Standardization of Methods for the ?Determination of Available Copper and to Determine the Critical Levels of Copper Using Maize as A Test Crop

Abstract

Pot studies during 1982-83 and 1983-84 were made to study the response of maize to various levels of copper on different fifteen soil series of Peshawar valley. Five methods i.e., 0.1N HCL, 1N NH40AC, 0.005 MDTPA, Na2-EDTA and 0.075 N acid mixture were tried each year for extraction. The experiments were carried out in glass house of N.W.F.P. agricultural University, Peshawar. Pots were filled with 5 kg of soil of each series and the individual experiments on each soil series were arranged in R.C.B design with four replications and the data analyzed statistically according to combined analysis by allotting main plots to series and sub plots to treatments. Copper treatments were applied each year at the rate of 0, 2.5, 5.0, 7.5 and 10.0 kg/ha, along-with basal doses of 125 kg N and 75 kg P/ha. Crops were harvested after 30 days in 1982-83 and after 21 days in 1983-84. The results obtained on fresh matter and dry matter yield of both year studies revealed that there was no significant response of maize to copper fertilization grown on various soil series of Peshawar valley. In all methods of extraction Na2-EDTA method better as regards the extraction capacity followed by DTPA, HCL, acid mixture and NH4OAC in both years. Sufficiency levels for maize crop in the soil i.e., 0.20, 0.15, 0.10, 0.47, 0.20 and 0.09 ppm extractable DTPA, 0.1 N HCL, Acid mixture, Na2-EDTA and 1N NH4OAC were suggested, respectively. Copper content of plants showed that there was an increase in the copper content of plants over control in some soil series in the 1st year while a corresponding increase in all soil series over control was noted in 2nd year. Critical level could not be determined due to lack of response of maize to copper. However, response study to copper by maize plant indicated that HCL and acid mixture extractants are better co-related as compared to the extractants in soil conditions of Peshawar valley. It could be concluded from the results of two years study that the available copper content in soils of Peshawar valley was sufficient for normal growth of plants and these soils do not need copper fertilization. It was also noted that the correct balance of different micronutrients must be scrupulously respected because of strong interactions and antagonism between them.