Browsing by study line "Maaperä- ja ympäristötiede"
Now showing items 1-7 of 7
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(2022)Runsas väkilannoitetypen käyttö kasvien typen tarpeen tyydyttämiseksi ja runsaampien satojen saamiseksi sekä karjatalouden keskittyminen tietyille alueille, ovat lisänneet maataloudesta aiheutuvaa typen vesistökuormitusta. Lisääntynyt ympäristötietoisuus on kuitenkin nostanut kestävyyden ja ilmastoviisaan ruoantuotannon osaksi maatalouden tavoitteita, mikä on lisännyt eloperäisten tai kierrätysaineista valmistettujen tai yhteiskunnan sivuvirroista valmistettujen maanparannusaineiden käyttöä. Maanparannusaineina käytettävien tuotteiden kenttä on laaja ja niiden vaikutukset moninaiset, mutta biohiilestä on etsitty ratkaisua liukoisen nitraatin (NO3-) ympäristökuorman vähentämiseksi. Tämän maisterintutkielman tavoitteena oli kartoittaa kahden kaupallisen biohiilen sekä synteettisen hiilipolymeerin vaikutusta nitraatin pidättymiseen, ja toisaalta pidättymisen vaikutusta nitraatin käyttökelpoisuuteen kasveille. Tutkimus koostui kahdesta osasta, josta ensimmäisessä osassa tutkittiin maanparannusaineiden kykyä pidättää maanparannusaineisiin esimuhitettua nitraattia peräkkäisten uuttojen avulla. Toinen osa koostui kasvatuskokeesta, jossa tarkasteltiin maanparannusaineisiin mahdollisesti pidättyneen nitraatin käyttökelpoisuutta ohralle kasvin kasvun ja klorofyllipitoisuuksien avulla. Uuttokokeen perusteella saksanpähkinänkuoresta valmistettu biohiili (Biohiili 1) osoitti kykyä pidättää nitraattia, koska kahden ensimmäisen uuton aikana biohiilestä ei vapautunut käytännössä lainkaan esimuhituksessa lisätystä nitraatista. Sen sijaan kuusesta valmistettu biohiili (Biohiili 2) ja hiilipolymeeri vapauttivat merkittävästi ja asteittain vähemmän nitraattia peräkkäisissä uutoissa. Kolmen peräkkäisen uuton jälkeen Biohiili 1:sta uuttui vain 1,8 % esimuhituksessa lisätystä typestä, kun taas Biohiili 2:sta uuttui 80 %. Hiilipolymeerillä uuttuneen nitraatin määrä oli yli 100 %, josta osa NO3-N oli peräisin itse tuotteesta. Kasvatuskokeen perusteella typpi ei todennäköisesti ollut ohrien kasvua rajoittava tekijä, ja vaikka Hiilipolymeeri sisälsi itsessään merkittävästi enemmän epäorgaanista typpeä, se ei johtanut korkeam-paan biomassaan. Erot ohrien biomassan ja klorofyllin kehityksessä liittyvät todennäköisimmin muihin ympäristötekijöihin. Mahdollisia selityksiä ovat fysikaalis-kemialliset erot kasvualustassa, mukaan lukien kasvualustan pH (biohiilillä emäksinen ja Hiilipolymeerillä hapan), irtotiheys ja huokoisuus, mutta lisäksi kesällä 2021 koettu poikkeuksellisen kuuma sää vaikutti todennäköisesti myös ohran kasvuun. Biohiilet ovat potentiaalisia maanparannusaineita vähentämään maataloudesta aiheutuvaa typen ympäristökuormitusta, ilman että ne vaikuttavat kasveille käyttökelpoisen typen määrään merkittävästi. Biohiilen valmistuksessa käytetty raaka-aine sekä valmistusprosessi vaikuttavat kuitenkin merkittävästi lopulliseen tuotteeseen, minkä vuoksi tarvitaan lisää tutkimusta ominaisuuksista, jotka vaikuttavat nitraatin pidättymisen tehokkuuteen.
