2,559 research outputs found
Kemiska vÀxtskyddsmedel i jordbruket : en förutsÀttning för tryggad livsmedelsförsörjning?
Jordbruket stĂ„r inför stora utmaningar under de kommande decennierna. Jordens ökande befolkning driver upp efterfrĂ„gan pĂ„ livsmedel och biobrĂ€nslen frĂ„n jordbruket. Men jordbrukets produktion bör inte öka genom att expandera till ytan eftersom det skulle ske pĂ„ bekostnad av viktiga naturliga habitat. Den totala ytan som finns att nyttja för livsmedelsproduktion kommer dĂ€rför sannolikt att minska i framtiden. Om mer livsmedel ska produceras pĂ„ mindre yta mĂ„ste produktiviteten per ytenhet öka. Historiska produktivitetsökningar i jordbruket har i stor utstrĂ€ckning tillskrivits kemiska insatsmedel i form av gödnings- och vĂ€xtskyddsmedel men EU har beslutat att unionens medlemslĂ€nder ska halvera anvĂ€ndandet av kemiska vĂ€xtskyddsmedel till Ă„r 2030. Kritiska röster menar att jordbrukets förmĂ„ga att producera livsmedel kommer minska, vilket kan komma att riskera livsmedelstryggheten, om EU:s mĂ„lsĂ€ttning nĂ„s. Syftet med den hĂ€r studien var att redogöra för i vilken utstrĂ€ckning jordbrukets avkastning Ă€r beroende av vĂ€xtskydd i allmĂ€nhet och kemiska vĂ€xtskyddsmedel i synnerhet. Genom en litteraturstudie sammanstĂ€lls, presenteras och analyseras tidigare forskning inom omrĂ„det. Resultaten visar att jordbruket Ă€r helt beroende av vĂ€xtskydd och att avkastning uppskattningsvis skulle minska med 50â80 % om inget vĂ€xtskydd bedrevs. Jordbrukets avkastning Ă€r i dagslĂ€get Ă€ven mycket beroende av kemiska vĂ€xtskyddsmedel. Beroende pĂ„ hur stor andel av anvĂ€ndandet av de kemiska vĂ€xtskyddsmedlen som fasas ut och i vilken utstrĂ€ckning andra förĂ€ndringar av odlingssystemen genomförs, kommer effekterna pĂ„ avkastningen att bli mer eller mindre stora. Hur stora dessa effekter skulle bli Ă€r svĂ„rt att förutse eftersom det rĂ„der en brist pĂ„ forsknings- och dataunderlag. Försök att göra skattningar frĂ„n en rad kĂ€llor visar att om kemiska vĂ€xtskyddsmedel helt fasas ut och inga andra förĂ€ndringar av odlingssystemen genomförs kommer minst 34 % av jordbrukets befintliga avkastning att gĂ„ förlorad. Om odlingssystemen förĂ€ndras för att kompensera för utfasningen kommer skördeförlusterna kunna begrĂ€nsas till, i bĂ€sta fall, cirka 20 %. En bred omstĂ€llning till ett jordbruk som drivs enligt det integrerade vĂ€xtskyddets principer och som halverar sitt anvĂ€ndande av kemiska vĂ€xtskyddsmedel skulle uppskattningsvis leda till en minskad avkastning om 5â13 %. För att framgĂ„ngsrikt minska anvĂ€ndandet av kemiska vĂ€xtskyddsmedel och samtidigt upprĂ€tthĂ„lla jordbrukets avkastning Ă€r det viktigt att bĂ„de öka antalet grödor i vĂ€xtföljden och antalet vĂ€xtskyddsĂ„tgĂ€rder, bĂ„de preventiva och kurativa, i linje med det integrerade vĂ€xtskyddets principer. Ett halverat anvĂ€ndande av kemiska vĂ€xtskyddsmedel kommer sannolikt leda till att produktionen av livsmedel minskar Ă€ven om mycket kan göras för att minskningen ska bli sĂ„ liten som möjligt. Det betyder dock inte nödvĂ€ndigtvis att framtidens livsmedelstrygghet Ă€r hotad eftersom livsmedelsproduktionen bara Ă€r den första lĂ€nken av flera, i en lĂ„ng kedja, frĂ„n jord till bord.The agricultural sector faces major challenges in the coming decades. The world's increasing population is driving up the demand for food and biofuel production. But the availability of agricultural land is limited, and production should not expand into the few natural habitats that still remain. The total area that can be used for food production is therefore likely to decrease in the future. If more food is to be produced on less land, productivity per area unit must increase. Major increases in productivity within the agriculture sector have historically been largely attributed to chemical inputs, i.e. fertilizers and pesticides, but the EU has decided that the Union's member states must reduce their use of pesticides by 50 % by the year 2030. Critics claim that food production will decrease, and threaten food security, if the targets of the EU are reached. The purpose of this study was to account for the extent to which crop yields are dependent on plant protection in general and chemical pesticides in particular. By using the methods of a literature review, previous research within the field is compiled, presented and analysed. The results of the review show that the agricultural sector is completely dependent on crop