The effects of delayed sowing and weather on growth, development and yield of winter oil-seed rape (Brassica napus)

Abstract

Sowing winter oil-seed rape cv. Victor late in autumn (late September or October) in seven seasons from 1970 to 1977 gave enormously variable seed yields, from 120 to 450 g/m 2 . All crops made little growth before winter, and yield was related to the size of the crop at flowering, a function of the length of time for radiation interception and growth between the 'beginning of spring', when mean temperatures rose consistently above 5 °C, and full flower in late May. A late spring in 1970 gave the poorest growth and lowest yield, whereas in 1977 an early spring coincided with late flowering to give exceptional growth, and yields higher than from any early sowing.Crops sown in early autumn (before mid-September) produced more consistent seed yields, 280-360 g/m 2 , except in the dry year of 1976. All grew well in autumn, overwintered with a large leaf area, and once temperatures rose in spring, rapidly reached peak area and full flower in early May. They were all large at flowering, and yield was apparently limited more by post-flowering events.With all sowings numbers of pods and seeds were largely determined during a 3-week phase in late May and early June, extending from full flower until most pod hulls had finished growing. Late sowings produced 3000-6000 pods/m 2 , and the number of seeds retained per pod varied widely, from 7 on a poorly grown crop to 22 on a well grown crop, thus expressing the yield potential determined by crop size at flowering. Early sowings, however, produced apparently excessive numbers of pods (6000-12 000/m 2 ) and few seeds per pod (6-10), so that yield varied little, regardless of crop size. Early in the phase, when the number of seeds was determined, the mass of yellow flowers at the top of the crop reflected or absorbed up to 60 % of incoming radiation, and then the large number of pods increasingly shaded each other and competed for assimilate, resulting in heavy seed losses. A high-yielding crop type may therefore need to incorporate the restricted pod production and good seed retention of some well-grown latesown crops with the reliability and desirable agronomic features of early-sown crops.Final seed weight varied more between seasons (3-7-5-3 nag) than between sowings. Seed growth mainly took place after the number of seeds had been determined, the duration depending on temperature, but rate of growth apparently more on assimilate supply, a function of environmental factors and the number of competing seeds.

Modeling Nitrogen Uptake in Oilseed Rape cv Capitol during a Growth Cycle Using Influx Kinetics of Root Nitrate Transport Systems and Field Experimental Data

“…Mendham et al (1981) also have reported similar results. These results were confirmed using an apetalous flower line (Rao et al, 1991).…”

“…The two constitutive and inducible components of each transport system (high or low affinity) were assumed to be similarly regulated by these compounds. The effect of PAR was taken into account in the model from bolting to harvest according to Chapman et al (1984) and Mendham et al (1981), who have demonstrated a decrease of about 60% to 80% of PAR transmitted inside the rape canopy at the beginning of flowering. No interaction between climatic factors (temperature and PAR) was taken into account.…”

Effect of Sowing Method and N Application on Seed Yield and N Use Efficiency of Winter Oilseed Rape

“…Several approaches from, for example, France and Germany take the amount of N in the WOSR canopy at the end of autumn growth and/or at the beginning of spring growth into account [18][19][20]. In one study of insignificant leaf losses over winter, a well-developed rapeseed canopy showed a higher leaf area index at the beginning of spring growth than a poor canopy, which, in consequence, allows for reduced N fertilization rates [21]. Henke et al [19] showed that even if canopy N is lost over winter due to frost, optimum N requirements in spring decreased with increasing canopy N in late autumn.…”

Evaluation of Micro and Macro Elements in Drought Stress Condition in Cultivars of Rapeseed (Brassica napus L.)

“…With the research that the researcher performed in the condition of humidity stress on Sulphur in Rapeseed (Brassica napus), they reached to this conclusion that the harsh reduction of sulphur in the Rapeseed (Brassica napus)'s organs would reduce the production of chlorophyll and photosynthesis reduction and the producing the dry substance would reduce and also the indicator of the harvesting would be reduce too [4] . Mendham et al [6] are believe that with the reduction of absorbing Sulphur in the condition of dry stress besides the function reduction the efficiency amount o water consumption would also decreasing (WUE) in the Rapeseed (Brassica napus) and it would decrease the amount of leaf level indicator and so it would cause the increasing of roots in comparison with the aerial organs. Sulphur with synthesizing the protein in Rapeseed (Brassica napus) would cause the increasing of the plants tolerance toward the dry situation [2,5] , but in the situation of harsh drought stress with the intense reduction in absorbing the sulphur the synthesis of protein would decrease and in first step with the hydrolyze of protein and changing it to the simple saccharin would try to stabilize the osmosis potential and its ingredient relatively water content [11] but with the continues of the stress condition the Rapeseed (Brassica napus) would loose its tolerance and with decreasing in the turgor pressure the output of the water consumption would cause the harsh reducing of functioning [7,8] .…”