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Soil management is known to have significant effects on soil structure. Especially, grassland renovation and associated ploughing may have destructive influence on structure, but on the other hand conversion of arable land to grassland can improve pore structure and soil functions. In crop rotations including perennial grasses, soil structure is affected by these counteracting processes. The purpose of this work was to study and quantify the impacts of varying soil management practices on the structure of boreal arable heavy clay soils. We studied intact topsoil samples collected from two sites by X-ray computed microtomography, image analysis, image-based pore-scale flow simulations, and water retention measurements. At both sites, one area under long-term (at least 30-year-old) grassland was compared with adjacent field area with contrasting managements:Site 1: Cereal production under no-till management for 13 years prior to sampling. Site 2: Crop rotation of a livestock farm with cereals and perennial grasses, tillage by ploughing. At the sampling time this field area had been two years under grass after preceding 3-year cereal period. Both imaging and water retention showed statistically and practically significant differences in the soil macropore structure at site 1 such that porosity of the long-term grassland was clearly higher that that under cereal production. On the contrary, at site 2, only minor differences between managements were observed. Our results show that the soil management practices affect the macropore structure of boreal arable clay soil and that no-till and crop-rotation managements had clearly different effects on soil structure as compared to long-term grasslands.

Viimeaikaiset tulokset massa- ja paperiteollisuuden sivuvirroista ja tehtaan jätevesien puhdistusprosesseista syntyvien kuitulietteiden käytöstä maanparannusaineina hienojakoisilla viljelymailla ovat olleet lupaavia. Kuitulietteiden sato-, hiilisyöte- ja maanparannusvaikutusten selvittämiseksi karkeilla kivennäismailla (KHt) perustettiin Biosfääri-hankkeessa (Biosfääri Pohjois-Savo; Biomassan ja biojalostusteknologioiden hyödyntäminen liiketoiminnan kasvattamisessa) Luke Maaningalle kaksivuotinen, lohkoittain satunnaistettu ja neljänä kerranteena toteutettu kenttäkoe. Timotei-nurminatanurmi perustettiin kesäkuussa 2020 suojaviljan alle. Ennen kylvöä kuitulietteet levitettiin maan pintaan (21–28 tuore-t ha-1, liukoinen-N n. 15 kg ha-1, kokonais-P n. 26 kg ha-1) ja äestettiin noin 7 cm:n syvyyteen. Toinen metsäteollisuuden kuitulietteistä oli tyyppinimeltään kalkkistabiloitu puhdistamoliete (kalkkikuitu Kuopio; Fortum Waste Solution Oy; jatkossa maanparannuskuitu A), kun taas toinen oli hygienisoimaton ja tuotteistamaton (Stora Enso Oyj, Varkaus; jatkossa maanparannuskuitu B). Kuitulietteistä otetuissa näytteissä ei todettu salmonellabakteereita ja Escherichia coli -pitoisuudet (

To achieve appropriate yield levels, inherent nitrogen (N) supply and biological N fixation are often complemented by fertilization. To avoid economic losses and negative environmental impacts due to over-application of N fertilizer, estimation of the inherent N supply is critical. We aimed to identify the roles of soil texture and organic matter in N mineralization and yield levels attained in cereal cultivation with or without N fertilization in boreal mineral soils. First, the net N mineralization and soil respiration were measured by laboratory incubation with soil samples varying in clay and organic carbon (C) contents. Secondly, to estimate the inherent soil N supply under field conditions, both unfertilized and fertilized cereal yields were measured in fields on clay soils (clay 30-78%) and coarse-textured soils (clay 0-28%). In clay soils (C 2.5-9.0%), both the net N mineralization and the cereal yields (without and with fertilization) decreased with increasing clay/C ratio. Moreover, in soils with high clay/C ratio, the agronomic N use efficiency (additional yield per kg of fertilizer N) varied considerably, indicating the presence of growth limitations other than N. In coarse-textured soils, the yield increase attained by fertilization increased with increasing organic C. Our results indicate that for clay soils in a cool and humid climate, the higher the clay content, the more organic C is needed to produce reasonable yields and to ensure efficient use of added nutrients without high N losses to the environment. For coarse soils having a rather high mean organic C of 2.3%, the organic C appeared to improve agronomic N use efficiency. For farmers, simple indicators such as the clay/C ratio or the use of non-N-fertilized control plots may be useful for site-specific adjustment of the rates of N fertilization. Highlights We aimed to identify simple indicators of inherent soil N supply applicable at the farm level. In clay soils, the net N mineralization was found to correlate negatively with the clay/C ratio. In coarse-textured soils, agronomic N use efficiency improved with increasing soil organic C. Clay soils with high clay/C ratio are at risk of low yield levels.

