Evaluating agroforestry interventions in extension projects

Because of the relative dearth of scientific information in agroforestry, monitoring and evaluation of agroforestry technologies in development projects plays an important role in the development and improvement of technical extension recommendations. To identify appropriate methodologies, ICRAF conducted in 1988–89 a review of agroforestry technology monitoring and evaluation in 166 projects worldwide, of which 108 responded. Almost 80% of these were involved in technology evaluation. Many extension projects were conducting research to test technologies on-farm or on research plots. Technology evaluation by projects focused on the biological of trees, often with inadequate consideration of the technology context. Few projects seemed to use farmer assessment in evaluation. Recommendations are made for an effective evaluation process and selection of appropriate methods and variables to be assessed by projects. Methods should be selected according to the availability of resources and should favour collaborative or collegial interaction between farmers and project staff.     

Ascorbic acid, carotenoids, and visual quality of baby spinach as affected by shade netting and postharvest storage

Baby spinach ( Spinacia oleracea L.) was grown under three types of shade netting (high transmittance, spectrum-altering, and low transmittance) to study the effect on the concentrations of vitamin C (ascorbic acid and dehydroascorbic acid), carotenoids, and chlorophyll and on the visual quality of the leaves. The spinach was sown in April and August and harvested at two growth stages. After harvest, leaves were stored in polypropylene bags at 2 and 10 degrees C. Shading significantly decreased the ascorbic acid concentration of April-sown spinach by 12-33%, but in the August-sown spinach, the response was inconsistent. Concentrations of total carotenoids and total chlorophylls were significantly higher under the nettings in many cases, especially under the spectrum-altering and low-transmittance nettings. Postharvest visual quality and postharvest persistence of the compounds analyzed were not greatly affected by shading. We conclude that these shade nettings are acceptable to use in baby spinach production when it comes to the studied aspects of internal and external quality of the produce.     

BODIUM—A systemic approach to model the dynamics of soil functions

The increasing demand for biomass for food, animal feed, fibre and bioenergy requires optimization of soil productivity, while at the same time, protecting other soil functions such as nutrient cycling and buffering, carbon storage, habitat for biological activity and water filter and storage. Therefore, one of the main challenges for sustainable agriculture is to produce high yields while maintaining all the other soil functions. Mechanistic simulation models are an essential tool to fully understand and predict the complex interactions between physical, biological and chemical processes of soils that generate those functions. We developed a soil model to simulate the impact of various agricultural management options and climate change on soil functions by integrating the relevant processes mechanistically and in a systemic way. As a special feature, we include the dynamics of soil structure induced by tillage and biological activity, which is especially relevant in arable soils. The model operates on a 1D soil profile consisting of a number of discrete layers with dynamic thickness. We demonstrate the model performance by simulating crop growth, root growth, nutrient and water uptake, nitrogen cycling, soil organic matter turnover, microbial activity, water distribution and soil structure dynamics in a long-term field experiment including different crops and different types and levels of fertilization. The model is able to capture essential features that are measured regularly including crop yield, soil organic carbon, and soil nitrogen. In this way, the plausibility of the implemented processes and their interactions is confirmed. Furthermore, we present the results of explorative simulations comparing scenarios with and without tillage events to analyse the effect of soil structure on soil functions. Since the model is process-based, we are confident that the model can also be used to predict quantities that have not been measured or to estimate the effect of management measures and climate states not yet been observed. The model thus has the potential to predict the site-specific impact of management decisions on soil functions, which is of great importance for the development of a sustainable agriculture that is currently also on the agenda of the ‘Green Deal’ at the European level.     

Effects of agricultural management on nematode–mite assemblages: Soil food web indices as predictors of mite community composition

Biological indicators based on abundances of soil organisms are powerful tools for inferring functional and diversity changes in soils affected by agricultural perturbations. Field plots, combining organic and conventional practices with no tillage, conservation tillage and standard tillage maintained different nematode assemblages and soil food webs. Soil food web indices based on nematode assemblages were reliable predictors of the trophic composition of functional characteristics of soil mite assemblages. Bacterial-feeding and predatory nematodes, together with predatory mites, were abundant in the organic-no till treatments and were associated with high values of the Enrichment and the Structure Index based on nematode assemblages. Conventional-Standard tillage treatments had high abundances of fungal- and plant-feeding nematodes and algivorous mites, associated with high values of the Basal and Channel Index. This study validates the hypothesis that nematode-based soil food web indices are useful indicators of other soil organisms such as mites, with similar functional roles and environmental sensitivities.     

