Do high nitrogen use efficiency rice cultivars reduce nitrogen losses from
paddy fields?
Several high nitrogen use efficiency (high-NUE) rice cultivars have been
developed to meet the increased food demand and urgent environmental
concerns, but the effect of these cultivars on reducing N losses from
paddy fields is not well documented. A two-year field experiment was
conducted in the Taihu Lake region of China to evaluate the advantages of
high-NUE rice on yields and N losses in 2011 and 2012. Two “high-NUE” rice
cultivars and a conventional cultivar were compared at the same fertilizer
N input of 200 kg N ha−1. Ammonia (NH3) volatilization, N2O emission, N
leaching and runoff losses were monitored during the entire rice growing
season within a rice–wheat rotation. The high-NUE rice cultivars Wuyunjing
23 (W23) and Zhendao 11 (Z11) achieved higher grain yields, and took up
more N with a higher NUE than the conventional cultivar Wuyujing 3 (W3).
There was a trend toward smaller N losses with the high-NUE cultivars W23
and Z11 (N leaching, N2O emissions and NH3 volatilization decreased by
12–23%, 5–10% and 2–8%, respectively), but the total reductions for the
growing season compared to W3 were not statistically significant. Even
though the high-NUE cultivars did not significantly decrease the absolute
losses of N from the field, they did show lower N losses expressed on a
yield-scaled basis than the conventional cultivar due to higher grain
yields. Cultivars W23 and Z11 produced 21–27% less NH3 volatilization,
23–26% less N2O emission, 23–33% less N leaching, and 13–24% less N in
runoff per ton of rice grain harvested than those of W3. Another cultivar
Aoyusi 386 (A386), known to have a higher N uptake at early growth stages
than W23 and Z11 was also planted in 2012. This cultivar significantly
reduced N losses compared with the conventional variety. It was concluded
that improving N uptake rate of high-NUE cultivars in the early stages of
growth would be most effective in decreasing N losses and that the main
part of N fertilizer applications should be later in the growing season
than is currently practiced in the region.
Do high nitrogen use efficiency rice cultivars reduce nitrogen losses frompaddy fields?Several high nitrogen use efficiency (high-NUE) rice cultivars have beendeveloped to meet the increased food demand and urgent environmentalconcerns, but the effect of these cultivars on reducing N losses frompaddy fields is not well documented. A two-year field experiment wasconducted in the Taihu Lake region of China to evaluate the advantages ofhigh-NUE rice on yields and N losses in 2011 and 2012. Two “high-NUE” ricecultivars and a conventional cultivar were compared at the same fertilizerN input of 200 kg N ha−1. Ammonia (NH3) volatilization, N2O emission, Nleaching and runoff losses were monitored during the entire rice growingseason within a rice–wheat rotation. The high-NUE rice cultivars Wuyunjing23 (W23) and Zhendao 11 (Z11) achieved higher grain yields, and took upmore N with a higher NUE than the conventional cultivar Wuyujing 3 (W3).There was a trend toward smaller N losses with the high-NUE cultivars W23and Z11 (N leaching, N2O emissions and NH3 volatilization decreased by12–23%, 5–10% and 2–8%, respectively), but the total reductions for thegrowing season compared to W3 were not statistically significant. Eventhough the high-NUE cultivars did not significantly decrease the absolutelosses of N from the field, they did show lower N losses expressed on ayield-scaled basis than the conventional cultivar due to higher grainyields. Cultivars W23 and Z11 produced 21–27% less NH3 volatilization,23–26% less N2O emission, 23–33% less N leaching, and 13–24% less N inrunoff per ton of rice grain harvested than those of W3. Another cultivarAoyusi 386 (A386), known to have a higher N uptake at early growth stagesthan W23 and Z11 was also planted in 2012. This cultivar significantlyreduced N losses compared with the conventional variety. It was concludedthat improving N uptake rate of high-NUE cultivars in the early stages ofgrowth would be most effective in decreasing N losses and that the mainpart of N fertilizer applications should be later in the growing seasonthan is currently practiced in the region.
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