Oilseed Rape Harvest Research Articles

Climate Overrides Effects of Fertilizer and Straw Management as Controls of Nitrous Oxide Emissions After Oilseed Rape Harvest

Oilseed rape (Brassica napus L.) is an important bioenergy crop that contributes to the diversification of renewable energy supply and mitigation of fossil fuel CO2 emissions. Typical oilseed rape crop management includes the use of nitrogen (N) fertilizer and the incorporation of oilseed rape straw into soil after harvest. However, both management options risk increasing soil emissions of nitrous oxide (N2O). The aim of this 2-years field experiment was to identify the regulating factors of N cycling with emphasis on N2O emissions during the post-harvest period. As well as the N2O emission rates, soil ammonia (NH4+) and nitrate (NO3−) contents, crop residue and seed yield were also measured. Treatments included variation of fertilizer (non-fertilized, 90 and 180 kg N ha−1) and residue management (straw remaining, straw removal). Measured N2O emission data showed large intra- and inter-annual variations ranging from 0.5 (No-fert + str) to 1.0 kg N2O-N ha−1 (Fert-180 + str) in 2013 and from 4.1 (Fert-90 + str) to 7.3 kg N2O-N ha−1 (No-fert + str) in 2014. Cumulative N2O emissions showed that straw incorporation led to no difference or slightly reduced N2O emissions compared with treatments with straw removal, while N fertilization has no effect on post-harvest N2O emissions. A process-based model, CoupModel, was used to explain the large annual variation of N2O after calibration with measured environmental data. Both modeled and measured data suggest that soil water-filled pore space and temperature were the key factors controlling post-harvest N2O emissions, even though the model seemed to show a higher N2O response to the N fertilizer levels than our measured data. We conclude that straw incorporation in oilseed rape cropping is environmentally beneficial for mitigating N2O losses. The revealed importance of climate in regulating the emissions implies the value of multi-year measurements. Future studies should focus on new management practices to mitigate detrimental effects caused by global warming, for example by using cover crops.

Efficiency of disc harrow adjustment for stubble tillage quality and fuel consumption

The compact disc harrow due to post-harvest tillage is used to incorporate the stubble and plant residues into soil, to induce their decomposition and to increase mineralization. The high-cut winter rape stubble is often main challenge of clear disc harrowing, especially in clay loam soil at minimum expenditure of fuel consumption. The aim of this study was to find optimal tillage performances and determine the fuel consumption what required to achieve the preferred level of stubble tillage in loam and clay loam soil after winter oilseed rape harvest. The tillage quality and fuel consumption were investigated in dependence on harrow disc angle (10°, 15° and 20°), tillage depth (5 and 8 cm) and working speed (1.4; 1.9; 2.5; 3.1; 3.6 m∙s−1). The tractor “CASE 135″ was instrumented with data acquisition system and was used to measure fuel consumption, actual working speed and implement draft. Research developed the efficient adjustment of aggregate regime mode to the best soil structure and plant residue incorporation. The beneficial relationship was established by obtaining tillage quality level to fuel consumption, which varied from 2.6 to 5.9 L·ha−1 in depending of soil type (loam and clay loam). Based on research results, the optimal fuel consumption (2.85 L·ha−1) was identified at disk harrow adjustment: disc angle 10°, working speed 3.5 m∙s-1 on both soils, but in different tillage depth 8 cm on loam and 5 cm on clay loam soil.

Temporal Differentiation of Crop Growth as One of the Drivers of Intercropping Yield Advantage

Intercropping studies usually focus on yield advantage and interspecific interactions but few quantify temporal niche differentiation and its relationship with intercropping yield advantage. A field experiment conducted in northwest China in 2013 and 2014 examined four intercropping systems (oilseed rape/maize, oilseed rape/soybean, potato/maize, and soybean/potato) and the corresponding monocultures. Total dry matter data collected every 20 d after maize emergence were fitted to logistic models to investigate the temporal dynamics of crop growth and interspecific interactions. All four intercropping systems showed significant yield advantages. Temporal niche complementarity between intercropped species was due to differences in sowing and harvesting dates or the time taken to reach maximum daily growth rate or both. Interspecific interactions between intercropped species amplified temporal niche differentiation as indicated by postponement of the time taken to reach maximum daily growth rate of late-maturing crops (i.e. 21 to 41 days in maize associated with oilseed rape or potato). Growth trajectories of intercropped maize or soybean recovered after the oilseed rape harvest to the same values as in their monoculture on a per plant basis. Amplified niche differentiation between crop species depends on the identity of neighboring species whose relative growth rate is crucial in determining the differentiation.

