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Article

Assessing the Value of Organic Fertilizers from the Perspective of EU Farmers

by
Michael Friedrich Tröster
Agricultural Education Center Triesdorf, Markgrafenstraße 12, 91746 Weidenbach, Germany
Agriculture 2023, 13(5), 1057; https://doi.org/10.3390/agriculture13051057
Submission received: 7 April 2023 / Revised: 11 May 2023 / Accepted: 12 May 2023 / Published: 15 May 2023
(This article belongs to the Section Agricultural Economics, Policies and Rural Management)
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Abstract

:
Fertilizer prices have risen worldwide since the end of 2021. In this context, the value of organic fertilizers has also changed from the farmers’ perspective. Hence, an open question about their value arises with an increased demand for organic fertilizers. This question must be addressed individually for each farm. Hence, a linear optimization model is applied. The model can be adapted to farm conditions and provides mineral and organic fertilizers as plant nutrition variables. The price level at which an organic fertilizer becomes competitive within the farm can be identified by parameterizing the organic fertilizer prices. This substitution value marks the maximum price a buyer could pay for a particular fertilizer. This method is repeated in the study in different scenarios. For an exemplary digestate (N-P2O5-K2O = 5-2-5 kg per ton), substitution values between EUR 1.70 and EUR 16 per ton could be determined, excluding transport and application cost. This study provides a basis for a decision support system that farmers can use to determine the value of organic fertilizers. As a positive implication, it can be expected that organic fertilizers will be used where they contribute best to value creation.

