Seed yield response to N fertilization and potential of proximal sensing in Italian ryegrass seed crops

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  • Tim Vleugels, ILVO (Flanders Research Institute for Agricultural Fisheries and Food), Plant Sciences Unit, Caritasstraat 39, 9090 Melle, Belgium, Belgien
  • Georges Rijckaert, ILVO, Plant Sciences Unit, Burg. Van Gansberghelaan 109, 9820 Merelbeke, Belgium, Belgien
  • René Gislum
Italian ryegrass (Lolium multiflorum L.) seed crops are often routinely fertilized with a predetermined amount of nitrogen (N) fertilizer in spring. However, nitrate leaching and increasing N fertilizer prices require rationalized fertilizer applications without compromises in seed yield. The objectives of this study were (1) to determine the seed yield response to N fertilization, and (2) to evaluate if NDVI values can reliably predict the N status in Italian ryegrass seed crops. During eight years, field trials were conducted with two cultivars ‘Melclips’ and ‘Melquatro’, and seven N strategies applied after the forage cut as single or split application: 0, 60, 60 + 30, 90, 90 + 30, 120 and 150 kg N ha−1. NDVI values were obtained with a ‘GreenSeeker’ optical sensor. Maximum seed yield was attained at 141 kg N ha−1 total available N (92 kg N ha−1 fertilized). Higher fertilizations only increased NNI values but not seed yield. Split-application strategies were equal to single-applications in terms of seed yield, which indicates that remedial fertilizations at the two-three node stage are effective. NNI values at all growth stages predicted seed yield adequately: maximum seed yield was attained at NNI values of 0.86 in the 2–3 node stage, 0.72 at the beginning of heading, and 0.59 at full ear emergence. NDVI values were correlated with NNI values, but were also heavily influenced by trial year. Therefore, is it impossible to establish NDVI thresholds to decide on remedial N fertilization.
TidsskriftField Crops Research
Sider (fra-til)37-47
Antal sider11
StatusUdgivet - sep. 2017

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