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(2024)In agricultural soils, Nitrogen (N) is an essential nutrient in crop production, and its supply comes from various pools. Understanding the N pools in soil could help farmers make better decisions about N fertilisation, increase productivity, reduce costs, and decrease environmental impacts. N is a challenging element to track in soil due to its seven oxidation states that are large-ly cycled and intermediated by soil organisms between various organic, mineral, and gaseous forms. This thesis aims to find whether C farming practices accumulate N in soil through investi-gating the size of soil N pools and how they relate to each other through a literature survey and data from a four-year carbon (C) farming experiment. The thesis also investigates whether meas-uring the fast-cycling N pools and including them in fertilisation recommendation calculations results in financial savings from N fertiliser cuts. Twenty different Finnish farms were investigated, split between six C farming practices: subsoil-ing, undersown cover crops, ley farming, soil organic amendments, planned grazing, diverse grasses lay. Soil samples were collected at two different depths (0-17 and 17-30 cm) and ana-lysed for total N and C (Total N, Total C), mineral N, Illinois Soil N Test (ISNT N), autoclave citrate extractable protein N (ACE-Protein N), water extractable organic N and C (WSON and WSOC), and microbial activity derived N (PMN) from CO2 burst after rewetting of dry soil (Resp C).The analysis recovered on average 25% of total N, while 75% remained in the non-recovered pool. Clay%, C% and C:Clay explained the variation in Total N (r2=0.90), ISNT N (r2=0.90), pro-tein N (r2=0.93) and the non-recovered N (r2=0.83), but it did not for WSON (r2=0.50), PMN (r2=0.21) and inorganic N (r2=0.20). Four-year C farming management did not result in statisti-cally significant differences in the N pools, even though PMN and WSON were 19% and 11.6% higher in treatment than in control, respectively. The variation was high for both (SD=48 and 42), explaining the non-significance. Strong correlations (Spearman rho, ρ) were observed between Total N - ISNT N, Residual N, and WSON, indicating their predictive capability for total N, while protein N showed weaker correlations. PMN correlated strongly with bacterial respiration C (ρ = 0.94) and WSON (ρ = 0.75) and had a negative strong correlation with the WSOC:WSON ratio (ρ = -0.73). In conclusion, soil's non-recovered N fraction, likely associated with the mineral surfaces and undecomposed particulate organic matter (POM), is the largest portion of total N. Clay%, C% and C:Clay explains the variation in the slow-cycling N pools but not in the fast-cycling ones. The quality of soil organic matter (SOM) is better assessed using WSON, PMN, and the WSOC:WSON ratio. Utilising PMN as a predictor of N release from SOM results in lower N ferti-liser recommendations, leading to cost savings for farmers. This research shows that four years of C farming do not increase the N stock in soil. Further research is needed to determine if C farming practices in a long-term experiment would increase the soil N stocks, significantly affect soil N pool relationships and result in financial savings for farmers.
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(2023)Phosphorus is one of the three main nutrients for plants and sufficient phosphorus uptake is a prerequisite for crop production. Phosphorus exists in organic and inorganic forms in soil, and the stability and biological availability of different forms of phosphorus vary. Fertilizer phosphorus is efficiently adsorbed by aluminium and iron oxides in mineral soils, and due to positive phosphorus balances in the last decades, cultivated soils contain residual phosphorus. In addition to topsoil, phosphorus can accumulate in soil layers below the plough layer. Knowing the size of the phosphorus reserves in soil profile and the proportions of different forms of phosphorus could provide a more reliable assessment of the possibilities for utilizing and considering phosphorus reserves for example in fertilization. The aim of this study was to investigate the distribution and stocks of different forms of phosphorus in depth profiles of conventionally and organically managed clay soil and in unmanaged natural grassland. In a field experiment that has lasted 24 years before the sampling, conventional plots were fertilized with inorganic fertilizers, and organically managed plots with organic fertilizers. Total phosphorus, organic phosphorus, and water-extractable phosphate phosphorus were determined in 10 cm layers to an average depth of 70 cm. The stocks of soil total carbon and nitrogen were also determined. Changes in the carbon-to-phosphorus (C:P) and carbon-to-nitrogen (C:N) ratios of soil can affect