Autumn-sown Crop Research Articles

Photoperiod and Vernalization Control of Flowering-Related Genes: A Case Study of the Narrow-Leafed Lupin (Lupinus angustifolius L.)

Narrow-leafed lupin (Lupinus angustifolius L.) is a moderate-yielding legume crop known for its high grain protein content and contribution to soil improvement. It is cultivated under photoperiods ranging from 9 to 17 h, as a spring-sown (in colder locations) or as an autumn-sown crop (in warmer regions). Wild populations require a prolonged cold period, called vernalization, to induce flowering. The key achievement of L. angustifolius domestication was the discovery of two natural mutations (named Ku and Jul) conferring vernalization independence. These mutations are overlapping deletion variants in the promoter of LanFTc1, a homolog of the Arabidopsis thaliana FLOWERING LOCUS T (FT) gene. The third deletion, named here as Pal, was recently found in primitive germplasm. In this study, we genotyped L. angustifolius germplasm that differs in domestication status and geographical origin for LanFTc1 alleles, which we then phenotyped to establish flowering time and vernalization responsiveness. The Ku and Jul lines were vernalization-independent and early flowering, wild (ku) lines were vernalization-dependent and late flowering, whereas the Pal line conferred intermediate phenotype. Three lines representing ku, Pal, and Ku alleles were subjected to gene expression surveys under 8- and 16-h photoperiods. FT homologs (LanFTa1, LanFTa2, LanFTc1, and LanFTc2) and some genes selected by recent expression quantitative trait loci mapping were analyzed. Expression profiles of LanFTc1 and LanAGL8 (AGAMOUS-like 8) matched observed differences in flowering time between genotypes, highlighted by high induction after vernalization in the ku line. Moreover, these genes revealed altered circadian clock control in Pal line under short days. LanFD (FD) and LanCRLK1 (CALCIUM/CALMODULIN-REGULATED RECEPTOR-LIKE KINASE 1) were negatively responsive to vernalization in Ku and Pal lines but positively responsive or variable in ku, whereas LanUGT85A2 (UDP-GLUCOSYL TRANSFERASE 85A2) was significantly suppressed by vernalization in all lines. Such a pattern suggests the opposite regulation of these gene pairs in the vernalization pathway. LanCRLK1 and LanUGT85A2 are homologs of A. thaliana genes involved in the FLOWERING LOCUS C (FLC) vernalization pathway. Lupins, like many other legumes, do not have any FLC homologs. Therefore, candidate genes surveyed in this study, namely LanFTc1, LanAGL8, LanCRLK1, and LanUGT85A2, may constitute anchors for further elucidation of molecular components contributing to vernalization response in legumes.

Time trend analysis of some agroclimatic variables during the last half century over Iran

We assessed the trends of precipitation, maximum and minimum temperature (Tmax and Tmin), diurnal temperature range (DTR), water requirement of autumn-planted wheat and summer-cropped corn (CWRwheat and CWRcorn), and reference evapotranspiration (ET0) under climate change over Iran using the Mann–Kendall test in 1967–2012. The presence of change-point in the series was also studied by the Pettitt test. In order to determine the length of growing season of autumn-sown crop (GSAC) and growing season of summer-sown crop (GSSC), the temperature-based and soil water-based approaches were employed. The analyses for Tmax, DTR, precipitation, and ET0 series were carried out over the entire year, GSAC, GSSC, mid-GSSC (MGSSC), early GSAC (EGSAC), and late GSAC (LGSAC). Further, the Tmin analysis was performed during the January–February–March (JFM). Precipitation had a negative trend in EGSAC, LGSAC, and GSAC at most stations. However, a positive trend in precipitation was found during MGSSC and GSSC at approximately 74% of cases. An increasing trend was detected for Tmax (except for LGSAC and EGSAC) and Tmin in most investigated locations. Moreover, DTR exhibited a downward trend for most regions except in GSAC. Increased Tmin and reduced DTR, unlike elevated Tmax, seem to have positively influenced autumn-sown crops. At the majority of cases, there was an upward trend in ET0, CWRwheat, and CWRcorn. Such increase in CWR and ET0 appears to have placed pressure on water resources through enhancing irrigation demand. Unlike for precipitation, ET0, and Tmax, a significant change-point occurred within Tmin, DTR, and CWR series for most sites.

