**3. Organic farming and the market for organically produced food**

Consumer concern, over high levels of saturated fats, sugar and salt in food, as well as the risks from food additives and synthetic pesticide residues, has stimulated the demand for healthy food and led to significant changes in the food sector, including the active promotion of additive‐free foods. These concerns have contributed to the development of the market for organically produced food that uses organic fertilizers. The development of the market for organically produced food has been largely consumer led. As a result, organic farming became one of the fastest growing segments of US agriculture since 1990s; producers, exports, and retailers are still struggling to meet consumer demand for a wide range of organic products. Organic farming, the use of organic fertilizers and organic pesticides, is increasingly being recognized as a potential solution to many of the policy problems facing agriculture in both developed and developing countries and has become an established part of the farming scene.

During the past 15 years, field studies were conducted at Kentucky State University (KSU) Research Farm (Franklin County, KY, USA) on a Lowell silty‐loam soil (2.2% organic matter, pH 6.7) to study the impact of manure (SS and CM) and YW on chemical composition of treated crops, crop yield, and quality. Eighteen (18) standard plots 22 × 3.7 m each were established, and the field study area was a randomized complete block design with three replicates for each of the three tested soil management practices tested (SS, CM, and no‐mulch treatments). The soil in six plots in this design was mixed with SS from the Metropolitan Sewer District, Louisville, KY (**Figure 1**) at 15 t acre-1 on dry weight basis.

**Figure 1.** Sewage sludge granules obtained from the Metropolitan Sewer District, Louisville, KY, USA.

Six plots were mixed with CM obtained from the Department of Animal and Food Sciences (**Figure 2**), University of Kentucky, Lexington, Kentucky, at 15 t acre-1 on dry weight basis, and six plots were used for comparison purposes. The plots were transplanted with collard seedlings (*Brassica oleracea* cv. Top Bunch) of 45 days old. Results revealed that soil incorpo‐ rated with SS increased soil myrosinase activity compared to soil incorporated with CM and no‐mulch native soil. Across all treatments, SS and CM increased soil organic matter content from 2.2% in native soil to 4.2 and 6.5%, respectively. The greater soil urease and invertase activities in soil amended with SS provided evidence of increased soil microbial population (data not shown).

food and led to significant changes in the food sector, including the active promotion of additive‐free foods. These concerns have contributed to the development of the market for organically produced food that uses organic fertilizers. The development of the market for organically produced food has been largely consumer led. As a result, organic farming became one of the fastest growing segments of US agriculture since 1990s; producers, exports, and retailers are still struggling to meet consumer demand for a wide range of organic products. Organic farming, the use of organic fertilizers and organic pesticides, is increasingly being recognized as a potential solution to many of the policy problems facing agriculture in both developed and developing countries and has become an established part of the farming scene.

During the past 15 years, field studies were conducted at Kentucky State University (KSU) Research Farm (Franklin County, KY, USA) on a Lowell silty‐loam soil (2.2% organic matter, pH 6.7) to study the impact of manure (SS and CM) and YW on chemical composition of treated crops, crop yield, and quality. Eighteen (18) standard plots 22 × 3.7 m each were established, and the field study area was a randomized complete block design with three replicates for each of the three tested soil management practices tested (SS, CM, and no‐mulch treatments). The soil in six plots in this design was mixed with SS from the Metropolitan Sewer District,

**Figure 1.** Sewage sludge granules obtained from the Metropolitan Sewer District, Louisville, KY, USA.

Six plots were mixed with CM obtained from the Department of Animal and Food Sciences (**Figure 2**), University of Kentucky, Lexington, Kentucky, at 15 t acre-1 on dry weight basis, and

Louisville, KY (**Figure 1**) at 15 t acre-1 on dry weight basis.

160 Organic Fertilizers - From Basic Concepts to Applied Outcomes

**Figure 2.** Chicken manure obtained from the Department of Animal and Food Sciences, University of Kentucky, Lex‐ ington, Kentucky, USA.

In summer 2015, a field trial was conducted at the University of Kentucky South Farm (Lexington, KY). Arugula (*Eruca sativa*) and mustard (*Brassica juncea*) were grown in 30' × 144' beds of freshly tilled soil. Each bed, measuring 12' × 30', was divided into three replicates in a randomized complete block design (RCBD) with four soil treatments. The entire study area contained 24 plots (2 crops × 3 replicates × 4 treatments). The treatments were (1) SS amended with soil, (2) CM amended with soil, (3) horse manure (HM, **Figure 3**) amended with soil, each at 15 t acre-1, and (4) no‐mulch bare soil used for comparison purposes. The results in **Table 1** revealed that soil amended with SS increased plant biomass production in arugula and mustard by 26 and 21%, respectively, compared to no‐mulch (NM) native bare soil [24].

**Figure 3.** Horse manure obtained from Kentucky horse park, College of Agriculture, University of Kentucky, Lexing‐ ton, Kentucky, USA.



Statistical comparisons were carried out among soil amendments for each parameter tested. Each value is an average of three replicates.

Knowledge about the environmental problems and adoption of appropriate solutions and **Table 1.** Mean weights of arugula and mustard plants grown under four soil management practices. practices to enhance and protect soil quality require timely delivery of research and educa‐ tional technology. Attempts to improve the efficiency of biofumigation have focused on se‐ lection of biofumigant crops with high glucosinolates (GSLs) content [26]. The use of soil amendments might reduce the biomass needed to produce significant concentrations of iso‐ thiocyanate (ITCs) generating GSLs in Brassica plants for greater biofumigant potential. Soil‐ borne organisms are becoming more difficult to control due to pathogen resistance and restricted use of some pesticides. Brassica species produce a significant amount of GSLs in their tissue. When GSLs are hydrolyzed by the enzyme myrosinase which is also present in the Brassica plant tissues, a range of products are produced which include the volatile bioci‐ dal ITCs that is similar to the active ingredient in the nematicide, metam sodium (Vapam). New soil management practices are needed to develop and expand our knowledge and technical means of agricultural production systems related to GSLs and plant protection. The problems of soil deterioration and erosion associated with intensive farming systems and the use of synthetic pesticides have generated considerable interest in less expensive and more environmentally compatible production alternatives such as recycling wastes from several processing operations for use as fertilizers in land farming to provide high‐ quality organic amendments. Approximately 41,511 water body impairments across the US are attributed to synthetic pesticides and of that total 1300 water body impairments are only from the state of Kentucky [27]. Brassica plants (such as mustard and arugula) have been shown to release biotoxic compounds (GSLs) or metabolic by‐products against bacteria, fun‐ gi, insects, nematodes, and weeds. When plants containing GSLs are physically disrupted, the hydrolytic enzyme myrosinase is released from ruptured cells, hydrolyzing GSLs pri‐ marily to ITCs, glucose, and nitrile products. Incorporation of allelopathic Brassica tissues, such as mustard and arugula, into soil suppresses soil‐borne pests due to the biofumigant properties of the highly toxic ITCs, and moderately toxic non‐glucosinolate S‐containing compounds [28]. ITCs, physiologically active compounds, are the major products of hydrol‐ ysis of GSLs that are released when myrosinase (thioglucosidase), a degradative enzyme, comes into contact with GSLs in plant damaged tissues. This technology could be explored in organic agriculture as alternative to synthetic fungicides.