the mineralization of soil organic matter and thus the release of nutrients for use by organisms. In addition, oxalate-extractable aluminium and iron, representing the concentrations of aluminium and iron oxides, were determined from the samples. Stocks were calculated using the equivalent soil mass (ESM) method, which quantifies stocks in terms of soil mass layers rather than depth layers. The differences in the concentrations and total stocks of the investigated forms of phosphorus between management systems were found to be relatively small. The slight differences in total stocks may indicate that phosphorus fertilization in the cultivated plots has corresponded well with the amount of phosphorus taken up by the crops. However, both conventional and organic plots also showed indications that phosphorus had accumulated in organic form below the plough layer. The use of organic fertilizers on the organically managed plots appeared to maintain the organic carbon content at deeper soil depths, as the carbon concentration of the organically managed plots and the unmanaged grassland with the highest carbon total stock did not differ statistically significantly at depths of 20–30 cm and below 40 cm. In all management systems, approximately one-third of the total phosphorus stock was in organic form. Based on the carbon-to-organic-phosphorus ratios (C:Porg), the soil organic matter in the cultivated plots contained more phosphorus than the unmanaged grassland, which may indicate that more phosphorus net mineralization occurs in the cultivated plots than in the unmanaged grassland.
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(2021)The use of fertilizers has made it possible to increase agricultural yields, enabling the world’s growing population to be fed. The use of mined phosphorus has created mostly linear phosphorus flow from mines through farms to lakes and oceans. This has clearly deteriorated aquatic ecosystems globally. USA, China and Morocco control over 85 % of global phosphorus reserves and Europe is very dependent on imported phosphorus. To gain phosphorus balance in Europe, it would be important to recycle phosphorus. Recycled fertilizers come from derived currents of agriculture, food industry, forest industry and communities. Only a few studies have been made regarding the effects different recycled fertilizers have on plant’s phosphorus uptake. The aim of this study was to find out how four different recycled fertilizer treatments (ammonium sulphate, liquid digestate, meat bone meal, vinasse) affect barley’s phosphorus uptake and soil aggregate stability, when compared to mineral fertilizer treatment and non-fertilized control treatment. Study material was collected from HYKERRYS 2 -project’s experiment field in growing season 2019. Phosphorus in dry matter was measured and biomass, phosphorus uptake to biomass, fertilizer use efficiency and phosphorus uptake from soil phosphorus reserves were calculated from barley plant samples collected at growth stage 65 (BBCH). Soil aggregate stability analyses, dry sieving and wet sieving, were made to soil samples collected after harvest. Barley’s phosphorus content in dry matter was highest with non-fertilized treatment but other treatments had no differences between them. In biomass quantity or phosphorus uptake on biomass there were no differences between treatments. Fertilizer use was most efficient with ammonium sulphate and least efficient with digestate. Phosphorus uptake from soil phosphorus reserves was least efficient with digestate and mineral fertilizer. The share of soil water stable aggregates had no differences between treatments, but water turbidity was lowest with ammonium sulphate. The results show that recycled fertilizers are fit to replace mineral fertilizers when considering plant’s phosphorus uptake, because there were no notable differences in barley’s phosphorus content, biomass, phosphorus uptake on biomass or soil aggregate stability between different recycled fertilizers and mineral fertilizer. When viewing the results, it should be considered that the soil in experimental field had high phosphorus content and high soil organic matter content to begin with, which made it more difficult to detect the differences than it probably would have been if the soil phosphorus content had been lower. There was also no information available about the forms of the phosphorus in the recycled fertilizers, which made the interpretation of the results difficult, because different forms of phosphorus are differently available for plants. In order to target the use of recycled fertilizers effectively based on crop and soil quality, more knowledge is needed on both the phosphorus forms in recycled fertilizers and recycled fertilizer’s effects on plant’s phosphorus uptake on soils with lower nutrient and organic matter contents.
