Nitrogen Fertilizer Replacement Value Research Articles

Benchmarking the relationship between nitrogenous compounds in wine grape juice with nitrogen fertiliser applications to determine nitrogen fertiliser replacement value

Benchmarking the relationship between nitrogenous compounds in wine grape juice with nitrogen fertiliser applications to determine nitrogen fertiliser replacement value

Ammonia water as a biobased fertiliser: Evaluating agronomic and environmental performance for Lactuca sativa compared to synthetic fertilisers

The European Union is actively promoting circular agriculture, aiming to reduce external inputs, close nutrient cycles, and minimise harmful emissions. This shift has spotlighted bio-based fertilisers (BBFs) as a potential substitute for energy-intensive and environmentally detrimental synthetic fertilisers. Nevertheless, research on resilience and eco-friendliness of BBFs remains limited. To address this, novel manure-derived BBF - ammonia water (AW) was examined in terms of agronomic (crop yield, nitrogen (N) fertiliser replacement value (NFRV)) and environmental (N2O, CO2, CH4, NH3) parameters in a lettuce pot cultivation. The AW had an initial alkaline pH of 11.2 (AWpHini), and another variant with pH adjusted to 5 (AWpH5) was tested for performance comparison against calcium ammonium nitrate (CAN). The agronomic efficiency was tested at three incremental N rates (30%, 60%, and 100% of crop N demand). AWpHini resulted in similar crop yield and N uptake compared to CAN for all N rates. NFRV for all N rates of AWphini exceeded 90%, however, significant reverse trend was noted for AWph5 (NFRV <90% for all rates) likely due to product's low pH affecting soil microbes. In terms of environmental performance, gaseous emissions for AWphini (52.2 CO2eq) showed significantly lower (p < 0.05) trend in comparison to CAN (120.2 CO2eq), AWph5 (114.1 CO2eq) and urea (101.3 CO2eq). The effect of acidification was observed in NH3 emissions, where AWpH5 resulted in significantly lower (p < 0.05) emissions compared to AWpHini. More research in real-world field conditions with different crops is needed to confirm ammonia water's potential as a synthetic nitrogen fertiliser replacement.

Nitrogen fertilizer replacement values of organic amendments: determination and prediction

AbstractThe nitrogen fertilizer replacement value (NFRV) quantifies the value of organic amendments as a nitrogen (N) fertilizer, and is commonly defined as the extent to which organic fertilizer N can replace mineral fertilizer N. NFRVs can be calculated by comparing the crop N uptake from equal N application rates of mineral and organic fertilizer, or by comparing the N rates of both fertilizers needed to obtain equal crop N uptake. Currently, NFRVs are mainly known for animal manure, whereas other organic waste products may become available as fertilizer products in the future. In this study, a pot experiment with spring wheat was performed to (1) assess NFRVs of a range of organic amendments; (2) compare NFRVs based on equal N application with NFRVs based on equal N uptake; and (3) assess which product characteristics explain observed variation. Observed NFRVs varied between 6.2 and 78.8%, with the lowest value for raw food waste and the highest for fishmeal. NFRVs were overestimated when calculated based on equal N application rate (with on average 6.9% point), and more so at high N application rate (9.0% point). NFRVs should therefore be calculated based on equal N uptake from organic and mineral fertilizers. Nitrogen concentration of the organic fertilizer provided the best explanation of variation observed in NFRVs (R2 = 0.86). These findings give valuable insights into the large variation in value of organic waste streams as organic fertilizer and can support decisions on sustainable N application rates, to increase crop N uptake and reduce N losses to the environment.

