High Harvesting Costs Research Articles

Birch shelterwood removal – harvester and forwarder time consumption, damage to understory spruce and net revenues

ABSTRACTTo improve the micro climate for Norway spruce (Picea abies (L.) Karst.) regeneration and achieve higher growth, a system of birch shelterwoods with naturally regenerated birch (Betula spp.) creating an overstory sheltering planted spruce is implemented in southern Sweden. Even though the primary objective is to establish a new spruce stand, the economic viability depends on efficient birch overstory harvest with little damage to spruce regeneration. This study aimed to analyze time consumption and net revenues for harvester and forwarder work when removing the birch overstory, and to describe the frequency of logging damage in the residual spruce stand. Time consumption data was collected through time studies of harvesting and forwarding of 10 study plots. Sample plots were inventoried after harvesting and forwarding operations to identify damage on the residual spruce. Average harvester productivity was 2.8 oven dry ton per efficient work hour. The variation in time consumption was up to 94%, explained by a positive correlation with the number of trees harvested per hectare and a negative relationship with removed volume per hectare. Forwarder loading time correlated with forwarded volume along the strip road and the number of birch trees per ha prior to logging. Approximately 7–17% of the residual trees were damaged, and the harvester caused 83% of the damage. Due to high harvesting costs and low revenues, only plots with large removals provided positive net revenues. Birch shelterwoods can therefore not be expected to increase net revenues but are best seen as a regeneration method for addressing stand re-establishment challenges.

The Resource Utilization of Water Hyacinth (Eichhornia crassipes [Mart.] Solms) and Its Challenges

The unchecked growth of Eichhornia crassipes can cause significant harm, including covering of the water surface, depletion of oxygen, clogging of river channels, and promotion of the breeding of flies and mosquitoes. These effects can significantly impact farmland irrigation, water transportation, and human health. However, methods for controlling its growth are not ideal, and control using biological and chemical agents can result in secondary pollution. The utilization of E. crassipes as a resource, for example, as animal feed or organic substrates, can not only turn waste into valuable resources, but it can also solve the problem of its growth, thus bringing about economic and ecological benefits. In this paper, the growth and ecological characteristics of E. crassipes, its nutrient composition, and resource utilization approaches were reviewed. The challenges associated with the large-scale utilization of E. crassipes were also analyzed in order to provide references for the control and resource utilization of the species. Regarding challenges such as the difficulty of cultivation and the high cost of harvesting and dehydrating, it is necessary to investigate the proper water surface and coverage characteristics of E. crassipes cultivation to assure adequate biomass and protect the ecological landscape. It is also necessary to evaluate the effect of E. crassipes cultivation on the health of aquatic ecosystems and the safety of the water environment in order to prevent the significant potential ecological and environmental risks. In addition, developing portable, high-efficiency facilities to promote the effectiveness of harvesting, transportation and dehydration are needed, as well as further improvement in the techniques of utilization and assessment of the economic value.

New ultra-flat photobioreactor for intensive microalgal production: The effect of light irradiance

One of the main bottlenecks for the exploitation of microalgae is the low biomass concentration of the cultures: high harvesting costs and large cultivation area are always required. This bottleneck is partly due to a low light availability along the optical path of photobioreactors. An ultra-thin flat photobioreactor (UFP) (3 mm thickness) was proposed to increase both biomass concentration and productivity. The performance of the UFP was investigated: the effects of incident light intensity - from 50 and 1000 μmolPhotons m−2 s−1 - on cell growth, photosynthesis rate, and biochemical composition of Chlorella sorokiniana were characterized. The maximum microalgal concentration and the maximum areal productivity were 24 kg m−3 and 1.34 g m−2 h−1, respectively. The cell specific growth rate reached 0.1 h−1 at 1000 μmol m−2 s−1. The biochemical composition of the microalgal biomass changed with the light irradiance. Protein content increased from 35 up to 53% of DW with increasing the light intensity. The concentration of storage compounds, such as starch and lipids, decreased from 30 to 16% and from 30 to 10%, respectively, with increasing the light intensity. A limit in the maximum biomass concentration achievable was identified. Several hypotheses have been discussed. A light transfer model was applied to assess the presence of light limitation. Other hypotheses were analyzed in depth and the most feasible explanations were found to be a) the damage to the photosystem when exposed for long period to continuous and high light irradiances, b) nutrient limitation due to salt precipitation or c) gas-liquid transfer of the CO2. Finally, benefits and drawbacks of the ultra-thin culture system were discussed.

