The biosolid soil amendment N-Viro Soil (NVS) and a Streptomyces isolate (S 99-60) were tested for effects on root-knot nematode [RKN (Meloidogyne incognita)] egg populations on cantaloupe (Cucumis melo). Application of 3% NVS (dry weight amendment/dry weight soil) in the soil mixture resulted in significant (P ≤ 0.01) suppression of RKN egg numbers on cantaloupe roots compared to all other treatments, including 1% NVS and untreated controls. Ammonia accumulation was higher with the 3% NVS amendment than with any other treatment. Adjustment of soil pH with calcium hydroxide [Ca(OH)2] to the same levels that resulted from NVS amendment did not suppress nematode populations. When cultured in yeast-malt extract broth and particularly in nutrient broth, S 99-60 was capable of producing a compound(s) that reduced RKN egg hatch and activity of second-stage juveniles. However, when this isolate was applied to soil and to seedling roots, no suppression of RKN egg populations was observed on cantaloupe roots. Combining S 99-60 with NVS or Ca(OH)2 did not result in enhanced nematode suppression compared to treatments applied individually. The results indicated that NVS application was effective at suppressing RKN populations through the accumulation of ammonia to levels lethal to the nematode in soil.
Susan L.F. Meyer, Inga A. Zasada, Mario Tenuta, and Daniel P. Roberts
Xiuling Tian and Youbin Zheng
beneficial microbes), waste DE from beer brewing, and a greenhouse nutrient solution that had been reused for more than 20 years on six water- or soil-borne plant pathogens commonly found in Ontario greenhouses. Materials and Methods Inhibition subtracts used
R.G. Linderman and E.A. Davis
Composted materials with high humic and microbial content, and their water extracts, are increasingly used in the nursery industry as potting mix components or as liquid amendments for the purposes of enhancing plant growth. Common speculation is that such materials either contain beneficial microbes or stimulate those in or added to the medium, such as vesicular-arbuscular mycorrhizal (VAM) fungi, known to have growth-stimulating effects on plants. Experiments were conducted to determine if one such compost enhanced plant growth by stimulating VAM fungi or other growth-enhancing microbes, by simply providing limiting nutrients [phosphorus (P)], or a combination of the two. Highly mycorrhiza-responsive onion (Allium cepa) `White Lisbon' was used to evaluate the interactions of composted grape pomace (CGP), the VAM fungus Glomus intraradices, and preplant soil heat treatment on onion growth under P-limiting conditions. CGP and its water extract stimulated onion growth under P-limiting conditions in the absence of VAM; the extract was more effective than the granular CGP. Growth was enhanced further by addition of G. intraradices, and the extract enhanced its colonization of roots. Heat pretreatment of the soil inconsistently affected growth-enhancement by CGP or its extract. Thus, inoculating plant roots with mycorrhizal fungi in combination with this composted organic amendment or its extract was beneficial. The effect could have been due to the CGP providing a source of P to overcome the P-limiting conditions, and to the mycorrhizal fungus enhancing P uptake by its extraradical hyphae and thereby increasing nutrient-use efficiency.
R.G. Linderman and E.A. Davis
Coconut fiber dust (coir) is being used as a peat substitute or amendment to potting mixes with varied results. However, its microbial composition and compatibility with beneficial microbes that might be added to growth media in the nursery, such as mycorrhizal fungi, has not been determined. In this study, coir was amended to a peat-based medium (15%, 30%, 45%, and 60% by volume) to determine its effects on growth of several ornamental plants and on the formation and function of the arbuscular mycorrhizal (AM) fungus Glomus intraradices. Mycorrhizae formed as well, and usually better, in all the coir-amended peat treatments as in peat alone. The magnitude of growth enhancement due to mycorrhizae was small for the plants tested in these media compared to that which usually occurs in soil-based media. In this experiment, plant growth responses appeared to be independent of level of mycorrhizal colonization and were plant species dependent. Consistent growth enhancement from mycorrhizae only occurred with marigold (Tagetes patula). With germander (Teucrium fruticans), growth was depressed with mycorrhizal inoculation in the medium composed of 60% coir. Growth of lavender (Lavandula augustifolia) was depressed in all coir-amended media, with or without AM inoculation, compared to the nonamended control. These results confirm previous reports of varied response of plant species to coir, and indicate the lack of any detrimental effects of coir on mycorrhiza formation.
