Expansion, harvest and cryopreservation of human mesenchymal stem cells in a serum-free microcarrier process

Human mesenchymal stem cell (hMSC) therapies are currently progressing through clinical development, driving the need for consistent, and cost effective manufacturing processes to meet the lot-sizes required for commercial production. The use of animal-derived serum is common in hMSC culture but has many drawbacks such as limited supply, lot-to-lot variability, increased regulatory burden, possibility of pathogen transmission, and reduced scope for process optimization. These constraints may impact the development of a consistent large-scale process and therefore must be addressed. The aim of this work was therefore to run a pilot study in the systematic development of serum-free hMSC manufacturing process. Human bone-marrow derived hMSCs were expanded on fibronectin-coated, non-porous plastic microcarriers in 100mL stirred spinner flasks at a density of 3×10⁵cells.mL^-1 in serum-free medium. The hMSCs were successfully harvested by our recently-developed technique using animal-free enzymatic cell detachment accompanied by agitation followed by filtration to separate the hMSCs from microcarriers, with a post-harvest viability of 99.63±0.03%. The hMSCs were found to be in accordance with the ISCT characterization criteria and maintained hMSC outgrowth and colony-forming potential. The hMSCs were held in suspension post-harvest to simulate a typical pooling time for a scaled expansion process and cryopreserved in a serum-free vehicle solution using a controlled-rate freezing process. Post-thaw viability was 75.8±1.4% with a similar 3h attachment efficiency also observed, indicating successful hMSC recovery, and attachment. This approach therefore demonstrates that once an hMSC line and appropriate medium have been selected for production, multiple unit operations can be integrated to generate an animal component-free hMSC production process from expansion through to cryopreservation.

Variation in carotenoid content of kale and other vegetables:a review of pre- and post-harvest effects

Lutein and zeaxanthin are carotenoids that are selectively taken up into the macula of the eye, where they are thought to protect against the development of age-related macular degeneration. They are obtained from dietary sources, with the highest concentrations found in dark green leafy vegetables, such as kale and spinach. In this Review, compositional variations due to variety/cultivar, stage of maturity, climate or season, farming practice, storage, and processing effects are highlighted. Only data from studies which report on lutein and zeaxanthin content in foods are reported. The main focus is kale; however, other predominantly xanthophyll containing vegetables such as spinach and broccoli are included. A small amount of data about exotic fruits is also referenced for comparison. The qualitative and quantitative composition of carotenoids in fruits and vegetables is known to vary with multiple factors. In kale, lutein and zeaxanthin levels are affected by pre-harvest effects such as maturity, climate, and farming practice. Further research is needed to determine the post-harvest processing and storage effects of lutein and zeaxanthin in kale; this will enable precise suggestions for increasing retinal levels of these nutrients.

The commercial bark harvest of the African cherry (Prunus africana) on Mount Oku, Cameroon: Effects on traditional uses and population dynamics

Bark extracts of the African cherry (Prunus africana) are used to treat benign prostatic hyperplasia. This study examined the effects of commercial bark harvest on population dynamics in the Kilum-Ijim Forest Preserve on Mount Oku, Cameroon and on traditional uses. P. africana is valued for its timber and as fuel although its greatest value is as a traditional medicine for human and animal ailments. Harvest has depleted the resource and has eroded traditional forest protection practices. I constructed matrix models to examine the effects of bark harvest on population structure and on population dynamics in harvested and unharvested populations. Harvesting simulations examined the effect on the population growth rate (λ) with differing levels of mortality of harvest-sized and large trees and differing harvest frequencies. Size class frequencies for the entire forest decreased in a reverse j-shaped curve, indicating adequate recruitment in the absence of harvest. Individual plots showed differences from the overall forest data, suggesting effects of natural and man-made perturbations, particularly due to bark harvest. One plot (harvested in the 1980s) showed a temporal difference in λ and fluctuated around one, due to alternating high and low fruiting years; other unharvested plots showed smaller temporal differences. Harvested plots (harvested illegally in 1997) had values of λ less than one and showed small temporal differences. The control plot also showed λ less than one, due to poor recruitment in the closed canopy forest. The value of λ for the combined data was 0.9931 suggesting a slightly declining population. The elasticity matrix for the combined data indicated the population growth rate was most sensitive to the survival of the large reproductive trees (42.5% of the elasticity). In perturbation analyses, reducing the survival of the large trees caused the largest reductions in λ. Simulations involving harvesting frequency indicated λ returns to pre-harvest conditions if trees are re-harvested after 10–15 years, but only if the large trees are left unharvested. Management scenarios suggest harvest can be sustainable if seedlings and small saplings are planted in the forest and actively managed, although large-scale plantations may be the only feasible option to meet market demand. ^

