Composted Biosolids for Agronomic and Horticultural Crop Production

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1 Composted Biosolids for Agronomic and Horticultural Crop Production James E. Shelton, J. R. Joshi, and P. D. Tate Department of Soil Science North Carolina State University Mountain Horticultural Crops Research and Extension Center Sustainable agriculture is dependent upon maintaining soil productivity which has been equated to soil organic content (Tisdale et. al. 1985). Maintenance of soil organic matter is extremely difficult under tilled cropping systems which increases aeration, hastens organic matter decomposition and facilitates erosion, resulting in physical loss of organic matter and other soil components. Limited land resources existing in the southeastern United States requires frequent, if not continuous, production on the same land which has led to a decrease in organic matter, a reduction In the quality of soil physical and chemical properties and a decrease in yields of tobacco (Miner and Sims, 1983). The greenhouse and nursery industries have also relied heavily on peat moss for the improvement of container media for crop production. Peat moss is not an unlimited resource and regulated harvest in some countries has resulted in increasing price and a significant cost in container media. Land application of wastewater biosolids is an increasingly popular method of utilizing wastewater biosolid residuals. However, federal (40 CFR Part 503) and state regulations established metal loading rates which limit long term use of land for this purpose. Increasing urbanization. local political uncertainties, and unsuitable weather conditions may also limit land application in some communities. Composting of these residuals with carbon sources such as wood waste would enhance product quality and allow for greater distribution and is a promising solution to the problem. While the literature is replete with reports on the beneficial uses of wastewater biosolids on various crops, the reports on composted wastewater biosolids are limited (Woodbury, 1992). A literature review by Shiralipour et. al., 1992, reported that the major benefit from the application of compost to soil was derived from the improved physical and chemical properties related to the increased organic matter content rather than its value as a fertilizer. Wastewater biosolids composting using woodchips has the potential of producing a high quality compost with relatively high nutritive value which could increase soil organic matter and supply nutrients in a slowly available form. In order to diversify its biosolids management program to meet long-term requirements the Charlotte- Mecklenburg Utility Department (CMUD) selected composting as a long-term biosolids management alternative and established a pilot project to evaluate the process and produce compost for crop production research (Huffman et. al., 1995). The studies reported herein are a part of the CMUD production research component. Methods The pilot project composting methodology was an aerated static pile using dewatered biosolids with woodchips and sawdust as bulking agents (Huffman et al., 1995). The feedstock ratio of compost, used in these studies, was 3: 1 :OS of woodchips, biosolids, sawdust composted for 28 days, using aerated static pile technology, under a covered open sided facility and then moved to an outdoor location for 30 days maturing. Compost was screened through a 1.27 cm mesh and met the Class A pathogen reduction criteria, pollutant concentration limits (PC) and veltar attraction requirements (VAR) established by EPA for exceptional quality (EQ) compost. Compost also met North Carolina regulations for unrestricted use. Compost was analyzed for C, N, P, K, Ca, Mg, Mn, Zn, AI, Cu, Pb, Ni, and Cr by the Analytical Services Laboratory - Department of Soil Science, North Carolina State University. C and N were analyzed using a Perkin- Elmer Model 2400 CHN Elemental Analyzer (Perkin Elmer Corp., Nonvalk, Connecticut). P, K, Ca, Mg, Mn, Zn, AI. Cu, Pb, Ni, Cd, andcrwere determined byicp using a PerkinElmerPlasma 2000 emission spectrometer following a dry ashing in a muffle furnace at 500 C with dissolution in HCI.