Seed losses during the harvesting of oilseed rape (Brassica napus L.) at on-farm scale

In the Italian environments, the rapeseed (Brassica napus L.) is subjected, at ripening, to a seed shattering causing significant losses that reduce the yield and increase the oilseed rape seedbank in the soil. Meteorological events and mechanical harvesting are the main factors affecting the extent of seed dispersal. Lacking the availability of works investigating the actual losses during the harvest at large scale, the Consiglio per la sperimentazione e la ricerca in agricoltura, Unità di ricerca per l’ingegneria agraria (CRA-ING) has conducted a study in order to determine the effective seed losses at on-farm scale. The amount of losses of two combine headers, traditional for wheat and specific for oilseed rape harvest, was compared. The rapeseed header had a hydraulic sliding cut-bar and two vertical electric blade on both sides in order to reduce the pulling and tearing action between the cut-off plants and those still standing. The seed losses were evaluated before and during the harvesting by using plastic trays placed on the ground within the crop rows. The trays were arranged in a layout allowing the estimation of the seed losses of three different sectors of the combine headers. The results have demonstrated that, at farm level, the use of a specific oilseed rape header adapted and optimized for the crop requirements allows to obtain a level of seed losses (0,97% of total production), below the values reported in literature. For rapeseed, the higher losses are localized at the final parts of the head, where the plants are strictly intertwined.

A new mycoparasite, Aspergillus sp. ASP-4, parasitizes the sclerotia of Sclerotinia sclerotiorum

A species of Aspergillus (strain ASP-4), belonging to the Aspergillus aculeatus clade of the black aspergilli, which can parasitize and destroy the sclerotia of the economically important plant pathogen Sclerotinia sclerotiorum was isolated from a field plot where oilseed rape had been planted for nearly 20 years. This is the first time that a member of Aspergillus section Nigri has been described as a mycoparasite. Inoculation experiments of S. sclerotiorum sclerotia were conducted in both the laboratory and field plots over a three year period. The results clearly show that the effect of this mycoparasite on reducing numbers of germinating sclerotia and subsequent spread of this pathogen is highly significant. Therefore, Aspergillus sp. ASP-4 has the potential to be an important biocontrol agent. In addition, since Aspergillus sp. ASP-4 infects sclerotia, the application time and method for the prevention and control of Sclerotinia stem rot of oilseed rape can be made relatively easy compared to the critical timing of fungicide application during the early to mid-flowering season, as fungal spores can be sprayed directly on to soils after oilseed rape harvest.

Seed losses during the harvesting of oilseed rape (Brassica napus L.) at on-farm scale

In the Italian environments, the rapeseed (Brassica napus L.) is subjected, at ripening, to a seed shattering causing significant losses that reduce the yield and increase the oilseed rape seedbank in the soil. Meteorological events and mechanical harvesting are the main factors affecting the extent of seed dispersal. Lacking the availability of works investigating the actual losses during the harvest at large scale, the Consiglio per la sperimentazione e la ricerca in agricoltura, Unità di ricerca per l’ingegneria agraria (CRA-ING) has conducted a study in order to determine the effective seed losses at on-farm scale. The amount of losses of two combine headers, traditional for wheat and specific for oilseed rape harvest, was compared. The rapeseed header had a hydraulic sliding cut-bar and two vertical electric blade on both sides in order to reduce the pulling and tearing action between the cut-off plants and those still standing. The seed losses were evaluated before and during the harvesting by using plastic trays placed on the ground within the crop rows. The trays were arranged in a layout allowing the estimation of the seed losses of three different sectors of the combine headers. The results have demonstrated that, at farm level, the use of a specific oilseed rape header adapted and optimized for the crop requirements allows to obtain a level of seed losses (0,97% of total production), below the values reported in literature. For rapeseed, the higher losses are localized at the final parts of the head, where the plants are strictly intertwined.