Eight years of eco-intensification of maize-soybean rotation in south Brazil: grain production and nitrogen fertilizer replacement value

Eight years of eco-intensification of maize-soybean rotation in south Brazil: grain production and nitrogen fertilizer replacement value

The effect of catch crops in spring barley on nitrate leaching and their fertilizer replacement value

Catch crops have been proven effective in reducing nitrogen leaching in cropping systems due to their uptake of post-harvest soil mineral N prior to the main percolation season in winter. Information on the residual effect of catch crops, and their nitrogen fertilizer replacement value is scarce. To determine nitrogen fertilizer replacement values for different catch crops a field experiment was conducted over a four-year period on a sandy soil in Denmark, involving different catch crops and catch crop mixtures with non-legume and legume species. The residual effect of the catch crops was measured in spring barley grown in the residual year. For comparison, winter rye was also included. Over the four-year period the spring barley/fodder radish showed significantly lower leaching compared with the other catch crops, and the winter rye had the highest leaching. Regarding the residual effect, fodder radish and ryegrass, were most valuable, with nitrogen fertilizer replacement values ranging from 13 to 41 kg ha-1, based on fertilizer recovery efficiency of 50%. The process based APSIM (Agricultural Production Systems sIMulator) model was used to simulate the spring barley/catch crop rotations and the winter rye, and showed good model performance regarding N leaching and, crop yield and N uptake. The model was then run over a period of 20 years, to determine variations in N leaching and residual effects due to environmental conditions. The simulations showed that catch crops reduced N leaching by 38–64% when grown every year, and by 21–39% when grown only every second year. Nitrogen fertilizer replacement values ranged on average from 28 to 44 kg N ha-1, but showed high inter-annual variability. The nitrogen fertilizer replacement values showed only a weak relationship with the N uptake of the catch crop prior to termination, likely due to long term effects of N mineralisation from catch crop residues and pre-emptive competition for N by the catch crop.

Effects of electrokinetic and ultrasonication pre-treatment and two-step anaerobic digestion of biowastes on the nitrogen fertiliser value by injection or surface banding to cereal crops

Biogas production from anaerobic digestion (AD) of biowastes is restricted by the recalcitrant nature of many substrates, and this may also reduce the fertiliser value of the produced digestate. The degradability of substrates can potentially be enhanced by physico-chemical pre-treatments before AD, and/or the degradation can be increased by a longer digestion time. In this study, we evaluated the effects of electrokinetic (high voltage) and ultrasonication pre-treatments of biowastes in a two-step AD process on nitrogen fertiliser replacement value (NFRV) of digestates obtained from two biogas plants with contrasting hydraulic retention time (HRT) in the primary AD step. The fertiliser value was tested by direct injection to spring barley and surface-banding to winter wheat, and the ammonium N was 15N-labelled to evaluate ammonia losses. The electrokinetic pre-treatment step significantly (p < 0.05) increased the NH4+-N/total N in the digestates before the second AD step but had an insignificant effect on the fertiliser value in winter wheat and spring barley. Ultrasonication pre-treatment had also no significant effect on the fertiliser value. The two-step AD significantly (p < 0.001) increased 15N recoveries and mineral fertiliser equivalence of labelled ammonium-N in winter wheat and reduced ammonia losses, with a significant effect (p < 0.001) observed in digestates sourced from a shorter HRT biogas reactor. The fertiliser equivalence of labelled ammonium-N in the digestates was 80–88% after injection, indicating relatively low N immobilisation with all the digestates. NFRV in the crops was mainly explained by the NH4+-N/total N ratio, C/N ratio and dry matter content of the digestates. The findings suggest that electrokinetic and ultrasonication pre-treatments combined with a second AD step have no considerable impact on the fertiliser value of digestates, whereas a second AD step significantly reduced ammonia losses after application by surface-banding in winter wheat.

Application of Vibrating Reverse Osmosis Technology for Nutrient Recovery from Pig Slurry in a Circular Economy Model.

