Abstract
Soil enzymes (urease, invertase, acid and alkaline phosphatase) activity in the rhizosphere of field-grown tomato plants were used to monitor the impact of soil amendments (SA) and SA mixed with biochar on soil microbial activity four months after addition of amendments. The soil treatments were sewage sludge (SS); horse manure (HM); chicken manure (CM); vermicompost (worm castings); commercial inorganic fertilizer; commercial organic fertilizer; and no-mulch (NM) native soil used for comparison purposes. Soil treatments also were mixed with 10% (w/w) biochar to investigate the impact of biochar on soil enzymes activity. The results showed a significant increase in soil urease and invertase activities after incorporation of SA to native soil. Vermicompost and HM were superior in increasing urease and invertase activity four months after their addition to native soil. Alkaline phosphatase activity fluctuated among the soil treatments, revealing some obstruction of its activity. SS amended with biochar increased acid phosphatase activity by 115% four months after SS addition. Other than alkaline phosphatase, organic manure enhanced soil biological activity (microbial biomass and release of enzymes), indicating that the use of manures, rather than inorganic fertilizers, in crop production is an affordable and sustainable agricultural production system.
Highlights
Soil quality is a combination of chemical, physical, and biological characteristics that enable soils to perform a wide range of functions
As more sewage sludge (SS) treatment districts turn to composting as a means of sludge maintenance, and because of the rapid growth in chicken manure (CM) production, SS and CM will be available in rising quantities
Urease activity in soil increased 2.2 times in horse manure (HM)-amended soil, 3.4 times in CM-amended NM soil, 7 times in SS-amended soil, and about 88 times increase in vermicompost-amended soil, four months after the addition of amendments
Summary
Soil quality is a combination of chemical, physical, and biological characteristics that enable soils to perform a wide range of functions It is dependent on soil biology, in which microorganisms play energetic parts in soil fertility and crop production through enzymatic activity, organic matter decomposition, and nutrient cycling. As more sewage sludge (SS) treatment districts turn to composting as a means of sludge maintenance, and because of the rapid growth in chicken manure (CM) production, SS and CM will be available in rising quantities Recycling wastes such as SS and CM for use as low-cost organic fertilizer could result in a positive effect on the growth and yield of a wide variety of crops and promote the restoration of ecologic and economic functions of soil
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