The harvest of oilseed rape (Brassica napus L.): The effective yield losses at on-farm scale in the Italian area

The oilseed rape is an interesting oil crop for energy production. In Italy there are many potential available areas for crop cultivation thanks to adequate rainfall and mild winters. The diffusion of rapeseed is restrained by the significant seed losses caused by mechanical harvesting and meteorological events. Aim of the study was to determine the effective seed losses taking into account all the phases of harvesting, from ripening to harvest, at on-farm scale. The combine used for mechanical harvester was equipped with two different header: a grain head and a specific oilseed rape head. The lost seed was collected by appropriate trays inserted between the crop rows on the ground, before and during the harvesting. The specific oilseed rape head permitted a general reduction of the seed losses, below the ranges reported in literature, and a more precise determination of the point where the losses were higher, as the terminus parts of the head.

Competitiveness and yield impact of volunteer oilseed rape (Brassica napus) in winter and spring wheat (Triticum aestivum)

Volunteer oilseed rape is a relevant weed in many crop rotations due to seed persistence and dormancy. With the intro-duction of imidazolinone-tolerant oilseed rape varieties in Europe, herbicide-based control strategies of volunteers in cereals may become ineffective in the future. Experiments were conducted on experimental fields and in outdoor pots in Bingen (Germany) to quantify the effect of oilseed rape volunteers on yield and quality parameters of wheat. To simulate competition, oilseed rape was sown into wheat plots at a range of 2 to 320 plants m−2. Both spring and winter varieties of oilseed rape and wheat were used in the experiments. Crop yield parameter were expressed as the number of heads m−2, net yield as kg ha−1 and hectolitre−1 weight. Wheat moisture content, percentage of dockage, wheat thousand-kernel weight, and crude protein content were determined. Significant negative correlations were detected between the yield parameters heads m−2 and yield on the one hand, and oilseed rape density on the other hand. Moisture content of wheat and percentage of dockage were positively correlated with the volunteer density. No clear correlation was found between volunteer oilseed rape density and thousand-kernel weight, hectolitre weight and crude protein content of wheat. The highest volunteer density of 261 plants m−2 caused a maximum yield loss of 68% in winter wheat. Based on a non-linear regression analysis, a single volunteer oilseed rape plant m−2 is able to cause a yield loss of 0.74 to 1.61% in the field, which corresponds to 26.3 kg ha−1 (spring oilseed rape in spring wheat (SOSR × SW)) and 147.3 kg ha−1 (winter oilseed rape in winter wheat (WOSR×WW)), respectively. However, the introduction of imidazolinone-tolerant oilseed rape varieties will challenge farmers in terms of volunteer management. Control of volunteers is important to reduce yield losses. Accurate, delayed tillage after oilseed rape harvest and control of imidazolinone-tolerant volunteers with herbicides with other modes of action than those grouped into HRAC B will contribute to the successful avoidance and removal of imidazolinone-tolerant volunteers from subsequent crops.

Seed spillage from grain trailers on road verges during oilseed rape harvest: an experimental survey.

ContextAnthropogenic vectors enhance the natural dispersal capacity of plant seeds significantly in terms of quantity and distance. Human-mediated seed dispersal (i.e. anthropochory) greatly increases the dispersal of crop species across agroecosystems. In the case of oilseed rape (OSR), spillage of seeds from grain trailers during harvest has never been quantified.MethodsOur experimental approach involved establishing 85 seed trap-sites on the road verges of an agricultural area around the grain silo of Selommes (Loir-et-Cher, France). We recorded OSR spillage during harvest and applied a linear model to the data.ResultsThe amount of seed spilled was related positively to the area of the OSR fields served by the road, whereas the amount of seed spilled decreased with other variables, such as distance from the trap-site to the verge of the road and to the nearest field.The distance to the grain silo, through local and regional effects, affected seed loss. Local effects from fields adjacent to the road resulted in a cumulative spillage on one-lane roads. On two-lane roads, spillage was nearly constant whatever the distance to the silo due to a mixture of these local effects and of grain trailers that joined the road from more distant fields.From the data, we predicted the number of seeds lost from grain trailers on one road verge in the study area. We predicted a total spillage of 2.05×106 seeds (±4.76×105) along the road length, which represented a mean of 404±94 seeds per m2.ConclusionContainment of OSR seeds will always be challenging. However, seed spillage could be reduced if grain trailers were covered and filled with less seed. Reducing distances travelled between fields and silos could also limit seed loss.

