It has never been a better time to look again at the wonderful value of peas and beans. As vegetable crops, and as dried seeds (pulses), they have been a staple food for many developing civilizations for many years. At last we are seeing the health benefits of increasing the amount of peas and beans in our developed diets.
“Caring for the Planet from the Ground” is the theme of this year’s World Soil Day (#worldsoilday). World Soil Day (WSD) is an annual campaign aimed at raising awareness of the critical importance of healthy soils and advocating for the sustainable management of global soil resources. In June 2013, the FAO Conference endorsed WSD and requested for it to be officially adopted at the 68th UN General Assembly. As a result, 5 December 2014 was designated as the first official WSD. So why is soil so important and why should we care about the health of it?
This week I had the pleasure of heading down to the south coast to attend the Society for Experimental Biology’s main meeting in Brighton. The flagship meeting attracts an international audience covering topics across the animal and plant sciences and also cell biology. For me, the main focus was to attend a plant biology session – From source to sink: Resource partitioning in plants – which I have spent the past 18 months organising with colleagues from the University of Sheffield and the University of Illinois.
Following the recent outbreak of E. coli food poisoning in Germany that claimed at least 37 lives as of 14 June 2011 and still counting, numerous articles have been written, but many fundamental questions still remain unanswered.
As you will remember, contaminated Spanish cucumbers were initially blamed for the outbreak of E. coli infection, which prompted the Spanish government and farmers to vehemently deny this claim (justifiably, as it turned out) and demand compensation.
As soon as “the Spanish cucumber story” was shown to be a false alarm, tomatoes, salad and vegetable sprouts (of German origin) were declared as potential culprits. It is unclear why other vegetables, such as peppers, courgettes, mushroom, to list but a few, were kept off the list of suspects, particularly because all the laboratory tests performed so far have been inconclusive.
As time goes by, it is less likely that the source(s) of this outbreak will be identified any time soon. However, even if a contaminated vegetable (or various vegetables) is identified and successfully linked with this outbreak of E. coli in humans, identifying the pathway of contamination may prove more difficult.
While looking for potential sources of vegetable contamination with pathogenic microorganisms, I searched CAB Direct database and came across a very interesting review published 20 years ago by German Professor Strauch of the Institute of Animal Medicine and Hygiene, University of Hohenheim, which explains how pathogens may contaminate food crops. He warned about the potential of pathogenic organisms to cross from manure or sewage into food crops and suggested that “the agricultural utilization of hygienically dubious sewage or sludge poses a risk for the whole national economy.”
In his 1991 review “Survival of pathogenic microorganisms and parasites in excreta, manure and sewage sludge” (Rev Sci Tech. 1991 Sep;10(3):813-46), Strauch also reported that two groups of researchers had found that pathogenic organisms can be taken up by crops that are used in human and animal nutrition.
Once pathogenic microorganisms are incorporated into crops (including vegetables), washing the outside of fresh vegetables is of little benefit, because all the pathogens from the sludge (bacteria, viruses and parasites) are inside the plant.
Growing of organic and genetically modified crops on neighbouring farms continues to be contentious, especially in Europe, but the issue of coexistence of same-species crops for different markets is not limited to GM. In a paper entitled “Can GM and organic agriculture coexist?”, Eberhard Weber points to the need for oilseed rape for cooking and industrial oil to be segregated, and similarly for crops for human food and animal feed for both maize and barley. Writing in CAB Reviews, he says that such situations work on the principle that some contamination will happen, but that “threshold values above zero for adventitious presence must be defined for coexistence rules.”
One company growing GM maize in Germany offered to buy maize from neighbouring non-GM farmers on the same conditions they would achieve without a GM neighbour. “The neighbouring farmers agreed, meaning that no coexistence problem arose,” says Weber, from Martin-Luther-University Halle-Wittenberg.
Weber notes that various organic organisations only require that the production process organic farmers use must not involve GMOs, rather than that they must ensure no GMO presence in their products. He quotes the International Federation of Organic Agriculture Movements: “Organic products are not defined as being free of unwanted pollution. Just as organic farmers cannot guarantee zero contamination from pesticides they do not use themselves, there is no way for them to guarantee that organic products will not be polluted by traces of GMOs.”
Weber looks at the various planting arrangements suggested to minimise gene flow to neighbouring fields. “Many experiments show that the GMO content is reduced with increasing distance as it should be, but no zero level can be achieved”. However, the variability of wind direction means no models can be entirely reliable.
As long as the same threshold value is valid for conventional and organic products, the GM farmer should not have to distinguish between neighbours with conventional and organic production, says Weber. ”The best way will always be agreement between farmers. As long as only farmers are involved, this can mostly be achieved.” However, he says that the involvement of other groups who try to influence political decisions on the rules make it difficult to predict the future of coexistence.
Can GM and organic agriculture coexist?”by Eberhard Weber appears in CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2008, 3, No. 072, 8 pp.
Much attention has focused on what plants will be able to grow where as the effects of climate change are felt. A key factor that plays into that analysis is what effect climate change will have on diseases and weeds.Two new papers in CAB Reviews look at those two elements and show that that the picture is a complex and sometimes surprising one.
Sukumar Chakraborty (from CSIRO Plant Industry) and co-authors note that modelling experiments suggest that the range of key pathogenic fungi may shift significantly towards the poles as a result of global warming. The impacts of raised CO2 and temperature together are more difficult to estimate, as raised CO2 may increase the vigour of some trees and crops. From certain studies it seems that C3 plants, such as cereals, may suffer from increased numbers of pathogens with increased CO2, while C4 plants (most other crops and trees) may not. Chakraborty and colleagues write that minor changes in climate can tip the balance in favour of an exotic species, and the same may be true of disease outbreaks. Import risk analysis will need to take into account changes in the risks of establishment of pests and pathogens as the climate alters.
Examining the 12 most serious weeds, Xianshong Wang (from Indiana University-Purdue University Indianapolis) and Jacqueline Mohan (from the University of Georgia) suggest the competitiveness of weeds at higher temperatures and CO2 levels may be affected greatly by water availability. Most of the weeds will be expected to be boosted by rising temperatures. Field bindweed may become a more serious weed in drier regions, while it may be outcompeted in well-watered soils. Purple nutsedge may suffer because of expected reductions in moisture and rising soil nitrogen.
Wang and Mohan point out that the move to biofuels may exacerbate some of the projected weed problems: “Altered land use and the unforeseen consequences of energy plants may have a greater impact on the seriousness and injuriousness of weeds and weed-crop interactions than the effects of other global environmental changes, including rising CO2, global warming and more frequent and severe droughts.”
Effects of global environmental changes on weeds by Xianzhong Wang, J.E .Mohan
CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2008, 3, No. 067, 20 pp.
Impacts of global change on diseases of agricultural crops and forest trees by S. Chakraborty, J .Luck, G. Hollaway, A. Freeman, R. Norton, K.A. Garrett, K. Percy, A. Hopkins, C. Davis, D.F. Karnosky
CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources, 2008, 3, No. 054, 15 pp.