Iwate Prefecture boasts the third largest apple harvest in Japan. JA Iwate Hanamaki, which grows various varieties of apples such as "Beni Iwate," "Jonagold," and "Sun Fuji," has introduced an agricultural version of "Weathernews for business," an extended business version of a weather application, in order to protect apple growth from frost damage. We interviewed Masaaki Kume -san and Koya Oishi -san of the Horticulture Sales Section, Agriculture Department, JA Iwate Hanamaki, about specific measures against frost damage.
Production down 40% to record low due to massive frost damage, frost damage in the growing stage due to recent temperature increase.
JA Iwate Hanamaki's apples are grown using a cultivation system that allows sunlight to permeate the entire tree through "dwarfing cultivation," in which the height of the apple tree is set at 2.5 meters or less, and "bagless cultivation," in which all varieties of apples are grown without bags. The temperature difference between day and night is also utilized to produce delicious apples.
The impetus for JA Iwate-Hanamaki to introduce the agricultural version of "Weathernews for Business" came from the large-scale frost damage it suffered in 2023. Frost damage is a phenomenon in which water freezes inside plants, damaging and necrotic cellular tissue and inhibiting growth.
There are some differences among varieties, but apple cultivation involves some kind of work at all times of the year. Last year, the most important time of the year, April, when apple leaves grow, flowers bloom, and pollination takes place, was hit by an influx of cold air, which, combined with radiative cooling, resulted in large-scale frost damage. As a result, the harvest volume dropped from about 280,000 cases (10 kg per case) the year before last to about 170,000 cases last year, a decrease of about 20%. Combined with the effects of the extreme heat, we lost about 40% of our apples as a whole compared to the year before last," said Oishi-san.
In the past, frost damage was most common during the leaf-opening period of apple trees, but recently frost damage seems to be occurring from the leaf-opening period to the flowering period.
The growth stage of apples at the time of frost damage seems to have shifted due to climate change, which has accelerated apple growth and brought forward the blooming period. If the damage is done before the leaf-opening period, the damage is not that great, but if the frost occurs after the leaf-opening period, the damage is much greater," said Kume-san.
This led to the use of the app as a countermeasure to stave off frost damage in apple cultivation.
Precise 1 km mesh prediction of frost damage risk 36 hours in advance, JA staff and members share dangerous garden areas and timing via app
Of the various weather factors, the one that has the greatest impact on frost damage is 'temperature. We believe that the borderline for frost damage is when the plant body temperature falls below 0°C. Therefore, it is necessary to apply frost protection measures when the temperature falls below 1 to 2°C. Therefore, when the temperature drops below 1 to 2 degrees Celsius, it becomes necessary to apply frost damage countermeasures. The weather bureau will issue frost advisories, but they are for all of Iwate Prefecture. There are many areas where fields are located in mountainous areas where it is difficult to make weather forecasts, and it has been an issue for some time that each of us has to guess and act based on temperatures and past experience to determine how much our fields will be affected," said Oishi-san.
In addition to temperatures, Weathernews for business forecasts the risk of frost occurrence at two levels, "Caution" and "Warning," for each hour up to 36 hours ahead. The risk of frost is calculated based on past weather conditions such as atmospheric temperature, wind speed, relative humidity, and atmospheric transmissivity, and is based on a 1 km mesh (square) of areas where frost is likely to occur.
Frost is a question of 'when?' and the extent of the damage. and the magnitude of the damage, are important to accurately estimate and take countermeasures. Accurate forecasting is indispensable for this," says Kume-san.
Currently, JA Iwate Hanamaki has given accounts to 27 people. For members who are not good at operating smartphones, data is compiled and shared, and staff members instruct them on how to use the system.
Highly Accurate Frost Prediction Averts Frost Damage, Reducing Actual Damage to Zero in 2024
The situation of frost damage control has not changed in the last 40 years, and although there are approaches such as "using blowers," "watering," and "covering," "bonfires" are the most useful way to raise the temperature around apple trees when cost and efficiency are considered.
The basic idea is to make one set of "bonfires" in about three hours to prevent freeze and frost damage. The first set of fires is built from 10 p.m. to midnight on the day when the need for countermeasures is predicted, and if necessary, a second set of fires is built from midnight to dawn," Kume-san said.
By confirming accurate frost forecasts with "Weathernews for business," the company has drastically reduced its human and economic burden. The company has personally verified frost forecasts and actual results at 13 locations within its jurisdiction, and found that the forecast accuracy was approximately 80%, indicating that the system is highly practical.
Compared to the past when we had to watch TV to predict the night's frost and stay up at night every day to make a "bonfire," the new system allows us to make "bonfires" on a more limited and planned schedule, which has considerably lightened the burden on our members. In fact, we had two days of frost in April 2024, but it did not have a significant impact on yields." (Oishi-san)
Expect to expand to other commodities such as asparagus, which is susceptible to frost
Frost damage can also be caused by the movement of cold air formed by radiative cooling. Frost damage also depends on weather and topography, such as the southward movement of cold air masses in the Arctic and cold air stagnation (cold air lakes) seen in basins.
In the future, I think apple cultivation will become more stable if we have information that can predict the movement of cold air by analyzing topographical and meteorological data," Kume-san said.
He also said that he is considering the possibility of utilizing the weather data for crops other than apples produced in Iwate Prefecture.
We also grow asparagus in the prefecture in the early spring. If there is a possibility to use weather data in the same way as apples to avoid the risk of frost damage, it would be a great benefit to the growers," said Oishi-san.
In an era when climate change is making it increasingly difficult to approach agriculture with the same sensibilities as before, it can be said that the number of measures that can be taken in advance by utilizing weather information will continue to increase in the future!
