A healthy soil ecosystem is needed for sustainable rice production. However, rice is very different from other crops because it is often grown in flooded fields where the soil is saturated for long periods of time.
What is unique with this system, as compared with other cropping systems without soil flooding, is the maintenance of soil organic matter. In addition, a flooded rice field is a favorable environment for nitrogen input through the biological fixation of atmospheric nitrogen gas by naturally occurring microorganisms.
However, both soil nutrients and organic matter must still be properly managed to sustain good yields through time.
Moreover, fertilizer often represents the highest input cost for rice farmers after labor, accounting for about 20% of the total cost of production. Soil nutrient knowledge can guide the development of practical tools to help farmers increase rice production and reduce costs through smart nutrient management.
IRRI established the Long-Term Continuous Cropping Experiment (LTCCE) immediately after its creation to determine the impact of growing irrigated rice continuously, season after season and year after year, on crop productivity and soil health.
The LTCCE is the most intensively cultivated—and undoubtedly the longest-running—field trial on rice in the world. First known as IRRI's Maximum Yield Experiment, the first crop of the LTCCE was seeded on 24 May 1962. Since 1966, three consecutive crops of high-yielding rice varieties have been grown annually during most years.
Moreover, the LTCCE also shows that, even with three rice crops a year, high yield can be sustained. Soil organic matter can also be maintained in the continuously flooded field. In a typical year, the total yield of three crops with balanced fertilization reaches up to 17 tons per hectare.
The Long-Term Continuous Cropping Experiment (LTCCE) has shown that, growing rice continuously—one crop immediately after the other—does not reduce soil quality in terms of organic matter, nor does it reduce productivity.
We have learned that, without the addition of nitrogen fertilizer, rice yields remain consistent at relatively low levels because of biological nitrogen fixation even after intensive cropping for 50 years. Moreover, the LTCCE has shown that intensive rice ecosystems can maintain soil organic matter—a remarkable feat considering that all aboveground crop residues are removed in the experiment. This occurs because the unique flooded soil environment in which rice is grown helps in retaining organic matter in the soil.
Importantly, the work shows that when fertilizer is used appropriately, yield can boost without negative impact on soil health.
Knowledge generated from the LTCCE has contributed to the development of tools for better crop and nutrient management in rice, such as the Nutrient Manager for Rice (NMRice). In 2012-2013, NMRice provided more than 30,000 recommendations on fertilizer use to rice farmers in the Philippines and Indonesia. Research indicates that, when NMRice practice is done by farmers, the increase in income averages to about US$100 per hectare per crop.
Farmer Carmelita Balmediano of Victoria, Tarlac, Philippines, used to apply a lot of fertilizer, which is not recommended at certain stages of the crop. When she tried the NMRice, she saved money because she had learned the right kind of fertilizer to use and the correct application of it that her land needed.
Another fellow farmer said he felt relieved that he used the NMRice to get recommendations for fertilizer application. He managed to save some money and his harvest improved by about one-half ton per hectare. This was a 14% increase in yield.
NMRice has been upgraded to the Crop Manager, which uses knowledge generated from the LTCCE. Crop Manager is accessible with a computer or a smartphone, and it delivers advice to farmers on optimal crop and nutrient management to increase production and reduce waste of inputs. It is available in the Philippines and Bangladesh and there are plans to roll it out across other countries.
Despite the successes that IRRI had achieved and continue to achieve, there’s still a lot of work that needs to get done and the Institute can’t do it alone. Funding plays a very important role on whether or not we could do more. This is where you come in.
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The LTCCE is the most intensively cultivated—and the longest-running—field trial on rice in the world. First known as IRRI's Maximum Yield Experiment, the first crop of the LTCCE was seeded on 24 May 1962. Since 1966, three consecutive crops of high-yielding rice varieties have been grown annually during most years.
This video shows time-lapse photography of the 136th and 137th crops grown from early May through November 2009.
- Rice and the environment
- Soil and nutrient management
- Crop and Environmental Sciences Division (CESD)