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A knowledge approach to sustainable agriculture

Analyses of the effects of potato cyst nematodes (Globodera pallida) on growth, physiology and yield of potato cultivars in field plots at three levels of soil compaction

Field experiments were carried out in 1991 and 1992 on sandy soil highly infested with the potato cyst nematode Globodera pallida. Half the trial area was fumigated with nematicide to establish two levels of nematode density. Three levels of soil compaction were made by different combinations of artificial compaction and rotary cultivation. Two potato cultivars were used in 1991 and four in 1992. Both high nematode density and soil compaction caused severe yield losses, of all cultivars except cv. Elles which was tolerant of nematode attack. The effects of the two stress factors were generally additive. Analysis of the yield loss showed that nematodes mainly reduced cumulative interception of light while compaction mainly reduced the efficiency with which intercepted light was used to produce biomass. This indicates that nematodes and compaction affect growth via different damage mechanisms. Nematodes reduced light interception by accelerating leaf senescence, by decreasing the specific leaf area and indirectly by reducing overall crop growth rate. Partitioning of biomass between leaves, stems and tubers was not affected by nematode infestation but compaction decreased partitioning to leaves early in the growing season while increasing it during later growth stages. The effects of nematodes and compaction on root length dynamics and nutrient uptake were also additive. This suggests that the commonly observed variation in yield loss caused by nematodes on different soil types is not related to differences in root system expansion between soils of various strength. Cv. Elles, which showed tolerance of nematodes by relatively low yield losses in both experiments, was characterised by high root length density and thick roots. These characteristics did not confer tolerance of soil compaction, since compaction affected root lengths and tuber yields equally in all cultivars. In the first experiment only, high nematode density led to decreased root lengths and lower plant nutrient concentrations. The yield loss which occurred in the second experiment was attributed to the effects of nematodes on other aspects of plant physiology. Copyright © 1995, Wiley Blackwell. All rights reserved

Regulation of sulfur metabolism in seedlings of the C4 plant maize upon sulfate deprivation and atmospheric H2S exposure

The increased cultivation of highly productive C4 crop plants may contribute to a second green revolution in agriculture. However, the regulation of mineral nutrition is rather poorly understood in C4 plants. To understand the impact of C4 photosynthesis on the regulation of sulfate uptake by the root and sulfate assimilation into cysteine at the whole plant level, seedlings of the monocot C4 plant maize (Zea mays) were exposed to a non-toxic level of 1.0 µl l−1 atmospheric H2S at sulfate-sufficient and sulfate-deprived conditions. Sulfate deprivation not only affected growth and the levels of sulfur- and nitrogen-containing compounds, but it also enhanced the expression and activity of the sulfate transporters in the root and the expression and activity of APS reductase (APR) in the root and shoot. H2S exposure alleviated the establishment of sulfur deprivation symptoms and seedlings switched, at least partly, from sulfate to H2S as sulfur source. Moreover, H2S exposure resulted in a downregulation of the expression and activity of APR in both shoot and root, though it hardly affected that of the sulfate transporters in the root. These results indicate that maize seedlings respond similarly to sulfate deprivation and atmospheric H2S exposure as C3 monocots, implying that C4 photosynthesis in maize is not associated with a distinct whole plant regulation of sulfate uptake and assimilation into cysteine.

Bat boxes as a tool for biological insect pest control on cocoa plantations in Ghana

Ghanaian farmers suffer from a decline in cocoa production partly due to damages and diseases from insect pests. To increase predation by bats on insects on the cocoa plantations we installed two different types of bat boxes on 15 plantations around the village of Buoyem. Bat activity, bat species composition (numbers of insectivorous and frugivorous bats) and insect abundance were measured before and after bat box installation. Insectivorous bats were present on all ofthe sampled plantations, namelyleaf-nosed bats (Hipposideros sp.), slit-faced bats (Nycteridae sp.), horseshoe bats (Rhinolophus sp.) and vesper bats (Vespertilionidae sp.). Furthermore, no correlation between insect abundance and bat activity could be detected. The bat boxes were not occupied yet during the research period since rainy season started in the second half of the measurements and bat activity decreases with increasing precipitation which is supported by our Un dings. Additionally, the available time period between in stallation and measuring of the effects of the boxes was very short when compared to similar researches. Bats alsohave different preferences per species for size and shape of bat boxes and the number of naturally available roosting sites also influences bat box occupancy. Our results suggest that bats are abundant above cocoa plantations in Buoyem and therefore bat boxes have the potential to be ahelpful tool in insect pest control.

Biomimicry

There is more to be learned from nature as a whole. In practice ‘nature’ is often used in teaching, training, consultancy and organisational development as a metaphor, as a source of inspiration or as an example for all kinds of processes, including leadership, cooperation, relationships and the development of organisations and society. Mainly ecological, and much less frequently biological, processes are generally involved here. The question has gradually arisen whether we can learn more from nature in the social environment than what we ‘see’ on the surface - which is often translated in metaphors. Seen more holistically, this is about the systemic side, the complexity, the context and the coherence. For example, can we demonstrate that applying fundamental ecological principles, such as cycles (learning, self-organising, selfregulating and self-sufficient capacity), succession, diversity and resilience, social and cooperative behaviour, interconnectedness and interdependency within an organisation leads to a sustainable organisation? Mauro Gallo is conducting research into the significance of technical innovation in and for the agricultural and food sector, and into the question whether biomimicry can in fact be backed up in such a way that it contributes to the social sciences domain. At the same time there is a clear teaching issue: Is it logical from the perspective of our green DNA to include biomimicry thinking in our teaching? Is it possible to learn to apply biomimicry, and can biomimicry be applied in teaching/learning? (How) can we apply biomimicry in green VMBO and MBO, pass it on to the teachers of the future in teacher training courses and include it in making current lecturers more professional? Is it conceivable that it could become an integral component of the curricula in green HBO?

The environmental impact of valorising agricultural by-products

Agricultural by-products, that is primary residue, industrial by-products and animal manure, are an important source of nutrients and carbon for maintaining soil quality and crop production but can also be valorised through treatment pathways such as fermentation, incineration or a combination of these called bio-refinery. Here, we provide an overview of opportunity to reduce environmental impact of valorising agricultural by-products. We estimate the available by-products in Northwestern Europe as a case study and the maximum and realistic greenhouse gas reduction potentials. Availability, collectability, the original use and environmental impact including land use changes, soil carbon sequestration and pollution swapping are discussed as critical factors when valorising agricultural by-products.