Brown coal-urea blends for increasing nitrogen use efficiency and biomass yield

Biplob K. Saha1, Michael T. Rose2, Vanessa Wong3, Timothy R. Cavagnaro4 and Antonio F. Patti1*

1School of Chemistry, Monash University, Clayton, Victoria, 3800, Australia
2NSW Department of Primary Industries, Wollongbar Primary Industries Institute, Wollongbar, NSW 2477, Australia
3School of Earth, Atmosphere & Environment, Monash University, Clayton, Victoria, 3800, Australia
4School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, South Australia, 5064, Australia

*Corresponding author. Email: [email protected]

Abstract

Increasing crop yield by minimum application of nitrogenous fertilisers is becoming more important due to its detrimental effects on the environment. Addition of humic rich brown coal (BC) as an organic amendment can alter N cycling and its availability to crop plants. However, the effect of brown coal-urea (BCU) blends on the biomass yield and N uptake by plant needs to be studied. Therefore, a glasshouse pot trial study was conducted to assess the effects of BCU blends on the growth, biomass yield and N uptake by silver beet. Blending of urea with BC showed a promising impact on the behavior of N fertiliser in the soil system. Compared to urea, BCU blends increased biomass yield by 27% and 23% in both a neutral (pH 7.24) and acid (pH 5.4) soil, respectively. In addition, incorporation of BCU blends to soil generally suppressed N2O emissions by 29% compared to urea. Application of BCU blends in soil maintained significantly higher amounts of mineralisable N in soil compared to urea application only. Moreover, addition of BCU blends increased the N uptake by silver beet and organic carbon content of soil. The blends with higher BC had higher biomass yield, maximum N uptake and maintained higher mineral N in soil compared to the blends with lower BC. The overall results suggest that blending of urea with BC can significantly increase N availability and its uptake by silver beet. As a result better crop yield can be obtained due to increased fertiliser N use efficiency.