Mineral Fertilizer Equivalent Research Articles

Physico-chemical Characteristics and Nitrogen Use Efficiency of Nine Human Urine-Based Fertilizers in Greenhouse Conditions

Most of the nutrients in wastewater come from human urine and their recycling for agricultural purposes is very limited. After source separation, urine can be treated to produce various urine-based fertilizers. This study aims to characterize the nitrogen use efficiency of different urine-based fertilizers. Nine urine-based fertilizers were compared together with ammonium nitrate and cattle slurry in a greenhouse pot trial with English rye-grass, (Lolium perenne L.). The detailed physico-chemical characteristics of the fertilizers were analyzed. The biomass production and nitrogen uptake of the plants were measured. The nitrogen use efficiency and the mineral fertilizer equivalent were determined for each fertilizer. The urine-based fertilizers were classified in four types based on their nitrogen forms (ammonia, nitrate, urea, or organic). The mineral fertilizer equivalent of most urine-based fertilizers were above 85% and even higher than 100% for nitrified concentrated and acidified stored urine. The lowest mineral fertilizer equivalent were found for fermented fresh urine and the mixture of fresh urine and woodchips but remained between 65 and 75%. In all cases, the nitrogen use efficiencies of urine-based fertilizers were higher than that of cattle slurry. The differences among the urine-based fertilizers and from the cattle slurry were attributed to the mineral nitrogen content which was much higher in urine-based fertilizers. Indeed, they contain mainly mineral nitrogen. Their content of trace element contaminants is low. Their efficiency as nitrogen fertilizers is high and close to that of mineral fertilizer. However, new valorization pathways from cities to agriculture need to be developed.

EFFECT OF INTEGRATED NUTRIENT MANAGEMENT ON NUTRIENT USE EFFICIENCY OF MAJOR NUTRIENTS: A REVIEW

Nutrient use efficiency (NUE) is an important concept in the evaluation of crop production systems. With emerging nutrient deficiencies under intensive agriculture, there is a need to improve NUE. One of the approaches to enhance it is by judicious use of fertilizers (adequate rate, effective source, methods and time of application) as well as inclusion of organic manures. Organic nutrient sources are very effective but as their availability is not sufficient to meet the nutrient demand, we have to integrate both organic and inorganic sources of nutrients together in order to achieve higher NUE. Common measures of NUE include Partial Factor Productivity (PFP), Agronomic Efficiency (AE), Apparent Recovery Efficiency (RE), Physiological Efficiency (PE) and Internal Utilization Efficiency (IE). Mineral Fertilizer Equivalent (MFE) is another parameter that can be used to assess short term release of nutrients (mainly nitrogen) from organic nutrient sources

Characterizing phosphorus availability in waste products by chemical extractions and plant uptake

AbstractBackground: The fertilizer value of phosphorus (P) in waste products relies heavily on its availability to the subsequent crop.Aim: We studied the link between extractable P in waste products and apparent P recovery (APR, i.e., difference in plant P uptake between P amended and un‐amended soils divided by the amount of P added) using spring barley grown on three sandy soils.Methods: The products included sewage sludge, biomass ash, struvite, compost, meat and bone meal, biochar from sewage sludge, and industrial sludge. Soft rock phosphate and triple‐superphosphate (TSP) were included for comparison. Availability of P was characterized by extraction with water and solutions of sodium bicarbonate, citric acid, oxalic acid, hydrochloric acid, ammonium acetate, ammonium fluoride and anion exchange resin membranes. TSP was used to establish mineral‐fertilizer‐equivalents (MFE). Water and bicarbonate extractions were also applied to products incubated with soil before extraction.Results: The APR ranged 26 to 31% for TSP and 0 to 30% for waste products. APR correlated most strongly with bicarbonate extractable P. The correlation increased when products were incubated with soil before extraction.Conclusions: We conclude that bicarbonate extraction is a good indicator of potential P availability. However, interactions between waste products and soil properties modify P availability.