Human impacts on pig frog (Rana grylio) populations in south Florida wetlands: Harvest, water management and mercury contamination

This study investigated how harvest and water management affected the ecology of the Pig Frog, Rana grylio. It also examined how mercury levels in leg muscle tissue vary spatially across the Everglades. Rana grylio is an intermediate link in the Everglades food web. Although common, this inconspicuous species can be affected by three forms of anthropogenic disturbance: harvest, water management and mercury contamination. This frog is harvested both commercially and recreationally for its legs, is aquatic and thus may be susceptible to water management practices, and can transfer mercury throughout the Everglades food web. ^ This two-year study took place in three major regions: Everglades National Park (ENP), Water Conservation Areas 3A (A), and Water Conservation Area 3B (B). The study categorized the three sites by their relative harvest level and hydroperiod. During the spring of 2001, areas of the Everglades dried completely. On a regional and local scale Pig Frog abundance was highest in Site A, the longest hydroperiod, heavily harvested site, followed by ENP and B. More frogs were found along survey transects and in capture-recapture plots before the dry-down than after the dry-down in Sites ENP and B. Individual growth patterns were similar across all sites, suggesting differences in body size may be due to selective harvest. Frogs from Site A, the flooded and harvested site, had no differences in survival rates between adults and juveniles. Site B populations shifted from a juvenile to adult dominated population after the dry-down. Dry-downs appeared to affect survival rates more than harvest. ^ Total mercury in frog leg tissue was highest in protected areas of Everglades National Park with a maximum concentration of 2.3 mg/kg wet mass where harvesting is prohibited. Similar spatial patterns in mercury levels were found among pig frogs and other wildlife throughout parts of the Everglades. Pig Frogs may be transferring substantial levels of mercury to other wildlife species in ENP. ^ In summary, although it was found that abundance and survival were reduced by dry-down, lack of adult size classes in Site A, suggest harvest also plays a role in regulating population structure. ^

Demographic effects of thatch harvest and implications for sustainable use of irapai palm (Lepidocaryum tenue, Mart.), by riverine communities in the Peruvian Amazon

Lepidocaryum tenue Mart. (Arecaceae) is a small, understory palm of terra firme forests of the western and central Amazon basin. Known as irapai, it is used for roof thatch by Amazonian peoples who collect its leaves from the wild and generate income from its fronds and articles fabricated from them. Increasing demand has caused local concern that populations are declining. Cultivation attempts have been unsuccessful. The purpose of this study was to investigate market conditions and quantify population dynamics and demographic responses of harvested and unharvested irapai growing near Iquitos, Peru. ^ Ethnobotanical research included participant surveys to determine movement of thatch tiles, called crisnejas, through Moronacocha Port. I also conducted a seed germination trial, and for four years studied five populations growing in communities with similar topography and soils but different land tenure and management strategies. Stage, survival, leaf production, and reproductive transitions were used to calculate ramet demographic rates and develop population projection matrices. ^ Weavers made an average of 20–30 crisnejas per day (90–130 leaves each), and earned US$0.09 to 0.70 each (US$1.80 to 21.00 per day). Average crisnejas per month sold per vendor was 2,955 with a profit range of US$0.05 to 0.32 per crisneja. Wholesalers worked with capital outlay from US$100 to 400, and an estimated ten to twenty vendors could be found at a given time. Consumers paid between US$0.23 to 1.20 per crisneja. Although differences in demographic rates by location existed, most were not significant enough to attribute to management. ^ After 60 months, mean seed germination rate was 19.5% in all media (37.9% in peat). Seedling survival was less than two percent after twelve months. Annual palm mortality was three percent, and occurred disproportionately in small (<50 cm) palms. Small palms grew more in height. Unharvested palms grew less than harvested palms. Large palms (≥50 cm) produced more leaves, were more likely to reproduce, and collectors harvested them more frequently. Reproductive potentials (sexual and asexual) were low. Population growth rates were greater than or not significantly different from 1.0, indicating populations maintained or increased in size. Current levels of irapai harvest appear sustainable. DNA analysis of stems and recruits is recommended to understand population composition and stage-specific asexual fecundity. ^

