Showing papers on "Sowing published in 2006"

Principles of Natural Regeneration of Tropical Dry Forests for Restoration

Abstract: Tropical dry forests are the most threatened tropical terrestrial ecosystem. However, few studies have been conducted on the natural regeneration necessary to restore these forests. We reviewed the ecology of regeneration of tropical dry forests as a tool to restore disturbed lands. Dry forests are characterized by a relatively high number of tree species with small, dry, wind-dispersed seeds. Over small scales, wind-dispersed seeds are better able to colonize degraded areas than vertebrate-dispersed plants. Small seeds and those with low water content are less susceptible to desiccation, which is a major barrier for establishment in open areas. Seeds are available in the soil in the early rainy season to maximize the time to grow. However, highly variable precipitation and frequent dry spells are important sources of mortality in seeds and seedlings. Collecting seeds at the end of the dry season and planting them when soil has sufficient moisture may increase seedling establishment and reduce the time they are exposed to seed predators. Germination and early establishment in the field are favored in shaded sites, which have milder environment and moister soil than open sites during low rainfall periods. Growth of established seedlings, however, is favored in open areas. Therefore, clipping plants around established seedlings may be a good management option to improve growth and survival. Although dry forests have species either resistant to fire or that benefit from it, frequent fires simplify community species composition. Resprouting ability is a noticeable mechanism of regeneration in dry forests and must be considered for restoration. The approach to dry-forest restoration should be tailored to this ecosystem instead of merely following approaches developed for moister forests.

Pre-sowing magnetic treatments of tomato seeds increase the growth and yield of plants.

Abstract: The effects of pre-sowing magnetic treatments on growth and yield of tomato (cv Campbell-28) were investigated under field conditions. Tomato seeds were exposed to full-wave rectified sinusoidal non-uniform magnetic fields (MFs) induced by an electromagnet at 100 mT (rms) for 10 min and at 170 mT (rms) for 3 min. Non-treated seeds were considered as controls. Plants were grown in experimental plots (30.2 m(2)) and were cultivated according to standard agricultural practices. During the vegetative and generative growth stages, samples were collected at regular intervals for growth rate analyses, and the resistance of plants to geminivirus and early blight was evaluated. At physiological maturity, the plants were harvested from each plot and the yield and yield parameters were determined. In the vegetative stage, the treatments led to a significant increase in leaf area, leaf dry weight, and specific leaf area (SLA) per plant. Also, the leaf, stem, and root relative growth rates of plants derived from magnetically treated seeds were greater than those shown by the control plants. In the generative stage, leaf area per plant and relative growth rates of fruits from plants from magnetically exposed seeds were greater than those of the control plant fruits. At fruit maturity stage, all magnetic treatments increased significantly (P < .05) the mean fruit weight, the fruit yield per plant, the fruit yield per area, and the equatorial diameter of fruits in comparison with the controls. At the end of the experiment, total dry matter was significantly higher for plants from magnetically treated seeds than that of the controls. A significant delay in the appearance of first symptoms of geminivirus and early blight and a reduced infection rate of early blight were observed in the plants from exposed seeds to MFs. Pre-sowing magnetic treatments would enhance the growth and yield of tomato crop.

Using USDA Crop Progress Data for the Evaluation of Greenup Onset Date Calculated from MODIS 250-Meter Data

