CHEMICAL FERTILIZATION AND ORGANIC AMENDMENTS IMPACT ON SOIL BIOLOGICAL, CHEMICAL PROPERTIES AND CARBON, NITROGEN LABILITY

Abstract

Soil organic matter (SOM) management to sustain soil quality requires integrated management practices, The goal of our study was to evaluate the long-term (1996 to 2012) effects of annual chemical fertilization and various organic amendments on soil biological and chemical properties and lability of carbon and nitrogen as indicator of SOM management. Treatments including the control, chemical fertilization, compost, cow manure, and mycorrhizal inoculated compost amendments were established for a corn (Zea mays L.) - wheat (Triticum aestivum L.) rotation in a randomized complete block design. Composite soils were randomly collected from 0 to 20 cm depth and analyzed for soil biological and chemical proporties. Besides, carbon and nitrogen lability as well as management indices were calculated from measured carbon and nitrogen fractions. Results showed that both compost and cow manure amendments significantly increased total microbial biomass (by 1.8 to 2.2 fold), basal respiration (by 1.3 to 1.9 fold), potentially mineralizable carbon (by 1.1 to 1.4 fold). total organic carbon (6 to 11%), oxidizable carbon (28 to 33%), particulate organic cation (4.2 to 4.5 fold), soluble carbon (1.3 to 1.7 fold), extractable carbon (1,7 to 1.9 fold), total nitrogen (10 to 12%), available nitrogen (2.8 fold), and PON (4.5 to 4.7 fold) with a significant decrease in qCO(2) (20 to 23%), as compared with the control, Moreover, both compost- and cow manure-amended soils had significantly higher values of basal respiration, soluble carbon, extractable carbon, oxidizable carbon, particulate organic cabon, and particulate organic nitrogen than the chemically fertilized soils. The POC and PON lability and management indices consistently accounted and predicted the management induced qualitative and quantitative changes in TOC and TN, over other C and N fractions.