Hugh Riley
Research Scientist (OAP Agreement)
Abstract
The effectiveness of mechanical subsoiling for alleviating subsoil compaction is controversially discussed, particularly due to the sensitivity of mechanically loosened soils towards re-compaction. In order to improve the alleviation potential by subsoiling it was hypothesized that the loss of soil stability by mechanical subsoiling of compacted soils can be reduced by top and subsoil liming. The primary objective was to evaluate whether (a) mechanical subsoiling (to a depth of 35 cm with a subsoiler or a plough with a pan-breaker) could alleviate compaction in a clayey Stagnosol and (b) whether liming could stabilize soil structure to minimize re-compaction. Undisturbed soil samples were collected to assess physical properties in both "compacted", "subsoiled", and "limed", as well as in untreated plots. The Compaction Verification Tool (CVT) identified potentially harmful soil compaction in the subsoil. The results showed that wheeling increased the extent of harmful subsoil compaction (from 8% to 33%) in the first year, which was accompanied with a reduction in crop yields. Subsoiling with a pan-breaker combined with high liming intensity improved soil physical properties and yields and may have mitigated re-compaction in the loosened subsoil. Nevertheless, it is expected to be not economically viable on the studied clay soil.
Authors
Alice Budai Daniel Rasse Thomas Cottis Erik J. Joner Vegard Martinsen Adam O'Toole Hugh Riley Synnøve Rivedal Ievina Sturite Gunnhild Søgaard Simon Weldon Samson ØpstadAbstract
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Authors
Tatiana Francischinelli Rittl Reidun Pommeresche Anders Johansen Håvard Steinshamn Hugh Riley Anne-Kristin LøesAbstract
Renewable energy in the form of biogas can be produced by anaerobic digestion (AD) of animal manure. However, there is still a lack of knowledge on the long-term effects of AD-treated manure on soil characteristics and crop productivity, compared with untreated manure. A field experiment was established in a perennial grass-clover ley in 2011 to study the effects on important soil and crop characteristics when the slurry from a herd of organically managed dairy cows is anaerobically digested. While the rate of manure application affected soil concentrations of extractable nutrients and pH, these variables were unaffected by AD. Soil organic matter (SOM) concentrations decreased in all plots and faster on the plots with high intrinsic SOM. The decrease was similar with application of untreated (non-digested) slurry (US) and anaerobically digested slurry (ADS), and it was not affected by application rates. The general decline may be explained by the initial high SOM content, the long-term effect of drainage, and higher temperatures with climatic change. US and ADS gave similar yields of grass-clover ley (2 cuts/year) and green fodder, on average 0.79 and 0.40 kg DM m−2, respectively. Clover yield was similar in manured treatments and the non-fertilized control. With respect to crop yields and chemical soil characteristics, long-term (10 years) effects of AD in an organic dairy cow farming system seem to be minor. The benefits of extracting energy from the slurry did not compromise grassland productivity or soil quality in the long term.