Hi, Katrina,

Yes, rice wash is rich in basic nutrients for plant growth such as N, P, K but in the same time it is rich in sugars, mainly amidon but also other carbohydrates. In aerobic and anaerobic conditions, sugars-based waters or slurries are very good substrate for fermentation, either aerobic or anoxic, in the presence of various soil bacterias and fungi. In soil there is oxygen, so as we speak about an aerobic, acidogenic fermentation that leads to various organic acids, mainly C1-C4 volatile acids. It is known that an acid soil is much harmful to plants growth. This is why rice waters that are used for soil watering are more harmful than beneficial. On the other light, such waters are a very good substrate for anaerobic fermentation if used as dilution waters in anaerobic digesters, they definitely increase the effectivenss of biogas systems due to their sugar contents.

Rice contains starch which are mainly present in rice water. These starches are beneficial to plants, encouraging healthy bacteria that grow in the rhizosphere. Its ability to provide fast and instant energy while provide a essential source of vitamin B1 to the human body. It has presence of trace amount of N, P and K which also influence the plant growth. In some of the cultivar rice water has reported very trace amount of Fe and Zn.

The exact amount of these nutrient losses would depend on the type of rice, how much water was used in washing of the rice, and how rigorous was the washing done. But generally, washing rice causes rice to lose up to 7% protein, 30% crude fiber, 15% free amino acids, 25% calcium (Ca), 47% total phosphorus (P), 47% iron (Fe), 11% zinc (Zn), 41% potassium (K), 59% thiamine, 26% riboflavin, and 60% niacin.But what was lost from the rice is now gained by the water. Perhaps these leached nutrients now in the washed rice water could be beneficial to our houseplants. Nonetheless, the belief that higher plant growth can be encouraged by using washed rice water is supported by the findings of higher N and K content in the plant (as well as in the soil for K). Washed rice water do supply the essential nutrients of N and K, which are very much needed by the kangkung plant. With the additional supply of N and K nutrients, it can be expected that kangkung as well as other plants would respond favorably by having increased plant growth and yield.

Potential problems of using washed rice water

Admittedly, using water from washed rice will always be for domestic, household use. Using such enriched water for large-scale or commercial farming production systems would be impractical as it would require too much washing of rice! Nonetheless, domestic use of washed rice water, as stated earlier, is a good way to recycle water in the household rather than just discarding it down the drain.

The second potential problem is the washed rice water will have to used almost immediately. Leaving the water out in the open would encourage fermentation and create unwanted sour-like smell, though it would interesting to compare between fermented and unfermented rice water on our houseplants.The third potential problem is whether prolonged use of washed rice water on our plants would encourage the incidence and spread of pests (like rodents) and diseases.

Hi, Katrina,

Thank you for the interesting point.

Availability of starch and other nutrients like N, K, P and others, may encourage fermentaion & growth of

various type of soil microorganisms, including N2-fixing ones (bacteria & azollas etc.), further enriching

the soil with extra N2, to support photosynthesis and hence plant growth. Good luck.