1. Introduction

The term organic fertilizer summarizes a range of residual materials used for plant nutrition. The most important organic fertilizers include, for example, slurry, digestate, manure, straw, compost, green manure, sewage sludge, and meat-and-bone meal. These organic fertilizers are of great importance worldwide for the supply of nutrients in crop production. Organic fertilizers also play a major role within the EU, as shown by a comparison of mineral fertilization and the nutrient uptake of plants: According to an evaluation by the World Bank, a total of 157 kg of the nutrients nitrogen (N), phosphate (P2O5), and potash (K2O) were applied in the EU in 2020 in the form of mineral fertilizer per hectare of arable land [1] (Note: the nutrients phosphorus and potassium are reported throughout the entire manuscript in their oxidized form). The average removal of these nutrients (N, P2O5, and K2O) in 2020, based on the average EU wheat yield of 4.35 tons per hectare [2], was around 214 kg per hectare (own calculation in accordance with [3]). This clearly shows that organic fertilizers contribute significantly to the nutrient supply of crops within the EU. However, the distribution and use of organic fertilizers are subject to strong cross-regional differences. In particular, regions with high livestock density, such as northwestern Germany, the Netherlands, or Denmark [4], have significant surpluses of organic fertilizers. In the Baltic States, the opposite is the case [4]. In parallel to the above-mentioned cross-regional differences, serious differences can also be observed at the level of individual farms within the regions. The spectrum ranges from pure cash crop farms that largely use mineral fertilizers, to intensive livestock farms or biogas plants. In some cases, the latter two produce significantly more organic fertilizer than can be sensibly used on their own farmland. Up to what amount organic fertilization is reasonable depends on many factors and will not be addressed in detail here. It should be noted, however, that historical studies [5] have already found a decreasing yield increase with increasing fertilization. Current studies indicate a decrease in nitrogen use efficiency (NUE) with increasing use of nitrogen fertilizers [6,7,8]. Both findings show that as the amount of factor input increases, the efficiency of organic fertilization decreases. As a result, negative environmental impacts such as nutrient pollution and gaseous nitrogen losses occur [9,10]. The EU wants to reduce such negative environmental effects and is putting pressure on the national legislation of the member states with regulations such as the Water Framework Directive [11] and the National Emissions Reduction Commitments (NEC) Directive [12]. The EU Commission’s farm-to-fork strategy also aims to further increase the efficiency of fertilization [13].
To summarize: Within the EU, we find an unbalanced distribution of organic fertilizers both cross-regionally and regionally; a balanced distribution of these fertilizers over the entire agricultural area would have economic and social benefits in terms of nutrient utilization and environmental impact; and due to national fertilizer legislation [3,14,15], many farms are already forced to pass on organic fertilizers. Hence, there is already a considerable need to exchange organic fertilizers between farms, which inevitably leads to the following question: what price can be set for organic fertilizers?
As natural compound fertilizers, they can substitute mineral fertilizers, so their valuation is highly dependent on the mineral fertilizer market. Considering the energy crisis and the war in Ukraine, fertilizer prices have multiplied compared to 2020 (see Figure 1).
In addition, the availability of fertilizer is not guaranteed in all cases. This situation had a significant impact on the demand for organic fertilizers in the 2022 season.
However, from the farmers’ perspective, organic fertilizers have some disadvantages compared with mineral fertilizers, for example, owing to increased transport and application costs or a lower NUE [17]. Moreover, the aforementioned restrictions imposed by fertilizer legislation mean that farms with a large amount of organic fertilizer must pass on considerable quantities to other farms. For example, in Germany, nitrogen use from liquid organic fertilizers is currently limited to 170 kg per hectare [15]. Hence, organic fertilizers have often been valued below their actual nutrient value and, in some cases, have even been subject to “transfer costs”. The severe distortions in the mineral fertilizer market are now forcing farms to reassess the value of organic fertilizers and reconsider their previous practices. The literature offers numerous studies on the evaluation of organic fertilizers. Often, the focus is on plant cultivation aspects, such as assessing the fertilizer effect. Delin et al. [18] compared the methods for estimating the nitrogen fertilizers’ effect on organic residues. Brown [19] evaluated various organic fertilizers from livestock farming. Then, Menino et al. [20] dealt with a novel approach, namely, the use of black soldier fly larvae frass as an organic fertilizer. These studies are among the many studies that address organic fertilizers from a crop production perspective. Meanwhile, studies on the economic evaluation of organic fertilizers are less common. Kall et al. [21] and Thuriès et al. [22] used a deterministic approach to capture the monetary value of organic fertilizers. However, notably, the actual economic value of an organic fertilizer corresponds to a farm-specific substitution value. Numerous farm-specific aspects have an influence on this substitution value. Keplinger and Hauck [23] therefore used a linear optimization model to determine the economic value of organic fertilizers. They focused on the economic valuation of organic fertilizers from livestock farming in connection with the influence of transport distance and the quantity of these fertilizers.
The present study aims to facilitate a fair economic valuation of organic fertilizers between supplying and receiving farms. Based on Keplinger and Hauck [23], a model-based approach is chosen to determine the substitution value, but different questions are analyzed:
  • Are there seasonal differences in the substitution value?
  • What is the influence of fluctuating mineral fertilizer prices?
  • What is the influence of the soil nutrient status of the receiving farm?
  • What is the influence of the NUE of organic fertilizers?
Answering these questions, in conjunction with a reassessment of the substitution value of organic fertilizers, is particularly relevant for farmers and their advisors. Owing to the differentiated consideration of season, soil nutrient status, and NUE, under which conditions organic fertilizers achieve the highest substitution value may be determined. Optimally, this knowledge will contribute to an increase in the use efficiency of organic fertilizers at the regional level and thus have positive economic and ecological impacts.

