title: Effect of Azadirachta indica (neem), sodium thiosulphate and calcium chloride on changes in nitrogen transformations and inhibition of nitrification in soil incubated under laboratory conditions.
abstract: A laboratory experiment was conducted to examine the effects of nitrification inhibitors (NIs) neem seed-cake (Azadirachta indica) (NSC), sodium thiosulphate (Na₂S₂O₃) and calcium chloride (CaCl₂) on changes in NH₄(+)⁻N, inhibition of nitrification and recovery of applied nitrogen (N) in soil. Surface soil samples of 0-15 cm were collected from an arable field, amended with urea N (UN) at the rate 200 mg N kg⁻¹, UN+NSC, UN+Na₂S₂O₃ and UN+CaCl₂ and incubated at 22°C periodically over 50 d. Soil without any amendment was used as check (control). Results indicated that more than 58% of N applied as NH₄⁻ disappeared over a period of 50 d from the soil mineral-N pool. Some of this N (21%) was accumulated as NO₃⁻-N while the remaining N was unaccounted for. Addition of nitrification inhibitors NSC, Na₂S₂O₃, and CaCl₂ resulted in a decrease in the extent of NH₄(+) disappearance by 35%, 44% and 30%, respectively. In the treatment receiving UN alone, 56 mg NO₃⁻-N kg⁻¹ was accumulated over 50 d (maximum 93 mg kg⁻¹) indicated an active nitrification. Application of nitrification inhibitors NSC, Na₂S₂O₃, and CaCl₂ with UN inhibited nitrification by 54%, 64%, and 59%, respectively. Apparent N recovery (ANR) in the treatment receiving UN alone was 63% that substantially increased to 83%, 89% and 76% in the treatments receiving UN+NSC, UN+Na₂S₂O₃, and UN+CaCl₂, respectively indicating 32%, 41% and 20% increase in N recovery. Among three NIs tested, Na₂S₂O₃ proved superior in inhibiting nitrification and increasing ANR. The study demonstrated that application of NSC, Na₂S₂O₃, and CaCl₂ which are cheap and easily available NIs inhibited nitrification and improved N recovery efficiency of applied N in an arable soil very effectively. It is suggested that these inhibitors should be tested under field conditions for increasing NUE and improving crop productivity.
authors.affiliation: Department of Soil and Environmental Sciences, University of Azad Jammu and Kashmir, Faculty of Agriculture, Rawalakot Azad Jammu and Kashmir, Pakistan. kaleemabbasi@yahoo.com
authors.forename: M Kaleem
authors.initials: MK
authors.lastname: Abbasi
authors.forename: Munazza
authors.initials: M
authors.lastname: Hina
authors.forename: Majid Mahmood
authors.initials: MM
authors.lastname: Tahir
mesh_terms: D000641:Ammonia / Q000032:analysis / Q000378:metabolism; D031601:Azadirachta; D001711:Biotransformation / Q000187:drug effects; D002122:Calcium Chloride / Q000633:toxicity*; D005308:Fertilizers / Q000032:analysis; D005989:Glycerides / Q000633:toxicity*; D058465:Nitrification / Q000187:drug effects*; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000032:analysis / Q000378:metabolism; D013729:Terpenes / Q000633:toxicity*; D013885:Thiosulfates / Q000633:toxicity*
chemical_list: D005308:Fertilizers; D005989:Glycerides; D012987:Soil; D012989:Soil Pollutants; D013729:Terpenes; D013885:Thiosulfates; C002443:neem oil; D000641:Ammonia; C017717:sodium thiosulfate; D002122:Calcium Chloride; D009584:Nitrogen