protection and that yields are estimated to decrease 50â80 % in the absence of crop protection. Crop yields are currently also highly dependent on pesticides. Depending on the extent to which the use of pesticides is phased out, and to what extent other changes to the cropping systems are carried out, yield effects will vary. How big these effects would be is difficult to predict because of the lack of available research and data. Attempts to make estimates from a range of sources show that if pesticides are completely phased out and no other changes to the cropping systems are implemented, at least 34 % of current yields will be lost. If the cropping systems are adjusted to compensate for the reduced use of pesticides, yield losses can be limited to, at best, around 20 %. A broad transition to the practices and principles of integrated pest management, parallel to a 50 % reduction in the use of pesticides, would lead to an estimated yield reduction of 5â13 %. In order to successfully reduce the use of pesticides while at the same time maintaining crop yields, it is important to increase both the number of crops in the crop rotation and the number of plant protection methods, both preventive and curative, in line with the principles of integrated pest management. A 50 % reduction in the use of pesticides will likely lead to a reduction in food production, although much can be done to make the reduction as small as possible. However, this does not necessarily mean that future food security is threatened since food production is only the first of several links in a long chain from farm to fork
An overview of economics and regulation
To very briefly conclude: We could summarise the contents of this essay with stating that economic theory and empirical research is a valuable tool in regulation. It might be difficult to apply or to comprehend the implications of economic research in a regulatory context, but it would at least be fruitful in the long run to develop
coherent methods to do this
Self-determination theory and the role of political interest in adolescents' sociopolitical development
SHARE Working Paper Series 62-2021: Adjustment of daily activities to restrictions and reported spread of the COVID-19 pandemic across Europe
Pubertal maturation and affective symptoms in adolescence and adulthood: evidence from a prospective birth cohort
The higher prevalence of affective symptoms among women compared to men emerges in adolescence, and it has been associated with pubertal maturation. However, it remains unclear whether pubertal timing has long-term influences on affective symptoms. Using data from the British 1946 birth cohort, we investigated whether pubertal timing was associated with affective symptoms over the life course, distinguishing those with symptoms in adolescence only, symptoms in adulthood only, and symptoms in both adolescence and adulthood. In females, there was no evidence that early pubertal maturation was a risk factor for affective symptoms. However, those with particularly late menarche (â„15 years) showed a lower risk of adult-onset affective symptoms (OR = 0.54, 95% CI: 0.31, 0.95). This effect of late pubertal timing was not explained by a range of socio-behavioural factors. In contrast, in males, late pubertal timing was associated with increased risk of adolescent-onset affective symptoms that tracked into adulthood (OR = 2.10, 95% CI: 1.44, 3.06). This effect was partly explained by low pre-pubertal BMI. Sex-specific effects of pubertal timing on the long-term risk of affective symptoms might be due to different effects of gonadal hormonal on the CNS, as well as different social experiences during puberty
Temperature stability of intersubband transitions in AlN/GaN quantum wells
Temperature dependence of intersubband transitions in AlN/GaN multiple
quantum wells grown with molecular beam epitaxy is investigated both by
absorption studies at different temperatures and modeling of conduction-band
electrons. For the absorption study, the sample is heated in increments up to
C. The self-consistent Schr\"odinger-Poisson modeling includes
temperature effects of the band-gap and the influence of thermal expansion on
the piezoelectric field. We find that the intersubband absorption energy
decreases only by meV at C relative to its room temperature
value
Why do some adolescents encounter everyday events that increase their civic interest whereas others do not?
