Fungal and bacterial growth following the application of slurry and anaerobic digestate of livestock manure to temperate pasture soils

How land-application of digestate sourced from anaerobic digestion (AD) of animal waste influences the functioning of a mixed pasture agroecosystem is not well characterised, particularly with regard to the response of the actively growing microbial community. We studied the impact of the liquid AD digestate on the decomposer community in two different soils, seeded with two different common grassland crops; a mixture of either grass or grass/clover in a greenhouse experiment. We studied bacterial (leucine incorporation into bacteria) and fungal (acetate incorporation into ergosterol) growth responses to AD cattle slurry digestate, undigested cattle slurry, mineral fertiliser (NPK and N) added at a rate equivalent to 150?kg?N?ha^?1, and a no-fertiliser control treatment. Differences in fungal and bacterial growth were evident between the soil and sward types. However, the fertilisers consistently stimulated a higher bacterial growth than the no-fertiliser control, and liquid digestate resulted in a level of bacterial growth higher or equal to that of mineral fertiliser, whilst undigested slurry resulted in lower bacterial growth. These fertiliser effects on bacterial growth mirrored the effects on plant growth. In contrast, the fungal community responded only marginally to fertiliser treatments. We conclude that the application of digestate stimulates the bacterial decomposer community in a similar way to that of mineral fertilisers. Our results suggest that mineral fertiliser can be exchanged for liquid digestate with limited impact on the actively growing soil microbial community that, in turn, regulate important soil processes including nutrient cycling in agricultural soils.     

Nitrogen and phosphorus in runoff from grassland with buffer strips following application of fertilizers and manures

Abstract. We examined whether nitrogen (N) and phosphorus (P) export was enhanced from grassland receiving inorganic fertilizer and manures typical of intensive livestock production. Buffer strips were included in the study to determine if they could reduce nutrient export. Hillslope plots receiving granular inorganic fertilizer, liquid cattle slurry and solid cattle manure (FYM) were compared using rainfall simulation for 4 storms on consecutive days at 22 mm h^-1 and 35 minutes duration. The plots were hydrologically isolated in a randomized block layout of 4 treatments × 3 replicates and measured 30 × 5m; the upper 20m received either fertilizer, slurry or FYM, while the lower 10 m acted as an unfertilized grass buffer strip. Nitrogen and P export in surface runoff from grassland receiving inorganic fertilizer exceeded that from FYM or slurry treatments; concentrations up to46mgN1-^-1 and 15 mgP1^–1 were recorded.
Sixty eight % and 62% of the N from FYM and slurry respectively, was exported in organic form. Seventy four % (FYM) and 39% (slurry) of the P was in particulate or dissolved organic form. The buffer strip reduced N export in surface runoff by 94% and P export by 98% from inorganic fertilizer plots. A 75% reduction in N export was recorded from the buffer zone below slurry plots but only a 10% reduction in P, with most P remaining in the particulate or dissolved organic fraction. There was no significant difference in N export from the buffer zone between the inorganic fertilizer treatment and the untreated control.     

Aeration improves the hygiene of cattle slurry and the quality of grass forage and silage†

The aeration of slurry at mesophilic temperature improves its hygiene, provided no fresh slurry is added to the tank during the 3–4 weeks of aeration. Microorganisms, such as Listeria monocytogenes, Yersinia enterocolitica and related species and coliphages, were reduced by 90–99.9%. However, the number of Clostridium was not affected. The typical odour of slurry diminished. The use of aerated slurry as fertilizer on growing grass may cause less risk of contamination either by enteric microorganisms or by butyric acid‐producing clostridia than the use of non‐aerated slurry. The hygiene level of grass was also sufficient when grown in a cold, rainy late summer and used for silage. None of the 62 samples of silage prepared from a second‐harvest grown in rainy conditions and fertilized with aerated slurry were found to have deteriorated. However, three samples out of 63 made during the same period but fertilized with non‐aerated slurry were observed to have deteriorated completely. Neither spreading method, band‐spreading or injection of the slurry into sward, had any effect on the microbiological hygiene of the samples.     

