Mixed Cropping

Mixed cropping, also known as polyculture, inter-cropping, or co-cultivation, is a type of agriculture that involves planting two or more plants simultaneously in the same field, interdigitating the crops—like interlocking your fingers—so that they grow together. Since crops ripen during different seasons, planting more than one saves space and also provides a wealth of environmental benefits including maintaining a balance of input and outgo of soil nutrients; weed, disease, insect pest suppression; resistance to climate extremes (wet, dry, hot, cold); an increase in overall productivity, and management of scarce land resources to its maximum potential.

Mixed Cropping in Prehistory

Planting enormous fields with single crops—monocultural agriculture—is a recent invention of the industrial agricultural complex. While unequivocal archaeological evidence is difficult to come by, it's believed that most agricultural field systems in the past involved some form of mixed cropping. That's because even if botanical evidence of plant residues (such as starches or phytoliths) of multiple crops are discovered in an ancient field, it's proven difficult to know they are the result of mixed cropping or rotation cropping.

The primary reason for prehistoric multi-cropping probably had more to do with the needs of the farmer's family, rather than any recognition that mixed cropping was a good idea. It's possible that certain plants adapted to multi-cropping over time as a result of the domestication process.

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The Three Sisters: the Traditional Intercropping Agricultural Method

By K. Kris Hirst

Classic Mixed Cropping: Three Sisters

The classic example of mixed cropping is that of the American three sisters: maize, beans, and cucurbits (squash and pumpkins). The three sisters were domesticated at different times but eventually, they were combined to form an important component of Native American agriculture and cuisine. The mixed cropping of the three sisters, historically documented by the Seneca and Iroquois tribes in the U.S. northeast, probably began sometime after 1000 C.E.

The method consists of planting all three seeds in the same hole. As they grow, the maize provides a stalk for the beans to climb on, the beans are nutrient-rich to offset those taken out by the maize, and the squash grows low to the ground to combat weed growth and keep water from evaporating from the soil in the heat.

Modern Mixed Cropping

Agronomists studying mixed crops have had mixed results determining if yield differences can be achieved with mixed versus monoculture crops. (For example, the combination of wheat and chickpeas might work in one part of the world but might fail in another.) Overall, however, it appears that measurably good outcomes result when the right combination is cropped together.

Mixed cropping is best suited for small-scale farming where harvesting is done by hand. The process has been successfully employed to improve income and food production for small farmers and lessen the likelihood of total crop failure because even if one crop fails, others in the field might still produce. Mixed cropping also requires fewer nutrient inputs such as fertilizers, pruning, pest control, and irrigation than monoculture farming, and as is often more cost-effective as a result.

Benefits

The practice of mixed cropping has been proven to provides a rich, biodiverse environment, fostering habitat and species richness for animals and beneficial insect species including butterflies and bees. There is even some evidence to suggest that polycultural fields produce higher yields as compared to monocultural fields in some situations, and almost always increase biomass richness over time. Polyculture in forests, heathlands, grasslands, and marshes has been particularly important for the regrowth of biodiversity in Europe.

Sources

• Cardoso, E.J.B.N.; Nogueira, M.A.; Ferraz, S.M.G. "Biological N2 fixation and mineral N in common bean–maize intercropping or sole cropping in southeastern Brazil" in Experimental Agriculture 43(03), pp. 319-330. 2007
• Daellenbach, G.C.; Kerridge, P.C.; Wolfe, M.S.; Frossard, E.; Finckh, M.R. "Plant productivity in cassava-based mixed cropping systems in Colombian hillside farms" in Agriculture, Ecosystems & Environment 105(4), pp. 595-614. 2005
• Pech-Hoil, R.; Ferrer, M.M.; Aguilar-Espinosa, M.; Valdez-Ojeda, R.; Garza-Caligaris, L.E.; Rivera-Madrid, R. "Variation in the mating system of Bixa orellana L. (achiote) under three different agronomic systems" in Scientia Horticulturae 223(Supplement C), pp. 31-37. 2017
• Picasso V.D.; Brummer, E.C.; Liebman, M.; Dixon, P.M.; Wilsey. B.J. "Crop Species Diversity Affects Productivity and Weed Suppression in Perennial Polycultures under Two Management Strategies" in Crop Science 48(1), pp. 331-342. 2008.
• Plieninger. T.; Höchtl, F.; Spek, T. "Traditional land-use and nature conservation in European rural landscapes" in Environmental Science & Policy 9(4), pp. 317-321. 2006