Xtremehorticulture

Heavy Metal Content in Tomatoes Grown in Soils with Biosolids

HEAVY METAL NUTRIENTS IN TOMATO PLANTS CULTIVATED IN SOIL AMENDED WITH BIOSOLID COMPOSTS1 Authors:   W.J. Melo, A.A.D. Cintra, M.D. Revoredo, L.T. Braz Keywords:   Lycopersicon esculentum Mill., Cu, Mn, Zn, composting process, waste DOI:   10.17660/ActaHortic.2003.627.26 Abstract:The use of biosolids in horticulture could contribute to recycle residues produced by men. This study analyzed concentrations of Cu, Mn and Zn in the compost during fermentation, in the soil amended with the composts and in the tomato plant materials. Five composts were produced using sugar-cane bagasse, biosolid and cattle manure in the proportions: 75-0-25; 75-12.5-12.5; 75-25-0; 50-50-0 and 0-100-0 (composts with 0; 12.5; 25; 50 and 100% biosolid), respectively. These composts were used in an experiment with 6 treatments (the 5 composts and a control with mineral fertilization) in a design of randomized blocks with a split plot design. The control and the treatment of 0% biosolid received inorganic nitrogen. All the treatments received the same amount of N, P and K. Two tomato plants were cultivated in each 24 L pot, in a greenhouse at the Technology Department of the Faculdade de Ciências Agrárias e Veterinárias of the Universidade Estadual Paulista in Jaboticabal County, São Paulo State, Brazil. The concentrations of Cu, Mn and Zn were evaluated in the compost 7, 27, 57, 97 and 127 days after composting began, in the soil 0 and 164 days after the compost applied, and in the plants. Compost, soil and plant samples were subjected to digestion with HNO3, H2O2 and HCl and the metals were determined by AAS. There were positive and significant correlations between Mn in the compost and Mn uptake by the plant (0.46 p>0.05), and between Zn in the compost and Zn concentration in the plant (0.78 p>0.05). Cu, Mn and Zn concentrations increased during composting. The biosolid in the compost supplied Cu and Zn to tomato plants, and the cattle manure supplied Mn to the plants. Note:  There is much discussion in horticulture regarding heavy metals in soils and in plants. What are heavy metals? In the periodic table of elements, heavy metals are those elements identified as metals that have a high atomic weight.  Heavy metals include those that are considered toxic to us and other animals, as well as metals which are nutrients. In the research below, only heavy metals which are considered plant nutrients (at low concentrations) are taken into consideration. Copper = Cu, manganese = Mn, zinc = Zn are plant and animal nutrients at lower concentrations such as reported here. In this report, the heavy metals that were plant nutrients and use of biosolids was considered a “good” thing.

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Are Organic Fertilizers Really Organic?