Processing Tomato–Durum Wheat Rotation under Integrated, Organic and Mulch-Based No-Tillage Organic Systems: Yield, N Balance and N Loss

In a 4-year study, the biannual crop rotation processing tomato–durum wheat was applied to three cropping systems: (i) an innovative organic coupled with no-tillage (ORG+) where an autumn-sown cover crop was terminated by roller-crimping and then followed by the direct transplantation of processing tomato onto the death-mulch cover; (ii) a traditional organic (ORG) with autumn-sown cover crop that was green manured and followed by processing tomato; and (iii) a conventional integrated low-input (INT) with bare soil during the fall–winter period prior to the processing tomato. N balance, yield and N leaching losses were determined. Innovative cropping techniques such as wheat–faba bean temporary intercropping and the direct transplantation of processing tomato into roll-crimped cover crop biomass were implemented in ORG+; the experiment was aimed at: (i) quantifying the N leaching losses; (ii) assessing the effect of N management on the yield and N utilization; and (iii) comparing the cropping system outputs (yield) in relation to extra-farm N sources (i.e., N coming from organic or synthetic fertilizers acquired from the market) and N losses. The effects of such innovations on important agroecological services such as yield and N recycling were assessed compared to those supplied by the other cropping systems. Independently from the soil management strategy (no till or inversion tillage), cover crops were found to be the key factor for increasing the internal N recycling of the agroecosystems and ORG+ needs a substantial improvement in terms of provisioning services (i.e., yield).

Market acceptability and economic losses due to new physiological disorders in papaya (Carica papayaL.)

Systematic field screening was conducted in four important papaya germplasm lines to observe the severity of bumpy fruit incidence. The study revealed that Pune Selection-3 (64.6 %) was most sensitive for bumpy fruit disorder. The lowest market acceptability and highest economic losses were also observed in Pune Selection-3 (Rs. 3.3 per kg and 11, 21, 580 per ha, respectively) due to highest incidence of bumpy fruit disorder as compared to other germplasm lines. Morphologically, the normal, disordered fruits or seeds are entirely different. The highest amount of deformed seeds/fruit (83.6 %) and economic loss (Rs. 84, 400 per ha) under fruit production for market were noticed during the month of February, while the lowest deformed seeds/fruit (2.7 %) were observed during December. Average deformed seeds/fruit were significantly higher in February harvested fruits as compared to other month’s harvested fruits. This is a first report for the incidences of vivipary and white seed disorders. The highest incidences of these seed disorders were observed during May (13.4 % and 75.7 %, respectively), whereas their lowest incidence was observed in February and March (10 % and 5 %, respectively). The highest economic loss (Rs. 53, 600 per ha) was observed in April, whereas the lowest while least during February (Rs. 16, 800 per ha) in autumn sown crop of Pusa Dwarf under seed production.

Screening and selection of faba beans (Vicia faba L.) for cold tolerance and comparison to wild relatives

Since autumn-sown faba beans possess several advantages including higher seed yield over the spring cultivars, the study was aimed to screen and select cold tolerant accessions of faba beans (Vicia faba L.) and compare these to wild species in the highland of the west Mediterranean region, Turkey. A total of 114 accessions of Vicia species including 109 accessions of faba bean, three accessions of narbon bean (V. narbonensis L.) and two accessions of V. montbretii Fisch. et C.A. Mey. were screened for cold tolerance at seedling stage in two successive years, 2005–2006 and 2006–2007 growth seasons. Accessions were evaluated for cold tolerance using a 1 (Highly cold tolerant)-5 (Highly cold susceptible) visual scale. Considerable variation was found for cold tolerance and some agronomical characteristics in faba beans. Wild relatives of faba bean were found to be more tolerant to cold than those of cultivated faba beans. Although some pigmented accessions were free from freezing damage at −9.6°C without snow cover, accessions with white flowers were damaged. The proposed screening technique could easily be used to evaluate many faba bean accessions for cold tolerance. To increase yield, it was concluded that the cold tolerant accessions with high yield could be grown as autumn-sown crop in the target environment.