2. Materials and Methods

The question concerning the monetary value of organic fertilizers arises as soon as an exchange between farms takes place. Often, the supplying farm is under pressure, for example, because internal use is impossible or uneconomical for reasons of efficiency or is limited for legal reasons. Therefore, this study primarily assumes a consumer market for organic fertilizers and takes the perspective of the receiving farm to determine the substitution value of organic fertilizers. Thus, the results reflect the maximum price that can be paid from the buyer’s perspective.
Marginal costs and marginal benefits determine the maximum price that a buyer of organic fertilizer could pay. For example, if the application of organic fertilizer leads to higher costs than the previous application of fertilizer, marginal costs arise. Moreover, if the use of organic fertilizer can reduce previous fertilizer expenditures, then marginal benefits arise. Marginal costs and marginal benefits also vary within the farm, for example, the first unit of organic fertilizer applied can be used more efficiently than the last unit before reaching a potential saturation limit. Where this potential saturation limit lies depends on the situation and is examined based on comparative scenarios:
  • Base scenario: Fertilizer prices as of 02/2023 (Table 1); soil phosphate supply normal (CAL: 10–20 mg/100 g soil); soil potash supply normal (CAL: 10–20 mg/100 g soil); NUE 36% of Nt.
  • Fertilizer price scenario (variation of nitrogen fertilizer prices): Fertilizer prices according to 09/2022 (Table 1); otherwise, identical to the base scenario.
  • P&K supply scenario (variation of phosphate (P2O5) and potash (K2O) content in soil): Phosphate supply in soil high (CAL: 21–30 mg/100 g soil); potash supply in soil very high (CAL: >30 mg/100 g soil); otherwise identical to the base scenario.
  • N efficiency scenario (variation of NUE of organic fertilizers): NUE (related to Nt) increased to 45%; otherwise, identical to the base scenario.
  • Timing (variation of the transfer window in quarters).
These scenarios are analyzed for an exemplary receiving farm with 90 ha of arable land and 30 ha of grassland. With this utilized agricultural area, the farm is a representative of the most important category of farms in the EU in terms of agricultural area. More than half of the agricultural area in the EU is managed by farms with more than 100 hectares [24] with a share of permanent grassland of 34% (own calculation based on [25]). The crop rotation for the arable land is winter wheat–winter barley–(catch crop)–silage maize, with each main crop covering one third of the arable land per year.
A linear optimization model based on the following structure (modified after Andrei [26] (p 119)) is used to represent these scenarios for the exemplary farm:
minimize  f(x)
subject to:   g(x) ≤ 0
h ( x ) = 0
The monetary objective function f (Equation (1)) and the sample constraint functions g (Equation (2)) and h (Equation (3)) represent linear functions. The restrictions arise from the nutrient requirements derived from soil nutrient supply, crop, and crop rotation. In parallel, legal restrictions must be considered. For example, the requirements of German fertilizer legislation are applied, including an upper limit of 170 kg of nitrogen per hectare from organic fertilizers and strict limitations and deadlines for fertilizing measures after the main crop has been harvested. More detailed information on fertilizer requirements and fertilizer legislation can be found in the form of laws and directives [3,14,15]. Another part of the model is the variable x, which represents the use of mineral and organic fertilizers (Table 1). Mineral fertilizers are included in the model at market prices, and price assumptions are assigned to organic fertilizers. By parameterizing these price assumptions step by step, farm-specific substitution values of organic fertilizers can be determined using the model.
To provide concrete results for the assessment of an organic fertilizer in the further course of the study, liquid biogas digestate is used as a representative example (see Table 1). In context with the previously defined receiving farm, the following results can therefore not be transferred directly to other constellations. However, the presented valuation method is transferable to other constellations and is a major part of this study.

3. Results

This section shows the determined substitution values of the biogas digestate (Table 1, row 1) under the assumptions of the various scenarios. A quarterly differentiation is made to illustrate the seasonal influence on the substitution value of the organic fertilizer.

3.1. Impact of Mineral Fertilizer Prices—“Fertilizer Price” Scenario

The volatile fertilizer prices clearly influence the substitution value of organic fertilizers (Table 1). Figure 2 shows the comparison of the “Base” and “fertilizer price” scenarios (for scenario definitions, please refer to Section 2). Under the conditions of the base scenario, a receiving farm could bear a maximum cost of EUR 12 per ton of digestate in all quarters (Figure 2). However, transport, storage, and application costs reduce this value if they are to be paid by the receiving farm. The quantities that can be purchased at these maximum costs differ considerably between the quarters, as can be seen from the bar height in the diagram (Figure 2). For instance, the sample farm with 90 ha of arable land and 30 ha of grassland would take 2822 tons of digestate at a maximum cost of EUR 12 per ton in the first quarter. In the third quarter, the quantity drops to 711 tons at this price because the NUE and especially the use options for organic fertilizer are already clearly limited at this time. With the beginning of the third quarter, the sample farm is only able to apply nitrogenous fertilizers on grassland and winter barley due to fertilizer legislation [3,14,15]. With 711 tons, the uptake limit has already been reached, which is why no increase in the uptake quantity is possible even if prices continue to fall (see Figure 2, third quarter).
With increased fertilizer prices, as of September 2022 (“fertilizer price” scenario), the receiving farm could accept EUR 16 per ton of digestate. However, the change in the uptake quantity between the quarters is comparable to the base scenario.

3.2. Impact of Soil Nutrient Status—“P&K Supply” Scenario

In this study, the soil nutrient supply with phosphate and potash has the greatest influence on the substitution value of the biogas digestate. Compared with the base scenario, the maximum substitution values are halved from EUR 12 to EUR 6 per ton (for scenario definitions, please refer to Section 2). The difference in the substitution values of the scenarios “Base” and “P&K supply” is EUR 6 per ton. This difference can also be interpreted as the maximum effort that is acceptable to transfer the biogas digestate to remote fields with lower nutrient content. Figure 2 also shows that higher nutrient contents of phosphate and potash in the soil also lead to a decrease in the sensibly applicable fertilizer quantities. The “P&K supply” scenario is also the worst case scenario in this study. This scenario has the poorest overall conditions for achieving a high substitution value.

