Search

This study aimed to investigate the soil organic carbon (SOC) sequestration rate and soil organic matter (SOM) composition in conventional rotational cropping with mineral fertilization compared with organic cover cropping with and without composted manure addition during 2008–2018 to specify the SOM stabilization under different farming systems. The SOC proportion in particulate organic matter (POM) (63–2000 µm) and mineral-associated organic matter (MAOM) (&lt, 63 µm) fractions were estimated in different treatments, and the SOM composition in the fractions was characterized by FTIR spectroscopy. The SOC sequestration rate was treatment-dependent, with the higher SOC sequestration rate (1.26 Mg ha−1 y−1) in the organic treatment with cover crop and composted manure. Across all treatments, 57.3%–77.8% of the SOC stock was in the MAOM fraction. Mineral N fertilization increased POM-C concentration by 19%–52% compared with the unfertilized control. Under the organic treatments, the POM-C concentration was 83%–95% higher than the control. The MAOM-C concentration increased by 8%–20%. The mineral N fertilization and organic treatments (with and without cover crops and composted manure) increased the SOC stock proportion of POM. The highest proportion of SOC stock related to POM was in the cover cropping system, reducing the proportion of C related to the MAOM fraction, but the addition of composted manure with cover cropping also increased the proportion of C in MAOM. Compared with MAOM, the POM had a less resistant organic matter composition, and the POM resistance was higher in organic than conventional treatments. In general, the recalcitrance of SOM increased with SOC concentration. The POM fraction had higher aromaticity (or degree of decomposition) than the MAOM fraction. The aromaticity in POM and MAOM fractions was higher in the organic farming system and depended on mineral N fertilization and cover cropping, but the effect of manure was not significant. Although the SOC sequestration rate was higher under manure addition, resulting in the highest formation of both POM and MAOM in the soil, manure addition had little effect on overall SOM composition compared with cover crops.

The effects of organic (manure, cover crop) and mineral fertilisers on total yield, soil phosphorus (P) and potassium (K) dynamics and soil pH changes were studied over 10 years. Five field crops (spring barley, red clover, winter wheat, field pea, potato) were grown organically and conventionally in rotation. The total yield of the five crops fertilized similarly was 24–25% higher in conventionally fertilised treatments than in organic treatments. The higher yielding conventionally fertilised treatments (annual total yield 29.0–29.8 t ha–1) removed 12–18 kg ha–1 P and 45–73 kg ha–1 K per year, which was respectively 28–35% and 28–40% higher than organic treatments. The soil became more acidic in the conventional system (pH 5.4–5.9 versus 5.9–6.3). The highest annual P and K uptake was by potato, followed by winter wheat. Use of winter cover crops and composted cattle manure in the organic system did not maintain the levels of P and K in the soil at baseline.

BACKGROUND This study investigated how infestation rates of an important oilseed rape pest, the cabbage seed weevil (Ceutorhynchus obstrictus) and rates of parasitization by its parasitoids are affected by land use, up to 1000 m from 18 focal fields. RESULTS The mean proportion of C. obstrictus-infested pods per plant was 8% (2-19.5%). Infestation rates were higher if the adjacent habitat was a herbaceous semi-natural habitat than if it was either another crop or a woody habitat. Infestation rates were positively related to the area of herbaceous semi-natural vegetation, permanent grassland and wheat (which followed oilseed rape in the crop rotation) at a spatial scale of at least 1 km. The mean parasitism rate of C. obstrictus larvae was 55% (8.3-87%), sufficient to provide efficient biocontrol. Parasitism rates were unrelated to adjacent habitats, however, they were positively related to the presence of herbaceous linear elements in the landscape and negatively related to permanent grasslands at a spatial scale of 200 m. CONCLUSION Proximity of herbaceous elements increased both infestation rates and parasitism, while infestation was also related to landscape factors at larger distances. The findings provide an empirical basis for designing landscapes that suppress C. obstrictus, at both field and landscape scales. © 2018 Society of Chemical Industry.

