Showing papers by "Rogier P.O. Schulte published in 2017"

Clay illuviation provides a long-term sink for C sequestration in subsoils

Abstract: Soil plays a key role in the global carbon (C) cycle. Most current assessments of SOC stocks and the guidelines given by Intergovernmental Panel on Climate Change (IPCC) focus on the top 30 cm of soil. Our research shows that, when considering only total quantities, most of the SOC stocks are found in this top layer. However, not all forms of SOC are equally valuable as long-term stable stores of carbon: the majority of SOC is available for mineralisation and can potentially be re-emitted to the atmosphere. SOC associated with micro-aggregates and silt plus clay fractions is more stable and therefore represents a long-term carbon store. Our research shows that most of this stable carbon is located at depths below 30 cm (42% of subsoil SOC is located in microaggregates and silt and clay, compared to 16% in the topsoil), specifically in soils that are subject to clay illuviation. This has implications for land management decisions in temperate grassland regions, defining the trade-offs between primary productivity and C emissions in clay-illuviated soils, as a result of drainage. Therefore, climate smart land management should consider the balance between SOC stabilisation in topsoils for productivity versus sequestration in subsoils for climate mitigation.

Tracing the seed : seed diffusion of improved potato varieties through farmers’ networks in Chencha, Ethiopia

Abstract: There are many prerequisites for potato production to meet its full potential as a food security crop for subsistence farmers in Sub-Saharan Africa. One of these is the introduction of improved varieties. Traditionally, the introduction of new varieties is by government agencies or Non-Governmental Organizations (NGOs). To understand the diffusion of seed tubers (seeds) of new potato varieties in farmer networks, we analysed social factors influencing the sharing of seed of improved potato varieties amongst farmers in Chencha, Ethiopia. We interviewed 166 farmers and analysed 146 seed transactions. We used seed flow mapping to visualize seed sharing amongst farmers. We found that the social networks of farmers are differentiated by wealth, gender and religion, and that this differentiation affects the dispersion of new varieties through the farming communities: Wealthier farmers shared seed tubers most frequently and poor farmers did not share seed at all. Seed sharing was influenced by, but not restricted to, gender and religion categories. Most sharing was with relatives (as gifts) and neighbours (in exchange for labour). There weas no equal access to seed for all households because of (i) the targeting of the better off farmers by the NGO (ii) differences in frequency of sharing and (iii) terms and motivation of the transactions. Our results show that wealthy farmers most effectively multiply and share the seed of new varieties with medium wealthy and poor farmers. This study shows that for the introduction of new technologies into a community, its dynamics of social differentiation need to be understood.

Gap assessment in current soil monitoring networks across Europe for measuring soil functions

Abstract: Soil is the most important natural resource for life on Earth after water. Given its fundamental role in sustaining the human population, both the availability and quality of soil must be managed sustainably and protected. To ensure sustainable management we need to understand the intrinsic functional capacity of different soils across Europe and how it changes over time. Soil monitoring is needed to support evidence-based policies to incentivise sustainable soil management. To this aim, we assessed which soil attributes can be used as potential indicators of five soil functions; (1) primary production, (2) water purification and regulation, (3) carbon sequestration and climate regulation, (4) soil biodiversity and habitat provisioning and (5) recycling of nutrients. We compared this list of attributes to existing national (regional) and EU-wide soil monitoring networks. The overall picture highlighted a clearly unbalanced dataset, in which predominantly chemical soil parameters were included, and soil biological and physical attributes were severely under represented. Methods applied across countries for indicators also varied. At a European scale, the LUCAS-soil survey was evaluated and again confirmed a lack of important soil biological parameters, such as C mineralisation rate, microbial biomass and earthworm community, and soil physical measures such as bulk density. In summary, no current national or European monitoring system exists which has the capacity to quantify the five soil functions and therefore evaluate multi-functional capacity of a soil and in many countries no data exists at all. This paper calls for the addition of soil biological and some physical parameters within the LUCAS-soil survey at European scale and for further development of national soil monitoring schemes.