Nursing technique and growth environment of Rabbit fish (Siganus guttatus) in the area of Tam Giang lagoon, Thua Thien Hue
Summary
In the area to the east of Hue city, in Vietnam, lays Tam Giang lagoon, one of Asia's largest lagoons, with an area of 22,000 hectares. This lagoon is suitable for aquaculture. One reason for this is because the salinity differs from sweet to salty in different parts of the lagoon. The Vietnamese Government advocates an increase in environmentally-friendly aquaculture and the fish Siganus guttatus (Rabbit fish) is a candidate for this. This fish eats mainly algae and can be cultivated in a polyculture. The purpose of this master thesis was to investigate how the fish S. guttatus are cultivated in nurseries. Focus was set on a farm located near the town of Tuan An, which cultivated the fish in cement tanks. What would be examined was growth in length and weight and various parameters of water quality where the fish were held. These results would then be compared to farms where fish were reared in earthen ponds on the shores of the Tam Giang lagoon. Only water quality and interviews with the farmers were made on the farms rearing S. guttatus in earthen ponds. Also an economic evaluation would be performed for the different farms. One nursery (farm 1) rearing S. guttatus in cements tanks was visited during an 8 week period. During these 8 weeks the fish grew 3.1 cm and 1.7 g. The mean water parameters were: temperature: 28.4 ° C, salinity: 20.6 â°, alkalinity: 140 ppm, pH: 7.7, DO 4.5 mg / L, TAN: 0.4 ppm. Three other farms (farm 2, 3 and 4) were visited for interviewing the farmer cultivating Rabbit fish in earthen ponds. At 2 of those farms (farm 2 and 3) also the water quality was analysed according to the same parameters as farm 1. The results from farm 2; temperature: 30 °C, salinity: 13 â°, alkalinity: 60 ppm, pH: 8, DO: 3 mg/L, TAN: 0.2 ppm.
The results from farm 3; temperature: 32 °C, salinity: 16 â°, alkalinity: 120 ppm, pH: 7.5, DO: 4 mg/L, TAN: 0.2 ppm. The management on the farms differed on some points. Farm 1 produced its own concentrate feed during the first month, consisting of fish meal, rice bran, cassava root meal, vitamins and probiotic (Bacillus subtilis). After the first month the fish got fed the same as on the other farms; industrially produced pelleted concentrate feed. In Addition, the fish were fed seaweed from the family of Gracilaria. None of the farms added chemicals to the ponds during cultivation of the Rabbit fish. One farm added saponins to the water between different cultivation batches. This to eradicate the fish that had swam in to the pond when the pond was refilled with new water. Two of the farms changed the pond water regularly, while a third added water from the lagoon to the pond after heavy rain. The fourth farm changed nothing in the pond during the rearing period.
