夏玉米生长期土壤氮素的硝化-反硝化作用研究

Study on nitrification-denitrification of soil nitrogen in summer maize season

对北京褐土夏玉米生长期氮素硝化 -反硝化作用进行了研究。结果表明 ,氮肥施用后硝化作用在一周内完成。三叶期施肥后土壤干旱 ,反硝化损失氮量相对较低 ,随后由于土壤水分状况的改善而增强。十叶期追肥后半个月内土壤反硝化作用最强 ,是反硝化损失关键阶段 ,并且随着施氮量增加土壤反硝化作用表现出增强趋势。在玉米全生育期表层 (15 cm)土壤氮素反硝化值分别为 14 2 2 .2 g/ hm2 (不施氮处理 )、3812 .4 g/ hm2 (施氮量 12 0kg/ hm2 )、4 6 35 .4 g/ hm2 (施氮量 36 0 kg/ hm2 )。在玉米生育期反硝化作用主要是受到水分供应状况的制约 。

Nitrification denitrification is an important way causing nitrogen loss from arable soil. A field experiment studying nitrification-denitrification was carried out in 1999 in Beijing cinnamon soil. Acetylene inhibition method was introduced to measure denitrification in a soil core incubation system. Urea-N was applied at 0, 120 and 360 kg/hm\+2 separately, among which 1/2 was applied as the third leaf stage topdressing fertilizer and another 1/2 as the tenth leaf stage topdressing fertilizer. The results showed that nitrification completed within a week after fertilizer nitrogen application. After the third leaf stage topdressing denitrification N loss was lower in the earlier stage than later due to soil drought. Highest denitrification occurred immediately after the tenth leaf stage topdressing, and increased fertilizer nitrogen application resulted in higher denitrification. The total denitrification N loss was 1 422.2 g/hm 2, 3 812.4 g/hm 2 and 4 635.4 g/hm 2 for fertilizer nitrogen treatment 0, 120 and 360 kg/hm 2 respectively. Main factor affecting denitrification was soil water filled pore space (WFPS) in whole growth period while soil temperature was possibly the key factor limiting denitrification at the later growth stage.