Screening of Onion Seedlings for Resistance Against New Mexico Isolates OF FUSARIUM OXYSPORUM f. sp CEPAE

New Mexico onion fields face reduced plant stand due to killing of seedlings for autumn-sown crop due to Fusarium basal rot (FBR). The goal of this study was to screen FBR-resistant and FBR-susceptible seedlings of onion entries using multiple Fusarium oxysporum f. sp. cepae (FOC) isolates collected from onion production fields in New Mexico. Twenty seeds from eight onion entries each were placed on a moist paper towel inside a Petri plate with a 1 cm2 piece of mycelial plug from one FOC isolate. A total of 136 combinations of FOC isolates and onion entries were evaluated at 25°C for 20 days for two years and disease incidence was calculated. An analysis of variation demonstrated a significant interaction between FOC isolate and onion entry for FBR incidence. Onion entries ‘NuMex Chaco’ and ‘NuMex Crispy’ produced the greatest spread in FBR incidence values for the FOC isolates tested. FOC isolate ‘CSC 515’ was the best FOC isolate for future screenings based upon its high mean and variation of FBR incidence.

Habitat-Specific Population Growth of a Farmland Bird

BackgroundTo assess population persistence of species living in heterogeneous landscapes, the effects of habitat on reproduction and survival have to be investigated.Methodology/Principal FindingsWe used a matrix population model to estimate habitat-specific population growth rates for a population of northern wheatears Oenanthe oenanthe breeding in farmland consisting of a mosaic of distinct habitat (land use) types. Based on extensive long-term data on reproduction and survival, habitats characterised by tall field layers (spring- and autumn-sown crop fields, ungrazed grasslands) displayed negative stochastic population growth rates (log λs: −0.332, −0.429, −0.168, respectively), that were markedly lower than growth rates of habitats characterised by permanently short field layers (pastures grazed by cattle or horses, and farmyards, log λs: −0.056, +0.081, −0.059). Although habitats differed with respect to reproductive performance, differences in habitat-specific population growth were largely due to differences in adult and first-year survival rates, as shown by a life table response experiment (LTRE).Conclusions/SignificanceOur results show that estimation of survival rates is important for realistic assessments of habitat quality. Results also indicate that grazed grasslands and farmyards may act as source habitats, whereas crop fields and ungrazed grasslands with tall field layers may act as sink habitats. We suggest that the strong decline of northern wheatears in Swedish farmland may be linked to the corresponding observed loss of high quality breeding habitat, i.e. grazed semi-natural grasslands.

The effect of chlormequat chloride (CCC) application at the bolting stage on the flowering and seed production of lettuce plants previously treated with water or gibberellic acid (GA 3)

Lettuce plants were sprayed with gibberellin (GA 3) or water at the rosette (8-leaf) stage and subsequently with water or CCC (500 or 1500 ppm) at the onset of bolting. GA 3 induced rapid bolting and increased seed yield, but seed stalks were longer and thinner than those that had been sprayed with water at the same stage. Treatment with CCC (500 ppm) at bolting decreased the flower stalk height of plants that had been sprayed with water at the rosette stage, but not that of GA 3 treated plants. CCC (500 ppm) increased the number of inflorescence branches per plant as well as seed yield in the autumn sown crop, but had no effect on the winter sown crop. When a higher concentration of CCC (1500 ppm) was applied at bolting, flower stalk height decreased, irrespective of whether the plants had been previously treated with GA 3 or not, and seed stalk diameter increased. However, 1500 ppm CCC reduced the number of inflorescence branches per plant and mean seed yield. It is concluded therefore that although the application of 500 ppm CCC at the onset of bolting may increase seed yield in the autumn sown crop, this treatment does not improve the seed stalk strength (e.g. increasing diameter or reducing height) of GA 3 treated plants. On the other hand, whereas a higher concentration of CCC (1500 ppm) improves seed stalk characteristics, it reduces seed yield.

