摘要
Field experiments were conducted in a maize (Zea mays L.)field of a calcareous fluvo-aquic soil in North China Plain for studying the fate and ammonia loss of urea-N applied at seedling stage,as well as the effectiveness of coated calcium carbide(CCC) in reducing N loss and in improving the yield efficiency of urea.Results show that:(1) For the surface-broadcast treatment ammonia volatilization (measured with micro-meteorological technique)took place quickly,reached the peak 20-26hr after application,and then declined gradually;the cumulative ammonia loss approached the maximum 188hr after application (30% of the N applied),and increased only to 32% 284 hr after application;the latter accounted for 71% of the total loss (45% of applied N).(2) In the case of point placement at a depth of 5-10 cm,ammonia loss 188hr after application was only 12% of the N applied,accounting for 40% of the total loss.(3) There was no difference in total loss between the application depths of 6cm and 10 cm,the loss of them was 30% and 29%,respectively.(4) Total loss of N applied at lower rate (40kg N/ha)with point deep placement at 6cm depth was found only 4% of the N applied,it rose up to 30% when the rate of application increased to 80kg N/ ha.(5) The nitrification inhibitor,CCC,seemed to enhance N loss of urea rather than reduce it,and did not show any benefit effect in improving the yield efficiency of urea,which is presumably due to the high potential of ammonia volatilization in the soil and climatic conditions under investigation.
Field experiments were conducted in a maize (Zea mays L.) field of a calcareous fluvo-aquic soil in North China Plain for studying the fate and ammonia loss of urea-N applied at seedling stage, as well as the effectiveness of coated calcium carbide (CCC) in reducing N loss and in improving the yield efficiency of urea. Results show that: (1) For the surface-broadcast treatment ammonia volatilization (measured with micro-meteorological technique) took place quickly, reached the peak 20-26 hr after application, and then declined gradually; the cumulative ammonia loss approached the maximum 188 hr after application (30% of the N applied), and increased only to 32% 284 hr after application; the latter accounted for 71 % of the total loss (45% of applied N). (2) In the case of point placement at a depth of 5-10 cm, ammonia loss 188 hr after application was only 12% of the N applied, accounting for 40% of the total loss. (3) There was no difference in total loss between the application depths of 6 cm and 10cm, the loss of them was 30% and 29%, respectively. (4) Total loss of N applied at lower rate (40 kg N/ ha) with point deep placement at 6 cm depth was found only 4% of the N applied, it rose up to 30% when the rate of application increased to 80 kg N / ha. (5) The nitrification inhibitor, CCC, seemed to enhance N loss of urea rather than reduce it, and did not show any benefit effect in improving the yield efficiency of urea, which is presumably due to the high potential of ammonia volatilization in the soil and climatic conditions under investigation.