Effects of nitrogen and phosphorus concentrations on the growth of microalgae Scenedesmus. LX1 in suspended-solid phase photobioreactors (ssPBR)

Attached microalgae cultivation is an effective way to decrease the high harvesting cost in microalgae biomass production. Nitrogen and phosphorus, as the two main nutrients, are hypothesized to influence the attachment efficiency and growth of microalgae. The attached growth of Scenedesmus. LX1 in the suspended-solid phase photobioreactor (ssPBR)1 with feed composed of different total nitrogen (TN) and total phosphorus (TP) concentrations was studied in this paper. The productivity of attached microalgae on Day 3 (3 × 106 cells·cm−3) at the nutrient levels of TN = 15 g m−3 and TP = 5 or 3 g m−3 was approximately 70% higher than that at relatively high-nutrient levels (i.e. TN = 150 g m−3 and TP = 10 or 15 g m−3). Under the nutrient levels of TN = 15 g m−3 and TP = 5, 3, 1.5, 0.5 g m−3, the average TN and TP concentrations in the microenvironment around microalgae biofilm were about 2.1 and 15.5 times higher than those of the bulk media, respectively. The higher nutrient concentration in the surrounding microenvironment of microalgae biofilm improved protein synthesis of attached microalgae compared to the suspended ones within the same reactor, especially at the late stage of batch cultivation.

Timber mobilization and habitat tree retention in low-elevation mixed forests in Switzerland: an inventory-based scenario analysis of opportunities and constraints

Timber use in central Europe is expected to increase in the future, in line with forest policy goals to strengthen local wood supply for CO2-neutral energy production, construction and other uses. Growing stocks in low-elevation forests in Switzerland are currently high as exemplified by the Swiss canton of Aargau, for which an average volume of 346 ± 16 m3 ha−1 was measured in the 3rd Swiss National forest inventory (NFI) in 2004–2006. While this may justify a reduction of growing stocks through increased timber harvesting, we asked whether such a strategy may conflict with the sustainability of timber production and conservation goals. We evaluated a range of operationally relevant forest management scenarios that varied with respect to rotation length, growing stock targets and the promotion of conifers in the regeneration. The scenarios aimed at increased production of softwood, energy wood, the retention of potential habitat trees (PHTs) and the conversion to a continuous cover management system. They were used to drive the inventory-based forest simulator MASSIMO for 100 years starting in 2007 using the NFI sampling plots in Aargau. We analyzed model outputs with respect to projected future growing stock, growth, timber and energy yield and harvesting costs. We found growing stock to drop to 192 m3 ha−1 in 2106 if business-as-usual (BAU as observed between the 2nd and 3rd NFI) timber volumes were set as harvesting targets for the whole simulation period. The promotion of conifers and a reduction of rotation lengths in a softwood scenario yielded 25% more timber over the whole simulation period than BAU. An energy wood scenario that reduced growing stock to 200 m3 ha−1 by 2056 and promoted the natural broadleaved regeneration yielded 9% more timber than BAU before 2056 and 30% less thereafter due to decreasing increments. The softwood scenario resulted in higher energy yield than the energy wood scenario despite the lower energy content of softwood. Retaining PHT resulted in a reduction of timber harvest (0.055 m3 ha−1 yr−1 per habitat tree) and higher harvesting costs. Continuous cover management yielded moderate timber amounts throughout the simulation period, yet sustainably. Considering climate change, we discuss the risks associated with favoring drought- and disturbance-susceptible conifers at low elevations and emphasize that continuous cover management must allow for the regeneration of drought-adapted tree species. In conclusion, our simulations show potential for short-term increases in timber mobilization but also that such increases need to be carefully balanced with future forest productivity and other forest ecosystem services.

