During three years of testing (1988-1990) the effects of plant density (200, 400, 800 and 1200 plants/m2) and nitrogen fertilization (40 kg/ha N and 80 kg/ha N) on yield and yield physiology of linseed (Linum usitatissimum L. cv. Atalante) were tested on two locations both representing the cool humide climate of Schleswig-Holstein, Northern Germany, but differing in soil type (free draining sandy loam soil and poor sandy soil). On sandy loam soil yields were two-fold as high as on poor sandy soil. Doubling of the N-dose from 40 to 80 kg/ha N was effective in the better soil conditions, exclusively. It could be clearly demonstrated that stand establishment widely governed variation in yield. Independently of location and N-nutrition, the 400 plants/m2 M2 variant led to considerably high seed yields while narrow stands resulted in significantly lower yields. The overall highest yield (24.4 dt/ha) was established when the N-dose of 80 kg/ha was combined with 400 plants/m2. Total dry matter accumulated progressively from 49 to 63 days after field emergence (DAE). During this phase, start of the flowering period occurred. Hence, accelerated vegetative growth and reproductive development proceeded simultaneously. Increasing plant density resulted in higher rates of linear growth (LGR) and higher maximum growth rates (MGR). On the other hand, duration of linear growth rate (DLGR) decreased and day of maximum growth rate (MGRD) was reached much earlier in the same conditions. Shoot diameter was under plain control of stand density from 49 days after field emergence (DAE) to maturity. Plants from stands with extremely low competition revealed stem diameters of abt. 3.5 mm in maximum. Extremely narrow stands generated individuals not even reaching 2 mm in diameter. Increasing plant density caused a sharp decrease in net assimilation rate (NAR). This reaction was mainly controlled by competition rather than environment as no differences were proved between the two locations. NAR was measured at two stages of development, start of stem elongation and full flowering. At both stages, NAR was highest at 200 and 400 plants/m2, respectively. Chlorophyll content of leaves was assessed as an indicator of source activity for assimilate production. Pigment contents of upper and lower leaves were analysed at five sampling dates as related to stand density and N-fertilization. After relatively low levels were found at 21 DAE, chlorophyll accumulation was raised until full flowering (63 DAE) and then slowed down during the reproductive period. Low population stands and enhanced N-nutrition excelled by comparatively high chlorophyll contents and, with the exception of day 21, apical leaves were superior to basal ones. Independently of stand density, the higher N-supply resulted in higher chlorophyll contents at all stages and during the post-flowering period the loss of chlorophyll was delayed significantly on both levels of the vertical leaf canopy. As early as full flowering occurred, capsules were already formed to some extent (63 DAE). Until end of flowering capsule mass per area rose thoroughly due to initiation of capsules but also to growth of seeds and pericarps. During the post-flowering stages there was a further sharp increase caused by the most intensive period of seed filling. Low stand densities and the more favourable location promoted reproductive biomass. The highest harvest index (46.96 %) was attained with the lowest plant population grown on sandy loam soil. In contrast, 1200 plant/m2 adapted to poor sandy oil resulted in the overall lowest harvest index (22.63 %). Independently of location, the proportion of capsules to total biomass (% CI) was improved with low stand densities.
