Diogenes L. Antille

Characterisation of Organomineral Fertilisers Derived from Nutrient-Enriched Biosolids Granules

Organomineral fertilisers (OMFs) were produced by coating biosolids granules with urea and potash. Two OMF formulations with N : P2O5 : K2O compositions: 10 : 4 : 4 (OMF10) and 15 : 4 : 4 (OMF15) were developed for application in grassland and arable crops. Routine fertiliser analyses were conducted on four batches of OMF and biosolids granules and compared with a sample of urea to determine key physical and chemical properties of the materials which affect handling and spreading, soil behaviour, and fertiliser value. Bulk and particle densities were in the range of 608 to 618 kg m−3, and 1297 to 1357 kg m−3, respectively. Compression tests showed that OMF particles undergo deformation followed by multiple failures without disintegration of the granules when vertical load was applied. Static particle strength was between 1.18 and 4.33 N mm−2 depending on the particle diameter. The use of a model for fertiliser particle distribution studies showed that OMF granules should be between 1.10 and 5.50 mm in diameter with about 80% of the particles in the range of 2.25 to 4.40 mm to enable application at 18 m tramline spacing. This research utilises novel technology to improve the fertiliser value of biosolids, reduce disposal costs, and deliver a range of environmental benefits associated with recycling.

Field-Scale Evaluation of Biosolids-Derived Organomineral Fertilisers Applied to Ryegrass (Lolium perenne L.) in England

A field-scale experiment was conducted to compare the suitability of two organomineral fertiliser (OMF) formulations (OMF10—10 : 4 : 4 and OMF15—15 : 4 : 4) with urea and biosolids granules applied to perennial ryegrass. Results showed a 25% to 30% increase in dry matter yield (DMY) with application of OMF compared with biosolids granules but about 5% lower than urea. For OMF, an average input of yielded which was similar to that of urea; whereas, for biosolids, a yield of required an input of but DMY was lower (). Agronomic efficiencies with OMF were in the range of 26 to 35 kg , approximately double those of biosolids but about 5% to 10% lower than urea. Soil extractable P levels remained close to constant; therefore, soil P Index was not affected by OMF application. This result supported the reasons for the proposed OMF formulations and demonstrated the advantage of the products compared with biosolids which induced an increase (), in soil extractable P. The application of OMF at rates which do not exceed the optimum N rate for the grass crop should not induce significant changes in soil P Index including application to soils with satisfactory P levels. OMF application strategies are discussed which will enable minimising environmental concerns and maximising fertiliser use efficiency.

Soil compaction and controlled traffic considerations in Australian cotton-farming systems

Abstract. A literature review was conducted to collate best practice techniques for soil compaction management within cotton-farming systems in Australia. Universally negative effects of traffic-induced soil compaction on the whole-farm system and the wider environment include: (i) increased gap between attainable and potential yields, (ii) increased costs of energy and labour, (iii) reduced fertiliser-use efficiency, (iv) reduced water use efficiency (irrigation and rainfall), (v) increased tillage intensity. Knowledge gaps that merit research priority, and research strategies, are suggested. These include: (i) identifying wider impacts on farm economics to guide decision-making and development of decision support systems that capture the effects of compaction on fertiliser, water, and energy use efficiency; (ii) predicting risks at the field or subfield scale and implementing precision management of traffic compaction; (iii) canopy management at terminal stages of the crop cycle to manipulate soil-moisture deficits before crop harvest, thereby optimising trafficability for harvesting equipment; (iv) the role of controlled traffic farming (CTF) in mitigating greenhouse gas emissions and loss of soil organic carbon, and in enhancing fertiliser and water-use efficiencies; (v) recent developments in tyre technology, such as low ground-pressure tyres, require investigation to assess their cost-effectiveness compared with other available options; and (vi) catchment-scale modelling incorporating changes in arable land-use, such as increased area under CTF coupled with no- or minimum-tillage, and variable rate technology is suggested. Such modelling should assess the potential of CTF and allied technologies to reduce sediment and nutrient losses, and improve water quality in intensively managed arable catchments. Resources must be efficiently managed within increasingly sophisticated farming systems to enable long-term economic viability of cotton production. Agronomic and environmental performance of cotton farming systems could be improved with a few changes, and possibly, at a reasonable cost. Key to managing soil compaction appears to be encouraging increased adoption of CTF. This process may benefit from financial support to growers, such as agri-environmental stewardships, and it would be assisted by product customisation from machinery manufacturers.

