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Crop rotation: a promising way to improve food security under a changing climate
Published: 25 November 2020
Cropping systems are increasingly simplified, with fewer and fewer crop species grown in rotation from year to year. But diverse rotations provide higher crop yields compared with continuous monoculture, in particular in years with low precipitation and high temperatures. A team of Swedish, Polish and Italian researchers found this by analysing cereal yield data collected for decades from long-term agricultural field experiments from southern to northern Europe. Diversifying our crop rotations emerges as an adaptation to a forthcoming warmer and drier climate.
Global demand for food is predicted to increase by 50-70% in the coming forty years, according to FAO. Although yields continue to increase in many regions, they either never improved, stagnated or even collapsed across about one third of the growing area of major staple crops. Soil exhaustion, pest build-up and climate change play key roles for this worrying trend. We have lost 5.5% of global wheat production due to climate change alone between 1980 and 2008. We need to adapt our crop production systems to better cope especially with rising temperatures and more frequent and prolonged droughts, such as in 2018 in northern and central Europe.
Crop diversification has been suggested as a general strategy to sustain yields and reduce risks of yield losses from adverse climatic conditions, through improved soil fertility, enhanced beneficial soil biota and suppressed build-up of weeds, pests and diseases.
“But the trend in major cropping systems worldwide is that we grow cereals in shorter and shorter rotations, and in some places even in continuous monoculture”, says Professor Lorenzo Marini at Padova University in Italy and lead author of the study. “And it was unclear how this affects cereal yields in a changing climate”.
The team of Swedish, Polish and Italian researchers tested whether diversified crop rotations works as climate change adaptation strategy. They merged unique yield information in their countries from seven long-term agricultural experiments, thus spanning northern to southern Europe. The experiments were established as far back as in 1958. In each experiment, cereals grown in monoculture had every year since been compared with the yields from diverse crop rotations. By matching these yield time series with meteorological data from each location, the team could explore yield outcomes in, for instance, dry and hot, or wet and cold years.
“Collecting decades of yield data under similar management allows us to assess effects of variability in climatic conditions, something that is virtually impossible in short-term experiments”, says Associate Professor Giulia Vico at the Swedish University of Agricultural Sciences and co-author of the study. “Our study demonstrates the importance of maintaining long-term experiments”.
Growing multiple crop species in a year-to-year rotation always gave higher yields compared with a continuous monoculture. The average yield gain with rotation was 860 and 390 kg/ha in autumn- and spring-sown cereals, respectively. In spring cereals the benefit of a diverse rotation increased without plateauing over time since the beginning of the experiments, reaching a gain of 500 kg/ha after 50-60 years. The benefit of a diverse rotation was stronger in hot and dry years, a condition that is predicted to become more frequent with climate change. In extremely dry (less than 143 mm total rain) and warm growing seasons (more than 17 °C in daily average temperature), the average yield gain was 800 kg/ha for spring sown cereals in fields with crop rotation. For autumn sown cereals the average yield gain was 1100 kg/ha during dry years, while heat lowered the harvest to the same extent for both monocultures and crop rotation.
In short: Diversified rotations emerge as a promising way to improve food security under a changing climate.
“The long-term experiments demonstrate just how ineffective poor rotations are, which may increase the need for fertilizers and pesticides to maintain yields and be even less adequate under future climates”, says Professor Zuzanna Sawinska at the Poznań University of Life Sciences in Poland.
“Given that our results clearly show that diversified rotations is a promising way to maintain crop production and food security in a changing climate, we now need redirected incentives that give opportunity for farmers to grow diverse crop rotations to secure also future food supply”, says Professor Riccardo Bommarco at the Swedish University of Agricultural Sciences and co-author of the study.
This study compares monocultures with crop rotations, but without considering the length and diversity of the latter. Probably extending shorter rotations, adding crop after crop to the rotation, has also a positive effect, but this is still unclear and the focus of current research at the Swedish University of Agricultural Sciences.
More about Long-Term Agricultural Experiments
Crop yield and soil health depend on which cropping practice we use in agriculture. It can be crop species grown, tillage, fertilization and crop protection practices. However, outcomes of management practice on crop yield often become evident only after many years of use.
Long-term agricultural plot experiments that run for decades were designed to examine such long-term effects and identify best practices that maintain or strengthen the productivity of a crop field over generations.
Yields depend on the weather in each growing season. Many years of crop yield and meteorological data from consistently managed field plots allow for analyses of how variation in climatic conditions affect crop yields and how this depends on management practices. Such high quality information is crucial to accurately predict weather impacts on yield and decide how we should grow our crops for the best results.
Long-term agricultural experiments are now also a unique resource to investigate the efficacy of cropping practices for the adaptation of agriculture to climate change.
Contact persons
Professor Lorenzo Marini
University of Padova, Department of Agronomy, Food, Natural resources, Animals and Environment
+39 049 8272807, lorenzo.marini@unipd.it
Professor Riccardo Bommarco
Swedish University of Agricultural Sciences, Department of Ecology
+46 18 672423, Riccardo.Bommarco@slu.se
Associate professor Giulia Vico
Swedish University of Agricultural Sciences, Department of Crop Production Ecology
+46 18 671418, giulia.vico@slu.se
Professor Antonio Berti
University of Padova, Department of Agronomy, Food, Natural resources, Animals and Environment
+39 0498272828, antonio.berti@unipd.it
Associate professor Guido Baldoni
Alma Mater Studiorum University of Bologna, Department of Agro Food Science and Technology
+39 051 2096664, guido.baldoni@unibo.it
Professor Zuzanna Sawinska
Poznan University of Life Sciences, Department of Agronomy, Faculty of Agronomy, Horticulture and Bioengineering
+48 061 8487406, zuzanna.sawinska@up.poznan.pl
Professor Andrzej Blecharczyk
Poznan University of Life Sciences, Department of Agronomy, Faculty of Agronomy, Horticulture and Bioengineering
+48 061 8487418, andrzej.blecharczyk@up.poznan.pl
Scientific Associate Audrey St-Martin
Technology and Support Center, Department System Evaluation of Renewable Resources,
+49 09421 300-146, audrey.st-martin@tfz.bayern.de
Scientific article
Lorenzo Marini et al. 2020. Crop rotations sustain cereal yields under a changing climate. Environ. Res. Lett. https://iopscience.iop.org/article/10.1088/1748-9326/abc651
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