Indian Journal of Science and Technology

Abstract

Information on soil zinc (Zn) distribution is essential for understanding its chemical reactions and bioavailability. A study was conducted on the distribution of different forms of soil Zn and response of maize to native soil Zn content at four locations (L1 , L2 , L3 and L4 ) having very low, low, medium and high soil available Zn status. The results revealed that various chemical pools of Zn under incubation condition treated with graded levels of Zn fertilizer application (0, 1.25, 2.50, 5.0, 7.5, 10.0 Zn as ZnSO4 kg ha-1) showed significant variation in almost all the locations and similar trends were noticed for all the soil studied, where the highest amount of added Zn (10 kg Zn ha-1) always produced greater Zn release than the lower doses. Among the fractions, the higher release of water soluble plus exchangeable zinc (WSEX-Zn), organically bound zinc (OM- Zn) and crystalline bound zinc (CFeOX-Zn) were observed at 15 days after incubation(DAI) and gradually declined at the end of the experiment upto 30DAI whereas other forms such as manganese oxide bound zinc (MNOX- Zn), amorphous sesquioxide bound zinc (AFeOX- Zn), residual zinc (RES- Zn) and TOTAL- Zn showed a prolonged release upto 30 DAI.Also from the study it is evident that the content of different fractions varied between the soils of all locations, the order of preponderance of different zinc fractions viz. WS and EX < OM < AFe-OX < CFe-OX) < MN-OX < RES and it remained same for all the locations. More than 95 % of the total Zn content occurred in the relatively inactive and mineral-bound residual form (RES), whereas only a small fraction occurred in WS and EX, OM, AFe-OX, and CFe-OX fractions. The pot culture experiment conducted with similar set of treatments with maize crop responded well to Zn fertilizer application and the location with very low Zn status with 7.50 kg Zn ha-1 showed higher value for the dry matter production (76.4 g plant-1) and Zn – uptake (3.34 mg plant-1). Correlation data indicated that those fractions are in a state of dynamic equilibrium among different fractions and were influenced by pH, EC, CEC, organic carbon, DTPA- Zn and also revealed that almost all the fractions contributed to the plant availability. In all the cases it is noted that the release of various forms of Zn and response of maize crop to Zn fertilizer application always higher for the soil having very low Zn followed by low, medium and high Zn status. 

Keywords: Dry Matter, Chemical Pools, Maize, Soil Properties, Zinc, Zinc Uptake, Zn Levels