Effect of the environment on condition and quality of cultured blue mussels (Mytilus edulis) with reference to culture depth and post-harvest practices

The condition and quality of cultured blue mussels (Mytilus edulis) are affected by various environmental characteristics including temperature, salinity, food concentration, composition and year-to-year variability, waves, tides, and currents. Mussels are a keystone species in the ecosystem, affecting the surrounding environment through filtration, biodeposition and nutrient recycling. This study evaluated the effects of culture depth and post-harvest handling on cultured blue mussels in Newfoundland, Canada. Depth was examined over two years; three shallow water (5 m depth) and three deep water sites (15 m depth) were compared for environmental characteristics, mussel physiological stress response, growth, and biochemical composition. The area examined presented complex hydrodynamic characteristics; deep water sites appeared to be located more often near or within the pycnocline than shallow water sites. Deep water sites presented lower temperatures than shallow sites from spring to fall. Physiological stress response varied seasonally, but was unaffected by culture depth. In Year 1 shallow and deep water mussels presented similar growth, while in Year 2 deep water mussels showed better final condition. Lipid and glycogen showed seasonal variation, but no significant differences between shallow and deep water were noted. Fatty acid profiles showed a higher content of omega-3s PUFA in deep water sites at the end of Year 2. Under extreme weather conditions, deep water appeared to provide a more stable environment for mussel growth than shallow water. Harvested mussels were kept under ambient live-holding conditions for one month during the fall, winter, and spring seasons. They were compared to freshly harvested mussels for condition, biochemical profile and palatability. A progressive loss of dry tissue weight and an increase in water content were shown over the holding period during the fall and spring seasons, when compared to field controls. The biochemical analysis suggested seasonal changes; differences in triacylglycerol content were found in the spring season when compared with controls. The palatability data indicated that the panellists were unable to determine a difference between mussels kept in holding and those freshly harvested from the site. This study presents new knowledge for mussel farming, especially in terms of environmental interactions and deep water culture.

Nutritional status of lactating mothers and their children 6-23 months of age in pre- and post-harvest seasons in two agro-ecological zones of rural Ethiopia

