Investigating the effects of interactions of environmental factors on grain quality using statistical techniques

Investigating the effects of interactions of environmental factors on grain quality using statistical techniques

The increasing carbon dioxide [CO2] in the atmosphere increases crop productivity. However, the grain quality of cereals and pulses are substantially decreased and consequently compromise human health. CO2, temperature, water and nitrogen are considered as the most critical factors influencing crop production. These environmental variables significantly affect grain yield and grain protein concentrations, which are key determinants of grain quality. Consequently, they affect human and animal nutrition. A more detailed understanding of how these environmental factors contribute towards the grain protein content is essential for addressing global nutrient security in the changing climate.

In this thesis, meta-analysis techniques were employed to investigate the effect of elevated [CO2] (e[CO2]) on protein, zinc (Zn) and iron (Fe) concentrations of major food crops including wheat, rice, soybean, field peas and corn considering different levels of temperature, water and nitrogen (N). Each crop, had decreased protein, Zn and Fe concentrations when grown at e[CO2] concentration compared ambient [CO2] (a[CO2]) concentration. However, the responses of protein, Zn, and Fe concentrations to e[CO2] were modified by water stress and N. There was an increase in Fe concentration in soybean under medium N and wet conditions but nonsignificant. The reductions in protein concentrations for wheat and rice were ~5%–10%, and the reductions in Zn and Fe concentrations were ~3%–12%. For soybean, there was a small and nonsignificant increase of 0.37% in its protein concentration under medium N and dry water, while Zn and Fe concentrations were reduced by ~2%–5%. The protein concentration of field peas decreased by 1.7%, and the reductions in Zn and Fe concentrations were ~4%–10%. The reductions in protein, Zn, and Fe concentrations of corn were ~5%–10%. Bias in the dataset was assessed using a regression test and rank correlation.

Also, randomized trials were carried out based on the conditions of the factorial experiments to show the effect of [e[CO2]], water, N, and their interactions on protein, Zn and Fe of wheat crop. To determine the effects of interactions of CO2, water and N on protein, Zn and Fe, the designed experiments are implemented in Matlab to investigate all possible possibilities for primary, binary and triple interactions. These results suggested that high [CO2] concentrations under various levels of environmental conditions affect protein, Zn and Fe concentrations in wheat crop negatively, with protein, Zn and Fe were decreased by 4.5%, 3.5%, 4.1%, respectively, during the three-year experimental period.

The outcomes of this project will inform experts and decision-makers about the effects of CO2, temperature, water and nitrogen on grain quality, and enable the investigation of suitable solutions.