Seaweed residuals as fertilisers in agriculture

This presentation holds information how seaweed residuals can be used as fertilisers for leek and oats. What kind of commercial fertiliser products are available from the Organic Materials Review Institute (OMRI)? How seaweeds have been exploited through ages as fodder and fertiliser along the Norwegian coast but lost value due to modernisation of agriculture and production of mineral fertilisers. How seaweed (algae fibre) and fish bones can be applied as a fertiliser and how they have affected growth and nutritional parameters in ryegrass and leek plants

Effect of fish bones and algae fibre as fertilisers for ryegrass

In organic growing, both in Norway and elsewhere in Europe, significant amounts of fertiliser products not derived from certified organic farming are used, such as dried poultry manure or other types of fertilisers derived from conventional farms such as animal by-products. Organic agriculture aims to be independent of conventional agriculture, and fertilisers derived from harvesting of natural materials may be a relevant alternative. Catching of wild fish, and collection or cultivation of seaweeds, result in residual products which contain essential plant nutrients. Sediments of fish bones, which are residues from hydrolysis of fish remains used to produce fish oil and soluble proteins, are rich in nitrogen and phosphorus. Residues from seaweeds (algae fibre), after extraction of soluble nutrients sold as a liquid fertiliser, are rich in potassium and sulphur. However, we do not know much about how such residues affect plant growth. This topic was studied in a pot experiment with annual (Westerwold) ryegrass, which was harvested five times during the experimental period, April-August 2018. We had four replicates per treatment, and fish bones and algae fibre were applied either as fresh material or after drying at 105 °C. The control treatment was an experimental soil without any fertiliser, and we also had a treatment with calcium nitrate (Calcinit). The three types of fertilisers were applied in low and high amounts, where we aimed at a fertilisation level corresponding to 300 or 600 kg nitrogen (N) per ha (corresponding to 30 or 60 kg per daa). However, the actual amounts of N applied in fish bones, and algae fibre were somewhat lower than this. The total number of treatments was 11. Application of fish bones gave a significant increase in the production of ryegrass. In total, across two N levels, and the drying status of materials, the accumulated above-ground yield over five harvests (stubble included) was 3.3 g DM per pot for fish bones, as compared with 2.2 g DM per pot in the control treatment. Fertilisation of ryegrass with algae fibre and Calcinit both gave an average yield of 2.6 g DM per pot. Converting these numbers to kg DM per ha, the accumulated yields were 7 166 kg/ha without any fertiliser, 8 541 kg/ha with algae fibre, 8 616 kg/ha with Calcinit and 10 916 kg/ha with fish bones. The average yield increase in % of the control yield was 19% with algae fibre, 20% with Calcinit and 52% for fish bones. Nitrogen was the nutrient which was supposed to give the most significant effect on the production of plant dry matter. Somewhat more N was applied with Calcinit than with fish bones, but the yields were still considerably higher with fish bones. This was likely explained by the phosphorus (P) content of the fish bones (no P is present in Calcinit). Drying at 105 °C did not reduce the positive growth effect since slightly higher yields were observed with dried than with fresh materials. Fertilisation with algae fibre led to luxury uptake of potassium (K) in above-ground material of ryegrass while causing low uptake of calcium (Ca) and magnesium (Mg). In spite of high concentrations of arsenic (As) (33 mg/kg DM) in algae fibre, the concentrations of As in ryegrass plants amended with this material were below the limit of detection. Both fish bones and algae fibre contain valuable plant nutrients and organic matter, which may have a positive effect as fertilisers and soil amendments. However, they are not well balanced as compared with the requirements of agricultural crop plants. Hence, unless special nutrients are requested, they need to be combined or mixed with other sources of nutrients and organic matter, to produce a valuable fertiliser which will also be easy to use in practice. Several further studies are required to possibly develop commercial fertiliser products for organic growing from marine-derived residual materials such as fish bones and algae fibre

Harvesting our fertilisers from the sea - an approach to close the nutrient gaps in organic farming