Abstract: Identification of the onset of vegetation greenup is a key factor in characterizing and monitoring vegetation dynamics over large areas. However, the relationship between greenup onset dates estimated from satellite imagery and the actual growth stage of vegetation is often unclear. Herein, we present an approach for comparing pixel-level onset dates to regional planting and emergence information for agricultural crops, with the goal of drawing reliable conclusions regarding the physical growth stage of the vegetation of interest at the time of greenup onset. To accomplish this, we calculated onset of greenup using MODIS 250 m, 16-day composite NDVI time series data for Kansas for 2001 and a recently proposed methodology for greenup detection. We then evaluated the estimated greenup dates using the locations of 1,417 large field sites that were planted to corn, soybeans, or sorghum in 2001, in conjunction with United States Department of Agriculture (USDA) weekly crop progress reports containing crop planting and emergence percentage estimates. Average greenup onset dates calculated for the three summer crops showed that the dates were consistent with the relative planting order of corn, sorghum, and soybeans across the state. However, the influence of pre-crop vegetation (weeds and “volunteer” crops) introduced an early bias for the greenup onset dates calculated for many field sites. This pre-crop vegetation signal was most pronounced for the later planted summer crops (soybeans and sorghum) and in areas of Kansas that receive higher annual precipitation. The most reliable results were obtained for corn in semi-arid western Kansas, where pre-crop vegetation had considerably less influence on the greenup onset date calculations. The greenup onset date calculated for corn in western Kansas was found to occur 23 days after 50 percent of the crop had emerged. Corn’s greenup onset was detected, on average, at the agronomic stage where plants are 15 to 45 cm (6 to 18 inches) tall and the crop begins its rapid growth.

Growth and Yield Response of Facultative Wheat to Winter Sowing, Freezing Sowing and Spring Sowing at Different Seeding Rates

Abstract: Growth and yield of wheat are affected by environmental conditions and can be regulated by sowing time and seeding rate. In this study, three sowing times [winter sowing (first week of September), freezing sowing (last week of October) and spring sowing (last week of April)] at seven seeding rates (325, 375, 425, 475, 525, 575 and 625 seeds m -2 ) were investigated during the 2002-03 and 2003-04 seasons, in Erzurum (Turkey) dryland conditions, using Kirik facultative wheat. A split-plot design was used, with sowing times as main plots and seeding rates randomized as subplots. There was a significant year x sowing time interaction for grain yield and kernels per spike. Winter-sown wheat produced a significantly higher leaf area index, leaf area duration, spikes per square metre, kernel weight and grain yield than freezing- and spring-sown wheat. The optimum time of sowing was winter for the facultative cv. Kirik. Grain yields at freezing and spring sowing were low, which was largely the result of hastened crop development and high temperatures during and after anthesis. Increasing seeding rate up to 525 seeds m -2 increased the spikes per square metre at harvest, resulting in increased grain yield. Seeding rate, however, was not as important as sowing time in maximizing grain yield. Changes in spikes per square metre were the major contributors to the grain-yield differences observed among sowing times and seeding rates. Yield increases from higher seeding rates were greater at freezing and spring sowing. We recommended that a seeding rate of 525 seeds m -2 be chosen for winter sowing, and 575 seeds m -2 for freezing and spring sowing.

Efeito de temperaturas e substratos na germinação de sementes de Myracrodruon urundeuva Fr. All. (Anacardiaceae)

Abstract: Myracrodruon urundeuva Fr. All. (Anacardiaceae) is a native tree specie with excellent physical, chemical and biological properties. However, due to predatory exploration, it is in the official list of Brazilian species threatened with extinction. This work aimed at studying the germination of M. urundeuva seeds in different conditions of substrate and temperature regime. The experiment was a completely randomized design in a 8 x 7 factorial arrangement (7 temperatures 25, 27, 30, 35, 20-27, 20-30 and 20-35oC; and 8 substrates - sowing in and on: blotting paper, sand, vermiculite and coconut fiber) with four replications with 25 seeds. The following parameters were analyzed: germination (%), first germination count (%), germination speed index, average time of germination (days), and length (cm) of hipocotyl and primary root. Constant temperatures gave the shortest average time of seed germination and favored hipocotyl development. The best results for germination were obtained at 25 and 27oC in all substrates, except for sowing in between blotting paper at 27oC. The vermiculite and coconut fiber substrates allowed satisfactory germinative performance and did not require daily remoisten, proving to be suitable for the evaluation of the physiological quality of M. urundeuva seeds.

