Rape Harvest Research Articles

Expansion of Field Margin Size Mitigate the Hazard of Rotary Tillage to Earthworm in Rice-Rape Rotation System

Field margin (FM) provides refuges for earthworm survival in rape-rice system after flooding, while the effects of FM with different size on earthworm in arable field (AF) is unclear. In this study, we investigated the effects of different FM sizes, a conventional size (FM I) and three expanding sizes (FM II, FM III, FM IV), on earthworm population characteristics in FM and AF. The results showed that the mean abundance of earthworm under the expanding sizes at 1 day and 60 day of flooding after rape harvest was 16.5 and 20.2 times higher than that of FM I, respectively. After stopping flooding, juveniles first migrated from FM to AF, whereas more than half of them were killed by subsequent rotary tillage, and the mortality decreased with expanding FM size. Subsequently, expanding FM sizes promoted earthworm to distribute evenly through the AF at faster speeds. At rape maturity, the mean abundance and total biomass of earthworm of AF under expanding FM sizes were significantly greater than that of FM I, and this positive effect increased with expanding FM size. The results indicated that expanding FM size can mitigate the hazard of rotary tillage to earthworm and promote rapid recovery of earthworm population in AF.

Effect of tillage implement (spring tine cultivator, disc harrow), soil texture, forward speed and tillage depth on fuel consumption and tillage quality

Over the years, tillage became less intense due to environmental safety requirements in order to minimize fuel and labour time. Mostly, this is achieved by reducing the depth of tillage. However, highly cut winter rape stubble is the main challenge for reduced tillage to prepare clear soil, especially as the summer droughts intensify. The aim of this study was to determine the optimal tillage performances of the spring tine cultivator and compact disc harrow and establish the fuel consumption required to achieve the preferred level of soil structure formation and residue incorporation on loam and clay loam soil after a rape harvest. The fuel consumption depends on the desired level of soil tillage intensity, implement type, tillage depth (5 and 8 cm), and forward speed (1.4, 1.9, 2.5, 3.1, and 3.6 m∙s-1). The tractor “CASE IH 135” was instrumented with an additional data acquisition system and was used to perform the indicators of stubble tillage. The research examines the dependence of the tractor-implement regime mode on the soil aggregate ratio, which varied from 0.10 to 0.21, and the residue interblending ratio, which varied from 0.60 to 0.96. The relationship was established by obtaining the tillage quality level and reduced fuel consumption, which varied from 3.4 to 5.9 L·ha-1, depending on soil type. Minimization of fuel consumption and sufficient quality of oilseed rape stubble cultivation was achieved by reducing the depth but not the speed of tillage.

Straw residue incorporation and potassium fertilization enhances soil aggregate stability by altering soil content of iron oxide and organic carbon in a rice–rape cropping system

AbstractBoth iron (Fe) oxide and soil organic carbon (SOC) content, among other factors, drive the development and subsequent stability of soil aggregates. However, the mechanism of these drivers in paddy‐upland rotation systems with straw residue incorporation is not well understood. In this multiyear (2011–2017) trial, we sought to study the factors which drive the stability of soil aggregates in such a rice‐rape (RR) agronomic system. In order to examine the effect of straw residue incorporation and potassium fertilization on soil aggregation dynamics, we divided our trial into four treatments: inorganic phosphorus (P) and nitrogen (N) fertilizer; inorganic NPK fertilizer; inorganic NP fertilizer plus straw residue; and inorganic NPK fertilizer plus straw residue. Treatments which incorporated straw residue significantly increased both the geometric mean diameter (GMD) and the mean weight diameter (MWD) of soil aggregates. Soil aggregate stability was greater after rape harvest than after rice harvest, while SOC shows the opposite trend. Straw residue incorporation increased the SOC and, specifically, concentrations of aliphatic‐C and aromatic‐C, particularly in aggregates greater than 0.25 mm. Straw residue addition significantly increased both the amorphous (Feo) and complex iron oxide (Fep) contents of soil. In both bulk soil and in aggregates greater than 5 mm, SOC and Fep were positively correlated with MWD, while in aggregates less than 5 mm, Feo was positively correlated with MWD. Overall, we suggest that the increased concentrations of SOC, alkane‐C, Feo, and Fep in soils after incorporation of straw residue were responsible for increasing soil aggregate stability.

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.