Organic production in Europe is currently dependent on the input of fertilisers derived from conventional agriculture, such as farmyard manure, slurry and fertilisers derived from slaugther residues. A significant part of the nutrient flows in our food systems goes in one direction, from land to sea, via sewage and leaching. Harvesting marine organisms for fertilisation, or utilising residual materials e.g. from fish industry as fertilisers, may close such nutrient gaps and promote active cycling of nutrients. At NORSØK, we are studying the use of algae fibre (rich in potassium (K), magnesium and sulphur) and fishbones (rich in nitrogen (N) and phosphorus (P)) as fertilisers. High yields were produced with fishbones, and the short-term N availablity was much higher than for mineral N fertiliser or dried poultry manure. Plants with a long period of nutrient uptake benefited from algae fertiliser. However, seaweeds contain significant amounts of arsenic (As), and easily available K may impact a balanced mineral content in the food or feed product. Excess P in the fishbones may cause eutrophication if this fertiliser is applied to cover the N demands of the crop. Research is needed to make a well balanced fertiliser

Noen må ta seg av rest-råstoffene: Fisk og alger som gjødsel til planter

Organic production in Europe is currently dependent on the input of fertilisers derived from conventional agriculture, such as farmyard manure, slurry and fertilisers derived from slaugther residues. A significant part of the nutrient flows in our food systems goes in one direction, from land to sea, via sewage and leaching. Harvesting marine organisms for fertilisation, or utilising residual materials e.g. from fish industry as fertilisers, may close such nutrient gaps and promote active cycling of nutrients. At NORSØK, we are studying the use of algae fibre (rich in potassium (K), magnesium and sulphur) and fishbones (rich in nitrogen (N) and phosphorus (P)) as fertilisers. High yields were produced with fishbones, and the short-term N availablity was much higher than for mineral N fertiliser or dried poultry manure. Plants with a long period of nutrient uptake benefited from algae fertiliser. However, seaweeds contain significant amounts of arsenic (As), and easily available K may impact a balanced mineral content in the food or feed product. Excess P in the fishbones may cause eutrophication if this fertiliser is applied to cover the N demands of the crop. Research is needed to make a well balanced fertiliser

Restråstoff fra havet - prima plantenæring, men viktige utfordringer

This hand-out summarises experimental details and results from a combined outdoor-pot and field experiment with oats and leek in 2019, fertilised with algae fibre and fishbones. The hand-out was given to participants visiting a field demonstration of the experimental site, at Tingvoll farm

Forsøk med marine restråstoff som gjødsel

A field experiment over 2 years is conducted at Tingvoll farm to study the effect on plant growth and soil and plant characteristics when fish waste and seaweed residues are applied as fertilisers. This presentation was made to accompany participants visiting the field experiment on an open day, August 13, 2020

Harvesting Our Fertilisers From The Sea - An Approach To Close The Nutrient Gaps In Organic Farming

Organic production in Europe is currently dependent on the input of fertilisers derived from conventional agriculture, such as farmyard manure, slurry and fertilisers derived from slaugther residues. A significant part of the nutrient flows in our food systems goes in one direction, from land to sea, via sewage and leaching. Harvesting marine organisms for fertilisation or utilising residual materials e.g. from fish industry as fertilisers, may close such nutrient gaps and promote active cycling of nutrients. At NORSØK, we are studying the use of algae fibre from seaweed (rich in potassium (K), magnesium and sulphur) and fishbones (rich in nitrogen (N), phosphorus (P) and calcium) as fertilisers. In a pot experiment with ryegrass (11 treatments, 4 replicates, 5 harvests), high yields were produced with fishbones, and the short-term N availability was much higher than for mineral N fertiliser. The same result was confirmed in a field experiment with dried poultry manure as control treatment (1 fertilisation level, 5 fertilisers, 4 replicates, random block design), and an outdoor pot experiment (2 fertilisation levels, 5 fertilisers, 4 replicates, random block design). Plants with a long period of nutrient uptake benefited from algae fertiliser. However, seaweeds contain significant amounts of arsenic (As), and easily available K may impact a balanced mineral content in the food or feed products. Excess P in the fishbones may cause eutrophication of this fertiliser is applied to cover N demands of the crop. Research is needed to make a well-balanced commercial fertiliser

Effects of Formic Acid Preservation of Fishbones on the Extractability of Ammonium Lactate–Acetate Soluble Calcium, Phosphorus, Magnesium, and Potassium