The organic movement has a foothold in the turfgrass and ornamental industry. The same industry brewing for decades in home vegetable gardens, and then with small-scale producers, has emerged as a significant market percentage for commercial landscapers. Homeowners are asking for “organic” landscape plants, organic methods of controlling pests and applications of “organic” fertilizer to their landscapes. Migration of Organics to the Landscape Industry             Alternative methods for producing and maintaining ornamentals and turfgrass have been around for a long, long time. In the past, very few residential clients were willing to pay for the additional costa associated with the product. That may be changing thanks to local food movements and organic agriculture1. The word “organic” has become synonymous with “wholesome” and “safe”. Organic fertilizers for vegetable gardens             Organic has a different meaning in landscape horticulture industry. Organic can mean sources that are not synthetic or conventional. Organic amendments, such as municipal and animal sources of biosolids, can be applied to improve soil physical and chemical properties which in turn can improve turfgrass establishment rates, growth, and quality. We know, for instance, that in poor or marginal soils the incorporation of compost improves soil properties, increases soil nutrients and consequently improves plant growth. In soils with a naturally higher percentage of organic matter these improvements are less noticeable. Nitroform urea used in the landscape industry could be classified as an “organic” fertilizer even though it is manufactured  Composted Dairy Manure Reduced Turfgrass Disease in Colorado             Research at Colorado State University evaluated the effects of applying composted dairy manure as topdressing to Kentucky bluegrass. Researchers applied compost at the rates of 13.3, 26.6 and 40 cubic yards to the acre. Applying composted manure as topdressing to established bluegrass in 2003 through 2004 improved the soil’s physical properties and nutrient content. EZ Green Is a composted chicken manure product for the landscape industry that is OMRI listed product for the organic program by USDA             Although nothing new, the application rates are important. The two higher rates improved turfgrass overall quality and allowed the grass to retain color in the fall, early winter and green up faster in the spring. Not bad for a product that is not considered a fertilizer.             During the hot summer months the two higher application rates produced about 50% more clippings. The researchers concluded that compost improves turf quality and shoot growth via its action as a slow-release fertilizer. Lawn clippings remove from the grass and left on the curbside for dumping in landfills. These clippings are filled with valuable nutrients that could be returned to the lawn resulting in one less fertilizer application each year.             More turfgrass clippings sound like a potential landscaper’s nightmare but there is a positive side to this “problem”.  Increased amounts of clippings in summer months helps suppress the incidence of hot weather diseases. Infected leaf blades are removed through regular mowing and mulched back into the turfgrass sward or removed from the property.             Disease suppression by composts, composted biosolids and compost teas in vegetable crops has been documented fairly well. But research has been conducted on the suppressive effects of composts, such as biosolids, on turfgrass diseases as well, dating back 20 years or more. Compost tea applicator used for soil applications             This research shows promise to “organic” gardeners by reducing the application of fungicides, synthetic fertilizers and other chemicals to home lawns. Composts show promise in controlling turf diseases such as Pythium, summer patch, brown spot, dollar spot, red thread, necrotic ring spot and others.  Reductions in the applications of pesticides such as fungicides, directly supports the “organic” movement whether it is truly organic or not. Lawn clippings from commercial properties represent a huge amount of fertilizer that is removed from the lawn grasses and buried in landfills. Composted Biosolids Benefits To Landscapes Shown by Texas Researchers             Researchers at Texas A and M University, from 2005 through 2008, demonstrated the benefits from composts used for soil improvement and nutrient enrichment can be transferred from the sod farm to newly established landscapes. Previous studies with sod that recycled manure-based soil amendments as topdressing indicates that 77% of the phosphorus and 47% of the nitrogen might be removed and transported in a single sod harvest.             About one quarter of the cubic yard of composted biosolids was incorporated to rootzone depth in a cubic yard of native soil when establishing Tifway bermudagrass sod. Researchers measured that five times more nitrogen and seven times more phosphorus was available to turfgrass grown in biosolids compared to grass grown without biosolids. Fertilizer content of composted biosolid product by a local Las Vegas supplier             After two sod harvests, all of the nitrogen and phosphorus applied from the biosolids was removed with the sod. These nutrients were transferred, with the sod, to the landscape.             Although not demonstrated, researchers claimed that this could result in faster establishment times and better turfgrass cover in a shorter period of time. This, of course, would reduce the amount of fertilizers needed during sod establishment. Another coup for the organic movement.             They also found that sod established with biosolids was lighter in weight than sod grown without biosolids. Biosolids-grown sod contained more water but less native soil than sod without biosolids. This helped preserve the native soil. Less fuel is needed for transporting the sod. Organics, are you listening? Composts Release Fertilizer Nutrients Slowly             Composts, when used as a fertilizer, releases nutrients slowly, acting like a slow-release fertilizer. When establishing turfgrass in sod farm operations, rapid turfgrass establishment is important so a rapid release of nutrients, particularly nitrogen, is needed.             This was not going to happen with compost-amended soils. So the researchers applied either 50 or 100 pounds of nitrogen per acre at the time of sprigging (establishment) to supplement the slowly-released nutrients contained in the compost.             Because of the application of supplemental nitrogen, the time between harvests in biosolids-amended soil plus fertilizer was reduced 60% compared to

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