AMES, Iowa – A new study by Iowa State University (ISU) agronomists shows crop diversity does not sacrifice yield.

“The overall conclusion is there’s a lot to be gained from diversifying cropping practices,” said Matt Liebman, an ISU professor of agronomy, and co-author of the study. He said, however, some marketing and agricultural policy considerations will have to change for farmers to adopt diversification practices more widely.

“Across many different countries in many different climates and soils, with many different crops, the general pattern is that with diversification, you maintain or increase crop yields while gaining environmental benefits,” he said.

Published in the academic journal, Science Advances, the study analyzed the results of 5,188 separate studies that included 41,946 comparisons between diversified and simplified agricultural practices.

The results showed that in 63 percent of the cases examined, diversification enhanced ecosystem services while also maintaining or even improving crop yields. The researchers described this as a ‘win-win’ result.

According to the researchers, Midwest agriculture is dominated by just a few crops – mainly corn and soybeans. But the study examined a wide range of farming practices aimed at introducing more diversity to cropland.

Giovanni Tamburini at the Swedish University of Agricultural Sciences and University of Bari, said those diversification practices include crop rotations, planting prairie strips within and along fields, establishing wildlife habitat near fields, reducing tillage and enriching soil with organic matter.

He said such measures improve water quality, pollination, pest regulation by natural enemies, nutrient turnover and reduced negative climate impacts by sequestering carbon in the soil.

“My colleagues and I wanted to test if diversification is beneficial for both agricultural production and ecosystem services,” said Tamburini, who’s also lead author. “The current trend is that we simplify major cropping systems worldwide. We grow monocultures on enlarged fields in homogenized landscapes. 

“The results of our study indicate that diversification can reverse the negative impacts that we observe in simplified forms of cropping on the environment and on production itself,” he added.

Liebman said barriers related to government agricultural policy, market considerations and the dissemination of data discourage farmers from adopting many of the diversification practices examined in the study.

But he said showing that such practices do not sacrifice yields, and in some cases, increase them, might encourage farmers to consider the practices. He added many current policies and market conditions incentivize farmers to focus on a few highly productive and profitable crops.

He said the study, which is the meta-analysis approach, allowed the research team to combine data from thousands of other studies that tested how crop diversification affects yields.

He said the researchers used innovative data analytics to find patterns in those results, which allowed them to gain a new level of insight that isn’t possible with individual experiments.

“What our study suggests is that if we want improved water quality and enhanced wildlife habitat, and if we want to continue to work on the soil erosion problem, diversification offers a lot of options to us,” he said.

For example, the trend of fewer crops in the rotation has also been observed in North Dakota, said Hans Kandel, North Dakota State University extension broadleaf crops agronomist.

“However, a number of growers, extension staff and researchers have started to diversify the cropping systems,” he said. “The results are encouraging and support the findings of the research reported in Science Advances.

“There is a lot of interest in incorporating cover crops into the farming systems,” he added. “There is a great opportunity to seed cover crops after small grains (i.e., spring wheat, barley, oats) as those crops are harvested by the end of July and the beginning of August.”

As producers in the northern part of North Dakota also grow canola and field peas, he said cover crops can be equally well-seeded after harvest of those crops since canola and field peas are also early-season crops.

“Compared to southern states, North Dakota has more options to incorporate a variety of crops into the cropping system, but economics have shifted rotations to include more soybeans; and, in general, the diversity of crops grown has decreased,” he said. “The research findings do support what I have seen. More crops and innovative cropping systems can increase the environmental benefits without reducing the crop yields of the major crops.”