Food systems need to become more sustainable. There is a need to investigate the agricultural management components that address the sustainability better. Long crop rotations are suggested to be environmentally friendly, yet, little is known how soil microbial communities may be affected by long-term rotation under organic cropping with cover crops and manure and conventional cropping with different nitrogen rates. We examined the composition and diversity of soil bacterial and fungal communities in a five-field crop rotation at the beginning and end, respectively in 2013 and 2018. Our analysis revealed that bacterial and to a lesser extent fungal diversity increased by the end of the rotation in all organic treatments and in conventional treatments with low to medium nitrogen rate (20‐100 kg of nitrogen per hectare). Conventional treatment with no added nitrogen decreased bacterial and fungal diversity. Nitrogen rate of 150 kg/ha decreased only bacterial diversity, while the impact on fungal diversity was neutral. Crop rotation significantly increased the relative abundance of bacterial taxa involved in nitrification and denitrification. Of fungal functional groups, the relative abundance of pathogenic functional groups decreased and mycorrhizal groups increased during crop rotation and especially with added cover crops. Our results suggest that crop rotation may outperform cropping systems in structuring soil microbial communities.

Nowadays, in sustainable agriculture growing winter cover crops and using organic manure have been widely implemented to improve soil quality which leads to increase of microbial activity. Six-year study was performed to evaluate the effect of cropping system on soil microbial hydrolytic activity, content of soil organic carbon (SOC) and total nitrogen (Ntot) under potato cultivation by considering various management systems, while comparing the soil parameters after previous crop. The experiment consisted of five-field crop rotation with two diferent organic (Org 0 as control and Org II with winter cover crops plus added composted manure) and conventional (Conv 0 as control and Conv II with mineral N, 150 kg ha–1) farming systems. The results showed that hydrolytic activity of soil microbes decreased in every farming system Under potato cultivation. Interestingly, after potato cultivation, the lowest and highest decrease in the soil microbial hydrolytic activity were seen in Org II and Conv II systems, respectively. The highest soil microbial hydrolytic activity was measured in system Org II where incorporation of biomass from winter cover crops and cattle manure was used. Finally, SOC and Ntot were higher in organic farming systems and there no significant changes after potato cultivation.

The experiments were carried out during 2012&ndash, 2017. There were 5 crops in rotation: Red clover, winter wheat, pea, potato and barley undersown (us) with red clover. There were 5 cropping systems in the experimental setup: 2 conventional systems with chemical plant protection and mineral fertilizers, 3 organic systems which included winter cover crops and farm manure. The aim of the present research was to study the effect of cultivating barley undersown with red clover and the preceding winter cover crop on the soil microbial hydrolytic activity, the change in the content of soil organic carbon (SOC) and total nitrogen (Ntot) compared to the same parameters from the field that was previously under potato cultivation (forecrop of barley in the rotation). The cultivation of barley with red clover (barley (us)) had a positive impact on the soil micro-organisms activity. In organic systems the soil microbial hydrolytic activity increased on average by 19.0%, compared to the conventional systems. By cultivating barley (us) the soil microbial hydrolytic activity had a significant effect on the SOC content only in organic systems where winter cover crops were used. Organic cultivation systems had positive impact on the soil nitrogen content, Ntot in samples taken before sowing the barley (us) was higher by 17.4% and after the cultivation of barley (us) by 14.4% compared to conventional systems, as an average of experimental years. After cultivation of barley (us) with red clover the soil microbial hydrolytic activity had no effect on the soil Ntot content in either cultivation systems.

The infestation rate and parasitoid communities of Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) were assessed on seven spring sown brassicaceous plant species to find potential secondary plants that might help increase the parasitism rates of this serious oilseed pest. Over the three-year study, the average infestation rate of pods by C. obstrictus remained below 10 % for each plant species. Despite the low pest abundance, C. obstrictus was parasitized by hymenopteran parasitoids on all plant species, except on Eruca vesicaria subsp. sativa ((Mill.) Thell.). Parasitism rates were remarkably high: between 33.7 and 70.8 % on average and peaked at 94.7 % on Raphanus sativus (L.) var. oleiformis (Pers.). Not only was the parasitism rate high on R. sativus, but it also had a different parasitoid species composition consisting mainly of egg parasitoids (Mymaridae), while on the other plant species larval parasitoids (Pteromalidae) dominated. These findings are important for planning new sustainable pest management approaches.

The effects of different winter cover crops and their combination with composted cattle manure on weeds and crop yields were investigated within a five-field crop rotation (barley undersown with red clover, red clover, winter wheat, pea, potato) in three organic cropping systems. The control system (Org 0) followed the rotation. In organic systems Org I and Org II the winter cover crops were used as follows: ryegrass (Lolium perenne L. in 2011/2012) and a mixture of winter oilseed-rape (Brassica napus ssp. oleifera var. biennis) and winter rye (Secale cereale L.) in 2012/2013 before pea; winter oilseed rape before potato and winter rye before barley. In Org II system composted cattle manure was also applied. In comparison with the control system, the winter cover crops, depending on plant species used, reduced the biomass and density of the weeds. In both years winter rye was a better suppressor of weeds than the other winter cover crops. Cover crops increased the yield of potato in rotation crops...

