Advantages of grass-legume mixture for improvement of crop growth and reducing potential nitrogen loss in a boreal climate

Honghong Li,Petri Penttinen,Kristina Lindström,Hannu Mikkola

doi:10.23986/afsci.75600

Abstract

A three-year field experiment was established to assess intercropping for sustainable forage production in Finland. In split-plot design, fertilizer treatment with unfertilized control, organic fertilizer, and synthetic fertilizer was the main plot factor, and crop treatment with fallow, red clover (Trifolium pratense), timothy (Phleum pratense), and a mixture of red clover and timothy was the sub-plot factor. Dry matter, carbon and nitrogen yields in mixture plots were highest with relatively high N% and the optimum C:N ratio (p < 0.05). Fertilization increased annual yields of mixture and timothy but not that of red clover. Soil NO3-N changed over time (p < 0.05) and was highest in fallow, followed by red clover, mixture, and timothy (p < 0.05), and the decrease during late growing season was smaller in the mixture and timothy plots. At the end of the experiment, soil C/NO3-N ratio was higher in timothy and mixture while lower in red clover and fallow plots (p < 0.05), and the relationship between soil DNA and NO3-N content may indicate that the potential nitrogen loss was lower in mixture and timothy than that in fallow and red clover plots.

Highlights

Agriculture is the world’s single largest driver of global environmental change (Rockström et al 2017)
Contrary to the industrial production of synthetic fertilizers, biological N fixation (BNF) relies on solar energy provided by the legume host to the bacterial nitrogenase, which reduces atmospheric N2 to ammonia to be used by the plant (Franche et al 2009)
According to Adams et al (2018), BNF was stimulated if the soil around the legume rhizosphere lacked N, while it was inhibited if the soil N was in surplus

Summary

Introduction

Agriculture is the world’s single largest driver of global environmental change (Rockström et al 2017). Sustainable or ecological intensification of agriculture (Tittonell 2014, Mahon et al 2017) is offered as one solution to this problem. On a field or farm scale it can mean production of more food or feed while reducing the potential negative environmental impacts and at the same time increasing contributions from natural capital and avoiding the unnecessary fertilizer inputs (Pretty et al 2011). Replacement of synthetic N fertilizer with biological N fixation (BNF) offers one important natural capital mean for achieving more sustainable food and feed production. Contrary to the industrial production of synthetic fertilizers, BNF relies on solar energy provided by the legume host to the bacterial nitrogenase, which reduces atmospheric N2 to ammonia to be used by the plant (Franche et al 2009). According to Adams et al (2018), BNF was stimulated if the soil around the legume rhizosphere lacked N, while it was inhibited if the soil N was in surplus

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