Activities in Japan

Yanmar’s Mitsunae technology for rice-planting systems saves labor and reduces costs.

What is Mitsunae?

Normally, dry seed rice is sown to a density of 100 to 150 g per nursery tray (or 125 to 187 g for germinated seed). With high-density planting, on the other hand, seed rice can be sown to a higher density of 250 to 300 g (or 312 to 375 g for germinated seed). What’s more, Yanmar’s proprietary technology allows for precision picking of 3 to 5 seedlings in nursery trays in the same manner as the conventional method, which enables precision transplanting in the same manner as conventional rice planting.

Selected as an advanced agricultural technology for 2016

Advantages of Mitsunae

Number of nursery trays is reduced to 1/3
Nursery material cost is reduced to 1/2
Sowing/seeding carry time is reduced to 1/3
Requires management methods almost the same as conventional methods. No special skills required.
  • Estimated for management of a 30-ha rice paddy, assuming 100 g/tray (similar to conventional methods) and 300 g/tray with Mitsunae.

Traditional Japanese method of raising seedlings and planting rice

Japan led the market in developing rice-planting machines that mechanized the task of planting rice. In order to ensure the success of mechanized rice planting, it is essential to prepare uniform, high-quality seedlings that are best suited for rice-planting machines.

With the traditional Japanese rice-planting method, seed rice is sown at a density of 100 to 150 g per nursery tray, although this can vary depending on the condition of the cultivated field. For example, about 230 nursery trays are required (assuming 150 g per tray) to plant 1 hectare. As the number of nursery trays increases, farmers see associated and remarkable increases in material costs, nursery tray carrying time, and greenhouse area required. These cost factors limit farmers’ ability to expand the scale of their crop.

“Mitsunae” is the technology developed to solve these problems. This technology actually reduces the hard labor required to carry nursery trays as well as the cost of raising seedlings. Since the planting management method is very similar to the conventional method, Mitsunae can be adopted without the need to learn difficult skills. This technology has attracted much attention in Japan as a planting method that helps to improve the efficiency of agricultural management.

Background to the development of “high-density planting,” the revolutionary approach to rice planting in Japan

Questioning conventional practices.

A willingness to question the conventional can lead to the development of something that changes the world. Although this is easy to say, it is more difficult to put into practice. People who follow conventional wisdom might become confused, even if ordered to stand an egg on its end. (The phrase “Columbus’s egg” is believed to have come from Columbus’ ability to stand a raw egg on its end.) The shell of the “egg” known as “conventional practice” is quite thick. In order to break the shell by discarding preconceptions, we must make our best efforts and focus our thoughts.
Mitsunae is like the story of the standing egg. This new method promises to revolutionize rice planting in Japan.

Taking on the challenge of Mitsunae with a strong desire to sustain agriculture.

Nursery tray for Mitsunae (left) and conventional planting tray (right)

As the environment surrounding the agricultural sector continues to shift substantially, demands for cost reductions that lead to a sustainable business are increasing. In addition, to cope with the growing scale of agriculture and the trend toward an aging society, demand is growing for labor-saving methods. One of the technologies arising from these circumstances is the high-density sowing and transplanting (Mitsunae) system.

Normally, 75 to 100 g of seed rice is sown in a nursery tray; this system results in sowing and seeding at a rather high density of 250 to 300 g per tray. A rice transplanter capable of precision picking can transplant 3 or 4 seedlings per clump in the conventional manner. Thus, the number of nursery trays used for 10 ares is reduced from 20 to 22 trays (with the conventional method) to 5 or 6 trays. This system results in a remarkable reduction in cost, labor, while contributing to more effective use of time and space.

Starting with the producers’ perspective

We interviewed the key person involved in this project, Toshihiro Butta, President and Representative Director of Butta agricultural products corp.
Five years ago, Mr. Butta visited the rice fields of Eiji Hamada of Agri-star Onaga in Hakui, Ishikawa prefecture. Mr. Butta asked Mr. Hamada how many nursery trays were needed to plant 10 ares of rice seedlings. Mr. Hamada replied that 10 trays were needed to plant at a density of 200 g. Even in these circumstances, rice can be produced. So, in spring of the next year, they grew seedlings at a higher density and, by making adjustments to a conventional rice transplanter, tried planting 7 trays on 10 ares. Then, Kazunori Sawamoto, at that time the Chief Researcher of the Agricultural Experiment Station, Ishikawa Agriculture and Forestry Research Center (Ishikawa Agr. Exp. St.), and Hiroshi Isemura, Department Manager of Yanmar Agricultural Research Center visited the rice fields to see the planting work and decided to take part in this project.

Toshihiro Butta, President, and Hiroshi Isemura, Department Manager

The trial proved successful. In some locations, production reached 700 kg per tan (992 sq. m.).
Said Mr. Butta, “It is important that we not be too positive in our approach to conventional methods, and to always question and wonder whether our practices can be improved upon.”
Adopting this attitude can lead to successes like Columbus’ standing egg. Clearly, however, it is not an easy approach, as it is only human nature to take the path of least resistance and continue with our standard practices. Nonetheless, we must admit that Japanese agriculture cannot be easily sustained if we simply continue on our current path.