In a field experiment based on a five-year crop rotation (pea, potato, barley undersown with red clover, red clover and winter wheat), several soil parameters, porosity, number and biomass of earthworms, total nitrogen, organic carbon, percentage of water stable aggregates and enzymatic activity, were studied during 2013 and 2014, the first and second year, respectively, since the first rotation concluded. This rotation was managed under three organic farming systems: Organic 0 (control), Organic I (with winter cover crops lately incorporated into the soil as green manure) and Organic II (with the same cover crops plus a yearly amendment of 40 t ha−1 of cattle manure). Crop rotation had a yearly positive effect on the soil bulk density, and enhanced the percentage of air filled pores; nonetheless, despite the leguminous crops in the rotation, all the systems presented a yearly decrease in total nitrogen in 2014. Cover crops along with manure only had a significant effect on enzymatic activity; how...

Maintaining or enhancing the stock of soil organic carbon (SOC) is a key factor in sustaining the soil resources of the world. The objective of this research was to study the effect of different farming systems (conventional farming with mineral fertilizers and crop specific fertilization vs. organic farming with organic fertilizers (catch crops and composted manure)) under the same 5-crop rotation (red clover, winter wheat, pea, potato, barley undersown with red clover) system on the SOC stock and the stability of SOC. The second aim was to quantify plant C inputs to the soil and to identify the relationship between C sequestration rate and C input. Data presented in this paper concerned the first rotation during 2008–2012. The main factors were farming systems: conventional and organic. Four conventional farming systems differed in the mineral nitrogen application rates used. In two organic farming systems catch crops were used with or without composted solid cattle manure. The SOC stock was determined before experiment establishment and after the first rotation. The C input into the soil was calculated based on the main product yield. The stock of SOC increased (2.57 Mg ha−1 y−1) considerably after the first rotation only in the organic farming systems, where the total C inputs were 1368 kg C ha−1 y−1 higher compared to the average C inputs in conventional systems. The mineral N rate did not influence the C-input but it had an effect on the properties and mineralisation of soil organic matter. The stable C fraction of SOC proportion increased in the system in which the highest rate of mineral N (20–150 kg N ha−1y−1 depending on crop) was used and its proportion in the soil was comparable with the results obtained from organic farming systems. Thus, the intensive management with high N rates may benefit to a formation of more stabile SOC if the crop rotation used is properly elaborated.

Since 2008, a 5-year crop rotation experiment (winter wheat, pea, potato, barley undersown with red clover, and red clover) has been run in Tartu, Estonia, to evaluate the changes in soil chemical parameters under four fertilizer managements: (1) unfertilized conventional plots (conventional I), (2) conventional plots with addition of mineral fertilizers (conventional II), (3) organic plots with cover crops during the winter period (organic I), and (4) organic plots with the same cover crops plus a yearly amendment of 40 t ha–1 of cattle manure (organic II). After the first rotation, results showed significant differences (P

A study was conducted which aimed to investigate the effect of farming systems (FS) (four conventional with increasing mineral N fertilizer amounts 0–150 kg of N ha−1) vs. two organic with catch crops (CC) and cattle manure (CC + M)) under the same five crop rotation system on the occurrence of tuber diseases such as common scab (Streptomyces spp.), silver scurf (Helminthosporium solani), dry rot (Fusarium spp.), and soft rot (Pectobacterium spp.). As the average of the first rotation years 2009–2011, the FS had a significant effect on the occurrence of silver scurf, dry rot and common scab (surface cover

For testing how cover crops and different fertilization managements affect the soil physical properties in a plough based tillage system, a five-year crop rotation experiment (field pea, white potato, common barley undersown with red clover, red clover, and winter wheat) was set. The rotation was managed under four different farming systems: two conventional: with and without mineral fertilizers and two organic, both with winter cover crops (later ploughed and used as green manure) and one where cattle manure was added yearly. The measurements conducted were penetration resistance, soil water content, porosity, water permeability, and organic carbon. Yearly variations were linked to the number of tillage operations, and a cumulative effect of soil organic carbon in the soil as a result of the different fertilization amendments, organic or mineral. All the systems showed similar tendencies along the three years of study and differences were only found between the control and the other systems. Mineral fertilizers enhanced the overall physical soil conditions due to the higher yield in the system. In the organic systems, cover crops and cattle manure did not have a significant effect on soil physical properties in comparison with the conventional ones, which were kept bare during the winter period. The extra organic matter boosted the positive effect of crop rotation, but the higher number of tillage operations in both organic systems counteracted this effect to a greater or lesser extent.

