Crop Program · Rice

In a flooded field, only one form of nitrogen survives: ammonium.

Flooded rice soil is chemically different from every other field on this site. Nitrate applied to a rice field is denitrified and lost to the atmosphere — it is never used. Because getting this right depends on your water management as much as your rate, we build every rice program with you.

The science

Flooded soil rewrites the nitrogen rules.

CDFA FREP’s Water Seeded Rice guidelines describe a nitrogen system unlike any other crop: once a field is flooded, the soil turns anaerobic, and any nitrate present — whether residual or newly nitrified — is denitrified and lost to the air. Only ammonium-form nitrogen (urea, aqua ammonia, ammonium sulfate) survives and is actually taken up. Because of this, the pre-plant soil nitrate test used on nearly every other crop is not useful for rice: whatever nitrate is measured will be gone once the field floods. Nearly all nitrogen is instead applied pre-plant and chiseled 3–4 inches into the soil, as close to flooding as possible, where it is protected from both volatilization and denitrification.

150 lb

N/acre — the FREP-cited state average total rate

3–4″

incorporation depth that protects ammonium from loss

~60%

of accumulated nitrate lost when a drained field is reflooded

Why this favors an ammoniacal, well-placed program. Phytamin® liquids are ammoniacal nitrogen — the exact form flooded rice soil can actually retain. Phyta-Grow®’s protein-based nitrogen also mineralizes to ammonium, which stays available as long as it remains in the reduced soil layer rather than surfacing into aerobic conditions. But placement is what makes or breaks a rice program — depth, timing relative to flooding, and drain management matter more here than the rate itself, which is exactly why this gets built with an agronomist rather than published as a fixed recipe.

Demand context

How much nitrogen rice needs.

These CDFA FREP figures are planning context, not a program. Actual demand depends heavily on your water management, yield goal, and straw history, which is why every COFI rice program is built to your field.

Water management scenario	Typical N
Continuously flooded, single pre-plant application (most common)	~150 lb N/acre average; 140–190 lb/acre range for maximum yields
Field drained >1 week early season (split program)	Pre-plant portion, plus midseason topdress capped near 30 lb/acre
Straw incorporated with consistent winter flooding	10–20 lb/acre less than the above, from organic matter mineralization

Water management scenario Continuously flooded, single pre-plant application
Most common

Typical N ~150 lb N/acre average; 140–190 lb/acre range for maximum yields

Water management scenario Field drained >1 week early season
Split program

Typical N Pre-plant portion, plus midseason topdress capped near 30 lb/acre

Water management scenario Straw incorporated with consistent winter flooding

Typical N 10–20 lb/acre less than the above, from organic matter mineralization

Every one of these numbers shifts with the factors below — which is why rice resists a one-size-fits-all program:

Water/drain management Yield goal & variety Straw incorporation & winter flooding history Soil mineralization potential Incorporation depth & timing accuracy

An organic-system credit, built in. Rice straw incorporation combined with winter flooding measurably increases the nitrogen supplied by soil organic matter mineralization — FREP guidelines credit this as roughly 10–20 lb/acre less fertilizer nitrogen needed. In an organic system already leaning on that biological cycle, a Phytamin® and Phyta-Grow® program supplies the well-placed remainder rather than the whole load.

Let’s build your rice program.

Because the right rate and placement depend on your water management, yield goal, and straw history, we don’t publish a single number. A COFI agronomist will build a program around ammoniacal Phytamin® liquids and Phyta-Grow®, matched to your flooding schedule and field.

Talk to a COFI agronomist

Sources

Flooded-soil nitrogen chemistry, application rate, and placement guidance: CDFA FREP California Crop Fertilization Guidelines, Water Seeded Rice (cdfa.ca.gov/is/ffldrs/frep). Drain-period denitrification research: Linquist, B.A., Koffler, K., Hill, J.E., van Kessel, C., “Rice Field Drainage Affects Nitrogen Dynamics and Management,” California Agriculture. Broader management context: Williams, J.F., “Rice Nutrient Management in California,” UC ANR Publication 3516. Product analysis: Phytamin® and Phyta-Grow® CDFA-registered labels, California Organic Fertilizers.

This page is planning context, not a prescription. Rice nitrogen rate, placement depth, and timing must be set for each field using its water management, yield goal, variety, and straw history. Finalize your program with a COFI agronomist and your PCA or Certified Crop Adviser.

DOWNLOAD RICE CROP PROGRAM PDF

THE ORGANIC AGRONOMIST

Growing Organic Rice: Protect Nitrogen with Placement and Water Management

Explore how fertilizer placement, flooding schedules, and nitrogen availability work together to help organic rice growers improve nutrient efficiency and reduce avoidable nitrogen losses.

Read the Rice Article

Rice field decision chart outlining how fertilizer placement, flooding schedules, field conditions, and crop monitoring guide nitrogen management.