International Journal of Recycling of Organic Waste in Agriculture
Volume:9 Issue: 2, Spring 2020

Purpose A combined treatment of composting and vermicomposting of poultry litter (PL), rice hulls (RH) and/or eucalyptus sawdust (ES) was carried out in order to obtain a high-quality organic fertilizer and avoid the environmental problems associated with the use of raw poultry manure and fresh agricultural waste materials. Methods Three composting mixtures were made at volume proportions: 1:3 RH/PL (M1); 1:2 ES/PL (M2) and 0.5:1:2 RH/ES/PL (M3). Composting (120 days) followed by vermicomposting (90 days) using earthworms (Eisenia fetida) were conducted during the autumn-winter season, outdoors and sheltered. Moisture content was kept at 60-70%. Physicochemical (pH, electrical conductivity, lignin, total carbon and nitrogen, organic matter, ammonium and specific cations), total microbial activity (fluorescein diacetate hydrolysis) and microbiological parameters were recorded throughout both processes. Phytotoxicity tests were lastly performed by means of Lactuca sativa, L. seed germination, to compare the quality of the organic fertilizers obtained. Results A sequential compost-vermicompost process enhanced the properties of the final products. Particularly, electrical conductivity was markedly lower in all vermicomposts (1.81-2.28 mS cm-1) and within the values recommended for the growth of sensitive plants; microbial activity reached 187.1-203.8 µg FDA gsoil-1 h-1. Germination Index values in vermicomposts were greater than 60%, indicating the high quality of the products obtained, being the mixture 0.5RH:1ES:2PL, the one which showed better quality and higher maturation degree. Conclusion The system that combines both processes (composting+vermicomposting) was effective to produce a stabilized organic fertilizer from poultry litter with other waste organic materials.

Purpose This research aimed to evaluate the yield and quality of granular NPK fertilizers prepared by physical granulation with eggshell, snail shell, and cow bone as fillers and to compare them to conventional filler. Methods Urea, DAP, KCl, and fillers were milled separately and mixed to the desired formula. About 150 g of mixed powders were granulated on a disc granulator in 9 minutes, at a rotation speed of 35 rpm and a disc slope of 45°. Water at a desired additional moisture was sprayed on the tumbled powders to facilitate the granulation. The obtained granules were then dried and screened into three fractions: undersize ( 4 mm). Results Snail shells and eggshells as fillers were found to give on-size NPK granules having yield and compressive strength which were comparable to that with limestone as a conventional filler. For NPK 15-15-15, using snail shells and eggshells as fillers, the yields of on-size granules achieved 46% and 56%, respectively, and the compressive strengths of on-size granules reached 2.4 and 2.1 MPa, respectively. Cow bones as fillers resulted in low compressive strength. The distribution of nutrients in the NPK granules was found to be close to the targeted formula. Conclusion Snail shells and eggshells as fillers have good yield and quality of on-size NPK granules and are very potential alternatives to limestone.

Purpose Vinasse is produced in large quantities as a by-product from bioethanol production. To ensure environmental sustainability, a beneficial use was sought. Previous study showed that short-term crops grown with vinasse-amended soil provided higher yield than crops treated with chemical NPK (15:15:15) fertilizer. To understand this phenomenon, this study sought to establish the nutrient release rates of vinasse in the agricultural soils of Guyana. Methods Soils representative of the three most common and one futuristic agricultural land in Guyana were fertilized with vinasse, then watered as with normal course of plant growth of cash-crops for twelve weeks. The soil was sampled periodically, and the soil nutrients were determined. Results The nutrient availability from the application of vinasse as a soil amendment was greater for the clay soils than the sandy soil. EC was high while there was high availability of N, Ca, Mg, Fe and Mn during the 6-12th week. There was no discernable trend for tiwiwid sand. Conclusion In this laboratory study, high nutrient availability was observed in weeks 6-12 for the three clay soils studied. This period is the fruit and foliage growth phase for most short-term crops; hence, this suggests that vinasse is a good soil amendment for short-term crops in these soils. Vinasse did not improve the fertility of sandy soils; hence, it would be unsuitable as a fertilizer source in the Intermediate Savannahs of Guyana. Further studies should be done to fully determine the soil nutrient dynamics and the nutrient uptake.