Nowadays, organically produced products have become more popular than ever and interest in them is still growing fast. The early blight causal pathogen Alternaria solani has not been considered a great threat to potato in northern climate conditions in the past and has not been routinely sprayed against. During our study early blight was evaluated in 2010 and 2011 on the plants of a potato cultivar ‘Reet’ in an organic farming experiment. In our study, both growing seasons were very favourable for early blight development. Significant differences between the two cultivation technologies were found (F1,12 = 4.84, p = 0.048). In 2010, the area under disease progress curve (AUDPC) value was 303 on cover crop (CC) plots and 990 on CC + M (manure) plots that is three times higher, whereas in 2011, the AUDPC value was 967 on CC plots and 1195 on CC + M plots. Our results confirm that potato early blight has become a serious problem in North-East European organic potato fields and thus susceptible potato cultivars cannot be recommended for growing in an organic farming system. However, it is possible to influence the development severity of early blight by selecting the proper growing technology. Since, in the changing climate conditions and in susceptible cultivars, early blight is a potato disease that can cause early defoliation of plants and crop death, there is a need for resistant potato cultivars.

The effect of thinning on fruit weight, color, biochemical composition, and on leaf insect occurrence was studied in an over 80-year-old orchard on two apple tree (Malus domestica Borkh.) old cultivars: Liivi Sibuloun and Paide Talioun. The study was conducted to restore an old orchard for quality apple juice production. Pruning led to a significant increase in pests, but the number of natural enemies of pests and of neutral insects did not increase. The total number of arthropods was significantly higher on ‘Paide Talioun’ in the second year after pruning. Consequently, more pests were found in both experimental years on this cultivar. Pruning significantly increased leaf SPAD value leading to a decrease in the total phenolics content of the fruit. The effect of thinning on ascorbic acid content was cultivar dependent. Fruit skin was greener, apple flesh color was yellower, and fruit weight increased by up to 60% after pruning. Among apple taste parameters, the sugar acidity ratio was not influenced by p...

In organic farming, nutrient cycling is based mainly on a farm level with external inputs only when organic fertilisers are not cycled and produced, and conventional systems largely depend on external inputs. Therefore, crop rotations are important tools for maintaining soil fertility and for increasing crop yields and qualities not only in organic farming systems but also in conventional systems. Moreover, proper nutrient management is a key element for sustainable farming. To identify the farming systems that would be sustainable for a longer period, a field experiment was conducted. The aim of this study was to investigate how different farming systems influenced tuber yields and quality (N, NO3−, P, K, Ca, Mg, dry matter and starch concentrations) of potato as well as how potato cultivation within a crop rotation under different farming systems affects soil quality (pH, Ntot, Corg, plant available P, K, Ca and Mg concentrations). Potato (Solanum tuberosum L.) was part of a five crop rotation experiment in which red clover (Trifolium pratense L.), winter wheat (Triticum aestivum L.), peas (Pisum sativum L.), potato and barley (Hordeum vulgare L.) followed each other simultaneously on a same field. Data presented in this paper concerned the first 3 years of the rotation during 2009–2011. The experiment was performed with six different farming systems as follows: two organic and four conventional. In both organic farming systems, catch crops (Organic CC) were used to provide organic green manure. In the second organic system, fully composted cattle manure (Organic CC + M) at a rate of 40 t ha−1 was also added as a fertiliser. The four conventional farming systems differed in the amounts of mineral fertilisers used as follows: N0P0K0 (control), N50P25K95 (low), N100P25K95 (average), or N150P25K95 (high). The average yield as well as tuber N, NO3−and Mg concentrations were significantly influenced by farming systems, year and their interaction. Fresh tuber yields were significantly higher under conventional systems in which nitrogen fertilisers were used. The use of average and high amounts of mineral nitrogen fertilisers increased tuber nitrogen and nitrate concentrations. The use of nitrogen fertilisers slightly decreased tuber Mg concentrations. There were no significant differences among farming systems in average tuber K, Ca, dry matter and starch concentrations. Only the year and its interaction with farming systems had a significant influence on these indicators. Different farming systems had different effects on some soil quality parameters. The Organic CC system significantly decreased the average soil K concentration after potato cultivation. The other organic system, Organic CC + M, significantly increased the average soil Corg and P concentrations after potato cultivation. The conventional control system significantly decreased the average soil Ntot, K and Mg concentrations and increased the P concentration. The conventional system that received 50 kg N ha−1 significantly decreased the average soil Ntot concentration after potato cultivation. The farming system that received an average amount of mineral nitrogen fertilisers significantly increased the average soil Corg and P concentrations and decreased the soil pH and K after potato cultivation. The conventional system that received 150 kg N ha−1 significantly decreased the average soil Corg, K and Mg concentrations. The average plant available Ca concentrations before and after potato crops did not have statistically significant differences among systems.