The rapid growth of the livestock sector in some areas of Europe has caused an imbalance between the generation of livestock manure and the availability of agricultural soil for its direct application as a fertilizer. Since the transport of pig slurry to other areas with nutrient-deficient soils is costly from an economic point of view due to its high water content, the application of new technologies for the concentration of this waste is considered key for reducing management costs. Consequently, the main objective of this study was to demonstrate the potential of vibratory shear enhanced processing (VSEP) operated with reverse osmosis membranes to recover nutrients from the liquid fractions of pig slurry (LF-pig slurry) and digestate (LF-digestate) and obtain concentrated fertilizing products. Use of the VSEP unit permitted reductions in the water contents of the LF-pig slurry and LF-digestate, around 77% and 67%, respectively. Both VSEP concentrates were characterized by their significant nutrient contents and showed a nitrogen fertilizer replacement value similar to that of mineral fertilizer as demonstrated in a barley crop pot-test, although the salinity of the digestate concentrate was identified as a key limitation, negatively impacting the agronomic yield of the test crop.

Fertiliser Effect of Ammonia Recovered from Anaerobically Digested Orange Peel Using Gas-Permeable Membranes

The manufacture of mineral N fertilisers by the Haber–Bosch process is highly energy-consuming. The nutrient recovery technologies from wastes through low-cost processes will improve the sustainability of the agricultural systems. This work aimed to assess the suitability of the gas-permeable membrane (GPM) technology to recover N from an anaerobic digestate and test the agronomic behaviour of the ammonium sulphate solution (ASS) obtained. About 62% of the total ammonia nitrogen removed from digestate using GPM was recovered, producing an ASS with 14,889 ± 2324 mg N L−1, which was more than six-fold higher than in digestate. The ASS agronomic behaviour was evaluated by a pot experiment with triticale as a plant test for 34 days in a growth chamber. Compared with the triticale fertilised with the Hoagland solution (Hoag), the ASS provided significantly higher biomass production (+29% dry matter), N uptake (+22%), and higher N agronomic efficiency 3.80 compared with 1.81 mg DM mg−1N in Hoag, and a nitrogen fertiliser replacement value of 133%. These increases can be due to a biostimulant effect provided by the organic compounds of the ASS as assessed by the FT-Raman spectroscopy. The ASS can be considered a bio-based mineral N fertiliser with a biostimulant effect.

Nitrogen fertilizer replacement value of dairy soiled water in grass swards as affected by timing and rate of application

AbstractDairy soiled water (DSW) is a dilute mixture of cow faeces, urine, milk and detergents produced from the washing of milking plant and holding areas, and contains nutrients. Its N fertilizer replacement value (NFRV), compared to inorganic fertilizer (IF), was determined in a plot experiment on two grassland soils (well‐drained and poorly drained) in SW Ireland over a year with 4 N rates (0, 15, 22 and 30 kg N/ha), nine application timings and four replicates. Herbage was harvested at 4 and 8 weeks after each application to determine the total 8‐week DM yield. While caution is required, as results are based on only two sites and one year, DSW increased herbage production and showed potential to substitute for inorganic fertilizer N with surprisingly high NFRVs of 72 to 90%, potentially offering cost savings to farmers, improved N use efficiencies and reduced risk of nutrient loss to the environment. High NFRV may be due to factors such as the even spread and infiltration of DSW, low rates of ammonia emission or a stimulatory effect on the release of soil N. Yield increased significantly (p &lt; .001) with N rate from approximately 1,200 kg DM ha−1 at 0 kg N/ha to approximately 1,700 kg DM ha−1 at 20–30 kg N/ha but application beyond approximately 20 kg N/ha was associated with increasingly diminished yield response. Yield response was greatest from March to July and poor response in winter suggests a greater risk of N loss during this period.

Viral infection can reduce the net nitrogen inputs of legume break crops and cover crops.