Agricultural use of organic residues in life cycle assessment: Current practices and proposal for the computation of field emissions and of the nitrogen mineral fertilizer equivalent

Agricultural utilization of organic residues is often included in Life cycle assessment (LCA) studies on livestock and crop production as well as waste and wastewater treatment. A review on the current state-of-the-art practices in agricultural use of organic residues in LCA studies is presented. This reveals that agricultural use of organic residues in LCA studies can be represented in several ways and at different levels of detail. About 100 published references were thoroughly analyzed showing that agricultural use of organic residues usually replaces the use of a mineral fertilizer (substitution of avoided mineral fertilizer). The mineral fertilizer equivalents (MFE) applied are rarely documented, although LCA results can be significantly affected by the way avoided impacts are modeled. Accounting of field emissions from organic residue application varies with the topic of the LCA study. To facilitate nitrogen MFE and field emission calculations, an Excel-tool is proposed for determining the nitrogen MFE of organic residues, direct nitrogen field emissions from organic residue applications, as well as avoided emissions (avoided mineral fertilizers). Computation of the nitrogen MFE of organic residues is based on their nitrogen content and composition, and on nitrogen emissions from field applications of the organic residues. Nitrogen field emissions were estimated using simple models and average climate and soil conditions. A global sensitivity analysis revealed that the choice of the application method, which determines the extent of incorporation into the soil, is the main cause of uncertainty in calculated nitrogen MFE values.

Effects of acidification and injection of pasture applied cattle slurry on ammonia losses, N 2 O emissions and crop N uptake

Abstract Surface application of cattle slurry on grassland is characterized by a high risk of ammonia (NH 3 ) losses. Different techniques and measures to lower these emissions are available, but reported abatement efficiencies vary substantially among studies. Therefore, a direct comparison of five different slurry application techniques was conducted in a two year field trial (2012–2013) on perennial grassland in Southern Denmark (sandy soil) and Northern Germany (marsh, clay soil). The techniques included open slot injection of cattle slurry with different distances between double disc injectors (0.166 m injection close, IC; 0.33 m injection wide, IW) and bandspreading of cattle slurry acidified to pH 6.5 (acid low, AL) and 6.0 (acid high, AH) as well as band spreading as reference (BS). For evaluation of N efficiency of slurry treatments, mineral fertilizer equivalents (MFE) were derived by comparison with a mineral N yield response curve. NH 3 emissions were measured with the combination of passive flux sampling and a dynamic chamber method. Nitrous oxide (N 2 O) emissions were determined with a static chamber method at the marsh site. Grass dry matter yield and N yield were determined in all treatments. Ammonia losses were significantly reduced compared to BS treatment by 31, 61, 42 and 79% by IC, IW, AL and AH, respectively. Slurry application techniques had no significant effect on dry matter yield at both study sites. Only treatment AH resulted in higher N uptake among slurry treatments on sandy soil (2012) or clay soil (2013). Except for AH with highest MFE values at Waygaard, MFE values of slurry treatments were higher at sandy soil (53–62%) than at clay soil (39–88%). N 2 O emissions were at a low level in 2012 (0.12–0.38% of N total ) and showed no significant differences among application methods. In 2013, N 2 O emissions were higher (0.07–0.75% of N total ) compared to 2012 and IW resulted in significantly higher emissions than BS. Treatment AH (acidification to pH 6.0) showed lowest NH 3 losses, highest yields while N 2 O emissions were not-significantly increased. Acidification and injection methods proved to reduce NH 3 losses reliably but trade-offs like increased N 2 O emissions from IW and high acid requirement from AH of 4.8 l t −1 slurry have to be taken into consideration.

Efficient Phosphorus Cycling in Food Production: Predicting the Phosphorus Fertilization Effect of Sludge from Chemical Wastewater Treatment.

This study examined the P fertilization effects of 11 sewage sludges obtained from sewage treated with Al and/or Fe salts to remove P by a pot experiment with ryegrass (Lolium multiflorum) and a nutrient-deficient sand-peat mixture. Also it investigated whether fertilization effects could be predicted by chemical sludge characteristics and/or by P extraction. The mineral fertilizer equivalent (MFE) value varied significantly but was low for all sludges. MFE was best predicted by a negative correlation with ox-Al and ox-Fe in sludge, or by a positive correlation with P extracted with 2% citric acid. Ox-Al had a greater negative impact on MFE than ox-Fe, indicating that Fe salts are preferable as a coagulant when aiming to increase the plant availability of P in sludge. The results also indicate that sludge liming after chemical wastewater treatment with Al and/or Fe salts increases the P fertilization effect.

