According to research from Malaysia’s Universiti Putra, fermented rice water can increase plant growth by 12-26% and provide nutrients comparable to some commercial fertilizers. This simple kitchen leftover can give your garden a real boost when used the right way. Keep reading to learn how it works and how to make it.
What Is Rice Water for Plants? The Science in Plain English
Simply put, rice water is a DIY fertilizer you make by rinsing or soaking rice in water. You can use the water immediately. Or, you can ferment it for about three days to boost the nutrients, increase beneficial microbes, and lower the pH for acid-loving plants. Along with the big three nutrients–nitrogen, phosphorus, and potassium–rice water also delivers a range of micronutrients, making it a surprisingly nutrient-dense fertilizer you can make at home.
Benefits of Rice Water for Plants (What Research Actually Shows)
Research shows rice water gives plants a solid nutritional boost. Ferment it, and the benefits get even better, increasing nutrient levels by 7.4% to 204%, depending on the specific element. Here are a few specific nutrient densities for unfermented rice water, fermented rice water, and tap water in milligrams.
Nutrients in Rice Water Compared to Tap Water
| Nutrient | Unfermented RW | Fermented RW | Tap Water |
| Nitrogen | 154.91-165.31 | 178.49 – 261.73 | 26.08 – 34.32 |
| Phosphorus | 87.16 – 94.68 | 198.60 – 221.02 | 0.03 – 0.07 |
| Potassium | 103.90 – 132.32 | 126.58 – 145.02 | 5.59 – 5.89 |
| Magnesium | 26.14 – 29.66 | 63.59 – 70.03 | 0.91 – 1.03 |
| Calcium | 6.42 – 10.62 | 13.08 – 14.14 | 10.89 – 11.01 |
| Zinc | 0.06 – 0.08 | 0.24 – 0.26 | trace |
The fermentation process causes beneficial bacteria to break down complex compounds, making them more bioavailable for the plants. The process also lowers the pH of the rice water, making it especially beneficial for acid-loving plants like tomatoes, blueberries, and azaleas. Leafy greens like lettuce and spinach thrive on it, and many vegetables grow taller, leafier, and more productive than untreated plants.
DIY Plant Fertilizer: How to Make Rice Water (Fresh vs. Fermented)
You can easily make your own rice water fertilizer at home. Here’s how to prepare both types for maximum plant benefits.
Fresh Rice Water Method
- Wash rice until the water runs clear.
- Save the wash water.
- Use immediately on plants–undiluted.
- Cook the remaining rice for a future meal.
Fermented Rice Water Method (Recommended):
- Follow the first two steps above to create basic rice water.
- Fill a clean glass jar ¾ full with rice water.
- Cover loosely with a cloth so it can breathe.
- Let ferment at room temperature for 3-5 days, away from direct sunlight.
- The solution is ready when it develops a slightly sour smell and becomes translucent.
- Store in the refrigerator for up to 7 days.
How to Use Rice Water Safely on Plants (Dilution, Frequency, Timing)
Fermented rice water is potent, so follow these steps to keep your plants safe.
- Dilute the fermented rice water 1:1 with clean water before applying to your plants. Note: Fresh rice water can be used undiluted in most circumstances.
- Apply no more than once every couple of weeks during the active growing season. Do not use during dormant or slow-growth periods.
- Apply to moist soil in the early morning or evening.
- Discontinue use if you notice soil hardening, unpleasant odors, or increased pest activity.
- Do not use on excessively wet soil.
Which Plants Benefit Most from Rice Water
Since rice water contains the nutrients found in commercial fertilizer preparations, most indoor and outdoor plants can reap benefits from it. One study recommends rice water particularly for vegetables. However, it’s been shown in other studies to increase the growth and fruiting of other plants, too. And since it has an acidic pH, fermented rice water is particularly valuable for acid-loving plants like blueberries, azaleas, and tomatoes.
Not every plant will love rice water. Slow-growing perennials and plants that prefer neutral or alkaline soils may see little benefit—or even stress—because of its acidity.
The Bottom Line on the Benefits of Rice Water for Plants
Used the right way, fermented rice water is a science-backed, budget-friendly fertilizer that performs as well as, or better than, commercial fertilizers. When coupled with other best gardening practices like proper soil management, rice water can reduce the need for commercial fertilizers and provide beneficial nutrients and microorganisms. When properly prepared and applied, you can see the difference in your plant’s growth and fruit production.
