The many benefits of growing a mixture of crop varieties together have now been demonstrated for many crops under many conditions. Latest entry is in a kind of specialised niche — organic tomatoes for processing — and the results are a little underwhelming. Three scientists at the University of California, Davis, grew one, three or five tomato varieties in soil that was either fallow or had a mustard cover crop the preceding winter. 1 Although there were differences between the mixtures and the monocrop, they were not very pronounced: more shoots, and more fruits that were somewhat redder.
The 3-cv mixture thus had some minor advantages compared with the monoculture, but overall, there was little evidence of higher ecosystem functions from mixtures vs. monoculture.
Leaving aside the question of whether the growing conditions on the farm, as described in the paper, accord with organic ideals, given that they do abide by the rules, it is hard to know what to make of the poor showing of mixtures. The authors concede that there may simply be no benefit to be had because the conditions on California organic processing tomato farms don’t stress the crop to the point where a mixture might be a good thing. It is also possible that the varieties — AB-2, CXD-19, H-2601, H-8892 and Red Spring — do not actually encompass enough trait diversity to offer any benefits. But then, they were chosen as simply the best-performing processing varieties. If mixtures were assembled deliberately to deliver potential benefits, the results might well be different.
Still, good to know.
El-Sayed is adamant that the seeds and field genebank are safe. However, it is clear that the laboratories have been thoroughly trashed, and a lot of equipment broken or taken.
Along with the computers went a lot of data. El-Sayed says he has lost some of his PhD data. And the genebank’s database seems to be gone, although the passport data is still around in hardcopy. There are about 1100 accessions in the genebank, of about 750 wild plant species.
Which brings up a point that’s maybe not often addressed. And that is that the desirability of safety duplication goes as much for the data about germplasm accessions as for the seeds themselves.