3.3. Impact of NUE—“N Efficiency” Scenario

The analyzed change in NUE has the smallest influence on the substitution value in this study. Compared with the base scenario, the quarterly substitution values increase by EUR 2 per ton to EUR 14 per ton (for scenario definitions, please refer to Section 2). The NUE for biogas digestate was derived from Lichti and Wendland [17]. According to this, a NUE of 45% (based on Nt) can only be achieved under favorable conditions and with corresponding loss-reducing technology. Against this background, the gain in substitution value of EUR 2 per ton is also regarded as the maximum additional expenditure for loss-reducing application technology (with an improvement in NUE from 36% to 45%, based on Nt).

3.4. Average Substitution Value and the Effects of Overlays

The results explained so far show the maximum substitution values that can be achieved according to the marginal value principle. Thus, they refer to the monetary value of the first unit of biogas digestate used by a receiving farm. In practice, however, there are cases where larger quantities of organic fertilizer are exchanged between farms. Table 2 compares which average substitution value would have to be applied if a total transfer of 3000 tons of biogas digestate is involved.
If in the base scenario, 3000 tons are taken over by the receiving farm, then the maximum substitution value of EUR 12 per ton cannot be kept. The quantity of 2822 tons for which this maximum substitution value is valid in the first quarter is exceeded. The maximum substitution value for the remaining 178 tons is EUR 10 per ton. The average substitution value in this case is EUR 11.88 per ton. Similar to this observation, the average substitution values in the remaining cases are also reduced. As only a part of the 3000 tons can be spread directly in the third quarter in all cases, additional costs for the storage, including storage and removal from storage, must be applied to the overstocked quantity. Costs of EUR 5 per ton are used, which of course vary from farm to farm.
In the worst case, the receiving farm would therefore only be able to pay EUR 1.70 per ton (Table 1, third quarter) if a total quantity of 3000 tons is concerned. As organic fertilization causes higher transport and application costs compared with mineral fertilization, further marginal costs are charged to the receiving farm. With farm-specific additional costs for transporting and spreading the biogas digestate of, for example, EUR 3.00 per ton, the remaining substitution value is EUR −1.30 per ton. In this case, the supplying farm would have to make additional payments to the receiving farm.

