Abstract
Context In Sweden, mixtures of 80–85% ground limestone and 15–20% slaked lime (hereafter, ‘structure lime’) are used in subsidised environmental schemes to improve aggregate stability and mitigate phosphorus losses on clay soils. Aims This study investigated different rates of structure lime application and soil variables on aggregate stability on clay soils, and whether soil properties can predict aggregate stability following structure liming. Methods Increasing application rates of 0–16 t ha−1 of structure lime (SL0, SL4, SL8 and SL16) were tested in 30 field trials in Sweden. Soil aggregates (2–5 mm) were collected 1 year after liming and subjected to two rainfall events in a rain simulator. Key results Leachate turbidity after the second simulated rainfall event decreased significantly (13% and 20%, respectively, in SL8 and SL16) compared with SL0, indicating improved aggregate stability. There was a near-significant interaction (P = 0.056) between treatment and trial. Grouping by initial SR21022_IE1.gif (range 6.2–8.3), clay content (10–61%), soil organic matter content (SOM, 2.2–7.1) and clay mineralogy (SmV index, 0.2–3.8) revealed different effects on turbidity. Discriminant analysis of soil characteristics and four tillage variables correctly classified the outcome for 27 of the 30 trial sites. Conclusions Results show that structure liming can improve aggregate stability 1 year after liming, and can thereby prevent particulate P losses from soils with high clay and SOM content, low SmV index and low initial pH. The discriminant analysis also showed the importance of tillage for the outcome of structure liming. Implications Clay soil characteristics such as SOM and pH significantly affected aggregrate stability after structure liming.
Highlights
Received: 21 January 2021 Accepted: 9 November 2021 Published: 12 January 2022Cite this: Blomquist J et al (2022) Soil Research doi:10.1071/SR21022 OPEN ACCESSAcidification of soils is a process with both natural and human-made causes (Filipek 2011)
Denomination, date of spreading, clay mineralogy characterisation (SmV index) and tillage before and after spreading the structure lime to a normal depth of 5–15 cm are summarised in Supplementary Table S1, together with the crop grown in the first year after structure liming
The results showed that the effect of structure liming, measured as change in turbidity, was greater on soils with lower compared with higher initial pH values (Fig. 3a)
Summary
Received: 21 January 2021 Accepted: 9 November 2021 Published: 12 January 2022Cite this: Blomquist J et al (2022) Soil Research doi:10.1071/SR21022 OPEN ACCESSAcidification of soils is a process with both natural and human-made causes (Filipek 2011). Liming indirectly affects crop growth through the bioavailability of plant nutrients (Goulding 2016) and in the long-term, can increase crop yield (Haynes and Naidu 1998). In long-term liming trials at Rothamsted and Woburn in the UK, yields of most crops, with the exception of oats and potatoes, responded positively to the higher pH achieved by liming in the pH range 4.4–8.0 (Holland et al 2019). A recent survey of long-term field trials combined with an intensive soil monitoring programme in Sweden revealed that, among manageable yield variables studied, pH had the greatest potential to positively affect crop yield, even at values >6.5 ðpHðH2OÞÞ, indicating a need for revision of the Swedish pH recommendations (Kirchmann et al 2020). Frank et al (2019) found that soil physical improvements, such as increased plant-available water capacity, recorded 6 months after liming were absent
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