Performance of double-cropped winter wheat-summer maize under minimum irrigation in the North China Plain

Abstract: The double cropping of winter wheat (Triticum aestivum L.) and summer maize (Zea mays L.) in the North China Plain (NCP) requires intensive irrigation that results in rapidly depleting aquifers and threatens the sustainable agricultural development in the region. This study investigated the possibility of growing winter wheat and maize with minimum irrigation (MI) by bringing soil moisture in the top root zone to field capacity at sowing with no further irrigation afterwards. Results over 8 yr (1997-2005) showed that grain yield of winter wheat was over 5000 kg ha -1 and maize was over 6000 kg ha -1 in most of the seasons under MI. The average yield was decreased by 14% for winter wheat and 13% for maize compared with the fully irrigated treatment (FI). Water use efficiency (WUE) under MI was increased by 15% for winter wheat and 10% for maize compared with that under FI. Average seasonal evapotranspiration (ET) was 335 mm under MI and 447 mm under FI for winter wheat, and 319 mm and 403 mm for maize, respectively. The annual irrigation requirement of MI was only half that of FI. Yield reduction in MI was negatively related to seasonal rainfall (significant at P < 0.05). The success of Ml depended on the deeper root system of winter wheat using soil moisture that accumulated below the shallower rooted maize over the summer rainfall season. The results showed that an MI strategy that would be simple to implement for farmers would contribute significantly to the sustainability of the groundwater resource.

In vitro seed culture and seedling development of Calopogon tuberosus

Abstract: A major obstacle to native orchid production is difficulty in seed germination. Culture media and light effects on seed germination of Calopogon tuberosus var. tuberosus, a native orchid with horticultural potential, were studied. Culture media included Knudson C, Malmgren modified terrestrial orchid, and PhytoTechnology orchid seed sowing. Effects of 8 weeks continual darkness, 8 weeks 16-h photoperiod, 2 weeks dark followed by 6 weeks 16-h photoperiod, 4 weeks dark followed by 4 weeks 16-h photoperiod, and 6 weeks dark followed by 2 weeks 16-h photoperiod were examined. Percent seed germination was highest on Knudson C after 8 weeks culture; however, seedling development was enhanced on PhytoTechnology seed sowing medium during 8 weeks culture under a 16-h photoperiod. This suggests that while KC and darkness promoted seed germination, P723 and light enhanced further seedling development. Seedlings of C. tuberosus readily acclimated to greenhouse conditions.

2-cyanobenzenesulfonamide compounds for seed treatment

Abstract: The present invention provides a method for the for the protection of seeds from soil insects and of the resulting plant's roots and shoots from soil and foliar insects comprising contacting the seeds before sowing and/or after pregermination with a 2- cyanobenzenesulfonamide compound of the general formula (I) where the variables R to R are as defined in claim 1.

Fertilizer Nitrogen Efficiency in Durum Wheat under Rainfed Mediterranean Conditions: Effect of Split Application

Abstract: Efficient N fertilizer management is critical for the economic production of wheat and the long-term protection of environmental quality. A 3-yr field experiment on a rainfed Vertisol was designed to study the effects of N fertilizer timing on the efficiency of N in durum wheat (Triticum turgidum L. var. durum Desf.). A single rate of 150 kg N ha -1 was used with different fractions being applied at planting, tillering, and stem elongation. A 15 N experiment was also conducted within the main experiment area, with microplots, to quantify N uptake from fertilizer and soil. Mean wheat recovery of N fertilizer ranged from 12.7% when applied at sowing to 41.6% when applied as a topdressing at the beginning of stem elongation. The mean annual contribution of soil residual N and mineralization was 167 kg N ha -1 , representing a considerable proportion of total wheat N uptake-ranging from 80.4% when N fertilizer was applied in the fall to 56.3% when it was applied at stem elongation. This would account for the poor and inconsistent response of grain yield and N efficiency indices, and for the importance of soil N in Vertisols for predicting wheat N fertilizer requirements, due to the carryover effect. It is recommended that N fertilizer be applied mainly as a topdressing in durum wheat, between tillering and stem elongation, to enhance crop N use efficiency (NUE) and reduce losses through leaching and runoff.