Fertilizer value of phosphorus in different residues

AbstractThe phosphorus (P) fertilizer effect of a range of commonly available manure, waste treatment and by‐product residues was tested in pot, field and incubation experiments. The effect of the residues on P offtake was compared with that of commercial mineral P (super phosphate) to calculate the mineral fertilizer equivalent (MFE). Possible relationships between MFE and P extractable from residues using different agents (ammonium lactate, citrate, water) were examined. Dry matter yield and P concentration were measured in ryegrass grown in pots amended with 14 different residues. The effect on the first cut (after 5 weeks) was significantly higher for residues with a low organic matter content, for example ash and biogas residues (MFE = 74–85%), than for many other products with higher organic matter content, for example meat meal (MFE = 44%), cattle slurry (MFE = 57%) and sewage sludge (MFE = 0–37%). However, the effect on two combined cuts (after 11 weeks) was more similar between residues (MFE = 40–60% for most residues). Ammonium lactate‐extractable P (P‐AL) in residues correlated better with MFE (r2 = 0.48) than water‐extractable or citrate‐extractable P. Grain yield and P concentration were measured in a field experiment with spring wheat fertilized with four different residues. Pelleted meat meal had a similar effect on yield and P offtake as mineral fertilizer P, whereas two different sewage sludge and chicken manure had approximately 50% of the mineral fertilizer effect. The effect of residues on soil P‐AL (the Swedish measure of easily available soil P) in the incubation experiment showed no correlation with MFE from the pot experiments.

Lowland Rice Yield as Affected by Straw Incorporation and Inorganic Fertilizer Over Cropping Seasons in Fluvisol

Grain yield stabilization of lowland rice over cropping seasons was explored using different compositions of inorganic fertilizers (NPK, NPKCa, NPKMg, NPKZn, NPKCaMg, NPKCaZn and NPKCaMgZn) and straw incorporation (3, 6, 9, 12 and 15 tha-1 ). No fertilizer and no straw amended plot was the control in a split-plot design with three replications laid in a Fluvisol of Guinea savanna in Centre Cote d’Ivoire. Three weeks old nursery rice variety NERICA L19 was transplanted. No significant difference of grain yield was observed between the different treatments excluding the highest yields recorded for treatments NPKMg (5.09 tha-1 ), NPKZn (5.15 tha-1 ) and NPKCaéMg (5.31 tha-1 ) compared with 12 (3.95 tha1 ) and 15 tha-1 (4.14 tha-1 ) as straw rates respectively. Grain yield declining trend was more pronounced for mineral fertilizer treatments showing twice greater depressive effect of cropping cycle compared with the straw especially, for treatments characterized by highest grain yield in the first cropping season and similar grain yields were recorded for both sources of nutrient in the third cropping cycle. Of slowness of nutrients releasing by straw, highest grain yield was expected for this soil amender within a longer period of cultivation whereas, unbalance soil micronutrients should be relevant to studious declining yield under inorganic fertilizer effect. Nevertheless, the straw rate of 12 tha-1 supplying 0.58% of NPK as mineral fertilizer equivalent can be recommended for sustaining lowland rice production in the studied agro-ecosystems unless for three cropping seasons.

CREATING SYNERGIES BETWEEN CONSERVATION AGRICULTURE AND CATTLE PRODUCTION IN CROP–LIVESTOCK FARMS: A STUDY CASE IN THE LAKE ALAOTRA REGION OF MADAGASCAR