4. Discussion and Conclusions

The results of this study show that organic fertilizers have a significantly different value for receiving farms depending on the situation. In the best case (scenario “fertilizer price”; first quarter; Figure 2), a maximum substitution value of EUR 16 per ton of biogas digestate is achieved. In the worst case (scenario “P&K supply”; third quarter; Table 2), the average substitution value is only EUR 1.70 per ton. In both cases, these values are further reduced by additional costs for transporting and applying organic fertilizers. The transport and application costs are strongly dependent on the situation. Assuming a rental price of EUR 75 for tractor (150 kW), including fuels and driver, at an hourly application rate of 50 tons and a rental price of EUR 1.50 for tanker and applicator, this results in total transport and application costs of EUR 3.00 per ton. According to this study, the following factors contribute to the differentiation of the substitution values, starting with the strongest influence:
  • Phosphate and potash levels in the soils of the receiving farm;
  • Price situation on the fertilizer markets;
  • Quantity of organic fertilizer transferred in connection with timing (quarter);
  • NUE.
As the soil nutrient levels of phosphate and potash play a major role, higher transport costs can be accepted to transfer organic fertilizers from surplus to deficient regions. This finding is not new [27,28], but an objective economic assessment is a prerequisite for correctly mapping the transport value. The strong influence of fertilizer markets in combination with their volatility [29] also leads to the need for a regular reassessment of the substitution value of organic fertilizers. The price volatility on the fertilizer market is also visible in this study. A glance at Figure 1 reveals the past ups and downs of the world market prices of fertilizers. According to information from southern German retailers, the price of calcium ammonium nitrate at the end of April 2023 was EUR 275 per ton, which is once again significantly below the price level of February 2023 (EUR 470 per ton, see Table 1). This means that a reassessment of the value of organic fertilizers would have become necessary within a period of only two months. A model-based decision support system (DSS) is appropriate to simultaneously consider fluctuating prices and other influencing factors such as timing, transferred organic fertilizer quantity, and NUE. In this study, an LP-based optimization model is proposed as a methodological framework for such a DSS. LP has long been one of the established and commercialized methods of operations research. For this very reason, the scientific community nowadays occasionally criticizes the methodological ambition of this method. However, it must be acknowledged that LP is a highly efficient and, moreover, comprehensible method for the determination of farm-specific substitution values according to the marginal principle and is currently used for this purpose [30]. Due to the commercialization of this method, LP can be used by almost everyone today. This is particularly relevant regarding the user requirements for a DSS [31].
When developing a DSS, the limitations of this study must be solved because, to date, only a static sample farm has been considered. Thus, all results refer to one crop rotation; a uniform NUE across all crops and quarters; and general assumptions on storage, transport, and application costs. A farm-specific DSS must be flexible in this respect. For farm-specific statements on the substitution values of organic fertilizers, such a tool must contain (i) an interface for current mineral fertilizer prices and (ii) an input option for field-, crop-, technology-, and time-specific user data. However, dynamically embedding an adjusted NUE is challenging. It is known that NUE depends on many factors, including the crop, timing of application, nitrogen form and nitrogen content of the organic fertilizer, weather conditions, application technique, amount of organic fertilizer applied, and various site conditions [17,32,33]. An ideal solution would be an integrated function to estimate the NUE based on the above-mentioned aspects. However, since the necessary database is lacking, a static NUE approach based on the experimental results of Lichti and Wendland [17] was chosen. To show the effects of a varying NUE, a corresponding scenario was included in this study (“N-efficiency scenario”). It is shown that the NUE has only a minor influence on the substitution value of organic fertilizers and is therefore of little importance in this study. The situation is different when it comes to farm-specific optimization of the allocation of organic fertilizers. In this case, it is essential to dynamically consider factors influencing NUE.
However, some limitations of this study can probably not be overcome by the described DSS. The literature shows that organic fertilization can have positive yield effects [34,35,36,37,38]. This case is especially true on depleted soils without long-term organic fertilization [39]. Drivers of such positive yield effects are, for example, micronutrients [40,41,42] or the general improvement of soil’s physical properties [42,43]. However, negative yield effects are also reported in connection with organic fertilization. This case is often because of soil compaction [44] caused by the use of heavy agricultural equipment [45]. Both positive and negative yield effects of organic fertilization are not considered in this study but can strongly influence the substitution value in individual cases.
When supplying farms use the approach presented in this article to determine a price for organic fertilizers, the following should be noted: A substitution value determined from the buyer’s perspective is by no means a market price but the monetary upper limit that a buyer could accept (compare maximum substitution values in Figure 2). Under conditions of a buyer’s market, it is expected that farms that are under pressure to sell organic fertilizer will do so below value. This case will likely reduce the market price for organic fertilizer in surplus regions (compare average substation values in Table 2). In these cases, however, the valuation approach presented here offers a good opportunity to check the transportability of organic fertilizer from surplus to deficit regions.
This study provides important insights into the monetary valuation of organic fertilizers and also forms a basis for a DSS that is yet to be developed. An important finding of this study is that the value of organic fertilizers cannot be generalized. Instead, a farm-specific approach, for example using a DSS, is recommended. In addition to the pricing of organic fertilizers, such a DSS can also contribute to a more efficient regional distribution of these fertilizers. Ecological goals that are important from a social perspective can also be pursued by allocating organic fertilizers in an economically efficient manner.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

CAL = calcium acetate lactate extract; DSS = decision support system; Nt = total nitrogen; NUE = nitrogen use efficiency.