Nitrogen Fertility and Planting Date Effects on Lint Yield and Cry1Ac (Bt) Endotoxin Production

Abstract: Early planted cotton (Gossypium hirsutum L.) and varieties expressing the Bacillus thuringiensis (Bt) gene offer improved yield potential. It is not dear whether the current N recommendations remain appropriate for these new production options. The objectives were to determine how varying rates, application timing, and sources of N affected cotton dry matter partitioning, leaf chlorophyll (Chl) concentration, leaf Bt (CrylAc) endotoxin concentration, lint yield, and fiber quality. Four N treatments (112 kg N ha -1 anhydrous; 112 kg N ha -1 liquid; 112/56 kg N ha -1 split; 56/56 kg N ha -1 split) were applied to three cotton varieties (PM 1218BR, STV 4691B, and FM 832) planted on either an early or normal planting date from 2001 through 2004. The N response was consistent across planting dates and varieties for all data collected as shown by the lack of any interactions with these variables. Although N treatments had no effect on lint yield or any dry matter partitioning components, plants receiving the 112/56 kg N ha -1 split application treatment exhibited 14% greater leaf CrylAc concentration and a 3% greater leaf Chl concentration than the other N treatments. Early planted cotton had 5% greater leaf Chl concentration but a 12% lower leaf CrylAc concentration than normal planted cotton. Lower CrylAc levels may reflect enhanced remobilization of the leaf protein to feed the faster developing boll load of the early planted cotton. Early planted cotton yielded 10% more than normal planted cotton because it produced 9% more bolls. Current N recommendations for normal planted cotton also appear sufficient for early planted cotton.

Recruitment limitation constrains local species richness and productivity in dry grassland

Abstract: Species coexistence and local-scale species richness are limited by the availability of seeds and microsites for germination and establishment. We conducted a seed addition experiment in seminatural grassland at three sites in southern Switzerland and repeated the experiment in two successive years to evaluate various circumstances under which seed limitation and establishment success affect community functioning. A collection of 144000 seeds of 22 meadow species including grasses and forbs of local provenance was gathered, and seeds were individually sown in a density that resembled natural seed rain. The three communities were seed limited. Three years after sowing, single species varied in emergence (0–50%), survival (0–69%), and establishment rates (0–27%). One annual and 13 perennial species reached reproductive stage. Low establishment at one site and reduced growth at another site indicated stronger microsite limitation compared to the third site. Recruitment was influenced by differences in abiotic environmental conditions between sites (water availability, soil minerals) and by within-site differences in biotic interaction (competition). At the least water-limited site, sowing resulted in an increase in phytomass due to establishment of short-lived perennials in the second and third years after sowing. This increase persisted over the following two years due to establishment of longer-lived perennials. After sowing in a wetter year with higher phytomass, however, productivity did not increase, because higher intensity of competition in an early phase of establishment resulted in less vigorous plants later on. Due to the generally favorable weather conditions during this study, sowing year had a small effect on numbers of established individuals over all species. Recruitment limitation can thus constrain local-scale species richness and productivity, either by a lack of seeds or by reduced seedling growth, likely due to competition from the established vegetation.

