Sweet pearl millet and sweet sorghum have high nitrogen uptake efficiency under cool and wet climate
Thivierge, M.N., Chantigny, M.H., Seguin, P., Vanasse, A. (2015). Sweet pearl millet and sweet sorghum have high nitrogen uptake efficiency under cool and wet climate, 102(2), 195-208. http://dx.doi.org/10.1007/s10705-015-9689-2
© 2015, Springer Science+Business Media Dordrecht. Nitrogen use efficiency is a key factor for the economic and environmental sustainability of farms. It comprises the ability for crops to recover applied fertilizer N in their aboveground biomass, called fertilizerN uptake efficiency (NupE). Sweet pearl millet [Pennisetum glaucum (L.) R.BR.] and sweet sorghum [Sorghum bicolor (L.) Moench] are C4 annual crops known for their capacity to produce high yield under N-limiting conditions, suggesting high NupE. A field study was conducted for 2 years on sandy loam soils in eastern Canada. The NupE was determined using a <sup>15</sup>N-tracing approach. Comparisons were made for both species in regards to their response to (1) increasing mineral N rate (0–160 kg N ha<sup>−1</sup>), (2) mineral versus organic N (liquid swine and dairy cattle manures), and (3) single versus split N application. For mineral N treatments, NupE ranged from 54 to 82 %, which is greater than values generally reported for conventional crops such as corn. Moreover, NupE increased with N rates. These findings suggest than both species expressed N luxury consumption. The NupE was lower with organic than with mineral N, and a larger proportion of N remained in the soil, suggesting that N immobilization occurred. The presumed losses (unrecovered <sup>15</sup>N) were <24 kg N ha<sup>−1</sup> in all mineral and most organic N treatments. Splitting N application had little effect on NupE. Our results confirm that sweet pearl millet and sweet sorghum are highly efficient at recovering fertilizer N and, with adequate residue management, may represent a low environmental risk.
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