Browsing by Subject "nutrient recycling"
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Development of sustainable practices for using lake sediment as growing medium for grass production (2023)Anthropogenic activities have resulted in huge accumulation of plant nutrients in lake sediments. These nutrients can be recycled back to the overlying water and sustain eutrophication. The release of phosphorus (P) from sediments, i.e. internal P loading, has often been a reason for delay in improvement of lake water quality, after reduced external nutrient loading. By removing the sediment, the internal lake nutrient load can be effectively reduced, and it is widely used in lake water quality restoration. By redirecting the reclaimed nutrients back to primary agricultural production, the need for using mineral fertilizers and virgin materials can be reduced. Currently there is, however, a lack of field-scale experiments and determination of best practices to enable efficient nutrient uptake and minimized nutrient leaching back into the lakes. A field experiment was conducted to study the effects of using P-rich lake sediment in different application methods for growing a mixture of forage grasses. The study focused on soil fertility, plant growth and nutrition, and species composition over a period of four growing seasons in central Estonia. Treatments for reducing nutrient losses included applying the sediment alone (Sed), with surface-incorporated biochar (Sed+BC), and as incorporated with surface-mixed biochar-topsoil mixture (Sed+Soil+BC). A treatment consisting of sandy loam topsoil was set up as control (Soil). The mean dry mass yield in the sediment treatments exceeded the local average grass yields and the N and P uptake rates in above-ground biomass (AGB) exceeded the international estimates for grasses. The sediment had no significant effect on AGB yield in comparison to the control. Similarly, no effect was observed in the yield of weeds, but temporary changes in weed species composition and an increasing trend particularly in nettle abundance on the sediment treatments were recorded. Apart from a transient increase in the amount of soluble potassium, no relevant effects were induced by the incorporated biochar. In conclusion, the sediment performed well and served as a plentiful source of P for grasses for four years. Based on the sufficient concentrations of P, sulphur, calcium and potassium in the plant tissue, yield increase could have been expected but most likely the good fertility of the control topsoil evened out yield differences between growing medium treatments. Based on this study, similar lake sediments can be advised to be used as soil amendments on grass cultivation on an agricultural field. Due to high nutrient concentrations, a lower rate could be applied on a wider field area to control excess in nutrient supply, given that the need of nitrogen fertilization is ensured to match plant-specific requirements.
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(2010)Meat and bone meal (MBM) is a valuable co-product of the rendering industry. Its feed and fertilizer uses were restricted in the EU in 2002 as a result of the occurrence of BSE crisis. Consequently, MBM was land filled, incinerated or used as an alternative fuel in cement production. The re-allowance of the fertilizer use of MBM in the EU since spring 2006 together with the rising prices of industrial nitrogen and phosphorus fertilizers have resulted in amplified research and use of MBM as a fertilizer. Additionally, growing consciousness of both finiteness of resources and deteriorating environmental effects of the artificial fertilizer use have contributed to growing popularity of nutrient recycling. The fertilizer effect and the nutrient uptake efficiencies of the Finnish MBM (N-P-K-Ca 8–6-0.5-15%) compared to mineral counterparts were tested for in present study. Additionally, the fertilizer effect of MBM in mixture with two potassium fertilizers was tested for. A greenhouse experiment with ryegrass (Lolium multiflorum) fertilized with five fertilizers (MBM, mineral fertilizers Y4PK and NK, two mixtures of MBM and potassium fertilizers) was conducted from 2007 to 2008 in Department of Agricultural Sciences greenhouses in University of Helsinki, Finland. Each of the fertilizers was applied on three nitrogen levels (80, 160 and 240 kg N ha-1). Four additional reference treatments (0 kg N ha-1 fertilizer, PK I, PK II and PK III) were included. Six cuts of ryegrass were cut and the yields were recorded. Post-harvest plant and soil analyses were conducted. MBM was shown to be a highly effective N and P fertilizer with fertilizer effect similar or even longer lasting than artificial Y4PK fertilizer. Additionally, unlike highest application levels of mineral fertilizer Y4PK and NK, meat and bone meal treatments did not lower the pH level of the soil. Therefore, it can be concluded that the relatively high Ca content of MBM is useful in preventing further costs for liming the soil. The nutrient uptake efficiencies of MBM were generally somewhat lower than for mineral counterparts. That could be partly attributable to possible immobilization of MBM-N to soil and partly to lower readily plant-available P content of MBM than mineral fertilizers. However, as significant amount of MBM-P is still available for following years, it is justified to use MBM only once in a crop rotation. That makes MBM an especially effective complementary N and P fertilizer for organic farming, where most of the nitrogen need in crop rotation is covered with legumes and manure. The fertilizing potential for mixture of MBM and K fertilizers was shown to be rather high. However, the lack of affordable potassium sources suitable for organic farming is a recognized challenge. Additional research is needed for convalescing MBM as NPK fertilizer.
