Abstract
The balance between applied and harvested nitrogen (yield removed nitrogen, YRN %) is a recognized indicator of the risk of N leaching. In this study we monitored the genetic improvements and environmental variability as well as differences among crop species (spring cereals and rapeseed) in YRN in order to characterize changes that have occurred and environmental constraints associated with reducing N leaching into the environment. MTT long-term multi-location field experiments for spring cereals (Hordeum vulgare L., Avena sativa L. and Triticum aestivum L.), turnip rape (Brassica rapa L.), and oilseed rape (B. napus L.) were conducted in 19882008, covering each crops main production regions. Yield (kg ha-1) was recorded and grain/seed nitrogen content (Ngrain, g kg-1) analyzed. Total yield N (Nyield, kg ha-1) was determined and YRN (%) was calculated as a ratio between applied and harvested N. A mixed model was used to separate genetic and environmental effects. Year and location had marked effects on YRN and Nyield. Average early and/or late season precipitation was often most advantageous for Nyield in cereals, while in dry seasons N uptake is likely restricted and in rainy seasons N leaching is often severe. Elevated temperatures during early and/or late growth phases had more consistent, negative impacts on YRN and/or Nyield for all crops, except oilseed rape. In addition to substantial variability caused by the environment, it was evident that genetic improvements in YRN have taken place. Hence, YRN can be improved by cultivar selection and through favouring crops with high YRN such as oat in crop rotations.;
Highlights
Risks associated with nitrogen leaching into natural water systems is high in northern Europe and especially in Finland with its more than 100000 lakes, km of Baltic coastline (Peltonen-Sainio et al 2009d), and substantial annual precipitation averaging 500–650 mm for 1970–2000 (FinnishMeteorological Institute)
Turnip rape and oilseed rape contrasted with oat
We found the highest relative derived differences among cultivars for N traits in oilseed rape, for which the ranges between the weakest and strongest cultivars were 31% units for YRN and 33 kg ha-1 for Nyield
Summary
Risks associated with nitrogen leaching into natural water systems is high in northern Europe and especially in Finland with its more than 100000 lakes, km of Baltic coastline (Peltonen-Sainio et al 2009d), and substantial annual precipitation averaging 500–650 mm for 1970–2000 (FinnishMeteorological Institute). The capacity of spring sown crops to utilize nitrogen (N) determines the potential risk for N leaching in the major production areas of Finland, with typical peaks in autumn and winter (Syväsalo et al 2006). Nitrogen surplus is evident when the quantity of N applied is greater than that used for production of crop biomass (Rankinen et al 2007). For this and economic reasons it is essential that N application occurs when the crop needs it, when it can be used for biomass production and is harvested instead of remaining unused in the soil (Peltonen-Sainio et al 2009d). Yield removed nitrogen (YRN, %) represents the ratio between applied and harvested N
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