Effects of Biosolids-Derived Organomineral Fertilizers, Urea, and Biosolids Granules on Crop and Soil Established with Ryegrass (Lolium perenne L.)

A pot scale trial investigated the agronomic performance of two organomineral fertilizers (OMF15—15:4:4 and OMF10—10:4:4) in comparison with urea and biosolids granules to establish ryegrass (Lolium perenne L.). Two soils of contrasting characteristics and nitrogen (N) application rates in the range of 0–300 kg ha−1 were used over a period of 3 years. Fertilizer effects were determined on: (1) dry matter yield (DMY) and crop responses, (2) nitrogen use efficiency (NUE), and (3) selected soil chemical properties. Ryegrass responded linearly (R2 ≥ 0.75; P < 0.001) to organomineral fertilizers (OMF) application increasing DMY by 2–27% compared with biosolids but to a lesser extent than urea (range: 17–55%). NUE was related to concentration of readily available N in the fertilizer: urea and OMF showed significantly (P < 0.05) greater N recoveries than biosolids. Total N in soil and soil organic matter showed increments (P < 0.05), which depended on the organic-N content in the fertilizer applied. Soil extractable P levels remained close to constant after 3 years of continuous OMF application but increased with biosolids and decreased with urea, respectively (P < 0.05). The application of biosolids changed soil P Index from 5 to 6; hence, there is a need to monitor soil P status. Both OMF10 and OMF15 formulations are suitable for application in ryegrass.

Towards a method for optimized extraction of soluble nutrients from fresh and composted chicken manures

A preliminary method for extraction of soluble nutrients from organic materials is presented that investigates important characteristics of design for efficient extraction. The study was conducted in Polyvinyl Chloride (PVC) columns (length: 50 and 100 mm, diameter: 87.5 mm) filled with fresh and composted chicken manures, packed to densities in the range of 0.2-0.6 g cm(-3). The columns were leached with distilled water. A total of 5 cm(3) of water per cm(3) of material was applied. Leachate collection was sequentially partitioned to enable determination of soluble nutrients throughout time, including: total dissolved nitrogen (TDN), water soluble phosphorus (P) and potassium (K). Waste material state, density of packing and lengths of column all significantly (P<0.05) affected the concentration of ions in the leachate. In general, longer contact time between the percolating water and the material resulted in higher (P<0.05) concentration of ions in the leachate. Cumulative TDN and water soluble-P were greater (P<0.05) in fresh manure leachates, compared with compost leachates. Although, compost leachates provided relatively greater (P<0.05) concentration of K. Salinity ionic concentration of leachates, determined as Na and Cl, was consistently greater from fresh manure as compared to that from mature compost. Fresh manure and mature compost were determined to provide different responses to nutrient leaching because of differences in physico-chemical characteristics. Saturated hydraulic conductivity in fresh manure columns reduced rapidly with application of water to the columns. The mechanisms involved in this process are discussed with the implication for nutrient extraction and use of leachate from chicken manure waste sources.

Phosphorus Release Characteristics from Biosolids-Derived Organomineral Fertilizers

This study investigated the availability of phosphorus (P) following soil application of a novel biosolids-derived organomineral fertilizer (OMF15; 15:4:4) in comparison with single superphosphate (0:18:0). Two soil types of contrasting characteristics were incubated over a period of 90 days at 25 °C and maintained near field capacity. Phosphorus was applied at rates equivalent to 0 (control), 150, and 300 kg ha−1 of P2O5, respectively. Availability of P from OMF15 was low throughout the experiment accounting for less than 6.5% of total OMF15-P applied. It was shown that after the 90 days incubation period, the overall increase in soil extractable P in OMF15-treated soil was marginal in both soil types. For single superphosphate (SSP), P availability ranged from 16% to 46% of total SSP-P applied. Application of SSP increased soil extractable P levels significantly (P < 0.001) compared with unfertilized control soils. The results of this study aided the development of fertilization strategies for the best use of OMF produced from nutrient-enriched biosolids granules for applications in winter cereal and grass crops in England.