Presence of the a.i. imidacloprid on vegetation near corn fields sown with Gaucho ® dressed seeds

Abstract: In recent years the widespread use of corn seed hybrids dressed with the systemic insecticide Gaucho ® (a.i. imidacloprid), has been frequently linked, by beekeepers with bee colony losses registered during the corn sowing season. On the basis of a preliminary experiment, where the loss of imidacloprid from the pneumatic seed drills was highlighted, the aim of the study was to verify both the amount of contamination and the persistence of the active ingredient on leaves and flowers of spontaneous plants growing near corn fields in which Gaucho ® dressed seeds had been used. The observations were carried out in north eastern Italy on five different commercial corn hybrid seeds, three dressed with Gaucho ® [hybrids 2 (H2), 4 (H4) and 5 (H5)], one with a new adjuvant (H5). The escape of the active ingredient from the fan drain of the pneumatic seed drill was monitored using paper filters, whereas samples of grass and flowers were collected from the borders of sown fields. Meteorological data were registered. The samples (paper filters, grass and flowers) were analyzed using a gas chromatography method. Paper filters on the output of the drill fan have shown, at different concentrations, an escape of imidacloprid from the fan for each kind of Gaucho ® dressed seed; the order of magnitude of the escape ranged on average for H2, H4 and H5 from 120 to 240 µg of imidacloprid for 1 g of paper filter at 240 seconds. Therefore the new adjuvant did not eliminate the loss of active ingredient. Even if at different concentrations for each kind of Gaucho ® dressed hybrid, imidacloprid was found the same day of sowing on spontaneous vegetation near the corn fields; H2 showed the highest level of residues with values of 123.7 and 58.2 ng/g of imidacloprid respectively on flowers and grass. Residual imidacloprid on grass and flowers was found at least four days after sowing (H2), while the washing effect of heavy rain has been observed, which seemed to hide the detection of the active ingredient (H4 and H5). The investigation showed that Gaucho ® dressed corn seeds during sowing operations can release imidacloprid into the environment, and therefore bees and wild pollinator insects could bee exposed to the insecticide molecule. Plants could accumulate the active ingredient released during different sowing operations in the same area and become polluted for a time depending on the length of the sowing period. The same problem could be extended to other pesticides, at present or in the future, used in seed dressing.

Potential for a Rye Cover Crop to Reduce Nitrate Loss in Southwestern Minnesota

Abstract: Cover cropping practices are being researched to reduce artificial subsurface drainage NO 3 -N losses from agricultural lands in the Upper Mississippi watershed. This study was designed to investigate the influences of fall planting date and climate on cereal rye (Secale cereale L.) biomass and N uptake in the spring, and to assess subsurface drainage NO 3 -N loss reductions. A soil-plant-atmosphere simulation model, RyeGro, was developed and used to predict rye cover crop establishment and growth, soil water balance, N cycling, and drainage NO 3 -N losses from mid-September through May in southwestern Minnesota. An imbedded stochastic weather generator provided model climate inputs. Inclusion of a rye cover crop sown on 15 September reduced N losses by 11.1 kg N ha -1 or 45% for a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] crop rotation. Fall sowing dates of 1, 15, and 30 October resulted in reductions of 7.8, 5.8, and 4.6 kg N ha -1 , respectively, by the end of May. Desiccation of the rye on 1 May resulted in reductions of 4.5, 2.2, 1.2, and 0.7 kg N ha -1 , for the 15 September and 1, 15, and 30 October sowing dates, respectively. Cover cropping practice provides promising opportunities for reductions in N losses for cropping rotations wherein the primary crops are harvested before mid-September and planted after mid-May. We predict that a winter rye crop can reduce drainage NO 3 -N losses on average 7.4 kg N ha -1 for southwestern Minnesota if planted on 15 September and desiccated on 15 May.