Efficient N management using winter oilseed rape. A review

During the last decades the acreage of winter oilseed rape has been increased considerably in Europe. Rapeseed can take up a large amount of nitrogen before winter (>100 kg N/ha) and thus prevent nitrate leaching and pollution. Winter wheat is often grown subsequently, using oilseed rape as a favorable preceding crop. However, under wheat large nitrogen losses via leaching are frequently observed in humid climates during winter, mainly due to high amounts of soil mineral N available in fall and the small N uptake in fall of wheat as a subsequent crop. The low N offtake by the seeds results in a lower N-use efficiency and increases the N surpluses (>90 kg N/ha) compared with winter wheat (c. 40 kg N/ha). In addition, a large soil N pool increases the risk of N2O emission, with its impact on climate change. In our review we discuss several options to increase nitrogen-use efficiency in oilseed rape-based cropping systems ranging from optimizing N fertilization practices to options arising from adopted tillage practices and crop rotation. N application in fall normally increases dry matter accumulation and N uptake before winter. However, because of its limited yield effects in most situations, fall N supply also boosts N surpluses. N fertilization in spring exceeding the need of the crop for optimal seed yield increases the risk of N leaching and decreases the farmer’s net revenue. Considering the amount of N taken up by the canopy before the first spring application improves the determination of the optimal spring N supply. Measuring canopy N in fall gave the best results. At the cropping system level, time and intensity of soil tillage after the harvest of oilseed rape has concurrent goals of controlling volunteer rape, and achieving a successful establishment of the following crop, but avoiding an increased N mineralization. Changing the crop rotation by growing catch crops which prevent N from leaching is very effective in reducing N losses from the system by >40%. However, the economic losses from growing a usually less profitable spring crop probably limit the acceptance by farmers. Despite the problems addressed above, looking at the whole cropping system, oilseed rape is indispensable because of its beneficial effects on yield levels and nitrogen-use efficiency of following cereals, especially wheat, because alternative crops are often not realistic alternatives.

Evaluation of different agronomic strategies to reduce nitrate leaching after winter oilseed rape (Brassica napus L.) using a simulation model

Winter oilseed rape (OSR) demands high levels of N fertilizer, often exceeding 200 kg N ha−1. Large amounts of residual soil mineral nitrogen (SMN) after harvest are regularly observed, and therefore N leaching during the percolation period over winter is increased. In this study agronomic strategies (fertilization level, crop rotation, tillage intensity) to control nitrate leaching after OSR were investigated by combining field measurements (soil mineral nitrogen, soil water content, crop N uptake) of a 2-year trial and another 5-year field trial with simulation modeling. The crop-soil model uses a daily time step and was built from existing and partly refined submodels for soil water dynamics, mineralization processes, and N uptake. It was used to reproduce the complex processes of the N dynamics and to calculate N concentration in the leachate and total volume of percolation water. Some parameters values were thereby newly identified based on the agreement between measured data and model results. Although SMN in the 60–90 cm layer was overestimated, the model could reproduce the measured data with an acceptable degree of accuracy. Overfertilization of OSR increased N leaching and therefore the precise calculation of N fertilizer doses is a first step towards prevent N leaching. Compared to ploughing, minimum tillage decreased N leaching when winter wheat was grown as the subsequent crop. Volunteer OSR and Phacelia tanacetifolia were grown as catch crops after OSR harvest. N leaching could be decreased especially when Phacelia was grown, but nitrate concentrations in the drainage water were higher and exceeded the European Union (EU) threshold for drinking water when volunteer OSR was grown. The results of this study provide strong evidence that reduced tillage or growing of noncruciferous catch crops decrease N leaching and may be used as an agricultural measure to prevent N pollution.

Adventitious presence of other varieties in oilseed rape (Brassica napus) from seed banks and certified seed

AbstractTo obtain information on possible sources of contamination of the seed harvest of oilseed rape (Brassica napus L., spp. napus) by other varieties (adventitious presence), we investigated the purity of certified seed lots; the abundance and origin of volunteers; and longevity and origin of seeds in the soil seed-bank. This information was acquired through DNA analysis of volunteers collected in the field and seedlings derived from the soil seed-bank. DNA profiles of the volunteers and seedlings were obtained using Inter Simple Sequence Repeat (ISSR) markers, and the profiles were compared with ISSR profiles from an assortment of 14 of the most commonly cultivated oilseed rape varieties from 1985 to 2004. This comparison was performed using the assignment program, AFLPOP. The age of the seed bank germinating to become volunteers was assumed from information on previously cultivated oilseed rape varieties at the site and the year of cultivation. The results showed that plants or seeds belonged to varieties cultivated at the site 4–17 years earlier, suggesting a long persistence of volunteer populations. High volunteer frequencies (6%, 29% and 32%) were found in the three oilseed rape fields analysed and, from soil cores, their soil seed-bank was estimated to be 50–100 seeds m− 2. The ISSR analysis of the 14 reference varieties showed that three of the certified seed lots contained other varieties above the allowed threshold. Our findings are discussed in the context of the coexistence between GM (genetically modified) and non-GM oilseed rape, and future levels of seed purity.

