Improved Manure Management Research Articles

Manure as a key resource within smallholder farming systems: Analysing farm-scale nutrient cycling efficiencies with the NUANCES framework

Smallholder farmers in Africa recognise the important role of manure in maintaining soil fertility. For smallholder farmers who use little fertiliser, efficient management of nutrients in manure is key for crop production. We describe a simple model to analyse the effect of manure management on the efficiency of mass and nutrient retention. We used on-farm data on manure excreted and manure management, experimental results, literature and fuzzy logic to model losses during manure storage. The model was used to analyse N cycling efficiency (NCE) within smallholder farms in western Kenya. Simulations showed that manure management during collection and storage had a large effect on the efficiency of C and nutrient retention. Differences in NCE between farmers of different wealth classes arose due to differences in resource endowment. For poorer farmers, large N losses occur at all stages of manure recycling. Urinary-N losses occurred on all farms but their impact on NCE for poor and medium-class farmers was larger due to the smaller amount of N recycled. With current management the poor farmer recovered < 1 kg N y − 1 in composted manure from 15 kg N y − 1 excreted. Improved manure storage had little effect on increasing overall NCE for the poor farmer due to large losses before storage. For the wealthier farmer improvement of manure storage increased NCE and allowed recycling of 30% of N excreted (ca. 30 kg N y − 1 ) with small investment in infrastructure. Covering manure heaps with a polythene film reduced mass and N losses considerably. For the poor to increase overall NCE, investment in cattle housing and recycling of urinary-N is required. Increasing cattle numbers or improved feeding would have a larger effect on manure availability but this is constrained by feed scarcity and investment capacity. The absolute amounts of N recycled (1–6, 4–17 and 7–18 kg N y − 1 for poor, medium and wealthier farmers) were small compared with maize N demand (> 50 kg N ha − 1 ), but significant given the small farm sizes (0.1–1.1 ha). Although absolute amounts of N recycled with improved manure management may have little immediate impact on crop productivity, manure is often the only input available. Manure provides other nutrients for crops and maintains soil organic matter — both vital to guarantee efficient use of fertiliser N — which justifies the search for interventions to assist farmers make better use of manure.

Potential of anaerobic digestion for mitigation of greenhouse gas emissions and production of renewable energy from agriculture: barriers and incentives to widespread adoption in Europe

The paper considers the role of anaerobic digestion in promoting good agricultural practice on farms and the contribution this would make to reducing the environmental impacts associated with manure management. There are no regulatory drivers to promote the use of digestion in Europe, and the technology has only been widely adopted where economic drivers and coherent policies have been implemented at a national level. These measures have included direct subsidy on the energy price paid for "green electricity", and exemption of tax when biogas is used as a vehicle fuel. In those countries where financial incentives are not available or where a financial penalty is incurred through the regulatory regime, the uptake of digestion has been poor. Even with subsidies, digestion of animal manures as a single substrate is not common, and countries with successful schemes have achieved this either by permitting the import of wastes onto the farm or offering bonus subsidies for the use of energy crops. Both of these measures improve the energy efficiency of the process by increasing the volumetric methane production, although concerns are expressed that attention could concentrate on energy production at the expense of improving manure management.

Nitrogen budgets and losses in livestock systems

Livestock farming systems encompass (i) grazing, (ii) mixed, and (iii) land-less systems. These systems convert crop protein into animal protein with an efficiency ranging from 5% to 45%, depending on animal type, system and management. The nitrogen (N) in the remaining fraction (55–95%) is in urine and dung, and is conducive to N losses. This paper reviews N input–output budgets and N losses in livestock farming systems. Systems differ in N inputs, outputs and budgets. Generally, N inputs and N losses increase in the order grazing systems < mixed systems < land-less systems. The estimated global amount of manure N ranges between 75 and 138 Tg N/year. Cattle (56–60%), sheep (12%) and pigs (6%) have the largest share in manure N production. Roughly 40–50% of manure N is collected in barns, stables and paddocks, and only half of this amount is recycled to cropland. Gaseous N losses from manure N are estimated at 45–75 Tg/year. There are opportunities for decreasing N losses and improving animal feed conversion efficiency by improving the composition of the animal feed and the genetic production potential of the herd. A major challenge lies in improving manure management.

