Evaluation of Extractants for Determination of Available and Estimation of Critical Limits of Zinc in Tomato Grown Soils of Eastern Dry Zone, Karnataka

摘要

Pot experiment was conducted in the green house of the Department of Soil Science and Agricultural Chemistry, UAS, Bengaluru, Karnataka, India during 2016-17 to determine available zinc and critical limits of zinc in tomato grown soils. The pot experiment consists of five treatments i.e., 0, 5,10,15,20kgZnSO4ha"' with three replications and fifteen locations with completely randomized design with a total number of225 pots. Among all the treatments Rec. NPK + ZnS0_4 @ 20 kg ha~(-1) recorded highest mean dry matter yields of tomato. The amount of zinc extracted by different extractants, were in the following order as Mehlich-3 - Zn > 0.1 N HC1 -Zn>AB-DTPA-Zn>0.01 NEDTA- Zn>DTPA-Zn> 0.01 MEDTA+ 1 NNH_4OAc-Zn> 1 NNH4OAc (pH 4.6) - Zn > 1 N NH4OAc (pH 7)- Zn. Among the various extractants tried, DTPA - Zn gave positive and higher significant correlation with Brays per cent yield (r = 0.781). The next better extractants are Mehlich-3 (r = 0.726) and AB-DTPA (r = 0.576) which are also significantly positively correlated with Brays per cent yield. The critical limits of DTPA, Mehlich-3 and AB-DTPA in graphical methods are 1.12,2.15 and 1.20 ppm while in statistical methods it is 1.16, 2.16 and 1.11 ppm, respectively. For tomato plant and fruit it is 34 and 66 ppm for graphical methods and 32 and 70.5 ppm for statistical method, respectively. The study indicated that tomato growing soils would respond to Zn application, when the soils contains less than 1.12 ppm DTPA extractable Zn.