SUMMARYConservation agriculture (CA) has been promoted as a strategy to cope with deterioration in soil fertility, but its adoption on smallholder farms in tropical areas remains limited. In Madagascar, livestock production is facing shortages in forage especially during the dry season. The value of cover crops used in CA as livestock feed could be an incentive to make this form of agriculture more acceptable in rural areas. To do so, farmers must find a trade-off between the use of biomass from cover crops for animal production and its maintenance on the soil to meet CA's criteria. In this study, we evaluated the impact of biomass flows (cover crops and manure) between cropping and cattle production in crop–livestock farms in the Lake Alaotra region. Surveys among crop–livestock farmers were used to calculate feed concentrate and mineral fertilizer equivalents. Our results show that on average 42, 22 and 10% of biomass production (dry matter basis) of Brachiaria spp., Stylosanthes guianensis and Vicia villosa, respectively, are used for livestock feeding. The economic benefit in feed concentrate equivalent is between €73 and €723/year per farm. The use of manure contributes, just as CA, to improve soil fertility without using external fertilizing resources. The economic benefit in mineral fertilizer equivalent is between €116 and €2365/year per farm. The integration of CA and livestock production shows, beyond the agronomic advantages, an obvious economic benefit, which is essential to secure the Malagasy agricultural systems. Moreover, this economic benefit is another argument for the dissemination of CA practices in rural areas.

Effects of short‐term nitrogen supply from livestock manures and cover crops on silage maize production and nitrate leaching

AbstractResource use efficiency requires a correct appreciation of the nitrogen (N) fertilizer replacement value (NFRV, percentage of total N applied) of manures. We assessed the NFRVs of the liquid fraction originating from separated pig slurry (MC), untreated pig slurry (PS), untreated cattle slurry (CS), the solid fraction from separated pig slurry (SF) and solid farmyard manure from cattle (FYM) in two consecutive years in silage maize grown on a sandy soil. Maize yields responded positively to each of these N sources applied at rates up to 150 kg of mineral fertilizer equivalents per ha per year (i.e. NFRV × total N rate). The observed NFRVs, relative to calcium ammonium nitrate fertilizer, amounted to 78% for MC, 82% for PS, 79% for CS, 56% for SF and 34% for FYM when averaged over both years. NFRVs were positively related to the ammonium‐N share in the total N content. Rye cover crop establishment after the harvest of maize reduced nitrate concentrations of the upper groundwater by, on average, 7.5 mg nitrate‐N/L in the first year and 10.9 mg/L in the second year, relative to a bare soil. Regardless of the presence of a cover crop, nitrate concentrations responded positively to the applied rate of effective N (total N × NFRV) but less to postharvest residual soil mineral N.

Fertilization effects of organic waste resources and bottom wood ash: results from a pot experiment

We conducted a pot experiment to study the fertilization effects of four N- and P-rich organic waste resources alone and in combination with K-rich bottom wood ash at two application rates (150 kg N ha–1 + 120 kg K ha–1, 300 kg N ha-1 + 240 kg K ha–1). Plant-available N was the growth-limiting factor. 48–73% of N applied with meat and bone meal (MBM) and composted fish sludge (CFS) was taken up in aboveground biomass, resulting in mineral fertilizer equivalents (MFE%) of 53–81% for N uptake and 61–104% for yield. MFE% of MBM and CFS decreased for increasing application rates. Two industrial composts had weak N fertilization effects and are to be considered soil conditioners rather than fertilizers. Possible P and K fertilization effects of waste resources were masked by the soil’s ability to supply plant-available P and K, but effects on plant-available P and K contents in soil suggest that the waste resources may have positive effects under more nutrient-deficient conditions.

Potential methods for estimating nitrogen fertilizer value of organic residues

AbstractNew organic fertilizers based on waste products are continually being introduced in agriculture. Their nitrogen (N) fertilizer value of their total N and mineral N content varies widely, creating a demand for standardized laboratory methods. This study evaluated some potential methods for estimating the N fertilizer value of different kinds of organic fertilizers. The methods were evaluated against the N fertilizer value obtained from a ryegrass pot experiment. Fifteen fertilizers were tested, including different kinds of manure, powders from meat, bone, blood and feathers, rapeseed cake, lucerne pellets, sewage sludge, biogas residue, vinasse and mussel compost. Mineral fertilizer equivalents (MFE) were calculated as the fraction of total N (MFE) or organic N (MFEorg) out of total N that has the same availability to plants as inorganic N. Mineral N content (% of total N added with organic residue) after 4 weeks of incubation of soil was correlated to MFE (r2 = 0.78), but was on average 17% lower. Warm water‐extractable N, amino acid N and crude fibre analysis all proved to be unsatisfactory as methods for estimating MFE or MFEorg. However, the carbon/nitrogen ratio accurately reflected short‐term plant‐available N through a negative linear relationship (r2 = 0.83) and would thus be a very useful method for estimating MFE, with MFE decreasing by 5% per unit increase in C/N ratio. The results also indicated that the analysis of near infrared reflectance (NIR) spectra can be an even quicker and cheaper method to estimate MFE of organic residues, but this issue requires further research.

