Nitrogen mineralization from digestate in comparison to sewage sludge,compost and urea in a laboratory incubated soil experiment

This paper evaluated, in a laboratory incubated soil, the properties of digestate as a nitrogen fertilizer in comparison with sewage sludge, compost and urea, this last as a typical mineral fertilizer. The incubation period lasted for 90 d and during this time, pH, CO₂ and evolution were measured. The maximum concentration of nitrate was reached in the incubated microcosm fertilized by urea (133 mg kg⁻¹ after 62 d), and that of digestate was very similar (113 mg kg⁻¹). Soil treated with compost showed a slower nitrate evolution. A significantly negative correlation was detected between cumulative nitrogen nitrified at the end of the trial, and the values of the C:N ratio of the biomasses used (compost, sludge and digestate) (mg kg⁻¹ vs . C:N, r = –0.94, n = 3, p < 0.05), and between the alkyl‐C content at the end of the experiment (mg kg⁻¹ vs . alkyl‐C, r = –0.95, n = 3, p < 0.05). As expected, pH decreases and soil respiration (CO₂ evolution) were also well correlated with the content of nitrate. Considering that about 90% of the nitrogen content in the digestate is short acting, the results obtained indicate that the nitrogen rate of mineralization in digestate is very similar to that of urea, confirming that digestate could replace traditional mineral fertilizers.     

连续闭式循环氨脱除工艺响应面法优化

针对两阶段闭式循环氨脱除工艺处理猪粪厌氧消化液耗时、耗碱、难以达到工业化大量污水处理的需求问题,进行了连续闭式循环氨脱除工艺的试验研究。试验结果表明,对于起始氨氮质量浓度为(1 444±37)mg/L的猪粪厌氧消化液,在气流量为530 L/h、液流量为445 m L/h、气液比为2 036条件下,氨氮脱除率可达(66.81±0.24)%。经RSM优化的模型能够很好地分析和预测该工艺及系统条件下猪粪厌氧消化液的氨氮去除结果。所选自变量对于氨氮脱除的影响力从大到小依次为:气液比、液流量、气流量。研究结果可为猪粪厌氧消化液的连续处理提供依据。     

Potential of anaerobic digestate of dairy manure in suppressing soil‐borne plant disease

Frequent use of pesticides to control soil‐borne plant disease leads to environmental pollution and the development of pesticide resistance in phytopathogens. Soil amendment is considered to have the potential of suppressing plant disease because of its biological properties. However, information on anaerobic digestate is limited. In this study, potential of antagonistic activities of anaerobic digestate against phytopathogens were investigated by detecting the amounts of antagonistic bacteria (Bacillus and Pseudomonas) in anaerobic digestates of dairy manure. The results showed that anaerobic digestion increased the total amounts of Bacillus and Pseudomonas in digestate. Bacillus suppressed growth of phytopathogens, while Pseudomonas did not show any antagonistic activities. These results indicated that Bacillus was an effective antagonistic bacterium in digestate against phytopathogens. Furthermore, two selected isolates, B11 (Bacillus subtilis) and B59 (Bacillus licheniformis), were applied in field experiments and showed significant reduction in percent infection of potato late blight (Phytophthora infestans). These results demonstrate the benefits of digestate in suppressing soil‐borne plant diseases caused by antagonistic bacteria.     

Effects of 5 years of digestate application on biomass production and quality of cocksfoot (Dactylis glomerata L.)

Anaerobic digestion of biomass produces biogas for combustion and also provides a residual digestate. Although sometimes regarded as a waste product, the nutrient‐rich chemical composition of digestate makes it a potential organic fertilizer for agriculture. The goal of this study was to evaluate the effectiveness of digestate as a fertilizer on the biomass yield and chemical composition of cocksfoot (Dactylis glomerata L.). In a 5‐year small‐plot field experiment digestate fertilization treatments supplying 90, 180, 270, 360 and 450 kg N ha^?1 were compared with untreated plots and plots fertilized with 180 kg N ha^?1 of mineral N fertilizer. Swards fertilized with digestate produced higher biomass yield compared with the control. The same rate of nitrogen fertilizer (180 kg N ha^?1) supplied as digestate and from mineral fertilizers gave similar results on biomass yield. Herbage in swards fertilized with digestate contained less nitrogen, but the C:N ratio was much more suitable for biogas production. Digestate fertilization resulted in higher concentrations of cellulose and hemicellulose in biomass and lower contents of the inhibitors of anaerobic digestion—sulphur, calcium, magnesium and phosphorus—compared with those of swards receiving mineral fertilizers.     

