Long-term effects of liming on crop yield, plant diseases, soil structure and risk of phosphorus leaching

This study examined the long-term effects of applying structure lime (mixture of similar to 80% CaCO3 and 20% Ca(OH)(2)) and ground limestone (CaCO3) on soil aggregate stability and risk of phosphorus (P) losses 5-7 years after liming, incidence of soil-borne diseases and yield in winter wheat (Tritium aestivum), oilseed rape (Brassica napus) and sugar beet (Beta vulgaris). Lime was applied in 13 field trials in Sweden 2013-2015 and soil characteristics and crop yield were monitored until 2021. Seedbed (0-4 cm depth) aggregate (2-5 mm size) stability was improved to the same extent with both lime treatments compared to the untreated control, sampled 5-7 years after liming. Analyses and estimations of different P fractions (total P, PO4-P and particulate P) in leachate following simulated rainfall events on undisturbed topsoil cores sampled 6-8 years after liming revealed lower total P and particulate P concentrations in both lime treatments compared to the untreated control. Two sugar beet trial sites with soil pH 7.2 but yield of oilseed rape decreased after application of structure lime

Timing and conditions modify the effect of structure liming on clay soil

Two dates (early, normal) for application and incorporation of structure lime to clay soil were examined at four field sites, to test whether early liming had more favourable effects on aggregate stability. Aggregate size distribution measurements revealed a finer tilth at the early liming date (20 August) than the normal date (14 September). Aggregate stability estimated one year later, using as a proxy turbidity in leachate from 2–5 mm aggregates subjected to two simulated rainfall events, was significantly improved (11% lower turbidity) with early compared with normal liming date. Three years after structure liming, soil structural stability measurements on lysimeters (15 cm high, inner diameter 18 cm) subjected to repeated simulated rainfall events showed no significant differences in turbidity in leachate between the early and normal liming dates. However, there was a strong interaction between liming date and site indicating different reactions at different sites. Our results suggest that early spreading and incorporation can improve the success of structure liming, but only if soil conditions are favourable

CO2 emissions from cultivated peat soil with sand addition, a CAOS project

Peatlands store a major share of the world’s soil organic carbon and are widespread in Northern and Central European countries. Drainage is a precondition for classical agricultural production on organic soils. Drainage fosters peat mineralization and changes the physical and chemical soil quality. Only few decades after initial drainage, agricultural systems on drained organic soils start experiencing a high risk of crop failure. Decreased hydraulic conductivities lead to decreased infiltration, ponding, and finally to abandonment as drainage will not be effective anymore. One of the problems of (wet) organic soils is the low trafficability. The aim in this experiment is to investigate if the addition of foundry sand to the top soil will improve the trafficability without increasing the CO2 emission. In the Swedish part of the CAOS project, a field experiment (Randomized block design, 3x3) was set up at a former cultivated, but now abandoned, fen peat located at Bälinge Mossar (60.02821N, 17.43008E). We will compare trafficability, yield and CO2 emission from plots sown with Phleum pretense and treated with 0 cm, 2.5 cm or 5 cm foundry sand. The sand was applied in the autumn of 2015 and mixed in the top 10 cm of the soil. Penetration resistance, yield and CO2 emissions will be compared during three years. The first preliminary results (15/9-1/11) show that the CO2 emissions is highest from the plots without sand addition (3.4 µmol*m-2s-1) and lowest from the plots where 5 cm sand was added (1.4 µmol*m-2s-1). The emission from the 2.5 cm treatment was 1.8 µmol*m-2s-1. Yield and trafficability have not been measured yet, but it is promising that the CO2 emission from the plots with sand addition was much lower than untreated soils

Site characteristics determine the duration of structure liming effects on clay soil

Adding carbonated or non-carbonated lime to clay soils can lead to changes in aggregate stability. In Sweden, 'struc-ture liming' with a mixed product (normally 80-85% calcium carbonate and 15-20% calcium hydroxide) is subsidised through environmental schemes to increase aggregate stability, thereby mitigating losses of particulate phosphorus (PP). This study assessed the effects of structure liming on aggregate stability in eight clay soils in southern Swe-den, using turbidity as a proxy for aggregate stability. Turbidity in leachate from simulated rain events performed on aggregates (2-5 mm) in the laboratory was measured one and six years after application of four treatments 0, 4, 8 and 16 t ha-1 of a mixed structure liming product. The effect on turbidity was analysed for all application rates, but also as the contrast between the unlimed control and the mean of the limed treatments, to identify the gen-eral effect. A significant effect of structure liming on turbidity was found after one year. The effect decreased over time, but was still detectable after six years. However, there was a significant interaction between trial and treat-ment, indicating different reactions on different soils and suggesting that not all clay soils are suitable for structure liming if the desired objective is to lower the risk of PP losses. Clay content, initial pH and mineralogy may explain the different responses to structure liming. These findings show a need for a site-specific structure liming strategy. As a tentative recommendation, soils with a minimum clay content of approximately 25-30% and pH <7 should be preferred for structure liming

Emissions of N2O from peat soils under different cropping systems

Drainage of peatlands for agriculture use leads to an increase in nitrogen turnover rate causing emissions of N2O to the atmosphere. Agriculture contributes to a substantial part of the anthropogenic emissions of N2O therefore mitigation options for the farmers are important. Here we present a field study with the aim to investigate if the choice of cropping system can mitigate the emission of N2O from cultivated organic soils. The sites used in the study represent fen peat soils with a range of different soil properties located in different parts of southern Sweden. All sites are on active farms with good drainage

Vallodling på torvjord – skördenivåer och växthusgasavgång

Avkastning och växthusgasavgång på odlad kärrtorvjord har studerats 2015–2022 på Broddbo fältlaboratorium, ca 25 km NNV Uppsala. Behandlingarna inkluderar jämförelser av olika gräs (timotej, rörflen och rörsvingel), packning med traktor eller opackad mark. Dessutom har tillförsel av gjuterisand eller kalk studerats samt olika nivåer av kalium- och fosforgödsel. Avkastningen har ökat med vallens ålder och trots torkan 2018 levererade dessa jordar stor avkastning. Störst avkastning i gräsjämförelsen gav rörflen med över 15 ton ts/ha. I sandförsöket blev det störst minskning av koldioxidemissioner på de sandkörda leden. Skörden av timotej blev stor (över 17 ton ts/ha) när 2,5 cm sand blandats in i ytan