Yield Of Winter Oilseed Rape Research Articles

Residual effects of spraying imidazolinone-family herbicides on Clearfield®* sunflower production from the point of view of crop rotation

SUMMARY This research was carried out to determine soil residual effects on stand establishment rate and yield in the rotation crops soft winter wheat ( Triticum aestivum L.), barley ( Hordeum vulgare L.), winter oil seed rape (WOSR) ( Brassica napus L.), maize ( Zea mays L.) and sugar beet ( Beta vulgaris L.) following Intervix® (33g Imazamox + 15g Imazapyr) spraying in Clearfield® (CL) sunflower ( Helianthus annuus L.) production. The experiments were conducted at the Trakya Agricultural Research Institute in Edirne between 2007 and 2009 using a randomized complete block design (stripe plots) with three replications. Five crops were evaluated in crop rotation after spraying Intervix® on Clearfield® sunflower. As the experiment materials, we used the sunflower hybrid Sanay-CL and the cultivars Gelibolu (soft winter wheat, SWW), Bolayir (barley), Elvis (winter oil seed rapeseed, WOSR), Brasco (maize), and Leyla (sugar beet). Nitrogen and phosphorus fertilization were applied according to soil analysis recommendations. Observations were made of the number of plants emerged per m2, stand establishment, yield, time to flowering, time to physiological maturity, plant height, root length, head diameter, etc ., according to plants included in crop rotations. Based on statistical analysis of the data from crop rotation experiments, CL sunflower plots followed by wheat, barley, and maize were not negatively affected to a significant degree by Intervix® residues in terms of stand establishment and seed yield in either year. In the first year of crop rotation, however, when planting WOSR four months after Intervix® application on CL sunflower plots, stand establishment and seed yield decreased significantly, by 35.7 and 23.7%, respectively. When planting sugar beet nine months after Intervix® application on CL sunflower plots, stand establishment and beet yield decreased by 26.7 and 11.6%, respectively. However, in the second year in the same crop rotations plots, stand establishment and yield of WOSR and sugar beet planted after CL sunflower were not affected significantly by Intervix® residues.

Effects of high plant populations on the growth and yield of winter oilseed rape (Brassica napus)

The effects of plant density on the growth and yield of winter oilseed rape (Brassica napus) were examined in a series of five multifactorial experiments at Rothamsted Experimental Station between 1984 and 1989. Plant densities, manipulated by changing the seed rate and row spacing, or because of overwinter losses, ranged from 13·5 to 372 plants/m2. Normalized yields for the multifactorial plots increased with densities up to 50–60 plants/m2. In very high density plots in 1987/88, yield decreased as density increased >150 plants/m2. Plants grown at high density had fewer pod-bearing branches per plant but produced more branches/m2. Branch dry matter (DM) per plant was decreased by 42%, the number of fertile pods per plant and pod DM/plant by 37%. There was no effect of density on the number or DM of pods/m2. Over 74% of the fertile pods were carried on the terminal and uppermost branches of plants grown at high density in 1987/88 compared with only 34% in plants grown at low density in 1988/89. Seed DM/plant decreased with increase in density but seed size (1000-seed weight) increased. There was no effect of density on seed glucosinolate or oil contents.

Effects of Severity and Timing of Stem Canker (Leptosphaeria maculans) Symptoms on Yield of Winter Oilseed Rape (Brassica napus) in the UK

The relationships between yield loss and incidence (% plants with stems affected) or severity (mean stem score, 0–4 scale) of stem canker in winter oilseed rape were analysed using data from experiments at Rothamsted in 1991/92, Withington in 1992/93, Boxworth in 1993/94 and Rothamsted in 1997/98. Critical point models and area under disease progress curve (AUDPC) models were better than multiple point models for describing relationships between yield (t ha−1) and incidence or severity of stem canker for the four experiments. Since yield is influenced by many factors other than disease, % yield loss was calculated and critical point models and AUDPC models relating % yield loss to stem canker were constructed. The critical point models for % yield loss on stem canker incidence for three of the four experiments were similar, but differed from that for Rothamsted in 1991/92. There were also no differences between models of % yield loss on AUDPC of both incidence and severity for these three experiments. Therefore, general models of % yield loss (L) against AUDPC of incidence (X) or severity (S) of stem canker from growth stages 4.8 to 6.4 were derived from the combined data sets for the three experiments: L=−0.76+0.0075X (R2=35%, p<0.001), L=0.26+0.53S (R2=37%, p<0.001). The relationships between % yield loss and % plants with different stem canker severity scores at different growth stages were also analysed; the greatest yield losses were generally associated with the largest severity scores, for plants assessed at the same crop growth stage, and were also associated with the early development of stem lesions. Further analyses showed that % yield loss was related to incidence or severity of both basal stem cankers and upper stem lesions in experiments at Boxworth in 1993/94 and at Rothamsted in 1997/98.

