Modelling grass digestibility on the basis of morphological and physiological plant characteristics

Grass digestibility is determined by the rate of plant development, mass of plant organs (leaf blades, leaf sheaths and stem internodes) and composition of organs. The development of an integrating model for grass digestibility necessitates the quantification of developmental characteristics of plants and their organs and the effects of environmental factors and management practices. The main objective of this study was a thorough analysis of changes in composition and digestibility of plant organs of two grass species ( Lolium perenne and L. multiflorum ). These characteristics were quantified in glasshouse experiments on vegetative and reproductive plants.Detailed analyses were made of the specific cell wall ( s cw ) and cell contents ( s cc ) mass of the various organs (mg OM cm -2), which determine cell wall content (CWC), and of cell wall digestibility (CWD). During growth, s cw and s cc of all plant organs increased. After full organ expansion had been reached, s cw remained unchanged, while s cc declined, resulting in an increase of CWC. CWD of plant organs declined during ageing. The increase in the proportion of indigestible cell wall per leaf appearance interval could be described by a negative exponential curve, with a fractional rate that was the same for all plant organs, temperatures and populations. The decline in CWD of whole shoots was a linear function of shoot development stage, i.e. number of appeared leaves. Cutting had only a marginal effect on the digestibility of whole shoots.The implementation of these trends in an object-oriented simulation model resulted in acceptable estimations of growth, development and digestibility of grass under contrasting environmental conditions in the field. Sensitivity analyses with the model demonstrated that the morphological plant characteristics leaf blade length and width, and leaf appearance rate have no systematic effect on composition and digestibility. The model using object-oriented principles offers large opportunities for simulation of collections of individual plants and plant organs in complex and varying environments.The cumulative gas production technique is a potential addition to in vitro measurement of digestibility. It was demonstrated that a multiphasic equation is required for mathematical description of gas production curves. Curves from incubations with strongly contrasting types and concentrations of substrate, medium and inoculum could be fitted precisely with one flexible, multiphasic sigmoidal equation. Parameters in the equation were related to biological phenomena. These findings contribute to improved interpretation of in vitro fermentation studies and fine-tuning of the cumulative gas production technique.</p

Exploring sustainable technical alternatives for Dutch dairy systems by integrating agro-economic modelling and public preferences assessment

Theoretical discussions on the joint consideration of multiple (economic, social and environmental) functions when assessing the sustainability of human actions are increasing. However few studies exist that integrate the social demand for multifunctional agriculture in the evaluation of the sustainability and the global welfare of society. This paper presents a methodology to answer to these questions: Which are the social demands for the multiple functions of agriculture and how can they be quantified?; Which are the feasible technical alternatives of land management to satisfy these demands?; What is the value of the land use alternatives according to social preferences and which alternatives optimally satisfy the social preferences?. The net utility of alternatives for society, and therefore their sustainability, will be measured as the sum of market and non-market net changes compared to the current situation. The proposed methodology combines economic valuation, integrated modelling, stakeholder analysis, and multi-criteria evaluation. In particular, different multi-criteria methods (QFD/ANP) and agro-economic modelling and optimizing tools (Landscape IMAGES) were used. The methodology will be fully illustrated through the case study of dairy farming landscapes in the Northern Friesian Woodlands, The Netherlands. Results show that for the case study it is possible to change current farming techniques and achieve more sustainable farming systems. The more sustainable alternatives are beneficial for farmers, obtaining higher gross margin, and for government, decreasing the current levels of subsidies in agri-environmental programs. Even current environmental restrictions can be slightly relaxed without compromising social demands to the analysed Dutch dairy farming systems.Land-use planning, public preferences, agro-economic models, Environmental Economics and Policy, Livestock Production/Industries,

Bridging youth and gender studies to analyse rural young women and men's livelihood pathways in Central Uganda

