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Long-Term Continuous Cropping Experiment (LTCCE)

Increasing soil health and productivity of rice crops
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.
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.
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 (later known as Crop Manager) 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.
Other discoveries from the LTTCE
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. 
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.
Appropriate fertilizer is use can boost yields without negatively affecting soil health.