Tore Krogstad

High performance constructed wetlands for cold climates

Abstract In 1991, the first subsurface flow constructed wetland for treatment of domestic wastewater was built in Norway. Today, this method is rapidly becoming a popular method for wastewater treatment in rural Norway. This is due to excellent performance even during winter and low maintenance. The systems can be constructed regardless of site conditions. The Norwegian concept for small constructed wetlands is based on the use of a septic tank followed by an aerobic vertical down-flow biofilter succeeded by a subsurface horizontal-flow constructed wetland. The aerobic biofilter, prior to the subsurface flow stage, is essential to remove BOD and achieve nitrification in a climate where the plants are dormant during the cold season. When designed according to present guidelines a consistent P-removal of > 90% can be expected for 15 years using natural iron or calcium rich sand or a new manufactured lightweight aggregate with P-sorption capacities, which exceeds most natural media. When the media is saturated with P it can be used as soil conditioner and P-fertilizer. Nitrogen removal in the range of 40–60% is achieved. Removal of indicator bacteria is high and < 1000 thermotolerant coliforms/100 ml is normally achieved.

Liquid digestate from anaerobic treatment of source-separated household waste as fertilizer to barley.

This study examined the efficiency of different organic waste materials as NPK fertilizer, in addition to the risk for leaching losses related to shower precipitation in the first part of the growing season. The experiment was tested in a pot trial on a sandy soil in a greenhouse. Six organic fertilizers were evaluated: liquid anaerobic digestate (LAD) sourced from separated household waste, nitrified liquid anaerobic digestate (NLAD) of the same origin as LAD, meat and bone meal (MBM), hydrolysed salmon protein (HSP), reactor-composted catering waste (CW) and cattle manure (CM). An unfertilized control, calcium nitrate (CN) and Fullgjødsel® 21-4-10 were used as reference fertilizers. At equal amounts of mineral nitrogen both LAD and Fullgjødsel® gave equal yield of barley in addition to equal uptake of N, P, and K in barley grain. NLAD gave significantly lower barley yield than the original LAD due to leaching of nitrate-N after a simulated surplus of precipitation (28 mm) at Zadoks 14. There was significantly increased leaching of nitrate N from the treatments receiving 160 kg N ha−1 of CN and NLAD in comparison with all the other organic fertilizers. In this study LAD performed to the same degree as Fullgjødsel® NPK fertilizer and it was concluded that LAD can be recommended as fertilizer for cereals. Nitrification of the ammonium N in the digestate caused significantly increased nitrate leaching, and cannot be recommended.

A phosphorus Index for Norway

Abstract The phosphorus (P) Index, a risk assessment tool, is a simple approach used to rank the potential for P loss from agricultural fields. The P Index identifies areas where sources of P coincide with high risk of P transfer. Factors included in the P Index, developed for Pennsylvania, USA were justified in relation to Norwegian conditions and relevant changes were made. Phosphorus application rate was modified by crop P removal. Additional factors for: 1) P release by freezing of plant residues, 2) flooding frequency, 3) risk of leaching, and 4) annual precipitation were included. Management practices in the Index were adjusted to reflect the effect of time and method of P application on P loss, as well as erosion control measures relevant to agricultural management in Norway rather than Pennsylvania. Testing of the suggested P Index showed that it ranks the potential for P loss from several agricultural catchments in the south-eastern part of Norway relatively well (R 2=0.79). Continuous development of the Index to include new knowledge about processes for P loss as well as regional differences is of great importance for future use of the P Index.

Contrasting responses of root morphology and root-exuded organic acids to low phosphorus availability in three important food crops with divergent root traits.

Available phosphorus (P) is one of the most important factors affecting crop production worldwide. Study on improving plant P uptake is hence of global importance. We have investigated the responses of root morphology and root-exuded organic acids to low P availability in three important food crops (barley, canola and potato) with divergent root traits using a hydroponic culture system. Results showed that plants evolved divergent adaptations of root morphology and exudation as a response to low P availability. These results could underpin future efforts to improve P uptake of the three crops which are important for future sustainable crop production.