S.R. Mueller and W.R. Kussow
Immature sand matrix golf putting greens are considered to be inhospitable environments for microorganisms as compared to native soils. Subsequently, turfgrass quality may suffer in the absence of beneficial microbe–plant interactions. The turfgrass industry has responded by marketing a wide array of biostimulant products that claim to improve putting green quality through influences on soil microbial activity. A field study was conducted to determine what influences five commercial biostimulants have on the root-zone microbial community and creeping bentgrass (Agrostis stolonifera L.) quality. A three year old U.S. Golf Association (USGA) specification sand-based putting green (e.g., 80% sand: 20% peat humus by volume) was the test site. Commercially available biostimulants and fertilizer were applied biweekly from May until August 2000. The soil microbial community was characterized using soil enzymes and substrate utilization profiles. Turfgrass quality was determined visually by evaluating color, percentage of localized dry spot (LDS), and overall uniformity. Nutrient uptake levels were monitored to ascertain if increases in quality related to plant health. Visual quality of the putting green was significantly improved (p < 0.05) by the commercial biostimulants. The positive response to biostimulants was not of a nutritional origin. The biostimulants did not effectively alter the putting green microbial community in terms of enzyme activity or substrate utilization. However, a seasonal decline was detected in cellulase activity, which prevailed over any treatment effect, suggesting the root-zone microbial community responded to summer decline of bentgrass roots and concomitant decreases in quantities of root exudates. Visual improvements in putting green quality during the period of summer stress were primarily associated with the incidence of LDS. Visual LDS ratings were significantly reduced (less LDS) by applications of the biostimulants on each observation date (p < 0.05) and over the entire course of the experiment (p < 0.10). Surfactant properties of the biostimulants therefore appeared to play a major role in the improvements in putting green quality. This does not negate the fact that the seaweed extracts and humic acids in the biostimulants may have improved the heat and moisture stress tolerance of the bentgrass once the LDS formed.
Yiyun Lin and Michelle L. Jones
synergistically improve plant growth and development. However, the formulations are often established based on experience instead of solid scientific evidence to support the effectiveness of the products ( Rouphael and Colla, 2018 ). Beneficial microbes can
M.D. Richardson and K.W. Hignight
., 2006 ) and fungi ( Salter and Smith, 1986 ), incorporate beneficial microbes ( Rice et al., 2001 ), enhance seed handling characteristics, and improve germination and seedling establishment ( Peltonen-Sainio et al., 2006 ; Scott and Hay, 1974
Lantian Du, Baojian Huang, Nanshan Du, Shirong Guo, Sheng Shu, and Jin Sun
ability (e.g., pathogenic bacteria, fungi, and nematodes), and the number of beneficial microbes decreases, thus affecting the normal growth of crops and causing yield reductions. The use of reasonable cropping systems and the employment of allelopathy
Kwang Jin Kim, Eun Ha Yoo, Myeong Il Jeong, Jeong Seob Song, Seung Youn Lee, and Stanley J. Kays
efficiency over 3 d is likely greater than the increase in beneficial microbe populations could account for, i.e., in some instances, up to a six times increase in efficiency. Regardless of the cause, increasing toluene removal efficiency is advantageous to
Chenping Xu and Beiquan Mou
lettuce leaf number, area, FW, DW, and chlorophyll index. The synergetic effects of many factors, such as suppression of plant diseases, insects, and nematodes, increased biomass and activities of beneficial microbes, high nitrogen and calcium content