Understanding farmers’ potato production practices and use of improved varieties in Chencha, Ethiopia

Abstract: This study was carried out to better understand non-adoption of improved varieties of potato (Solanum tuberosum) and associated technologies by smallholder farmers in Chencha, Ethiopia. Data were collected through a survey (n = 47) and in-depth interviews (n = 20). It shows how wealth status was a factor of major importance. Most wealthy and some medium-wealthy farmers adopted improved potato varieties and many of the improved production practices; they had access to seed, associated knowledge and support, and sufficient resources that were necessary to apply the improved practices. Non-adoption was common among many medium-wealthy and most poor farmers: they lacked—next to access to the technologies and knowledge—cash, land, and labor. Results indicated the need to rethink research and intervention efforts. Next to paying attention to differences in the access to technology and the related knowledge, there is a need to consider the variation in technology needs, supporting microcredit services, a...

Application of Dexter’s soil physical quality index: an Irish case study

Abstract: Historically, due to a lack of measured soil physical data, the quality of Irish soils was relatively unknown. Herein, we investigate the physical quality of the national representative profiles of Co. Waterford. To do this, the soil physical quality (SPQ) S-Index, as described by Dexter (2004a,b,c) using the S-theory (which seeks the inflection point of a soil water retention curve [SWRC]), is used. This can be determined using simple (S-Indirect) or complex (S-Direct) soil physical data streams. Both are achievable using existing data for the County Waterford profiles, but until now, the suitability of this S-Index for Irish soils has never been tested. Indirect-S provides a generic characterisation of SPQ for a particular soil horizon, using simplified and modelled information (e.g. texture and SWRC derived from pedo-transfer functions), whereas Direct-S provides more complex site-specific information (e.g. texture and SWRC measured in the laboratory), which relates to properties measured for that exact soil horizon. Results showed a significant correlation between S-Indirect (Si) and S-Direct (Sd). Therefore, the S-Index can be used in Irish soils and presents opportunities for the use of Si at the national scale. Outlier horizons contained >6% organic carbon (OC) and bulk density (Bd) values

Selective improvement of global datasets for the computation of locally relevant environmental indicators: A method based on global sensitivity analysis

Abstract: Several global datasets are available for environmental modelling, but information provided is hardly used for decision-making at a country-level. Here we propose a method, which relies on global sensitivity analysis, to improve local relevance of environmental indicators from global datasets. This method is tested on nitrogen use framework for two contrasted case studies: mixed dairy supply chains in Rwanda and the Netherlands. To achieve this, we evaluate how indicators computed from a global dataset diverge from same indicators computed from survey data. Second, we identify important input parameters that explain the variance of indicators. Subsequently, we fix non-important ones to their average values and substitute important ones with field data. Finally, we evaluate the effect of this substitution. This method improved relevance of nitrogen use indicators; therefore, it can be applied to any environmental modelling using global datasets to improve their relevance by prioritizing important parameters for additional data collection.

Sustainability assessment of agricultural production: Case study of latvian crop sector

Abstract: The concept of sustainability in agricultural production is characterised by three interrelated dimensions: environmental sustainability; economic sustainability; and social sustainability Research studies are needed to understand what the specific characteristics of each dimension are and how they interact in time and space The aim of this research is to make a sustainability assessment of agricultural production in the crop sector in Latvia In the paper, the authors have compiled existing studies that have tried to include all the three dimensions of sustainability analysis and to provide explanations of factors determining sustainable agricultural production It was concluded that some agricultural development indicators pointed to the challenges of meeting sustainable economic development objectives in agricultural production The results showed that this development of agricultural production in the crop sector took place at the expense of natural capital impairment, as the environmental sustainability index had fallen from a neutral value of 0 to a negative value of -025 during the last decade Activity data characterising the production practices of crop farms pointed to a non-sustainable farming system, where the intensity of exploitation of production resources of fossil origin had essentially increased