Heart valves from polyester fibers: a preliminary 6-month in vivo study.

Transcatheter aortic valve implantation (TAVI) has become a popular alternative technique to surgical valve replacement for critical patients. Biological valve tissue has been used in TAVI procedures for over a decade, with over 150,000 implantations to date. However, with only 6 years of follow up, little is known about the long-term durability of biological tissue. Moreover, the high cost of tissue harvesting and chemical treatment procedures favor the development of alternative synthetic valve leaflet materials. In that context, textile polyester [polyethylene terephthalate (PET)] could be considered as an interesting candidate to replace the biological valve leaflets in TAVI procedures. However, no result is available in the literature about the behavior of textile once in contact with biological tissue in the valve position. The interaction of synthetic textile material with living tissues should be comparable to biological tissue. The purpose of this preliminary work is to compare the in vivo performances of various woven textile PET valves over a 6-month period in order to identify favorable textile construction features. In vivo results indicate that fibrosis as well as calcium deposit can be limited with an appropriate material design.

Metabolic engineering of microalgae: a review and future prospects

Microalgae are widely distributed in nature, which can produce lipids, pigments, polysaccharides, as well as other high-value products through cell metabolism. However, low product content and high cost of cell harvesting negatively impact the practical application of microalgae. To utilize microalgal resources more effectively, it is necessary to modify the microalgae strains with genetic modification technologies for producing specific metabolites efficiently. Genome editing, metabolic engineering and synthetic biology tools are being developed for accelerating the production of important metabolites to meet the growing demands of energy, food and pharmaceutical industries using microalgae. The recent progress of related studies is summarize in this review, with future prospects provided.

A continuous flocculants-free electrolytic flotation system for microalgae harvesting

High harvesting cost and reusing of post-harvest water are the major challenges in commercial production of microalgae. In this work, a flocculants-free electrolytic flotation harvest process was investigated. The electrode design and materials were evaluated in terms of harvesting efficiency. Stainless steel as the cathode and carbon as the anode were selected based on the harvesting efficiency data and non-sacrificial feature for construction of a pilot scale harvesting system. In the pilot scale experiments, 23.72g/h biomass yield was achieved at the power consumption of 2.73kWh/kg. With the advantages of no chemical flocculent contamination and relatively low energy requirement, this continuous system is promising for food or feed applications.

微藻磁分离进展研究

微藻能源是理想的可再生能源，能部分替代化石能源。然而其开发利用受微藻细胞小、浓度低导致的采收困难、采收成本高的限制。低成本、高效率地将微藻与水体有效分离是保障微藻推广利用的关键。本文分析了传统微藻分离技术存在的难点及研究趋势，讨论了国内外微藻磁分离技术研究现状及存在问题。为微藻水处理、资源回收等领域的进一步应用提供一定的基础理论研究保障。 Microalgae is an ideal renewable energy source that can partially replace fossil fuels. However, the difficulties and high cost of microalgae harvesting which caused by small cell and low concentration are the main constrains of microalgae utilization and further application. Hence, cost-effec- tive separation of microalgae from water body becomes the key issue to microalgae utilization. This paper analyzed the difficulties and research trends of traditional microalgae separation technology, discussed the current problems of microalgae magnetic separation technology, and further provided a theoretical basis for microalgae water treatment, resource recovery and its other application.

Productivity and work processes of small-tree bundler Fixteri FX15a in energy wood harvesting from early pine dominated thinnings

First thinnings are often neglected in Europe due to high harvesting costs. The studied small-tree bundler (Fixteri FX15a) was developed in order to rationalize the integrated harvesting of small-diameter energy wood and pulpwood in thinning operations, and to reduce transportation costs through load compaction. For the time-and-motion study, three stand types were chosen, all dominated by Scots pine (Pinus sylvestris). Two were dense, small dimension stands. The third stand was a “normal” first thinning stand. The machine fells and accumulates small-trees, which are fed into the bundling unit, where crosscutting, compaction, winding, scaling, and output of bundles of approximately 0.6 m3 solid is performed in an automated process. The productivity in the dense stand with rich undergrowth was 9.7 m3/PMh (productive machine hour), with an average tree volume of 27 dm3 and 3216 trees felled per hectare. In the dense stand with no undergrowth, a productivity of 11.9 m3/PMh was reached. The average tree volume here was 44 dm3, and 2019 trees per hectare were harvested. In the normal first thinning stand with no undergrowth, the felled trees averaged 84 dm3, 1266 trees per hectare were felled, and a productivity of 13.8 m3/PMh was registered. When compared with the previous version, the Fixteri II, the productivity of Fixteri FX15a was 2.1–2.3 times higher, depending on the density and size of the removal. Several factors may explain the increased productivity, but one of the most prominent is an improved technical potential for multi-tree handling.