Many development countries are currently undergoing major demographic shifts as the percentage of young people of the total population rapidly increases. This shift is associated with high rates of migration, unemployment and instability. In policy discourses, engaging youth in commercial agricultural is often presented as a measure to control or even counter these trends. In Uganda, a country with one of the youngest populations in the world, we investigated whether young people themselves see a career in farming as an option. We studied the livelihood pathways of rural-born young men and women from Central Uganda and in particular; 1) their aspirations, 2) the extent to which these aspirations are associated with agriculture, and 3) the importance of gender in shaping their opportunity spaces. Data consisted of in-depth interviews with 8 young men and 8 young women originating from the same rural community in Central Uganda (2017) and was supported by three additional datasets collected between 2010 and 2014; one qualitative case-study conducted in the same site (2014) and two survey datasets collected in three rural sites in Central Uganda in 2010 (N = 199) and 2012 (N = 54). Our findings suggest a large proportion of youth out-migrating from the rural communities, with young women migrating more often than young men. Farming was seldom an aspiration but irrespective of sex or residence most young men and women did remain engaged in agriculture in some way. The nature of the engagement was different for men and women though, with young women specifically refraining from commercial agriculture. By analyzing the opportunity space of young men and women, we uncovered how their livelihood pathways were linked to a set of normative and structural constraints maintaining gender inequality. Examples were young women's weaker resource base (land) and gender norms which discourage young women's independent commercial (agricultural) activities. To advance the engagement of young men and especially women in commercial agriculture, it is important to acknowledge these patterns and their underlying structural gender differences.</p

Diagnosis for ecological intensification of maize-based smallholder farming systems in the Costa Chica, Mexico

Enhanced utilization of ecological processes for food and feed production as part of the notion of ecological intensification starts from location-specific knowledge of production constraints. A diagnostic systems approach which combined social-economic and production ecological methods at farm and field level was developed and applied to diagnose extent and causes of the perceived low productivity of maize-based smallholder systems in two communities of the Costa Chica in South West Mexico. Social-economic and production ecological surveys were applied and complemented with model-based calculations. The results demonstrated that current nutrient management of crops has promoted nutrition imbalances, resulting in K- and, less surprisingly N-limited production conditions, reflected in low yields of the major crops maize and roselle and low resource use efficiencies. Production on moderate to steep slopes was estimated to result in considerable losses of soil and organic matter. Poor crop production, lack of specific animal fodder production systems and strong dependence on animal grazing within communal areas limited recycling of nutrients through manure. In combination with low prices for the roselle cash crop, farmers are caught in a vicious cycle of cash shortage and resource decline. The production ecological findings complemented farmers opinions by providing more insight in background and extent of livelihood constraints. Changing fertilizer subsidies and rethinking animal fodder production as well as use of communal lands requires targeting both formal and informal governance structures. The methodology has broader applicability in smallholder systems in view of its low demand on capital intensive resource

Exploring the potential for improved internal nutrient cycling in dairy farming systems, using an eco-mathematical model

Nutrient management at Dutch dairy farms is changing rapidly from strong reliance on external inputs to more prudent utilization of internal resources. This paper explores opportunities and constraints arising from this shift towards eco-technological management. A mathematical model of inorganic and organic nitrogen (N) flows in a dairy farming system was formulated based on ecological concepts, integrating processes of nutrient input, recycling, immobilization and mineralization. Recycling is defined as the mineralization of N within the year of its incorporation into herbage, which occurs through release from faeces, animal urine and non-harvested biomass. We simulated changes in inorganic and organic N per hectare, and the consequent emission (E), mineralization (MS) and recycling (R) of N for different initial amounts of inorganic and organic N. Results demonstrate that in the long term, the system evolves to equilibrium amounts of inorganic and organic N, which are strongly determined by the imposed management practices, such as fertilizer input and grassland management. In the short term, moving away from the equilibrium is possible for particular initial amounts of inorganic and organic N. In the equilibrium state, E was reduced by lowering inorganic fertilizer input rate, increasing grassland productivity and improving animal N conversion efficiency, i.e., only by production-related parameters. Only in the short term E was affected by adjustments in quality-related parameters: lower N content, lower digestibility of herbage, reduced degradability of non-harvested biomass and faeces, and parameters determining the functioning of soil biota (degradation rate, efficiency, C/N ratio). Qualityrelated parameters had no effect on internal nutrient cycling in the equilibrium state, because adjustments in MS were completely compensated by changes in R. A comparison of farming systems demonstrated that farming systems can be designed in such a way that improvement of internal nutrient cycling supports the same production with lower inputs and lower emissions