Browsing by Subject "N2 fixation"

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The effects of leguminous living mulch intercropping and its growth management on organic cabbage yield and biological nitrogen fixation
(2022) Stein, Sophie; Hartung, Jens; Möller, Kurt; Zikeli, Sabine
In organic horticulture, living mulches (LM) are used for weed suppression and erosion prevention. In addition, leguminous LM can contribute to higher nitrogen (N) import into vegetable cultivation systems via biological N2 fixation (BNF). In order to investigate the effect of LM systems, a two- as well as three-year field experiment was conducted between 2019 and 2021 at two locations in Southwest Germany. White cabbage was intercropped with two different clover varieties (Trifolium repens cv. ‘Rivendel’, with regular growth and T. repens cv. ‘Pipolina’, a micro clover) and perennial ryegrass (Lolium perenne cv. ‘Premium’). Bare soil (with spontaneous vegetation) without intercropping was the control treatment. The second factor was the growth management of the LM: incorporation by rototilling before planting the cabbage, intercropping with the cabbage and no LM growth management, and intercropping with mulching of the LM during the cabbage growing. The results show that rototilling LM before planting the cabbage did not lead to higher weight of cabbage residues or differences in total head yield among the treatments for growth management. Intercropping without further LM growth management did not result in a reduced total head yield of cabbage compared to mulching. The micro clover ‘Pipolina’ showed no reduced competition with cabbage compared to the regular-growing white clover ‘Rivendel’. Therefore, we conclude that leguminous LM systems, regardless of growth management, can achieve high yields with sufficient irrigation and additional fertilization while increasing the inputs of N via BNF into the entire cropping system.
The Influence of nitrogen applications and low rainfall conditions on yield of mixed grass-legume grassland for 2 years
(2023) Weggler, Karin; Elsäßer, Martin
Mixed-species grassland containing legumes were suggested to increase yield compared to monocultures. Furthermore, some legumes were suggested to be able to sustain growth, even under drought conditions. The first aim of the current study was to measure if multispecies grassland with legumes is also more productive when their N input due to symbiotic N2 fixation is taken into account. Our second aim was to determine the benefit of grass–legume mixtures in terms of dry matter production under naturally occurring drought conditions. Mixed-species grasslands, consisting of monocultures and variable mixtures of (a) Trifolium pratense, (b) Trifolium. repens, (c) Lolium perenne, and (d) a mixture of drought-tolerant grasses (GSWT based), were assessed for their dry matter production over two years with contrasting weather patterns. The legume–grass seeding mixtures received either a fixed (180 kg N ha−1) or adapted N-fertilizer application (0–180 kg N ha−1), with the latter taking the assumed symbiotic N2 fixation by legumes into account. Mixed-species grassland showed improved yield compared to monocultures both in comparably humid and drought-affected years. The benefits of multispecies grass–legume mixtures were considerably more obvious under a fixed but still measurable under an adapted N-fertilizer regime. The species diversity effect appears to be significantly dependent on the additional N supply enabled by legumes’ symbiotic N2-fixation. Legumes and drought-tolerant grasses yielded equally well under drought conditions, although legumes showed major advantages during moderate drought and humid conditions. White and red clover, although both legumes, differed significantly in their persistence under elevated-N and their dry matter production under low-N fertilizer application, but were equal in their tolerance towards drought.