Anaerobic co‐digestion of perennials: Methane potential and digestate nitrogen fertilizer value

Co‐digestion of crop biomass improves the traditional manure‐based biogas yield due to an increased content of easily degradable carbon compounds. In this study, the methane potential of three perennials (grass, legumes, and grass+legume) was determined using various amounts together with animal manure. The nitrogen (N) mineralization dynamics in soil and the N‐fertilizer value of the derived digestates were subsequently tested in both a soil incubation study and a pot experiment with spring barley. Digestion of all tested perennials together with a manure‐based inoculum increased the cumulative methane yield four to five times compared to digestion of the inoculum alone, with the highest increases observed with pure grass. However, the methane potential decreased along with increasing grass biomass concentration. In the plant pot experiment, all tested digestates increased barley shoot biomass by 40–170%, to an extent statistically comparable to mineral N fertilizer. However, the application of the digestate originating from fermentation with pure grass resulted in lower plant growth and a more fluctuating soil mineral N content throughout the incubation study compared to the other digestates. Considering the high dry matter and methane yield ha^?1, the possibility to substitute mineral N fertilizer inputs by leguminous biological N₂ fixation capacity, and the digestate fertilizer value, the integration of grass–legume mixtures or sole legumes into anaerobic digestion systems as co‐substrate for manure seems to be promising. This could furthermore contribute to the diversification of cropping systems for bioenergy production.     

Soil biological quality of grassland fertilized with adjusted cattle manure slurries in comparison with organic and inorganic fertilizers

We studied the effect of five fertilizers (including two adjusted manure slurries) and an untreated control on soil biota and explored the effect on the ecosystem services they provided. Our results suggest that the available N (NO₃⁻ and NH₄⁺) in the soil plays a central role in the effect of fertilizers on nematodes and microorganisms. Microorganisms are affected directly through nutrient availability and indirectly through grass root mass. Nematodes are affected indirectly through microbial biomass and grass root mass. A lower amount of available N in the treatment with inorganic fertilizer was linked to a higher root mass and a higher abundance and proportion of herbivorous nematodes. A higher amount of available N in the organic fertilizer treatments resulted in a twofold higher bacterial activity (measured as bacterial growth rate, viz. thymidine incorporation), a higher proportion of bacterivorous nematodes, a 30% higher potential N mineralization (aerobic incubation), and 25–50% more potentially mineralizable N (anaerobic incubation). Compared to inorganic fertilizer, organic fertilization increased the C total, the N total, the activity of decomposers, and the supply of nutrients via the soil food web. Within the group of organic fertilizers, there was no significant difference in C total, abundances of soil biota, and the potential N mineralization rate. There were no indications that farmyard manure or the adjusted manure slurries provided the ecosystem service “supply of nutrients” better than normal manure slurry. Normal manure slurry provided the highest bacterial activity and the highest amount of mineralizable N and it was the only fertilizer resulting in a positive trend in grass yield over the years 2000–2005. The number of earthworm burrows was higher in the treatments with organic fertilizers compared to the one with the inorganic fertilizer, which suggests that organic fertilizers stimulate the ecosystem service of water regulation more than inorganic fertilizer. The trend towards higher epigeic earthworm numbers with application of farmyard manure and one of the adjusted manure slurries, combined with the negative relation between epigeic earthworms and bulk density and a significantly lower penetration resistance in the same fertilizer types, is preliminary evidence that these two organic fertilizer types contribute more to the service of soil structure maintenance than inorganic fertilizer.     

