‘environmental factor productivity’ or ‘eco‐efficiency’. Worldwide, grassland is the most important agroecosystem delivering ecosystem services ranging from feed supply for ruminants and soil carbon storage to habitats of biodiversity. However, worldwide, grassland is under threat due to intensified land use and land‐use changes from grass to arable. In this article, we (i) highlight ecosystem services of selected grassland biomes abroad of Europe, (ii) show evidence of sustainable as well as non‐sustainable intensification options in these grassland biomes linked to European agriculture by exports of agricultural commodities (e.g. soy) and (iii) derive research strategies for north‐west European grassland research and management to match sustainable intensification strategies for the grassland‐based dairy industry.