Influence of Cadmium on Paprika Chilli ( Capsicum annum ) and its Detoxification by Organic Amendments

A pot culture experiment was conducted in Dept of Soil Science & Agriculture Chemistry during 2010 to study the effect of farm yard manure (FYM) and poultry manure (PM) on detoxification of Cadmium in alfisol with Capsicum annum (cv. Kt-PI-19) as a test crop. The experiment was carried out with 24 treatment combinations (eight levels of Cd 0, 2.5, 5.0, 10.0, 20.0, 40.0, 80.0 and 160.0 mg kg -1 soil and three levels of organic manure; (control, FYM and PM @ 5 t ha -1 ) with three replications in split plot design. With the application of organic matter, dry matter yield was increased at different levels of Cd application (5.97 to 17.2 g pot -1 in FYM and 5.34 to 17.63 g pot -1 in PM treatment, respectively). Cd content in shoot was 2.1 ppm in control and increased to 209.90 ppm at 160 ppm of Cd application. The Cd content was 2.6 and 4.3 ppm in FYM and PM treatment and increased to 133.60 and 111.4 ppm, respectively with the application of 160 ppm of Cd. The organic amendments by chelating organic complexes reduce the phytotoxicity activity which retards the availability of Cd from soil to plant. There was also detoxification of Cd content in post harvest soil samples.

Cadmium (Cd), a non essential element in plant nutrition, is readily taken up by roots and distributed throughout the plant. Accumulation of heavy metal resulted in phytotoxicity to plants or even transfer to food chain. The plant growth and biomass yield is affected at higher concentration (Chang, A.C et. al. 1982). Increasing use of industrial effluent and municipality sewage on agricultural land not only increased nutrient status and organic matter but also the heavy metal content of the soil. Continuous use of sewage, sludge and industrial effluents on agricultural land reported to increase the levels of trace metals (Rattan R.K. et.al. 2003). It needs attention to alleviate the metal content by using organic manure. Significant decrease in phytoavailability of metals was obtained upon addition of organic manure (Karapanagiotis et al. 1991) . On the contrary, increases in solubility of metal in soil amended with organic manure were reported by other workers (Narwal R.P. andSingh B.R. 1998, Shuman L.M. 1998). With these views, a pot culture experiment was laid out to study the effect of Cd on biomass yield of paparika chilly (Capsicum annum cv.  in alfisol, its accumulation on plant and to detoxify Cd content by using organic amendments.

Materials and Methods
A pot experiment was conducted during 2010 rabi with 24 treatment combinations; eight levels of Cd (i.e.) 0, 2.5, 5.0, 10.0, 20.0, 40.0, 80.0, 160.0 mg Kg-1 soil and three levels of organic manure (OM) (i.e.) Control, farm yard manure (FYM) @ 5 t ha-1 and poultry manure (PM) @ 5 t ha-1 with three replications in split plot design. Capsicum was grown in rabi season. The soil used for the study was sandy loam in texture, pH 5.6, EC 0.42 dS m-1 and organic carbon 0.42%. The soil was low in available N but medium in available K. The DTPA extractable Fe, Zn and Cd were 116, 0.43, and 0.033 mg Kg-1 respectively.
Ten kg of air dried soil was filled in earthen pots. The crop received N: P2O5: K2O @ 120:60:120 kg ha -1 respectively. Full dose of P2O5 and half dose of K2O and 20% of N were applied at planting and remaining N & K2O were applied after 30 days of transplanting. FYM and PM @ 10 t ha-1 were well mixed with soil before transplanting. The pots were irrigated with deionized water from time to time. Then the seedlings of capsicum were transplanted. The plants were harvested at maximum vegetative stage and the plant shoot biomass was expressed on oven dry basis. The post harvest soils were analyzed for DTPA extractable cadmium. Plant shoots were washed with distilled water and then oven dried and digested with diacid mixture (HNO3::HClO4). The extract was determined with the help of Atomic Absorption Spectrophotometer.

Biomass yield of Capsicum
The oven dry matter yield of capsicum decreased with the increasing levels of Cd. The decrease was   (Table 1). The values ranged from 5.97 to 17.2 g pot -1 and 5.30 to 17.63 g pot -1 in FYM and PM treatment, respectively (Fig 1).

Cadmium content in Shoot
Cadmium accumulation in plants increased significantly with addition of Cd application (Table 2).

Fig. 2. Effect of organic amendments (Farm Yard Manure and Poultry Manure) on per cent detoxification of Cd in Capsicum
Cd content in capsicum shoot was 2.1 ppm at control (Cd0OM0) and increased to 209.90 ppm at 160 ppm of Cd. On the other hand, Cd content in FYM and PM treatment (with Cd0) was 2.6 and 4.5 ppm, respectively. The increase was from 2.6 to 133.60 ppm in FYM treatment and 4.5 to 111.4 ppm in PM treatment, respectively, at 160 ppm of Cd. The organic amendments reduced the phytotoxic acitivity by chelating Cd with the organic manure (Fig 2). Shoot accumulates a major quantity of Cd than fruit (Quadir.M et. al. 2006).

Soil
Cadmium content in post harvest soil is presented in Table 3. The results showed that the application of Cd at higher level, the Cd content of soil increased and it ranged from 0.44 to 59.00 mg ha-1 in control where as it increased from 0.5 to 47.92 and 0.96 to 36.6 mg kg-1 in FYM and PM treated pots, respectively. The results showed that Cd concentration in soil decreased to 38.2% due to addition of organic amendments up to 2.5 ppm of Cd. Thereafter increased in higher doses may be due to chelating effect of organic manures (Table 4).

Conclusion
The study revealed that the addition of Cd decreased the dry matter yield of plant but addition of organic amendment enhanced the dry matter yield.
Cadmium was detoxified in the post harvest soil. It was further detoxified by addition of organic amendments in the form of chelates which ultimately retard the availability of Cd from soil to plants as evidenced from enhanced yield.