Effects of fertilization on soil enzyme activities of arable black soil profiles under soybean-maize rotation system

The impact of fertilizer regimes on soil catalase, invertase and urease activities of arable black soil profiles under soybean-maize rotation systems in Heilongjiang province was studied.Four different fertilizer treatments were established in 2011 with NoF(no fertilizer), CF(chemical fertilizers), CF+M(chemical fertilizers plus maunre) and CF+2M(chemical fertilizers plus double maunre).The results showed that the catalase activities declined from the soil surface to the deeper soil layers.The applied fertilizer reduced the catalase activities regardless the soil layers.CF had the lowest catalase activities, while CF+M and CF+2M alleviated the inhibition effect of CF on catalase activities in the soil layer of 0-20 cm, but there were no significant differences between CF+M and CF+2M.The invertase activities also declined from the soil surface to the deeper soil layers.Although in the soil layer of 0-30 cm, the fertilizer treatments had higher invertase activities compared with NoF, the effect of CF+2M on the increase of invertase activities was less than CF+M, which indicated that the application of chemical fertilizers plus suitable manure could balance the soil nutrient and effectively increases invertase activities.The urease activities showed a "A" distribution in the soil profile, with the urease activities increased from the soil layer 0-40 cm, then decreased after that and finally reached the lowest values at the soil layer 70-80 cm.In the soil layer of 0-20 cm, the urease activities among the four treatments showed the order as:CF+2M>CF+M>CF>NoF, while in the soil layer of 20-80 cm, the effect of fertilizer on soil urease activities was not obvious.