Strategies to reduce nutrient pollution from manure management in China

As the demand for livestock products continues to increase in China, so too does the challenge of managing increasing quantities of manure. Urgent action is needed to control point source (housing, storage and processing) and diffuse (field application) pollution and improve the utilization of manure nutrients and organic matter. Here, we review strategies to improve management at each stage of the manure management chain and at different scales. Many strategies require infrastructure investment, e.g., for containment of all manure fractions. Engineering solutions are needed to develop advanced composting systems with lower environmental footprints and design more efficient nutrient stripping technologies. At the field-scale, there is an urgent need to develop a manure nutrient recommendation system that accounts for the range of manure types, cropping systems, soils and climates throughout China. At the regional scale, coordinated planning is necessary to promote recoupling of livestock and cropping systems, and reduce nutrient accumulation in regions with little available landbank, while minimizing the risk of pollution swapping from one region to another. A range of stakeholders are needed to support the step change and innovation required to improve manure management, reduce reliance on inorganic fertilizers, and generate new business opportunities

Towards country-specific nitrous oxide emission factors for manures applied to arable and grassland soils in the UK

Nitrous oxide (N2O) emission factors (EFs) were calculated from measurements of emissions from livestock manures applied to UK arable crops and grassland as part of a wider research programme to reduce uncertainty in the UK national agricultural N2O inventory and to enhance regional inventory reporting through increased understanding of processes and factors controlling emissions. Field studies were undertaken between 2011 and 2013 at 3 arable and 3 grassland sites in the UK. Nitrous oxide emissions were measured following the autumn and spring application of different manures (pig slurry, cattle slurry, cattle farmyard manure (FYM), pig FYM, poultry layer manure, and broiler litter) at typical rates, using representative manure application and soil incorporation methods. In addition, ammonia emissions and nitrate leaching losses (1 site on a light sandy soil) were measured to calculate indirect N2O losses. IPCC comparable, direct N2O EFs ranged from −0.05 to 2.30% of total nitrogen applied, with the variability driven by a range of factors including differences in manure composition, application method, incorporation and climatic conditions. When data from the autumn applications were pooled, the mean N2O EF from poultry manure (1.52%) was found to be greater (P < 0.001) than from FYM (0.37%) and slurry (0.72%), with no difference found (P = 0.784) in the EF for bandspread compared with surface broadcast slurry application, and no effect (P = 0.328) of the nitrification inhibitor, Dicyandiamide (DCD). For the spring applications, the mean N2O EF for bandspread slurry (0.56%) was greater (P = 0.028) than from surface broadcast slurry (0.31%), but there were no differences (P = 0.212) in the mean N2O EFs from poultry manure (0.52%), slurry (0.44%), and FYM (0.22%). The study did confirm, however, that DCD reduced N2O emissions from slurries applied in the spring by 45%. EF data from this project have been used in the derivation of robust Tier 2 country specific EFs for inclusion in the UK national agriculture greenhouse gas inventory

Emissions of ammonia, nitrous oxide and methane during the management of solid manures

