Some factors affecting seed yield of spring oilseed rape (Brassica napus L.)
¹Lithuanian Institute of Agriculture, Akademija 5051, Dotnuva parish, Kedainiai distr., Lithuania, e-mail: email@example.com
²Lithuanian Institute of Agriculture Vezaiciai branch, Vezaiciai, LT-5845 Klaipeda distr., Lithuania, e-mail: firstname.lastname@example.org
The effect of nitrogen rates, time of nitrogen application, concentration of nitrogen, phosphorus and potassium in aboveground plant dry matter, stand population density, mean daily temperature, precipitation rate, growing degree days accumulated by plants at different growing stages and the duration of vegetative growth period on seed yield of Star, a cultivar of Brassica napus L., were studied in the field experiment. The seed yield was significantly affected by nitrogen rates of up to 120 kg ha-1. Further increase in nitrogen fertilisation had only a little effect on the seed yield of spring oilseed rape. There was a possibility to prolong the nitrogen application time until the start of flowering. However, in poorest soils, especially under unfavourable growing and development conditions, late nitrogen application could be much less effective. Nitrogen concentration in plant dry matter at 4–5 leaf stage, at the start and end of flowering and at the seed development stage had a significant effect on seed yield of spring oilseed rape. Phosphorus concentration was not important in the second part of vegetative growth. Potassium concentration, on the contrary, in the first part. With an increase of stand population density to up to 170 plant m-2 seed yield of spring oilseed rape was increasing. The increase in the duration of vegetative growth period and precipitation rate resulted in a higher seed yield. Meanwhile, the increase of mean daily temperatures and growing degree days had a negative effect on seed yield of spring oilseed rape. Presented regression equations could be used for a model for prognosis of seed yield of spring oilseed rape, based on agronomic and climatic factors.