Effect of wheat stubble burning and tobacco waste applications on nitrogen mineralization, denitrification and yield in soil under soybean vegetation

ABSTRACT PhD THESIS EFFECT OF WHEAT STUBBLE BURNING AND TOBACCO WASTE APPLICATIONS ON NITROGEN MINERALIZATION, DENITRIFICATTON AND YIELD IN SOIL UNDER SOYBEAN VEGETATION A1İCOŞKAN DEPARTMENT OF SOIL SCIENCE INSTITUTE OF NATURAL AND APPLIED SCIENCES UNIVERSITY OF ÇUKUROVA Supervisor Year Jury ProfDrMustafa GÖK 2004 Pages: 124 ProfDrMustafa GÖK ProfDr.Hayriye İBRİKÇİ Prof Dr.Turan SA?LAMTİMUR ProfDr.ZülküfKAYA ProfDr. Suphi ASLAN A two year field experiment at soybean cultivation was undertaken for determining the effects of stubble burning, a widely performed practice in Çukurova Region, along with admixing tobacco wastes on soils NO"3-N and NH4+-N contents, denitrification losses, biological activity and grain yield. The doses of 0, 500 and 1000 kg da"1 tobacco wastes were applied to stubble burned and non-burned plots. NO"3-N, NH/-N, dehydrogenase and C02 analyses were undertaken on samples taken at certain periods. Moreover, on the day of samplings in-situ denitrification analyses at field were performed via acetylene inhibition technique. Results revealed that applications were significantly effective on soil nitrate and ammonium contents. According to overall averages, the highest nitrate values have been achieved in first year as 3.47 kg da"1 on the plot 1000 kg da waste applied and stubble burned, and in the second year with 9.06 kg da"1 on the 1000 kg da"1 waste applied plot with stubble. The highest ammonium values of 3.13 and 5.01 kg da"1 were determined in the stubble burned plot in the first year, and in the second year highest values were determined in the 1000 kg da"1 tobacco waste applied plots with stubble. There was no significant statistical difference according to the loss of nitrogen via denitrification between the plots with or without stubble burning. In the first year of experiment tobacco waste applications of 500 kg da"1 and 1000 kg da"1 both induced and increased the rate of denitrification. The highest value of 9.79 g N2ON da"1 day"1 was determined at plot with stubble, with 1000 kg da"1 waste. When the rates of tobacco waste applications were compared, no statistically significant results were revealed according to control plot However, the highest loss was achieved in stubble burned and 1000 kg da"1 waste applied plots with 12.00 g N20-N da"1 day"1. At the end of experiment determined grain yield amounts in first year were higher in the stubble burned plots. No statistical difference was determined in second year. When the variants of tobacco waste applications were compared according to their tobacco rates, the productivity was increased at plots of waste application in both years. The highest yield 452 kg da"1 was determined at stubble burned plots in which 1000 kg da"1 waste was applied in the first year, whereas in the second year the highest value was achieved on plot of stubble with 1000kg da"1 waste (528 kg da"1). Key Words: Stubble burning, tobacco waste, denitrification, acetylene inhibition technique, soybean n