Lämmastikväetise ja sordi mõju kahjurite arvukusele ja nende parasiteerituse tasemele talirapsil
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Kuupäev
2015
Kättesaadav alates
Autorid
Ajakirja pealkiri
Ajakirja ISSN
Köite pealkiri
Kirjastaja
Abstrakt
Rapsi külvipinna pidev suurenemine Eestis on loonud eeldused ristõielistele spetsialiseerunud
kahjurite arvukuse tõusuks. Rapsi saagi tõstmiseks kasutatakse suurtes kogustes väetisi ja
kahjurite tõrjeks insektitsiide. Tihti tehakse seda mullaviljakust ja kahjurite arvukust
kontrollimata. Samas võivad insektitsiidid lisaks kahjuritele hävitada ka neutraalseid ja
kasulikke lülijalgseid, sealhulgas nende kahjurite looduslikke vaenlaseid. Ühtedeks sellisteks
kahjurite looduslikeks vaenlasteks on parasitoidid. Teatud tingimustel on parasitoidid
võimelised hoidma kontrolli all kahjurite populatsiooni suurust rapsipõldudel. Kahjurite ja
parasitoidide arvukust põllul võivad mõjutada ka erinevate lämmastikväetiste koguste
kasutamine.
Käesoleva uurimustöö eesmärgiks oli leida, kas ja kuidas mõjutavad erinevad
lämmastikväetiste kogused kahel erineval talirapsi sordil saagikust, naeri-hiilamardika ja
kõdra-peitkärsaka arvukust ning nende parasiteerituse taset. Uurimustöö aluseks olid
põldkatsed talirapsidega ’Silvia’ ja ’Pastell’, mis viidi läbi Jõgevamaal. Taimedega läbi viidud
katsete tulemused näitasid, et sordil ’Silvia’ mõjutasid erinevad lämmastikukogused taimede
arvu m
2
, kõtrade arvu taimel ja rapsi seemnete saagikust, sordil ’Pastell’ aga mõjutasid
erinevad kogused rapsi seemnete saaki. Entomoloogiliste katsete tulemustes leiti, et sordil
’Silvia’ mõjutasid erinevad lämmastikukogused naeri-hiilamardika vastsete ja kõdrapeitkärsaka
poolt kahjustatud kõtrade arvu, sordil ’Pastell’ aga ainult kõdra-peitkärsaka poolt
kahjustatud kõtrade arvu.
Katse tulemustest võis järeldada, et väetamine lämmastiku kogusega 100 kg/ha andis parima
tulemuse. 100 kg/ha lämmastiku kogusega olid ühtemoodi tasakaalus keskkonnasäästlikkusele
ja kahjurite tõrjele suunatud huvid.
The increase in cultivation of oilseed rape has in turn provided good conditions for the population growth of the cruciferous pests. Large amounts of fertilizers and insecticides are being used to increase the oilseed rape yield and cope with the expanding population of pests. Chemicals are often used prophylactically without the regard of threshold levels, thus harming the environment and killing beneficial insects, including predators and parasitoids that can control the population size of oilseed rape pests. Beneficial insects, like parasitoids, are able to control the pest population biologically. This decreases the need for using insecticides and is therefore good for the environment in general. The aim of this study was to compare the impact of different amounts of nitrogen fertilizer on crop yield, abundance of pests and their larval parasitism levels. The study was carried out on experimental fields of two cultivars of winter oilseed rape, ’Silvia’ and ’Pastell’. The data was collected about the amounts of plants on a square meter, amount of seedpods per plant, crop yield and abundances of pollen beetle, cabbage seed weevil and the level of their parasitism. The results of this study show that winter oilseed rape ’Silvia’ was affected by different levels of nitrogen in numerous aspects – the amount of plants per square meter and seedpods per plant, crop yield, the abundance of pollen beetle larvae and cabbage seed weevil. In the case of ’Pastell’ nitrogen levels affected the crop yield and the abundance of cabbage seed weevil. Parasitism levels of both pests were not affected by the differences in nitrogen levels. The results show that different amounts of the nitrogen fertilizer have certain effects on some aspects of this study. It is possible to conclude that the best amount of nitrogen fertilizer to use on both, ’Silvia’ and ’Pastell’, is 100 kg per hectare. This amount gives the best correlation between low abundance level of pests and high levels of crop yield. Lower amounts of fertilizers are also less harmful for the environment.
The increase in cultivation of oilseed rape has in turn provided good conditions for the population growth of the cruciferous pests. Large amounts of fertilizers and insecticides are being used to increase the oilseed rape yield and cope with the expanding population of pests. Chemicals are often used prophylactically without the regard of threshold levels, thus harming the environment and killing beneficial insects, including predators and parasitoids that can control the population size of oilseed rape pests. Beneficial insects, like parasitoids, are able to control the pest population biologically. This decreases the need for using insecticides and is therefore good for the environment in general. The aim of this study was to compare the impact of different amounts of nitrogen fertilizer on crop yield, abundance of pests and their larval parasitism levels. The study was carried out on experimental fields of two cultivars of winter oilseed rape, ’Silvia’ and ’Pastell’. The data was collected about the amounts of plants on a square meter, amount of seedpods per plant, crop yield and abundances of pollen beetle, cabbage seed weevil and the level of their parasitism. The results of this study show that winter oilseed rape ’Silvia’ was affected by different levels of nitrogen in numerous aspects – the amount of plants per square meter and seedpods per plant, crop yield, the abundance of pollen beetle larvae and cabbage seed weevil. In the case of ’Pastell’ nitrogen levels affected the crop yield and the abundance of cabbage seed weevil. Parasitism levels of both pests were not affected by the differences in nitrogen levels. The results show that different amounts of the nitrogen fertilizer have certain effects on some aspects of this study. It is possible to conclude that the best amount of nitrogen fertilizer to use on both, ’Silvia’ and ’Pastell’, is 100 kg per hectare. This amount gives the best correlation between low abundance level of pests and high levels of crop yield. Lower amounts of fertilizers are also less harmful for the environment.
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