Effects of seed production and storage conditions on blackgrass (Alopecurus myosuroides) germination and shoot elongation

Blackgrass is a common winter annual grass weed in autumn-sown crop rotations in Atlantic European countries. Control with a minimum amount of herbicides in integrated cropping systems would be facilitated by modeling the effect of cropping systems on its demography. To develop the submodel relating weed seed bank to emerged seedlings, laboratory experiments were conducted to analyze and quantify seed germination and shoot elongation. These processes were studied as a function of environmental conditions during seed production (nitrogen availability, water deficit, plant density, and crop) and of seed characteristics (seed weight, harvest date, storage length, and dry-stored/soil-buried). Nonlinear equations relating germination and shoot elongation to time calculated as cumulated degree-days were fitted to the observed germination and shoot elongation data. These were used to estimate parameters for germination proportion and rate, as well as final shoot length and elongation rate. Recently harvested seeds germinated best and fastest when they were collected in spring crops compared with winter crops. Germination proportion and rate increased with seed storage length, especially for seeds collected in winter crops. Midgermination time decreased with seed weight and water deficit during seed production; it increased with nitrogen amounts available to the mother plants. Maximum shoot length increased with seed weight and plant density during seed production. It decreased with nitrogen availability to mother plants and with storage length, irrespective of whether the seeds were dry-stored or buried in soil. Elongation rate was highest for early- and fast-germinating seeds. Time to midelongation increased with maximum shoot length. These germination and preemergence growth models can now be combined with other submodels to develop a blackgrass emergence model.

Physiological postharvest responses of Matricaria (Matricaria recutita L.) flowers

Abstract Mechanically gathered fresh Matricaria ( Matricaria recutita L.) flowers had a very high respiration rate (average from six trials at 10°C: 999±134 W t −1 , at 20°C: 2438±289 W t −1 , and at 30°C: 4552±570 W t −1 ). These levels, comparatively high for medical or vegetable plants, were maintained throughout an 80-h postharvest period. A senescence-related decline was only observed at 10°C by 33.3%, at 20°C by 45.4% and at 30°C by 62.0% of their initial rate for each temperature level. Even at 30°C, no respiratory collapse occurred despite considerable senescence and strong wilting of the flowers. Spring-sown crops had significantly higher respiration rates at harvest (+86–333 W t −1 ) than the autumn-sown crop and maintained this difference until the end of 80 h storage. The senescence-associated decrease occurred more quickly at 20°C and even more so at 30°C in autumn-sown plants. The ensuing dry matter loss was relatively high (7.5%/80 h) as was transpiration (1.83% in 24 h) at 10°C. Constituents of Matricaria flowers decreased only slightly during 80 h postharvest storage: essential oils (up to 20%), chamazulene (10%), EN-IN-dicycloether (20%) and apigenine-7-glycoside (20%). The valuable (−)-α-bisabolol and its A and B oxidized forms, in contrast, responded rather differently at 10°C with losses between 10 and 80%. All these changes were primarily dependent on storage temperature and the annual growing conditions. Matricaria flowers need intensive and immediate postharvest treatment including ventilating, cooling or drying. The expected respiration heat release in these trials may be used for process calculations. The essential oils and most of the pharmaceutical constituents were best maintained in the flowers at 10°C; but for bisabolol and its oxides, 20°C and for dicycloether, 30°C are more favourable temperatures.