Application rate and composting method affect the immediate and residual manure fertilizer value in a maize–rice–rice–maize cropping sequence on a degraded soil in northern Vietnam

A field experiment was carried out in northern Vietnam to investigate the effects of adding different additives [rice (Oriza sativa L.) straw only, or rice straw with added lime, superphosphate (SSP), urea or a mixture of selected microorganism species] on nitrogen (N) losses and nutrient concentrations in manure composts. The composts and fresh manure were applied to a three-crop per year sequence (maize–rice–rice) on a degraded soil (Plinthic Acrisol/Plinthaquult) to investigate the effects of manure type on crop yield, N uptake and fertilizer value. Total N losses during composting with SSP were 20% of initial total N, while with other additives they were 30–35%. With SSP as a compost additive, 65–85% of the initial ammonium-N (NH4-N) in the manure remained in the compost compared with 25% for microorganisms and 30% for lime. Nitrogen uptake efficiency (NUE) of fresh manure was lower than that of composted manure when applied to maize (Zea mays L.), but higher when applied to rice (Oriza sativa L.). The NUE of compost with SSP was generally higher than that of compost with straw only and lime. The mineral fertilizer equivalent (MFE) of manure types for maize decreased in the order: manure composted with SSP > manure composted with straw only and fresh manure > manure composted with lime. For rice, the corresponding order was: fresh manure > manure composted with SSP/microorganisms/urea > manure composted with lime/with straw alone. The MFE was higher when 5 tons manure ha−1 were applied than when 10 tons manure ha−1 were applied throughout the crop sequence. The residual effect of composted manures (determined in a fourth crop, with no manure applied) was generally 50% higher than that of fresh manure after one year of manure and compost application. Thus, addition of SSP during composting improved the field fertilizer value of composted pig manure the most.

A whole-farm assessment of the efficacy of slurry acidification in reducing ammonia emissions

Livestock slurry in animal houses, in manure stores and applied on fields is in Denmark the most important source of ammonia (NH 3) in the atmosphere. The emitted NH 3 is a source of NH 3 and ammonium (NH 4 +) deposition, which causes eutrophication of N-deficient ecosystems and may form NH 4 +-based particles in the air, which are a risk to health. This study examines the reductions in NH 3 emissions from pig houses, manure stores and manure applied in the field achieved by acidifying the slurry in-house. Sulphuric acid was used to acidify pig slurry to pH < 6 and the system was constructed is such a way as to prevent foaming in the animal house as well as during storage. Acidification of the pig slurry reduced the NH 3 emission from pig houses by 70% compared with standard techniques. Acidification reduced NH 3 emission from stored slurry to less than 10% of the emission from untreated slurry, and the NH 3 emission from applied slurry was reduced by 67%. The mineral fertilizer equivalent (MFE) of acidified slurry was 43% higher compared with the MFE of untreated slurry when applied to the soil. The odour emission from the slurry was not affected significantly by the treatment. The slurry acidification system is approved Best Available Technology (BAT) in Denmark.

