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Item does not contain fulltext, Radboud Reflects - actualiteitencollege, 24 april 2024, Invited lecture

Public affairs round table, 09 februari 2023, Radboud Reflects, Item does not contain fulltext

Leghennenhouder Bertus Verbeek heeft met behulp van technologie de fijnstofemissie per dier met 30% gereduceerd. WUR-onderzoek Ingrid de Jong gaat met hem in gesprek. Welke technologieën gebruikt hij nog meer en wat levert dat op? Ook bespreken ze hoe technologie gebruikt zou kunnen worden om het welzijn van dieren te meten.

Dijken opgebouwd uit een kern van zand met daarop een klei- en grasbekleding als bescherming van het talud (aan de landzijde) zijn een veelgebruikte waterkering in Nederland. De ontwerpparameters van deze dijken, zoals de kruinhoogte, worden bepaald door middel van probabilistische ontwerpmethoden. Hiermee wordt de kans op een faalmechanisme, zoals overloop, tot een normwaarde gereduceerd. Er is echter weinig bekend over de processen die leiden tot het falen van deze dijkopbouw, wanneer de ontwerpbelasting optreedt. De grootste overstromingen in Nederland zijn veroorzaakt door dijkdoorbraken. Dit onderzoek beschrijft bresvorming als gevolg van overloop en bepaalt welke ontwerpparameters de weerstand van een dijk tegen bresvorming beïnvloeden. Het model (BRAM, "a Breach Resistance AnalysisModel") combineert bestaande methoden om de duur van het faalproces van de gras- en kleibekleding te bepalen met een nieuw model op basis van kliferosie. Het model berekent de totale duur van de bresvorming aan de hand van de tijd-tot-falen per onderdeel van de dijk., Dikes constructed of a sand core, clay cover and natural vegetation as (landside) slope protection are common flood defence structures in the Netherlands. The design parameters, such as the crest height of dikes, are determined through risk assessment to reduce the remaining probability of a failure mechanism, such as overflow. Little is known about the exact process leading to failure of the typical Dutch dikes in case the failure conditions actually occur. The most notable floods in the Netherlands have all been caused by dike breaching, where local damage in the dike lead to breach formation. This research describes the process of breach formation due to overflow and determines what design parameters affect the resistance of a dike against breaching. The proposed model (BRAM, a Breach Resistance AnalysisModel) combines existingmethods to determine the time-to-failure of the grass and clay cover with a newly developed process-oriented headcut erosion model. The model assesses the total time-to-failure of a dike through sequential failure of its components.

The variation in field pea grain yield and competitiveness with annual ryegrass due to crop density, row spacing and cultivar was determined to enable farmers to better manage weeds with cultural control tactics. Crop density varied with seeding rate, cultivar, row spacing and year. Higher seeding rates were required to reach equivalent plant densities in cv. Dinkum (short, semi-leafless) compared with cv. Dundale (tall, conventional-leaf), and at 36 cm compared with 18 cm row spacing. Field pea grain yield was reduced more at low crop densities, in Dinkum, at 36 cm row spacing, and in the presence of weeds. Percentage yield losses from weed competition were similar in both cultivars (about 70–80%) at a low density of 10 plants/m2 in 2 seasons. At higher crop densities Dinkum had a larger loss than Dundale (i.e. at 30 plants/m2 losses were 60 and 35%, respectively, compared with 50 and 5% at 60 plants/m2). Seasonal variation influenced the effect of crop density on yield loss from weeds. The percentage yield loss from weeds in 1993 ranged from about 90 to 40% at plant densities of 10 to 40 plants/m2, in contrast to 1995 when 40% yield loss occurred at all these densities. Ryegrass dry weight was reduced with increasing field pea density in both years, and in the tall more than the short cultivar in 1 year. Maintaining recommended field pea seeding rates has considerable financial benefits in both weed-free (around $100/ha) and weed-affected crops (to $400/ha). In weedy situations, integrating cultural practices such as higher seeding rates and choice of cultivar that enhance crop competitiveness will improve weed management in south-eastern Australia.

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