Development and Testing of “On‐Farm” Seed Priming

Abstract: Poor germination and emergence of tropical crops under stressful conditions, such as adverse soil temperature, variable soil moisture, and hardening soils, are major obstacles to obtaining adequate stands of vigorous seedlings and hence reasonable yields in marginal areas of the less‐developed world. Representative examples of failures of common tropical crops to establish are reviewed and management techniques appropriate to resource‐poor farmers are discussed, including use of good quality seed, dry planting, timely sowing, control of sowing depth, transplanting of seedlings, and seed priming. It is concluded that successful establishment is associated with rapid emergence. Studies of “on‐farm” seed priming, whereby farmers can prime their own seeds in water, are reviewed in detail with special reference to work done in developing countries. A large body of in vitro, on‐station, and participatory on‐farm research shows that priming seeds of many important tropical crops in water, typically overnight, before sowing can increase the rate and extent of emergence, improve seedling vigor, advance flowering and maturity, and increase yield in most cases. In some instances, priming does not benefit farmers, but negative effects of priming are rare. The consequences of drying seeds after priming are discussed, as are opportunities for farmers to “add value” to their seeds by using priming to deliver nutrient supplements and increase resistance to pests and diseases. Given its low cost, on‐farm seed priming represents good insurance for risk‐averse, resource‐poor farmers.

Three Seasons of Subsistence Insect-Resistant Maize in South Africa: Have Smallholders Benefited?

Abstract: White maize is the staple food of the majority of the South African population. We examine if smallholder farmers that adopted insect-resistant (Bt) varieties of white maize benefited from planting Bt over the last three seasons. Commercial farmers are known to benefit from planting Bt maize in high stalk borer or corn borer infestation years, but when planted in locations or years when stalk borers are not a problem, Bt will usually not be profitable because of higher seed costs. In the first two production seasons, small farmers enjoyed higher yields with Bt maize than with conventional hybrid varieties despite lower-than-normal (yet still significant) stalk borer pressure and less-than-ideal maize production conditions. Yield is expressed according to grain per kilogram of seed planted, as seeding rates per land area differ drastically between small-scale farmers. The value of the yield benefit depended on how the farmer utilized the additional grain, with the highest valued use being home grinding and consumption substituting for more expensive store purchases. In the third season, which was also the fourth consecutive drier-than-usual season, the stalk borer infestation level was very low, and farmers who planted Bt maize had yields similar to farmers who planted conventional hybrids.

Management of environmental crop conditions to produce useful sunflower oil components

Abstract: The objective of this study was to investigate the impact of water availability and temperature after flowering on oil, major fatty acid and sterol contents in seeds of standard and oleic sunflower genotypes, under managed and controlled field conditions. When water deficit was effective from the beginning to the end of anthesis, it modified the fatty acid composition of standard hybrids. When water was supplied, a major enhancement of oleic acid content was associated with a concomitant reduction of linoleic acid content and a decrease in saturated fatty acid contents. Higher temperatures increased the oleic acid content in seeds of standard hybrids. Oil content was enhanced under colder temperature and irrigation. The content of minor oil components, phytosterols, was also enhanced when seed development occurred under high temperature and severe water stress. As a whole, the data showed that combining water management, sowing date and choice of genotype may orientate the biosynthesis of seed components and thus generate seed composition variability suitable for industrial purposes.

Influence of sowing density and spatial pattern of spring wheat (Triticum aestivum) on the suppression of different weed species

Abstract: To better understand the potential for improving weed management in cereal crops with increased crop density and spatial uniformity, we conducted field experiments over two years with spring wheat (Tr iticum aestivum) and four weed species: lambsquarters (Chenopodium album), Italian ryegrass (Lolium multiflorum), white mustard (Sinapis alba), and chickweed (Stellaria media). The crops were sown at three densities (204, 449, and 721 seeds m −2 ) and in two spatial patterns (normal rows and a highly uniform pattern), and the weeds were sown in a random pattern at a high density. In most cases, the sown weeds dominated the weed community but, in other cases, naturally occurring weeds were also important. There were strong and significant effects regarding the weed species sown, the crop density, and the spatial distribution on the weed biomass in both years. The weed biomass decreased with increased crop density in 29 out of 30 cases. On average, the weed biomass was lower and the grain yield was higher in the uniform compared to the row pattern in both 2001 and 2002. Despite the differences in weed biomass, the responses of L. multiflorum, S. media, and C. album populations to crop density and spatial uniformity were very similar, as were their effects on the grain yield. Sinapis alba was by far the strongest competitor and it responded somewhat differently. Our results suggest that a combination of increased crop density and a more uniform spatial pattern can contribute to a reduction in weed biomass and yield loss, but the effects are smaller if the weeds are taller than the crop when crop‐weed competition becomes intense.

