Nitrogen Fertilizer Rates and Timing for Rice

Rice yield is affected greatly by nitrogen application rates and the timing of applications. The severity of diseases, lodging, crop maturation and grain quality (milling yield) are also seriously influenced by nitrogen rates and timing. Research in Missouri shows rice yields, and especially rice quality, to be negatively affected by excessive rates and late applications of nitrogen fertilizer. The varieties Mars, Katy and Kaybonnet are especially hurt by overfertilization with nitrogen.

We strongly recommend the use of the Plant Area Measurement Board at mid-tillering and at mid-season to determine whether and how much nitrogen to apply at mid-season. The DD⁵⁰ Rice Growth Prediction Program is essential for use of the Plant Area Measurement Board. Contact and Extension agronomy specialist for assistance.

The following table provides the recommended rates and timing for commonly grown rice varieties when rice follows soybeans in rotation. Read the qualifiers following the table for adjustments for other rotation sequences and special conditions.

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VARIETY         TOTAL N  PREFLOOD N    1ST MIDSEASON N    2ND MIDSEASON N
                                    (1/2-inch internode) (7-10 Days Later)
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Very Short Season Maturity
Adair             120        60              30                 30
Alan              135        75              30                 30
Jackson           135        75              30                 30
Jodon             135        75              30                 30
L202              135        75              30                 30
Maybelle          135        75              30                 30
Millie            135        75              30                 30
RT 7015           135        75              30                 30
Tebonnet          110        50              30                 30
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Short Season Maturity
Bengal            150        90              30                 30
Gulfmont          180       120              30                 30
Kaybonnet         135        75              30                 30
Lacassine         150        75              30                 30
LaGrue            135        75              30                 30
Mars              110        50              30                 30
Orion             135        75              30                 30
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Midseason Maturity
Cypress           150        90              30                 30
Drew              135        75              30                 30
Katy              135        75              30                 30
Lemont            180       120              30                 30
Newbonnet         135        75              30                 30
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Late Midseason  Total N  Preflood N (3/4-inch internode) (7-10 Days Later)
Lebonnet           90        45              45                  0
Skybonnet         110        50              30                 30
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• If rice is following rice, bare ground fallow (set-aside) or cotton, increase the preflood N by 20 lbs.
• If following grain sorghum, wheat or fallow with a good vegetative cover, increase the preflood N by 10 lbs.
• If rice is growing on a very fertile soil with high nitrogen release (often with a history of lodging), decrease the preflood N by 10 lbs.
• If rice is following long-term pasture or fish, or is in the first year after clearing the land, omit preflood nitrogen altogether.
• If the stand is thin (6 to 8 plants per square foot), increase the preflood N by 20 lbs. DO NOT increase the preflood rate because of a thin stand if the variety is Adair, LaGrue, Lebonnet, Tebonnet or Skybonnet.
• Use the Plant Area Measurement board at mid-tillering and again at beginning internode elongation (according to your DD⁵⁰ Report) to determine whether to add more or less N at midseason than recommended in the above table.
• Especially if plant color and height indicate nitrogen deficiency, use the Plant Area Measurement Board at mid-tillering and at beginning internode elongation to determine whether to apply as much as 15 lbs. extra N at either or both midseason application times.
• On varieties especially susceptible to sheath blight and blast, especially when there is a history of these diseases in a given field and when current weather conditions (warm, humid and wet) favor these diseases, reduce midseason N.