Biogas digestates based on lignin-rich feedstock – potential as fertilizer and soil amendment

With advances in biogas technology, lignocellulosic material may be increasingly included in feedstock due to the abundance of raw materials. The main goal of this study was to evaluate fertilizing and soil amendment effects of digestates based on lignin-rich feedstock. The digestates originated from reactors fed with manure co-digested with Salix, wheat straw or sugarcane bagasse, respectively. In pot experiments with three different soils, Italian ryegrass and reed canary grass were grown with 120 kg ha^?1 total nitrogen or 150 kg ha^?1 available nitrogen, respectively, given as either mineral fertilizer or digestate. Soil chemical and physical characteristics were determined after ended experiments. Additionally, an incubation study was carried out to estimate N mineralization from one digestate over time. Digestate addition resulted in similar yields compared to mineral fertilizer, varying from 0.5 (loam) to 1 kg dry matter m^?2 (silt) for Italian ryegrass and 1.2 (loam) to 2.3 kg m^?2 (silt) for reed canary grass. Digestates contributed to a favourable pH for plant growth, reduced bulk density in the loam and improved water retention characteristics in the sand. Biogas digestates based on lignin-rich feedstock appear promising as fertilizers and for soil amelioration but results have to be verified in field experiments.     

Effects of Anaerobic Digestate on Chinese Melon (Cucumis melo L.) Yield Components,Soil Properties,and Microbial Communities under Saline Irrigation Condition

ABSTRACT

Digestate is increasingly utilized as a fertilizer, and earlier research was dedicated to plant growth and soil properties, with simple little information available regarding the effects of digestate on soil, plant, and microbial communities under saline irrigation. For this reason, a pot experiment with Chinese melon was conducted in a greenhouse, and digestate (1100 L ha^?1) and a full recommended dose of NPK fertilizer were used. The melons were irrigated with normal water 0.25 (SL0) and 2 dS/m (SL1) using sodium chloride (NaCl). Application of digestate increased the melon plant height and leaves number significantly (p < 0.05) compared to control and treatments that received full NPK dose, under both water treatments (SL0 and SL1). The maximum plant height (SL0: 161 cm and SL1: 85.5 cm) and leaves number (SL0: 156.33 and SL1: 69.67) were observed when digestate used with NPK fertilizer. Plant fruit length, fruit diameter, sugar content, and yield increased significantly by digestate addition. The melon fruit sugar content values were 12% (SL0) and 9.83% (SL1). Soil electrical conductivity values increased when digestate combined with NPK fertilizer (1.4 dS m^?1) particularly, under saline water, while the soil pH is not affected by digestate treatments. Digestate increased bacteria and decreased the number of fungi in the soil. Our results indicated that the usage of digestate could be more effective than NPK fertilizer on plant growth and soil properties. And there is a need to confirm these results in soils more realistic for agricultural field conditions and pay attention to use of digestate with saline irrigation water.     

Does acidification increase the nitrogen fertilizer replacement value of bio‐based fertilizers?

Acidification of manure, digestate and their processed derivatives has been proposed as a technique to, amongst others, mitigate ammonia emissions related to application in the field. The current study investigated whether acidification of (1) pig slurry (PS), (2) liquid fraction of pig slurry (LFPS), (3) digestate (DIG), and (4) liquid fraction of digestate (LFDIG) increases their nitrogen (N) fertilizer replacement value (NFRV) as compared to non‐acidified counterparts, a synthetic N fertilizer (calcium ammonium nitrate; CAN) and an unfertilized control. Product performance was evaluated from the perspective of (1) crop development (yield, nutrient uptake, and crop quality assessment) via a pot experiment with Lactuca sativa L. and (2) soil N dynamics [net N release (N_rel,net) and net N mineralization] via a soil incubation experiment. Crop yield of pots receiving bio‐based fertilizers performed ‘on par' with CAN as compared to unfertilized control, implying that bio‐based fertilizers derived from digestate or manure could potentially play a role in replacing synthetic N fertilizers. However, our findings also suggest that acidification did not result in an increased use efficiency of applied N. NFRVs of acidified products were below those of non‐acidified products and CAN, with crop yield on average 6–13% and 11–18% lower compared to non‐acidified products and the CAN treatment, respectively. A possible explanation for lower performance as compared to non‐acidified products could be an inhibitory delay in the N_rel,net, which in our experimental design proved to be negative for crops with short production cycles. This pattern was revealed in the incubation experiments in which N_rel,net in acidified products remained below that of non‐acidified, in this study tentatively attributed to immobilization of mineral N. However, this negative effect on N availability should be reaffirmed in crops with longer production cycles. Finally, some interesting findings with regard to plant composition also warrant further in‐depth investigation, e.g ., Zn uptake by lettuce in acidified treatments was significantly higher than that of non‐acidified treatments. This implies that product pre‐treatment may play a future role in biofortification and amelioration of (trace) element composition of crops (arguably for crops with longer production cycles). Improving crop nutritional value by increased uptake of micronutrients is receiving increasing attention.     