Occurrence of barley yellow mosaic and barley mild mosaic bymoviruses in Greece

In March 1991, large chlorotic patches appeared in an autumn-sown barley crop growing near Thessaloniki, Greece. Leaves had characteristic mosaic symptoms and immunosorbent electron microscopy and enzyme-linked immunosorbent assay confirmed the presence of both soil-borne mosaic viruses of barley, barley mild mosaic and barley yellow mosaic bymoviruses. In the following year, similar symptoms appeared in a crop at Souroti, 30 km east of Thessaloniki but the disease has not been found in other areas of Macedonia. This report is the first record of these viruses from Greece and is the most southerly European record.

The dry matter and nitrogen degradation of whole crop wheat cut at three stages of crop maturity

The in sacco degradability technique (Paine, Crawshaw and Barber (1982)) is a useful method to evaluate the dry matter and nitrogen degradation characteristics of a forage in the rumen. Little information is available on the DM and N degradability of whole crop wheat. In a previous paper substantial variations in the nutritive composition of fermented and urea treated whole crop wheat forages were observed with increasing crop maturity. These variations were ascribed to changes in botanical composition of the forage with increasing maturity, for example the increasing contribution of grain in the dry matter elevated the starch content of the forage (Hill and Leaver (1991)). Givens, Moss and Adamson (1993) stated that whole crop cereals comprised of a cell wall rich straw fraction and a starch rich grain fraction. Therefore it could be suggested that variation in the relative proportions of these fractions would influence the fractional rate of degradation of the forage. Evidence to support this hypothesis was presented in Givens, Moss, Adamson and Reeve (1992) by incubating each fraction individually. The experiment reported was designed to compare the effect of stage of crop maturity, ensiling and urea treatment on the degradability of DM and N of whole crop wheat forages incubated as a total forage.An autumn sown crop of wheat (var. fortress) was cut at three stages of maturity being; growth stage 49 (boot), 71 (early milk) and 89 (hard dough) and three treatments were applied to the harvested forage. The treatments were fresh forage as harvested, ensiled and urea treatment with 40 kg/tonne DM. Six mature sheep (mean liveweight 76.9 kg), each fitted with a rumen cannula were used in the degradation trial.

Growth and yield of white lupin (Lupinus albus) under Mediterranean conditions: effect of sowing date

Abstract The sowing date, which depends on climate and on genetic characteristics of the species and cultivars, has a marked influence on crop growth and yield. A 5-year study of white lupin ( L. albus ) was conducted under the Mediterranean conditions of southern Spain in order to determine the influence of autumn (October/November) and winter (December/January) sowing dates on growth and grain yield. The duration of the different growth stages and thermal time (base 4°C) were estimated for: emergence (V 0 ), initiation of flowering (R 1 ), end of flowering and beginning of pod filling (R 4 ), and harvest maturity (R 8 ). The accumulation of dry matter, leaf area index (LAI), leaf area duration (LAD), pod setting %, grain yield, yield % of the main stem and yield components (plants m −2 , pods plant −1 , seeds pod −1 , and mean seed mass) were also measured. A randomized block with four replications was used and an analysis of linear correlation between the parameters measured and path coefficients analysis between grain yield and its components was estimated. The complete growth period had an average duration of 222 days (2417 thermal units) in the case of the autumn-sown crop and 173 days (2096 thermal units) with winter sowing. The periods V 0 −R 1 and R 1 −R 4 were shorter in the case of winter sowing, due to the influence of vernalization, photoperiod and water shortage in spring. The accumulation of dry matter and grain yield was greater for autumn sowing (6110 kg ha −1 and 1868 kg ha −1 ) than for winter sowing (3810 kg ha −1 and 1178 kg ha −1 ), as were maximum LAI and LAD (2.2 and 171 days and 1.6 and 83 days, respectively). The number of pods plant −1 , mean seed mass and pods m −2 were the components most influenced by sowing date, showing significantly higher values in autumn. There was a positive correlation between yield and the number of pods m −2 and mean seed mass. Path coefficients analysis showed a marked direct effect of mean seed mass on the yield; indirect effects were negligible, with the exception of mean seed mass.

