How to save water

El Niño causes either drought or floods. To ease the drought effects brought about by El Niño, farmers can use evaporation suppressants in rice fields.

Evaporation suppressants save water in the farm. They remove water stress on crops, increase fertilizer efficiency, and optimize water temperature when it is cold. An evaporation suppressant is a non-toxic and biodegradable chemical substance that comes in the form of paste, slurry, and solution with organic solvent. It prevents water loss by forming a thin continous film above the water surface. The most readily available evaporation suppressant is a cetyl-stearyl alcohol mixture prepared from coconut oil.

The evaporation suppressant was a product of an inter-agency project among the University of the Philippines Los Baños (UPLB), Philippine Rice Research Institute (PhilRice), and the Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD) through the leadership of the late Dr. Maximo Baradas of PhilRice and Dr. Milagros M. Peralta of UPLB.

Evaporation suppressant saves up to two million liters of water/ha per season. This amount of water can already irrigate an additional one fourth ha of rice field using the same amount of irrigation water available. It also maintains optimum water temperature needed for faster growth of rice plants. It reduces nitrogen loss while facilitating oxygen exchange.

In rainfed rice fields, use of evaporation suppressant can minimize water stress during the two to three week dry spells during rainy season.

Most importantly, evaporation suppressant is environment-friendly and safe.

Evaporation suppressant can be applied not only in rainfed and insufficiently irrigated lowland rice areas, but also in small farm reservoirs, municipal water reservoir, small water impounding projects, and aquaculture ponds.

Using evaporation suppressant is easy. First, determine the actual size of the rice field or reservoir. Second, measure the necessary amount of evaporation suppressant for the area. Finally, pour the evaporation suppressant into the different parts of the rice field or reservoir.

In rice fields with standing water, apply the suppressant one week after transplanting, two weeks after transplanting, one week after flowering, and two weeks after flowering. In reservoirs and fishponds, the mixture is applied weekly until the onset of the rainy season.

For better results, other complementary practices could be adopted and these are establishing wind breaks and increasing the dike’s spillway height to at least 10 cm from the ground level.

The solution form is the most highly recommended for use in the field because the film spreads rapidly in the field. This solution form should not be used at floodwater temperature below 20ºC because of the tendency of the suppressant to solidify before it can completely spread. Also, evaporation suppressant should not be applied in running water because it will be dispersed instead of staying on the surface.

Field-testing and technology demonstration on evaporation suppressants showed positive results. Rice yields increased in almost all 15 provinces where the techno-demo sites were established. During the 1998 wet season cropping the techno-demos consisted of two-ha ricefields in each of the following provinces: Ilocos Norte, Isabela, Nueva Ecija, Bulacan, Tarlac, Laguna, Iloilo, and North Cotabato. In these provinces, the average increase in yield was 18 cavans/ha.

Yield increase was due to reduced water stress when evaporation suppressant was used. The suppressant prolonged the availability of moisture in the ricefields one to five days longer compared with ricefields without evaporation suppressant. The evaporation suppressant was also found effective in reducing evaporation in evaporation pans and reservoirs.

Evaporation suppressants can be bought at AGR Lotus, Agribusiness Division, Km 16 Republic Steel Tube Compound, Alabang-Zapote Road, Pamplona, Las Piñas City at telefax numbers (02)827-7709. For other details, contact Dr. Milagros M. Peralta, Institute of Chemistry, UP Los Baños at tel. Nos. (049) 536-2220/2435 or PCARRD Los Baños, Laguna at tel. Nos. (049) 536-0014 to 20. – Ofelia Domingo, S&T Media Service.