Simulations on Zimbabwe crops show better soil quality could mitigate climate change effects

This study has simulated the effects of climate change on crop production in Zimbabwe and found that changes in temperature, rainfall and carbon dioxide negatively affect yields. However, a focus on improved soil quality can mitigate the effects of climate change to protect crop yields.

Climate change is likely to negatively impact Zimbabwe’s agricultural sector, the mainstay of the country’s economy, but there is a lack of information to help smallholder farmers respond to the risks. Climate change has the potential to change rainfall patterns and the amount of carbon dioxide available, and so impacts crop production. But the exact effects of these changes have not been studied well in Zimbabwe.

This study therefore looked at the effects of expected changes in rainfall, increases in carbon dioxide (CO2), and temperature, on crop production using two mathematical models.

The researchers used the two models to determine the effect of single and combined climate change factors on the productivity of groundnut and maize crops in the Nkayi region of Zimbabwe. They used the models to simulate different seasons, the role of different processes of the soil such as water cycles and nitrogen cycles, in addition to the maximum and minimum temperatures that crops can experience throughout the day.

The researchers used the models to investigate the impact of climate change on the grains of maize and groundnut, and on the stems and leaves that are usually left on the field during harvesting (known as stover).

The study found that the two models agreed on the effects that different climatic factors have on both maize and groundnuts, however, the magnitude of the effects varied. The APSIM model showed that maize grain yields are reduced with climate change, while the DSSAT model showed that maize stover is greatly reduced by climate change.

Both models showed that groundnut production increased at higher levels of carbon dioxide (CO2), but the DSSAT model showed more favourable production of both groundnut grain and stover at higher temperatures and higher CO2 levels.

The researchers found that soils play an important role in determining how crops can adapt to changes in rainfall and temperature.

These results show that good soil quality is the key to buffering the effects of climate change on crop production. The researchers recommend that farmers and governments in Africa focus on improving their soil to protect themselves from the impacts of climate change.

Abstract

Although climate change is likely to affect a wide variety of sectors in Zimbabwe, the risk to agriculture stands out most since agriculture is the mainstay of the country’s economy. In addition, there is little information available on how to help smallholder farming systems and livelihoods respond to these risks. To determine the effects on crop production of expected changes in precipitation patterns and projected increases in carbon dioxide (CO2) and temperature, we used two process-based crop models—the Decision Support System for Agrotechnology Transfer (DSSAT) model and the Agricultural Production Systems Simulator (APSIM) model. The models were calibrated and validated to assess the effects of single and combined climatic factors on grain and stover yield performance of maize and groundnut, across three soil types. The two models generally agree on the effects that different climatic factors have on both maize and groundnuts, however, the magnitude of the effects varied. For example, reductions on maize grain yields are more pronounced in the APSIM model while the DSSAT model shows more pronounced reduction of maize stover yields. Both models show yield benefits under elevated CO2 concentration for groundnuts negating the effects of increased temperatures when evaluating the combined effects of the climatic factors. However, yield increases for both groundnut grain and stover are more pronounced in the DSSAT model. The key finding is that soils play an important role in determining outputs of crop-climate interactions: they can buffer or aggravate climatic impacts.

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