Effects of lead (pb) on some cereal crops of Bangladesh and their remediation

Abstract

In recent ages, lead (Pb) poisoning in human body through soil-crop system is a serious threat to people of Bangladesh. Pot experiments were conducted with soils of belabo series at the research field of the Department of Soil Science, Govt. Bangla College, Dhaka, to investigate the effect of different doses of Pb (0, 50, 100, 150 and 200 ppm) and the ameliorating effects of several amendments (cowdung, poultry manure and lime) with 100 ppm Pb on Rice (variety: BRRIdhan- 49), Wheat (variety: BARI wheat-26) and Maize (variety: BARI maize-9) and the varietal remediation of soils with 200 ppm Pb using four rice varieties (BRRIdhan- 33, 49, 53 and 54) and three wheat varieties (Shotabdi, Prodip and BARI wheat-26). A field experiment was also conducted to investigate the effect of different Pb doses (0, 50 and 100 ppm) on above mentioned wheat varieties and one maize variety (BARI maize-9). All the treatment and varietal combinations with three replications were laid out in a completely randomized design in pots and plots. Pot experiments through applying different Pb doses in rice, wheat and maize varieties showed a gradual and significant decrease in yield and growth parameters and mineral nutrient concentration, except total N concentration gradually and significantly increased and then again decreased in rice grain, maize shoot and grain respectively, while N concentration gradually and significantly increased in maize root. The highest N concentrations in rice grain, maize root, shoot, grain were obtained at 100, 200, 150 and 150 ppm Pb treatments respectively. Besides increasing Pb concentration in soil caused an increase in Pb concentration in all crops. In all cases shoot accumulated more potassium than root and grain. All the crop varieties showed higher Pb accumulation in root than in shoot and grain and Pb accumulation was in the order root > shoot > grain. For a given Pb treatment in case of root, rice root accumulates higher Pb than root of wheat and maize and Pb accumulation was in the order rice > wheat > maize while in case of shoot or grain, wheat shoot and grain accumulates higher Pb than shoot and grain of rice or maize. Field experiments through applying different Pb doses in wheat and maize varieties showed similar results as in pot experiments. Application of 100 ppm of Pb significantly decreased the growth and yield parameters and mineral nutrient concentration in all crops, except N concentration increased in rice grain and maize root, shoot and grain and Pb concentration in root, shoot and grain of three crops, as compared with their control. Addition of different amendments (cowdung, poultry manure and lime) on soils with 100ppm Pb treatment significantly increased the growth and yield parameters and N, P, K, Ca, Mg concentration and significantly decreased the Pb concentration in rice, wheat and maize varieties in comparison to un-amended soils. Among the amendments, cowdung had greatest ability to reduce Pb toxicity and increase yield and growth parameters and mineral nutrient concentration in crops except lime treatment resulted the highest 1000 grain weight of wheat (46.43g/pot). Besides, poultry litter enhanced the K concentration in rice shootand grain and lime enhanced Ca concentration in root and shoot of rice and in root, shoot and grain of wheat and maize. Moreover, in case of rice and wheat Pb toxicity reducing capacity was in the order cowdung> lime > poultry litter, while in case of maize Pb toxicity reducing capacity was in the order cowdung> poultry litter > lime. Pot experiments for varietal remediation of soils with 200 ppm Pb treatment revealed that among the respective rice and wheat varieties, BRRIdhan-49 and BARI wheat-26 accumulated the highest concentrations of Pb; so their agronomic parameters and nutrient uptakes were lesser than other respective rice and wheat varieties. Conversely, BRRI dhan-54 and Shotabdi had the ability to withstand Pb stressed soil and concentrates less amounts of Pb in root, shoot and grain, hence had a better capability to increase growth and yield parameters and mineral nutrient concentrations than other respective rice and wheat varieties. In summary it may be stated that all investigated methods (selection of suitable plant varieties, crops, soil amendment with cowdung, poultry litter and lime) caused partly significant reductions of Pb accumulation from contaminated soils. Nevertheless, for the optimization of the reduction effects, it is necessary to select and combine the different methods according to crop specific and varietal characteristics.