Crop Production in the East of Scotland - SASA

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Inputs and SustainabilityTable 5.1), but there are major arthropodpests. Wheat bulb fly (Delia coarctata) is acommon pest in the South East of Scotland,causing “deadheart” symptoms when larvaefeed on the main shoot. Since the eggswhich will result in damage in spring aredeposited during the preceding summer,preferentially on bare soil, the greatest riskis run by winter wheat crops after potatoes,peas, oilseed rape or set-aside. There is along history of wheat bulb fly damage inEast Lothian, Fife and Angus, but since theearly 1990s there has been an increase inthe number of eggs recorded, and in therange of the pest (e.g. to the Merse) (Evans,2000). This suggests that its incidence andseverity may be changing in response tochanges in climate and/or farming practice(e.g. set-aside and increased areas ofoilseed rape). Without an effectiveforecasting system, many farmers willcontinue with prophylactic, and in manycases unnecessary, insecticide applications(see Table 5.1).Of the main crops in the East of Scotland,the potato is most susceptible to the fullrange of pathogenic taxa, including anarray of viruses transmitted by leaf-feedingaphids (e.g. the peach-potato aphid Myzuspersicae); bacterial diseases such asblackleg (Erwinia carotovora); foliar fungaldiseases, notably late blight (Phytophthorainfestans); soil-borne nematodes (potatocyst nematodes (PCN) Globodera spp.) aswell as a wide array of fungal and bacterialdiseases of tubers in storage. By exploitingthe cool climate of the North of Scotland(slow build up of aphid populations) and acomprehensive set of strict regulations(restriction of cropping to PCN-free land;regular field inspections; pre- and postharvestdiagnosis of virus diseases etc.),Scotland maintains a highly-profitable seedtuber industry, supplying many overseascountries, particularly in the Mediterraneanzone. Nevertheless, this phytosanitaryapproach does not rule out the need forextensive chemical crop protection (e.g.Table 5.1Estimates of the total usage of pesticides on cereal crops in Scotland,1994, 1996 and 19981994 1996 1998InsecticidesPyrethroids 15,210 46,456 56,648Organophosphates 31,608 15,656 20,993Organochlorines - - 1,157Carbamates 4,192 1,962 2,650Unspecified or mixed formulation - 427 -All insecticides 51,010 64,501 81,448Molluscicides 17,025 8,841 30,586Fungicides 1,092,222 1,712,768 1,967,309Herbicides 1,011,474 1,315,092 1,354,105Growth regulators 295,233 388,787 422,748Seed treatments 779,010 830,133 799,005All pesticides 3,245,974 4,320,122 4,655,201Area planted (ha) 395,286 ha 449,298 ha 468,153 haThe data are expressed in terms of “spray hectares of active ingredients”.Source: Pesticide Usage in Scotland Reports. Arable Crops 1994, 1996, 1998. Edinburgh:Scottish Agricultural Science Agency.41
Crop Production in the East of Scotland42aphicides, protection against blight).Each crop species and cropping system hasits own characteristic weeds, some of whichcan be extremely difficult to control (e.g.wild oats, which are taxonomically, andtherefore biochemically, close to the majorcereal crops). Weeds are controlled byroutine spraying with the appropriateselective herbicide (Table 5.1), although allweeds can be controlled by a combinationof rotation and cultivation. Recent work onlow doses of herbicide, repeated only ifnecessary, has demonstrated how herbicideusage can be reduced withoutcompromising crop yield and quality.The extent of pesticide applications tocontrol the pests, diseases and weeds ofcereal crops in Scotland is shown in Table5.1 (Note that several of the values for“spray areas” are greater than the actualarea cropped because many crops receivetwo or three applications per season). Thepreponderance of herbicide and fungicideapplications reflects the practical problemsof cereal growing in a cool climate, but thedata also show a distinct rise in the use ofinsecticides, which may be related toclimate change (increased winter survivaland higher spring populations of insects).Work on integrated farming systems hasdemonstrated some of the ways in whichpesticide applications can be reduced.Nevertheless, there is no immediateprospect of a substantial reduction in thelevel of application of pesticides, if existingyields are to be maintained.Risks to humans from pesticides appliedaccording to codes of best practice, arejudged to be low, and the accumulation ofpesticide residues in the human diet ismonitored by government scientists toensure food safety. On the other hand,pesticides inevitably have a deleteriouseffect on biodiversity in crops and theirmargins.Inputs: EnergyFossil fuel is required for the chemicalsynthesis of fertilisers and pesticides; forthe transport and distribution ofagrochemicals and other supplies; fortraction (direct fuel use); and for themanufacture of machinery; before anyaccount is taken of the large energy costsof transforming, transporting andmarketing the farm yield into food or otherproducts. For example, Slesser (1975)calculated that the fossil energy required tomeet the direct fuel use, fertiliser andpesticide needs of a Scottish spring barleycrop was equivalent to around 20% of thesolar energy captured in the harvestedgrain; with the intensification of cerealproduction, these energy costs will be atleast as high now. Intensive agriculture, aspresently practised worldwide, needs to beprimed with oil to secure the acquisition ofsolar energy (see the pioneering studies ofPimental & Pimental, 1979).Implementation of the Kyoto Protocol ongreenhouse gas emissions may have asignificant effect on the volume ofagricultural produce which is transportedover long distances, particularlycommodities with a high moisture content.The competitiveness of agriculture in theEast of Scotland might benefit from anysuch change.Predictable ChangeThe next step in evaluating thesustainability of arable agriculture inScotland is to review predictable changes inthe physical and biological environment,and their potential impacts.Current forecasts of long-term climatechange in Scotland are for highertemperatures (typically 1 - 3ºC) particularlyin winter, higher winter rainfall, and drier
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Crop Production in the East of Scotland - SASA

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