Fixed ammonium and carbon-nitrogen ratios of some semi-arid tropical Indian soils

• Published in: Geoderma Vol. 68; no. 3; pp. 219 - 224
• Main Author: Sahrawat, K.L.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.10.1995; Elsevier
• Subjects: ammonia; ammoniac; amoniaco; azote; carbon; carbone; carbono; chimie du sol; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geochemistry; inde; india; nitrogen; nitrogeno; quimica del suelo; semiarid zones; Soil and rock geochemistry; soil chemistry; Soils; sol tropical; suelo tropical; Surficial geology; tropical soils; zona semiarida; zone semi aride; Asia; India; Vertisols; geochemical cycle; nitrogen; carbon; soil profiles; Alfisols; ammonium; semi-arid environment; tropical environment; horizons
• ISSN: 0016-7061; 1872-6259
• DOI: 10.1016/0016-7061(95)00031-I

Relatively little is known about the fixed NH4-N status of soils in the semi-arid tropics (SAT) but information is needed in view of its role in N cycling and the N economy of the soils. The distribution of fixed NH4-N and C/N ratios of soil profiles from two benchmark Vertisols and one Alfisol in the Indian SAT were studied. From 15.9 to 58.6% of the total soil N was present as fixed NH4-N in the Vertisol profiles; the range was from 13.3 to 30.8% in the Alfisol profile and a higher percentage of fixed NH4-N was found in the lower horizons. A method based on the extraction of soil samples with dilute HF solution was found suitable for determining fixed NH4-N in these soils as the values of fixed NH4-N determined by this method were in good agreement with those determined using the standard method. Organic C/total N ratios varied from 7.7 to 12.8 in the three profiles while the organic C/organic N ratios varied from 9.4 to 21.4. The results of this study emphasize the importance of fixed NH4-N in assessing the N-status of the soils.