Soil metabolism of the herbicide napropamide in cereals, maize, sugar beet and vegetable field replacement crops

The metabolism of the herbicide napropamide has been studied in the field in the soil of replacement crops (cereals, corn, sugar beet, potato and several vegetables). Napropamide was soil applied in the autumn and the soil left fallow during the winter. Crops were sown in April of the following year and simulated the replacement crops that are grown in the event of failure of the first autumn-sown crop. Trials were made twice, i.e. during the 1987-1988 and 1988-1989 crop seasons. The soil metabolism of napropamide was also studied in a rose nursery. Napropamide was transformed by microbiological processes in the soil into the corresponding monoethylamide and acid. These compounds did not generally accumulate in the soil, and their individual concentrations did not exceed that of residual napropamide during the observed growing seasons. The kinetics, metabolic pathways and agricultural implications of the herbicide are briefly discussed.

Use of cluster analysis for identification and classification of farming systems in Qingyang County, Central North China

Cluster analysis by the average linkage method was used for the identification and classification of farming systems in Qingyang County on the Loess Plateau of Central North China. Data from 26 townships describing soci-agricultural parameters of farm households were standardised and a Pearson correlation matrix was constructed. Parameters with the highest correlation coefficients and largest standards of deviation were selected for cluster analysis. These were: proportion of slopeland, proportion of valley land, proportion of autumn sown crops per household, autumn sown crop yield (kg ha −1), grain yield (kg ha −1), number of draught animals per unit area and number of sheep per household. The resulting dendrogram identified three major farming system groups comprising three, one and three subsystems for groups I, II and III, respectively. Topography was the principal component for discerning the major groups and identified: hilly slopelands, hilly slopelands with valley and tablelands for farming system groups I, II and III, respectively. Subsequent farm surveys confirmed differences between two of the major farming system groups (I & III). Examination of labour input to crops, livestock and house activities between households in groups I and III revealed that unutilised manpower was 2·4 times higher in group III than in group I, thus confirming differences in the two farming systems. The classification method was useful in determining farming system boundaries and for selecting areas appropriate for the introduction of new technologies. It also showed potential for the introduction of a taxonomy system for identification of different farming systems.

Measured and estimated evapotranspiration from well-watered crops

Abstract Daily evapotranspiration (ET) measurements from the Bowen ratio-energy balance method are presented for an autumn-sown oat crop and a number of summer crops, all of which were well-watered. The accuracy of both the Penman, and Priestley & Taylor ET estimates were found similar, with errors of 15–20% for daily ET estimates. The Priestley & Taylor method is simpler as it only requires net radiation and temperature data, so it appears preferable. The empirical constant in this method, relating the“equilibrium ET” to ET was found to be 1.21 from data obtained over winter, spring, and summer for a range of crops in the Manawatu. Daylight, rather than 24 h net radiation, data were used in evaluating this constant giving a better-defined constant. Further, daylight net radiation is more accurately predicted than is the 24 h value. Neglect of the nocturnal latent heat flux was of little consequence. Longer term ET estimates, using the Priestley & Taylor method, with net radiation calculated from incoming...

Phasic development in field crops III. The pseudocereals, buckwheat and grain amaranth