Möglichkeiten zur Holzmobilisierung im Tessiner Kastaniengürtel

Timber mobilization possibilities for the chestnut belt of Ticino Many of the traditionally managed chestnut groves and coppice forests in the canton of Ticino have been abandoned in the second half of the 20th century. The ensuing natural development resulted in homogenized stand structures across the landscape, increasing growing stocks and diminishing provision of ecosystem services (e.g. timber, protection from gravitational hazards, nature conservation and recreation services). We used a forest growth simulator (“Massimo”) to simulate a range of management scenarios and possible consequences. Under the current low intensity management growing stocks and tree mortality continue to increase, which – at a large scale – could further reduce the protection and other services and increase the risk of forest fires. This process could be countered with more intense management practices, yet facing relatively high timber harvesting costs. An optimized forest management in the chestnut belt would require the definition of the dominating forest functions, the designation of priority areas and monetary compensation schemes for the provision of the respective forest ecosystem services.

Fungal-assisted algal flocculation: application in wastewater treatment and biofuel production.

BackgroundThe microalgal-based industries are facing a number of important challenges that in turn affect their economic viability. Arguably the most important of these are associated with the high costs of harvesting and dewatering of the microalgal cells, the costs and sustainability of nutrient supplies and costly methods for large scale oil extraction. Existing harvesting technologies, which can account for up to 50% of the total cost, are not economically feasible because of either requiring too much energy or the addition of chemicals. Fungal-assisted flocculation is currently receiving increased attention because of its high harvesting efficiency. Moreover, some of fungal and microalgal strains are well known for their ability to treat wastewater, generating biomass which represents a renewable and sustainable feedstock for bioenergy production.ResultsWe screened 33 fungal strains, isolated from compost, straws and soil for their lipid content and flocculation efficiencies against representatives of microalgae commercially used for biodiesel production, namely the heterotrophic freshwater microalgae Chlorella protothecoides and the marine microalgae Tetraselmis suecica. Lipid levels and composition were analyzed in fungal-algal pellets grown on media containing alternative carbon, nitrogen and phosphorus sources from wheat straw and swine wastewater, respectively. The biomass of fungal-algal pellets grown on swine wastewater was used as feedstock for the production of value-added chemicals, biogas, bio-solids and liquid petrochemicals through pyrolysis. Co-cultivation of microalgae and filamentous fungus increased total biomass production, lipid yield and wastewater bioremediation efficiency.ConclusionFungal-assisted microalgal flocculation shows significant potential for solving the major challenges facing the commercialization of microalgal biotechnology, namely (i) the efficient and cost-effective harvesting of freshwater and seawater algal strains; (ii) enhancement of total oil production and optimization of its composition; (iii) nutrient supply through recovering of the primary nutrients, nitrogen and phosphates and microelements from wastewater. The biomass generated was thermochemically converted into biogas, bio-solids and a range of liquid petrochemicals including straight-chain C12 to C21 alkanes which can be directly used as a glycerine-free component of biodiesel. Pyrolysis represents an efficient alternative strategy for biofuel production from species with tough cell walls such as fungi and fungal-algal pellets.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0210-6) contains supplementary material, which is available to authorized users.

