Impact of simultaneous increase in CO2 and temperature on soil aggregates, associated organic carbon, and nutritional quality of rice-wheat grains

Background: Food and nutritional security remain a major thrust area in the under developed and developing countries. These problems are exaggerated by the unprecedented challenges of climate change. Aims: The aim of this study was to assess the impact of climate change on grain quality of wheat and rice genotypes as well as their effect on soil aggregate fractions and aggregate associated carbon. Methodology: In the context, the present study was formulated by considering four predicted climate scenarios, namely, T0C0 (ambient condition), T0C1 (approx. 25% higher CO2), T1C0 (2 degrees C higher temperature) and T1C1 (25% higher CO2 + 2 degrees C higher temperature) and their impact on grain quality of wheat (HD2967, HD2733, DBW17, and HD3093) and rice (IR83376-B-B-24-2, IR84895-B-127-CRA-5-1-1, R Bhagwati, and IR64) genotypes as well as soil aggregate fractions and aggregate associated carbon. Results: The result revealed that T0C1 has a negative impact on grain nitrogen and protein content. On an average, nitrogen content in wheat and rice showed a decrease of about 15.55% (5.52%-25.32%) and 11.44% (3.33%-23.86%), respectively. Interestingly, the concurrent effect of elevated CO2 and temperature resulted in higher nitrogen and protein content as compared to other climate conditions. Further, P (P) content in the wheat and rice grains also improved under the elevated CO2 condition, whereas the content of potassium was not significantly influenced. Apart from major nutrients, micronutrients (Zn and Fe) were significantly influenced by climatic variables. The study revealed that grain Zn and Fe content of both the crops were reduced due to elevated CO2. The data on soil aggregate fractions revealed that elevated CO2 favors the formation of macro-aggregate, whereas an increase in temperature favors micro-aggregate fractions in the soil. Further, the elevation of CO2 also resulted in the accumulation of more carbon in the macro-aggregates. Conclusion: We conclude that elevated CO2 and temperature cause specific changes in soil aggregate formation and grain nutrient quality. Based on molar ratio of P/Zn and P/Fe, we identified varieties of rice (IR83376-B-B-24-2) and wheat (HD2733) with higher bioavailability to address the nutritional security with changing climate in developing countries.