Effect of the nitrification inhibitor DMPP on nitrous oxide emissions and the stabilization of ammonium following the injection of dairy slurry and digestate in a soil‐column experiment

Injection of slurry or digestate below maize seeds is a relatively new technique developed to improve nitrogen use efficiency. However, this practice has the major drawback of increasing nitrous oxide (N₂O) emissions. The application of a nitrification inhibitor (NI) is an effective method to reduce these emissions. To evaluate the effect of the NI 3,4‐dimethypyrazole phosphate (DMPP) on N₂O emissions and the stabilization of ammonium, a two‐factorial soil‐column experiment was conducted. PVC pipes (20 cm diameter and 30 cm length) were used as incubation vessels for the soil‐columns. The trial consisted of four treatments in a randomized block design with four replications: slurry injection, slurry injection + DMPP, digestate injection, and digestate injection + DMPP. During the 47‐day incubation period, N₂O fluxes were measured twice a week and cumulated by linear interpolation of the gas‐fluxes of consecutive measurement dates. After completion of the gas flux measurement, concentration of ammonium and nitrate within the soil‐columns was determined. DMPP delayed the conversion of ammonium within the manure injection zone significantly. This effect was considerably more pronounced in treatment digestate + NI than in treatment slurry + NI. Regarding the cumulated N₂O emissions, no difference between slurry and digestate treatments was determined. DMPP reduced the release of N₂O significantly. Transferring the results into practice, the use of DMPP is a promising way to reduce greenhouse gas emissions and nitrate leaching, following the injection of slurry or digestate.     

Yield and Performance and Soil Properties of Organically Fertilized Fodder Crops

The aim of this study was to evaluate the effects of experimental amendments on yields of Trifolium subterraneum L., Pisum arvense L., and Lolium multiflorum Lam., and on soil characteristics. A two-year research was carried out comparing anaerobic digestate (AD) and olive-pomace compost (OPC) with mineral fertilizer (Min), commercial organic-mineral fertilizer (Org-min), and unfertilized control (Cont). Anaerobic digestate and OPC were firstly analyzed for their chemical characteristics. The most important parameters were recorded and soil properties were investigated. Anaerobic digestate showed the highest dry weight for ryegrass, the best yield in pea, and good level of dry matter in clover. Good responses were achieved by OPC. Anaerobic digestate increased total soil organic carbon by 14.4, 8.1 and 7.6% than Min, Org-min and Cont, respectively. Olive-pomace compost increased the same parameter by 16.3, 10.0, and 9.5%. The findings indicated the possibility to substitute mineral fertilizers with organic ones without decreasing yields and support soil fertility.     