Legumes are used in crop rotations by both large-scale and smallholder farmers alike to increase soil fertility, especially before high-nitrogen-demanding crops such as corn (maize). Legume crop residues and green manures are rich in nitrogen due to mutualistic rhizobia, bacteria that live in their roots and convert atmospheric nitrogen into a biologically available form. Growers can obtain recommendations from local extension offices about how much less inorganic nitrogen fertilizer needs to be added to a subsequent crop following different legume break crops for the predominant soil type (the nitrogen fertilizer replacement value, or NFRV). Due to the intimate relationship between legumes and rhizobia, conditions that affect plant health can also affect the rhizobia and how much nitrogen they provide. We use a combination of empirical data and previously published values to estimate reductions in nitrogen inputs under outbreaks of plant viruses of varying severity. We also use historical fertilizer prices to examine the economic impacts of this lost fertilizer for farmers. We find that fertilizer losses are greatest for crops that fix large amounts of nitrogen, such as clover and alfalfa as opposed to common bean. The economic impact on farmers is controlled by the proportion of plants with viral infections and the price of synthetic fertilizer. In a year of high disease prevalence, attention is normally focused on the yield of the diseased crops. We suggest that farmers growing legumes as break crops should be concerned about yields of subsequent crops as well. Viral diseases can be difficult to diagnose in the field, so the easiest way for farmers to prevent unexpected yield losses in subsequent crops is to test their soil when it is feasible to do so.

Grassland Phosphorus and Nitrogen Fertiliser Replacement value of Dairy Processing Dewatered Sludge

Abstract Dairy processing sludge is currently a bio-based fertiliser being spread to grassland without knowledge pertaining to its phosphorus (P) or nitrogen (N) fertiliser replacement value. This creates uncertainty of desired crop yield achievement and unproductive nutrient recycling and also poses a great challenge to the dairy milk processing industry in promoting their food processing by-product as valuable recyclable fertiliser. Therefore four representative samples, i.e. two activated sludge (aluminium-precipitated (Al-sludge) and iron-precipitated (Fe-sludge)), and two lime-stabilised calcium-precipitated sludge (Ca1- and Ca2-sludge), were examined at field scale to assess P and N availability for crop yield and uptake in comparison to reference mineral fertilisers over one seasonal year. The field plots were set-up on a light textured clay loam soil within the optimum plant available P (Morgan's soil P index 3, i.e. medium / adequate soil P level) in two separate adjoining areas consisting of P and N availability experiments. Each experiment consisted of 40 plots (each 8×2 m2) of 10 treatments with 4 replications arranged in a randomised complete block design. All dairy sludge (40 kg-P ha−1) and mineral P treatments (rates 0–50 kg-P ha−1) produced similar yields and uptake, and crop P was not affected by sludge applications despite the presence of high Al, Ca and Fe. During the experiment there was no significant change in P index (stayed at index 3) indicating that no treatment caused a decline in P into index 2 (i.e. low soil P level), therefore replacing P removed by the crop. The only change in Morgan's P was observed in the Ca-sludge treatments, but this was due to Morgan's reagent overestimating plant available P in high Ca conditions. From N trial plots a significantly higher grass yield and N uptake was observed for Fe and both Ca-type sludge applied plots than the control (zero N) plot during the 1st harvest, while no statistical difference observed in the subsequent harvests (up to 4th harvesting). The N fertiliser replacement value (derived from mineral N response) of sludge samples was observed to be in the order of Fe (54%)>Ca2 (25%)>Ca1 (22%)>Al (8%) with greater promise of N fertiliser efficiency of Fe and Ca types. Overall these bio-based sludges show promise in recycling P and N for grassland application but longer term trials in other soil types considering other environmental aspects (losses to soil, water and air) can further optimize the management of dairy sludge as an alternative to chemical fertiliser.