DEVELOPMENT OF A SELF-PROPELLED REAPER FOR WHEAT CROP

Harvesting of wheat crop is one of the important agricultural operations which demands considerable amount of labour in the case of the use manual harvest. Wheat prevalent harvesting methods in Egypt are manual cutting traditional and by reaper. The present study was carried out to manufacture and evaluate a self propelled vertical conveyor reaper with cutting width of 1.5 m. The reaper was operated by using 12 hp diesel engine and four wheels ground to harvest wheat crop .The reaper consists of two main parts: reaping–conveying part (reaping head) and driving, mobile part (motive power). In order to maintain the wheat stalks complete without wasting. Used by the farmer in order to feed the animals after threshing by threshing machines to overcome the problems resulting from the use of combine harvest. As well as to overcome the high cost of manual harvesting. This Innovative Mechanical machine ensures 100% recovery of straw with negligible grain losses at a surprisingly low cost of operation and will save time. This machine can be used in wheat, rice, barley and other grain crops.With this machine, we hope to provide farmers nationwide with a way to harvest grains on small plots of land in cities and along the periphery of urban areas. The variables of this study were : four forward harvesting speeds of, 2.1, 3.0, 4.2 and 5.1 km/h, four grain moisture content of, 23.5, 21.3, 19.1 and 16.3 %, w.b. and four levels of cut of, 5, 8, 12 and 15 cm. The above mentioned variable were tests to examine their effects on total grain losses,%, harvesting efficiency %, effective field capacity fed/h, energy consumption, kW.h/fed, operating cost, L.E./fed, and criterion cost, L.E./fed. The experimental results reveal that the maximum total grain losses of 2.6, %was recorded at forward speed of 5.1 km/h, levels cut of 5 cm and grain moisture content of 16.3 %. The minimum effective field capacity of 0.61 fed/h at forward speed of 2.1 km/h, levels cut of 5 cm and grain moisture content of 23.5 %. The minimum energy consumed of 5.0 kW.h/fed at forward speed of 5.1 km/h, levels cut of 15 cm and grain moisture content of 16.3 %. The maximum operating cost of 30.49 L.E./fed was recorded at forward speed of 2.1 km/h, levels cut of 5 cm and grain moisture content of 23.5 %.

Study on personal, socio-economic, communication, situational characteristics and constraints of adopting recommended practices ofKharif groundnut growers in Saurashtra zone of Gujarat

Groundnut is considered as the world’s fourth largest source of edible oil and third most important source of vegetable protein. It is also a major oilseed legume crop in India and meets about 30 per cent of the edible oil requirements in the country. Groundnut is a principal crop of the Saurashtra region of Gujarat State. It is grown so extensively since 1910. There is a wide gap exists between average yield of common farmers and actual potential yield. The study was conducted in the South Saurashtra AgroClimatic Zone of Gujarat State. The study was conducted under ex-post facto research design. 4 talukas were randomly selected, from each selected taluka three villages were selected randomly. Thus, 12 villages were selected. Total 120 respondents, 10 respondents from each selected village were selected by using multistage random sampling technique with a condition that the farmers have cultivated Kharif groundnut at least since last two years. Important constraints faced by farmers are High price of chemical fertilizers, Less supply of electricity, High price of improved and hybrid seeds, High cost of threshing and harvesting as well as high cost and lack of skilled labours. And important remedies to overcome it are Remunerative price of the product should be made available; the projects for increasing availability of irrigation water should be implemented.

Economic, environmental and social impact of alternative forest management in Baden-Württemberg (Germany) and Västerbotten (Sweden)

The forest sector is important for the German Federal State of Baden-Württemberg (BW) and the Västerbotten (VB) County in Sweden. Their forestry wood chains (FWCs) are of similar magnitude and supply forest industries. This study provides a regional comparison of the performance of FWCs from roundwood harvesting, including hauling, to mill gate concerning the factors that impact sustainability and assess different sustainability indicators for alternative supply chains, in particular fully mechanized chains in comparison to motor-manual operations. The harvest volumes are similar but operational conditions differ. Analysis of sustainability indicators demonstrated that the total costs for roundwood to industry are similar. Higher harvesting costs in BW are compensated for by lower transport costs to the mills. Employment per unit is higher in BW because of the high share of labour in felling. Due to smaller machinery and shorter transport distances in BW, energy use and greenhouse gas emissions per unit are lower than in VB. Areas for improvement are the technologies for logging in BW and the logistics of timber transport in VB.