Improved manure management and utilization: A systems approach

AbstractThe manure issue is complex and inherently interdisciplinary but, more fundamentally, it requires systems thinking. Current policies, technologies, infrastructure, incentives and modes of thinking about the problem fail to consider the system-wide implications, and thus fail to foster the creation of new and innovative solutions. At the farm level, complexity, uncertainty and lack of compatibility with the current farming system need to be addressed in order to promote better manure management. Production facilities, feed management and waste treatment systems (including centralized treatment plants) need to be designed to allow for beneficial use of manure components. At the industry level, changes in the poultry, swine and beef industries have resulted in concentration, both in terms of decision-making and geography. This currently limits the ability of these farmers to take a systems approach to livestock production. Environmental policies thus need to take account and advantage of this new reality. At the economy-wide level, factors affecting the demand and supply for alternative manure products need to be considered. A number of innovative uses are being developed in the private sector, but there are constraints as far as technology, institutions and infrastructure are concerned. A systems perspective will allow the design of policies and technologies that reduce environmental problems associated with manure, while promoting efficient utilization of the resource.

Environmental aspects of the anaerobic digestion of the organic fraction of municipal solid wastes and of solid agricultural wastes

In order to obtain more detailed information for better decision making in future biogenic waste treatment, different processes to treat biogenic wastes in plants with a treatment capacity of 10,000 tons of organic household wastes per year as well as agricultural codigestion plants were compared by life cycle assessments (LCA). With the tool EcoIndicator, anaerobic digestion is shown to be advantageous as compared to composting, incineration or a combination of digestion and composting, mainly because of a better energy balance. The management of the liquid manure in agricultural codigestion of organic solid wastes causes increased gaseous emissions, which have negative effects on the LCA, however. It is recommended to cover the slurry pit and to use an improved manure management in order to compensate for the additional gaseous emissions. In the LCAs, the quality of the digester output could only be taken into account to a small extent; the reasons are discussed.

OPTIMUM COAGULANT AND FLOCCULANT CONCENTRATIONS FOR SOLIDS AND PHOSPHORUS REMOVAL FROM PRE-SCREENED FLUSHED DAIRY MANURE

Concentrated animal feeding operations (CAFO) using water-flush systems creates excessive manure slurriescontaining high solids and phosphorus (P). Using pre-screened slurry (1.0 mm) in Part I, optimum combinationconcentrations for dewatering for two coagulants (AlCl3 and FeCl3) and one flocculant (255G-PAM) were identified. In afollow-up separate experiment in Part II, the identified optimum concentrations were evaluated for their total solids (TS) andtotal P (TP) removal capability using the same type of pre-screened slurry (1.0 mm) in combination with a 0.5-mm staticscreen. In Part I, aluminum (Al) and iron (Fe) alone increased dewatering 70 to 80 times compared to the control, decreasedfiltrate pH as their respective concentrations increased, and decreased filtrate total dissolved P (TDP). Coagulants combinedwith 255G-PAM enhanced the dewatering capabilities 1.5 to 1.7 times at lower coagulant concentrations. Interactionbetween the coagulants and 255G-PAM dewatered the slurry and removed P more efficiently than the control or coagulantsalone. In Part II, the TP removed was directly correlated to the quantity of screened solids removed (R2 = 0.92). Treatments(on screen) removed 3 to 8 times more TS and 6 to 25 times more TP than the control, with mean recoveries of 100% and 76%for TS and TP, respectively. Interaction between the coagulants and 255G-PAM removed TS and TP more efficiently comparedto the control and coagulants alone. Treatments reduced the amount of TDP in the filtrate 87 to 182 times, demonstrating thistechnology has potential for improving manure management provided chemical treatment can be combined with solidseparation on a practical and commercial scale.