The objective of this study was to assess seasonal variation in nutritional status and feeding practices among lactating mothers and their children 6-23 months of age in two different agro-ecological zones of rural Ethiopia (lowland zone and midland zone). Food availability and access are strongly affected by seasonality in Ethiopia. However, there are few published data on the effects of seasonal food fluctuations on nutritional status and dietary diversity patterns of mothers and children in rural Ethiopia. A longitudinal study was conducted among 216 mothers in two agro-ecological zones of rural Ethiopia during pre and post-harvest seasons. Data were collected on many parameters including anthropometry, blood levels of haemoglobin and ferritin and zinc, urinary iodine levels, questionnaire data regarding demographic and household parameters and health issues, and infant and young child feeding practices, 24 h food recall to determine dietary diversity scores, and household use of iodized salt. Chi-square and multivariable regression models were used to identify independent predictors of nutritional status. A wide variety of results were generated including the following highlights. It was found that 95.4% of children were breastfed, of whom 59.7% were initially breastfed within one hour of birth, 22.2% received pre-lacteal feeds, and 50.9% of children received complementary feedings by 6 months of age. Iron deficiency was found in 44.4% of children and 19.8% of mothers. Low Zinc status was found in 72.2% of children and 67.3% of mothers. Of the study subjects, 52.5% of the children and 19.1% of the mothers were anaemic, and 29.6% of children and 10.5% of mothers had iron deficiency anaemia. Among the mothers with low serum iron status, 81.2% and 56.2% of their children had low serum zinc and iron, respectively. Similarly, among the low serum zinc status mothers, 75.2% and 45.3% of their children had low serum in zinc and iron, respectively. There was a strong correlation between the micronutrient status of the mothers and the children for ferritin, zinc and haemoglobin (P <0.001). There was also statistically significant difference between agro-ecological zones for micronutrient deficiencies among the mothers (p<0.001) but not for their children. The majority (97.6%) of mothers in the lowland zone were deficient in at least one micronutrient biomarker (zinc or ferritin or haemoglobin). Deficiencies in one, two, or all three biomarkers of micronutrient status were observed in 48.1%, 16.7% and 9.9% of mothers and 35.8%, 29.0%, and 23.5%, of children, respectively. Additionally, about 42.6% of mothers had low levels of urinary iodine and 35.2% of lactating mothers had goitre. Total goitre prevalence rates and urinary iodine levels of lactating mothers were not significantly different across agro-ecological zones. Adequately iodised salt was available in 36.6% of households. The prevalence of anaemia increased from post-harvest (21.8%) to pre-harvest seasons (40.9%) among lactating mothers. Increases were from 8.6% to 34.4% in midland and from 34.2% to 46.3% in lowland agro-ecological zones. Fifteen percent of mothers were anaemic during both seasons. Predictors of anaemia were high parity of mother and low dietary diversity. The proportion of stunted and underweight children increased from 39.8% and 27% in post-harvest season to 46.0% and 31.8% in pre-harvest season, respectively. However, wasting in children decreased from 11.6% to 8.5%. Major variations in stunting and underweight were noted in midland compared to lowland agroecological zones. Anthropometric measurements in mothers indicated high levels of undernutrition. The prevalence of undernutrition in mothers (BMI <18.5kg/m2) increased from 41.7 to 54.7% between post- and pre-harvest seasons. The seasonal effect was generally higher in the midland community for all forms of malnutrition. Parity, number of children under five years and regional variation were predictors of low BMI among lactating mothers. There were differences in minimum meal frequency, minimum acceptable diet and dietary diversity in children in pre-harvest and post-harvest seasons and these parameters were poor in both seasons. Dietary diversity among mothers was higher in lowland zone but was poor in both zones across the seasons. In conclusion, malnutrition and micronutrient deficiencies are very prevalent among lactating mothers and their children 6-23 months old in the study areas. There are significant seasonal variations in malnutrition and dietary diversity, in addition to significant differences between lowland and midland agro-ecological zones. These findings suggest a need to design effective preventive public health nutrition programs to address both the mothers’ and children’s needs particularly in the preharvest season.

Local festivals, social capital and sustainable destination development: experiences in East London

This paper explores the nature of social capital arising from engagement in local festivals and the implications of this for the social sustainability of an emerging destination. Two case studies are developed from a longitudinal research project which investigates local festivals staged in the Hackney Wick and Fish Island area adjacent to Queen Elizabeth Olympic Park in East London, UK between 2008 and 2014. This area has been directly affected by extensive development and regeneration efforts associated with the staging of the London 2012 Olympic Games. The two festivals considered here respond to the challenges and opportunities arising for local people as the area changes. One festival aims to foster a sense of community by creating shared experiences and improving communication across diverse groups. The other draws together the cultural community, links them to the opportunities arising as the area emerges as a destination, and attracts visitors. These festivals increase social capital in the area, but its distribution is very uneven. The accrual of social capital exacerbates existing inequalities within the host community, favouring the “haves” at the expense of the “have nots”. There are tensions between the development of social capital and social sustainability in this emerging destination.

DESIGN, FABRICATION, AND PERFORMANCE CHARACTERIZATION OF MULTIFUNCTIONAL STRUCTURES TO HARVEST SOLAR ENERGY FOR FLAPPING WING AERIAL VEHICLES

