Color Chart Promotes Fertilizer Efficiency for Asian Rice Farmers

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Access to nitrogen fertilizers can mean the difference between success and failure of an entire year’s investment for an Asian rice farmer. But overuse of fertilizer can degrade the long-term quality of the soil and water resources on which they depend—and can eat away at precious little profits. But researchers have discovered that rice leaves themselves can give clues about how much nitrogen is needed for optimal yield.

A new 4-panel leaf color chart (LCC) that corresponds to actual colors of rice leaves has been developed for rice cultivation in Asia—the chart was created by the Irrigated Rice Research Consortium (IRRC) in collaboration with the University of California Cooperative Extension (UCCE). The LCC consists of plastic panels, each with distinctly different shades of green—ranging from yellowish green to dark green. LCCs can be used by farmers in the field to gauge how much nitrogen fertilizer is needed for efficient use, and to maximize rice yields.

The LCC is used at critical growth stages by simply holding a rice leaf against the panels. A farmer can tell whether the crop has received too much nitrogen or is nitrogen deficient, by comparing leaf color too LCC panels. This provides real-time guidance for when to apply, and when not to apply fertilizer. Any color outside the range of the four panels would signal extreme nitrogen deficiency or excess.

“The challenge for poor smallholder farmers is how to plan for the application [of nitrogen] in an environment that is very versatile,” says Dr. Christian Witt, IRRC researcher in the development of LCC. “Small changes in soil fertility gradient from field to field will have a great impact on the nitrogen demand of the crop. Also, you have seasonal variation. In the dry season the yield potential is higher, so the plant requires more nitrogen.In the wet season, soil fertility is usually sufficient to cover a significant portion of the nitrogen demand. And not every wet season or dry season is the same. So it is extremely difficult to plan for your nitrogen requirement before the season.”

The new LCC can be used for all high-yielding rice varieties in Asia. Guidelines on the use of the chart have to be adjusted for local conditions. The critical leaf color—signaling optimal growth—depends on region, rice variety, season, and cropping method. A prescribed amount of nitrogen is applied when the color of rice leaves falls below the critical LCC value.

This effective, low-cost tool helps farmers improve their nitrogen fertilizer management, improving their prospects for success. “Smallholder farmers benefitted from the low cost [about US$1 a unit] and the learning that was associated with it,” says Witt. “It wasn’t just the chart, but also learning when the plant really needs the nitrogen and observing leaf color. Once farmers used the LCC for two or three seasons,{they} adjusted their nitrogen management, and they developed an eye for the optimal green leaf color.Managing soil fertility and having adequate tools to be able to communicate soil fertility to farmers is essential to sustainable agriculture and food security.”

The chart and guidelines for using the LLC are being promoted in many Asian countries through the IRRC. More than 250,000 units of the 4-panel LCC are due to be distributed to rice farmers in Bangladesh, China, India, Indonesia, Myanmar, the Philippines, Thailand, and Vietnam. Further research is being conducted to establish whether the LCC could also be used for nitrogen management in maize.

To read more about innovations in rice cultivation see: Gleanings from Des Moines: Farmer Testimonials of Sustainable Rice Intensification, System of Rice Intensification: A viable solution to produce more rice, using less water, Messages From One Rice Farmer to Another, Keeping the Rice from Going to the Birds, and Encouraging Consumption of Local Rice by Improving Local Quality and Processing.

Matt Styslinger is a research intern with the Nourishing the Planet project.

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