Residual bioavailability of nickel in nickel spiked sandy loam soil: Impact on swede rape (Brassica napus L.) growth and uptake of micronutrients

In screenhouse experiment, a sandy loam soil (Typic Ustipsamment) was spiked with six levels of nickel (Ni) viz. 0, 5, 10, 25, 50, 100 mg kg−1 soil to investigate residual bioavailability of Ni and its impact on Swede rape grown after rice. The residual effect of Ni was investigated on growth of swede rape and uptake of micronutrients by it. Swede rape [Brassica napus (L.) Czern.] was grown for 60 days for dry matter accumulation, content of nickel and micronutrients. A linear and significant decrease in dry matter yield (DMY) was observed with the residual effect emanating from each successive level of Ni contamination except for that observed under 5 mg kg−1 Ni spiking. Maximum reduction in DMY (50%) was observed at 100 mg Ni kg−1 soil contamination level as compared to control. Nickel uptake by Swede rape increased substantially from 15.3 pg pot−1 in control to 397.8 pg pot−1 at 100 mg Ni kg−1 soil. Nickel spiking reduced the concentration of micronutrients in Swede rape, but significant reduction occurred only for iron at levels higher than 10 mg kg−1 soil. However, the uptake of iron, manganese, and zinc registered a significant decline at 5 mg Ni kg−1 soil and successive higher rates. Even after the harvest of Swede rape, 14.2 mg Ni kg−1 soil remained in the soil spiked with 100 mg Ni kg−1. This suggests that several cropping cycles would be required to make a contaminated soil safe for cultivation.

Development and experiments on reel with improved tine trajectory for harvesting oilseed rape

Crops with branching characteristics, such as rapeseed, are difficult to harvest owing to their specific plant geometry. To solve this problem, an harvesting reel with improved tine trajectory, considering the reel working process and a function suitable for oilseed rape, is proposed in this study. The improved tine, of which angle can be continuously adjusted to adapt to the plant structure and meet the operating requirements of the reel in the stages of pushing the reel into the crops, feeding plants into the auger, and releasing the reel. The kinematics of the tine trajectory between the new and standard reels were calculated and a simulation comparative analysis was performed, which proved that the new reel satisfies the theoretical requirements. Single-factor field experiments were conducted for the two types of reels. The test results demonstrated that the proposed reel has a lower header loss rate and is significantly affected by the reel speed than the reel height or machine forward speed. According to the multivariate orthogonal results, the combination of optimal parameters with minimum loss rate yielded a reel rotational speed of 1.88 rad s −1 , machine speed of 0.6 m s −1 , and reel vertical height of 1100 mm. The actual loss rate was found to authentically decrease to 1.04% in the supplementary field test under this condition, which verified that the parameters are reasonable. This study combines experiments and trajectory analysis to explain the advantages of the improved reel and provide a new study direction of reducing rapeseed harvesting losses. • Designed an reel with improved tine trajectory suitable for harvesting rapeseed. • Simulation analysis proved the improved reel is more favorable for rape harvest. • Field comparative experiments proved the improved reel has a lower header loss.

Current status and prospect of research on combine harvester header for rape

Rapeseed is one of the most important oil-bearing crops in China. Because of its poor efficiency, the planting area is in a trend of declining year by year. In order to change the status quo of low efficiency and stimulate farmers’ enthusiasm for planting oilseed rape, it is of great significance to vigorously promote the mechanized harvest in the process of rapeseed production. The rape header is an important part of the rape combine harvester. It is different from the header structure of common rice and wheat combine harvesters, and the header depth is larger. At the same time, in order to solve the problem of dense branches and cross-linking of rapeseed, in addition to the main cutter, reel and screw conveyor, the rape header also needs to be equipped with a vertical splitting cutter on the side. In this way, the entangled branches are cut and the loss of shattering can be reduced. Head loss accounts for a considerable proportion of the total loss during the rape harvest. By reasonably configuring the structure of the rape header and optimizing the working parameters, the vibration of the header and the power consumption of the header can be reduced, and the work efficiency can be improved. It is of great significance to reduce the mechanical harvest loss of rape and increase the efficiency of rape planting. This article introduces the current status and progress of the research on the working structure of the rape header at home and abroad. Point out the existing problems and put forward suggestions for the development of rape header in the future.