Cover crop and cereal straw management influence the residual nitrogen effect

Cover crops (CC) may play an essential role in the recycling of nutrients in organic farming systems with cereals. Harvest time of cereals and management of straw in the field can affect the growth of CC and subsequent nitrogen (N) fertiliser replacement value (NFRV) in the following crop. This study investigates 1) the effect of harvest time, 2) cutting height of straw and 3) straw removal from the main crop on CC growth, composition, uptake and NFRV in the following crop and 4) the effect of CC harvest in autumn on the NFRV in the succeeding crop. A CC mixture of mainly red clover, with chicory and ryegrass was sown under a spring barley crop in 2017, and replicated in 2018. Four strategies of barley harvest were conducted: 1) early harvest as whole crop or 2) early harvest of the upper parts only, 3) at maturity with straw removed or 4) at maturity with straw left on the field surface. Subsequently, CC and high stubbles of left straw were harvested and removed in autumn in half of the field replicates. The residual effect was measured in spring barley in the succeeding year. The CC aboveground biomass dominated by the clover had an N uptake for both years of 40−77 kg N ha−1. Variability was significant between years but not caused by the harvest time or by straw management. In the succeeding year, residues from barley and CC could replace 61−85 kg N ha−1 of mineral N fertiliser, which were mostly derived from CC roots and stubble. High straw stubble left (40 cm length) significantly reduced the NFRV of CC shoots by 20%. Root residues (including barley and CC roots) contributed a substantial N supply to the following crop irrespective of aboveground CC biomass. The availability of N derived from CC shoot mineralisation differed significantly in the two years and was also influenced by straw left from the previous crop.

Toward profitable and sustainable bioresource management in the Australian red meat processing industry: A critical review and illustrative case study

The Australian Red Meat Processing (RMP) industry is challenged with ever increasing environmental pressures to reduce their environmental footprint. Wastewater is high strength and requires quality treatment to prevent pollution of surface and ground waters; while much of the solid waste produced is organic and is suitable for land-based disposal. Stricter environmental standards and greater community expectations as well as increasing costs for water, energy and waste disposal require the reduction of resource consumption. This represents an opportunity for the RMP industry to adopt innovative technologies to use bioresources produced on site to increase the plants profitability. This article provides a critical review of solid and liquid waste management at RMP plants outlining the current trends in bioenergy, biofertiliser and value-add byproducts production. The review proceeds to place these developments through an illustrative case study of investigations undertaken at one of Australia’s largest RMP plants investigating technologies and processes to reuse, recycle, and dispose of organic liquid and solid waste. The three main lines of investigation include biogas optimization, reuse of paunch as a fertilizer and opportunities for blood products. Key results from the case study include: 1. Natural gas consumption could be offset with biogas to reduce yearly energy expenditure by up to a further ≈25% by operating lagoons under optimal mesophilic conditions (38 °C); 2. Nitrogen fertilizer replacement value of paunch was found to be comparable to other organic materials used for land application; and 3. The recovery of blood products can yield up to AUD10.5M pa for the enterprise.

Nitrogen and Sulfur Availability in Digestates from Anaerobic Co-digestion of Cover Crops, Straw and Cattle Manure

Anaerobic digestion (AD) has the potential to enhance the availability of nitrogen (N) from green manures; however, part of the sulfur (S) is lost with the biogas. In this study, the N and S availabilities from untreated and digested cover crop (CC) and straw mixtures were measured after application to soil in the laboratory. In addition, a microplot experiment was carried out to assess the N availability in a spring barley crop. A CC consisting of red clover (Trifolium pratense L.) and chicory (Cichorium intybus L.) was harvested and ensiled with barley straw (Hordeum vulgare L.) at different ratios (1:0, 10:1 and 3:1). The silages were either digested alone or co-digested with cattle manure (CM) in continuously fed anaerobic reactors. Six months after soil application, the net inorganic N release was − 7%, 15% and 25% of total N for untreated CC:straw ratios of 3:1, 10:1 and 1:0, respectively. AD significantly increased the net inorganic N release of these plant materials to 5%, 26% and 38% (mono-digestion) and 40%, 41% and 43% (co-digestion with CM). Results from the laboratory experiment corroborated the field experiment in which AD significantly increased the nitrogen fertiliser replacement value (NFRV) of the CC:straw from 19 to 41% of total N applied. Gaseous loss of S up to 30% was observed during AD while the total N content remained unchanged. Sulfate from untreated CC:straw and digestates was immobilised soon after application to soil, resulting in low availability of inorganic S. Digestion of CC and straw significantly reduced N immobilisation but clearly did not contribute to inorganic S supply.

