Multi-Crop (Mixed Culture) Farming Practices Promote More Fruitful Farmland than Single-Crop (Monoculture) – Beyond Pesticides


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(Beyond Pesticides, July 15, 2021) A study by ETH Zurich finds multi-crop (mixed culture) farmlands, which include a diverse array of crops, produce higher biomass and seed yields than single-crop (monocultures). Monocultures are most prevalent among arable farmland as commercial industrial farming uses this practice to increase sowing, managing, and harvesting efficiency for higher yields. However, less crop diversity leads to higher, more intensive pesticide use as pests favor the consistent food availability monocultures provide.
An increase in toxic chemical use threatens human, animal, and environmental health, as well as food security. Ecological research already finds a positive association between plant diversity and biomass productivity in grasslands and meadows. In addition, a University of California, Santa Barbara study demonstrates that crop diversity in commercial agriculture is just as essential to supporting a stable biological system as plant diversity on non-commercial landscapes (i.e., grasslands/meadows). Therefore, this research highlights the need to develop policies that help farmers and global leaders make more knowledgeable decisions regarding crop diversity to sustain yield without toxic pesticides. The researchers note, “While crop diversification provides a sustainable measure of agricultural intensification, the use of currently available cultivars [(plant varieties for selective breeding)] may compromise larger gains in seed yield. We, therefore, advocate regional breeding [programs] for crop varieties to be used in mixtures that should exploit complementarity [(harmonization)] among crop species.”
It is critical for plants to allocate resources for reproduction or seed-bearing. This allocation of resources for reproduction is a trait known as the harvest index in the agricultural context, which determines how plant biomass converts to seed yield. Hence, this study aimed to assess seed yield and biomass differences between monoculture and mixed culture farming. To do this, researchers replicated a general garden experiment in Switzerland and Spain at two soil fertility levels (unfertilized and fertilized) and four plant diversity levels. Researchers tested eight annual grain crop species: wheat, oat, quinoa, lentil, blue lupin, camelina, linseed, and coriander. The seeds of each crop were planted in alternating, parallel rows 12 centimeters apart and grown without pesticides. Researchers compared the results of 24 different two-species and 16 different four-species mixed cultures to monocultures and a singular, isolated plant.
Overall, the results demonstrate that mixed cultures produce higher yields than monoculture farming. In mixtures of two crops, seed yields increase by 3.4 percent in Spain and 21.4 percent in Switzerland. In four-species combinations, seed yield increases 12.7 percent and 44.3 percent in Spain and Switzerland, respectively. Although seed yield was lower than expected relative to vegetative biomass in Spain, seed production remains higher among mixed cultures.
Since the 1940s, the ecological theory maintains that greater diversity promotes the stability of an ecosystem. However, U.S. commercial agriculture has become more chemical-intensive in its management and less diverse. Commercial, chemical-intensive agriculture has implications on a much grander scale, as farmers more frequently apply pesticide treatments to larger, monoculture crop areas. A growing body of scientific research supports the finding that larger, monoculture croplands contain higher pest concentrations. These regions can foster specific pests that persist as they have ample quantity of the same food source, thus resulting in greater insecticide use. Perversely, monoculture crops induce biodiversity and pollinator loss as exposure causes harm to pollinators and other animals. Pesticides can drift from treated areas and contaminate non-commercial landscapes, limiting pollinator foraging habitat.
Regions like the Midwest, which boasts vast monoculture grain crops, experience high levels of pesticide contamination in nearby water sources. This circumstance is especially concerning as Midwestern waterways previously lacked requirements for the multinational company Syngenta to monitor for atrazine contamination, a ubiquitous pesticide that the company manufactures. Although farmers aim to combat pesticide overuse and drift by using genetically engineered (GE) crops incorporated with pesticides, pests still develop resistance. In turn, farmers continue to use pesticides to combat resistance, but at a much higher rate, prompting a positive feedback loop.
This researcher presents one of the premier studies to demonstrate how crop diversity impacts seed yield on farmland. Researchers attribute additional seed yield from mixed culture farming to the biodiversity effect. This effects states, “A greater variety of plants results in a better use of available resources and more effective, natural pest control.” Small, diverse crop areas can alleviate pest pressure, as food sources differ, barring specific pest persistence.
Although the study finds mixed cultures have a lower harvest index in the agricultural context than expected, the total seed yield remained above monoculture seed production. Researchers attribute the reduction in seed yield among mixed cultures to seeds used in the experiment. Like most commercially grown seeds, those in the experiment are cultivars specifically bred for monocultures, thus perform better in monocultures.
Monocultures are a fairly recent invention of industrial agriculture to mass produce resources for food security. However, this farming practice is a breeding ground for pest infestations, resistance, and thus chemical use to combat these issues. In 2019, Beyond Pesticides set out many of the downsides of monocropping — despite its perceived advantages in terms of ease and economy for growers. Therefore, the convenience of monoculture does not guarantee necessary food security, nor safeguard human, animal, or environmental health. Government officials need to reassess the necessity of monoculture farming and implement mixed culture farming practices to circumvent pest resistance subsequent pesticide use, and vice versa.
The proliferation of large-scale, mono-crop farming has directly increased pesticide use, and existing regulation enforcement are inadequate. Transitioning from chemical-intensive commercial monocultures to diverse, organic mixed cultures can reduce pest presence and pesticide use. Organic agriculture has many health and environmental benefits, which curtail the need for toxic pesticides. Regenerative organic agriculture revitalizes soil health through organic carbon sequestration, while reducing pests and generating higher profits than chemical-intensive agriculture. Learn more about the adverse health and environmental effects chemical-intensive farming poses for various crops and how eating organic produce reduces pesticide exposure. For additional information, see Beyond Pesticides webpage on organic agriculture.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Science Daily, ETH Zurich/Nature Plants

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