Comparison of Estimates of First‐Year Dairy Manure Nitrogen Availability or Recovery Using Nitrogen‐15 and Other Techniques

Measurements of dairy manure nutrient availability to crops typically show great variability. Approaches that are more accurate are needed to improve manure management and reduce nutrient loss to the environment. In this study, we compared direct (15N recovery) and indirect (difference method [Diff Meth] and fertilizer equivalence [FE] approach) methods of determining first-year dairy manure N availability or recovery during three cropping seasons. A field experiment was conducted on a Plano silt loam (fine-silty, mixed, superactive, mesic Typic Argiudolls) planted to corn (Zea mays L.). Plots received either manure, fertilizer N, or no N. Microplots receiving 15N-labeled manure were also established each study year. Manure was applied to a new plot each cropping season. Whole-plant N uptake was the best crop parameter to use for FE estimates. Estimates of N availability by relative effectiveness (Rel Eff), which are derived from the Diff Meth, and FE were similar (32 and 41%, respectively) and higher than unlabeled N or 15N recovery measurements because these indices factor in N use efficiency. Measures of the Rel Eff of manure N use were highly affected by control plot N uptake. The FE approach is less influenced by control plots, but it requires the inclusion of several more treatments and use of mathematical functions to describe crop response to N. These limitations are reflected in the wide ranges obtained for N availability estimates (-60 to 148%). Although apparent N recovery by the Diff Meth (14%) or direct measurements of 15N recovery (16%) were close on average, variability tended to be much lower for the 15N method. In addition, the Diff Meth was highly dependent on initial soil conditions. Use of 15N-labeled manure, although more costly and time-consuming, provided more consistent and reliable results.

MANAGEMENT OF MANURE IN FARMING SYSTEMS IN SEMI-ARID WEST AFRICA

The last 50 years have seen a rapid expansion of cultivated area in semi-arid areas of West Africa. This has precipitated a change from traditional fallowing to more pro-active soil fertility management techniques. Smallholder farmers employ a range of technologies to enhance soil fertility and manure is a cornerstone of many of the soil fertility management strategies they use. This paper reviews manure management by smallholder farmers. It considers factors that affect the quality of the manure used, including methods for keeping livestock and storing manure. The paper reviews the strategies, such as night parking and crop-livestock integration, which farmers employ to ensure that manure reaches their fields. The nutrient balances of two farming systems are presented as evidence for the importance of manure as a nutrient source. Rangeland-to-cropland nutrient transfers are contrasted with nutrient recycling through crop-livestock integration. The paper concludes that within the constraints in which smallholder farmers operate in semi-arid West Africa, manure will remain an important component of soil fertility management strategies for the foreseeable future. Integrated nutrient management strategies that take into consideration the circumstances of farmers, and the resources available to them, are the best way forward. Appropriate interventions need to focus on improving manure management to ensure that the material which farmers so laboriously prepare and transport is of the best possible quality.

Nitrogen‐15 Labeling of Dairy Feces and Urine for Nutrient Cycling Studies

Estimates of the availability of dairy manure nutrients to crops rely on indirect measurements and can vary greatly. More accurate estimates of manure nutrient availability are needed to improve manure management. The objective of this study was to enrich dairy feces and urine in 15N to study nutrient flow in the feed–animal–manure–soil and crop–environment continuum. Ammonium sulfate (12.3 or 10 atom % 15N) was applied to soil to enrich alfalfa (Medicago sativa L.) and corn (Zea mays L.) plants during growth. Alfalfa hay contained from 2.386 to 3.980 atom % 15N in three harvests and corn silage contained 8.162 atom % 15N. A feed mixture containing 55% alfalfa hay and 45% corn silage (4.026 atom % 15N) was fed to two mature nonlactating cows (Bos taurus) for 36 h. The pattern of 15N excretion in urine and feces was similar for both cows. The 15N appeared in urine by 8 h and in feces by 24 h, and peaked by 30 h in urine (1.642 atom % 15N) and by 54 h in feces (2.341 atom % 15N). Enrichment approached basal levels at 132 h after initial feeding for both urine and feces. Of the total 15N fed, 60% was recovered: 31% from urine and 29% from feces. Approximately 60 to 70% of the total N excreted in dairy feces was endogenous N and 30 to 40% was undigested feed N. Combining feces excreted during the 16‐ to 122‐h period after initial feeding of 15N‐enriched feed would produce feces having uniformly labeled N components. The various 15N‐enrichment levels of urine and feces collected during different times after feeding offer possibilities for studying differential 15N use in short‐ and long‐term nutrient cycling studies.

