Die Bodenkultur - Journal for Land Management, Food and Environment
L. Špokas, R. Velička, A. Marcinkevičiene und R. Domeika:
Optimization of spring rape harvest time by choosing crop varieties
Spring rape (Brassica napus L.) is ripe and harvest should start when average humidity of seeds is 15 %. The seed yield losses higher than 1 % determine the duration of harvest period. The beginning of harvest period and its duration of oilseed rape varieties ,Star,Sponsor, Marinka and Lisora was established to determine their suitability for growing.
Investigation of rape seed losses started when rape seed and stem humidity was approximately 30 % and seed rain from the pods did not begin. Seed losses were determined in every experimental plot by counting seeds crumbled into troughs (1,44 × 0,05 m). The beginning of rape harvesting period depended on different meteorological conditions and started: in 1997 – 20th of August, 1998 – 2nd of September, 1999 – 5th of August. At these dates the humidity of seeds was less than 15 %. The humidity of rape seed and stem declined during each day by 3–5 % and 4–7 % respectively.
Short rainfall had no influence on the humidity of rape seed. The losses of rape seed did not exceed 1 % of seed yield at seed humidity of 15 %. Rape plants of variety ,Lisora‘ have ripened 2 – 3 days earlier than these of other varieties, but daily natural seed losses from pods were approximately 0,3–0,4 %. Because of that further growing of rape variety , Lisora‘ is not perspective. The most resistant to natural seed rain was spring rape variety, Sponsor‘. Natural daily seed rain from the pods reached only 0,07 % of seed yield, harvest duration was 6 days. Spring rape varieties ,Star‘ and ,Marinka‘ must be harvested within 2–3 days because of high natural seed rain. It is very important to indicate in the certificate of the spring rape variety not only mass of one thousand seeds, their viability, but also rape ripening peculiarities, especially duration of harvest period until seed yield losses reach 1 %.
Key words: Brassica napus L., dynamic of humidity, duration of harvest, losses of seeds, variety.