Luis Miguel Brito

Methods to improve the composting process of the solid fraction of dairy cattle slurry

Cattle slurry solid fraction (SF) with different dry matter (DM) contents was collected from two dairy farms and composted in static and turned piles, with different sizes and cover types, to investigate the effects of pile conditions on the physical and chemical changes in SF during composting and to identify approaches to improve final compost quality. Thermophilic temperatures were attained soon after separation of SF, but the temperature of piles covered with polyethylene did not increase above 60 degrees C. The rate of organic matter (OM) mineralisation increased for turned piles in comparison to static piles, but the maximum amount of mineralisable OM (630-675gkg(-1)) was similar for all pile treatments. The C/N ratio declined from over 36 to a value of 14 towards the end of composting, indicating an advanced degree of OM stabilisation. Mature compost was obtained from raw SF feedstock as indicated by the low compost temperature, low C/N ratio, and low content of NH(4)(+) combined with increased concentrations of NO(3)(-). The efficiency of the composting process was improved and NH(3)-N losses were minimized by increasing DM content of the SF, reducing the frequency of pile turning and managing compost piles without an impermeable cover.

Simple technologies for on-farm composting of cattle slurry solid fraction.

Composting technologies and control systems have reached an advanced stage of development, but these are too complex and expensive for most agricultural practitioners for treating livestock slurries. The development of simple, but robust and cost-effective techniques for composting animal slurries is therefore required to realise the potential benefits of waste sanitation and soil improvement associated with composted livestock manures. Cattle slurry solid fraction (SF) was collected at the rates of 4m(3)h(-1) and 1m(3)h(-1) and composted in tall (1.7 m) and short (1.2m) static piles, to evaluate the physicochemical characteristics and nutrient dynamics of SF during composting without addition of bulking agent materials, and without turning or water addition. Highest maximum temperatures (62-64 °C) were measured in tall piles compared to short piles (52 °C). However, maximum rates of organic matter (OM) destruction were observed at mesophilic temperature ranges in short piles, compared to tall piles, whereas thermophilic temperatures in tall piles maximised sanitation and enhanced moisture reduction. Final OM losses were within the range of 520-660 g kg(-1) dry solids and the net loss of OM significantly (P<0.001) increased nutrient concentrations during the composting period. An advanced degree of stabilization of the SF was indicated by low final pile temperatures and C/N ratio, low concentrations of NH(4)(+) and increased concentrations of NO(3)(-) in SF composts. The results indicated that minimum intervention composting of SF in static piles over 168 days can produce agronomically effective organic soil amendments containing significant amounts of OM (772-856 g kg(-1)) and plant nutrients. The implications of a minimal intervention management approach to composting SF on compost pathogen reduction are discussed and possible measures to improve sanitation are suggested.

Co-composting of invasive Acacia longifolia with pine bark for horticultural use

The feasibility of commercial-scale co-composting of waste biomass from the control of invasive Acacia species with pine bark waste from the lumber industry, in a blend ratio of 60:40 (v:v), was investigated and compared with previous research on the composting of Acacia without additional feedstock, to determine the potential process and end-product quality benefits of co-composting with bark. Pile temperatures rose rapidly to >70 °C and were maintained at >60 °C for several months. Acacia and bark biomass contained a large fraction of mineralizable organic matter (OM) equivalent to approximately 600 g kg−1 of initial OM. Bark was more recalcitrant to biodegradation compared with Acacia, which degraded at twice the rate of bark. Therefore, incorporating the bark increased the final amount of compost produced compared with composting Acacia residues without bark. The relatively high C/N ratio of the composting matrix (C/N = 56) and NH3 volatilization explained the limited increases in content, whereas concentrations of conservative nutrient elements (e.g. P, K, Ca, Mg, Fe) increased in proportion to OM mineralization, enriching the compost as a nutrient source for horticultural use. Nitrogen concentrations also increased to a small extent, but were much more dynamic and losses, probably associated with N volatilization mechanisms, were difficult to actively control. The physicochemical characteristics of the stabilized end-product, such as pH, electrical conductivity and OM content, were improved with the addition of bark to Acacia biomass, and the final compost characteristics were suitable for use for soil improvement and also as horticultural substrate components.

