Microwave technology has wide applications, including extraction of active compounds in biomass and compost for agricultural use. A study was carried out to determine the effects of microwave power level from 0 (control) to 1000 W on the properties and active microbial groups in vermicast, and how it may impact the photosynthesis, plant growth, and yield of kale (Brassica oleracea var. sabellica) ‘Red Russian’. Heat accumulation in the vermicast increased rapidly to a peak of 86 °C at 400 W before declining to 68 °C at 1000 W. Vermicast water loss increased exponentially up to 800 W before declining. The C:N ratio of the vermicast was reduced at ≥600 W while the pH remained the same. In a 2D-principal component analysis biplot, vermicast treated at 600, 800 and 1000 W were associated with Gram-positive (G+), GGram-negative (G−), G + G− bacteria, protozoa, and fungi groups while the 0, 200, and 400 W treated vermicast were associated with eukaryotes. However, the trend for total microbial mass was 200 W = 400 W > 0 W > 600 W = 800 W = 1000 W. Kale leaf anthocyanin, chlorophylls, and carotenoids were significantly (p = 0.001) increased by the 400 W or 600 W treatment compared to the other treatments. Stomatal conductance, transpiration, and photosynthesis rates were increased by the 400 W followed by the 600 W. As a result, yield of kale grown in the 400 W microwaved vermicast was the highest. Future studies will explain the functions of specific microbial populations and elemental composition in microwaved vermicast.
A study was performed to assess nutrient release from biochar inoculated with solid vermicast (SVB), vermicast tea (VTB), deionized water (DWB), uninoculated biochar (Bioc), and Promix-BX (Pro-BX). The growth response of Swiss chard ( Beta vulgaris subsp. vulgaris) cv. Rhubarb chard was also assessed. Comparatively, nutrients were released slowly from treatments SVB and VTB compared to the other treatments. The rate of nutrient release determined by total dissolved solids and electric conductivity from the Pro-BX was the highest. The trend for the plant growth components, total leaf surface area and leaf fresh weight at first harvest, was Pro-BX > Bioc > DWB = SVB > VTB. The only treatment that increased total leaf area and leaf fresh weight at the second harvest by approximately 1.02- and 1.88-fold was VTB. Leaf fresh weight was significantly reduced by approximately 0.33-fold for DWB, 0.28-fold for Bioc, and 0.70-fold for Pro-BX but was not altered by SVB at the second harvest as compared to the first harvest. A 2-dimensional principal component analysis (PCA) biplot confirmed that treatment Pro-BX increased plant growth components at the first harvest only. The locations of SVB and VTB on the PCA biplot confirmed their efficacies, which led to increases in the plant growth components at the second harvest. Overall, the VTB adsorbed more nutrients onto its surface that were slowly released to enhance the Swiss chard cv. Rhubarb chard plant growth at the second harvest. Further studies should consider microbial activities.
A combination of vermicast and sawdust mixed medium is commonly used in horticulture, but the added benefit of microbial inoculation and mechanism of nutrient availability are unknown. This study was done to determine nutrient mineralization and nutrient release patterns of different combinations or a mix of vermicast-sawdust growing media amended with or without Trichoderma viride (10 5 spores/g). The mixed-media treatments were (1) 80% vermicast+20% sawdust; (2) 60% vermicast+40% sawdust; (3) 40% vermicast+60% sawdust; (4) 20% vermicast+80% sawdust; and (5) sawdust alone (control). Total dissolved solids, electric conductivity and salinity increased with each sampling time following submergence in deionized. Nutrients released from media without T . viride were significantly higher than the corresponding media with added T . viride . Overall, the starting total nitrogen of the different media did not change during the incubation period, but nitrate-nitrogen was reduced to a negligible amount by the end of day 30 of incubation. A repeated measures analysis showed a significant effect of Time* T . viride *Treatment on total dissolved solids. Redundancy analysis demonstrated a positive and strong association between media composed of ≥40% vermicast and ≤60% sawdust with or without T . viride and mineral nutrients released, electrical conductivity, total dissolved solids and salinity. These findings suggest that fast-growing plants may benefit from 40% to 60% vermicast added to 40% to 60% sawdust without T . viride while slow-growing plants can benefit from the same mixed medium combined with the addition of T . viride . Further investigation is underway to assess microbial dynamics in the mixed media and their influence on plant growth.
Vermicast (VC)-sawdust (SD) influences growing medium, microbial community, and nutrients mineralization but understudied. We determined the active microbial composition and nutrients mineralization of VC-SD mixed medium without (A) or with (B) addition of 10 5 spores/g T. viride at (1) 80% VC+20% SD; (2) 60% VC+40% SD; (3) 40% VC+60% SD; (4) 20% VC+80% SD; and (5) sawdust alone. Six major microbial groups were found based on microbial membrane phospholipid fatty acids determination. These include gram-positive (G+), gram-negative (G-), fungi, protozoa, eukaryotes, and Archea. Vermicast-sawdust with T. viride did not (p>0.05) alter the active microbial composition. A moderately positive correlation was found between microbial groups and mineral nutrients. A2 and B2 had highest pH and iron in addition to protozoa and fungi/bacteria ratio, while B1 and B3 had the highest amounts of sodium and phosphatidylglycerol. A2, A3, B2, and B3 had the most diverse microbial community and the highest overall mineral nutrients compared to the other media. Overall, there was temporal reduction in active microbial communities after 30 days of incubation. Therefore, VC-SD ratios 40:60 and 60:40 incubated within 30 days can potentially improve plant growth and productivity. Non-active microbial populations must be quantified in future studies.
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