Short-term agronomic and environmental benefits are fundamental factors in encouraging farmers to use biochar on a broad scale. The short-term impacts of forest residue biochar (BC) on the productivity and carbon (C) storage of arable boreal clay soil were studied in a field experiment. In addition, rain simulations and aggregate stability tests were carried out to investigate the potential of BC to reduce nutrient export to surface waters. A BC addition of 30 t ha−1 increased soil test phosphorus and decreased bulk density in the surface soil but did not significantly change pH or water retention properties, and most importantly, did not increase the yield. There were no changes in the bacterial or fungal communities, or biomasses. Soil basal respiration was higher in BC-amended plots in the spring, but no differences in respiration rates were detected in the fall two years after the application. Rain simulation experiments did not support the use of BC in reducing erosion or the export of nutrients from the field. Of the C added, on average 80% was discovered in the 0–45 cm soil layer one year after the application. Amendment of boreal clay soil with a high rate of BC characterized by a moderately alkaline pH, low surface functionalities, and a recalcitrant nature, did not induce such positive impacts that would unambiguously motivate farmers to invest in BC. BC use seems unviable from the farmer's perspective but could play a role in climate change mitigation, as it will likely serve as long-term C storage. publishedVersion

Production of organic fertilizers from poultry manure may compromise availability of phosphorus (P) to plants. This study examined the effects of granulation, feather meal addition, and pyrolysis on bioavailability of P in broiler manure in a pot experiment with ryegrass and assessed whether P availability is enhanced by inoculating arbuscular mycorrhizal fungi (AMF) into soil. Granulated broiler manure gave similar plant yield and P uptake to superphosphate. Feather meal addition had a minor negative effect on P availability, whereas pyrolysis lowered the fertilization effect of broiler manure. The yield-based mineral-P equivalences were 120%, 85% and 75% during the first harvest, and 100%, 75% and 45% during one growing season for granulated unamended, granulated amended with feather meal and pyrolyzed broiler manure. Soil inoculation with AMF did not enhance P availability. Granulated poultry manure is suitable as a P fertilizer for annual crops with comparable bioavailability to mineral fertilizer P, whereas pyrolyzed poultry manure is suitable as a slow-release or storage P fertilizer in slightly acidic soils. Knowledge on P bioavailability in organic fertilizers produced with different technologies can be used for optimizing fertilization, minimizing build-up of soil P and its adverse environmental effects. (C) 2021 The Author(s). Published by Elsevier B.V.

Erosion and colloidal particle loss from cultivated clay soils in cool humid climate pose a risk to soil productivity and surface water quality. To enhance soil management practices that effectively reduce clay soil erosion, we need to understand the interrelations between the key variables on which clay soil aggregate structure depend. The objective of our study was to quantify the relative importance of OC content, land use and soil wetness, for the aggregate stability of post-glacial clay soils. We estimated the potential effect of five different land uses (cereal cropping with variable tillage and crop rotation, permanent grassland and forest as a control) on clay soil aggregate stability as measured by the percentage of water-stable aggregates (WSA% of 2–5 mm fraction) and colloid detachment (turbidity, NTU%), after controlling for the differences in organic carbon content (OC%) and Clay%/OC% ratio between the land uses through covariance analysis. Further, we assessed how aggregate structure in differently managed soils with different OC% tolerates the varying moisture conditions. The higher OC% was reflected in all cultivated soils by increased aggregate stability, implying that OC inputs may positively affect soil structure even in low additions. When compared at equal OC%, the mean WSA% was lower in cereal cropping than in soils under forest or permanent grass, clearly showing the negative effect of tillage frequency on the aggregate stability. The detachment of colloidal particles from aggregates was higher in soils with a high Clay%/OC% ratio, and thus the Clay%/OC% ratio may offer an easily measurable indicator for the risk of clay dispersion, and thereby soil erosion and the export of particle-bound nutrients from cultivated fields. When compared at an equal Clay%/OC% ratio, colloid detachment from aggregates representing cereal fields was two- to threefold as compared to permanent grassland. Cultivated soils with less than 4–6% OC were very sensitive to waterlogging, highlighting the role of proper drainage in erosion control. The results demonstrate that an increase in OC content and proper drainage would help to improve the aggregate stability of cultivated clay soils in cool humid climate, but the effective improvement of the present situation would require drastically reduced soil disturbances for areas with the highest erosion risk.