We have established for the first time that Colorado potato beetle (CPB) (Leptinotarsa decemlineata Say) (Coleoptera: Chrysomelidae) produced a distinct second generation in 2010 in Estonia. This species has a history, in Estonia, of less than 50 years. Due to their great ability to adapt to variable environmental conditions, the beetles spread very quickly throughout the country and established a permanent population in the 1980s. Before 2010, CPB has been predominantly univoltine. The occurrence of the second generation was the result of rare coincidence of extremely favourable weather as the cumulative degree days (DD) of 927 exceeded the sum needed for two full generations. Constantly high temperatures from the beginning of May caused the formation of summer generation adults already by the end of July and the long day photoperiod, as well the availability of fresh food, kept the beetles in reproductive mode preventing the onset of diapause. Summer beetles continued to oviposit up to the second half o...

A two-year small plot experiment was performed to test whether (1) other plants in the cruciferous family: Brassica juncea (L.) Czern. and Sinapis alba L. are more attractive to the cabbage seed weevil (Ceutorhynchus obstrictus (Marsham)) than turnip rape (Brassica rapa Metzg.) and oilseed rape (Brassica napus L.); (2) the host plant species affects the oviposition preferences of parasitoid species attacking the cabbage seed weevil. According to our results oilseed rape had the highest pest infestation. The parasitism rate was highest on B. juncea and B. rapa. Thus, we can assume that wild relatives of oilseed rape plants can support the presence of hymenopteran natural enemies of pests in the field. The parasitism rate was surprisingly high, up to 85.4% on B. juncea. In addition to the key parasitoids of C. obstrictus, species from the family Mymaridae were also found. The species composition of parasitoids differed between investigated plant species, suggesting that the physical or volatile characteristics of closely related plant species affect the behavioural responses of C. obstrictus parasitoids and therefore could be used to enhance the natural enemy complex.

Nitrogen (N) deficiency is a major problem in organic and low-input farming systems. Growing spring cereals with undersown legumes has a positive effect on soil fertility, enriching it with nitrogen, through symbiosis of legumes with nodule bacteria. Two hypotheses were tested: 1) undersowing of red clover increases the protein content of barley grains and 2) mineral N has negative aftereffect on growth of legume plants. The aim of this study was to investigate the effect of organic (cattle manure, off-season cover crop) and mineral N in organic and conventional farming systems on (i) barley (Hordeum vulgare L.) grain yield and quality, (ii) biomass yield formation of undersown red clover (Trifolium pratense L.) and (iii) the aftereffect of mineral and organic N fertilisers on the red clover crop biomass yield in the following year. The experiment was established in 2008 at the Estonian University of Life Sciences (58°22ʹ N, 26°40ʹ E) on the soil described as Stagnic Albic Luvisol (LV ab-st) (WRB, 2014) with sandy loam surface texture, 1.38% C, 0.13% N, 133 mg kg-1 P, 210 mg kg-1 K and pHKCl 6.0. The crops were treated using different farming systems: three organic (Org0, OrgI and OrgII) and four conventional (N0, N40, N80 and N120); nitrogen sources during crop cycle period: N0 and Org0 = symbiotically fixed atmospheric N2, N40 = N2 + mineral N 40 kg ha-1 N, N80 = N2 + mineral N 80 kg ha-1 N, N120 = N2 + mineral N 120 kg ha-1 N, OrgI = N2 + N taken up by cover crops (NCC) and OrgII = N2 + NCC + N applied with manure (Nm). Our study revealed that grain yield of barley was strongly affected by undersown red clover; because of competition for nutrients in cereallegume mixture the grain yield of barley in organic system was 11‒61% lower than that in conventional system. The seed rate of undersown red clover (2.84 million viable seed per ha) was too high. The content of proteiin depended on the availability of mineralised nitrogen. The mean protein content of barley grains over the trial years and treatments was 99 ± 1.6 g kg-1 in the conventional system, which was 17% higher than that in the organic system. Undersowing of red clover had no significantly positive effect on the grain yield and protein content of barley. Mineral N fertiliser had no negative aftereffect on growth of the red clover crop the following year. Mean above ground biomass yield over the trial years for the red clover crop 2nd cut was 17% higher in the conventional system than in the organic system.

