R. Moral

Composting of animal manures and chemical criteria for compost maturity assessment. A review.

New livestock production systems, based on intensification in large farms, produce huge amount of manures and slurries without enough agricultural land for their direct application as fertilisers. Composting is increasingly considered a good way for recycling the surplus of manure as a stabilised and sanitised end-product for agriculture, and much research work has been carried out in the last decade. However, high quality compost should be produced to overcome the cost of composting. In order to provide and review the information found in the literature about manure composting, the first part of this paper explains the basic concepts of the composting process and how manure characteristics can influence its performance. Then, a summary of those factors such as nitrogen losses (which directly reduce the nutrient content), organic matter humification and compost maturity which affect the quality of composts produced by manure composting is presented. Special attention has been paid to the relevance of using an adequate bulking agent for reducing N-losses and the necessity of standardising the maturity indices due to their great importance amongst compost quality criteria.

Co-composting of distillery wastes with animal manures: carbon and nitrogen transformations in the evaluation of compost stability.

The aim of this work was to study the viability of recycling the solid wastes generated by the winery and distillery industry by means of co-composting with animal manures, as well as to evaluate the quality of the composts obtained. Two piles, using exhausted grape marc and cattle manure or poultry manure, respectively (at ratios, on a fresh weight basis, of 70:30), were composted by the Rutgers static pile composting system. Throughout the composting process, a number of parameters were monitored, such as pH, electrical conductivity, organic matter, water-soluble carbon, water-soluble polyphenols, different forms of nitrogen (organic nitrogen, ammonium and nitrate) and humification indices (humification ratio, humification index, percentage of humic acid-like C, polymerisation ratio and cation exchange capacity), as well as the germination index. Organic matter losses followed first-order kinetics equation in both piles, the highest organic matter mineralisation rate being observed with exhausted grape marc and cow manure. On the other hand, the mixture with the lowest C/N ratio, using exhausted grape marc and poultry manure, showed the highest initial ammonium contents, probably due to the higher and more labile N content of poultry manure. The increase in the cation exchange capacity revealed the organic matter humification during composting. In contrast, other humification parameters, such as the humification ratio and the humification index, did not show the expected evolution and, thus, could not be used to assess compost maturity. Composting produced a degradation of the phytotoxic compounds, such as polyphenols, to give composts without a phytotoxic character. Therefore, composting can be considered as an efficient treatment to recycle this type of wastes, due to composts presented a stable and humified organic matter and without phytotoxic effects, which makes them suitable for their agronomic use.

Spent mushroom substrates as component of growing media for germination and growth of horticultural plants.

This research work was conducted in order to investigate the possibility of using spent mushroom substrate (SMS) in the production of horticultural seedlings replacing part of the peat in the growing media. Three vegetable species with different salt sensitivities, the less sensitive being tomato (Lycopersicon esculentum var. Muchamiel), the moderately salt-sensitive being courgette (Cucurbita pepo L. var. Afrodite F1) and the most salt-sensitive being pepper (Capsicum annum L. var. Lamuyo F1) were grown in 12 media containing SMS of two types of mushroom (Agaricus bisporus (SMS-AB) and Pleurotus ostreatus (SMS-PO)) or a mixture of both 50% (v/v) (SMS-50), as well as peat in various ratios. The proportions of each residue in the mixtures elaborated with peat were 25%, 50%, 75% and 100% v/v residue. A substrate of 100% peat was used as control. The experiment was arranged in a completely-randomised design with two replicates per treatment under greenhouse conditions. Prior to sowing, some physical, physico-chemical and chemical properties of the growing media were determined and seed germination and fresh weight of seedling were also measured. In most of the cases, the addition of SMS to the growing media produced an increase in the pH values, salt contents, macro and micronutrient concentrations and a decrease in the water holding capacity contents in comparison to peat, whereas great differences were found in the air capacity values between SMS-based substrates and peat. Up to 75% SMS can be used in mixtures with peat for seed germination of the plant species studied. Regarding the most suitable SMS-based substrates for plant growth, any substrate could be used for tomato seedling production. However, all SMS-AB-based substrates and the media containing low dose of SMS-PO and SMS-50 were adequate for growth of courgette and pepper.

Utilisation of manure composts by high-value crops: safety and environmental challenges.

The intensification in livestock production has increased the need of efficient treatments of waste streams especially to preserve as much as possible, the nutrients into the soil-plant system. Composting is a cheap, efficient and sustainable treatment for solid wastes that is always included in any manure treatment scenario. In this paper, an overview about the environmental and safety challenges of composting of manures is made considering the compost quality requirements established by the main demanding sectors. Co-composting and additive strategies are presented as feasible options for the improvement of compost quality. For quality evaluation of manure compost, the use of both classical and innovative instrumental techniques could increase our knowledge about added properties in compost, especially those related to organic matter stability.

Nitrogen mineralisation potential in calcareous soils amended with sewage sludge

Mineralisation of organic N is an important consideration when determining the annual amount of sewage sludge to be applied to agricultural soils. The mineralisation of sludge organic N was studied in two different textured soils (clayey and sandy soil) treated with aerobic and anaerobic sludge at two different rates (30 and 50 g sludge kg(-1) soil). The mineralisation of sludge organic N was determined during 20 weeks incubation period by analysis of inorganic N produced by a non-leached procedure. Sludge organic N mineralisation was influenced by soil type, organic N mineralisation being greater in the sandy soil (from 30% to 41%) than in the clayey soil (from 13% to 24%). Mineralisation rates decreased rapidly the first two weeks, followed by a slower decrease with time. Although total mineralisation increased with sludge addition rate, net mineralisation decreased with sludge addition rate, probably due to denitrificaton losses. The aerobically treated sludge gave higher mineralisation rates than the anaerobically treated one. The values of N0 and k for treated soils varied depending on the type of sludge and soil.