Purpose This study performed a feasibility assessment of nitrogen enrichment by some organic wastes through vermicomposting as well as its release as a bioavailable form over time. Methods Soybean and canola wastes as well as the dairy blood powder of industrial slaughterhouse were used as organic wastes to enrich the vermicompost. Composted materials were incubated for nitrogen mineralization kinetic assessment by adjusting moisture content to 50% at 30 ˚C for 80 days. During the incubation, moisture was maintained by weighing. Subsamples were collected after 1, 5, 10, 20, 40, 60, and 80 days of incubation. Results Among the treatments, those for 25% dairy blood powder contained the highest nitrogen content (4.95 and 3.70% for chicken and cow blood powder, respectively). Nitrogen mineralization through 80 days of incubation ranged from 2.23% (for 50% canola waste treatment) to 2.57% (for 25% blood powder) of the total nitrogen. The mineralization rate ranged from 4.24 and 3.62 mg kg-1 day-1 for the compost containing 25% chicken and cow blood powder, respectively, to 0.94 and 0.84 mg kg-1 day-1 in canola and soybean waste, respectively, whereas those for the control treatment equaled 0.81 mg kg-1 day-1. Conclusion Composts containing 25% blood powder were acceptable in terms of quantity and nitrogen release over time, and can serve as a reliable source of available nutrients in the soil.

Purpose The overharvesting of the endemic palm tree Euterpe edulis Mart. (Arecaceae) from the Brazilian Atlantic Forest hotspot and the destination given to the sludge produced from urban sewage treatment are both serious environmental issues caused by human activities. In order to find solutions or alternatives for both the issues, we aimed to investigate the effect of increasing rates of a sewage sludge organic fertilizer (SSOF), produced by composting sewage sludge and solid waste, on the initial growth of E. edulis. Methods We mixed sand with 0, 62.5, 125, and 250 kg·m−3 of SSOF in 8 L (21 cm height × 24 cm top diameter × 20.5 cm base diameter) pots and then planted a seedling of E. edulis in each pot. We assessed the seedlings’ height and stem diameter relative growth rate (RGR), biomass, root to shoot ratio, and shoot macronutrient (nitrogen, phosphorous, potassium, calcium, magnesium, and sulphur) concentrations in relation to fertilizer levels. We also evaluated the relation between plant height and diameter over time for each fertilization level. Results We found that height and stem diameter RGRs, biomass accumulation, and N and P shoot concentrations of E. edulis were positively related to SSOF levels between 120 and 250 kg·m−3 in the substrate. Conclusions Our study demonstrates that SSOF can be further used as an alternative to sewage sludge disposal and contribute to E. edulis cultivation, and, hence, its conservation.

Purpose Bacterial and fungal communities represent key bioindicators of soil quality and are essential for the maintenance of nutrient availability. Our purpose was to characterize the bacterial and fungal biodiversity associated with different compost mixtures, comparing microbiological indicators regarding the soil quality. Methods Compost samples and mixtures were prepared (15:1 final ratio) with chemical fertilizer, animal manures (bovine, swine, and poultry) and green waste (such as tomato waste and leaves). Bacterial and fungal isolation and identification were performed through standard phenotypic methods. Statistical methods to assess differences between treatments included Shannon diversity, Chi-square tests, Bray-Curtis clustering, and Canonical Correspondence Analysis. Results Streptomyces species, Gram-positive bacteria, were commonly found in differing abundances in all samples. Gram-positive species were predominant in soils amended with vegetable green waste while Gram-negative bacteria were more abundant in samples with chemical fertilizer. Fungal abundance increased in poultry manure and chemical fertilizers. Conclusion Our findings suggested that organic matter recycling and composting resulted in the shifting of biodiversity in bacterial and fungal populations which might be associated with the availability of certain nutrient sources provided by the composting materials.