Organic manures arising from livestock production provide a source of plant nutrients when applied to agricultural land. However, only about 52% of the N excreted by livestock is estimated to be recycled as a plant nutrient. The ­greatest losses of N from livestock excreta and manures are as gaseous emissions. These emissions are in the form of ammonia (NH3), nitrous oxide (N2O) and methane (CH4). Ammonia forms particles in the atmosphere which reduce visibility and may also harm human health, and when deposited to land NH3 causes nutrient enrichment of soil. Nitrous oxide and CH4 contribute significantly to global warming and N2O can also cause the breakdown of the protective ozone layer in the upper atmosphere. We established a database of emissions from solid manures. Statistical analysis provided new information, focussing on developing emission factors, emission algorithms and also new understanding of emission patterns from solid manure. The review found that housing systems with deep litter emit more NH3 than tied stalls. This is likely to be because the emitting surface area in a tied stall is smaller. Laying hens emit more NH3 than broilers and reduced-emission housing systems for poultry, including the aviary system, can reduce NH3 emissions by between 50% and 80%. The greatest N2O-N emissions from buildings housing livestock were also from deep litter systems, but the amount of N2O-N was smaller than that of NH3-N by a factor of 15. Air exchange and temperature increase induced by aerobic decomposition during manure storage may greatly increase NH3 emission. Emissions of 0.25–0.30 of the total-N have been recorded from pig and cattle manure heaps undergoing aerobic decomposition. Increased density of manure during storage significantly decreased temperatures in manure heaps. Storing solid manures at high density also reduces air exchange which with the low temperature limits the formation and transfer of NH3 to the surface layers of the heap, reducing emissions. Most N2O emission estimates from cattle and pig manure have been between 0.001 and 0.009 of total-N. Emission of N2O from poultry manure tends to be small. Average unabated NH3 emissions following application of manure were 0.79, 0.63 and 0.40 of total ammoniacal-N (TAN) from cattle, pig and poultry manure respectively. The smaller emission from poultry manure is expected as hydrolysis of uric acid to urea may take many months and is often incomplete even after application, hence limiting the potential for NH3 emission. Manure incorporation within 4 h after application reduced emission on average by 32%, 92% and 85% for cattle, pig and poultry manure respectively. Reductions following incorporation within 24 h or more after application were 20%, 56% and 50% for cattle, pigs and poultry, respectively. Incorporation by disc or harrow reduced NH3 emissions less than incorporation by plough. Emissions of N2O following the application of cattle manure were 0.12 of TAN without incorporation after application and 0.073 TAN with incorporation after application. Conversely, emissions following application of pig and poultry manures were 0.003 and 0.001 TAN respectively without and 0.035 and 0.089 TAN respectively with incorporation after application

How do NH3 emissions relate to nitrogen use efficiency of livestock production?

Ammonia (NH3) emissions from livestock production systems can be substantial but difficult to measure. Here we explore the relationship between NH3 emissions, the emission intensity (NH3-N emitted/product N) and the more easily measured feed Nitrogen Use Efficiency (NUE). Using a conceptual model, we find that the relationship between emission intensity and NUE is equivalent to that between NH3-N emission and feed N intake. Furthermore, there is a linear relationship between the two, with a slope that is dependent on characteristics of the animal and its feed, and the manure management system. This is illustrated using data taken from the emission inventories of six European countries, which found a linear relationship, with much variation within a commodity type. Using the same data, we show how the effects of animal and feed characteristics can be separated from those of the manure management system

How should the impact of different presentations of treatment effects on patient choice be evaluated? A pilot randomized trial

BACKGROUND: Different presentations of treatment effects can affect decisions. However, previous studies have not evaluated which presentations best help people make decisions that are consistent with their own values. We undertook a pilot study to compare different methods for doing this. METHODS AND FINDINGS: We conducted an Internet-based randomized trial comparing summary statistics for communicating the effects of statins on the risk of coronary heart disease (CHD). Participants rated the relative importance of treatment consequences using visual analogue scales (VAS) and category rating scales (CRS) with five response options. We randomized participants to either VAS or CRS first and to one of six summary statistics: relative risk reduction (RRR) and five absolute measures of effect: absolute risk reduction, number needed to treat, event rates, tablets needed to take, and natural frequencies (whole numbers). We used logistic regression to determine the association between participants' elicited values and treatment choices. 770 participants age 18 or over and literate in English completed the study. In all, 13% in the VAS-first group failed to complete their VAS rating, while 9% of the CRS-first group failed to complete their scoring (p = 0.03). Different ways of weighting the elicited values had little impact on the analyses comparing the different presentations. Most (51%) preferred the RRR compared to the other five summary statistics (1% to 25%, p = 0.074). However, decisions in the group presented the RRR deviated substantially from those made in the other five groups. The odds of participants in the RRR group deciding to take statins were 3.1 to 5.8 times that of those in the other groups across a wide range of values (p = 0.0007). Participants with a scientific background, who were more numerate or had more years of education were more likely to decide not to take statins. CONCLUSIONS: Internet-based trials comparing different presentations of treatment effects are feasible, but recruiting participants is a major challenge. Despite a slightly higher response rate for CRS, VAS is preferable to avoid approximation of a continuous variable. Although most participants preferred the RRR, participants shown the RRR were more likely to decide to take statins regardless of their values compared with participants who were shown any of the five other summary statistics. TRIAL REGISTRATION: Controlled-Trials.com ISRCTN85194921