Effect of different rates of compost and phosphate fertilizer on the accumulation of Cadmium in kalmi (Ipomoea aquatica) and red amaranthus (Amaranthus cruentus)

Shamim Al Mamuna, N. Sultanaa, M. Hasana, M. Aktara and T.R. Tusherab

aDepartment of Environmental Science and Resource Management, Mawlana Bhashani Science and Technology University, Bangladesh

bGraduate School of Environmental Studies, Tohoku University, Japan

shamim084du@yahoo.com

Cadmium (Cd), a non essential trace element, is found in elevated concentrations in soils due to Cd containing phosphate fertilizer application and industrial waste discharge. In Bangladesh, the daily intake of Cd exceeds the guideline values as the market rice and vegetables were reported containing high concentration of Cd. We aimed to find out the concentration of Cd in soils of Bangladesh and the effect of different rates of compost, phosphate fertilizer and their combinations on the transfer of Cd from soil to kalmi (Ipomoea aquatica) and red amaranthus (Amaranthus cruentus) and the growth of the plants in pot trial. We selected 330 locations from 3 disdtricts of Bangladesh and collected top soil (0-15.0) cm and sub soil (15.0-30.0 cm) samples from each point. The soil Cd concentrations ranged from 0.97 mg/kg to 3.7 mg/kg in top soil (0-15 cm) and 0.96 mg/kg to 3.6 mg/kg in sub soil (15-30 cm). We used soils in the pot trial that had Cd concentration of 1.2 ppm which were collected from an agricultural land. In pot trial, the treatments were control, compost 1 t/ha, compost 5 t/ha, compost 10 t/ha, TSP 40 kg/ha, TSP 60 kg/ha, TSP 80 kg/ha, compost 1t/ha + TSP 40 kg/ha, compost 5t/ha + TSP 40 kg/ha, compost 10t/ha + TSP 40 kg/ha, compost 1t/ha + TSP 60 kg/ha, compost 5t/ha + TSP 60 kg/ha, compost 10t/ha + TSP 60 kg/ha, compost 1t/ha + TSP 80 kg/ha, compost 5t/ha + TSP 80 kg/ha and compost 10t/ha + TSP 80 kg/ha. After bringing the soils from 0-30 cm depth, the soils were mixed throughly, put in to 4 kg plastic pots, treatments (d.w.) were added (w/w), mixed properly and 500 ml water/pot was added daily for 15 days. Then the seeds of kalmi (Ipomoea aquatica) and red amaranthus (Amaranthus cruentus) were sown. After germination the plants were kept in a net house following a randomised block design and allowed to grow for four (4) weeks. There were 3 replications for each treatment. After harvesting the plants, the fresh weight was recorded. Then the plants were dried ( dry weight was recorded), ground and analysed. The highest Cd concentration in kalmi (Ipomoea aquatica) (1.8 mg/kg d.w.) and red amaranthus (Amaranthus cruentus) (2.1 mg/kg d.w.) was observed when the plants were grown in compost 10 t/ha treated soils. Compost 10 t/ha wheather alone or with fertilizer treatments increased the Cd concentration in plants (up to 30%) compared to control while the 1 and 5 ton compost/ha either reduced or not affected the Cd concentration in plants. The 10 t/ha compost application also reduced the pH of soils. Compost 10 t/ha application reduced the growth of plants wheras the other compost treatments alone or with fertilizers either increased the growth of plants or did not change the growth. Lime with compost higher than 10 ton/ha together with reduced phosphate fertilizer rates could be tried to reduce the input of Cd containing TSP in agricultural soils while maintaining the growth of plants.

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