土壤添加沼渣对温室气体排放及小麦生长的影响

Digestate, the product obtained after anaerobic digestion of organic waste for biogas production, is rich in plant nutrients and might be used to fertilize crops. Wheat(Triticum spp. L.) was fertilized with digestate, urea, or left unfertilized and cultivated in the greenhouse for 120 d. Emissions of greenhouse gasses(carbon dioxide(CO_2), methane(CH_4), and nitrous oxide(N_2O)) were monitored and plant growth characteristics were determined at harvest. The digestate was characterized for heavy metals, pathogens, and C and N mineralization potential in an aerobic incubation experiment. No Salmonella spp., Shigella spp., or viable eggs of helminths were detected in the digested pig slurry, but the number of faecal coliforms was as high as 3.6 × 10~4colony-forming units(CFU) g-~(1)dry digestate. The concentrations of heavy metals did not surpass the upper limits established by US Environmental Protection Agency(EPA). After 28 d, 17% of the organic C(436 g kg~(-1)dry digestate) and 8% of the organic N(6.92 g kg~(-1)dry digestate)were mineralized. Emissions of CO_2 and CH_4 were not significantly affected by fertilization in the wheat-cultivated soil, but digestate significantly increased the cumulative N_2O emission by 5 times compared to the urea-amended soil and 63 times compared to the uncultivated unfertilized soil. It could be concluded that digestate was nutrient rich and low in heavy metals and pathogens, and did not affect emissions of CH_4 and CO_2 when applied to a soil cultivated with wheat, but increased emission of N_2O.     

Use of digestate as an alternative to mineral fertilizer: effects on growth and crop quality

Nowadays, the recycling of organic wastes represents a key factor for improving soil and crop quality with socio-economic and environmental benefits. In recent years, the production of digestate significantly increased with a crescent need to be sustainable disposal. The use of digestate as soil amendment has been widely studied but few researches evaluated the digestate effects on crop quality. Since it has been proven that digestate increased soil fertility, we hypothesized that it could increase crop quality as organic fertilizers do. To verify this hypothesis, we analyzed the effects of two digestates on Cucumber quality. Cucumber was chosen because it is an important old crop used worldwide as fresh food, and in cosmetic and pharmaceutic industries. Results showed that digestates increased its content of phenols and flavonoids with antioxidant activity. Neohesperidine and hesperitin with well-known antioxidant, anti-inflammatory and anti-carcinogenic properties as well as naringin and narirutin with the power of reducing the risk of atherosclerosis and cardiovascular complications were manifested only in digestate amended cucumbers. These results highlighted the potentiality of digestates not only as crop growth promoter but also as phytochemical inducers representing a good option for the production of high-quality food with reduced chemical mineral fertilizer inputs.     

不同有机物及其堆肥与化肥配施对小麦生长及氮素吸收的影响

采用15N示踪技术,选用水稻土和灰潮土在宜兴进行小麦盆栽试验,研究了稻草、猪粪及其堆肥与化肥配施对作物生长及氮素吸收的影响。结果表明,在水稻土和灰潮土上,不同有机物及其堆肥与化肥配施分别比单施化肥增产4.46%～24.82%和1.01%～20.53%,稻草堆肥和猪粪堆肥配施化肥处理籽粒产量分别高于稻草和猪粪直接与化肥配施处理。稻草和猪粪堆肥后更利于作物吸收氮素,增加植物体内15N累积。两种土壤上15N回收率表现为相同配比的堆肥处理未堆肥处理单施化肥处理。随着小麦生育期的推进,土壤微生物量氮和矿质态氮含量均呈下降趋势,稻草和猪粪处理的微生量氮含量始终高于稻草堆肥和猪粪堆肥处理。有机无机肥配施处理土壤矿质态氮在小麦生育前期低于单施化肥,成熟期则高于单施化肥。整个生育期中,稻草堆肥和猪粪堆肥处理土壤矿质态氮含量分别高于稻草和猪粪处理。因此,有机物堆肥后与化肥配施更有利于提高产量,促进作物对氮素的吸收利用。     

