Kvävebehov och beståndsuppbyggnad hos olika höstvetesorter 2016-2018

Sammanfattning: Since winter wheat is a large part of the income at farm level, winter wheat is an important crop for Swedish agriculture. The yield is determined by the yield components ears/m2, seeds/ear and thousand grain weight. Yield components are affected by the nitrogen availability throughout the time they are formed and reduced. In this thesis, 10 field experi-ments performed 2016–2018 and with eight different winter wheat varieties were analyzed and evaluated. The aim was to investigate how increasing mineral nitrogen (N) rates (120-300 kg N/ha) affect yield, protein and yield components in eight winter wheat varie-ties. Statistical analysis showed that differences between varieties in yield, protein and yield components were the same at different N-rates and between years (no interactions). The varieties could be divided into three groups with regard to the relationship between yield level and protein content. High yielding varieties seem to prioritize yield above protein content, while low yielding varieties develop protein content first and then yield. Praktik and Julius were good examples of this with significantly higher protein content at all nitrogen levels and at optimal N-rate (OptN), but had the lowest yields. The opposite tendency was found for Hereford, Mariboss and Torp who all had the highest yield at all nitrogen levels and at OptN, but the lowest protein content. The varieties Reform, Ellvis and Brons became a group in the middle. Differences between varieties in N-uptake in seeds followed the same pattern as the protein content: highest N-uptake in varieties with the highest protein and the lowest in varieties with low protein. Yield components was affected by the N-rate and varied with wheat variety. The number of seeds/ear increased up to 180 kg N/ha and the number of ears/m2 up to 240 kg N/ha, while the thousand grain weight decreased with increasing N-rates. The variety with the most ears/m2 was Mariboss, most seeds/ear was Torp, and the highest thousand grain weight was found in Hereford, Reform and Julius. Brons and Ellvis showed a compensatory ability for achieving high seed density/m2 through a combination of many ears/m2 and many seeds/ear. There were only small differences between the varieties (not significant) in OptN calculated for feed and milling wheat. However, there was a tendency to higher N demand in varieties with high protein at OptN and lower in varieties with low protein (feed wheat).The biggest difference in N demand was between feed wheat and milling wheat. Growing milling wheat increased net income with 1400 kr/ha compared with feed wheat, despite 24 kg N/ha higher OptN and due to higher protein. For feed wheat, Mariboss, Hereford and Torp had the highest yield and net income at OptN. For milling wheat varieties there were only statistical differences in protein at OptN. High yield in combination with low protein and vice versa levelled out differences in net income between varieties. Annual differences existed, yield and net income 2017 were higher than in 2016 and 2018. The dry and warm year 2018 the protein content at OptN was higher than in the other two years. Similar varietal differences were found 2018 as the other years.