Effects of Fallowing and Nitrogen Application on Striga Infestation, Soil Fertility and Maize Performance

Striga possesses an ominous obstacle to the African continent that is struggling with food security as it affects the livelihood of more than 300 million people. The control of Striga has proved exceptionally difficult. Two fallows, namely natural fallow (NF) and A. histrix fallow (AF) were maintained in 2012, such that the field was divided into two parts and each part was further divided into three replicates. Each part was separated from one another by a strip of 2 m width and the fallow factor was randomly assigned to each part which constituted the main plot. In 2013, the inorganic N fertilizer levels (0, 60, 90 and 120 kg ha-1) were applied to the fallow plots and assigned to the sub-plot. These treatments were laid out in a split plot arrangement fitted to a randomized complete block design with three replicates. The two fallows significantly (P &lt; 0.05) reduced Striga infestation similar to application of N at 60 – 120 kg N ha-1. The two fallows significantly (P&lt; 0.05) increased SOC. Only natural fallow significantly (P&lt;0.05) increased the STN by 36 %. Maize grain yield after natural fallow (1527 kg ha-1) was not significantly (P&gt;0.05) different from that after A. histrix (1943 kg ha-1). Inorganic N application had highly significant (P&lt;0.05) effect on grain yield. Lowest grain yield of 1253 kg ha-1 was obtained without inorganic N application, which was significantly different from those fertilized with inorganic N. Inorganic N fertilizer rate of 60 kg ha-1 seems to be optimum for maize. The Nitrogen Fertilizer Replacement Value of A. histrix was low, 13 kg N ha-1. The effect of both fallows on grain yield was due mainly to increased SOC content.

Nitrogen fertilizer replacement value of digestates from three green manures

Green manure mixtures including legumes and forbs can help to increase N availability in organic arable systems. Anaerobic digestion of green manures may provide ammonium rich digestate, which can be redistributed as fertilizer. The aim of this study was to investigate the effect of plant species composition, cutting strategy and anaerobic digestion on the N fertilizer replacement value (NFRV) of different green manures. Digestates obtained from silages of pure stand lucerne (four cuts/year) and a mixture including lucerne, grass and forbs (two or four cuts/year) were used to fertilize winter wheat (surface banding) and spring barley (injection). In general, NFRV was 46–173% higher in spring barley than winter wheat, due to the different application method and timing, which reflect the common practices in Denmark. NFRV of digestates were 25–63% higher than the corresponding silages, with the largest increase with the most fibrous material (mixture at two cuts/year). Total N concentration (DM based) in the silages largely explained NFRV of the digestates. To obtain NFRV above 60%, total N concentration of silage should exceed 3.5 g 100 g−1 DM, achievable with silages from four-cut strategies. Silages of plant materials with different composition and N content may be similar in terms of biomethane production, but the fertilizer value of the digestates varies considerably depending on total N concentration.

