ACCUMULATION OF HEAVY METALS UNDER INTENSIVE CROPPING WITH LONG TERM FERTILIZER APPLICATION IN CALCAREOUS VERTIC USTOCREPTS SOILS
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Date
2012-07
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jau,junagadh
Abstract
ABSTRACT
Farmers use very large amounts of fertilizers to obtain maximum yield for relatively high economic value of the extra yields and difficulties in the accurate management of fertilizer application. At present, overuse of fertilizers in agriculture contributes to environmental deterioration of great concern nationally and internationally. Fertilizer application rate in agricultural area have increased dramatically in last two decades. Based on interview with farmers and the information available at different agricultural centers of Saurashtra region, the application of fertilizers in this area is more than land requirements of different crops, which can result in long run the high amount of heavy metals accumulation in the soil. Since the soils are calcareous in nature the various pools of heavy metals and its availability in are not clearly understood. Keeping this in mind, a long term fertilizer experiment (LTFE) was started in the year 1999 at Instructional Farm, College of Agriculture, Junagadh Agricultural University at Junagadh to know the effect of continuous application of fertilizers (0, 50, 100 and 150 % recommended dose of N, P, K with and without Rhizobium and PSM) and manure (FYM @ 10 and 25 t/ha) on accumulation of heavy metals under groundnut-wheat sequence. After harvesting of wheat crop, the soil samples were drawn periodically at the interval of 1st, 4th, 8th and 12th years and analysed for Cu, Mn, Zn, Fe, Cd, Cr, Ni and Pb.
The results revealed that the application of FYM and fertilizer significantly increased groundnut pod and haulm yield over control. The significantly highest groundnut pod and haulm yield were recorded after 8th and 12th years with the application of 50 % NPK of recommended dose of G’nut + FYM @ 10 t ha-1 to groundnut crop. While, the grain and straw yield of wheat crop were significantly observed higher with the application of 100% NPK recommended dose at all the four years (1st, 4th, 8th and 12th years).
The DTPA available Cu significantly increased with FYM and fertilizer at 4th, 8th and 12th years after harvesting of wheat crop. The pooled analysis indicated that highest DTPA available Cu was recorded with FYM @ 25 t ha-1 to G’nut over control. Similar trend was also observed in the case of DTPA available Mn.
The application of FYM @ 25 t ha-1 significantly improved Zn content after 8th and 12th years over control. While, in case of the DTPA available Fe after 8th and 12th years were recorded highest with the application of 100 % NPK of recommended doses in G’nut-wheat sequence.
Among the different heavy metals, DTPA available Cd, Cr, Ni and Pb were significantly highest recorded with the application of 100 % NPK of recommended doses in G’nut-wheat sequence (P as SSP) at all the four years. Similar trend was also observed in case of all the heavy metals in pooled analysis after harvesting of wheat crop at 12th year.
The Y x T interaction effect of Cu, Zn, Fe and Cr was observed significant in pooled analysis after 12th years harvesting of wheat crop. The Y x T interaction effect clearly indicated that the continuous cropping (G’nut-wheat sequence) with and without fertilizer treatments after a span of 12 years, the accumulation of Fe, Zn, Mn, Cd, Pb, Ni and Cr were increased 136%, 42%, 23%, 39%, 35%, 32% and 24%, respectively over initial year of the experimentation. While, the Cu was decreased from its initial value of 1.387 ppm to 1.030 ppm. Moreover, these results clearly showed that the application of FYM with fertilizer increased availability of Fe and Zn in the soil and above the maximum permissible limit. While, the Zn, Cd, Cr, Ni and Pb were observed under the permissible limit.
Correlation analysis showed that groundnut pod and haulm yield have significant positive relationship with available Cu, Fe, Cd, Ni, and Cr. The wheat grain and straw yield have significant positive relationship with available Mn, Zn, Fe, Cr, Pb and Ni. The correlation of two heavy metals in pooled analysis showed significant positive relationship between (Cd-Cr), (Cd-Fe), (Cd-Mn), (Cd-Zn), (Cr-Fe), (Cr-Mn), (Cr-Zn), (Ni-Pb), (Ni-Fe), (Cu-Mn) and (Cu-Fe). The regression analysis revealed that DTPA available Cu influenced only groundnut pod yield. While, DTPA available Cr influenced grain and straw yield of wheat and also haulm yield of groundnut crop to the maximum extent.
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Chemistry