Acknowledgements

soil (soil origin)? Or this increase might be due to increased soil organic matter and microbial activity. Based on the results in Figures 9 and 10, plants grown in NM bare soil (control plants) contained the lowest concentrations of the two phytochemicals (vitamin C and phenols) compared to the plants grown in animal manure amended soils. Therefore, the native soil used in this study is not the source of these three compounds. SS, CM, and HM contain many enzyme substrates such as urea, sucrose, and phosphates compounds that activate soil enzymes, such as urease, invertase, and phosphatase, respectively. Accordingly, the pronounced differences in vitamin C and phenols concentrations found among tomato fruits of plants grown under the different soil amendments tested could be attributed to increased microbial activity and the enzymes they produce. Many reasons have been suggested for this variability, but none of them have been extensively investigated. In either way, the use of animal manure such as municipal waste compost is an economic way to recover nutrients, reduce dependence on inorganic fertilizers, reduce dunghill areas of disposal, and eliminate

3.3. Impact of agricultural waste on soil enzymes (urease and invertase) activity

Animal manures used as organic soil amendments protect soil microorganisms, soil biological processes, improve soil quality, and increase agricultural productivity [72]. There are three enzymes in soil play a significant role in the N, C, and P cycles. These three enzymes are, urease (urea amidohydrolase, EC 3.5.1.5) is the enzyme that catalyzes the hydrolysis of urea to

its organic form into inorganic N by hydrolysis of urea or organic forms of N into ammonia. Invertase (β-D-fructofuranosidase) is ubiquitous enzyme in soils. The activity of these two soil enzymes (urease and invertase) in soil is responsible for the release of C and N needed for the growth and proliferation of soil microorganisms and the enzymes they produce. Phosphatases, a group of enzymes that catalyze the hydrolysis of esters and anhydrides of phosphoric acid

Figure 12. Urease activity expressed as μg NH4–N released g<sup>1</sup> dry soil. Statistical comparisons were carried out among soil management practices using SAS procedure. Values accompanied by the same letter are not significantly (P > 0.05)

) ions. Urease breaks-down and converts N from

+

unpleasant smell [71].

60 Agricultural Waste and Residues

carbon dioxide (CO2) and ammonium (NH4

different. Each value is an average of three replicates std. error.

The author would like to thank Steven Diver, Eric Turley, and the University of Kentucky farm crew for their assistance in growing tomato under field conditions. This investigation was supported by a USDA/NIFA Award No. KYX-10-13-48P to Kentucky State University.