The effect of nitrogen management in agricultural production on water and air quality: evaluation on a regional scale

The purpose of this study was to use a nitrogen (N) budget calculation approach to estimate the effect of agricultural production in the Lower Fraser Valley, British Columbia, Canada, on N loss to the environment under 1991 crop and animal management practices, the change in N loss to the environment between 1981 and 1991, and the extent to which these losses could be reduced through improved management practices. Ammonia losses to the atmosphere from animal production were substantial, in excess of 7250 (t N) year −1, but could be reduced by up to 30% through improved manure management and animal diets. Root-zone N losses to surface and groundwater were estimated as the N surplus (the excess of N additions from inorganic fertilizer, manure, and atmospheric deposition over N removals by the crop and denitrification) for the root zone of land in agricultural production. The N surplus for the study area as a whole was 68 (kg N) ha −1 land in agricultural production, whereas an N surplus of <50 (kg N) ha −1 would be expected under optimal N management. Calculation of N surplus values on the basis of individual districts as compared to the entire study area predicted a greater effect of agricultural production on water quality because of a non-optimal distribution of nutrients. High N surplus values within individual districts, up to 238 (kg N) ha −1, were attributed to animal intensification, particularly poultry and swine production which does not require a local land base for feed production. Root-zone N losses increased between 1981 and 1991, primarily because of the concentration of animal production in specific geographical areas and on a diminished agricultural land base. Improved fertilizer and manure management was predicted to reduce the N surplus of the study area from 68 to 5 (kg N) ha −1; however, less than one-half of this reduction could be practically realized at this time. Improved animal diets were predicted to reduce the N surplus from 68 to 45 (kg N) ha −1, with most of the reduction occurring in areas with high root-zone N losses. The results demonstrate the value of using an N balance approach to evaluate the environmental effect of agricultural production on air and water quality, and to assess how this effect could be reduced through improved management practices.

LSI testing: a three-way street

Low nitrogen (NUE) and phosphorus (PUE) use efficiencies in food production in China result in large losses of nitrogen (N) and phosphorus (P) to the environment. The Chinese government formulated policies to increase the NUEs and PUEs. Recent policies aim for zero growth in synthetic fertilizer use after 2020 while ensuring food security. In this study we analyzed how current and improved nutrient management in China can affect future nutrient use efficiencies and nutrient losses from food production. The NUEs and PUEs of food production were quantified using the NUFER (NUtrient flows in Food chains, Environment and Resources use) model for 31 provinces and China in 2013, 2020 and 2050. Results show that national NUE (20%) and PUE (24%) in 2013 are low but vary largely among provinces (12–33% for NUE, 10–53% for PUE). The N and P losses to the air (14 Tg year− 1 of N) and waters (12 Tg year− 1 of N, 2 Tg year− 1 of P) are consequently high in 2013. Three scenarios were analyzed for 2020 and 2050 to explore future trends in NUEs and PUEs, assuming Business As Usual (BAU) trends, Zero Fertilizer (ZF) growth from 2020, and Improved Nutrient Management (INM). In the BAU scenario, the NUEs and PUEs roughly remain at their low 2013 levels, while nutrient inputs to agriculture are increasing. The losses to the air therefore increase by 37% for N and to waters by 40% for N and 48% for P between 2013 and 2050. In the ZF scenario, the NUEs and PUEs are a few percent higher than in BAU. The associated N and P losses to waters are 8–16% lower than in BAU because of increased recycling of manure to cropland, but still higher than in 2013. Improved nutrient management, as assumed in our INM scenario, may increase NUEs and PUEs to 33% and 59% in 2050. Meanwhile, N and P losses to waters in 2050 are 47% and 83% lower than in 2013, and losses of N to the air 20% lower. We conclude that the policy aimed at zero growth in fertilizer use is a good start, but not very effective in reducing nutrient pollution in China. To substantially reduce N and P losses to the environment it is needed to improve nutrient management by not only reducing fertilization without yield losses, but also by improved manure management and animal production with lower nutrient excretion.