Abstract
Planting grass-legume mixtures may be a good option to improve soil health in addition to increased forage productivity, improved forage nutritive value, and net farm profit in a hay production system. A field experiment was conducted from 2011 to 2014 at Lingle, Wyoming to evaluate soil microbial biomass under different seeding proportions of two forage grasses (meadow bromegrass, Bromus biebersteinii Roem. & Schult.; and orchardgrass, Dactylis glomerata L.) and one legume (alfalfa, Medicago sativa L.). Nine treatments included monoculture grass, monoculture legume, one grass and one legume mixture, two grasses and one legume mixture, and a control (not seeded with grass or legume). Monoculture grass received either no nitrogen (N) or N fertilizer (150 kg N ha−1 year−1 as urea) whereas monoculture legume, grass-legume mixtures, and control plots received no N fertilizer. The study was laid out as a randomized complete block design with three replications. The plots were harvested 3–4 times each year after the establishment year. Soil samples were collected and analyzed for microbial biomass using phospholipid fatty acid (PLFA) analysis at the end of May in 2013 and 2014. Soil samples were also analyzed for mineralizable carbon (C) and N in 2013 and 2014. The total above-ground plant biomass was higher in 50–50% mixture of grass and alfalfa than monoculture alfalfa and monoculture grass (with and without N fertilizer) during the entire study period. The application of N fertilizer to the grass hay production system had little effect on improving mineralizable soil C, N, and soil microbial biomass. However, grass-legume mixture without N fertilizer had great effect on improvement of mineralizable soil C and N, and total, bacterial, and actinomycetes microbial biomass in soil. The 50–50% mixture of grass and alfalfa performed consistently well and can be considered to use in Wyoming conditions for improving soil health and forage productivity.
Highlights
Soil microorganisms are the key driver for various soil biochemical processes such as organic matter decomposition, nutrient cycling, and soil aggregate formation [1,2]
Soil under the perennial crop production system has a higher soil microbial biomass and diversity compared to annual crop production systems due to the reduction in soil disturbance and addition of more organic residues into the soil [9,10]
The objective of the study was to assess the effect of monoculture grass, monoculture legume, and mixtures of grass and legume on soil mineralizable C, N, and soil microbial biomass
Summary
Soil microorganisms are the key driver for various soil biochemical processes such as organic matter decomposition, nutrient cycling, and soil aggregate formation [1,2]. These microorganisms rely on organic carbon (C) for their growth, development, and activities in soil [3]. There is good correlation between aboveground plant species and the belowground microbial community [11] This is due to variations in quantity and quality of rhizodeposits under different plant production systems [13,14] and increased abundance and diversity of both the aboveground species and belowground microbial population [15]
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