Introducing the farmer-friendly moisture meter

Imagine the trouble of growing your seedlings, feeding them with nutrients, and getting rid of pests and diseases, only to have your rice rot or overdry after harvest? Well, the key to preventing that postharvest nightmare from happening is accurate moisture determination.

Moisture determination is the most critical factor when drying, storing, and processing rice seed and grain. Paddy or unhulled rice needs to be dried without delay to moisture content below 14% to prevent rapid deterioration after harvest. Rice seeds should be dried to 12% moisture content or below to maintain optimum germination levels. In most rice mills, the maximum amount of milled rice is obtained when the paddy is milled at 14% moisture content. When grains are overdried to lower moisture content, the producers also lose money from excessive weight loss. During storage, the moisture content needs to be monitored to prevent grains from absorbing water from the surrounding air, especially in the wet season when relative humidity is high.

The cheapest commercial moisture meter costs approximately US$200, far more than rural budgets permit. Farmers and processors therefore rely on estimating the moisture content; one way is by biting the grains. Consequently, the International Rice Research Institute’s (IRRI) Agricultural Engineering Unit developed an affordable moisture meter that uses standard electronic components and can be produced locally.

The low-cost moisture meter is designed as a decision-making tool with an analog display, and with ranges instead of a number scale indicating the appropriate action to be taken. The red section for moisture content above 14% indicates that the paddy needs to be dried. The green section ranging from 12% to 14% moisture content tells the user that paddy is ready for milling, and is also safe for short-term storage of grain. The blue section for moisture content below 12% indicates safe storage moisture content for seed. The moisture meter is thus a decision-making tool and not intended for commercial purposes.

Eugene Aquino, the IRRI engineer who designed the electronic circuit of the moisture meter, points out that the accuracy is within + 0.5% compared with data gained using the oven method, and is comparable with that of regular commercial moisture meters. It is calibrated for paddy, other cereals, and coffee.
The moisture meter costs $30, and feedback obtained from villages in Indonesia, Cambodia, and Vietnam showed that this is affordable for farmers’ groups or cooperatives. So far, we have provided around 175 units to our collaborators in the national agricultural research and extension systems and projects in partner countries. It is currently being field-tested by seed producers and in several villages in Cambodia and Vietnam.

The moisture meter can help farmers to reduce losses and maximize profits from their rice harvests. Two small manufacturers in the Philippines can now produce the moisture meter, and one in Cambodia has made several prototypes and has sent them for testing to IRRI.

Farmers and extension officials test the moisture meter during a training in Hau Thanh Village, South Vietnam. (Photo by M. Gummert)

Martin Gummert (m.gummert@cgiar.org) 

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