Effects of different diets on utilization of nitrogen from cattle slurry applied to grassland on a sandy soil in The Netherlands

Dietary adjustments have been suggested as a means to reduce N losses from dairy systems. Differences in fertilizing value of dairy slurry as a result of dietary adjustments were evaluated in a 1-year grassland experiment and by long-term modelling. Slurry composition of non-lactating dairy cows was manipulated by feeding diets with extreme high and low levels of dietary protein and energy. C:Ntotal ratio of the produced slurries ranged from 5.1 to 11.4. To evaluate their short-term fertilizer N value, the experimental slurries (n = 8) and slurries from commercial farms with variable composition (n = 4), were slit-injected in two grassland fields on the same sandy soil series in the north of The Netherlands (53°10?N, 6°04?E), with differences in sward age and ground water level. The recently established grassland field (NEW) was characterized by lower soil OM, N and moisture contents, less herbs and more modern grass varieties compared to the older grassland field (OLD). Slurry was applied in spring (100 kg N ha?1) and after the first cut (80 kg N ha?1) while in total four cuts were harvested. Artificial fertilizer N treatments were included in the experiment to calculate the mineral fertilizer equivalent (MFE) of slurry N. The OLD field showed a higher total N uptake whereas DM yields were similar for the two fields. Average MFE of the slurries on the OLD field (47%) was lower than on the NEW field (56%), probably as a result of denitrification of slurry N during wet conditions in spring. Slurries from high crude protein diets showed a significantly higher MFE (P <0.05) compared to low crude protein diets. No significant differences in MFE were observed between slurries from high and low energy diets. On both fields, MFE appeared to be positively related to the ammonium content (P <0.001) and negatively to the C:Ntotal ratio of the slurry DM (P = 0.001). Simulation of the effect of long-term annual application of 180 kg N ha?1 with highest and lowest C:Ntotal ratio suggested that both slurries would lead to an increase in annual soil N mineralization. Both soil N mineralization and SOC appeared to be substantially higher in equilibrium state for the slurry with the highest C:Ntotal ratio. It is concluded that in a situation with slit-injection, the reduced first-year N availability of slurry with a high C:Ntotal ratio as observed in the grassland experiment will only be compensated for by soil N mineralization on the very long term.

Short‐term and residual availability of nitrogen after long‐term application of organic fertilizers on arable land

AbstractKnowledge on short‐term and long‐term availability of nitrogen (N) after application of organic fertilizers (e.g., farmyard manure, slurry, sewage sludge, composts) provides an important basis to optimize fertilizer use with benefits for the farmer and the environment. Nitrogen from many organic fertilizers often shows little effect on crop growth in the year of application, because of the slow‐release characteristics of organically bound N. Furthermore, N immobilization after application can occur, leading to an enrichment of the soil N pool. However, this process finally increases the long‐term efficiency of organic fertilizers. Short‐term N release from organic fertilizers, measured as mineral‐fertilizer equivalents (MFE), varies greatly from 0% (some composts) to nearly 100% (urine). The most important indicators to be used for predicting the short‐term availability of N are total and NH$ _4^+ $‐N contents, C : N ratio (especially of the decomposable organic fraction), and stability of the organic substances. Processing steps before organic fertilizers are applied in the field particularly can influence N availability. Composting reduces mineral‐N content and increases the stability of the organic matter, whereas anaerobic fermentation increases NH$ _4^+ $‐N content as well as the stability of organic matter, but decreases the C : N ratio remarkably, resulting in a product with a high content of directly available N. Nevertheless, long‐term effects of organic fertilizers rather slowly releasing N have to be considered to enable optimization of fertilizer use. After long‐term application of organic fertilizers, the overall N‐use efficiency is adequate to a MFE in the range of 40%–70%.

Dietary effects on the composition and plant utilization of nitrogen in dairy cattle manure