Modelling seedbank dynamics of volunteer oilseed rape ( Brassica napus)

A simple mechanistic model is presented which describes population dynamics of volunteer oilseed rape within a field. The model calculates the number of volunteers appearing in each crop and the seedbank after each crop. The main input variables are harvesting losses when the crop is oilseed rape, crop rotation, soil cultivation, soil moisture content within the arable soil layer and the level of volunteer control in each crop in the rotation. Simulation studies suggest that there are a number of agronomic means of minimising volunteer oilseed rape populations effectively. The amount of harvesting losses, the time span between oilseed rape harvest and the first tillage operation post-harvest, the efficiency of controlling oilseed rape in other crops and rotation itself are key components of a programme for ensuring that volunteer oilseed rape populations are minimised. Simulation runs showed that the proportion of volunteer plants within a crop of oilseed rape will be relatively high, even though the density of volunteers is low in other crops. This contamination of a rape crop could be a particular problem in the context of the cultivation of genetically modified rape. The model would benefit from improved estimates of some parameters. More data are particularly necessary on the long-term development of a seedbank of oilseed rape and the relationship between the size of the seedbank and the number of volunteers in various crops.

Variation in the development of secondary dormancy in oilseed rape genotypes under conditions of stress

Summary A substantial amount of seed is left in the fields before and during harvest of oilseed rape. Although this crop exhibits little or no primary dormancy, the absence of certain environmental cues that promote germination of imbibed seeds induces secondary dormancy. The work reported investigated the extent to which environmental stress conditions, including osmotic stress, low oxygen stress and anaerobiosis, induce secondary dormancy in oilseed rape, and examined the variation in development of secondary dormancy between and within genotypes. Osmotic stress was most effective in inducing dormancy. Anaerobic treatment produced very few dormant seeds, as did an atmosphere low in oxygen and high in nitrogen. The development of secondary dormancy under osmotic stress varied considerably between and within genotypes. Dormancy ranged from almost zero to about 60% for winter genotypes and about 85% for spring types. Within genotypes, variations occurred between seed lots and years of harvest. Temperature variations affected the percentage of dormant seeds. More dormant seeds were likely to be produced with incubation under water stress at 20 °C than at 12 °C. In winter genotypes, fewer dormant seeds were produced when incubation temperature and germination test temperatures differed. Thus, incubating at 20 °C and 12 °C, followed by germination tests at 20 °C and 12 °C, respectively, produced most dormant seeds. Also, in the winter genotypes, the potential development of secondary dormancy was positively correlated with the pattern and speed of germination of untreated seeds.

Turnover of residual 15N-labelled fertilizer N in soil following harvest of oilseed rape (t Brassica napus L.)

We studied the fate of 15N-labelled fertilizer nitrogen in a sandy loam soil after harvest of winter oilseed rape (Brassica napus L. cv. Ceres) given 100 or 200 kg N ha-1 in spring, with or without irrigation. Our main objective was to quantify the temporal variations of the soil mineral N, the extractable soil organic N and soil microbial biomass N, and fertilizer derived N in these pools during autumn and winter. Nitrogen use efficiency of the oilseed rape crop varied from 47% of applied N in the 100N, irrigated treatment to 34% in the 200N, non-irrigated treatment. However, only in the latter treatment did we find significantly higher fertilizer derived soil mineral N than in the three other treatments which all had low soil mineral N contents at the first sampling after harvest (8 days after stubble tillage). Between 31% and 42% of the applied N could not be accounted for in the harvested plants or 0-15 cm soil layer at this first sampling. Over the following autumn and winter none of the remaining fertilizer derived soil N was lost from the 0–5 cm depth, but from the 5–15 cm depth a marked proportion of N derived from fertilizer was lost, probably by leaching. Negligible amounts of fertilizer derived extractable soil organic and mineral N (<1 kg N ha-1, 0-15 cm) were found in all treatments after the first sampling.