Nitrogen (N) availability is a key factor influencing the yield of Brassica napus L. Thus, mineral fertilization is widely used to improve the quality and quantity of seeds. In this study, we conducted field experiments to determine the impact of nitrogen fertilization on B. napus pests, their parasitoids and plant diseases. The results showed that N treatment had an impact on the abundance of pollen beetles (Meligethes aeneus Fab.) and cabbage seed weevils (Ceutorhynchus obstrictus Marsh.) as well as dark spot disease (Alternaria brassicae (Berk.) Sacc.). Since pest abundance was not correlated with the flower and silique numbers, the feeding and oviposition sites, plant smell bouquets were analysed to determine potentially attractive or repellent volatile organic compounds. We detected 19 different compounds among which acetic acid and several lipoxygenase pathway products were emitted at higher levels from N-treated plants. Emission of a few other terpenoid compounds was correlated with the pest abundance in field conditions. Abundance of parasitoids of both pests was related to the host availability rather than to the fertilization treatment. Therefore, we suggest that plant chemical cues play a minor role in localization of hosts in close proximity to parasitoid. Dark spot disease levels decreased with increasing N availability, possibly reflecting enhanced emissions of acetic acid, a known antifungal volatile. This study demonstrates the effects of N fertilization on bud and flower volatile bouquets, which might play a role in B. napus insect pest host selection and in resistance to fungal plant diseases. Further studies are necessary to investigate the behavioural responses of insects to the changed volatile bouquets.

Oilseed rape (Brassica napus) is a valuable crop, attacked by several insect pests, of which the pollen beetle (Meligethes aeneus) is one of the most widespread and important in Europe. The relative attractiveness for the pollen beetle of Brassica nigra, Eruca sativa and Raphanus sativus was compared with that of spring oilseed rape, to assess the potential of these plant species as trap crops for the pest. At early growth stages, B. nigra and R. sativus were more attractive to over-wintered adult pollen beetles than B. napus. At the bud and flowering stages, B. nigra was the most attractive while E. sativa was the least attractive. At flowering, B. nigra was more attractive for oviposition than the other species. Thus, of the species tested, B. nigra has the most potential as a prospective trap crop to protect spring oilseed rape before flowering when it is at its most vulnerable developmental phase, due to its faster development and its acceptability both for feeding and oviposition to overwintered pollen beetle adults. Raphanus sativus was accepted both for feeding and oviposition, but pollen beetle larvae failed to develop in its flowers; it therefore has the potential for use as a dead-end crop. At the end of the growing season, both E. sativa and R. sativus, as late-flowering species, attracted the new generation of pollen beetles and thereby have potential to extend the effectiveness of a trap-cropping system at this time.

Ceutorhynchus obstrictus (Marsham) (Coleoptera: Curculionidae) is a major pest of oilseed rape in Europe and North America. The last decade has seen growing interest in the occurrence, importance and efficiacy of its parasitoids as biocontrol agents. The infestation of pods by C. obstrictus larvae and their parasitism rates were assessed in a total of nine commercially-grown crops and fifteen experimental plots of winter oilseed rape in 2004–2007. Pod samples were collected at the pod maturation stage and incubated in emergence traps. Emerged larvae, their exit holes and parasitoids were counted and identified; the percentage of infested pods and parasitism rates were calculated. Pod infestation by larvae increased continuously over the study period. The parasitism level was lowest in 2005 and increased thereafter up to 96%. The most abundant parasitoid was Trichomalus perfectus (Walker), but Mesopolobus morys (Walker) and Stenomalina gracilis (Walker) (Hymenoptera: Pteromalidae) were also reared from hos...