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(2023)The average global surface temperature has risen 1.1 degrees from pre-industrial times, mainly due to anthropogenic greenhouse gas (GHG) emissions. Nitrous oxide (N2O) is a strong and ozone-depleting greenhouse gas. It has 265 times stronger Global Warming Potential than carbon dioxide (CO2) and an atmospheric lifetime of 120 years. Over half of the global N2O emissions originate from agriculture, mainly from cultivated soils. In soils, facultative microbial-driven denitrification and chemoautotrophy- or heterotrophy-driven nitrification are the dominant N2O -producing processes. These processes are driven by soil properties and environmental variables. In northern agricultural soils, over half of the annual N2O emissions are estimated to be produced outside the growing season, mostly during soil freeze-thaw cycles (FTCs). However, due to lack of seasonal measurements the emissions outside growing season are still poorly understood. The aim of this study was to investigate how soil FTCs affect N2O emission dynamics from Finnish grassland soils, and whether different soil types (fine sand, peat soil, clay loam) affect N2O emissions and nitrogen dynamics during soil freezing and thawing. The study was conducted as a laboratory incubation experiment using a newly built automated measuring system. N2O emissions from undisturbed soil samples were measured continuously for 21 days, which included total of 7 freeze-thaw cycles from -5°c to +5°C. N2O production or consumption was calculated for each freeze-thaw cycle, and soil mineral nitrogen (min N), C:N ratio, C%, N%, and pH(H2O) were determined during each cycle from separate undisturbed soil samples. Also, net ammonification, net nitrification and total net mineralisation rates were calculated from the min N concentrations for each FTC. Each soil type emitted N2O during the thawing of the soil, while frozen soils appeared to act as a small N2O sink. Contradictory to other studies, steady N2O production was seen throughout the seven FTCs and there was no significant increase or decrease in N2O emissions as the FTCs proceeded. Peat soils produced 4-10 times more N2O than fine sand and clay loam, respectively. Peat soil was also the largest sink of N2O during freezing. N2O emissions did not correlate with soil chemical properties, with few exceptions during soil thawing: C:N ratio (positive correlation) and pH (negative correlation). This is probably due to the episodic nature of N2O, and the complex and overlapping processes driving N2O production and consumption. FTCs increased NH4+ concentration especially in fine sand and peat soil while NO3- concentration decreased in all soils except in clay soil. Based on these results, denitrification was suggested as the main N2O producing process in peat soil and in fine sand. High NH4+ and low NO3- concentration in peat soil and fine sand indicate fast mineralisation and rapid denitrification during thawing or low nitrification and dissimilatory nitrate reduction (DNRA) activities, both of which may also have limited N2O emissions. This study shows that organic grassland soils have a high potential to both produce and consume N2O compared to other soil types during FTCs. The capacity to produce N2O during consequent FTCs indicates that these soils have a persistent and long-lasting capacity to produce N2O in freeze-thaw conditions. The N2O emission dynamics most likely reflect rapid changes in soil nitrogen turnover processes, which calls for further studies and method development to link the gross N turnover rates to N2O production and consumption during soil freezing and thawing.