Influence of Thiourea on Photosynthesis, Nitrogen Metabolism and Yield of Clusterbean ( Cyamopsis tetragonoloba (L.) Taub.) under Rainfed Conditions of Indian Arid Zone

Abstract: A 2-year field trial was conducted to study the effects of seed treatment (500 ppm) or foliar application of 1000 ppm thiourea (at 25 and 40 days after sowing) or a combination of these, on growth, yield, net photosynthesis and nitrogen metabolism of clusterbean (Cyamopsis tetragonoloba (L.) Taub.) grown for two consecutive years (1999 and 2000) under rainfed conditions of the Indian arid zone. Thiourea application either as pre-sowing seed treatment or as foliar spray significantly increased plant height, leaf area, dry matter production and seed yield as compared to the untreated control plants during both the years. However, maximum favourable effects were obtained with combined application of seed treatment and foliar spray. The beneficial effects of thiourea were attributed to its role in significantly increasing the net photosynthetic rates and the concentrations of total chlorophyll and starch in the leaves. Thiourea also reflected a positive role in enhancing nitrogen metabolism as it significantly increased nitrate reductase activity and concentration of soluble protein in the treated plants. It has been concluded that seed treatment with thiourea followed by foliar spray could significantly improve growth, yield and water use efficiency of rainfed clusterbean under arid conditions due to enhanced photosynthesis and more efficient nitrogen metabolism.

Influence of Polymer Seed Coatings, Soil Raking, and Time of Sowing on Seedling Performance in Post-Mining Restoration

Abstract: This study represents part of a broader investigation into novel seed broadcasting methodologies as a means to optimize rehabilitation techniques following sand mining. Specifically, the study investigated the use of polymer seed coatings, time of sowing application, and in situ raking of the topsoil to optimize seedling recruitment to site. For polymer seed coatings, an ex situ trial was undertaken to evaluate seed coating effects on seedling emergence. Results demonstrated that seed coatings did not significantly inhibit maximum emergence percentage of 10 Banksia woodland species (out of 11 evaluated), but coated seeds from four species were on average 2–6 days slower to emerge than noncoated seeds. Seed coatings were found to have a greater effect in situ, with more coated seeds emerging than noncoated seeds. Topsoil raking (following seed sowing) and time of sowing were found to have the greatest impact on seedling emergence, with higher emergence following topsoil raking (5- to 90-fold increase) and sowing in May (late autumn) (1.4- to 12-fold increase) rather than in July (mid-winter). The implications for mining rehabilitation are discussed, and areas for further research are considered.

Recolonisation and distribution of spiders and carabids in cereal fields after spring sowing

Abstract: Generalist predators are important for pest suppression during pest establishment because they may occur in the crop before and during pest arrival. However, different crop management practices can have a negative effect on predator populations. If so, there is a need for recolonisation by the predators to the crop fields. An important pest in Sweden is the bird cherry-oat aphid, Rhopalosiphum padi, which migrates to cereal fields in spring. In turn, many cereal fields are spring sown and thus are disturbed by harrowing and sowing a short time before aphid arrival. In this study, three different questions about the populations of spiders and carabids in spring cereal crops were asked. First, does sowing in spring have a negative effect on the predators present in the fields? Second, if sowing has a negative effect on predator populations, do they recolonise the fields before pest arrival? Third, how are the predators distributed in the fields? We found that most carabids and most lycosid spiders were not affected by sowing and were distributed uniformly in the fields after sowing. Most linyphiid spiders were negatively affected by sowing, but then they recolonised the fields and were uniformly distributed in the fields after recolonisation. Thus, many spiders and carabids are present in the fields after sowing in spring and have the opportunity to suppress aphids during their establishment phase, which in turn may prevent a possible outbreak.