Division of soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 110012.
*Corresponding author: e-mail samar1953@yahoo.com.
The aim of this investigation was to study the kinetics of Zn release by 100 ppm tartaric acid from clay-humus complex (CHC) and humus free clay (HFC) from different layers of two nearby profiles of a Typic Ustipsament at Ludhiana, India where rice-wheat and maize wheat cropping are being practiced for quite a long time. Release of zinc (Q) with time, t, was found to be closely fitted to Elovich equation of the form, Q= 1/blnt +1/bln (ab), where, a and b are constants. The coefficient, a which is a measure of the initial rate of release and b, a coefficient reducing the initial rate were combined as a/b and termed as Zn extractability of a sample independent of its total Zn content. On an average Zn extractability of CHC was more in case of maize-wheat cropping system (MWCS) than rice-wheat cropping system (RWCS). It was maximum at 30–45 cm and 7.5–15 cm for RWCS and MWCS, respectively. On an average, the HFC samples also had more extractability than CHC samples but specifically on partial removal of adsorbed humus by H2O2, (decomposition product were not being washed out), Zn extractability decreased in 0–7.5 cm for both the layers and in 30-45cm in case of RWCS and 7.5 –15 cm incase of MWCS.