In Nonoichi, Ishikawa prefecture, Butta agricultural products corp. processes and markets its production from 28 ha of rice paddies, 0.7 ha of turnip fields, and 0.5 ha of white radish fields. Butta agricultural products corp. practices vigorous agricultural management through personal mail-order sales, commercial contract sales, sales of processed goods through shops of the head office and in Kanazawa Station, all the while accommodating current trends.
According to Mr. Butta, this technology might not have been developed in the days when koshihikari rice sold for 20,000 yen more per bale. It can be said that a strong willingness to sustain agriculture resolves the severe management challenge of reducing costs in order to survive.

A reduction in the number of nursery trays results in easier transfer and improved greenhouse availability while retaining the production quantity and quality at levels equivalent to what is produced with conventional methods.

The high-density sowing and transplanting (Mitsunae) system underwent demonstration testing at the Ishikawa Agr. Exp. Stn. in 2013 and 2014. In parallel with these tests, Yanmar developed rice transplanters capable of high-precision picking and transplanting. Butta agricultural products corp. conducted planting with this method throughout three growing seasons, with the current year marking the fourth season.
Planting starts with the sowing of 250 to 300 g of dry seed rice in a nursery tray. Butta agricultural products corp. sows 300 g of seed rice, raises seedlings for 15 to 17 days, and transplants them when they reached a foliar age of 2 to 2.3.
Assuming that 1.5 kg of seed rice is required for 10 ares as a standard, 20 nursery trays are required to sow 75 g with the conventional method. However, this new system makes it possible to sow 300 g, or four times the conventional quantity, using only 5 trays, or one-fourth the number of nursery trays required with the conventional method.
“Only fifteen nursery trays are required for 30 ares,” said Mr. Butta. “Therefore, with an 8-row rice transplanter, a single person can handle the task without any need to replenish the seedlings.”
No assistant is required, and the number of workers can be reduced during busy periods. Because the nursery trays are typically carried by women in the conventional method, this new approach can be considered a boon for women.

Raising seedlings at high density in a greenhouse

While the standard growing period is 35 days for 75 g of seedlings, it can be reduced to only 15 to 17 days with this method, resulting in improved greenhouse availability.
In the case of Butta agricultural products corp., the number of nursery trays can be reduced to one-fourth, and the growing period is shortened by half, which increases work efficiency eight-fold in total.
According to Mr. Butta, “When engaged in management of complex rice planting methods, using greenhouse space effectively can be a challenge. This method helps to solve this problem.”
High-density sowing causes growth to stall when the growth period exceeds 20 days. So, only young seedlings with leaves at an age of 2 to 2.3 should be planted. However, because this method excels in mat formation, it does not differ from conventional rice planting even when the picking block becomes small, unless the water is too deep. Also, following transplantation, “Rooting proceeds smoothly, and tillering is easy as younger seedlings are planted,” said Mr. Butta.
This has been known from experience, so the old knowledge was proven correct yet again through this trial.
“If technology with high reproducibility is available, verification is important,” noted Mr. Butta.
Verification of experience and tradition can be regarded as a way to free oneself from restrictions imposed by current common practice.

Following rice planting, the processes remain the same as those of the traditional rice planting method.
“Since the seedlings are small at the beginning, the problem is whether one can wait a period of about ten days. It is a matter of patience,” noted Mr. Butta.
This new method achieves results equivalent to the conventional method, in terms of both quantity and quality, without the need for special measures.

Rice transplanter introduced to handle high-precision picking in confined areas.

Yanmar has developed a rice transplanter that can accommodate the method outlined above.
“The claw width is reduced so that the machine can handle picking in a small area. This model has undergone precision machining and assembly with fewer gears to rattle, so any fluctuations in the amount picked are minimized,” said Mr. Isemura of the Agricultural Research Center.
As the target becomes finer, the machine’s accuracy must exceed that of conventional units. To meet this requirement, Yanmar has fully employed its precision machining technology. What’s more, it has undertaken a thorough study of conventional technologies. Through this process, the engineers were able to develop a machine that meets actual requirements in the field. This process has revealed the manufacturer’s high intrinsic abilities as well as its advanced technologies.
“This machine has the ability to plant seedlings to the same depth by automatically sensing surface unevenness on the rice planting land,” noted Mr. Isemura.
With this machine, anyone can handle a high-density sowing and transplanting (Mitsunae) system. The sowing machine can be adjusted simply by changing the number of feed gears.

New technologies on the horizon for large-scale and small-scale farmers (including part-time farmers)

The high-density sowing and transplanting (Mitsunae) system has the advantages of reducing the number of nursery trays, material costs, space requirements for nursery trays, and seedling transportation/replenishment time. What’s more, it provides a production quantity and quality equivalent to those of the conventional management method. This system is applicable to both large-scale and small-scale farmers, including part-time farmers. Unlike the direct sowing method, it handles plants in the same manner as conventional transplantation. Thus, this system is applicable to the planting of specially cultivated and organic strains of rice. Furthermore, since this system ensures a stable production quantity equivalent to that of traditional transplantation, it is suitable for contract planting.
“This method has the potential to capture 50% of transplantation in the future,” Mr. Butta says.
This novel approach will introduce innovations into the rice-planting process in Japan. We have high expectations for the new technology, which has overturned conventional thinking.

Source: “FRONT VIEW Forefront challenges,” AMJ, June 2, partially revised