Physicochemical Dynamics of Composting Screw Pressed Cattle Slurry Amended with Italian Ryegrass Straw or Gorse Bulking Agents

Cattle slurry solid fraction (SF) was composted with increasing rates (0, 25, 33 and 50% v/v) of either Italian ryegrass (Lolium multiflorum L.) straw or gorse (Ulex europaes) to determine the effects of these bulking agents on the physicochemical properties during the composting process and to identify approaches to improve final compost quality. Composting temperatures increased to a maximum of 65°C after 42 days for unamended SF. In contrast, temperatures increased more rapidly in piles mixed with straw (68°C at day 7) or with gorse (74°C at day 3). Gorse or straw addition to SF, therefore, also increased the initial rates of organic matter mineralization. However, potential organic matter (OM) mineralization and compost N concentration decreased with the addition of the bulking agents. C/N ratios declined from 32-38 to a value of 13-17 towards the end of composting and followed a similar trend for all compost treatments. Low compost temperature, low C/N ratio and the small content of NH4+ combined with increased concentrations of NO3− indicated SF composts were stabilized and suitable for use in agriculture. High concentrations of OM (780-840 g kg−1 dry matter (DM)) and total N (28-35 g kg−1 DM), and low electrical conductivity (0.7-1.2 dS m−1) suggested that SF composts would be effective soil amendments with agronomic and environmental advantages. The addition of straw or gorse also enhanced compost sanitation.

Use of Acacia Waste Compost as an Alternative Component for Horticultural Substrates

The rising cost of peat and pine bark has boosted the demand for alternative organic materials for container growing media. Here, composts of invasive acacia (Acacia longifolia and Acacia melanoxylon) residues were evaluated as alternative organic materials for horticultural substrates. Compost bulk density was less than 0.4 g cm−3 and total pore space was more than 85 percent of the total volume, as established for an ideal substrate. The matured acacia compost air capacity, easily available water, buffering capacity, and total water-holding capacity were also within acceptable recommended values. With increased composting time the physical characteristics of the composts were improved, but the same was not true for chemical characteristics such as pH and electrical conductivity. The replacement of pine bark compost by acacia compost in a commercial substrate did not negatively affect either lettuce emergence or lettuce growth, suggesting that acacia compost can be successfully used as an alternative component for horticultural substrates.

Organic Lettuce Growth And Nutrient Uptake Response To Lime, Compost And Rock Phosphate

Fertilizer recommendations are needed to increase organic vegetable yields. Thus, organic lettuce growth and nutrient uptake was investigated in a randomized block pot experiment with twelve treatments from the factorial structure of three factors: (i) Gafsa phosphate [0 and 200 kg phosphorus pentoxide (P2O5) ha−1], (ii) compost from source separated municipal organic waste (0, 15, and 30 t ha−1) and (iii) limestone [0 and 8 t ha−1 calcium carbonate (CaCO3) equivalent]. Lettuce yield increased with compost application and a first order interaction between lime and phosphate was clear because lime partially replaced the need for phosphate. This was explained by the effect of liming on P availability in acid soils. Nitrogen (N), phosphorus (P), and potassium (K) accumulation increased in lettuces produced with compost or phosphate but only the accumulation of N was increased with lime. This compost is recommended to increase nutrient availability for organic lettuce whereas the need for phosphate fertilization may decrease with liming.

Composting for management and resource recovery of invasive Acacia species

The feasibility of commercial-scale composting of waste biomass from the control of invasive Acacia species was investigated. Pile temperatures exceeded 65ºC for several months, indicating that the composting process was effective at pathogen inactivation and seed destruction. Mineralisation of Acacia biomass was described by a two-component, first-order exponential model; the pool sizes for labile and recalcitrant organic matter (OM) were similar and in the approximate ranges: 360–410 g kg-1 and 350–390 g kg-1 of initial OM, respectively. Concentrations of conservative nutrients increased proportionally to OM mineralisation, enriching the compost as an agricultural nutrient source. Nitrogen concentrations also increased, but were more dynamic as nitrogen losses were difficult to control, although we suggest that they may be potentially minimised by restricting the turning frequency. The physicochemical characteristics of the stabilised end-product, and the high OM content and low electrical conductivity (<1.2 dS m-1), in particular, were suitable for soil improvement or as substrate components.