Nitrogen transfer from warm‐season annual legumes to pearl millet

A glasshouse study was conducted to determine and quantify direct transfer of nitrogen (N) between 3 selected warm‐season annual legumes and a warm‐season annual grass during the growing season, ‘Tifleaf’ pearl millet [Pennisetum americanum (L.) Leeke] was grown in pots as a monoculture with and without N applied as inorganic fertilizer, or with either ‘Iron and Clay’ cowpeas [Vigna unguiculata (L.) Walp], common alyceclover [Alysicarpus vaginalis (L.) DC.], or ‘Comanche’ partridge pea (Cassia fasciculata Michx.). Sixty‐three percent of the N contained in pearl millet grown with alyceclover was derived directly from alyceclover as determined by the ¹⁵N dilution technique. Partridge peas and cowpeas transferred 34% and 32%, respectively, of the N contained in companion pearl millet plants. Pearl millet grown with partridge peas produced dry matter yields similar to pearl millet that received the equivalent of 112 kg N/ha. Pearl millet grown with legumes contained lower levels of neutral detergent fiber than did pearl millet that received inorganic fertilizer. Nitrogen content of pearl millet grown with legumes was not as great as pearl millet that received N‐fertilizer.     

Application of Fresh and Treated Pig Slurries and a Novel Organic-Mineral Fertilizer in Maize Crop

Lysimeter experiments were carried out during two growing seasons to compare the effect of untreated, digested, codigested, and a novel organic-mineral fertilizer, synthesized with pig slurry by a new-generation technology, on nitrogen (N) and phosphorus (P) leaching when compared with mineral fertilizer at typical rates for maize (Zea mays L.) production in Mediterranean soil. Relationships between application rates and type of fertilizer on maize crop yield, N uptake, and N and P leaching were investigated to assess the efficacy of these fertilizers in Mediterranean areas. Results showed a positive effect of the use of treated slurries, high N uptake of maize plants, and dry-matter production that was crucial for keeping N leaching loads at minimum. Then, not only in terms of production, but also in terms of N conservation in soil and in environmental water quality, slurries showed a better performance than inorganic or the organic-mineral fertilizer.     

A mixture of grass and clover combines the positive effects of both plant species on selected soil biota

The introduction of N₂-fixing white clover (Trifolium repens) in grassland is a management measure that may contribute to sustainable grassland systems by making them less dependent on inorganic fertilizers. However, little is known about the impact of this measure on soil biota and ecosystem services. We investigated earthworms, nematodes, bacteria and fungi in an experiment in which white clover-only and a mixture of grass and white clover without fertilization were compared with grass-only with and without fertilization.In comparison with grass-only, white clover-only had a lower total root biomass and a lower C/N-ratio in the above- and below-ground plant biomass. These plant characteristics resulted in a lower bacterial biomass, a lower fungal biomass, a higher proportion of bacterivorous nematode dauerlarvae, a lesser proportion of herbivorous nematodes and a greater abundance of earthworms in clover-only.The quantity and quality (C/N-ratio) of the above- and below-ground plant biomass in the mixture of grass and white clover (20–30% clover in the DM) was comparable with grass fertilized with 150 kg N ha⁻¹ of inorganic fertilizer. Differences between these treatments might show specific clover effects in the grass–clover mixture on soil biota other than quantity and C/N-ratio of the litter. However, the only differences were a higher proportion of bacterivorous nematode dauerlarvae and a different nematode community composition in grass–clover.The soil structure in white clover-only showed a higher proportion of angular blocky elements, a lower penetration resistance, a higher number of earthworm burrows, a higher potential N-mineralization and respiration than the soil in grass-only. This suggests that clover stimulates the ecosystem services of water infiltration and supply of nutrients, but is less conducive to soil structure maintenance. The grass–clover mixture differed from grass-only in a higher respiration and from clover-only in a higher percentage of soil crumbs. We suggest that when clover is introduced in grassland to reduce the reliance on inorganic fertilizer, the mixture of grass and clover maintains the positive impact of grass roots on soil structure and increases the supply of nutrients via the soil food web. Thus, a grass–clover mixture combines the agronomic benefits of the two plant types.     