Effect of Vibration on Rapeseed Header Loss and Optimization of Header Frame

HighlightsThe relationship of vibration and header loss was studied by multi-point vibration measurement and loss collection test.There was an approximately linear positive correlation between total header vibration and total rapeseed header loss.The header frame was analyzed and optimized through modal simulation and testing.The total rapeseed header loss of the improved header was reduced by 33.2% to 46.9%.Abstract. In view of the current large rapeseed header losses of rape combine harvesters, the effects of the header on rapeseed header loss were studied from the perspective of vibration. First, the vibrations at various measuring points on the header during rape harvest were studied using a data acquisition and analysis system while performing collection tests of rapeseed header loss with the sample slot method. The relationships between total header vibration and total rapeseed header loss and between vertical cutter vibration and rapeseed vertical cutter loss were shown to have a positive correlation, and they all increased with the increase in engine speed. Vertical cutter loss accounted for 31.2% to 42.4% of the total rapeseed header loss. Modal analysis and optimization of the header frame were then performed by simulation and test. The natural frequencies of the first-order and second-order modes of the optimized header were increased, and the possibility of resonance with other working parts was eliminated. Finally, the improved header was tested during rape harvest. The results showed that the total vibration of the improved header was reduced by 19.9% to 43.9%, and the total rapeseed header loss was reduced by 33.2% to 46.9%. The vertical cutter vibration was reduced by 30.5% to 49.8%, and the rapeseed vertical cutter loss was reduced by 20.8% to 34.7%. In addition, the vibration and rapeseed loss of the improved header had relatively slow rates of increase with the increase in engine speed. The method of reducing rapeseed loss by reducing the header vibration achieved an obvious and positive effect. Keywords: Frame optimization, Modal analysis, Rape combine harvester, Rapeseed header loss, Vibration.

Application of inorganic passivators reduced Cd contents in brown rice in oilseed rape-rice rotation under Cd contaminated soil

Immobilization of heavy metals by the application of chemical amendments is an eco-friendly, economical and effective method to remediate cadmium (Cd) -contaminated soils. Field experiments were conducted during 2016–2018 following oilseed rape-rice rotation with the application of inorganic passivators i.e., slaked lime (CaOH2>95%) and sepiolite (SiO2>50%, MgO>20%). The experimental treatments were comprised of: rice planting in winter fallow and without passivator (F-PA0); fallow with slaked lime (F-PA1); fallow with sepiolite (F-PA2); oilseed rape–rice rotation without passivator (R-PA0); rotation with slaked lime (R-PA1); and rotation with sepiolite (R-PA2). The slaked lime and sepiolite were applied after the harvest of rape at 2000 and 5000 kg ha−1, respectively. Results revealed that the Cd contents were reduced by 47.44–49.03% in brown rice for F-PA2 and 9.54–42.66% in soil for R-PA2. The superoxide dismutase (SOD) activity was decreased by 10.65–17.98%, the malondialdehyde (MDA) contents were reduced by 28.57% whereas the proline content was decreased by 32.61% under R-PA2. In addition, the filled grain percentage was improved by 6.87% (F-PA2) and 3.70% (R-PA1), respectively. Overall, rice sown after oilseed rape gave better yields than sown after fallow fields while application of slaked lime and sepiolite as passivator could be a potential management option to grow crops in metal polluted soils.

Ground beetles (Coleoptera: Carabidae) diversity from harvested oilseed rape fields (Brassica napus L.) in Southern Bulgaria

This study aimed at clarifying the species composition and ecological structure of carabid communities, in oilseed rape fields after rape harvest. Field work was carried out in 2018. Pitfall traps (5 in each site) were set in 10 sampling sites in Thracean Lowland and Sarnena Sredna Gora Mts. Captured beetles belonged to 66 species and 24 genera, representing 9% of the species and 19% of the ground beetle genera occurring in Bulgaria. The most diverse was genus Harpalus Latreille, 1802 (15 species), followed by the genera Amara Zimmermann, 1832 (7 species), Microlestes Schmidt-Goebel, 1846 (6 species) and Parophonus Ganglbauer, 1891 (5 species). Five species were new for the region of the Thracean Lowland: Amara (Bradytus) consularis (Duftschmid, 1812), Harpalus (Harpalus) caspius (Steven, 1806), H. (Pseudoophonus) calceatus (Duftschmid, 1812), Microlestes negrita negrita (Wollaston, 1854), Tachyura (Tachyura) parvula (Dejean, 1831). Three species: Amara (Zezea) fulvipes (Audinet-Serville, 1821), A. (Zezea) chaudoiri incognita Fassati, 1946 and Diachromus germanus (Linnaeus, 1758) were new records for the region of the Sarnena Gora. Seven species were new for the whole Sredna Gora Mts.: Acinopus (Acinopus) picipes (Olivier, 1795), A. (Oedematicus) megacephalus (P. Rossi, 1794), Carterus (Carterus) dama (P. Rossi, 1792), Harpalus (Harpalus) flavicornis flavicornis Dejean, 1829, H. (Pseudoophonus) griseus (Panzer, 1796), Licinus (Licinus) depressus (Paykull, 1790) and Microlestes maurus maurus (Sturm, 1827). Genera Acinopus Dejean, 1821, Carterus Dejean, 1830 and Licinus Latreille, 1802 were new geographic records for the Sredna Gora Mts. Twelve life form categories were established (7 zoophagous and 6 mixophytophagous). The analysis of the life forms showed a slight predominance of the mixophytophages (38 species; 58%) over the zoophages (28 species; 42%). There were no constant species occurring in all sampling sites (with 100% occurrence). Thirteen species appeared after the harvest (they were absent during the flowering and ripening of the rape), forty-four species disappeared (they were present during flowering and ripening), and twenty-nine species were present in all stages.

