In high-yielding sprinkler-irrigated maize monoculture systems,
the optimal rate of N (organic and/or mineral) fertilisation
could vary greatly from year to year, depending especially on
such factors as soil initial NO3
−-N content, or the climatic conditions
of the current year.
When soil initial NO3
−-N content was very high there was
no yield response to N (organic or/and mineral) fertilisation and
N losses during the growing period increased significantly. High
N (organic and/or mineral) fertilised treatments generated high
levels of soil residual NO3
−-N and high N losses during the
growing period in all of the studied years. Elevated soil residual
NO3-N content could increase the risk of N leaching during
autumn-winter, which in turn could constitute a potential source
of environmental problems.
In general, the minimum N rates (organic and/or mineral)
to achieve maximum grain and biomass yields coincided with
the minimum N losses and the minimum soil residual NO3-N