Sensing Miscanthus Stem Bending Force for Maximizing Throughput Rate in a Disk Mower-Conditioner

Abstract. One of the reasons for relatively high biomass harvesting cost is challenges in adjusting the ground speed of harvesting machines with respect to the yield level within a field. A real-time biomass yield sensor that can predict the yield in front of a machine could be a useful tool to control ground speed. It was hypothesized that the force required to bend Miscanthus stems is a reliable predictor of biomass yield. Based on this novel concept, a stem bending force-sensing system was developed and field tested with a disk mower-conditioner. A bale-specific method, segmenting the field area from which a bale was formed, was developed to correlate sensed bending force and Miscanthus yield. The measured bending force showed a logarithmic relationship (R 2 = 0.80) with Miscanthus yield. The average error in predicting bale-specific yield was 10.3% for training data and 12.9% for validation data. The average error in predicting plot yield was 3.4% for training plots and 10.0% for validation plots. Using the developed logarithmic correlation model, yield maps were also generated. For the specific case analyzed, a proper control strategy to maximize throughput rate (mass per unit time) would be to either operate the mower-conditioner at the maximum feasible ground speed (9 km h -1 ) or at the maximum achievable throughput rate (60 Mg h -1 ). The yield-sensor controlled machine would result in 44.2% higher field capacity, 41.3% higher throughput rate, and 31.2% lower mowing-conditioning cost for the specific case analyzed compared to the operator-controlled machine. Studies are needed to extend the stem bending force-sensing concept to other thick-stemmed crop harvesting machines, such as sugarcane harvesters and coppice harvesters.

Ansätze zur Senkung der Holzerntekosten in der Schweiz

Approaches to reducing timber harvesting costs in Switzerland For over two decades, the majority of Swiss forest enterprises have been confronted with financial losses. One of the main reasons for this is the general diminishing of revenues from timber sales since the 1980s. Moreover, Swiss forest enterprises have not managed to reduce the most important matter of expenses – the timber harvesting costs – to a similar extent. In comparison, unit costs from timber harvest in Switzerland are more than twice as high as those in the neighboring countries. This study analyzes the cause-and-effect relationships that lead to the high timber harvesting costs in Swiss forest enterprises. Building on that, possibilities of reducing these costs are proposed. The study is based on the results obtained through the Swiss Forestry Holding Network (HDN). The results have been systematically analyzed, the cause-and-effect relationships graphically depicted, and the gained knowledge has been discussed with experts. In essence, the results from the HDN suggest that the high timber harvesting costs are primarily a consequence of the structural situation of the Swiss forest enterprises. The over-proportionally high number of employees and large machinery parks allocated to each of the management areas are inevitably leading to high timber harvesting costs, and thus to suboptimal timber harvesting methods. Subsequently, this is all giving rise to an unfavorable cost situation. Furthermore, economies of scale can hardly be reached among the large numbers of relatively small forest enterprise management areas producing low usage quantities. In essence, the most important approaches to reducing the timber harvesting costs are the more frequent involvement of specialized forest services for harvesting, and measures that lead to the enlargement of the management areas. In order to reduce timber harvesting costs and by that improve operation results, a critical reflection of the current forest management strategy is unavoidable.

Production potential and crop agronomy of sweet gale (Myrica gale L.) in the north of Scotland