Evaluation of seed yield determining factors of winter oilseed rape ( Brassica napus L.) by means of crop growth modelling

A simple crop growth model of winter oilseed rape ‘LINTUL-BRASNAP’, is briefly described and evaluated. The model simulates crop growth and development under optimum growth conditions and calculates 1) light reflection and absorption by the green canopy and flower layer, 2) total dry matter production based on light absorption and light-use efficiency by the green canopy 3) seed density (seeds m −2), 4) partitioning of dry matter to the seeds based on whether seed growth is limited by source or sink, 5) accumulation and mobilization of reserve carbohydrates and 6) crop phenological development. Two hypotheses on the duration of a critical period (CP) for seed set in a crop, (1) the duration of the flowering period and (2) a period of 350°Cd since onset of flowering, were tested by means of the model. Variation in seed density was better simulated with the second hypothesis. When the model was tested with data used for parameterization (cultivar Jet Neuf) and with other data (cultivar Victor), highly significant correlations were found between simulated and experimental data of various crop characteristics such as total dry matter production at various stages of crop development, seed density, pod density and seed yield. The differences between sowing dates were simulated better than the differences between years per sowing date. LINTUL-BRASNAP appears to be a useful tool for identifying the main crop characteristics responsible for variation in winter oilseed rape yield such as leaf area development, density of the flower layer and subsequent light absorption during the critical period of seed set. It can be used to explore options for improving the seed yield of winter oilseed rape.

The Effects of Drought and Nitrogen on Light Interception, Growth and Yield of Winter Oilseed Rape

Abstract The effects of drought and nitrogen on growth of winter oilseed rape were investigated during 1991–93 on a coarse sandy soil. Drought in the flowering phase or in the pod-filling phase or throughout the seasons was partly combined with three nitrogen levels of 200, 100 and 0 kg N ha−1. During the dry years 1992 and 1993, at 200 kg N ha−1, seed yield, pod number and seeds per pod were strongly decreased by drought, whereas the seed weight increased after drought during flowering. The straw yield was less affected by drought. Lower nitrogen levels reduced seed yield in the fully irrigated treatments; in the unirrigated treatments, however, the yield was slightly higher at the 0 N and 100 N level than at 200 N in both 1992 and 1993. Nitrogen and drought increased the nitrogen concentration of the seeds and decreased the oil concentration. The interception of photosynthetically active radiation (PAR) was estimated from spectral reflectance ratio measurements. The dry-matter: radiation quotient (∊t) f...

The effect Of insect pollination on plant development and seed production in winter oil-seed rape (Brassica napus L.)

SummaryThe effect of insect pollination on plant development and seed yield of winter oil-seed rape, cultivar Jet Neuf, was investigated by comparing plots caged with a honeybee colony, plots caged to exclude insects and plots uncaged and 'open-pollinated' by naturally occurring insects. Plants in the bee-pollinated plots finished flowering earlier, showed more advanced pod growth, and were shorter than those in the plots without bees. Pods from the plots with honeybees contained more seed post-flowering than those from plots without honeybees but the proportion of them that grew into mature seeds for harvest was determined by water availability during seed growth.

Effects of sowing date on the growth and yield of winter oil-seed rape (Brassica napus)

SummaryResults are reported from experiments carried out in three seasons in an environment with mild winters and early springs in which the date of sowing of winter oil-seed rape was varied from early September to early December. Consistently high seed yields were achieved in the late sowings and, in two of the three seasons, delaying sowing beyond early September resulted in significant yield increases. The pattern of dry-matter accumulation and changes in leaf area index were affected to a large extent by sowing date, but no significant effect on total dry-matter production at final harvest was found. Numbers of axillary inflorescences per plant and, in two of the experiments, numbers of fertile pods/m2, were reduced by late sowing, but large increases in numbers of seed per pod were found in each experiment. Mean weight per seed was reduced when sowing was delayed but there was no consistent effect on oil content. Differences were found between cultivars in the extent to which delayed sowing produced increased yields. It is suggested that early spring growth, delayed flowering and reduced reflexion of radiation during flowering were important factors leading to the high yields achieved by late sowings. No interactions were found between sowing date and plant population density for any yield component in one experiment.

Fungicide effects on light leaf spot, canker, crop growth and yield of winter oil-seed rape

SummaryField experiments with rape ovs Primor, Jet Neuf and Norli during 1979–83 tested the effects of benomyl, prochloraz, imazalil, thiabendazole, metalaxyl or triadimefon sprays applied at different times on disease, crop growth and yield. The principal disease in all experiments was light leaf spot (Pyrenopeziza brassicae).A single spray in autumn of benomyl or prochloraz at 0·5 kg a.i./ha consistently decreased incidence and severity of light leaf spot and sometimes decreased stem canker (Leptosphaeria macvlans). Under severe disease conditions in cv. Primor an autumn spray of fungicide contributed more to disease control than a spray in spring; a decrease in light leaf spot incidence was detectable up to 8 months after application. The autumn spray maintained plant population density, increased leaf area index, dry matter, crop growth rate, earliness of flowering, and yield by up to 0·69 t/ha; an autumn + spring spray increased yield by up to 0–83 t/ha. Effects on crop growth and yield were due to disease control not direct chemical stimulation of growth. Measurements of crop growth and population per unit area revealed the effects of fungicides more clearly than traditional disease assessments based solely on randomly selected plants.Triadimefon sprayed on rape stubble at high dose rate (1 kg a.i./ha) decreased incidence and severity of light leaf spot throughout the growing season of a subsequent rape crop, with beneficial effects on plant population density, growth, flowering and yield.Electrostatically charged rotary atomizer and conventional hydraulic spray applications of fungicide were equally effective in disease control. A reduction to one quarter in dose rate of prochloraz and 100–fold reduction in amount of water carrier (125 g a.i. in 4·3 1/ha) when applied electrostatically in autumn or autumn + spring had similar effects on disease, crop growth and yield to those obtained with a conventional sprayer delivering 500 g a.i. prochloraz in 410 1/ha.Fungicides, spray timing and methods of application are discussed in relation to the epidemiology of light leaf spot and canker and the economics of disease control.

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

SUMMARYSowing 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/m2. 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/m2, 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/m2, 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 (6000–12000/m2) 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.