Purpose To comply with purposes of circular economy and sustainability, as well as promoting an appropriate destination for waste from Bactris gasipaes agro-industry and adding value to this product, we evaluated the compost of the plant residue as substrate for seedlings production. Methods Waste was collected, composted, dried and ground. Compost samples were characterized chemically and physically. The treatments consisted of different proportions of compost and soil (medium commonly used in B. gasipaes seedling nurseries), to make five growth media (v:v composted peach palm:soil): T1 - 100: 0; T2 - 75:25; T3 - 50:50; T4 - 25:75 and T5- 0: 100. After 120 days of planting the peach palm seedlings, morphological parameters were evaluated. Results  For the majority of physicochemical properties, T1 showed superior characteristics, i.e. higher water retention capacity (74.19 v/v), higher total porosity (74.78%) as well as higher concentrations of N, P, K (with 2.90 %, 3412.00 g dm-3 and 7120.00 g dm-3, respectively) when compared to T5. Likewise, for seedling morphological parameters, the material grown in T1 presented higher height and shoot fresh and dry weight. Conclusion  B. gasipaes residue compost shows adequate amounts of macro and micronutrients and physical properties that enable satisfactory development of seedlings from the species, thus promoting a self-sustainable seedling production system.

Purpose In recent years, attempts have been made to compensate irrigation water shortage through widespread wastewater application as a low-quality water resource for agriculture. The existing wastewater treatment plants do not have sufficient capacity to treat such a huge volume of wastewater. In arid and semiarid region, soil type as well as climate is different from the others, so the aim of this paper is the review of literature on the effects of wastewater reuse in agriculture. Methods An extensive literature review was conducted to evaluate urban wastewater effects on soil, plant and environment. Results One of the best methods for wastewater disposal is wastewater discharge into the soil. However, as it was revealed in this research, in most cases, this method would lead to increased salinity, SAR, organic matter content, permeability, and electric conductivity as well as reduced soil bulk density. Nevertheless, wastewater effect on soil physical properties depends on its characteristics and also its application period. For instance, in durations less than one year, wastewater has often no significant effect on some soil properties such as bulk density. The best wastewater usage approach is utilizing drip irrigation method, which can overcome the shortcomings resulted from its application. In most studies carried out in this field, wastewater irrigation has led to increased accumulation of heavy elements and nutrients in the soil and even sometimes in under-cultivation plants. It is noteworthy that these elements' accumulation in the fruit section is less than their accumulation in the vegetable part of the plants. Conclusion The use of wastewater without accurate management can extremely cause adverse environmental outcomes, including soil salinization, soil degradation, reduced soil hydraulic conductivity, soil hydrophobicity, poisoning, reduced yield of the crops, and surface/groundwater resources' contamination, and eventually the prevalence of diseases. Consequently, in order to reuse wastewater for agriculture, microbial contamination' reduction should be seriously considered in accordance with the standards determined by the Environmental Protection Agency or the World Health Organization guidelines. It is highly emphasized that after reaching the required standards, the wastewater can be used for irrigation. In conclusion, Pharmaceuticals presence in the wastewater are a growing global concern.

Purpose Sorption could be a way to concentrate nutrients in diluted waste streams to bring more nutrients back to agriculture. The aim of this work was to model the fate of sorbed NH4+ content in liquid waste streams by adding nitrogen (N) sorbed to a sorbent, zeolite, and study its effect on early growth and potential leaching losses. Methods A pot experiment with two soil types and wheat as test crop was conducted. Mineral N in soil was measured, and a leaching experiment performed. 15N labelled ammonium was sorbed to zeolite. The fertilizer effect was then compared to ammonium fertilizer applied the conventional way, with and without zeolite. Results Early uptake of sorbed ammonium was reduced by 56% compared to ammonium applied conventionally, and soil uptake compensated only very early. Nitrate concentration in leachates was reduced by 12% in sandy soil when N was applied sorbed to zeolite. However, leaching of water through the profile increased 71% when N was applied sorbed to zeolite, so that there was only a tendency to lower N losses when N was applied sorbed to zeolite. Conclusion Ammonium-N sorbed to zeolite is less plant available than conventionally applied N but may also be less prone to leaching losses.