Use of ammonium sulphate as a sulphur fertilizer: implications for ammonia volatilization

Ammonium sulphate is widely used as a sulphur (S) fertilizer, constituting about 50% of global S use. Within nitrogen (N) management it is well known that ammonium-based fertilizers are subject to ammonia (NH3) volatilization in soils with pH >7, but this has been overlooked in decision making on S fertilization. We reviewed 41 publications reporting measurements of NH3 loss from ammonium sulphate in 16 countries covering a wide range of soil types and climates. In field experiments loss was mostly 7.0 there was a wide range of losses (0-66%), with many in the 20-40% range and some indication of increased loss (ca. 5-15%) in soils with pH 6.5-7.0. We estimate that replacing ammonium sulphate with a different form of S for arable crops could decrease NH3 emissions from this source by 90%, even taking account of likely emissions from alternative fertilizers to replace the N, but chosen for low NH3 emission. In temperate climates emission from soils of pH >7.0 would decrease from 35.7 to 3.6 t NH3 per kt ammonium sulphate replaced. Other sources of S are readily available including single superphosphate, potassium sulphate, magnesium sulphate, calcium sulphate dihydrate (gypsum) and polyhalite (Polysulphate). In view of the large areas of high pH soils globally, this change of selection of S fertilizer would make a significant contribution to decreasing NH3 emissions worldwide, contributing to necessary cuts to meet agreed ceilings under the Gothenburg Convention

Nuclear imaging in the diagnosis of primary aldosteronism.

PURPOSE OF REVIEW: Primary aldosteronism is increasingly recognized as a common secondary cause of hypertension. Successful demonstration of a unilateral cause (e.g. a classical 'Conn's adenoma') offers the potential for curative adrenalectomy. Adrenal vein sampling (AVS), in conjunction with cross-sectional imaging, remains the 'gold standard' for distinguishing unilateral and bilateral disease, but is technically demanding and frequently unsuccessful or inconclusive. As such, alternative strategies for lateralization, including nuclear medicine techniques, are being developed and brought into clinical practice. RECENT FINDINGS: Metomidate, a potent ligand of CYP11B1 and CYP11B2, can be C11H3-labelled as a PET tracer and has been shown to offer a rapid noninvasive alternative to AVS for localizing unilateral aldosterone-producing adenomas. SUMMARY: Increasing experience with 11C-metomidate PET-CT supports its use as an adjunct to AVS when this has failed, is ambiguous, or cannot be undertaken.A.S.P. and M.G. are supported by the National Institute for Health Research Cambridge Biomedical Research Centre. M.J.B. is a National Institute of Health Research Senior Investigator.This is the final published version. It first appeared at http://journals.lww.com/co-endocrinology/Fulltext/2015/06000/Nuclear_imaging_in_the_diagnosis_of_primary.3.aspx

Why do we make changes to the long-term experiments at Rothamsted?

The long-term field experiments at Rothamsted in south-east England (UK) are an important resource that has been used extensively to study the effects of land management, atmospheric pollution and climate change on soil fertility and the sustainability of crop yields. However, for these and other long-term experiments around the world to remain useful, changes are sometimes needed. These changes may be required to ensure that the experiment is not compromised by e.g. acidification or weeds, but often they are needed to ensure that the experiment remains relevant to current agricultural practice, e.g. the introduction of new cultivars and the judicious use of pesticides. However, changes should not be made just for the sake of change or to investigate aspects of management that could be better resolved in a short-term experiment. Rather, modifications should only be made after carefully considered discussion, involving scientists from different disciplines. It must be remembered however that there are limitations to what can be achieved in one experiment. In this paper we give examples of why certain changes were made to the Rothamsted experiments and what the results of those changes have been. We also highlight the value of archiving crop and soil samples for future studies

Is it possible to attain the same soil organic matter content in arable agriculture soils as under natural vegetation?

Clearing natural vegetation to establish arable agriculture (cropland) almost invariably causes a loss of soil organic carbon (SOC). Is it possible to restore soil that continues in arable agriculture to the pre-clearance SOC level through modified management practices? To address this question we reviewed evidence from long-term experiments at Rothamsted Research, UK, Bad Lauchstädt, Germany, Sanborn Field, USA and Brazil and both experiments and surveys of farmers’ fields in Ethiopia Australia, Zimbabwe, UK and Chile. In most cases SOC content in soil under arable cropping was in the range 38-67% of pre-clearance values. Returning crop residues, adding manures or including periods of pasture within arable rotations increased this, often to 60-70% of initial values. Under tropical climatic conditions SOC loss after clearance was particularly rapid, e.g. a loss of >50% in less than 10 years in smallholder farmers’ fields in Zimbabwe. If larger yielding crops were grown, using fertilizers, and maize stover returned instead of being grazed by cattle, the loss was reduced. An important exception to the general trend of SOC loss after clearance was clearing Cerrado vegetation on highly weathered acidic soils in Brazil and conversion to cropping with maize and soybean. Other exceptions were unrealistically large annual applications of manure and including long periods of pasture in a highly SOC-retentive volcanic soil. Also, introducing irrigated agriculture in a low rainfall region can increase SOC beyond the natural value due to increased plant biomass production. For reasons of sustainability and soil health it is important to maintain SOC as high as practically possible in arable soils, but we conclude that in the vast majority of situations it is unrealistic to expect to maintain pre-clearance values. To maintain global SOC stocks at we consider it is more important to reduce current rates of land clearance and sustainably produce necessary food on existing agricultural land

Response to ‘A well-established fact: Rapid mineralization of organic inputs is an important factor for soil carbon sequestration’ by Angers et al.

Letter to the edito

Milling plant and soil material in plastic tubes over-estimates carbon and under-estimates nitrogen concentrations

Peer reviewedPostprin