An Investigation into the Fertilizer Potential of Slaughterhouse Cattle Paunch

Abstract. In Australia, recycling of paunch waste to farmland has been suggested as a cost-effective and practicable environmental option, but little is known about its agronomic value. Experimental work was undertaken to assess potential risks due to weed seed contamination, determine the agronomic response of ryegrass ( L.) to soil incorporation of paunch, and investigate short-term greenhouse gas (GHG) emissions. Five types of paunch with compost ages between 2 and 16 weeks were compared with urea (46% N) and applied at field equivalent rates of 0 (control), 150, and 300 kg ha-1 N. The risk of weed contamination from paunch applied to soil appeared to be negligible; however, techniques that enable seed viability to be determined may be required to fully discard such risk. Average dry matter yield with paunch was ~30% higher than untreated grass, but ~35% lower than with urea. Dry matter yield in paunch-treated grass was between 2500 and 3250 kg ha-1 over five cuts conducted at 25-day intervals. Paunch N responses were between 1.12 and 3.25 kg DM kg-1 N depending on compost age, but lower than with urea N (~6.5 kg DM kg-1 N). Nitrogen use efficiency of paunch ranged between 3% and 20%, compared to about 35% with urea. Nitrogen fertilizer replacement value (NFRV) of paunch was highest in the 6-week-old compost (~60%) and ranged between 20% and 55% across all other organic materials. Short-term N2O emissions were similar (p &amp;gt; 0.05) with both mineral and organic amendments; however, CH4 emissions were higher (p &amp;lt; 0.05) from paunch compared with urea-treated soil. Overall, there appears to be potential for paunch-derived products to be used as a source of C and nutrients in crop production. Industry quality specifications for compost are available, but they need to be expanded to incorporate guidelines relevant to paunch. There is a requirement for the value proposition to industry to be determined, including reduced cost of paunch disposal via gate fees. Keywords: Byproducts, Composting, Fertilizer replacement value, Nutrient recovery, Nutrient use efficiency, Recycling of abattoir-derived waste.

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

AbstractAcidification 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 (Nrel,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 Nrel,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 Nrel,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.

Nitrogen fertiliser replacement values for organic amendments appear to increase with N application rates

Nitrogen (N) supply from organic amendments [such as farmyard manure (FYM), slurries or crop residues] to crops is commonly expressed in the amendment’s Nitrogen Fertiliser Replacement Value (NFRV). Values for NFRV can be determined by comparison of crop yield or N uptake in amended plots against mineral fertiliser-only plots. NFRV is then defined as the amount of mineral fertiliser N saved when using organic amendment-N (kg/kg), while attaining the same crop yield. Factors known to affect NFRV are crop type cultivated, soil type, manuring history and method or time of application. We investigated whether long-term NFRV depends on N application rates. Using data from eight long term experiments in Europe, values of NFRV at low total N supply were compared with values of NFRV at high total N supply. Our findings show that FYM has a significant higher NFRV value at high total N supply than at low total N supply (1.12 vs. 0.53, p = 0.04). For the other amendment types investigated, NFRV was also higher at high total N supply than at low total N supply, but sample sizes were too small or variations too large to detect significant differences. Farmers in Europe usually operate at high rates of total N applied. If fertiliser supplements are based on NFRV of the manure estimated at low total N supply, N fertiliser requirements might be overestimated. This might lead to overuse of N, lower N use efficiency and larger losses of N to the environment.

Nitrogen Fertilizer Replacement Value of Concentrated Liquid Fraction of Separated Pig Slurry Applied to Grassland

ABSTRACTSeven grassland experiments on sandy and clay soils were performed during a period of 4 years to estimate the nitrogen (N) fertilizer replacement value (NFRV) of concentrated liquid fractions of separated pig slurry (mineral concentrate: MC). The risk of nitrate leaching when applying MC was compared to when applying mineral fertilizers. Grassland yields in 2009–2012 fertilized with MC were compared with grassland fertilized with two mineral fertilizers: granulated calcium ammonium nitrate and liquid ammonium nitrate (LAN). The mineral fertilizers comprised 50% nitrate-N and 50% ammonium-N, and MC comprised 95–100% ammonium-N. Treatment application rates included zero N and three incremental rates of N fertilization. The liquid fertilizers were shallow injected (0–5 cm). The NFRV of MCs was 75% on sandy and 58% on clay soil with granulated ammonium nitrate as reference, and 89% on sandy and 92% on clay soil with LAN as reference. Risk of nitrate leaching after application of MC, measured in residual soil mineral N post-growing season and N in the upper groundwater in the following spring, was equal to that for mineral fertilizers.