Abstract
Recycling animal manure could be explored in agricultural production for growing vegetable crops to reduce dependence on inorganic fertilizers. Arugula (Eruca sative) and mustard (Brassica juncea) were grown in a randomized complete block design (RCBD) under four soil management practices: 1) control (no-mulch untreated soil); 2) sewage sludge; 3) horse manure; and 4) chicken manure. Sewage sludge compost elevated soil urease and invertase activities indicating increased soil microbial activities. Total soil enzyme activities were significantly (P < 0.05) greater in sewage sludge amended soil compared to no-mulch native soil. It could be concluded that sewage sludge and chicken manure increased soil fertility and the activities of soil urease and invertase could be used as an indicator of soil biological activity after addition of soil amendments. This investigation revealed that soil incorporated with sewage sludge or horse manure promoted biomass production of arugula and mustard by 26 and 21%, respectively compared to no-mulch bare soil. Future trends in agricultural production should make a good use of natural resources to reduce dependence on synthetic fertilizers.
Highlights
The use of animal manure as organic fertilizer has important properties that cannot be gained from synthetic inorganic fertilizers
sewage sludge (SS) used in this study was purchased from the Metropolitan Sewer District, Louisville, KY, whereas, chicken manure was obtained from the Department of Animal and Food Sciences, University of Kentucky, Lexington, Kentucky, and horse manure was obtained from Kentucky horse park (Lexington, Kentucky)
Results revealed that horse manure (HM) was a good choice for growing arugula and mustard plants, because it produced the 2nd great biomass production after SS, whereas, the biomass produced from chicken manure (CM) was similar to the no-mulch bare soil
Summary
The use of animal manure as organic fertilizer has important properties that cannot be gained from synthetic inorganic fertilizers. Thirty percent of U.S streams have high levels of N and P contamination and drinking water violations due to nitrates and phosphates (eutrophication) that have been doubled in the last eight years [2] due to over application of inorganic fertilizers. There is a need for affordable sources of organic fertilizers for use as alternative to inorganic synthetic fertilizers. Municipal sewage sludge (SS), a byproduct of sewage treatment plants, is currently applied to some agricultural soils as an alternative to conventional inorganic fertilizers. Fungi, protozoa, and algae present in animal manure release various enzymes, such as ureases, invertases, dehydrogenases, cellulases, amylases, and phosphatase that are primary means of degrading xenobiotics in soil systems, mineralization of organic compounds, and release of nutrients for plant uptake. Soil enzymes are sensitive indicators to environmental stress caused by soil pollution [3]. Soil enzymatic measurements could be explored as indicators of soil health and biological processes when animal manure is used as fertilizer
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