Fertilizer Use Down, Rice Quality Up…A Smart Rice Transplanter That Catches 'Four Rabbits' Emerges

(Korea Agricultural Technology Newspaper = Reporter Lee Hyun-woo) Amid the double burden of disruptions in fertilizer raw material supply caused by instability in international commodity supply chains and labor shortages resulting from the aging rural population, a domestic research team is drawing attention for creating a breakthrough through data-based precision variable-rate fertilization technology.

The Rural Development Administration (Administrator Lee Seung-don) announced on May 27 that it had developed a ‘smart rice transplanter that adjusts site-specific customized fertilizer application rates simultaneously with transplanting,’ which identifies paddy soil conditions in real time and automatically adjusts fertilizer application amounts, and has begun field deployment. The technology is being evaluated as a product that simultaneously catches the so-called four rabbits: cost reduction, labor relief, environmental protection, and high-quality rice production.

▲Resolving soil heterogeneity within fields…integration of four major data-based innovative technologies 'from analysis to control'=Conventional fertilization practices have remained at the level of treating an entire paddy as a single average value and uniformly applying slow-release fertilizer.

However, even within a single plot, the amount of nutrients needed by rice varies depending on drainage, organic matter content, and soil fertility. As a result, excessive fertilizer was applied to areas already rich in nutrients, causing rice plants to grow too tall and lodge or become vulnerable to pests and diseases, while residual fertilizer components flowed into streams and caused water pollution. On the other hand, areas lacking nutrients showed poor growth, leading to variations in overall quality and yield.

To fundamentally solve these problems, the newly developed smart rice transplanter △organically combines four core technologies in four stages: calculating the appropriate fertilization amount (analysis), generating a fertilization map (prescription), recognizing real-time farm work location (judgment), and controlling the optimal fertilization amount (control).

In the first stage, the ‘appropriate fertilization amount calculation’ process links soil information analyzed by city and county agricultural technology centers and the Korea Agriculture Technology Promotion Agency with the Rural Development Administration’s soil environment information system “Heuktoram” data (fertilizer use prescription information). Through this, the nutrient status of each plot is identified and the distribution of nutrients across eight items, including pH, organic matter, and available phosphate, is precisely examined.

In particular, the algorithm also reflects physical characteristics such as particle size and density of 16 types of slow-release granular fertilizers distributed in Korea, deriving the appropriate fertilization amount by calculating differences in discharge volume by fertilizer product.
Next, in the ‘fertilization map generation’ stage, analysis data are used with the spatial interpolation method (Kriging) to determine the proper input amounts of key components such as nitrogen, phosphate, and potassium for detailed unit zones within a plot, and to build a digital ‘fertilization prescription map.’ The fertilization prescription map is organized by plot or by unit zones according to the rice transplanter’s working interval.

When actual transplanting begins, the ‘real-time farm work location recognition’ technology is activated. By using high-precision satellite positioning information (RTK-GNSS), location error was dramatically reduced to within ±2 cm, and the transplanter’s driving position is tracked in real time to deliver accurate fertilizer amount information matched to the relevant zone to the control device.

Finally, in the ‘optimal fertilization amount control’ stage, the controller’s computing unit linked to a touch-type UI display adjusts motor output in real time. According to the values set in the prescription map, it automatically adjusts fertilizer application amounts in real time with high-precision control within ±5% and applies them accurately to the paddy surface.

▲Economic viability proven in Hwaseong demonstration test…29% less fertilizer yet 10% higher yield=The results of a demonstration test conducted by the research team at a rice-growing farm in Hwaseong were encouraging. Compared with the conventional method, fertilizer use per 1 hectare fell by 29%, and because transplanting and fertilization were carried out simultaneously and precisely, fertilizer application time was also shortened by as much as 40%.

Management costs and labor were greatly reduced, but productivity and quality improved. As a result of intensively supplementing nutrient-deficient zones and preventing excessive fertilization, yield instead increased by 10%, while yield variation by zone decreased by 33%.

In particular, this technology offers a major advantage in meeting rice grade and protein content standards under notices issued by the Ministry of Agriculture, Food and Rural Affairs. By appropriately controlling nitrogen input by zone, which determines eating quality, it lowers the protein content of rice and has been evaluated as proving its value as a ‘quality management-type agricultural machine’ capable of stably producing high-quality rice.

The Rural Development Administration projected that if this smart rice transplanter is introduced across the nation’s rice cultivation area (700,000 ha), it could generate enormous savings in agricultural input costs amounting to about 560 billion won annually (800,000 won per ha).
 

▲'Modular' and compatible with existing agricultural machinery…improves field acceptance and responds to aging=It is also practical for field application. This variable-rate fertilization control device was produced in a detachable ‘modular’ form. Therefore, farms that already own rice transplanters equipped with side-band fertilization units can convert them into smart rice transplanters simply by additionally installing the control module, without needing to purchase large new equipment, reducing the financial burden.

However, application is limited for old and outdated rice transplanters that do not have side-band fertilization units or are difficult to retrofit with electronic control systems, so measures to expand compatibility by model are expected to be prepared in the future.
Concerns in the field over the cost of soil sample analysis for detailed zone prescriptions have also been resolved. Free analysis services are available through support from city and county agricultural technology centers where farms are located, and based on a 1,200-pyeong paddy, only about 10 representative-value samples need to be collected and used, so the burden on farmers in terms of effort or actual additional costs is not significant.

At the briefing that day, Seong Je-hoon, president of the National Institute of Agricultural Sciences under the Rural Development Administration, emphasized, “The smart rice transplanter, as a data-based precision agriculture technology, will be of great help not only in reducing labor and costs, preventing water pollution, and producing high-quality rice, but also in strengthening farmers’ ability to respond in situations like the current fertilizer supply crisis.” He added, “It is highly meaningful that, amid the rapid reorganization of the global agricultural machinery market around smart technologies, we have raised the level of domestic precision agriculture technology to one equal to that of world-leading countries,” and said, “We will continue to do our utmost in developing agricultural technologies and distributing them to the field to realize sustainable future agriculture.”

Meanwhile, the Rural Development Administration plans to complete system improvements and technology advancement by 2027 in cooperation with industry in order to rapidly commercialize and distribute the smart rice transplanter developed this time. In addition, in 2028 it plans to quickly spread this technology to rice-growing farms nationwide through a new technology dissemination project.