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

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.

Response of Soil Bacterial Community Diversity and Composition to Time, Fertilization, and Plant Species in a Sub-Boreal Climate

“…Generally, the soil had lower NO 3 -N content and higher moisture content in the autumn than in the summer (Li et al, 2019). From summer to autumn, the relative abundances of Acidobacteria and Bacteroidetes increased, while that of Actinobacteria decreased.…”

“…Soil NH and NO were extracted with 2 M KCl and measured with Lachat QuickChem 8000 (Lachat Instruments, Milwaukee, WI, United States), soil pH and EC were determined in a 1:2.5 (w/w) soil–water mixture, and total C and N were determined with TruSpec Elemental Determinator (LECO, United States). The details were reported in Li et al (2019) .…”

“…Hence, we established a 3-year field study in the sub-boreal conditions of southern Finland. We have previously shown that the management and the season induced temporal changes in crop growth and soil properties, with the legume-grass mixture providing particular advantages over the pure stands of red clover (Trifolium pratense) and timothy (Phleum pretense) in terms of improved pasture yield and reduced potential N loss (Li et al, 2019). Given that the changes in soil organic C content, N availability, C/N ratio (Marschner et al, 2003;Ramirez et al, 2010), soil pH (Enwall et al, 2007;Shen et al, 2010), and soil moisture and temperature (Lauber et al, 2013) could drive the differences in microbial communities, we hypothesized that the response of community diversity measures (richness, Shannon diversity, and Shannon evenness) and composition would change over time and that the higher N input level in the third year would result in greater differences between treatments.…”

Sustainable Mixed Cropping Systems for the Boreal-Nemoral Region

“…Plant diversity in the perennial mixtures increases the N 2 fixation mainly as a result of the non-legume species competition for N from soil (Carlsson and Huss-Danell, 2003;Rasmussen et al, 2012). For example, Li et al (2019) showed that an unfertilized timothy-red clover mixture had higher dry matter yield than N fertilized sole stands in Finland because through biological N fixation plants were able to utilize resources more efficiently. Dhamala et al (2017) concluded that perennial mixtures need to have non-legume species to maximally benefit from the N 2 fixation.…”

Stable Nitrogen-Cycling Capacity in Relation to Fertilization and Intercropping in a Sub-Boreal Grassland

“…We aimed to disentangle the underlying mechanism of how the agricultural management regimes in these sub-boreal grasslands affect microbial communities and their capacity for N-cycling and how such changes may affect crop yield. Hence, we conducted an integrated analysis, including crop yield, soil properties and the composition of soil bacterial communities previously reported from the same field experiment [20,23], along with the abundance of several functional groups within the N-cycling communities. We specifically tested the hypotheses that i) the soil microbial communities mediate management effects on crop yield and the potential for both N retention and N 2 O sink capacity and ii) an increase in potential for N retention increases crop yield.…”