LONG- TERM TILLAGE AND MANURE EFFECTS ON SOIL PHYSICAL AND CHEMICAL PROPERTIES AND CARBON AND NITROGEN MINERALIZATION POTENTIALS

The objective of this work was to study the effects of tillage and liquid manure applications on some physical and chemical properties as well as on the carbon and nitrogen mineralization potential of a meadow soil. Our results indicated that tillage and manure applications had no effect on the concentration of Cu, Mn, total N and organic C in 0-15 cm layer of soil after 15 years of treatment. However soil P, Ca, Mg and Zn contents significantly increased with manure applications. Soil organic matter and total N significantly decreased in a 15-30 cm depth. No significant change was detected in soil structural stability in any of the layers. Moreover, tillage affected soil soluble C and the C/N ratio significantly. Application of 100 t ha-1 manure significantly increased soil soluble C. The results of this study suggest that tillage increased the soil N mineralization rate significantly. The potentially mineralizable nitrogen (N0) was higher in tilled than in no-tilled soil and was at its maximum in the 0-15 cm layer. Furthermore, a significant positive interaction was observed between tillage and manure application on mineralized N after 1.4 wk (Ne). No significant change was detected in C mineralization rate (Cm) and potentially mineralizable C (C0). The total amounts of mineralizable carbon (Cm) and nitrogen (Nm) significantly decreased in 15-30 cm depth and were very closely correlated with the total amounts of C or N and mineralization rate constants (K).