Sweet gale (Myrica gale L.) is a common shrub in the wetter parts of north-west Europe, north America and Asia. An oil obtained from shoots of Scottish plants has been included in cosmetic products but, as a result of the high costs of wild harvesting, the potential for growing sweet gale as an agricultural crop is being investigated. Six trials, comparing three weed control treatments (no weeding, herbicide and herbicide plus mulch) were planted and monitored at different sites in northern Scotland from 2008 to 2010. Good weed control was critical for plant survival and growth and was most effectively achieved with herbicide plus mulch and this treatment indicates the potential of the crop. By 2010, averaged across sites, plant survival was highest (63%) in this treatment and fresh weight shoot yields (0.75tha−1 and 35.4gplant−1) and oil yield (1.38Lha−1) were all significantly (P<0.05) higher than in the other treatments. These yields are higher than those reported for wild harvesting, but at the best site, yields were about 4 times the average, showing the importance of good site selection. Soil water content was significantly (P<0.05) higher in the mulch treatment down to about 30cm depth through most of the growing season. Oil concentration was not significantly affected by weed control treatment but, in 2009, was significantly (P<0.001) affected by site, with site averages ranging from 1.01 to 2.36μLg−1 fresh weight. In 2009 and 2010, oil concentration was significantly (P<0.05) negatively correlated with site temperature over the growing season. Studies of shoot growth showed that the rate of leaf emergence was significantly (P<0.001) correlated with both soil and air temperatures and the relationships suggested base temperatures of 5.2°C and 6.9°C for air and soil, respectively.

Determining Adequate Vibration Frequency, Amplitude, and Time for Mechanical Harvesting of Fresh Mandarins

Mechanical citrus harvesting systems in Spain can solve the problem of the high costs of manual harvesting. Previous results, without the use of abscission agents, have shown the effectiveness of trunk and limb shakers for mechanical citrus harvesting. It is crucial to define the adequate vibration time to achieve an acceptable removal percentage because a higher vibration time could render the operation economically unviable. To address mechanical citrus harvesting, it is also necessary to determine the vibration conditions (amplitude, frequency, and duration) to ensure maximum removal efficiency. The objective of this research is to determine the optimal combination of vibration frequency, amplitude, and duration that will ensure maximum removal efficiency in mechanical citrus harvesting. Marisol and Orogrande mandarin trees were tested and harvested with a commercial trunk shaker. The Marisol trees were shaken at a vibration of 15 Hz for 5 s with a 0.030 m displacement. The Orogrande trees were shaken at 15 and 20 Hz frequencies with two shakes, the first lasting 5 s and the second lasting 2 s, 3 to 4 s after the first shake, with a 0.030 m displacement. Due to the low trunk height of orchard trees in the Valencia region, it is impossible to study intermediate and high amplitudes with a commercial olive trunk shaker. To solve this limitation, a laboratory unidirectional vibratory device was used to shake the branches at a vibration frequency of 4.6 to 18.1 Hz and a vibration amplitude modified from 0.06 to 0.18m. The field and laboratory results show that the mechanical citrus removal percentage exhibits a logarithmic behavior with time. The laboratory test shows that high-amplitude and intermediate vibration frequencies in the branches achieve adequate removal percentages. Lengthening the shaking time and repeating the shaking process do not increase the removal efficiency. In the field test, almost all the detached fruit fell in the first 2 to 3 s of shaking. It was evident that two shakes were not necessary to obtain an acceptable removal percentage. The results found in the laboratory indicate the possibility of reducing the frequencies and increasing the amplitudes to achieve an optimal mechanical citrus harvest. In the fresh market for citrus from the Mediterranean region, with very low citrus trunk heights, mechanical harvesting equipment can be adapted to achieve high vibration amplitude and intermediate vibration frequencies in the branches.

Assessing the short rotation woody biomass production on marginal post-mining areas

The Lusatian lignite-mining district (Eastern Germany) is characterized by a high share of marginal post-mining areas. At these sites, crop yield is generally low, and hence, conventional land use systems often fail in terms of reliable and efficient crop production. In this paper the attempt is made to evaluate the production of woody biomass for bioenergy in short rotation coppices (SRC) and alley cropping systems (ACS) with black locust (Robinia pseudoacacia L.) and lucerne (Medicago sativa L.) from the aspect of possible ecological and economic benefits compared to the conventional agricultural recultivation practice. The results show that, due to both high establishment and harvesting costs and comparatively low prices of energy wood, land use systems such as SRC or ACS are currently hardly profitable compared to conventional agriculture. However, the cultivation of black locust resulted in a higher humus accumulation and in a lower harvest-related nutrient export than the cultivation of lucerne as a typical recultivation crop in this region. Therefore, it can be concluded that for an improvement of soil fertility woody biomass production is more beneficial than the conventional agricultural recultivation practice.