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Agriculture 13 01057 g001 550
Figure 1. Monthly prices of fertilizer worldwide (source [16]; exchange rate: 1 EUR = 1.1014 USD).
Figure 1. Monthly prices of fertilizer worldwide (source [16]; exchange rate: 1 EUR = 1.1014 USD).
Agriculture 13 01057 g001
Agriculture 13 01057 g002a 550Agriculture 13 01057 g002b 550
Figure 2. Quarterly substitution values for biogas digestate under changing scenarios. Remarks: Substitution values excluding transport, storage, and spreading. Sample digestate (Nt = 5 kg t−1; P2O5 = 2 kg t−1; K2O = 5 kg t−1; S = 0.8 kg t−1); “Base” scenario: fertilizer prices according to 02/2023; phosphate supply in soil normal (CAL: 10–20 mg/100 g soil); potash supply in soil normal (CAL: 10–20 mg/100 g soil); NUE 36% of Nt. Scenario “fertilizer price”: fertilizer prices according to 09/2022; otherwise, identical to the “Base”. Scenario “P&K supply”: phosphate supply in soil high (CAL: 21–30 mg/100 g soil); potash supply in the soil very high (CAL: >30 mg/100 g soil); otherwise, identical to the “Base”. Scenario “N efficiency”: NUE increased to 45%; otherwise, identical to “Base”. Fourth quarter (not shown) largely identical to the third quarter.
Figure 2. Quarterly substitution values for biogas digestate under changing scenarios. Remarks: Substitution values excluding transport, storage, and spreading. Sample digestate (Nt = 5 kg t−1; P2O5 = 2 kg t−1; K2O = 5 kg t−1; S = 0.8 kg t−1); “Base” scenario: fertilizer prices according to 02/2023; phosphate supply in soil normal (CAL: 10–20 mg/100 g soil); potash supply in soil normal (CAL: 10–20 mg/100 g soil); NUE 36% of Nt. Scenario “fertilizer price”: fertilizer prices according to 09/2022; otherwise, identical to the “Base”. Scenario “P&K supply”: phosphate supply in soil high (CAL: 21–30 mg/100 g soil); potash supply in the soil very high (CAL: >30 mg/100 g soil); otherwise, identical to the “Base”. Scenario “N efficiency”: NUE increased to 45%; otherwise, identical to “Base”. Fourth quarter (not shown) largely identical to the third quarter.
Agriculture 13 01057 g002aAgriculture 13 01057 g002b
Table
Table 1. Fertilizer selection.
Table 1. Fertilizer selection.
Price #1 09/22 Price #1 02/23 NP2O5K2OS
(EUR t−1)(EUR t−1)(kg t−1)(kg t−1)(kg t−1)(kg t−1)
Liquid biogas digestate #2??5250.8
Calcium ammonium nitrate870470270
Calcium ammonium nitrate + S890485240 40
Ammonium sulfate nitrate910545260 130
Urea980670460
Nitrogen phosphate (20 20)930720200200
Diammonium phosphate1195880180460
Potash640615 40050
Remarks: #1 Consumer prices (net) ex wholesale depot (Southern Germany). #2 The usability of the nitrogen content of 5 kg per ton is controlled by the NUE factor. This factor is 0.36 or 0.45, depending on the scenario (based on Lichti and Wendland, [17]).
Table
Table 2. Substitution value #1 according to an average value approach for 3000 tons delivery quantity.
Table 2. Substitution value #1 according to an average value approach for 3000 tons delivery quantity.
ScenarioFirst QuarterSecond QuarterThird Quarter
(EUR t−1)(EUR t−1)(EUR t−1)
Basic11.88 #211.888.18 #3
Fertilizer price15.5415.5412.18
P&K supply4.574.521.70
N efficiency13.4313.2510.18
Remarks: #1 Substitution value excluding transport and spreading. #2 Calculation: E U R   11.88 = ( 2822   t   × EUR   12 + 178   t   × EUR   10 ) ÷ 3000   t ; (compare Figure 2, first quarter). #3 Calculation: EUR   8.18 = ( 320   t   × EUR   12 + 2680   t   × ( EUR   12 − SC ) ) ÷ 3000   t (compare Figure 2, first and third quarters). SC = costs for storage incl. storage and retrieval = EUR 5 per ton.
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Tröster, M.F. Assessing the Value of Organic Fertilizers from the Perspective of EU Farmers. Agriculture 2023, 13, 1057. https://doi.org/10.3390/agriculture13051057

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Tröster MF. Assessing the Value of Organic Fertilizers from the Perspective of EU Farmers. Agriculture. 2023; 13(5):1057. https://doi.org/10.3390/agriculture13051057

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Tröster, Michael Friedrich. 2023. "Assessing the Value of Organic Fertilizers from the Perspective of EU Farmers" Agriculture 13, no. 5: 1057. https://doi.org/10.3390/agriculture13051057

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Tröster, M. F. (2023). Assessing the Value of Organic Fertilizers from the Perspective of EU Farmers. Agriculture, 13(5), 1057. https://doi.org/10.3390/agriculture13051057

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