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  • Author or Editor: Rebecca N. Brown x
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Using organic wastes as agricultural amendments is a productive alternative to disposal in landfills, providing nutrients for plant growth and carbon to build soil organic matter. Despite these benefits, a large fraction of organic waste is sent to landfills. Obstacles to the adoption of wastes as sources of plant nutrients include questions about harmful effects to crops or soils and the wastes’ ability to produce satisfactory yields. We compared six organic waste amendments with a mineral fertilizer control (CN) to determine effects on soil quality, soil fertility, crop quality, and crop yield in 2013 and 2014. Waste amendments were applied at a rate sufficient to supply 10,000 kg organic C/ha over two seasons, and mineral fertilizer was applied to control plots to provide 112 kg-N/ha/yr. The experiment was laid out in a randomized block design with four replicates and three crops: sweet corn (Zea mays L. cv. Applause, Brocade, and Montauk), butternut squash (Cucurbita moschata Duchesne cv. JWS 6823), and potatoes (Solanum tuberosum L. cv. Eva). Amendment with biosolids/yard waste cocompost (BS), dehydrated restaurant food waste (FW), gelatin manufacturing waste (GW), multisource compost (MS), paper fiber/chicken manure blend (PF), and yard waste compost (YW) did not have a negative impact on soil moisture, bulk density, electrical conductivity (EC), or the concentration of heavy metals in soil or plant tissue. Our results indicate potential uses for waste amendments including significantly raising soil pH (MS) and increasing soil organic matter [OM (YW and BS)]. The carbon-to-nitrogen ratio (C:N) of waste amendments was not a reliable predictor of soil inorganic N levels, and only some wastes increased potentially mineralizable nitrogen (PMN) levels relative to the control. Plots amended with BS, FW, and GW produced yields of sweet corn, butternut squash, and potatoes comparable with the control, whereas plots amended with YW, PF, and MS produced lower yields of sweet corn, squash, or both, although yields for potatoes were comparable with the control. In addition, the marketability of potatoes from PF plots was significantly better than that of the control in 2014. None of the wastes evaluated in this study had negative impacts on soil properties, some provided benefits to soil quality, and all produced comparable yields for at least one crop. Our results suggest that all six wastes have potential to be used as sources of plant nutrients.

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Consumer demand for cleaned squid generates a substantial amount of waste that must be properly disposed of, creating an economic burden on processors. A potential solution to this problem involves converting squid byproducts into an organic fertilizer, for which there is growing consumer demand. Organic fertilizers are reputed to offer advantages that synthetic fertilizers cannot provide, such as increasing soil water- and nutrient-holding capacity and promoting the growth of beneficial soil organisms. To evaluate the effectiveness of hydrolyzed squid waste as an organic fertilizer, we quantified soil fertility and turfgrass quality on perennial ryegrass turf (Lolium perenne L.) amended with two types of fertilizer: squid-based (SQ) or synthetic (SY). Field plots were established on an Enfield silt loam in Kingston, RI, and liquid (L) or granular (G) fertilizer formulations of squid or synthetic fertilizers were applied at 0, 48, 146, and 292 kg nitrogen/ha/year. Soil physical, chemical, and biological properties were determined monthly and turfgrass quality was determined periodically during the growing season in 2008 and 2009. Squid hydrolysate applied as a liquid (SQL) and granular (SQG) fertilizer consistently provided high-quality, uniform turf when compared with synthetic fertilizer applied at the same rate. Soil concentrations of NO3, NH4, PO4, pH, moisture, soil organic matter, C:N ratio, and levels of trace metals were unaffected by fertilizer type, formulation, or rate throughout the two-year study. Both squid-based organic fertilizer formulations gave significantly higher microbial activity rates than their synthetic counterparts regardless of application rate. Conversion of squid processing byproducts into fertilizer has the potential to improve turfgrass quality while providing a sustainable solution to waste disposal problems in the seafood processing industry.

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