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(2021)Tämän työn tarkoituksena oli tutkia kuinka eri lannoituksen muodot ja määrät vaikuttavat nurmiviljelyyn käytettävän maaperän typpi (N)- ja hiili (C)-pitoisuuksiin. Pyrkimyksenä oli löytää tilastollisia eroavaisuuksia orgaanisen ja epäorgaanisen lannoituksien vaikutuksista nurmialueen kasvihuonekaasupäästöihin. Kasvillisuuden, maahengityksen ja yhteyttämisen mittaukset suoritettiin neljälle eri käsittelylle (lannoittamaton, epäorgaaninen 30 kg N/ha, epäorgaaninen 60 kg N/ha ja orgaaninen 60 kg N/ha). Maaperästä otetiin näytteet analyysiä varten kasvukauden jälkeen syvyyksiltä 0–10 cm ja 20–30 cm. Maaperänäytteille suoritettiin mineraalityppi-määritys sekä kokonais- hiilen ja – typen määritykset. Kasvillisuudesta mitattiin maanalainen ja maanpäällinen biomassa sekä lehtipinta-ala indeksi eli LAI. Maahengitys ja yhteyttäminen mitattiin suljetuilla kammiomenetelmillä. Mittauksissa saatu CO2-pitoisuuden muutos sijoitettiin lineaariseen yhtälöön, josta muodostettiin hiilidioksidin vuo. Maahengityksen ja yhteyttämisen tuloksista mallinnettiin vielä koko kasvukauden hiilitaseet. Kasvillisuuden mittauksissa suurimmat biomassat esiintyivät läpi mittauskauden korkeimman lannoitustason saaneilla epäorgaanisella (700–800 g/m2) ja orgaanisella (700–1000 g/m2) käsittelyillä. Yhteyttämispotentiaalin sekä maahengityksen tuloksissa eroja oli ainoastaan lannoittamattomien ja lannoituksen saaneiden käsittelyiden välillä. Hiilitaseiden mallinnuksessa selvisi, että kokeen kaikki käsittelyt toimivat hiilenlähteinä ja vähiten hiiltä vapautui epäorgaaniselta 30 kg N/ha saaneelta lannoitukselta. Maaperäanalyyseissä käsittelyiden C- ja N- pitoisuuksissa ei ollut eroavaisuuksia. Mineraalitypen määrityksissä pohjamaiden NO3- ja NH4- pitoisuuksissa oli tilastollisia eroavaisuuksia orgaanisen ja epäorgaanisen käsittelyiden välillä. Orgaanisella lannoituksella pintamaan sekä pohjamaan NO3-pitoisuudet ovat lähellä toisiaan, kun taas epäorgaanisella lannoituksella pohjamaan pitoisuudet ovat selkeästi korkeammat. Tuloksien perusteella ei pystytä selkeästi sanomaan, kumpi lannoitemuodoista olisi hiilen sitoutumisen kannalta parempi vaihtoehto. Tutkimuksen aihealue on kuitenkin merkittävä ilmaston sekä viljelijöiden kannalta. Tästä syystä jatkotutkimuksien tekeminen olisikin suotavaa, jotta nurmiviljelystä pystytään muokkaamaan hiiltä sitovaksi ja samalla parantamaan peltojen kasvukuntoa.
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(2022)Declining trend of carbon content in croplands has been reported in Finland as well as globally and at the same time soil degradation has risen to a significant threat for food production. Increasing soil carbon content for example with carbon rich fertilizers may improve soil water retention properties, soil structure, and increase soil carbon sink. The aim of this thesis was to study if the usage of carbon-rich fertilizers (pulp mill sludge, liquid vinasse, bone meal and biowaste compost with biochar) increase soil carbon content, soil water retention and water stable aggregates compared to usage of inorganic fertilizers or unfertilized control in a four-year time period (2016-2019). Material for water retention curve and water stable aggregate measurements was collected in HYKERRYS-project field experiment after harvest in august 2019. Existing data were utilized for determination of soil total carbon content, which had been collected every year after harvest in the topsoil (0-20 cm). The total carbon content was determined with Variomax CN-analyser in 2016-2018 and with LECO CN-analyzer in 2019. Water retention curve was determined by underpressure method in sandbox (for pF 1,5, 1,8 and 2,0) and overpressure method in pressure plate extractor (for pF 2,7, 3,4 ja 4,2) using undisturbed and disturbed (pF 4,2) soil samples collected in topsoil. Water-stability of aggregates was determined with wet sieving method for aggregate size fraction 2-5 mm. Before wet sieving, samples were dry sieved on fraction classes > 5 mm, 2-5 mm and < 2 mm. Soil carbon content (soil C) in the composted pulp mill sludge treatment was by +0,5 % statistically significant (p < 0,05) higher than that in the mineral fertilizer treatment in 2019. Statistically significant regression between added C and measured soil C content supported the view that added C increased soil C contents also in other treatments even if no significant differences between these treatments were detected. None of the treatments significantly improved the water retention or water stable aggregates (p > 0,05). The results of this thesis indicated that adding composted pulp mill sludge over 22 000 kg DM ha 1 (8000 kg C ha-1) in four years is enough to significantly raise the carbon content of a humic clay loam soil, but it is not enough to improve soil water retention properties or the water stability of soil aggregates.
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