Soil organic C variability and microbial functions in a Mediterranean agro-forest ecosystem

Five soils characterised by different agro-forest managements, typical of Mediterranean environment and with increasing human impact were chosen in Sardinia (Italy): two vineyards with different management systems, a rotation hay crop-pasture and a forest (Quercus suber L.). The study aimed to investigate the relationships between C storage and microbial functionality in soil under different managements. Pools of total organic C and microbial biomass C were determined, as well as the loss of organic C due to microbial respiration (basal and cumulative) and several microbial indices (metabolic, mineralization, and microbial quotient) as indicators of the microbial efficiency in the use of energy and the degree of substrate limitation for soil microbes. Enzymes were chosen on their relevance in the C (β-cellobiohydrolase, N-acetyl-β-glucosaminidase, β-glucosidase, α-glucosidase), N (leucine aminopeptidase), S (arylsulphatase) and P (acid phosphatase) cycling and were used as indicators of functional diversity in soil. Organic C pools and enzyme activities on average increased noticeably in soils with a lower human impact showing the highest values in forest and the lowest in the vineyards, following the trend of organic matter availability. The trend in functional diversity reflected the increase of microbial pool and organic C availability: the vineyards showed a lower Shannon’s diversity index, whilst pasture and forest sites reached the maximum levels of functional diversity. These soils showed an increase of microbial efficiency in the use of available resources and the decrease of substrate limitation for soil microbes.     

Interaction of contaminated sediment from a salt marsh with estuarine water: evaluation by leaching and ecotoxicity assays and salts from leachate evaporation

Purpose

Wastes from a former Portuguese steel plant were deposited between 1961 and 2001 on the riverbank of a tributary of the Tagus River creating a landfill connected to the river, posing a potential contamination risk to the Tagus estuary ecosystem. This study aims to assess the transfer of chemical elements from contaminated sediments to the estuarine water from cycles of sediment leaching so as to evaluate the ecotoxicity of the leachates, and to analyze the solid phases crystallized from those leachates.

Materials and methods

Landfill sediment and estuarine water samples were collected during low tide. Sediment samples were analyzed for pH, electric conductivity (EC), C_org, NPK, and iron oxides. Leaching assays (four replicates) were done using estuarine water (200 cm³/replicate) and 1.5 kg of sediment per reactor. Each reactor was submitted to four leaching processes (0, 28, 49, and 77 days). The sediment was kept moist between leaching processes. Sediment (total (acid digestion) and available fraction (diluted organic acid extraction-Rhizo)) elemental concentrations were determined by inductively coupled plasma–instrumental neutron activation analysis (ICP/INAA). Leachates, and estuarine and sediment pore waters were analyzed for metals/metalloids by ICP/mass spectrometry (MS) and carbonates/sulfate/chloride by standard methodologies. Ecotoxicity assays were performed in leachates and estuarine and pore waters using Artemia franciscana and Brachionus plicatillis. Aliquots of the leachates were evaporated to complete dryness (23–25 °C) and crystals analyzed by X-ray powder diffraction (XRD).

Results and discussion

Sediment with pH?=?8 and high EC and C_org was contaminated with As, Cd, Cr, Cu, Pb, and Zn. The element concentrations in the available fraction of the sediment were low compared to the sediment total concentrations (<1 % for Rhizo extraction). The concentrations of potentially hazardous elements in the estuarine water were relatively low, except for Cd. Concentrations of hazardous elements in the leachates were very low. Calcium, K, Mg, Na, and chloride concentrations were high but did not vary significantly among the four leaching experiments. Total concentrations of carbonate were much higher in leachates than in estuarine water. Both estuarine water and leachates showed negligible toxicity. Crystals identified in the solids obtained from the leachates by evaporation were halite, anhydrite, epsomite, dolomite, and polyhalite.

Conclusions

The sediment showed the capacity to retain the majority of the potentially hazardous chemical elements. Remobilization of chemical elements from sediment by leaching was essentially negligible. The variation of total concentrations of Ca, carbonate, and sulfate in leachates indicates that the sediment contained reactive sulfides. Due to its composition, the sediment seems to be a dynamic system of pollution control, which should not be disturbed.

     

Interlaboratory evaluation of a real-time multiplex polymerase chain reaction method for identification of salmon and trout species in commercial products

This interlaboratory study evaluated a real-time multiplex polymerase chain reaction (PCR) method for identification of salmon and trout species in a range of commercial products in North America. Eighty salmon and trout products were tested with this method by three independent laboratories. Samples were collected in the United States and Canada, and only the collecting institution was aware of the species declaration. Following analysis with real-time PCR, all three laboratories were able to identify species in 79 of the 80 products, with 100% agreement on species assignment. A low level of fraud was detected, with only four products (5%) found to be substituted or mixtures of two species. The results for two of the fraudulent products were confirmed with alternate methods, but the other two products were heavily processed and could not be verified with methods other than real-time PCR. Overall, the results of this study show the usefulness and versatility of this real-time PCR method for the identification of commercial salmon and trout species.