The addition of magnesium sulfate and borax to urea reduced soil NH3 emissions but increased N2O emissions from soil with grass

Abstract

Nitrogen (N) use efficiency can be increased by the addition of substances to urea. Magnesium sulfate (MgSO₄) and boron were considered as plant nutrients, while zeolite was used as soil conditioner. The addition of these substances may affect soil NH₃ and N₂O emissions, by increasing N use efficiency. We conducted an 30 days incubation experiment with ryegrass using fertilizer treatments (12 g N m^-2) as follows: urea (U); urea + MgSO₄ (UM); urea + MgSO₄ + borax (UMB); zeolite + urea + MgSO₄ (Z-UM); and zeolite + urea + MgSO₄ + borax (Z-UMB). We measured NH₃ and N₂O emissions and the aboveground N uptake of ryegrass. Cumulative NH₃ emissions of UM, UMB, Z-UM and Z-UMB were 10%, 53%, 21% and 58% lower than U, respectively, while their N₂O emissions were 32%, 133%, 43% and 72% higher than U, respectively. Aboveground N uptake of UM, UMB, Z-UM and Z-UMB were 9%, 6%, 12% and 13% higher than U, respectively. Overall, we suggest that the addition of MgSO₄ and borax were effective in reducing NH₃ emissions and potentially increase plant N uptake. However, the risk of higher denitrification and N₂O emissions also needs to be considered. This study reveals the considerable effect of MgSO₄ and borax in soil N cycles. Future research should evaluate how the application of urea + MgSO₄ + borax effects gaseous emissions and crop yield of dicotyledons and in drier soil conditions.

Keywords: Borax; Magnesium sulfate; Nitrous oxide; Urea; Zeolite; ammonia.