We studied the effects of catchment characteristics (soil type and land use) on the concentration and quality of dissolved organic matter (DOM) in river water and on the bacterial degradation of terrestrial DOM. The share of organic soil was the strongest predictor of high concentrations of dissolved organic carbon, nitrogen, and phosphorus (DOC, DON, and DOP, respectively), and was linked to DOM quality. Soil type was more important than land use in determining the concentration and quality of riverine DOM. On average, 5-9 % of the DOC and 45 % of the DON were degraded by the bacterial communities within 2-3 months. Simultaneously, the proportion of humic-like compounds in the DOM pool increased. Bioavailable DON accounted for approximately one-third of the total bioavailable dissolved nitrogen, and thus, terrestrial DON can markedly contribute to the coastal plankton dynamics and support the heterotrophic food web.

Several factors highlight the importance of dissolved organic matter (DOM) in coastal ecosystems such as the Baltic Sea: 1) DOM is the main energy source for heterotrophic bacteria in surface waters, thus contributing to the productivity and trophic state of bodies of water. 2) DOM functions as a nutrient source: in the Baltic Sea, more than one-fourth of the bioavailable nutrients can occur in the dissolved organic form in riverine inputs and in surface water during summer. Thus, DOM also supports primary production, both directly (osmotrophy) and indirectly (via remineralization). 3) Flocculation and subsequent deposition of terrestrial DOM within river estuaries may contribute to production and oxygen consumption in coastal sediments. 4) Chromophoric DOM, which is one of the major absorbers of light entering the Baltic Sea, contributes highly to water color, thus affecting the photosynthetic depth as well as recreational value of the Baltic Sea. Despite its large-scale importance to the Baltic Sea ecosystem, DOM has been of minor interest compared with inorganic nutrient loadings. Information on the concentrations and dynamics of DOM in the Baltic Sea has accumulated since the late 1990s, but it is still sporadic. This review provides a coherent view of the current understanding of DOM dynamics in the Baltic Sea.

Dissolved organic carbon (DOC) load in discharges from cultivated soils may have negative impacts on surface waters. The magnitude of the load may vary according to soil properties or agricultural management practices. This study quantifies the DOC load of cultivated mineral soils and investigates whether the load is affected by agricultural practices. Discharge volumes and concentrations of DOC and dissolved organic nitrogen (DON) were continually measured at three sites from surface runoff and artificial subsurface drainage or from combined total discharge over a two-year period (2012-2014). Two experimental sites in South-West Finland had clayey soils (with soil carbon contents of 2.7-5.9% in the topmost soil layer), and the third site in West-Central Finland had sandy soil (soil carbon contents of 4.3-6.2%). Permanent grassland, organic manure application, mineral fertilization, and conventional ploughing or no-till activities were studied. Furthermore, the biodegradable DOC pool of surface runoff and subsurface drainage water from no-till and ploughed fields was estimated in a 2-month incubation experiment with natural bacterial communities collected from the Baltic Sea seawater. The annual DOC and DON loads were affected by discharge volume and seasonal weather conditions. The loads varied between 25-52 kg ha(-1) and 0.8-3.2 kg ha(-1), respectively, and were comparable to those from boreal forests with similar soil types. The DOC load increased with increasing topsoil carbon content at all sites. There were slightly higher DOC concentrations and DOC load from permanent grassland, but otherwise we could not distinguish any clear management-induced differences in the total DOC loads. While only 6-17% of the DOC in discharge water was biologically degraded during the 2-month incubation, the proportion of biodegradable (labile) DOC in surface runoff appeared to increase when soil was ploughed compared to no-till. (c) 2017 Elsevier B.V. All rights reserved.

Soil structure is one of the key properties affecting the productivity of soils and the environmental side effects of agricultural soils. Poor surface soil structure increases the risk of soil erosion by water and eroded clay-sized particles can carry adsorbed phosphorus (P) to the surface waters, thus inducing eutrophication of receiving waterways. Management practices, e.g. reduced tillage, used to reduce erosion can lead to enrichment of P in the uppermost soil layers, which leads to elevated risk for dissolved P loss in the runoff water. In this study, we aimed to identify whether biochar (BC) could be used to reduce clay soil erosion by improving aggregate stability. Moreover, we tested whether the BC addition would change the P sorption affinity of the soil and help to reduce the loss of dissolved P. One sandy and two clayey soils were amended with BC (0, 15 and 30 t ha − 1 ) and after a 3-week incubation, a wet-sieving method was used to measure the release of colloidal particles and the stability of aggregates. The sorption of P onto soil surfaces was estimated with a Q/I (quantity/intensity) plot technique. The BC used here had a very low P sorption affinity and the BC addition did not increase the sorption of P in incubated soils. However, for the two clayey soils, the BC additions increased aggregate stability and reduced detachment of colloidal material. The BC thus induced changes in soil properties that could be beneficial for erosion control and thereby aid in reducing particulate P losses from agricultural fields.

