H.M.G. van der Werf

Use of agro-ecological indicators for the evaluation of farming systems

For the development of integrated arable farming systems (IAFS), tools are needed to evaluate the achievement of agronomic and environmental objectives, in order to optimize the systems. A set of agro-ecological indicators (AEI) is proposed. These indicators estimate the impact of cultivation practices on the agrosystem and its environment. AEI are aimed, first of all, at being used as decision aid tools, to help farmers to adapt their cultivation practices to IAFS requirements, from one cropping year to the next. So far, seven indicators have been elaborated for the evaluation of farming systems: crop diversity, crop succession, pesticide, nitrogen, phosphorus, organic matter and irrigation. The calculation method for the organic matter and pesticide indicators is presented. Possibilities for use of the AEI at the farm and field level, for farmers and decision makers are given with data from a network of 17 commercial arable farms. The elaboration of a single aggregated indicator is discussed.

Comparison and evaluation of eight pesticide environmental risk indicators developed in Europe and recommendations for future use

Original article can be found at: http://www.sciencedirect.com/science/journal/01678809 Copyright Elsevier B.V. [Full text of this article is not available in the UHRA]

Constraints to dry matter production in fibre hemp (Cannabis sativa L.).

Abstract Fibre hemp (Cannabis sativa L.) may be an alternative to wood as a raw material for pulp and paper production. Research was done to assess the potential productivity of fibre hemp and to identify constraints to that productivity. Growth analyses were done on hemp crops in three consecutive years, using several cultivars and seeding rates. In 1987 the crops suffered severely from fungal diseases ; stem dry matter yields were 9.4 t ha−1. In 1988 and 1989 fungicides were applied and stem dry matter yields were respectively 11.9 t ha−1 and 13.6 t ha−1. The number of living plants m−2 ranged from 86 to 823 at emergence, depending on treatment, and from 38 to 102 at final harvest. Increased seeding rates led to earlier canopy closure and higher initial biomass production, but more plants died during the growing season and the stem yield at final harvest was not affected by seeding rate. Average radiation-use efficiency (RUE; above-ground accumulated dry matter divided by intercepted photosynthetically active radiation) for the entire growing season under favourable growing conditions was 1.9 g MJ−1, which is low compared to other C3 crops. Leaf photosynthesis rates at saturating light intensities, however, were high: 30 kg CO2ha−1 h−1. The light extinction coefficient of hemp canopies was high (0.96), and may have reduced canopy photosynthesis rate and RUE. The high lignin content of the stems, and the high fat and protein content in the seed, also reduced RUE. Furthermore, dry matter invested in the tap root and in shed dead leaves was ignored. The RUE was also underestimated because an appreciable proportion of the biomass of plants that died during the growing season could not be collected. More research is needed to optimize cultural practices in fibre hemp.

The effect of daylength on yield and quality of fibre hemp (Cannabis sativa L.).

Abstract Stem growth of the short-day plant fibre hemp (Cannabis sativa L.) decreases after flowering. In the Netherlands, the hemp cultivars currently available flower in August. In 1990 and 1991 the ambient daylength was compared with a 24-hour daylength in field experiments on two cultivars. Crop development, interception of photosynthetically active radiation, dry matter accumulation, stem yield and stem composition were recorded. The 24-hour daylength did not totally prevent flowering, but did greatly reduce the allocation of dry matter to floral parts. It enhanced the efficiency of post-flowering radiation use, and increased stem dry matter yield by 2.7 t ha-1. The continued stem growth resulted in higher yields, which in one cultivar were accompanied by a lower bark content of the stem. At final harvest, the 1 per cent NaOH solubility indicated a lower fibre content in the bark of plants from the 24-hour daylength. Breeding late-flowering hemp may be a promising strategy to improve the potential stem yield of hemp in the Netherlands, but the stem quality of such cultivars may be slightly poorer.

Using reference values to assess environmental sustainability of dairy farms

One challenge for the environmental assessment of agricultural systems is to progress from estimating whether one farming system has fewer impacts than another to estimating whether or not it can be considered environmentally sustainable. To this end, we developed reference values (RVs) of farm emissions or energy use per hectare that defined hypothetical sustainability thresholds in each of three impact categories: climate change, water-quality degradation and non-renewable energy use. We applied one RV per category to the potential impacts (estimated by life-cycle assessment) of 45 French dairy farms to identify farms below RVs in each impact category and then evaluated their management and production characteristics. Seventeen of the 45 farms lie below at least one of the three RVs. Groups of farms below RVs had a higher percentage of organic farms, larger mean usable agricultural area, longer mean pasture residence time and lower mean inputs of concentrate feed and nitrogen than those above the same RVs. In consequence, the groups below RVs also tended to have lower mean milk production per cow and per hectare. All milk production systems can move toward environmental sustainability even though, according to production mode and intensity, some potential impacts are easier to reduce than others. Most farms were unable to attain the lowest RVs, suggesting that policy-makers may need to consider less ambitious RVs for existing agricultural systems. Otherwise, the distance between normative RVs and indicator values of dairy farms suggest that production and consumption of agricultural products will need to change if sustainability goals do not.