Soil organic matter and aggregates affected by wildfire in a Pinus halepensis forest in a Mediterranean environment

et Abstract. Three Mediterranean soils located in the north of the Province of Alicante (Spain) were studied for a year after a forest fire. The percentage of water-stable aggregates (between 0.2 and 4 mm) and organic matter content were measured. Microaggregates (< 0.2 mm) were observed using electron microscopy. The results showed the importance of type of forest fire on soil organic matter and aggregates. Soil structure was more affected by surface fire (which affects mainly brushwood and soil surface) than crown fire (which burns the tops of trees and some brushwood). Accumulation of organic matter from burnt trees and brushwood in areas affected by crown fire and alterations in organic matter content through the soil profile were observed. Surface forest fire affected soil structure more negatively than crown fire as observed using electron microscopy. Soils affected by surface fire may be more easily eroded and recovery of vegetation may be delayed because of effects on soil structure. Organic matter content through the soil profile comparing burnt and adjacent unburnt soil could be used to determine the type of fire. Additional keywords: Forest fire; calcareous soil; Spain; Mediterranean type-areas.

Reclamation of a burned forest soil with municipal waste compost : macronutrient dynamic and improved vegetation cover recovery

The reclamation of burned soils in Mediterranean environments is of paramount importance in order to increase the levels of soil protection and minimise erosion and soil loss. The changes produced in the content of total organic carbon (TOC), N (Kjeldahl) and available P, K, Ca and Mg by the addition of different doses of a municipal solid waste compost to a burned soil were evaluated during one year. The effect of organic amendment on the improvement in the vegetation cover after one year was also evaluated. The organic amendment, particularly at a high dose, increased the TOC and N-Kjeldahl content of the soil in a closely related way. The levels of available K in soil were also enhanced by the organic amendment. Although the effects on all three parameters tended to decrease with time, their values in the amended soils were higher than in the control soil, which clearly indicates the improvement in the chemical quality of the soil brought about by the organic amendment. The available P content did not seem to be influenced by organic treatment, while available Mg levels were higher than in the control during the first 4 months following organic amendment. The application of compost to the burned soil improved its fertility and favoured rapid vegetal recovery, thus minimising the risk of soil erosion.

Effects of chromium on the nutrient element content and morphology of tomato

Abstract An hydroponic experiment was conducted to study the effects of chromium (Cr3+) on the distribution of nitrogen (N), phosphorus (P), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), and Cr in the plant, and the growth and yield of a tomato plant. Three Cr treatments were established (0, 50, and 100 mg Cr/L in a nutrient solution). In general, the nutrient element concentration in stems and branches was significantly affected by the Cr treatments. Chromium accumulated preferentially in the roots and low transport was detected to the aerial parts. Growth was diminished due to Cr presence in the nutrient solution. Total yield was not affected, however the number of fruits was diminished and the mean fresh weight of fuit increased with each increment of Cr in the nutrient solution. Chromium was not detected in the edible part (fruit) of the plant.

NUTRIENT VALUE OF ANIMAL MANURES IN FRONT OF ENVIRONMENTAL HAZARDS

The increment of the industrial farms in the Southeast of Spain represents an opportunity to reuse animal manures in arid and semiarid soils, as a source of nutrients and organic matter. However, there are diverse components in their composition potentially dangerous for the environment from the different management activities in the industrial farms, especially heavy metals and salinity. In this experiment, 48 different types of manures from horse, cow, calf, pig, sheep, goat, rabbit, fowl, chicken, ostrich, turkey and earthworm were evaluated on total nutrient content, specially N and P. We also monitored the salt content and the presence of the heavy metals Cd, Hg, Pb, Cr and Ni as main environmental hazards for agricultural soils. We tested a nitric acid digestion for a rapid sample preparation using electro thermal energy (microwave), with very good efficiency on metal recovery.

Influences of winery–distillery waste compost stability and soil type on soil carbon dynamics in amended soils

The application of organic materials to replenish soil organic matter and improve soil structure and fertility has become a common agronomic practice. This research deals with the effects of soil amendment with winery and distillery waste composts on organic carbon (C) mineralisation in two arable soils. A sandy-loam and clay-loam soil were treated and incubated with a number organic materials obtained from the co-composting of different proportions of grape stalk, grape marc, exhausted grape marc and vinasse, with sewage sludge or animal manure. Moreover, the effect of compost stability on C mineralisation dynamics was studied by applying organic materials from different stages of the composting process. The results obtained showed that the addition of exogenous organic matter stimulated microbial growth, enhanced soil respiration and increased water-extractable C contents in both soils, particularly in the days immediately following amendment. The initial composition of the different organic materials used, especially for the mature samples, and the texture of the receiving soil did not influence significantly the C mineralisation final values, with around 11-20% of the added organic C being mineralised over the first 140 days. However, the contribution of organic amendment to the labile organic C pool, maximum rates of soil respiration, as well as the extent of initial disturbance of the soil microbiota were all found to be related to the degree of organic matter stability. Moreover, irrespective of the type and stability of the organic amendment, the mineralogical composition of the receiving soil was found to significantly influence its resilience in such systems.