Yield capacity and energy value of sorghum grain depending on the application of mineral fertilisers

Abstract

The paper covers the research into the productivity of sorghum (Sorghum bicolor (L.) Moench) grain for its widest use: nutrition, fodder for animals, and as a bioenergy crop, depending on the rates of mineral fertilisation. The purpose of the experiment was to analyse the effect of the fertiliser rates on the productivity of sorghum grain, its biofuel output, and energy received from it. The following methods were used: the field method, to investigate biological and ecological features of growth and development of the crop productivity and quality; the laboratory method, to determine the correlation between the crop and the environment (plant and soil analysis); the generalised method, to identify common properties and features. The application of fertilisers improved the quality of sorghum grain considerably: protein and fat content increased from 9.7% to 12.4% and from 3.37% to 3.62%, respectively; with higher fertiliser rates, starch content increased from 67.1% to 70.1% for cultivar ‘Dniprovskyi 39’ and from 65.8% to 68.8% for cultivar ‘Vinets’. Compared with the control treatment (without fertilisers) and under the effect fertiliser rates, grain yield capacity and above-ground mass increased. In the case of ‘Dniprovskyi 39’, at fertiliser rates N90P90K90, N120P120K120 and estimated rate of N50P40K70, grain yield capacity increased reliably, compared with the control treatment, and it amounted to 7.1, 7.9, and 7.3 t ha-1; grain yield capacity of ‘Vinets’ was 7.2, 7.8 and 7.0 t ha-1, respectively. Biomass yield capacity of ‘Dniprovskyi 39’ and ‘Vinets’ increased reliably only at the highest and estimated fertiliser rates. When ‘Dniprovskyi 39’ was grown, the highest total energy output was equal to 181.0 and 187.8 GJ ha-1; this indicator was 169.8 and 178.3 GJ ha-1 for ‘Vinets’. This was due to the estimated and maximal fertiliser rates. More than 80% of this energy is concentrated in solid biofuel and only 20% in bio-ethanol. The decrease in fertiliser rates led to a lower energy output of 1 ha