Influence of pool substitution on the interpretation of fertilizer experiments with 15N

The uptake of labelled and unlabelled N by wheat was measured in pot and field experiments with ¹⁵N-labelled fertilizer. Soils from two sites on the same series were used in the pot experiment; one had been bare-fallowed for 22 years and contained 1.6% organic C, the other had been under grass for many years and contained 3.8% organic C. Fertilizer N increased the uptake of unlabelled soil N in both soils, i.e. there was a positive ‘added nitrogen interaction’ (ANI). There was no ANI in the field experiment. A simulation model is used to show how positive ANIs can arise as a result of ‘pool substitution’—labelled inorganic fertilizer N standing proxy for unlabelled inorganic soil N that would otherwise have been immobilized. In the low-organic fallow soil, pool substitution accounted for the whole of the observed ANI and fertilizer N did not enhance either gross or net mineralization of soil N. Pool substitution also operated in the high organic grassland soil, but here net mineralization of soil N increased with increasing additions of fertilizer, giving rise to a ‘real’ ANI in addition to the larger ‘apparent’ ANI caused by pool substitution. This increase in net mineralization is probably caused by a decrease in immobilization of N as fertilizer N additions increase, not by an increase in gross mineralization of soil N. For pool substitution to operate, fertilizer N and soil inorganic N must occupy the same pool. This occurred in the pot experiment but not in the field experiment, where fertilizer and soil inorganic N remained separate and there was no ANI. When pool substitution occurs, fertilizer use efficiency is predictably lower as measured by the isotopic method than as measured by the conventional non-isotopic procedure.     

Hydro-/Biochar application to sandy soils: impact on yield components and nutrients of spring wheat in pots

From hydro-/biochar application to soils positive effects on soil characteristics and as a consequence on yield of crops were expected. The objective of this study was to compare the effects of maize biochar and maize hydrochar (HTC-char) amendments treated with or without digestate, as well as a wood biochar, mixed with or without digestate and mineral nitrogen fertilizer on yield, yield components, nutrient contents and quality of spring wheat. Therefore, a pot experiment was set up. Yield, yield components and quality were mainly influenced by nitrogen fertilizer. The application of HTC-char could have negative effects on yield and yield components of spring wheat. Hydrochar treated with digestate had no negative effects on yield of spring wheat.     

Application technique affects the potential of mineral concentrates from livestock manure to replace inorganic nitrogen fertilizer

It has been suggested that mineral concentrates (MCs) produced from livestock manure might partly replace inorganic N fertilizers, thereby further closing the nitrogen (N) cycle. Here, we quantified nitrogen use efficiency (NUE) and N loss pathways associated with MCs, compared with inorganic fertilizer and manure. In a 26‐day greenhouse experiment with ryegrass (Lolium perenne L.), the effects of application technique (surface application vs. injection) and N source (control, two types of MC, three inorganic fertilizers or pig slurry) were compared. We measured yield, ammonia volatilization, nitrous oxide emission and denitrification. With surface application, NUE for MCs (38% for MC1 and 22% for MC2) was significantly lower than for calcium ammonium nitrate (CAN; 61%) and comparable with PS (25%). This was most likely due to higher ammonia emissions. After injection, the NUE of MC was comparable with that of CAN. Denitrification and N₂O emission from surface‐applied MC were comparable with those from surface‐applied PS. After injection, MC behaved similarly to inorganic fertilizers. We conclude that MCs should be injected to maximize NUE and to fulfil their potential as inorganic fertilizer replacement. Significant NUE differences between MCs suggest the possibility for further optimization of the MC production process.     

动物粪便营养成分含量的估算

该文通过大量数据统计分析提出，不同种类动物粪便需用不同的预测方程估算其中的养分含量，粪便的导电性和干物质含量是准确估算其中氮、磷、钾养分含量的重要参数；以上两个参数为自变量的二元回归方程可更准确地估算出粪便中的养分含量