Bert Reubens

Opportunities and barriers to on-farm composting and compost application: A case study from northwestern Europe.

Maintaining and increasing soil quality and fertility in a sustainable way is an important challenge for modern agriculture. The burgeoning bioeconomy is likely to put further pressure on soil resources unless they are managed carefully. Compost has the potential to be an effective soil improver because of its multiple beneficial effects on soil quality. Additionally, it fits within the bioeconomy vision because it can valorize biomass from prior biomass processing or valorize biomass unsuitable for other processes. However, compost is rarely used in intensive agriculture, especially in regions with high manure surpluses. The aim of this research is to identify the barriers to on-farm composting and the application of compost in agriculture, using a mixed method approach for the case of Flanders. The significance of the 28 identified barriers is analyzed and they are categorized as market and financial, policy and institutional, scientific and technological and informational and behavioral barriers. More specifically, the shortage of woody biomass, strict regulation, considerable financial and time investment, and lack of experience and knowledge are hindering on-farm composting. The complex regulation, manure surplus, variable availability and transport of compost, and variable compost quality and composition are barriers to apply compost. In conclusion, five recommendations are suggested that could alleviate certain hindering factors and thus increase attractiveness of compost use in agriculture.

A sociopsychological analysis of agroforestry adoption in Flanders: understanding the discrepancy between conceptual opportunities and actual implementation

ABSTRACT While the opportunities of modern agroforestry systems are increasingly recognized by policymakers, consultants, researchers, and educators, the response of farmers to the recent subsidy program for alley cropping systems in Flanders is relatively low. Therefore, in this study, a mixed method technique, including a survey (n = 86), interviews (n = 33), and a GIS analysis, is used to better understand the reasons behind this implementation gap. The study showed that 55% of the Flemish farmers are not familiar with agroforestry and that the intention to engage in agroforestry is very low. As a result, alley cropping in Flanders remains sparse with only around 30 farmers known to be consciously engaged in the practice. In the last couple of years, these pioneers have installed one or more agroforestry plots (average surface area of 2.3 ha) that often combine a variety of trees with grassland. Whereas negative perceptions of Flemish farmers are mainly related to compatibility and profitability of such a farming system, pioneers consider legal issues, such as land tenure, the most pertaining drawback. Therefore, future research and policy and extension efforts should target these aspects in order to enhance further diffusion.

Potential of chopped heath biomass and spent growth media to replace wood chips as bulking agent for composting high N-containing residues

We investigated the potential of C-rich byproducts to replace wood chips as bulking agent (BA) during composting. The impact of these alternatives on the composting process and on compost stability and characteristics was assessed. Three BA (chopped heath biomass and spent growth media used in strawberry and tomato cultivation) were used for processing leek residues in windrow composting. All BA resulted in stable composts with an organic matter (OM) content suitable for use as soil amendment. Using chopped heath biomass led to high pile temperatures and OM degradation and a nutrient-poor compost with high C/P ratio appropriate for increasing soil organic carbon content in P-rich soils. Spent substrates can replace wood chips, however, due to their dense structure and lower biodegradation potential, adding a more coarse BA is required. Generally, the nutrient content of the composts with growth media was higher than the composts with wood chips and chopped heath biomass.

Field storage conditions for cattle manure to limit nitrogen losses and optimise fertiliser value

Storage and application of cattle farmyard manure (CFM) can cause considerable environmental problems through nutrient losses to soil, water and air, if not properly handled. We investigated different storage conditions of CFM at field scale to reduce nitrogen (N) losses to the soil, meanwhile optimising the agronomical quality of the CFM. The treatments differed in terms of storage method (stockpiling, extensive composting or co-composting with bulking agents) and coverage (no cover, plastic or geotextile cover). Over the different treatments, the ammonium-N concentrations under the piles in the 0–90 cm soil layer amounted to a maximum of 4.2% of the initial manure N content. We were able to assess the relative importance of each of the two processes resulting in a higher mineral N concentration under the piles, i.e. direct leaching from the CFM to the soil on the one hand, and a smaller indirect effect of elevated soil temperatures (up to 37°C) under the piles resulting in higher N mineralisation in the top soil on the other hand. NH4+-N was the most important component of mineral N under all heaps due to limited oxygen diffusion to the soil. N leaching and end-product quality were affected by a combination of treatment option (i.e. storage and cover) and initial manure characteristics. When CFM was characterised by a low volumetric moisture content and high C : N ratio, so in case of straw-rich CFM or CFM with added bulking agents, composting led to the least N leaching and most stable end product. When CFM was characterised by a high volumetric moisture content and low C : N ratio, stockpiling and covering (plastic or geotextile) resulted in lower N leaching to the soil. Stockpiling and covering the CFM with a geotextile resulted in a more stable end product than did covering with a plastic.

Monitoring the Impact of Hedgerows and Grass Strips on the Performance of Multiple Ecosystem Service Indicators

The importance of semi-natural vegetation elements in the agricultural landscape is increasingly recognized because they have the potential to enhance multiple ecosystem service delivery and biodiversity. However, there is great variability in the observed effects within and between studies. Also, little is known about the simultaneous delivery of multiple ecosystem services and biodiversity because most studies focus on monitoring one service at a time and in conditions specifically suited to observe this one service. In this study, the results are presented of 1 year of monitoring of a set of parcel-level and simplistic ecosystem service and biodiversity indicators on parcels with grass strips or hedgerows. In the grass strips, an increase in soil organic carbon stock, a decrease in soil mineral nitrogen content, a different carabid species composition and a higher spider activity density were found, compared to the adjacent arable parcel. These results indicate a contribution of grass strips to climate regulation, the regulation of water quality, an increase of beta diversity and potential for pest control. Next to hedgerows, crop yield was reduced and winter wheat thousand kernel weight, soil organic carbon stock and spider activity density were increased. These indicators show an effect of the hedgerow on food production, climate regulation and potential for pest control. The study concludes that both grass strips and hedgerows have the potential to increase multiple ecosystem service delivery, but that an increase of every service is not assured and that multifunctionality is affected by management choices. Also, an improved experimental setup in order to enhance ecosystem service monitoring is suggested.

Improving the product stability and fertilizer value of cattle slurry solid fraction through co-composting or co-ensiling

Separating dairy cattle slurry in a liquid and solid fraction (SF) is gaining more interest, since it enables a more targeted use of both fractions. However, the valorization of the SF is limited on P-rich soils, due to its high P content, and the export or use as bedding material requires sanitation. Therefore, we investigated the influence of composting or ensiling the SF, whether or not mixed with bulking agents, on the product quality in terms of fertilizer value, sanitation and stability. Ensiling can be considered as a controlled storage method for conserving C and nutrients. Soil amendment with co-ensiled SF resulted in a higher N mineralization and crop growth compared to amendment of co-composted SF. Co-composting SF with structure-rich feedstock materials optimized the composting process and sanitation when compared with composting pure SF and did not increase the risk for extreme-heat-resistant spores of thermophilic aerobic spore-forming bacteria (X-TAS). Further, the composts contained more P per unit of fresh weight than the silages, beneficial for the export of the composted SF. The oxygen uptake rate was found to be less powerful to determine the stability of fresh, composted and ensiled SF.