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Edinburgh, United Kingdom

Ball B.C.,SAC Crop and Soil Systems Research Group | Cameron K.C.,Lincoln University at Christchurch | Di H.J.,Lincoln University at Christchurch | Moore S.,Lincoln University at Christchurch
Soil Use and Management | Year: 2012

Urine patches in dairy pastures are major sources of nitrous oxide (N 2O). Wet winters result in compaction damage to pastures because of animal trampling. The nitrification inhibitor, dicyandiamide (DCD), is effective at reducing N 2O emissions from urine patches. Here, we assessed the extent of damage to the physical quality of the soil by trampling and whether this influenced the ability of DCD to mitigate N 2O emissions. A field experiment was conducted where a sandy loam soil was trampled by a mechanical hoof just before urine and DCD application. Trampling reduced air permeability and pore continuity, but this had no effect on bulk density. Urine appeared to have contributed to pore collapse and blockage. Trampling increased average cumulative N 2O emissions from 1.74 to 4.66% of urine-N applied. This effect was attributed to increased water-filled pore space, aggregate destruction and suppression of grass growth. DCD was highly effective in reducing N 2O emissions, with the N 2O emission factor of the urine-N being decreased by 58-63%. Trampling did not significantly affect the effectiveness of DCD in reducing N 2O emissions. © 2012 The Authors. Journal compilation © 2012 British Society of Soil Science.

Guimaraes R.M.L.,State University of Maringa | Ball B.C.,SAC Crop and Soil Systems Research Group | Tormena C.A.,State University of Maringa
Soil Use and Management | Year: 2011

Spade methods to visually evaluate soil structural quality (Sq) are simple, quick, cheap and can be used by farmers, gardeners, consultants and the scientific community. However, European and Brazilian users of one such method, viz. visual evaluation of soil structure (VESS) which is a development of the Peerlkamp test, have been concerned about its subjectivity. The method of soil slice break-up and operator influence on scores have been questioned. Thus, our aim was to make soil scoring by the VESS technique more objective and thus to revise the scoring guide. We compared scoring with normal breaking up of the soil slice by hand with scoring after breaking up the slice by dropping (drop shatter) to make the soil break-up more operator independent. After slice break-up, aggregates were split by hand and their internal porosity was evaluated to develop the use of visible porosity as an aid to scoring. This proved inconclusive on its own, so a method of reducing larger aggregates to 1.5-2.0cm core fragments and describing their shape and porosity was developed to score soil Sq. Breaking up a spadeful of soil by hand or by dropping resulted in the same Sq score. The method of reducing aggregates and evaluation of their shape improved VESS, particularly in the middle range of soil quality and the revised chart is shown. VESS was sensitive to changes in Sq in layers within the profile and its use for diagnosing Sq in different layers allows targeted soil improvement by tillage. © 2011 The Authors. Journal compilation © 2011 British Society of Soil Science.

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