Browsing by Subject "typenotto"
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(2020)Ilmastonmuutos tuo mukanaan Suomeen äärioloja, jotka lisäävät typen huuhtoutumista, mutta myös mahdollisuuksia pidempinä ja lämpimimpinä kasvukausina. Viimeisen kahdenkymmenen vuoden aikana lajikejalostus ei ole kuitenkaan lisännyt käytännön satotasoja, vaan sadot ovat jopa taantuneet. Laskeneet satotasot eivät selity pelkästään laskeneilla typpilannoitustasoilla, ja satokuilua onkin lähdetty ratkaisemaan monimuotoisemmalla viljelykierrolla, joihin sisältyy esimerkiksi härkäpapua. Tutkimuksen tavoitteena oli selvittää esikasvina toimineen härkäpavun (Vicia faba L.) vaikutusta maaperän liukoisiin typpivaroihin ja seuraavien viljelykasvustojen typpidynamiikkaan. Tutkimus toteutettiin Haltialan pellolla satunnaistettuna täydellisten lohkojen kerrannekokeena, jossa käsittelynä oli yhteensä kuusi kasvia ja neljä lannoitustasoa. Kasvustoista mitattiin lehtivihreäpitoisuus, lehtialaindeksi (LAI) sekä määritettiin kuiva-aineen kehittyminen ja koeruuduista otettiin maanäytteet vähintään viidesti kasvukauden aikana. Biomassamääritysten pohjalta analysoitiin kasvinosien typpipitoisuudet ja laskettiin typpisadot. Maanäytteet uutettiin (2M KCl) NH4+- ja NO3--N-pitoisuuksien määrittämiseksi. Kasvustojen typpidynamiikkaa (NUE, UPE, UTE, NHI), typpisatoja ja koeruutujen mineralisaatiota sekä mineraalityppipitoisuuksia vertailtiin lannoitus ja esikasvi taustatekijöinä. Lämmin ja kuiva kasvukausi viivästytti kasvustojen sulkeutumista ja epätasaisuus vaikutti tuloksiin enemmän kuin esikasvi tai lannoitus. Lannoittamattomat kasvustot eivät eronneet tilastollisesti biomassaltaan tai typenotoltaan lannoitetuista. Kasvien typenotto vaikutti enemmän maaperän NO3--N kuin NH4+-N-pitoisuuksiin. Härkäpapuesikasvi lisäsi kauran lehtialan kestoa (LAD). Laskennallinen mineralisaatio oli suurin nollalannoitusruuduissa, keskimäärin 127 N kg ha-1. Kasvustojen UPE, UTE ja NUE jäivät pieniksi maan pintahorisontin ollessa lakastumisrajalla koko kesän. Härkäpavulla on hyvin todennäköisesti vaikutusta maan typpivaroihin, mutta tarkemmat arviot vaativat syvemmälle maahan ulottuvia mittauksia ja edullisemman kasvukauden.
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(2023)Long-term, one-sided cultivation of crops has become more common in farming systems in recent decades, but at the same time, it has had negative impacts on soil structure, soil carbon reserves and the biodiversity of farming systems. Pea (Pisum sativum L.) is a legume that can be used to diversify crop rotations and improve protein self-sufficiency. Pea can symbiotically fix nitrogen from the atmosphere with the help of nitrogen-fixing Rhizobium bacteria living in its root nodules, and convert it into usable forms for plants, thus reducing the need to use industrial fertilizers. The following crop may also benefit from the organic nitrogen derived from the pea crop residues and pea’s ability to reduce pest pressure on cereals. The aim of this study was to study the pre-crop effects of pea on the formation of dry matter and nitrogen yields of oat (Avena sativa L.) and rapeseed (Brassica napus L.). The study was conducted as a field experiment in Haltiala with a completely randomized block design in four replicates. The study included four oat treatments (fertilized with 90 kg (N) ha-1 and either oat, pea or pea-rapeseed mixture as a pre-crop, and unfertilized oat with a pea-rapeseed mixture as a pre-crop) and two rapeseed treatments (pea as a pre-crop, unfertilized or fertilized with 90 kg (N) ha-1). In the study, the pre-crop did not affect the amount or formation of dry matter or nitrogen yield of oats and rapeseed. The effect of fertilization on the formation of dry matter and nitrogen yield was also small, but the maximum rates of dry matter accumulation and nitrogen uptake occurred earlier in fertilized than in non-fertilized treatments. Although pea as a pre-crop did not significantly affect the amount of dry matter and nitrogen yield of the crops during the growing season, it did not either affect them negatively compared to the monoculture oat because their yields were similar. Drought in June and July limited the release of nitrogen for plant use, which explains the effect of both the pre-crop and the fertilization treatment being rather small in the dry matter and nitrogen yield of oats and rapeseed. Pea very likely has a positive effect on the growth of the following crop, but further research is needed in different soil types and in more favorable weather conditions.
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(2017)The soil mineral nitrogen content is affected by many factors such as nitrogen fertilizer, fertilization and cultivated plant species. The effects of these factors on soil mineral nitrogen content were examined and the research was conducted at the Viikki Research Farm during 2013–2015. The possibility of using soil mineral nitrogen content and nitrogen balance to optimise nitrogen fertilization was also studied as well as the leaching of mineral nitrogen during winter and the factors affecting leaching. The soil type of the experimental area was clay loam in topsoil and sandy loam in subsoil. Soil samples were taken in the spring before tillage and in the autumn before soil freezing from topsoil (0-20 cm) and subsoil (30-50 cm). Ammonium and nitrate were extracted from soil samples with 2 M KCl. Plant species and fertilization changed every year, but fertilization followed the regulations for the subsidies of agricultural environment and all the fertilizers and cultivars were commercially available in Finland. The nitrogen content of the seed and forage samples were determined. The actual nitrogen yield and nitrogen balance were calculated. The expected nitrogen yield and nitrogen balance were calculated with the common nitrogen contents of seeds published by the Finnish Agency for Rural Affairs and compared to the actual nitrogen yield and nitrogen balance, but no differences were found. Soil mineral nitrogen content, nitrogen balance and nitrogen yield varied a lot from year to year which was partly caused by the differences between the growing seasons and winters as well as the changes of cultivated plants and fertilization. The soil mineral nitrogen content was smaller in the spring (33 N kg/ha) than in the autumn (55 N kg/ha). Grass took more nitrogen than the other plant species. The soil nitrate content was smaller under growing grass than harvested plant stand in the autumn and the ammonium content was greater under growing grass than other plant species in the spring. The soil mineral nitrogen content was reduced and differences between treatments were moderated during the winter, which was probably caused by leaching. Fertilization had no direct effect on soil mineral nitrogen content. Increasing nitrogen fertilization increased nitrogen balance, but there was no correlation between nitrogen balance and soil mineral nitrogen content.
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