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.
symptoms. Table 1. Soil pH, soil organic C, and NH 4 OAc-extractable nutrient concentrations for compost sources and turfgrass soils before compost addition. Soil sampling and analysis. Five soil cores (2.5-cm diameter) were taken from
amount of P that was measured ( Table 4 ). In 2014 and 2015, CL had greater extractable soil P content than CL + MIN. All of the compost and compost + mineral treatments had greater extractable soil K than the CON, MIN, and FGN treatments, but there was
benefits to plants. Two strategies that have seen limited early adoption by innovative growers to provide cost-effective benefits from these high-value local inputs in small-scale commercial systems in the state include 1) using aqueous compost extracts or
include one or more of peat, compost, coconut coir, vermiculite, and perlite. Animal, plant, and mined materials are often incorporated by the manufacturer to provide additional nutrients and adjust pH. The diverse ingredients and their combinations create
Topdressing or incorporation of large, volume-based rates of composted biosolids (CB) can increase storage of soil organic carbon (SOC), supply essential mineral nutrients, and enhance turfgrass coverage during sod establishment and regrowth
The influence of compost (derived from MSW and biosolids) maturity on seed germination of several weed species was evaluated. A bioassay was developed by extracting 20 g of compost of different maturities with various volumes of water, then measuring germination percentage of ivyleaf morningglory (Ipomoea hederacea) seeds placed on extract-saturated filter paper in a petri dish. A 20 g (dry weight) compost: 50 mL of water generated an extract that produced the widest percentage seed germination variation in response to composts of different maturity. Ivyleaf morningglory, barnyardgrass (Echinochloa crus-galli L.), purslane (Potulaca oleracea L.), and corn (Zea mays L) were selected as plant indicators to determine the compost maturity stage with maximum germination inhibition. Compost 8-week-old decreased percent germination, root growth, and germination index (combines germination rate and root growth), and increased mean days to germination (MDG) of each plant indicator. Immature 8 week-old compost extract effect on MDG and germination percent of 15 weed species was evaluated. Extract from 8-week-old compost inhibited germination in most weed species, except yellow nutsedge (Cyperus esculentus). Compost extracts derided from immature (3-day, 4-, and 8-week-old) compost resulted in delayed and reduced germination percent of important economic weed species.
decreases, cells will begin to lose turgor, resulting in decreased leaf expansion and root elongation. When cell turgor approaches zero, leaves wilt ( Taiz and Zeiger, 2002 ). When the substrate becomes too dry for a plant to extract water from the substrate
Application of organic amendments can increase dissolved organic C (DOC) concentrations, which may influence movement of nutrients and heavy metals in soils. The objectives of this study were to investigate the influence of compost sources and application rates on concentrations of soil DOC, NO3-N, and extractable P over 29 months after a one-time application of compost to bermudagrass [Cynodon dactylon (L.) Pers.] turf. Few differences were evident between compost sources for soil total organic C (TOC), DOC, and NO3-N. However, the initial P content of compost sources significantly influenced soil extractable P. Increasing the rate of compost application increased soil TOC initially, but levels remained fairly stable over time. In contrast, DOC continued to increase from 3 to 29 months after application, suggesting that compost mineralization and growth of bermudagrass contributed to DOC dynamics in soil. Dissolved organic C was 98%, 128%, 145%, 175%, and 179% greater 29 months after application of 0, 40, 80, 120, and 160 Mg compost/ha, respectively, than before application. Rate of compost application had less effect on DOC than TOC, as DOC concentrations appeared controlled in part by bermudagrass growth patterns. Soil NO3-N was generally unaffected by compost application rate, as NO3-N decreased similarly for unamended soil and all compost treatments. Soil extractable P initially increased after compost application, but increasing the application rate generally did not increase P from 3 to 29 months. Seasonal or cyclical patterns of TOC, DOC, and extractable P were observed, as significantly lower levels of these parameters were observed in dormant stages of bermudagrass growth during cooler months.
A small, continuous flow compost reactor was employed to produce a compost from a shredded newspaper/kitchen waste mixture. Transit time through the reactor was 4 weeks and the compost was then stockpiled for 5, 7, 8 or 9 weeks prior to evaluation. Cress seed germination was not reduced in graded aqueous compost extracts, however, seedling radicle length was significantly reduced in the nondiluted extract.. Elemental analysis of the compost showed PO4 ond K to be about 20 and 2 times recommended levels and No 5 times the maximum level at 577 mg. liter-1. Electrical conductivity of the compost was 5 dS.m-1 and pH range was 6.2-7.3. Composts were leached with water to E.C.'s of 1-1.5 dS.m-1 before planting tomato seedlings. Dry weights of tomato seedlings grown 5 weeks in the composts were equal to those in a peat vermiculite control, except that dry weights of seedlings in the compost stockpiled for 5 weeks were less than those of control plants. Some residual inhibition of growth may hove remained in the compost for at least 5 weeks after the production dote but by the 7th week, no growth inhibition was apparent.