3. Results and discussion
3.1. Agronomic properties
The mineral N fertilizer had greater impact than PS on the
average grain yield and plant N uptake from 2002 to 2011 (Table 3).
This may reflect the differing application strategies, with PS45
applied once before sowing and mineral N split into two doses.
PS45 applied before sowing was not used efficiently by the crop,
suggesting a significant proportion of the N in PS45 is probably lost
by volatilization in the 3e5 h before ploughing. The average
temperature during application was 12e18 C depending on the
year, and previous studies under these conditions suggest that 15e
50% of the N applied in PS45 could be lost by volatilization [43]. The
emission of NH3 from animal manures during and after spreading
depends on the temperature, humidity, precipitation and windspeed,
suggesting that the response of maize crops to different forms of N fertilizer will depend on both agronomic management
practices and the climate