Nitrogen Release Characteristics from Biosolids-Derived Organomineral Fertilizers

This study investigated the availability of nitrogen (N) following soil application of a novel biosolids-derived organomineral fertilizer (OMF15—15:4:4) in comparison with urea (46% N). OMF15 is produced by coating biosolids granules (particle size range: 1.10–5.50 mm in diameter) with urea and potash [60% potassium oxide (K2O)], which increase the concentration of mineral N and potassium (K), respectively, resulting in a balanced fertilizer material suitable for application in cereal and grass crops. The study comprised two soil types of contrasting characteristics which were incubated over a period of 90 days at 25 °C and maintained near field capacity. Nitrogen was applied at rates equivalent to 0 (control), 150, and 300 kg ha−1, and soil mineral N measured routinely using standard laboratory techniques. Results showed that the majority of N was released from OMF15 within 30 days from application (range: 40% to 72% of total OMF15-N applied) with a further 10% to 28% in the following 60–90 days. OMF15 required an accumulated thermal time of 2250 degrees-day to release between 68% and 79% of the total OMF15-N applied. From this, it was inferred that mineralization of the organic-N fraction in OMF15 is likely to progress beyond harvest of winter cereal crops in-field conditions in England. The results of this study aided the development of fertilization strategies for the best use of OMF in winter cereal and grass crops.

Issues related to waste sewage sludge drying under superheated steam

Abstract Sewage sludge was dried in a rotary drum dryer under superheated steam. Particle size and moisture content were shown to have significant influences on sticking and agglomeration of the materials. Pouring partially dried sludge (70–80% moisture content, wet basis) directly into the screw feeder of the drum dryer resulted in a significant sticking to the surface of the drum and the final particle size of the product was greater than 100 mm in diameter. The moisture content of this product was slightly less than its initial value. To overcome this issue, the sludge was mixed with lignite at variety ratios and then chopped before being introduced to the feeding screw. It was found that mixing the sludge with lignite and then sieving the chopped materials through a four millimetre mesh sieve was the key to solve this issue. This technique significantly reduced both stickiness and agglomeration of the material. Also, this enabled for a significant reduction in moisture content of the final product.

Field-Scale Evaluation of Calcium Ammonium Nitrate, Urea, and Urea Treated with N-(N-Butyl) Thiophosphoric Triamide Applied to Grassland in Ireland

This study investigated the effects of nitrogen (N) source, rate, and timing of application on dry-matter yield (DMY), N responses, N uptake and N-use efficiency (NUE) in a grass crop. The experiment used three fertilizer treatments: calcium ammonium nitrate (CAN), urea, and urea treated with N-(n-butyl) thiophosphoric triamide (NBTPT), applied at 0 (control), 25, 50, and 75 kg ha−1 of N over eighteen application timings. Results showed relatively lower agronomic performance of urea compared with CAN when applied in early spring. Urea reported lower N responses, lower relative DMY (90 percent), and relative N uptake (85 percent), which translated in lower NUE (0.45 kg kg−1) compared with CAN (0.70 kg kg−1). In spring fertilizer applications, urea and NBTPT showed DMY and NUE values comparable to those obtained with CAN. However, NBTPT enhanced overall performance of urea, which was shown with increasing temperatures toward summer or increasing N application rates. For summer applications, the efficiency of urea was less (P < 0.05) than that of CAN or NBTPT in all measured parameters, suggesting greater ammonia volatilization loss in urea-treated grass. Nitrogen saved in volatilization improved uptake and responses in NBTPT-treated grass, and hence DMY was not affected compared with CAN in summer fertilizer applications. The results of this study are supportive of increased usage of urea-based fertilizers treated with NBTPT.

Considerations for Recycling of Compost and Biosolids in Agricultural Soil

Regulatory pressures, economic factors and the increasing production of organic waste promote the recycling of compost and biosolids to agricultural land. Sustainable recycling requires an in-depth understanding of the various processes involved when dealing with organic materials. These include interactions in the soil–crop system and the wider environment. The fertiliser value of compost and biosolids depends on the nutrient content of the materials, notably nitrogen, phosphorus and potassium, and their availability to plants. Compost and biosolids constitute slow release fertilisers since most of the nitrogen and phosphorus is not readily available for plant uptake. Furthermore, imbalances in their nutrient composition can negatively affect their agronomic performance. The development of nutrient-enriched biosolids (organomineral fertilisers) appears to be a sustainable alternative for recycling to agricultural land as it deals with the problems associated with nutrient imbalances and release. Further research is necessary to develop suitable techniques for compost nitrogen enrichment in order to improve its nitrogen fertiliser value.