Abstract:

To explore the changing law of soil invertase activity and the response to different nitrogen levels after returning straw to field, the test adopted a split zone test design with two factors of no straw and straw buried deep, and each factor had 4 nitrogen levels (0, 135, 180 and 225 kg/hm²). The results indicated that the soil invertase activity showed a trend of first increasing and then decreasing with the extension of the corn growth period, reached the highest in the jointing stage, gradually decreased in the harvest period, and reached the lowest in the harvesting stage. Compared with the no straw returning treatment, the straw buried deep treatment could significantly increase the soil invertase activity, and with the increase of nitrogen fertilizer level, it could significantly increase the soil invertase activity (P<0.01), when nitrogen application level was 180 kg/hm², the activity of soil invertase reached the highest value, which was 329.09 mg/(g·24 h), and the increase rate was up to 19.83%. Adding nitrogen fertilizer under the straw buried deep treatment could increase the content of soil organic matter. The amount of soil organic matter reached the highest level of 37.08 g/kg at the fertilizer application level of 180 kg/hm². Through correlation analysis, it concluded that the interaction between straw buried deep and nitrogen application level had a significantly positive correlation with organic matter content and soil invertase activity, and soil invertase activity had the possibility of reflecting the dynamic changes of soil organic matter content. Therefore, the straw buried deep has beneficial effect on the content of soil invertase, and the activity of soil invertase could be used as one of the nutrient indexes to characterize the content of soil organic matter.

Key words: straw buried deep, nitrogen fertilizer level, corn stalk, soil enzyme, soil invertase, soil organic matter