Diversity of Crops Can Improve Field Quality.

We compared growth and mineral acquisition of 11 different crops cultivated at present in Finland. The crops were: oil hemp (Cannabis sativa L.), quinoa (Chenopodium quinoa Willd.), false flax (Camelina sativa (L.) Crantz), caraway (Carum carvi L.), dyer’s woad (Isatis tinctoria L.), nettle (Urtica dioica L.), reed canary grass (RCG) (Phalaris arundinacea L.), buckwheat (Fagopyrum esculentum Moench), linseed (Linum usitatissimum L.), timothy (Phleum pratense L.) and barley (Hordeum vulgare L.). Some of the crops are at present underutilised, but may have prospects for the future. All the annual spring-sown crops accumulated above-ground biomass faster than perennials, while all perennials had higher biomass accumulation below ground. Annuals would be more efficient in forming ground cover, competing with weeds and reducing erosion in the spring, while perennials would be more efficient in adding organic material to the soil, improving soil structure and reducing erosion and leaching in the long term and in the winter. Seeds were high in N and P, and green biomass in K and Ca (especially caraway and dyer’s woad). With biomass yield, the soil can be depleted from K and Ca, with seed yield P and N are efficiently removed. Stem yield of nettle, RCG, linseed and hemp was low in minerals, as were roots of all the crops. On general, quinoa and caraway were K and P accumulators, buckwheat accumulated P, hemp and nettle Ca, and quinoa Mg. We suggest that with right choice of crop and cultivation strategy, field nutrient balances and organic matter content could be managed. However, plant breeding has to develop new varieties of the underutilised crops studied here, especially fitted for Finnish long day growing conditions. The pot experiments presented here have been extended into a 4 year trial on the field, the results of which are in preparation.