Nature doesn’t do monoculture
"Nature doesn’t do monoculture." In my first two weeks of working at the Soil Association these 4 words defined 3 separate conferences that I attended, and only one of them was an organic conference.
From Agroforestry, with its linking of trees and farming to the importance of diverse species in cover crops and grazing for livestock, monocultures have become a bad word. The mixing of species in the field give different benefits to the soil, the bacteria, fungi, and invertebrates that live in it. Above the soil a variety of food sources for beneficial insects, birds and animals help in the control of pests, and provide the pollination necessary for many of our crops.
Used in cover crops, deep rooting plants bring phosphates and potash back to the surface layers, and crack through compaction. Shallower rooting plants take up unused nitrogen which can’t then pollute rivers, and straw and stems can breakdown to increase soil organic matter with all the benefits that come from that.
In an arable field, mixing beans and wheat in the field can produce up to 25% more total yield per hectare than growing the same crops separately. Intercropping can also provide a subsidiary crop that improves weed control and maybe even a second cash-crop in the year. This is also known as relay cropping and is common in gardens, with lettuce under sweetcorn a good example.
Mixed varieties of cereals in a field can provide increased disease resilience, and the different growth patterns has been seen to disrupt pests who seem to like a nice consistent playing field. Peola is the name given to a mix of peas and OSR, the peas using the rape stems for support, easing harvest. A mix of peas or lupins with spring barley can be cut for whole crop silage, or combined as a pre-mixed animal feed if the silage pits are already full.
However, It is not that simple because there are possible difficulties. The mixture of crops and varieties need to have matching harvest dates. Mixed species will need an extra process to separate them for sale unless they can be used together. Merchants need named varieties for milling and malting, and for many human consumption markets. Not all species can grow together, maize for example doesn’t like competition early in its growth and can compete for light and water when fully grown.
But we can get around this using the resilience of some crops. Westerwold or Italian ryegrasses can be sown into growing maize crops in June. The seeds will germinate and grow slowly, but will grow away rapidly after the maize is harvested, giving an "early bite" for cattle or sheep, and stabilizing the soil against water erosion over winter. The use of livestock on arable farms is another form of species diversification, the benefits of grazing, manure and treading in of residues adding to soil organic matter, invertebrate numbers, fungi and bacteria levels.
These are all simple ways that we currently use crop mixtures in farming and so it is not a new idea but it may be one that we need to look at again.