Analysis of physical and chemical characteristics of commercial substrates and comparison with a compost of organic waste

Por razones ambientales existe una presion creciente para reducir el uso de turba como sustrato y aumentar el uso de materiales de deshecho, como residuos organicos que a menudo se encuentran en los vertederos. En este estudio fueron comparadas las caracteristicas fisico-quimicas de 16 sustratos comerciales con las de un compost de residuos solidos urbanos con la fraccion organica separada, con diferentes periodos de maduracion., para determinar las limitaciones del compost como componente del sustrato y sugerir ajustes en la composicion para conseguir caracteristicas mas adecuadas en el compost final. La principal limitacion del compost como componente del sustrato es la baja relacion C/N, bajo contenido en humedad, elevado pH y altos valores de conductividad electrica, asi como contenidos muy altos de amoniaco, sodio y potasio. Estas limitaciones pueden ser minimizadas con la seleccion de materias primas para el proceso de compostaje con el aumento de la relacion C/N y la disminucion de la conductividad electrica y manteniendo el contenido de humedad del compost durante el periodo de maduracion, para incrementar la mineralizacion de la materia organica restante y la nitrificacion del amoniaco.

Perceived changes in well-being and happiness with gardening in urban organic allotments in Portugal

ABSTRACT Urban allotment gardens (AG) in Portugal have increased in recent years, as in many other European countries and worldwide. The contribution of these gardens to the happiness and well-being of urban populations has been recognized, but evaluations of their benefits are still very scarce. The objective of this study was to evaluate this contribution, based on the urban organic AG of the Devesa Park in Vila Nova de Famalicão, Portugal. The sample included 65 gardeners who completed the self-administered questionnaires of Bem-Estar Pessoal (personal well-being scale), Felicidade Subjetiva (subjective happiness scale) and sociodemographic characteristics. Respondents were mainly adults under 65 years, married and academically well qualified and about half of them had a professional activity, with nearly one third being retired. They considered themselves happy with their life (Personal Well-being Index = 74.5%) and revealed an optimistic and positive attitude towards life, regardless of economic or social difficulties. The increased frequency of visits for gardening was positively related to a greater perception of subjective happiness. The gardeners who visited the AG more frequently considered themselves happier from a self-perspective and in comparison with peers. It can be suggested that urban organic AG represent a means for enhancing citizen well-being, contributing positively to their feelings of happiness and life satisfaction, changing behaviours and developing personal capacities. Beyond economic measures, urban AG can be recommended to capture the well-being of societies.

Organic production of horticultural crops with green manure, composted farmyard manure and organic fertiliser

Abstract A three-year organic crop rotation was set up in a field with sandy loam soil, with a cover crop of rye and vetch grown over the three autumn/winter seasons for green manure, followed by potato and lettuce (1st year), Swiss chard and turnip (2nd year), and Portuguese cabbage and carrot (3rd year). Nitrogen (N) mineralisation was determined by field incubation in response to green manure (GM), GM with 20 and 40 t ha−1 farmyard manure (FYM) compost (C20 and C40) and GM with 1 and 2 t ha−1 of commercial organic fertiliser (CF1 and CF2). The second season crops (lettuce, turnip and carrot) yields were higher for the treatment C40 compared to all other treatments because most of the commercial fertiliser was mineralised during the previous crop. Swiss chard, grown in a short season (54 days), produced higher yield for CF2 compared with C40. However, this was not true for potato (1st year), probably because of increased compost mineralised N recovery during the longer growing season for the potatoes (124 days), nor for the cabbage (3rd year), which had a short growing season (56 days), because of increased N availability with continuous compost and green manure application. This study highlighted that field incubation can be used to assess mineralisation rates and that the fast N release of commercial fertilisers increased the yield of the first crop of the year, whereas the slowly released N of FYM compost increased yield of both crops of the year, with lower risk of N loss.