Willow short rotation coppice is used as a renewable energy source and also as a vegetation filter for purifying wastewater. Wastewater irrigation might change microclimatic conditions and increase the canopy density in plantations, which might decrease production due to leaf rust ( Melampsora epitea ). The aim of this study was to estimate the impact of the canopy density on rust abundance on willows. For that, we counted rust pustules on leaves of five different willow clones from dense and sparse areas in both the wastewater irrigated and control part of the plantation. The results demonstrated clear differences between clones; clone ‘81090’ was very susceptible, ‘78183’ susceptible, ‘78021’ fairly tolerant and ‘Tora’ rust resistant. Clone ‘Gudrun’, which was previously reported resistant, had severe rust damages in Estonia. In the case of clones ‘78183’ and ‘78021’ there were significantly more rust pustules per leaf unit area at areas with denser canopy, which confirmed that higher plant density could result in biomass losses caused by leaf rust. No differences, however, were detected between dense and sparse areas of hybrid clone ‘Gudrun’, most probably because in this particular case leaves from upper canopy layer were used. There was a tendency detected that clones with a higher number of shoots per plant had more rust damages on their leaves, however, the correlation was not statistically confirmed. In conclusion, the impact of canopy density on rust abundance is clone-specific and significant in the case of clones on which infection starts from the lower part of the canopy.

Willow leaf rust (Melampsora epitea) is an important leaf pathogen in short rotation coppice plantations. Although ecological factors influencing rust severity are rather well known, to date, the connections between leaf morphological traits and rust infections are poorly studied. The aim of this study was to examine the relation between rust severity and specific leaf area (SLA). Willow leaves of three different clones from waste-water-irrigated and non-irrigated plantation areas were used. The results revealed a significant positive correlation between SLA and rust severity. There were clone specific differences whereas more rust pustules were always accompanied with higher SLA. Waste-water-irrigated plants had higher SLA and always more rust damages. These results suggest that leaves with low SLA are less susceptible to leaf rust in various conditions.

Summary A 3-year field study was carried out to determine the effect of wastewater irrigation and previous differences in mineral fertilization on the occurrence of willow leaf rust (Melampsora epitea). The experiment was conducted in two energy forest plantations: one designed for wastewater purification and the other as a mineral fertilization experiment. The severity of leaf rust on different clones and sites with different treatments was assessed by counting the number of uredinia per leaf unit area. Generally, plants irrigated with wastewater consistently had more leaf rust, irrespective of the study years or willow clones. Previous mineral fertilization had mixed effects on different clones 2 years after the last application. Three years after the last fertilizer application, however, no impact of the treatment on rust disease development was detected. In general, the rust levels differed from year to year probably due to climate. In this study, no correlation was detected between shoot age and rust severity, whereas climate and treatments strongly influenced leaf rust levels on some willow clones.

Blackcurrants are an important berry crop in many European countries. There is increasing demand for new and economically valuable blackcurrant cultivars suitable for organic production. To meet this demand, potential candidates of blackcurrant cultivars have been studied under Estonian field conditions. Our aim was to evaluate blackcurrant cultivars with regard to their productivity, berry quality, and resistance to the blackcurrant gall mite (Cecidophyopsis ribis Westw.). Our results showed that the drop of berries was the highest in the control treatment (no fertilizers used), and the lowest in conventional treatment. Higher yields were obtained from the conventional and organic treatments. The most productive cultivar, with the biggest berries and highest ascorbic acid content irrespective of cultivation system, was the cultivar ‘Pamyati Vavilova’. Organically cultivated berries had a higher content of ascorbic acid than did conventionally cultivated berries. Minor damage by mites was observe...

The impact of minimised (MIN – no plough, direct drilling, no pesticides) and standard (STN – plough, standard application of pesticides) cropping systems on the abundance of old (previously overwintered) and new generations of Meligethes aeneus (Fabricius) (Nitidulidae, Coleoptera) was assessed in spring oilseed rape in 2003 – 2005 in Estonia. Old generation M. aeneus were more abundant in STN than in MIN crops, despite the application of insecticide, probably because the latter reduced M. aeneus damage to the buds, making STN crops more attractive to M. aeneus seeking feeding and oviposition resources. The abundance of new generation M. aeneus showed a strong linear increase over the 3 years, on both MIN and STN systems. In 2005, the abundance of new generation M. aeneus was significantly greater in the STN than in the MIN field. The study showed that the application of insecticides promotes population increase in new generation M. aeneus.

