The influence of sowing date on winter rape over-wintering and yield in the middle Lithuania

Abstract

A field experiment on different sowing dates of winter rape (Brassica napus L. spp. oleifera biennis Metzg.) was carried out during 2007.2008 at the Experimental Station of Aleksandras Stulginskis University. Experimental treatments were sowing dates: 1) August 10, 2) August 20, 3) August 30, 4) September 10. The objective of this study was to establish the influence of winter rape sowing date on preparation for over-wintering and seed yield. It was estimated, that 60.80 days period is necessary for winter rape preparation for wintering. According to the data of earlier experiments, winter oilseed rape sown in Lithuania before August 15 produced significantly higher seed yield than that sown at later dates. The weather during autumn months of several last years was warmer and possibility for later sowing of winter rape occurred. The possibility of later sowing allows winter rape sowing after more pre-crops. According to biometric parameters (number of leaves per plant, root collar diameter and height of apical bud), winter rape sown at the end of August (August 30), whose autumnal growth and cold acclimation period was 64 days, was best prepared for wintering. Results of our investigations showed that winter rape sown at the end of August (August 30) over-wintered most successfully. Crop density (44.2 plants m-2) in spring, silique number per plant (126.8) and biological yield (5.92 t ha-1) were best in winter rape sown at this date. Sowing date influenced the amount of dry matter in winter rape leaves and apical bud. In apical bud of winter rape sown at later dates (August 30 and September 10) amount of dry matter was higher compared with amount of dry matter in leaves. The highest amount of total sugar in all morphological parts of winter rape was obtained when it was sown at earliest date (August 10). The strong positive correlations between the sum of day air temperatures .+2 ‹C during the period of prepar