Despite the publication of a number of papers dealing with the effect of drying on the soil labile P pool, less attention has been paid to the possible drying-evoked changes in the more stable P pools. We applied Hedley's sequential fractionation procedure that aims at quantifying soil P reserves according to their decreasing plant availability to examine the effects of drying on soil P fractions in clayey soil samples of different cultivation history. To further investigate the contribution of organic matter disruption to the solubility of soil P, the P extracted in each fractionation step was divided into two size classes by filtering the suspension through a 0.2 μm membrane filter. There were no air-drying-induced changes in the total amount of P extracted in each fractionation step. However, air-drying changed the distribution of water-extractable P in size fractions ; increase in the small-sized P took place at the expense of large-sized P. Air-drying increased also small-sized molybdate-unreactive P (MUP) in the NaOH fraction giving evidence that drying-induced alterations take place also in less labile P forms. The results revealed that air-drying alters the extractability and distribution of P in various pools rather than the total amount of extracted P and that a large proportion of H 2 O- and NaOH-extractable large-sized MUP may remain undetected if only filtered samples are analyzed.

The potential effects of freezing on phosphorus (P) chemistry in Finnish soils are not well known. We studied the effects of multiple freeze-thaw cycles on soil P chemistry in a laboratory incubation experiment with one organic and one mineral surface soil. The soils were incubated at +5°C or at alternating +5/–20°C temperatures for 24 weeks, either without amendment or amended with pig slurry or with commercial compound fertilizer (NPK 20–3–9). After incubation, the soils were analyzed for water-soluble reactive and unreactive P, and acid ammonium acetate soluble P (PAAA). Freezing and thawing of soils during the incubation had no significant effect on any of the water-soluble P fractions or PAAA. The outcome was most likely a consequence of the good P status of the soils, which masked the gentle effects of freezing. According to these results, the time of soil sampling (fall vs. spring) has no effect on P test results on soils with a good P status. Concentrations of soluble P after incubation were roughly twice as high in the slurry treatments than in the fertilizer treatments, demonstrating potentially better long-term availability of slurry P., Pohjoismaissa maat jäätyvät lähes säännöllisesti, muttajäätymisen vaikutuksia maan kemiallisiin ominaisuuksiin on tutkittu melko vähän. Tässä työssä selvitettiin toistuvien jäätymis-sulamissyklien vaikutuksia fosforin (P) käyttäytymiseen multamaalla ja multavalla hiuemaalla. Maiden viljelyhistoria oli käytännössä identtinen ja P-tila hyvä. Tulosten perusteella pyrittiin arvioimaan mm. maanäytteen ottoajankohdan vaikutusta viljavuusanalyysin P-lukuun ja maan jäätymisen vaikutusta syysviljojen fosforilannoituksen tehoon. Maihin lisättiin sian lietelantaa tai NPK-lannoitetta (20–3–9), ja niitä muhitettiin tasaisessa + 5 °C lämpötilassa tai kahden viikon jaksoissa +5 °C ja –20 °C lämpötiloissa yhteensä 24 viikkoa. Molemmissa käsittelyissä oli mukana myös kontrollikoejäsenet, joihin ei lisätty fosforia. Käsittelyjen jälkeen maista analysoitiin vesiliukoisen reaktiivisen ja ei-reaktiivisen fosforin pitoisuus sekä viljavuusfosfori. Muhituksen jälkeen NPK-lannoitetta saaneiden maiden vesiuuttoisen reaktiivisen P:n pitoisuudet eivät poikenneet merkittävästi lannoittamattomista kontrollikoejäsenistä. Sian lietelantaa saaneissa maissa pitoisuudet olivat sen sijaan selvästi suurempia kuin kontrollissa, vaikka niissäkin suurin osa lisätystä P:sta oli pidättynyt maahan. Tuloksen perusteella lannan P on muhitusolosuhteissa pitempivaikutteista kuin NPK-lannoitteen P ja siksi sopivaa esim. syysviljojen lannoitukseen. Tulokseen vaikuttaa osaltaan myös se, että ohjeen mukaan lannan fosforista lasketaan kasveille käyttökelpoiseksi vain 75 %, ja siksi lannassa saa levittää enemmän fosforia kuin NPK-lannoitteessa. Jäätymisellä ei ollut juurikaan vaikutusta maista muhituksen jälkeen tehtyjen fosforianalyysien tuloksiin, vaikka toistuva jäätyminen ja sulaminen hieman näyttikin kasvattavan vesiliukoisen reaktiivisen P:n pitoisuutta. Näytteenottoajankohdalla ei siten näyttäisi olevan vaikutusta maasta tehtävien P-analyysien tuloksiin. Muualla tehdyissä tutkimuksissa talvella tapahtuvan jäätymisen on usein todettu kasvattavan tuloksia loppukesällä otettuihin näytteisiin verrattuna. Tässä kokeessa saatuihin tuloksiin vaikutti todennäköisesti pitkä muhitusaika, jonka kuluessa jäätymisen mahdollisesti vapauttama fosfori ehti pidättyä maahan, sekä koemaiden hyvä P-tila. Tällaisilla mailla jäätymisen vaikutukset ovat aiemmissakin tutkimuksissa olleet pieniä.

