Compost use is becoming common in commercial vegetable production, particularly among smaller and more specialized producers (Roe, 2001). Feedstocks for composts evaluated on vegetable crops have included mixed municipal solid waste, biosolids, yard trimmings/waste, and other agricultural wastes (Roe, 2001).
The impact of composted soil amendments on chemical parameters of crop quality, rather than simply on crop productivity, has received relatively little attention. Amending the soil with composted red clover (Trifolium pratense L.) affected the content of S-alk(en)yl-L-cysteine sulfoxides in leek (Allium porrum L.) (Lundegårdh et al., 2008). Zhao et al. (2008) reported that organic fertilization (compost + fish emulsion) resulted in higher phenolic concentrations for pak choi (Brassica rapa L. Chinensis group) compared with conventional fertilization with mineral fertilizers. The application of sanitized sewage sludges to pepper (Capsicum annuum L.) plants improved yield without significantly affecting the concentrations of ascorbic acid, glutathione, and capsaicinoids (Pascual et al., 2010).
Pungency is a major determinant of quality in radish (Raphanus sativus L.) storage roots. The pungent principle of radish storage roots was identified by Friis and Kjaer (1966) as a glucoside undergoing rapid enzymatic hydrolysis to 4-methylthio-3-trans-butenyl isothiocyanate, abbreviated MTBITC. There is some evidence that levels of glucosinolates in Brassicaceae vegetables can be influenced by growing conditions. Neil and Bible (1973) reported that MTBITC levels in radish storage roots were influenced by photoperiod and by soil type. Foliar fertilization with methionine, a precursor of glucosinolate synthesis, increased the glucosinolate content in broccoli (Brassica oleracea L. Italica group) heads but not in radish hypocotyls (Scheuner et al., 2005). Pant et al. (2012) found that applications of vermicompost tea increased plant growth, nitrogen (N) content, total carotenoids, and total glucosinolates in pak choi tissues.
The work reported here was part of a larger study designed to compare two unblended organic materials—spent mushroom substrate (SMS) and yard waste compost (YWC), both hereafter referred to as composts—applied to the soil surface at two depths (equivalent to 2.5 or 5 cm) and then incorporated ≈5 to 7 cm deep for effects on field production of multiple cultivars of red radishes. Details of the larger study, including compost analyses, have been published elsewhere (Kahn et al., 2012). The objective of the work reported here was to determine whether the tested compost treatments would affect pungency levels in the radish storage roots, including analyses of possible compost treatment × cultivar interactions.
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