Profits did not differ significantly between the farms that were reared in earthen ponds. However, the farm with cement tanks produced much higher profits per square meter. It was difficult to draw conclusions about differences between the different farming methods because of too few data.Sammanfattning
I omrÄdet öster om staden Hue i Viet Nam ligger lagunen Tam Giang lagoon, vilken Àr en av Asiens största laguner med en area pÄ 22 000 ha. Denna lagun lÀmpar sig vÀl för vattenbruk dÄ salthalten skiljer sig frÄn söt till salt beroende pÄ var i den man befinner sig. Den Vietnamesiska regeringen föresprÄkar en ökning av miljövÀnligt vattenbruk och fisken Siganus guttatus Àr en kandidat för detta. Denna fisk Àter frÀmst alger och gynnas av att födas upp polykultur. Syftet med detta arbete var att undersöka hur denna fisk odlas, frÄn fÄngst i det vilda vid 1 mÄnads Älder och upp till ca 4 mÄnaders Älder. Fokuseringen kom att ligga
2
speciellt pĂ„ en gĂ„rd (gĂ„rd 1) som odlade fisken i cement tankar och var belĂ€gen nĂ€ra staden Tuan An. Det som skulle undersökas var tillvĂ€xt i lĂ€ngd och vikt samt olika parametrar pĂ„ vattenkvaliteten i de cement tankar dĂ€r fisken hölls. Detta hĂ„llningssĂ€tt skulle sedan jĂ€mföras med 3 gĂ„rdar dĂ€r fiskar föddes upp i grĂ€vda jord-dammar invid stranden till Tam Giang lagoon. DĂ€r undersöktes vattenkvalitet (gĂ„rd 2 och 3) samt skötsel (alla 3 gĂ„rdar). Ăven en ekonomisk berĂ€kning skulle utföras för de 4 olika gĂ„rdarna.
GĂ„rd 1 besöktes under 8 veckor och tillvĂ€xten i lĂ€ngd och vikt pĂ„ fiskarna var som följer; 3.1 cm samt 1.7 g. MedelvĂ€rdet för vatten parametrarna var; temperatur: 28.4 °C, salinitet: 20.6 â°, alkalinitet: 140 ppm, pH: 7.7, löst syre (DO): 4.5 mg/L, totala ammoniak kvĂ€vet (TAN): 0.4 ppm. Resultat frĂ„n mĂ€tning av vattenkvaliteten pĂ„ gĂ„rd 2; temperatur: 30 °C, salthalt: 13 â°, alkalinitet: 60 ppm, pH: 8, DO: 3 mg/L, TAN: 0.2 ppm.
Resultat frĂ„n mĂ€tning av vattenkvaliteten pĂ„ gĂ„rd 3; temperatur: 32 °C, salthalt: 16 â°, alkalinitet: 120 ppm, pH: 7.5, DO: 4 mg/L, TAN: 0.2 ppm.
Skötseln mellan gÄrdarna skiljde sig pÄ nÄgra punkter. GÄrd 1 tillverkade sitt eget koncentrat-foder innehÄllande fiskmjöl, riskli, cassavarots-mjöl, vitaminer och probiotika under den första mÄnaden. DÀrefter utfodrades fiskarna likadant som pÄ de andra gÄrdarna; med industriellt producerat, pelleterat, koncentrat-foder. Utöver detta utfodrades fiskarna med vattenvÀxter frÄn familjen Gracilaria. Under odlingsperioden tillsatte inga av gÄrdarna nÄgra kemikalier till vattnet. En av gÄrdarna tillsatte dÀremot saponiner mellan fiskodlings- omgÄngarna. TvÄ av gÄrdarna bytte vatten regelbundet, medan en tredje tillsatte vatten frÄn lagunen efter kraftiga regn. Den 4:e gÄrden förÀndrade ingenting i dammen under uppfödningsperioden.
Ekonomin skiljde sig inte mycket mellan de gÄrdar som hade uppfödning i dammar. DÀremot hade gÄrden med uppfödning i cement tankar en mycket högre vinst per kvadrat meter vid jÀmförelse med de andra gÄrdarna. Det var dock svÄrt att dra slutsatser om skillnader mellan de olika uppfödningssÀtten pÄ grund av för fÄ data
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