Content of inorganic elements in rice grain depending on irrigation methods

Abstract

Purpose. To study the content of heavy metals in the grain of two varieties of rice under different irrigation conditions. To estimate the content of basic microelements – components of redox systems of plants in the grain of rice for biofortification and inhibition of heavy metal accumulation. 

Methods. Plants of rice varieties ‘Consul’ and ‘Viscount’ were grown on the experimental fields of the Rice Institute of NAAS of Ukraine during flooding or drip irrigation. Grain samples were digested for analysis by microwave sample preparation in nitric acid on Milestone Start D. The content of inorganic elements was determined by ICP-MS method on Agilent 7700x in helium flow mode. Calibration solutions from Inorganic Ventures, USA were used.

Results. Compared to flood irrigation, the introduction of drip irrigation leads to a 2.3–3 times decrease in the accumulation of arsenic in the grain. The increase in cadmium and strontium accumulation was found. Drip irrigation also increases the accumulation of trace elements in grain – components of redox systems of plants (copper, zinc, manganese). A slight decrease in iron content is probably associated with the activation of mechanisms for blocking the inflow and reuse of arsenic into the grain. The yield of rice varieties was higher during flooding. In the case of ‘Viscount’ and ‘Consul’, it was 9.35 and 11.76 t/ha in the case of flooding, and 6.80 and 9.30 t/ha in the case of drip irrigation, respectively. The content of inorganic elements/ ash content is significantly lower in the variety ‘Consul’. This is probably due to the dissolution of elements in the biomass with high productivity of this variety. 

Conclusions. The natural contamination of rice crops with arsenic limits the nutritional value of the crop. The introduction of drip irr igation of r ice crops signif icantly reduces the accumulation of highly toxic arsenic in the grain, which is especially important for children food. The increase in cadmium and strontium accumulation determined by drip irr igation leads to high equirements for the quality of phosphate fer tilizers used in crop cultivation echnologies. Introduction of drip irr igation optimizes the aerobic conditions of ion supply, which leads t o i nc r ea s ed accumul at i on of t r ace e l ement s – components of redox systems of plants. The only exception is a slight decrease in iron content , which is probably associated with the activation of mechanisms of inhibition of the inflow of arsenic to the grain of rice. At the same time, there is a slight decrease in the productivity of crops. Thus, under drip irr igation there is an increase in the accumulation of biologically important metals and a decrease in the accumulation of highly toxic arsenic.