The Rainmaker

A Rain Simulator that Improves Crop Protection Products

Three women holding umbrellas.

Unpredictable weather often makes pest control difficult during rain seasons across the globe. Even with good planning, unexpected showers may occur after a pesticide application.


Be it north-German drizzle or tropical downpours, Dr. Daniela Portz and her team have answers. Their job is to test the rainfastness (the ability of the product to remain effective after rainfall or irrigation) of crop protection products.


“No,” says Dr. Daniela Portz: “Singin’ in the Rain is not my favorite song.” The experienced biologist prefers “Sunshine Reggae” as she prefers sunshine to thick rainclouds in her free time, too. Nevertheless, rain is certainly an important factor in her work, specifically, the rain produced artificially at the Bayer Crop Science division’s research center. As soon as she or a co-worker touches the start display, a wide range of plant species is sprayed with carefully metered water at Bayer greenhouse located in Monheim, Germany.

Yet for Portz and her team, it’s about much more than just “rainmaking”. As part of their focus,they provide support for the formulation experts. These specialists look for the ideal composition of active ingredient and co-formulants to ensure a crop protection product exhibits optimum efficacy and can be used easily and safely.


The substance needs to spread optimally on the plant and not be washed away by rain. This calls for special experiments using a rain simulator, which generates artificial rain that bears a striking resemblance to the real thing. In the “rain tower”, raindrops aren’t just reproduced synthetically – they are also applied to plants at a near-natural impact speed. “We can set various rain intensities, from 10 mm to 80 mm per hour,” Portz explains. “After all, soybean plants in Brazil are exposed to different rainfall events than wheat in the Baltic states, for instance.”


Before irrigation, the researchers treat the plants in the spraying facility with various active ingredient formulations. After a certain drying time, irrigation starts at various intervals. This is followed around two weeks later by the biological or analytical evaluations that show which formulation is the most suitable.


The rainfastness provides farmers with important information they can deploy to optimize planning for using crop protection products, depending on the weather situation. It is also a key quality feature and sales argument for crop protection products. “That’s why our customers include the Crop Science sales teams throughout the world,” says Portz with pride. The inquiries are wide-ranging: How does Bayer product compare to the competition? Can an active ingredient formulation be adapted to country-specific conditions? “That’s not a problem for our team,” says Portz,

Her team’s work is important for the business, but the environmental and social aspects of sustainability play a key role for this scientist. “Our experiments deliver findings that help ensure we can optimize our products to reduce the amount of active ingredient required to protect the plants and consequently safeguard the harvest. If a good formulation prevents active ingredients from being washed away by the rain, only a certain amount needs to be applied, which means you can reduce the amount of active ingredient used on the field. In addition to this, the active ingredient stays where is it needed – on the plant, where it protects against pest infestation and is broken down by the plant’s metabolism,” explains Portz.


Farmers around the world make multiple decisions each season on how best to protect their crops. Bayer works to support farmers by providing a variety of tools to control weeds, protect harvests and further promote sustainability and biodiversity on their farms.


But what about the amateur gardeners? “Follow the quantities stated. It isn’t a case of ‘the more, the better’.” Portz advises. It’s imperative to always read the label and product information and pay attention to the warnings and symbols in the instructions. “And it goes without saying that no products should be used shortly before or even during a period of rainfall,” she concludes.

Facts and figures about rain


Raindrops are usually depicted as tears, but this is not correct. In the atmosphere, they assume a spherical shape. The water molecules combine with each other and are held together by the surface tension. Once raindrops start to fall, their shape changes continuously. They collide with each other, and the air resistance has a flattening effect, giving them a kidney bean shape.


Falling rain

How quickly a raindrop reaches the ground depends on the height it falls from and how large it is. If a cloud is at approximately 2,500 meters, and assuming an average speed of 22.5 km/h, a raindrop would need a little over two minutes to reach the ground. It takes up to seven minutes for smaller raindrops to cover the same distance.


The smell of rain

When it rains, we often sense a familiar smell. This is referred to as “petrichor”. When raindrops fall on dry, dusty soil, they trap tiny air bubbles that then shoot upward, as in a glass of champagne. The bubbles are released again from the raindrops, and the wind spreads the scent.


Rain volumes

On July 3, 1975 in Shangdi in the “Inner Mongolia” region of China, 401 liters of rain fell per square meter in one hour, while November 26, 1970 saw 38 liters per square meter in one minute on Basse-Terre, an island in Guadeloupe.



On average, around one billion metric tons of rainwater fall every minute worldwide.


Lack of rain

Quillagua, an oasis on the Río Loa in the Atacama Desert in northern Chile, is considered the driest place on Earth. Its average annual rainfall is just half a millimeter.

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