The objective of this study was to examine the effects of urine and dung additions on the phosphorus (P) chemistry of pasture land and to compare the sensitivity of two soil extraction methods in assessing the P-loading risk. In a field experiment, urine and dung were added to soil in amounts corresponding to single excrement portions and the soil samples, taken at certain intervals, were analysed for pHH2O, acid ammonium acetate extractable P (PAc) and water extractable total P (TPw), and molybdate reactive P (MRPw). Urine additions immediately increased soil pH and MRPw, but no such response was observed in PAc extraction due to the low pH (4.65) of the extractant enhancing the resorption of P. The PAc responded to the dunginduced increase in soil total P similarly as did Pw, which suggests that both tests can serve to detect areas of high P concentration. However, water extraction was a more sensitive method for estimating short-term changes in P solubility. In pasture soils, the risk of P loss increases as a result of the interaction of urination and high P concentration in the topsoil resulting from continuous dung excretion., Maan fysikaalisten ja kemiallisten olosuhteiden muutoksetsekä muutokset maan fosforitilassa voivat edistää fosforin (P) huuhtoutumista maasta ja sitä kautta myös vesistöjen rehevöitymistä. Tutkimuksen tarkoituksena oli selvittää sonta- ja virtsalisäysten vaikutusta laidunmaan fosforitilaan sekä verrata kahden uuttotestin, vesiuuton ja happaman ammoniumasetaattiuuton, herkkyyttä muutosten seurannassa. Aineisto kerättiin MTT:n Maaningan tutkimusasemalla sijainneesta kenttäkokeesta. Sontaa ja virtsaa levitettiin koeruuduille keskimääräistä kertaeritystä vastaavat määrät ja koeruuduista (virtsa, sonta ja kontrolli) otettiin 0–2 cm ja 2–10 cm syvyyksiltä maanäytteet tietyin aikavälein. Maanäytteistä määritettiin pHH2O, vesiliukoinen kokonaisfosfori (TPw) ja epäorgaaninen fosfori (MRPw) sekä viljavuusanalyysin fosfori (PAc), jota Suomessa käytetään fosforilannoitustarpeen ennustamiseen. Eri käsittelyjen vaikutukset olivat pääasiassa havaittavissa vain maan pintakerroksessa (0–2 cm). Virtsa nosti maan pH:ta välittömästi lisäyksen jälkeen ja MRPw:n pitoisuudet seurailivat kiinteästi pH:n muutoksia maassa. Vastaavaa nousua ei juurikaan ollut havaittavissa PAc:n pitoisuudessa. Tämä johtuu viljavuusuuttoliuoksen (hapan ammoniumasetaatti) alhaisesta pH:sta (4,65), joka edistää fosforin pidättymistä maahan. Molemmat testit reagoivat samalla tavoin sontalisäyksen aiheuttamaan maan kokonaisfosforipitoisuuden kasvuun. Tulosten mukaan vesiuutto on viljavuusanalyysin uuttoa herkempi menetelmä tarkasteltaessa lyhyen ajan muutoksia maan helppoliukoisen fosforin pitoisuuksissa. Laidunmailla virtsan aiheuttama pH:n nousu lisää liukoisen fosforin määrää, mikä yhdessä sontalisäysten aiheuttaman pintamaan fosforipitoisuuden nousun kanssa kasvattaa fosforin huuhtoutumisriskiä.