Phosphorous Sorption by Filtralite P—Small Scale Box Experiment

Abstract Phosphorus (P) sorption of light weight aggregate, Filtralite P has been examined through a box experiment which imitates a horizontal subsurface flow wetland system. The results showed that after the P breakthrough, the outlet P concentration increased with time according to the amount of P applied. Small scale boxes with a high inlet P concentration (15 ppm) and high loading rate (5–2.5 L d−1) reached 90% saturation level relatively quickly (after about 150 days of operation), while the boxes with low hydraulic loading rate (1.25 L day−1) were 70–90% saturated after 18 months of operation. The total P removal was dependent on pH, Ca, and the inlet P concentrations, but was independent of the hydraulic loading rate. Extraction of total P from the saturated filter material showed that the sorbed P accumulated within the inlet section of the box and decreased gradually towards the outlet as well as towards the bottom layer. Even after large amounts of Ca had leached out of the system, Filtralite P still had a very high P removal capacity. After resting periods the P sorption capacity of the material was regenerated, the P concentration in the effluent decreased by 22–53%.

The potential of natural ecosystem self-purifying measures for controlling nutrient inputs

Abstract Most ecosystems have a certain assimilative capacity regarding plant nutrient or biodegradable organic matter. Knowledge of the metabolizing processes of different ecosystems enable the use of natural systems for pollution abatement from agricultural, domestic and industrial sources. Such ecologically engineered natural systems are often very cost efficient. At the Centre for Soil and Environmental Research (JORDFORSK) studies of degradation processes and the fate of plant nutrients in small streams, ponds, wetlands, vegetative filter strips and soil are being conducted in order to gain experience with and develop self purifying methods. Preliminary results show that denitrification in streams remove only a minor part of the annual nitrogen (N) transport (1–15%), but that this process can remove a considerable part of the N transport during summer. Constructed ponds and wetlands in streams draining agricultural areas showed 10–56% retention of soil particles, 23–40% of phosphorous (P) and 5–13% of N. Narrow ponds had a higher efficiency than wide ponds per unit surface area. Short-term experiments with vegetative strips treating agricultural runoff show a sediment removal of over 95%, a P removal from 80–90% and N removal between 60 and 75%. A multistage subsurface constructed wetland treating domestic waste-water removed an average of 97% P, 91% BOD, 80% of suspended solids, 55% N and 99.9% E. coli over the first 18 months of operation. Preliminary results from a multistage plant with constructed ponds and wetlands treating landfill leachate show high treatment efficiency for the same parameters. A rapid infiltration plant in northern Norway showed an average removal of 99% P, 90% COD and 73% N after 4 years of operation. These results show that self purifying measures offer potential for design of pollution abatement systems for agricultural as well as domestic purposes in the Norwegian climate.

Long-term effects of crop rotation and different fertilization systems on soil fertility and productivity

The effects of crop rotation and fertilization systems on yield and soil fertility parameters have been investigated in a long-term field trial established in southeast Norway in 1953. The results indicate the small differences between crop rotations and different fertilization systems in yield and soil fertility parameters; the decreasing trend in soil organic carbon (SOC) (from 3.8 to 3.7%) and increasing trend of N with time (from 0.32 to 0.36%) and, as a result, the decreasing trend in C/N ratio (from 12 to 10).

Rhizosphere Organic Anions Play a Minor Role in Improving Crop Species' Ability to Take Up Residual Phosphorus (P) in Agricultural Soils Low in P Availability