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(2014)Sewage treatment plants produce circa 150 000 dry tons of sewage sludge in Finland each year. Sewage sludge contains a great amount of organic matter and nutrients but also a wide variety of harmful substances such as persistent organic pollutants and pharmaceuticals. Sewage sludge is waste material that must be properly disposed of. While more efforts are made to close nutrient cycles, the use of sewage sludge in agriculture has become a more attractive option also in Finland. In this study it was assessed whether or not organic contaminants present in sewage sludge may prove to be a problem for sludge applications in Finnish agriculture. The study was performed using mathematical models and data collected from literature. 34 different organic contaminants were selected and their accumulation into agricultural soil was simulated assuming that sludge was applied yearly. In addition, leaching was simulated for seven of the compounds. The simulated concentrations in soil and drain water were compared to predicted no effect concentrations (PNEC) given for each compound. Compound-specific data on each substances' behavior in soil environment and concentrations in sewage sludge was collected from literature. Because the data given in different sources varied, simulations were run for each compound using combinations of different values. For each compound 3–23 simulations were run. Simulations were performed with two models developed for simulating pesticide behavior in agricultural soils, PECsoil-calculator and MACRO 5.2. Finnish data on weather and soil properties were used in the simulations. For many compounds the simulated concentrations in soil and water were in the range of concentrations measured in field trials. According to the simulations, the most problematic compounds present in sludge are triclosan, 17α-ethinylestradiol, ibuprofen and carbamazepine. Triclosan and 17α-ethinylestradiol were the only compounds that exceeded their PNECsoil-values. Persistent organic pollutants such as PFAS- and PBDE-compounds accumulated into the soil very efficiently but did not exceed their PNECsoil-values. Leaching to sub-surface drains and below them was a significant end-point for carbamazepine and ibuprofen. These compounds did not exceed their PNECwater-values. However, the highest yearly average concentration in drain water simulated for ibuprofen exceeded the environmental quality standard proposed for it. The peak concentration in drain water simulated for triclosan was circa 70 times higher than its PNECwater-value. The compound-specific values used in the simulations contained a lot of variation. This increases the uncertainty of the results. However, the simulations demonstrate that based on current knowledge the agricultural use of sewage sludge may in some extreme cases cause harm for the environment.
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Towards local balance of crop and animal farming for recycling of nutrients and for localizing food (2018)Circular economy and nutrient recycling have become central aims of agricultural development domestically and internationally. In Finland the enhancement of nutrient recycling is hindered by the areal dividedness of agricultural production. The high animal densities in West-Finland produce more manure nutrients than the area can sustain whereas in the South-Finland the Uusimaa region is dependent on mineral phosphorus fertilizers as there isn’t enough manures in the region. Also the unutilized grasslands have potential for increasing efficient silage and energy grass production, which enables nutrient recycling through biogas or livestock production. In this thesis the agricultural production structure of Uusimaa is approached from the perspective of the regional feed production and the feed production potential as an enabler of more balanced regional crop-livestock production. Simultaneously the regional nutrient recycling and livestock product self-sufficiency enhances. The method used is MFA (material flow analysis) which is applied to the case study area of the Mäntsälä municipality with results scaled up to the rural areas of Uusimaa County. The materials were based on annual statistics of Finland’s production structure and agricultural production. The Mäntsälä municipality’s nutrient balance of nitrogen and phosphorus, the average yields and self-sufficiency in livestock products were analyzed. Three alternative scenarios were introduced to analyze the possibilities of increasing livestock production, enhancing nutrient recycling and attaining livestock product self-sufficiency. The case area has remarkable potential for livestock production increases. With these increases the cereal dominated region gains the possibility of replacing a majority of mineral fertilizers with the manures. Simultaneously, the municipal production can come close to meeting the municipal consumption. These additions of livestock can be carried out without changes in crop areas, but then the livestock production would depend on imported mineral and protein feeds. Also the increases in protein feed needs can be met by transforming the needed areas from cereal areas. In addition the unutilized grasses provide a potential for enhancing the areal silage production. The case study area can’t meet the areal consumption of livestock produce without using the expanse of the present cereal cultivation areas. The results suggest that Uusimaa and its surrounding rural regions have great potential for increasing livestock production and enhancing the nutrient recirculation, whereas the regional consumption cannot be met with the regional production. To enhance sustainable agroecosystem in Finland changes in production structure, way of production and the consumption patterns of citizens are needed.
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