The adoption of non-inversion tillage practices has been widely promoted due to their potential benefits in reducing energy consumption and greenhouse emissions as well as improving soil fertility. However, the lack of soil inversion usually increases weed infestations and changes the composition of the weed community. Weed management is still a main drawback for the wider adoption of reduced tillage practices. However, it is not entirely clear whether these changes in weed communities are a consequence of non-random filters on the functional attributes of weed species and may thus affect the potential weed-crop competition relationship. Here, we analyse the changes in weed diversity, community composition, and the functional attributes of weed communities under reduced (non-inversion) and conventional (inversion) tillage. We discuss their potential effects on the competitiveness against crop production using data from two crops of seven on-going organic and low-input field trials in different climatic regions across Europe. Weeds were evaluated after post-emergence weed control methods. We used the community weighted mean values of the life form (annuals versus perennials), specific leaf area, seed weight, canopy height, seed bank longevity, soil nutrient conditions affinity, beginning of flowering and flowering span. Moreover, the effect of the crop type on the functional attributes was also evaluated. Overall, the tillage system affected the composition and functional attributes of the weed communities. Weed community changes may imply a reduction in weed-crop competition under both tillage systems. For instance, weed communities under reduced tillage were potentially less competitive because they were shorter and had less affinity to nutrients. On the other hand, weed communities under conventional tillage had potentially less seed production and a lower abundance of perennial species. Our study thus supports tillage as an important driver of the functional attributes of weed communities, but both tillage systems can have their downside. However, the crop type was overall more relevant than the tillage in determining most of the trait values of the weed communities.

The six most important pests of oilseed rape are host to at least 80 species of parasitoid, mostly parasitic Hymenoptera, particularly braconids, chalcids and ichneumonids. Most of them attack the egg or larval stages of their hosts. Based on reviews of the literature and extensive sampling programmes during the EU project MASTER (QLK5-CT-2001-01447), 12 species have been identified as the key parasitoid species of these pests in winter oilseed rape, and, with little divergence, also in spring rape in nearly all European countries where their hosts occur. Some key species have been recorded for the first time in individual partner countries. They are sufficiently widespread and abundant across Europe to be of potential economic importance for conservation biological control of the target pests. Their incidence and abundance in European countries were associated with the occurrence of their hosts, thereby indicating close host-parasitoid-relationships.

The computer-based DSS proPlant incorporates weather-based phenological models for the six major pests of oilseed rape in Europe: the cabbage stem flea beetle, the rape stem weevil, the cabbage stem weevil, the pollen beetle, the cabbage seed weevil and the brassica pod midge. The models have now been validated for several European countries. The system predicts the start and course of pest infestation and provides site-specific crop protection treatment decisions, a selection of suitable chemicals, computes optimum dates and rates for application and evaluates the efficacy of past applications. Phenological models for migration of some key parasitoids of the pests have also been constructed recently; their use in finding spray windows to conserve parasitoids is described. Further work is needed to validate them before they can be integrated into a pest control strategy for farmers.

The pests and their hymenopterous parasitoids present in a spring and a winter oilseed rape crop in Estoniawere studied. Meligethes aeneus was themost abundant pest in both crops. Other crucifer-specialist pests included: Ceutorhynchus assimilis, C. pallidactylus, C. rapae, C. floralis, C. pleurostigma and Phyllotreta spp., but their abundance was low. Four species of parasitoids of M. aeneus larvae (Diospilus capito, Phradis morionellus, P. interstitialis and Tersilochus heterocerus) and threeof C. assimilis larvae (Mesopolobus morys, Stenomalina gracilis and Trichomalus perfectus) were also found.

To investigate the impact of different cropping systems, the pests, their hymenopteran parasitoids and predatory ground beetles present in two spring rape crops in Estonia, in 2003, were compared. One crop was grown under a standard (STN) cropping system and the other under a minimised (MIN) system. The STN system plants had more flowers than those in the MIN system, and these attracted significantly more Meligethes aeneus, the only abundant and real pest in Estonia. Meligethes aeneus had two population peaks: the first during opening of the first flowers and the second, the new generation, during ripening of the pods. The number of new generation M. aeneus was almost four times greater in the STN than in the MIN crop. More carabids were caught in the MIN than in STN crop. The maximum abundance of carabids occurred two weeks before that of the new generation of M. aeneus, at the time when M. aeneus larvae were dropping to the soil for pupation and hence were vulnerable to predation by carabids.

The aim of organic agriculture is to produce food of high nutritional quality in sufficient quantity. Field experiments were conducted to evaluate the effect of organic and conventional growing systems on (i) total amounts and supply of N taken up or applied to plants during a five year crop cycle period and (ii) crops total dry matter (DM) yield obtained during same period. The total DM yields from the organic treatments were 25–33% smaller than from the conventional treatments. The ratio of N output/N input was significantly the smallest in the organic treatment with cattle manure, where only 37% of all supplied N was used by plants during the crop cycle period. The organic fertiliser with faster mineralisation rate and splitting the application of organic N during crop cycle period would be more appropriate to supply sufficient quantities of N during rapid plant growth and to obtain higher crop yields in organic farming systems.