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.

Effects of organic carbon and iron oxides on soil aggregate stability under different tillage systems in a rice–rape cropping system

Studies of soil organic carbon (SOC) and iron oxides are crucial for understanding soil aggregate formation and stability in paddy–upland rotation systems. Many of these soils contain large amounts of SOC and iron oxides, which may be lost due to changes in the hydrothermal conditions. This study primarily investigated the dynamics of aggregates and soil binders (SOC and iron oxides) after rice and rape harvests under four treatments: conventional tillage without straw returning (T1), conventional tillage with straw returning (T2), no-tillage without straw returning (T3), and no-tillage with straw returning (T4) in paddy soils. The percentage content of >5 mm aggregates was higher than that of other aggregates in all treatments, except T1 and T2 after the rape harvest. T4 significantly (P < 0.05) facilitated the formation and stability of soil aggregates (>2 mm). Relative to T1, the SOC content was increased under T2, T3, and T4 by 1.64–24.96% after the rape harvest and 3.23–34.74% after the rice harvest, and the highest SOC content was found under T4. Alkanes-C, aromatic-C, and alkenes-C were primarily distributed in >0.25 mm aggregates, whereas polysaccharides-C was mainly distributed in 0.25–0.053 mm aggregates. There were higher alkanes-C and alkenes-C concentrations in the no-tillage treatments (T3 and T4) compared to conventional tillage (T1 and T2). The relative phenolics-C concentration in all aggregates and polysaccharides-C concentration in >0.053 mm aggregates increased in the T2 treatment. The concentrations of amorphous and complex iron oxides significantly (P < 0.05) increased in the T2 and T4 treatment by 1.60–14.40% and 12.70–41.10%, respectively. Iron oxides were distributed disproportionally among the different size fractions of soil aggregates. The soil aggregate stability, and SOC and iron oxide concentrations were higher after the rice harvest than the rape harvest. Soil aggregate stability was strongly correlated with SOC (P < 0.01) and iron oxides (amorphous and complex iron oxides) (P < 0.05). Alkanes-C, aromatic-C, alkenes-C, and amorphous iron oxides were the most important binding agents in the >0.25 mm aggregates, while polysaccharides-C and amorphous and complex iron oxides were the main binding agents in the 0.25–0.053 mm aggregates. It was concluded that the high levels of SOC and amorphous and complex iron oxides in soil under T4 were responsible for the aggregate stability.

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.

Root-Derived Short-Chain Suberin Diacids from Rice and Rape Seed in a Paddy Soil under Rice Cultivar Treatments.