The influence of dairy cattle feed composition on the manure composition and on the dynamics and plant availability of cattle slurry N was studied. Dairy cows were fed seven different forages either with or without supplemental concentrates. The concentration of N in faeces dry matter varied from 18 to 38 g/kg dry matter and increased with increasing digestibility of the feed. Cattle slurries consisting of a mixture of 0·5 faecal N and 0·5 urinary N were stored according to common agricultural practice in Northern Europe. The mineralization of faecal N during slurry storage was very variable (0·09–0·50). The plant availability of N in the slurries originating from cattle fed with known diets was tested in small, framed field plots with spring barley, under conditions with minimal N losses. The nitrogen uptake in barley was determined and the mineral fertilizer equivalent (MFE) of slurry N was calculated. The net release of mineral N and CO2 from the slurries in soil was also measured in a parallel incubation study. The MFE of cattle slurry N varied from 53 to 75%. After correcting for the measured urine-N/faeces-N ratio and expected ammonia emission, the MFE varied from 51 to 78%. The plant availability and net release of cattle slurry N were influenced by forage type and feeding level. The MFE was negatively correlated with the concentration of crude fibre and neutral detergent fibre (NDF) in the diet, and positively correlated with the dietary protein content. The net release of CO2 from the slurries after 12 weeks in soil was significantly influenced by the concentration of crude fibre in the diet. The plant availability of slurry N was significantly correlated with the ammonium content (R2=0·53) and negatively correlated with the slurry C[ratio ]N ratio (R2=0·67) and the dry matter[ratio ]N ratio (R2=0·58). Residual slurry N left in the soil after harvest of the first crop varied from 0·25 to 0·47 of total slurry N. It is concluded that the fibre and the protein content of cattle diets have a significant influence on the plant availability of cattle slurry N and on the amount of residual slurry N remaining in the soil after the first growing season.

Dietary effects on the composition of pig slurry and on the plant utilization of pig slurry nitrogen

The composition of animal manure is influenced by the diet fed. Efforts are made to decrease nitrogen emission from pig production by optimizing diet composition. This normally results in a lower proportion of N excreted in urine relative to faeces, and may also influence the turnover and utilization of manure N after field application. The effects of pig feed composition on the excretion of urinary and faecal N, on the dynamics of manure N in soil and on the potential utilization of manure N in the field was studied. Growing pigs and sows were fed 12 different diets with variable contents of fibre and protein (with or without synthetic amino acids). Slurries consisting of a mixture of faeces and urine were stored according to common agricultural practice in Northern Europe. The plant availability of N in the resultant slurries originating from animals fed known diets was tested in small field plots with barley, under conditions with minimal N losses. Separate plots were fertilized with increasing amounts of mineral N. Nitrogen uptake in barley was determined and the utilization of slurry N was compared with that of mineral fertilizer N. The net release of mineral N and C from the slurries in soil was also measured in a parallel incubation study.The mineral fertilizer equivalent of pig slurry N was 72–100% and significantly influenced by feed fibre composition, but not significantly influenced by the protein content. There was a significant positive correlation between enzyme-digestible organic matter in the pig diet (measurement used for feed evaluation) and the plant availability of pig slurry N (R2=0·90). The ammonium content of stored pig slurry could not be used for prediction of the N availability since the net mineralization of pig slurry N was variable, but there was a significant negative correlation between the pig slurry C/N ratio and the plant availability of slurry N (R2=0·86).Increased dietary concentration of fermentable structural carbohydrates (e.g. by including sugar beet pulp in the diet) reduces the excretion of N in urine without affecting the availability of slurry total N, whereas an increased concentration of dietary fibre with a low fermentability (straw) results in less urinary N, but also a lower plant availability of slurry N.

The influence of surface and sub‐surface application methods for pig slurry on herbage yields and nitrogen recovery

AbstractExperiments were conducted on a grassland site at Wrest Park, Silsoe, Bedfordshire between 1987 and 1989, to compare herbage yields from slurry applied by deep and shallow injection, low trajectory and conventional vacuum tanker methods. Slurry application rates for all spreaders were calibrated at 86 ± 5 t ha‐1, an equivalent of c. 200 kg NH4+‐N ha‐1 applied in autumn or in spring.As expected, herbage yields following spring applications were higher than from autumn applications, with average mineral fertilizer equivalents of 122 and 89 kg N ha‐1 respectively. Yields from the conventional and low trajectory spreaders showed no consistent differences. However, in both years, first cut yields from plots were significantly lower (P &lt; 0·05) where slurry had been injected than where surface applications had been used by an average of 0·7 t DM ha‐1. Subsequent cuts in 1988 demonstrated higher residual effects from injection so that annual total yields were similar from all slurry applications irrespective of spreader type.Analysis of N content revealed high N levels in herbage from deep injection plots. Mean concentrations of N in the herbage, expressed as a percentage of the dry matter, were 1·43 for surface treatments and 1·79 for deep injection in 1988, and 1·84 for surface treatments, 2·13 for shallow injection and 2·68 for deep injection in 1989.