Many arable lands have accumulated large reserves of residual phosphorus (P) and a relatively large proportion of soil P is less available for uptake by plants. Root released organic anions are widely documented as a key physiological strategy to enhance P availability, while limited information has been generated on the contribution of rhizosphere organic anions to P utilization by crops grown in agricultural soils that are low in available P and high in extractable Ca, Al, and Fe. We studied the role of rhizosphere organic anions in P uptake from residual P in four common crops Triticum aestivum, Avena sativa, Solanum tuberosum, and Brassica napus in low- and high-P availability agricultural soils from long-term fertilization field trials in a mini-rhizotron experiment with four replications. Malate was generally the dominant organic anion. More rhizosphere citrate was detected in low P soils than in high P soil. B. napus showed 74–103% increase of malate in low P loam, compared with clay loam. A. sativa had the greatest rhizosphere citrate concentration in all soils (5.3–15.2 μmol g−1 root DW). A. sativa also showed the highest level of root colonization by arbuscular mycorrhizal fungi (AMF; 36 and 40%), the greatest root mass ratio (0.51 and 0.66) in the low-P clay loam and loam respectively, and the greatest total P uptake (5.92 mg P/mini-rhizotron) in the low-P loam. B. napus had 15–44% more rhizosphere acid phosphatase (APase) activity, ~0.1–0.4 units lower rhizosphere pH than other species, the greatest increase in rhizosphere water-soluble P in the low-P soils, and the greatest total P uptake in the low-P clay loam. Shoot P content was mainly explained by rhizosphere APase activity, water-soluble P and pH within low P soils across species. Within species, P uptake was mainly linked to rhizosphere water soluble P, APase, and pH in low P soils. The effects of rhizosphere organic anions varied among species and they appeared to play minor roles in improving P availability and uptake.

Effect of fertilization, tiller cutting and environment on plant growth and yield of European Blueberry (Vaccinium myrtillus L.) in Norwegian forest fields.

BACKGROUND: European blueberry (E. blueberry; Vaccinium myrtillus L.) is a natural resource demanded by the processing industry with potential of domestication. Therefore an investigation of the possibilities of partial cultivation of native stands was started. OBJECTIVE: To increase knowledge of how E. blueberry react to soil types, climate, mineral nutrition, organic amendments and cutting of tillers. METHODE: Five forest fields with E.blueberry stands in Norway were examined. Besides natural development influenced by soil parameters and climate, effect of fertilization and plant pruning were examined in the municipalities of Bardu in Troms county (68◦N) and of Snasa and Lierne in Nord-Trondelag county (64◦N). Experiments were executed in randomized block designs in forest fields of native E. blueberry stands. RESULTS: The fields that performed best had O-layers close to 7 cm or thicker. The C/N ratios indicate that N was not easily available in any field, and addition of mineral fertilizer containing nitrogen and phosphor show that especially N increased elongation of long shoots and more nodes were developed. However, the effect on number of short shoots per long shoot initiated a growth gain only the last of two years. The positive growth effect of fertilizer was not followed by higher yields throughout the years, and strongest fertilization level (N60P40) reduced yield in average of four years. Adding composted wood chips or wood chips alone increased tiller growth in the birch-field in Bardu both years, but only the first year in the pine-field; this was not reflected in higher yield. Cutting of shoots to the ground reduced yield and full yield potential was not recovered before the third year after cutting. CONCLUSION: The results suggest that by improving growth conditions, especially by securing a thick natural O-layer and adjusting soil macro nutrient composition, growth conditions could be improved; and that fruit yield were down the two first years after pruning.

Combined waste resources as compound fertiliser to spring cereals

There is increasing awareness of the need for efficient nutrient recycling in food production. Therefore, a pot experiment was conducted to contribute to the development of alternative compound fertilisers with balanced nutrient ratios for cereal production. We compared the (1) fertilisation effects and (2) effects on soil chemistry of four organic nitrogen (N)- and phosphorous (P)-rich waste-based products (WBPs), applied with or without potassium (K)-rich bottom wood ash (BWA). WBPs and BWA were applied at two rates (80 kg N ha−1 + 35 kg K ha−1 and 160 kg N ha−1 + 70 kg K ha−1) to spring barley (Hordeum vulgare) in year one and spring wheat (Triticum aestivum) in year two, and the effects were compared with those of commercial mineral and organic compound fertilisers. The K fertilisation effects of BWA were masked by the soils ability to provide plant-available K during both years of the experiment. Plant-available N was, therefore, the growth-limiting factor for barley in year one, when there were no differences in grain yield between treatments with and without K-rich BWA. The mineral fertiliser equivalent of WBPs was 64–118% for N uptake in barley grain, but can be expected to be lower under field conditions. During year two, wheat yield was determined by the plant availability of P and N. Meat-rich meat and bone meal caused P deficiency at the lower application rate as a result of alkaline soil conditions, whereas the P in BWA appeared to be almost as plant-available as soluble mineral P.