Unveiling the effect of organic and inorganic amendments on arsenic accumulation by rice under paddy soil conditions

Muhammad Mahroz Hussaina, I. Bibia, N. K. Niazia,b,, M. Shahidc, M. F. Nawazd, S. Bashire, F.Younasa, and J.Rinklebef

a Institute of Soil and Environmental Sciences, University of Agriculture Faisalabad, Pakistan

b School of Civil Engineering and Surveying, University of Southern Queensland, Toowoomba, Queensland, Australia

c Department of Environmental Sciences, COMSATS University Islamabad, Vehari Campus, Pakistan

d Department of Forestry & Range Management, Faculty of Agriculture, University of Agriculture Faisalabad, Pakistan

e Sub-campus Depalpur, Okara, University of Agriculture Faisalabad, Okara, Pakistan

f Laboratory of Soil- and Groundwater-Management, Institute of Foundation Engineering, Water- and Waste-Management, School of Architecture and Civil Engineering, University of Wuppertal, Germany

hmahroz@gmail.com

Arsenic (As) contamination is emerging as a serious health and environmental issue globally especially in the South and South-east Asian countries including Pakistan, India and Bangladesh. In contrast to oxic soil environments, mobility and bioavailability of As to rice under (reduced) paddy soil conditions is an emerging issue to food security and human health. This is because rice is a staple food of about 3 billion people throughout the world including in India, Pakistan and Bangladesh and it accumulates As in paddy soil environments. The objectives of the present study were to: (1) explore the accumulation of As in different parts of rice (Oryza sativa L.) plants of the two contrasting rice genotypes (Kainat and KSK-385), and (2) evaluate the effect of As on morphological and biochemical parameters of rice plants. Six types of organic (farm yard manure (FYM), cow dung (CD), biogas slurry (BGS), mixed biomaterials waste (MBW)) and inorganic (gypsum, lignite) amendments were applied to determine their impact on soil As availability and uptake by the two rice genotypes. Arsenic-contaminated irrigation water was applied to rice plants after 15 days of transplantation in three intervals – each irrigation contained 15 mg As/L (400 mL per 2 kg soil). We found that the percentage increase in number of tillers ranged from 28–51% and tiller length spanned 28–50% with the maximum values obtained for FYM over their respective control for KSK-385 genotype. In the case of Kainat genotype, number of tillers and tiller length ranged from 41–50% and 18–33%, respectively, with the maximum values attained for CD treatment compared to control. This study highlights that organic amendments, notably FYM and CD, could possibly have nutritional effect, although contrasting, on the growth of two rice genotypes under As stress, thus providing an essential strategy to mitigate As accumulation in rice under paddy soil conditions. Our further analysis of As in rice tissue and in different soil fractions will help identify As bioavailability and transfer in paddy-soil rice system.

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