Winter oilseed rape : analysis of yield formation and crop type design for higher yield potential

The study described in this thesis focuses on quantifying the seed yield formation of winter oilseed rape and on identifying crop traits and combinations of traits for increasing seed yield potential in North-West Europe, by combining experimental research with crop growth simulation. The experimental research yielded quantitative detailed data on pod formation, seed set and seed filling. Results on light absorption, light use efficiency and crop growth showed that the first two of these explain much of the variation in crop dry matter production. An empirical model was developed to describe the phenological development of the crop in relation to environmental factors. Comparison of its predictions of various developmental stages with data recorded in Germany, the Netherlands and France, showed that much of the variation in duration of the various developmental phases is attributable to the combined effect of temperature (including vernalization) and photoperiod or to the effect of temperature only. Key processes of crop growth, phenological development and partitioning of assimilates to the seeds were integrated in a simple crop growth model, whose performance was evaluated with data used for parameterization and with independent data. The model recognizably reproduced the observed variation in various crop characteristics, such as total dry matter production, pod density, seed density and seed yield resulting from different sowing dates and growing seasons. Differences between sowing dates were simulated better than differences between years. The model was used to identify options for increasing seed yield potential. Comparison with the higher-yielding reference crop, winter wheat, showed that light absorption, light use efficiency and harvest index were relatively weak yielddetermining components. Crop traits and combinations of traits were identified to obtain higher values in these components. Finally, high-yielding crop types were designed and tested in simulations for various locations in North-West Europe and showed good prospects for increasing seed yield potential

Efficient resource management in dairy farming on sandy soil

Sandy soils in the Netherlands are mainly used for dairy farming. As a result of intensification of dairy farming in the recent past, valued functions of sandy regions now are threatened by high emissions of nitrogen (N) and phosphorus (P) and by increased water consumption by forage crops. Improved utilization efficiency of resources is proposed as a strategy to realise environmental targets in an economically viable way. Experimental results of the prototype system 'De Marke' indicate that an average intensive commercial farm can halve inputs of fertilizers and feeds at least, without the need to reduce milk yield/ha or to export slurry. Water consumption can be reduced by 13%, increasing groundwater 'production' by 570 msuperscript 3/ha. Nitrate concentration in the upper groundwater decreased from 200 to 50 mg/litre. Changes in soil fertility did not lead to serious agricultural problems but costs of milk production increased by 5%. However, additional costs may be compensated for if the extra groundwater is 'harvested' by water companies, because of high cost of purification of surface water and consumer preference for drinking groundwater instead of river-water. In 1999, the examined strategy of improved resource management was implemented on 12 commercial farms, representing the full range of conditions for dairy farming in the Netherlands

Competition between a sugar beet crop and populations of Chenopodium album L. and Stellaria media L.

Analyse van de inlvoed van de morfologie van de onkruiden melganzevoet en vogelmuur op het concurrentievermoge