2 A turf typefescue (cv. Bonanza)-bluegrass (standard) seed mixture (9:l by weight) was seeded on 4 cm of wastewater biosolids compost (WBC) over perforated plastic at a seeding rate of 390 kg ha". No fertilizer amendments were applied until the time of first clipping 24 days after seeding at which time weekly fertilization with m-g kg" N as Peters ( ) soluble fertilizer was applied. Two additional clippings were made 48 and 60 days after seeding. Clippings were oven dried at 50 C and weighed. Rooted cuttings of dwarf nandina (Nana domesticus L.) cv. Fire Power was set in 2 gallon containers, in a pinebark compost media containing 0, 25, 50, 75, 100% WBC. Each media combination was fertilized with 3, 6 or 9 kg m-j of Osmocote ( ) (Sierra Chemical Co., Milpatis, CA), a slow release fertilizer mixed prior to potting. Each treatment was replicated 3 times. After 100 days of growth plant height (ht.), diameter (D) was measured in centimeters and plant density (d) was rated on a scale of 1-10 by 4 individuals. A growth quality index (GQI) was calculated as (ht+dr) x d/ioo. Fall color development was rated by 4 individuals. Rooted cuttings of geranium (Geraniaceae L.) were grown in 2 qt. containers containing media composed of pine bark and WBC at 0, 25, , 100% compost by volume. Fertilizer application rates of 50, 100, or 200 ppm N solution (as ) was applied weekly. Each combination of compost and fertilizer was replicated 4 times. Growth measurements consisting of height and diameter were taken at 30 and 45 days after transplanting, Bloom bud stalk counts were also taken at 45 days. Results and Discussion The chemical and physical properties of WBC used in the experiments reported herein are shown in Table 1. Primary nutrient content were generally higher than other types of compost (Shelton, 1995). Micronutrients and heavy hetals were generally lower than was reported by Shelton for other composts with the exception of Cr. All metals were below EPA-Part 503 PC limits. Greenhouse sod production - Seeding germination and early growth of fescue-bluegrass was excellent as shown in Fig. 1 with the first clipping 24 days after seeding. Fertilizer treatments initiated at the time of first clipping resulted in a small but not significant increase in biomass production during the following 24 days (2nd clipping, Fig. I). However, by the 3rd clipping, 60 days after seeding there was a significant response to the fertilizer treatments (Fig. I). This growth response suggests a readily available nutrient supply from the compost in the initial growth stages, which was reduced and adequate levels were not being mineralized for maximum growth during the rapid growth stage following the second clipping. Thus, a significant response to fertilizer treatments. Sod was of acceptable quality for marketing at the end of the 60 day period. Based upon the results of these studies, sod production is feasible using compost over perforated plastic or other landscape fabrics without soil requirements. However, these experiments were conducted under greenhouse conditions and longer periods may be required outside. Although not reported here an outdoor sodstudywas established using a municipal solid waste compost over perforated plastic. This crop was seeded in October and harvested in late March. Dwarf nandina - Figure 3 shows the GQI at 100 days of dwarf nandina grown in pine bark-wbc media containing 3, 6, 9 kg m-' of Osmocote IO ( ) slow release fertilizer. Increasing the percentage of compost in the media significantly (P=0.05) increased growth quality. Response to fertilizer rate was dependent on the composition of the growing media. With media containing 50 percent or less compost a significant growth response occurred with increasing fertilizer rates except in the standard bark media containing no compost. Media containing 75 or 100 percent compost did not respond to increasing fertilizer rates indicating that mineralization of the WBC was releasing adequate nutrients for maximum plant growth. A desirable red foliage associated with this plant was significantly decreased with WBC or by increasing fertilization (Fig. 3). Fall color development is a function of leaf chlorophyll content which is enhanced with nitrogen addition either from the fertilizer or mineralized from the compost. Thus, the standard bark growing media with the lowest fertilizer addition resulted in the highest color rating. 1 I7