藻-菌耦合系统对猪场沼液的净化效果及其影响条件研究

针对猪场沼液中氮磷含量高且碳氮比严重失调不利于生化处理这一问题,选用对养猪废水净化效果好的近具刺链带藻和有机物降解效率高的商业化菌剂构建藻-菌系统,探讨其对猪场沼液的净化效果及其运行条件。结果表明,添加有机物降解菌不仅有助于促进微藻的生长,使微藻生物量最大值达到1.47 g·L-1,较未添加菌剂处理提高了23.53%,还能促进废水中碳氮磷的去除效果,其中总有机碳、氨氮和总磷的去除率分别提高了13.40%、3.39%和5.90%。藻-菌系统在不同温度条件下对猪场沼液中碳氮磷的净化效果差异明显。温度为30℃时最利于藻菌系统中微藻的生长,且对总有机碳和总磷的去除效果最好,此时微藻生物量最高值能达到2.21 g·L-1,总有机碳和总磷去除率为72.64%和26.66%;而最利于氨氮去除的温度为40℃,这与高温条件下氨氮易挥发有关。不同光照强度下藻-菌系统对污染物净化能力也不同。随着光照强度的增加,系统中微藻生长速度和光合产氧能力逐渐增加,系统对碳氮磷的去除效果也增强,而当光照强度从400μmol photons·m-2·s-1增加到600μmol photons·m-2·s-1时系统中微藻的生长速度和污染物的去除效果并没有提高,可见将光照强度控制在400μmol photons·m-2·s-1时系统中微藻生物量、总有机碳、氨氮和总磷去除率最高,分别为2.35 g·L-1、57.03%、68.01%和59.66%。研究表明,添加有机物降解菌可以促进微藻的生长,从而促进其对猪场沼液的净化效果,该藻菌系统运行的适宜温度和光照条件分别为30℃和400μmol photons·m-2·s-1。     

喷施木醋酸对苹果树叶片和果实品质的影响

为探索木醋酸在苹果生产中作为植物生长调节剂的功能和作用,通过木醋酸及其与沼液耦合喷施苹果树,研究木醋酸和其沼醋耦合液对苹果树叶片生长及苹果品质的影响,结果表明:单施木醋酸,苹果树叶绿素的质量分数为47.72mg/g,比对照高4.57%;叶面积为32.57cm2,比对照高8.49%;百叶厚度为5.03cm,比对照高1.21%;百叶鲜质量为75.16g,比对照高6.96%;百叶干质量为32.59g,比对照高0.59%。单施木醋酸平均单果质量为210.2g,比对照高3.8%;相对体积质量为0.89,比对照高3.49%;可溶性糖质量分数为11.4g/100g,比对照高11.8%;总酸质量分数为2.93g/kg,比对照低0.68%;维生素C质量分数为1.25mg/100g,比对照高17.92%;蛋白质质量分数为0.38g/100g,比对照高5.56%,除相对体积质量外其他指标均达到差异显著水平。证实木醋酸及其与沼液耦合喷施,对促进苹果树叶片生长发育和提高苹果品质具有较好的协同增效作用。     

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.     

Unbalanced nutrient ratios in pelleted compound recycling fertilizers

The aim of this study was to contribute to the development of pelleted compound recycling fertilizers with favourable handling and spreading characteristics and balanced nutrient ratios by combining nitrogen (N)‐ and phosphorus (P)‐rich waste resources (meat bone meal, fish sludge or food waste) with potassium (K)‐rich bottom wood ash. Pelleted compound recycling fertilizers with good durability and low dusting tendency were produced by roll‐pelleting preheated waste resources at a suitable moisture content. However, the nutrient ratios in the final products were insufficiently balanced, with too low N concentrations relative to P and K to meet crop demands. In a bioassay using barley (Hordeum vulgare ) and a nutrient‐deficient sand/peat mixture, the relative agronomic effectiveness (RAE ) of pelleted compound recycling fertilizers and reference recycling fertilizers was 22–42% of that of mineral compound fertilizer. Growth limitation was due to reduced N availability (mineral fertilizer equivalent ‐ MFE = 35–57%) or reduced P availability (MFE  = 20–115%), with the greatest P fertilizer value obtained for digestate based on dairy manure and fish sludge. Availability of K in bottom wood ash was masked by the experimental soil.     

Effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors: Process performance and digestate characteristics

The objective of this study was to investigate the effect of solid–liquid separation on anaerobic digestion of dairy manure in semi‐continuous stirred tank reactors. Reactors fed with liquid fraction of dairy manure (screened liquid manure) were kept in water baths at mesophilic (Run 1) and thermophilic (Run 3) temperatures, respectively, while reactors fed with water diluted manure and kept at mesophilic (Run 2) and thermophilic (Run 4) temperatures as control reactors. The performances of reactors were compared in terms of biogas and methane production, and digestate characteristics. The methane yields obtained from screened manure were higher than those from diluted manure at both mesophilic and thermophilic temperatures, while the highest methane yield was 185 L/kg VS_added under thermophilic temperature. Solid–liquid separation also had improved the effect on digestate fertilizer characteristics. Among four digestates from reactors, the highest contents of nutrients, N (4.12 g/kg) and P (2.36 g/kg) were found in Run 3, while the highest content of K (3.42 g/kg) was found in Run 1. These results showed the benefits of solid–liquid separation of dairy manure on process performance and digestate characteristics.     

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.