The phasic development of a day-neutral cultivar of buckwheat and a short-day cultivar of grain amaranth were simulated using a model adapted from the long-day model described in Part II of this series. The model was fitted to data from serial sowings of both crops at Gatton in eastern Australia. Temperature has a non-linear effect on rate of development of both buckwheat and grain amaranth, and photoperiod has a non-linear effect on rate of amaranth development prior to anthesis. The estimated values of model parameters for buckwheat indicate that its rate of development both before and after anthesis responds with diminishing returns to temperature above a threshold of about 10°C. Above mean daily temperatures of 20°C, the rate of development is effectively constant and crop duration is about 60 days. In the case of grain amaranth the model indicates a threshold temperature of about 10°C throughout the life cycle, and before anthesis it shows a strong short-day response with a critical photoperiod of about 14 h. After anthesis there is no sensitivity to photoperiod. At a temperature of about 20°C and a photoperiod of about 12 h the crop duration is as short as 67 days. Yield and biomass of the little-researched grain amaranth crop were measured over five summer months. The highest seed yield (2.15 t/ha) was for a fast-maturing autumn-sown crop but both yield and growth rate were found to be lower than other C4 species grown at the same time. The adaptation of these pseudocereals in cropping systems is discussed in relation to the potentially short life cycles.

Sugar beet bolting in the root crop

SummarySugar beet bolting in the root crop was studied during nine growing seasons, under the extreme climatic conditions in which the autumn-sown crop grows in Southern Spain.Bolting is positively correlated with the number of days with minimum air temperatures ranging from 2 to 8 °C or with the number of days with mean temperatures between 8 °C and 13 °C.The occurrence of bolting is also affected by rainfall distribution in so far as it determines the date of seedling emergence.

Sowing sugar beet in autumn in England

SUMMARYExperiments in England from 1970 to 1973 investigated the possibility of extending the growing season and increasing yields of bolting resistant sugar beet by sowing in autumn rather than in spring. September-sown plants grew rapidly in spring and achieved a complete leaf cover by mid-June by which time they had intercepted 40 % of radiation incident since mid-April compared with 28 and 9% for crops sown on 13 October and 13 April respectively. By early June autumn-sown plants were 20 fold heavier than spring sown but this advantage was progressively lost with the onset of bolting. Root growth slowed as assimilates were diverted to stem and inflorescence growth. Delaying autumn sowing from late September until mid-October delayed and reduced the frequency of bolting, probably because of a shortening of the period when plants were sufficiently large to respond to cold. Cutting down bolting inflorescences at frequent intervals improved root growth of both bolters and non-bolters. However, yields from autumn sowing never exceeded those from spring sowing, the best yield from an autumn-sown crop was 6·1 t/ha of sugar which was similar to that of the spring-sown crop. To try to prevent bolting of overwintered plants the growth regulator ethephon was applied at 10000 mg a.i./l water sufficient to wet the foliage in mid-April. Growth was severely checked and 55 % of plants died. Of the remainder 25–30% fewer than in the untreated crop bolted but yields were 26–42 % less. Less concentrated doses of ethephon did not affect bolting.

The effect of fertilizers and harvest date on growth and yield of oilseed rape sown in autumn and spring

SummaryIn experiments at Sutton Bonington between 1967 and 1970, which tested 0–300 kg N/ha applied in spring, maximum oil yields of both autumn- and spring-sown oilseed rape were obtained by applying 200 kg N/ha. The seed-oil content was reduced by nitrogen application but only seriously when 300 kg/a was applied. Responses to high levels of potassium (180 rather than 60 kg K20/ha) were only obtained at 200 kg N/a. Successive increments of nitrogen from nil to 300 kg/ha improved plant growth, increasing leaf area and the dry weight of leaves and stems. The last increment from 200 to 300 kg N/ha was less effective and either reduced or did not affect pod production.In one experiment 300 kg N/ha stimulated husk growth, apparently at the expense of seed growth, with 200 kg/ha giving the highest proportion of pod dry matter as seed. More nitrogen always raised number of seeds per pod, but only increased seed weight in one autumn-sown experiment.Serial harvests of one experiment indicated that the maximum seed and oil yield was obtained by cutting plants before they were fully ripe, thus avoiding seed loss through pod shatter. The oil content of the bulk samples reached a peak about a week before maximum oil yield, probably because later-ripening seed did not reach full maturity. All nitrogen levels delayed flowering, but only the highest delayed maturity in the autumn-sown crop.