Suberin-derived substituted fatty acids have been shown to be potential biomarkers for plant-derived carbon (C) in soils across ecosystems. Analyzing root derived suberin compounds bound in soil could help to understand the root input into a soil organic carbon pool. In this study, bound lipids were extracted and identified in root and topsoil samples. Short-chain suberin diacids were quantified under rice (Oryza sativa L.) and rape (Brassica campestris) rotations with different cultivar combinations in a Chinese rice paddy. After removal of free lipids with sequential extraction, the residual bound lipids were obtained with saponification and derivatization before analysis using gas chromatography–mass spectrometry (GC-MS). Diacids C16 and C18 in bound lipids were detected both in rice and rape root samples, while diacids C20 and C22 were detected only in rape root samples. Accordingly, diacids were quantified in both rhizosphere and bulk soil (0–15 cm). The amount of total root-derived diacids in bulk soil varied in a range of 5.6–9.6 mg/kg across growth stages and crop seasons. After one year-round rice-rape rotation, root-derived suberin diacids were maintained at a level of 7–9 mg/kg in bulk soil; this was higher under a super rice cultivar LY than under a hybrid cultivar IIY. While concentrations of the analyzed diacids were generally higher in rhizosphere than in bulk soil, the total diacid (DA) concentration was higher at the time of rape harvest than at rice harvest, suggesting that rape roots made a major contribution to the preservation of diacids in the paddy. Moreover, the net change in the concentration and the ratios of C16:0 DA to C18:1 DA, and of C16:0 DA to C18:0 DA, over a whole growing season, were greater under LY than under IIY, though there was no difference between cultivars within a single growth stage. Overall, total concentration of root-derived suberin diacids was found to be positively correlated to soil organic carbon concentration both for bulk soil and rhizosphere. However, the turnover and preservation of the root suberin biomolecules with soil property and field conditions deserve further field studies.

Microbiological and Enzymatic Activity of Soil after Pollution with Fluorine

The objective of this research has been to determine the impact of soil contamination with fluorine, including the concomitant application of substances neutralizing this pollution, on counts of actinomyces, fungi, and copiotrophic bacteria, and on the activity of acid phosphatase, alkaline phosphatase, grease, and dehydrogenase. The research was based on two pot experiments, both conducted in 2009 in a greenhouse at the University of Warmia and Mazury in Olsztyn, Poland. One experiment involved winter oilseed rape, while the other was performed on maize followed by yellow lupine. The following factors were included in both experiments: I) increasing doses of fluorine in the form of potassium fluoride (0, 100, 200, 300 mgF·kg -1 of soil) II) substances neutralizing soil pollution with fluorine: lime, in a dose corresponding to 1 Hh of soil, charcoal, and loam – both in amounts equal to 3% of the soil mass per pot. The biological activity of soil was assayed after harvesting winter oilseed rape (BBCH 69) and yellow lupine (BBCH 69). It has been demonstrated that low doses of fluorine (from 100 to 200 mgF·kg -1 of soil) had a positive influence on counts of the analyzed microorganisms and on the activity of the examined soil enzymes. Under the influence of such low amounts of fluorine, the number of actinomyces and the activity of urease increased in soil tested after the harvest of winter rape and yellow lupine, the latter being a catch crop sown after maize. The neutralizing substances had a much better effect on counts of the analyzed microorganisms than on the activity of soil enzymes. The counts of actinomyces and copitrophic bacteria were positively affected by all the substances added to soil, as compared to the control treatments. With respect to fungi, these microorganisms responded positively only to the application of charcoal and loam to soil cropped with yellow lupine. In general, the tested substances had a beneficial influence on the activity of acid phosphatase and urease. As regards the activity of alkaline phosphatase, it was adversely affected by the neutralizing substances. The residual effect of fluorine on counts of the analyzed microorganisms and activity of the soil enzymes was milder in the soil sampled after the harvest of yellow lupine, which seems to indicate that fluorine loses its toxic properties with time.

Experimental Study of Reciprocating Friction between Rape Stalk and Bionic Nonsmooth Surface Units

Background. China is the largest producer of rape oilseed in the world; however, the mechanization level of rape harvest is relatively low, because rape materials easily adhere to the cleaning screens of combine harvesters, resulting in significant cleaning losses. Previous studies have shown that bionic nonsmooth surface cleaning screens restrain the adhesion of rape materials, but the underlying mechanisms remain unclear. Objective. The reciprocating friction between rape stalk and bionic nonsmooth metal surface was examined. Methods. The short-time Fourier transform method was used to discriminate the stable phase of friction signals and the stick-lag distance was defined to analyze the stable reciprocating friction in a phase diagram. Results. The reciprocating friction between rape stalk and metal surface is a typical stick-slip friction, and the bionic nonsmooth metal surfaces with concave or convex units reduced friction force with increasing reciprocating frequency. The results also showed that the stick-lag distance of convex surface increased with reciprocating frequency, which indicated that convex surface reduces friction force more efficiently. Conclusions. We suggest that bionic nonsmooth surface cleaning screens, especially with convex units, restrain the adhesion of rape materials more efficiently compared to the smooth surface cleaning screens.

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.

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.