Fishbones contain significant amounts of plant nutrients. Fish residues may be preserved by acidification to pH < 4, which may affect the chemical extractability, and the plant availability of nutrients when applied as fertilisers. Grinded bone material from cod (Gadus morhua) heads was mixed with formic acid to investigate if this would increase the concentrations of ammonium lactate–acetate (AL)-extractable nutrients. Two degrees of fineness of fishbones (coarse 2–4 mm; fine < 0.71 mm) were compared at pH 3.0 and 4.0 plus a water control in a laboratory study over 55 days. Samples for measurement of AL-extractable P, Ca, Mg and K were taken on day 2, 15, 34 and 55. Whereas more formic acid and thereby lower pH clearly increased the concentrations of AL-extractable calcium (Ca-AL) and magnesium (Mg-AL), AL-extractable phosphorus (P-AL) was only significantly increased in finely grinded bones at pH 3. After 34 days at pH 3, 6% of the total content of P was extracted by AL in fine fishbones. In the water control, about 1% of the P was extracted, possibly from phospholipids. This P-AL concentration was well above P-AL extracted from acidified coarse fishbones (pH 3 and 4) and from fine fishbones acidified to pH 4. With acidification, about 30% of total Ca and 100% of total Mg were extracted by AL, and the Ca-AL and Mg-AL concentrations were closely correlated. A possible reason for lower P-AL in coarse fishbones at pH 3 and 4, and in fine fishbones at pH 4 than in water controls may be a precipitation of apatite from phospholipids and dissolved calcium.publishedVersio

Fertilisation effects of marine-derived residual materials on agricultural crops

This final report from the project “Residual materials from marine industries as fertilisers in organic agriculture” is an example of blue-green collaboration. Such collaboration has been a strategic goal for many Norwegian research and innovation activities since the terms bioeconomy and circular economy came high on the agenda. Significant amounts of residual raw materials from marine industry are still poorly utilized. Traditionally, seaweeds and residues of fish and other sea animals were applied as feed and fertilisers along the coast of Norway, as elsewhere in coastal regions. These valuable materials should still be applied in agriculture, but the application needs to be adapted to a more professional and large-scale production. Organic agriculture aims at being self�sufficient in nutrients and other inputs for the production. A further aim is to recycle nutrients and organic matter not only inside the farm by feeding manure-producing animals, but by recycling nutrients lost from the farm by sales of products, and by runoff and emissions. The RESTOR project (2018-2022) has provided resources for establishing a significant research and developmental work on marine-derived fertilisers at the Norwegian Centre for Organic Agriculture (NORSØK). Marine�derived fertilisers, especially from sustainable collection or capture of natural renewable resources, may fit well to the aims of organic agriculture. The project has tested residual materials rich in bones from industry processing white fish species (cod, saithe, longfish etc.), and residual material from chemical extraction of rockweed. The materials have been tested as fertilisers and soil amendments, with controlled trials indoor and in the field. A general result is a very rapid growth effect of fishbones in the year of application, with a residual effect in subsequent years resembling that of dried poultry manure. The algae fiber has no immediate fertiliser effect but has a significant residual growth effect. Due to the content of cadmium (Cd), algae fiber is a class II soil amendment product. This implies that it may be applied with up to 20 tons of dry matter per hectare over 10 years, according to Norwegian regulation. An amount close to this level was tested in ryegrass in 2020. The tetany ratio, which is an assessment calculated to assess the risk of tetany in ruminants based on the concentrations of potassium (K), magnesium (Mg), and calcium (Ca) in plant material applied as feed, was then well above the critical level. Hence, we recommend that the material should not be applied at a higher rate than 10 tons per hectare over 5 years (half the maximal rate for each application), to avoid excess uptake of potassium in crop plants. When applied as the single fertiliser material, both fishbones and algae fiber are unbalanced and should be blended with other materials. The project tested a mix where 30% of the nitrogen (N) was derived from algae fiber and 70% from fishbones. This fertiliser gave good yields both in the year of application, and in one or more subsequent growing seasons. With higher prices on energy, there is increased interest for alternative sources of plant nutrients which may complete existing fossil resources. Most European countries are currently dependent on importing phosphorus (P) and potassium, which is a challenge in a world with increasing levels of conflicts. Significant amounts of nutrients are found in the sea, but we still need both research and developmental work to establish value chains for marine-derived fertilisers which may complete the currently applied fertilisers in both conventional and certified organic agriculture. We also need adapted regulations for such products. A proposal for new regulation on organic fertilisers in Norway includes strict limits for arsenic (As), which may significantly hamper the utilization of seaweed material in fertilisers and for soil amendment. We need more research to assess such limit values. The R&D work with marine-derived fertilisers is well established, and continues, both at NORSØK and with other research organizations