Flapping Wing Aerial Vehicles (FWAVs) have the capability to combine the benefits of both fixed wing vehicles and rotary vehicles. However, flight time is limited due to limited on-board energy storage capacity. For most Unmanned Aerial Vehicle (UAV) operators, frequent recharging of the batteries is not ideal due to lack of nearby electrical outlets. This imposes serious limitations on FWAV flights. The approach taken to extend the flight time of UAVs was to integrate photovoltaic solar cells onto different structures of the vehicle to harvest and use energy from the sun. Integration of the solar cells can greatly improve the energy capacity of an UAV; however, this integration does effect the performance of the UAV and especially FWAVs. The integration of solar cells affects the ability of the vehicle to produce the aerodynamic forces necessary to maintain flight. This PhD dissertation characterizes the effects of solar cell integration on the performance of a FWAV. Robo Raven, a recently developed FWAV, is used as the platform for this work. An additive manufacturing technique was developed to integrate photovoltaic solar cells into the wing and tail structures of the vehicle. An approach to characterizing the effects of solar cell integration to the wings, tail, and body of the UAV is also described. This approach includes measurement of aerodynamic forces generated by the vehicle and measurements of the wing shape during the flapping cycle using Digital Image Correlation. Various changes to wing, body, and tail design are investigated and changes in performance for each design are measured. The electrical performance from the solar cells is also characterized. A new multifunctional performance model was formulated that describes how integration of solar cells influences the flight performance. Aerodynamic models were developed to describe effects of solar cell integration force production and performance of the FWAV. Thus, performance changes can be predicted depending on changes in design. Sensing capabilities of the solar cells were also discovered and correlated to the deformation of the wing. This demonstrated that the solar cells were capable of: (1) Lightweight and flexible structure to generate aerodynamic forces, (2) Energy harvesting to extend operational time and autonomy, (3) Sensing of an aerodynamic force associated with wing deformation. Finally, different flexible photovoltaic materials with higher efficiencies are investigated, which enable the multifunctional wings to provide enough solar power to keep the FWAV aloft without batteries as long as there is enough sunlight to power the vehicle.

Developing a commercial hot water treatment to control post-harvest rots on ‘Fiji Red’ papaya

Fiji exports approximately 800 t year-1 of 'Solo Sunrise' papaya marketed as 'Fiji Red' to international markets which include New Zealand, Australia and Japan. The wet weather conditions from November to April each year result in a significant increase in fungal diseases present in Fiji papaya orchards. The two major pathogens that are causing significant post-harvest losses are: stem end rot (Phytophthora palmivora) and anthracnose (Colletotrichum spp.). The high incidence of post-harvest rots has led to increased rejection rates all along the supply chain, causing a reduction in income to farmers, exporters, importers and retailers of Fiji papaya. It has also undermined the superior quality reputation on the market. In response to this issue, the Fiji Papaya industry led by Nature's Way Cooperative, embarked on series of trials supported by the Australian Centre for International Agricultural Research (ACIAR) to determine the most effective and economical post-harvest control in Fiji papaya. Of all the treatments that were examined, a hot water dip treatment was selected by the industry as the most appropriate technology given the level of control that it provide, the cost effectiveness of the treatment and the fact that it was non-chemical. A commercial hot water unit that fits with the existing quarantine treatment and packing facilities has been designed and a cost benefit analysis for the investment carried out. This paper explores the research findings as well as the industry process that has led to the commercial uptake of this important technology.

The effect of Lampara net on the catch rates and size of the fishing harvest of Rastrineobola argentae (mukene) in selected parts of Lake Victoria, Uganda

This study was undertaken in Napoleon gulf, and part of the off shore area of Lake Victoria Uganda in the landing site of Lufu in Buvuma district in the month of October 2015 for three days of sampling. It was conducted in four landing sites; Busana, Kikondo from Buikwe district and Lufu landing site from Buvuma district. The main aim was to determine the effect of Lampara net on the catch rate and size of the Rastrineobola argentae (mukene) harvested on Lake Victoria using various mesh sizes. The study focused on the 5mm and 10 mm mesh sizes of the Lampara net. A total of 109 boats were sampled; from the 5 mm mesh sizes indicated catch rates of 78-200 kg/boat/day and yet for 10 mm mesh size was at 248 kg/boat day. Statistical tests were carried out on the these two mesh sizes using One way Anova and indicated in catches was (Anova F=7.476; P<0.05) and for the price values was (Anova F=5.488 ; P<0.05). This is an indication that despite the fact that the mukene fishery is on the increase, a time will come when it also be depleted so a need to use the rightful fishing gear of 10mm mesh size is advisable for the biodiversity conservation.