3 Geranium - The addition ofcompost to pinebark significantly increasedgrowth of geranium but there wasno difference due to compost rates above 25% (Fig. 3). Growth response to increasing fertilizer rates were reduced at increasing percentages of compost with no significant difference above the 50% compost rate. Bloom bud response to compost additions was significant to both increasing rates of compost and fertilizer up to the 50% compost rate (Fig. 3). Mineralization of nutrients contained in the compost was apparently adequate to support growth and bloom bud response in the 75 and 100% compost media. Conclusion Woodchips and sawdust composted with wastewater biosolids serving as a nitrogen source produced an "exceptional quality" compost with lowheavymetal content. Theproductimproved the rate of sod grownon perforated plastic as compared to conventionally grown sod and may significantly reduce the rotation time while utilizing none of the valuable topsoil. As a media component for greenhouse and container grown plants, compost gave excellent results andacted as a slow release nutrient source whichmay serve as maintenance during the marketing process which may extend over several weeks or months. The results of these investigations show that composted biosolids may be used effectively in the production of agronomic and horticultural crops. Although cost of compost at the national level is erratic at the present time this is thought to be due to unfamiliarity of producers in how to use the product. Compost appears to be a suitable replacement for peat moss in the greenhouse and nursery industry and should be available at a lower cost. However. based upon the potential use of compost as reported by Slivka et. al., 1992, prices may increase as growers learn to use the product. Acknowledgements Appreciation is expressed to the Water Resources Research Department (CMUD) for their financial support and cooperation. institute and Charlotte Mecklenburg Utilities I18

4 References Huffman, E.. J. Shelton. and J. Bellamy Pilot scale testing of the Charlotte aerated pile compost process. ProceedingsComposting in the Carolinas Conference. pp January 18-20, edr.k. White, R. Rubin and F.J. Wolak. Miner, G.S. and J.L. Sims Changing fertilization practices and utilization of added plant nutrients for efficient production of burley and fluecured tobacco. In:Recent Advances in Tobacco Science #9 Production of Quality TobaccoLeaf. Symposium 37th Tobacco Chemist Research Conference October 11-13, Washington, DC pp Shelton. J.E Effect of various feedstocks on compost properties and use. Proceedings Composting in the Carolinas Conference. pp January 18-20, ed R.K. White, R. Rubin and F.J. Wolak. Tisdale, S.L., W.L. Nelson and J.D. Beaton Cropping systems and soil management. In: Soil Fertility and Fertilizers. 4th Edition. Macmillan Publishing Co. New York, NY. pp Wood6ury, P.B Trace elements in municipal solid waste composts: A review of potential detrimental effects on plants, soil biota, and water quality. Biomass and Bioenergy 3:

5 Table I. Characteristics of WBC compostused in these studies. Parameter - YO Parameter ma kg" C 39.8 B 15.0 N 1.75 Mn P cu I 19.2 K Zn Ca 1.56 Pb 24.0 Mg 0.19 Ni 9.7 S 0.34 Cd 1.1 Fe 0.94 Cr 92.7 AI 0.92 Na CI Soluble Salts. 10 mmhs cm" Bulk Density 0.51 g cc" ph (2: 1) 6.5

6 Fertilizer Rate (mg kg -l) 50 I Days after seeding Fig. 1. Effect of weekly fertilization, mg kg-' of N as 20N-8.6P-16.6K ( ), on growth of bluegrass-fescue sod grown on wastewater biosolids compost. No fertilizer applied until first clipping (24 days). 121

7 Fertilizer Rate (kg m ) Color Rating: 1, Poor; 10, Excellent.I I YO Compost Fertilizer Rate ( kg m-3) 05 HI0 HI5 GQI = [(Ht + Wd)/2]*Density/ YO Compost Fig. 2. Effect of media composition (pine bark-compost) and fertilizer rate on growth quality index and fall color development of dwarf nandina I22

8 250 Fertilizer Rate ( ppm) 050 a100 M n E 150 v I bd ; 50 0 L Oh Compost 75 Fertilizer Rate ( ppm) YO Compost 100 Fig. 3. Effect of media composition (pine bark-compost) and weekly fertilizer rate on growth and bloom stalk count of geraniums 123

Ecological Landscaping Association's 2013 Conference & Eco-Marketplace February 27, Geoff Kuter, Ph.D. Agresource Inc.

Ecological Landscaping Association's 2013 Conference & Eco-Marketplace February 27, 2013 Geoff Kuter, Ph.D. Agresource Inc. www.agresourceinc.com Since 1984, providing organic waste management services