Fish waste as fertiliser - effect of drying methods on fish waste and supplementing fish waste with other residual raw materials to form an organic fertiliser

In organic farming systems, soil-plant systems fertility is sustained by recycling of nutrients through the addition of organic inputs and nitrogen fixation by clover and other legumes. Several of the nutrients in fertilisers are limited resources. Thus, it is crucial to recycle nutrients from various value chains so that in the future also one can produce fertilisers that ensure good plant crops in both conventional and organic agricultural production. The fishing industry produces large amounts of fish waste. In 2018 in Norway about 40% of fish waste was not utilised, which is a substantial amount. Fish waste such as fish backbones and bones-rich heads are an important source of phosphorus and calcium. We applied fish waste (fish sediments, conserved with formic acid) that originates from the white fish industry in our field experiments with ryegrass, oats, and leek. Fish sediments showed a quick and good effect on the growth of plants. However, to apply as a fertiliser, the fish sediments need to be dried to remove moisture, reduce odour and deterioration rate. The drying method/drying temperature can affect the pH, total nitrogen, and ammonium nitrogen concentrations. In this project, we investigated how the fish waste (fish sediments and minced fish backs) are affected by the drying in a cabinet, adjusted to temperatures 25C, 40C, and 80C with and without air-circulation, and by drying in a freeze dryer and a microwave oven. We studied how different drying temperatures affect the sample weight over time and which method was most effective. Additionally, we also investigated how different methods of drying can affect the pH and the concentrations of total nitrogen and ammonium nitrogen in fish sediments and minced fish backs. Altogether, cabinet drying with air-circulation was found to be more effective as compared to drying without air-circulation for both fish sediments and minced fish backs, particularly in terms of reduction of moisture/weight reduction over time and also the appearance of the material. The dried samples of fish sediments showed slightly higher pH values (4.8 – 5.3) compared to wet fish sediments (pH 4.5). Contrary, the dried samples of minced fish backs showed equal or slightly lower pH values (6.7 – 7.1) compared to wet minced fish backs (pH 7.1 or pH 7.5). The drying temperature and the drying with and without air-circulation also affected the concentrations of total nitrogen and ammonium nitrogen. The samples of fish sediments dried at 25C with air-circulation showed the lowest concentrations of total nitrogen and ammonium nitrogen. The samples of minced fish backs dried at different temperatures with- or without air-circulation showed minor differences for the concentrations of total nitrogen. Though, for ammonium nitrogen, some variations were observed among samples, where microwave oven-dried samples showed the greatest concentration. Algae fibre, bottom ash, and crab shells are residual raw materials (RRMs) that are/can become available in Møre og Romsdal/Trøndelag. These materials possess suitable concentrations of some of the macronutrients, such as potassium, sulphur, calcium, and magnesium, and can be utilised as additives to fish waste or other fertilisers. However, these materials also contain toxic elements, such as cadmium, chromium, zinc, arsenic and lead. Regulations about fertilisers of organic origin have specific limits for heavy metals contents as a basis for classifying fertilisers. In crab shells, the concentration of arsenic was a bit over the proposed limit of quality class I soil amendment products. Algae fibre had a concentration of arsenic at the border level of the proposed limit of quality class III and cadmium in class II. Bottom ash showed contents of heavy metals zinc, nickel, cadmium, and copper higher than for quality class 0. Neither fish waste nor other RRMs have sufficient amounts of nitrogen, phosphorus, and potassium to give a fertilisation combination that can fulfill grass-clover ley, oats and leek requirements. Fish sediments and minced fish backs can be applicable in certain conditions such as lack of phosphorous in the soil. The bottom ash can be applied as an additional fertiliser when there is a lack of potassium and phosphorus in the soil. By performing calculations, we found that RRMs: fish sediments, minced fish backs, algae fibre, bottom ash and crab shells in combination with cattle manure or commercially available fertiliser Eco 16-1-0 can accomplish the nutritional requirements of an organically cultivated oat, leek and grass-clover ley with two harvests with middle levels of clover. Fish sediments / minced fish backs or algae fibre, bottom ash, and crab shells can give a good fertiliser effect but must be mixed with other fertilisers to balance the primary nutrients. The contents of some of the heavy metals are too high in these materials and cannot be applied without any processing