Design and Pilot Study for an Efficient High-Throughput Automated Computer-Vision Guided Intelligent De-Calyxing Machine for Post-Harvest Strawberry Processing

Strawberries harvested for processing as frozen fruits are currently de-calyxed manually in the field. This process requires the removal of the stem cap with green leaves (i.e. the calyx) and incurs many disadvantages when performed by hand. Not only does it necessitate the need to maintain cutting tool sanitation, but it also increases labor time and exposure of the de-capped strawberries before in-plant processing. This leads to labor inefficiency and decreased harvest yield. By moving the calyx removal process from the fields to the processing plants, this new practice would reduce field labor and improve management and logistics, while increasing annual yield. As labor prices continue to increase, the strawberry industry has shown great interest in the development and implementation of an automated calyx removal system. In response, this dissertation describes the design, operation, and performance of a full-scale automatic vision-guided intelligent de-calyxing (AVID) prototype machine. The AVID machine utilizes commercially available equipment to produce a relatively low cost automated de-calyxing system that can be retrofitted into existing food processing facilities. This dissertation is broken up into five sections. The first two sections include a machine overview and a 12-week processing plant pilot study. Results of the pilot study indicate the AVID machine is able to de-calyx grade-1-with-cap conical strawberries at roughly 66 percent output weight yield at a throughput of 10,000 pounds per hour. The remaining three sections describe in detail the three main components of the machine: a strawberry loading and orientation conveyor, a machine vision system for calyx identification, and a synchronized multi-waterjet knife calyx removal system. In short, the loading system utilizes rotational energy to orient conical strawberries. The machine vision system determines cut locations through RGB real-time feature extraction. The high-speed multi-waterjet knife system uses direct drive actuation to locate 30,000 psi cutting streams to precise coordinates for calyx removal. Based on the observations and studies performed within this dissertation, the AVID machine is seen to be a viable option for automated high-throughput strawberry calyx removal. A summary of future tasks and further improvements is discussed at the end.

Natural recovery of the benthic nematode assemblages associated to Zostera noltii seagrass beds after physical disturbance caused by digging harvest activity

Seagrass beds are productive ecosystems that maintain high levels of biodiversity, making them susceptible to anthropogenic pressures such as bivalve harvesting. Nematodes are considered great ecological indicators as changes in their density, diversity and structure may represent changes in the environment. This experimental fieldwork aimed to assess the impact of the bivalve harvesting on the nematodes assemblage of a seagrass bed in the Mira estuary by simulating the digging activity. Two plots were subjected to the digging (D1 and D19) and two plots were control (C11 and C18). The sampling took place in five occasions: T0 – before digging; T1 – 14 days; T2 – 45 days; T3 – 75 days; and T4 – 165 days after digging. The results showed no significant difference in the nematode assemblages’ density, diversity and trophic composition between treatments and sampling times, evidencing their high tolerance for naturally stressed environments and to the level of digging they were exposed; Recuperação natural das comunidades de nematodes bentónicos associados aos povoamentos de Zostera noltii após atividade de marisqueio Resumo: As pradarias marinhas são ecossistemas produtivos que suportam elevados níveis de biodiversidade, pelo que estão sujeitos a pressões antropogénicas. Os nematodes são bons indicadores ecológicos pois respondem rapidamente a qualquer perturbação por alterações na densidade, diversidade e estrutura. Este trabalho experimental teve como finalidade o estudo da recuperação natural das comunidades de nematodes associados aos povoamentos de Zostera noltii pela simulação da atividade de marisqueio. Dois plots foram sujeitos a revolvimento (D1 e D19) e dois plots serviram como controlo (C11 e C18) e foram efetuadas amostragens em cinco ocasiões: T0 – antes do revolvimento; T1 – 14 dias; T2 – 45 dias; T3 – 75 dias; e T4 – 165 dias após revolvimento. Os resultados obtidos não mostraram diferenças significativas na diversidade, densidade e composição trófica das comunidades de nematodes entre tratamentos e tempos de amostragem, evidenciando a sua elevada tolerância a ambientes naturalmente dinâmicos e ao nível de revolvimento a que foram expostas.

Effect of post-harvest ozone treatments on the skin phenolic composition and extractability of red winegrapes cv Nebbiolo and Berbera

Mestrado Vinifera Euromaster - Instituto Superior de Agronomia - UL

Increasing the effectiveness of the land manure after irrigated rice harvest.

Este artigo apresenta o progresso na pesquisa de cultivo mínimo em área de arroz irrigado. É investigado um método de preparo do solo com rolo-faca em áreas de várzea, que é um cilindro com lâminas paralelas usadas para incorporar a palha no solo. A técnica proporciona a antecipação do preparo da terra para a instalação de pastagem durante o inverno e com melhoria no controle de pragas e redução do tempo de preparo e consumo de combustível nas operações. Requerer-se uma menor potência de tração do que métodos convencionais empregando arados e grade.