| Despite the perceived importance of N to wheat growth and production, few studies
have attempted to examine the effects of warming on wheat N uptake patter or its
preference for NO3−-N, NH4+-N, especially under different tillage systems. In the
North China Plain, an in situ 15N labelling study was conducted on winter wheat in
which effects of experimental warming during the jointing stage under till and no-till
tillage systems on uptake of total N and three forms of N (NO3−-N, NH4+-N and
glycine-N) was studied. Warming strongly enhanced wheat biomass and N content in
both roots and shoots. Total N uptake rates increased by 40% and 47% under till and
no-till treatments, respectively. Warming changed the uptake pattern of the three forms
of N by significantly increasing the contributions of NO3−-N and glycine-derived N,
while decreasing the contribution of NH4+-N. Between the two tillage systems, wheat
under no-till without warming obtained more N than till. However, warming was found
to suppress N uptake under no-till relative to till. Collectively, high temperatures
accelerate N sequestration in winter wheat and improve the preferential contribution
of NO3−-N due to high soil N availability and enhanced microbial activity. |