REENA SAINI AND S. R. GUPTA*
Department of Botany, Kurukshetra University, Kurukshetra-136 119 (Haryana), India
*(e-mail : sgupta2002158@gmail.com; Mobile : 09896261253)
(Received : November 26, 2018; Accepted : January 14, 2019)
ABSTRACT
This study was carried out in Populus deltoides agroforestry system at Kurukshetra (20°58″N, 76°51″E, 250 m above mean sea level). The climate of the study area is tropical monsoonal. Seasonal variations in the population of nitrifying bacteria were studied in agroforestry systems of one, two, six and seven-year stage of P. deltoides along with sugarcane and wheat. Viable populations of nitrifiers i. e. ammonium and nitrite oxidizers were estimated by most probable number (MPN) technique. The population size of nitrifying bacteria was related to soil moisture content, inorganic nitrogen and nitrogen mineralization rates. The high values of soil moisture, inorganic-N and N-mineralization could be responsible for the greater population size of ammonia oxidizing and nitrite oxidizing bacteria during the two-year study period. In P. deltoides+sugarcane system, the ammonia oxidizing bacteria (AOB) population varied from 2.40 x 104 to 7.78 x 104/g dry soil and nitrite oxidizing bacteria (NOB) population varied from 1.36 x 104 to 5.81 x 104/g dry soil. In seven-year agroforestry system, the population density of AOB and NOB was 2.1 x 104 to 6.8 x 104 and 1.3 x 104 to 4.83 x 104/g dry soil, respectively. The soil moisture content was found to be positively correlated with the population size of AOB (r2 = 0.65 and r2 =0 .80) and with the population size
of NOB (r2 = 0.39, r2 = 0.41).
Key words : Ammonium, nitrite oxidizers, nitrogen mineralization, MPN