LAUSR

A short-term incubation experiment (30-day) was conducted using a calcareous sandy loam soil (having pH of 7.65 and CaCO3 of 16.8) amended with urea (U) at application rate of 360 kg N ha−1 in the presence and absence of biochars (BCs) produced from date palm waste at two pyrolysis temperatures of 300 (BC300) and 500 °C (BC500) with application rate of (0 and 45 Mg ha−1) at different incubation temperatures of 15, 25, and 35 °C to investigate their short-term effects on soil ammonia (NH3-N) volatilization and different forms of nitrogen (N) transformation. The results showed that applying BC300 had 23.1% and 12.5% and 10.2% significant (P = 0.05) lower cumulative NH3-N volatilization than U treatment at incubation temperatures of 15, 25, and 35 °C, respectively. Meanwhile, applying high pyrolysis temperature BC (BC500) showed significant (P = 0.05) lower cumulative NH3-N volatilization only at 15 °C, which accounted for 21.9% lower than U treatment. The concentrations of ammonium (NH4-N) in the soil increased with the progress of incubation time and reached the maximum peak at days 3–15 of incubation. With the progress of incubation time, BC300-treated soil showed a higher concentration of NH4-N and ammonification rate than those of other treatments (U and U + BC500); however, BCs did not show significant effects on NO3-N concentration and nitrification rate. Hence, integrated use of urea and biochar pyrolyzed at 300 °C having acidic functional groups and high content of total acidity may serve as an efficient fertilization strategy for minimizing NH3-N volatilization and enhancing the available form of N in calcareous soils from an arid environment.