Information from 1999 Missouri Rice Research Update, February 2000.

Nitrogen Timing on Yields of Cypress, Drew and Jefferson Rice

Gene Stevens, David Dunn, Todd Reed, and Tina Gladbach

Abstract

Applying all of the nitrogen for the season preflood can save farmers about $10 per acre in airplane costs by not having to make mid-season applications. However, a reduction in rice yields with this program could more than offset the saving benefits from not making mid-season application costs. An experiment was conducted at the Missouri Rice Farm in Glennonville to determine the most effective nitrogen timings on Cypress, Drew, and Jefferson rice. Test results indicated that multiple applications of urea produced greater yields than one-time N applications on Drew and Jefferson.

Introduction

N application timing is an important issue to rice producers, because as costs of production continue to increase, money can be saved with an effective application plan. One-time treatments may appear to save money by reducing application costs. However, results have shown that multiple applications may increase yields enough to offset these additional costs.

Materials and Methods

All three tested varieties were drill seeded on May 11, 1999. Recommended N rates were applied to each variety (Cypress and Jefferson, 150 lb./acre; Drew, 135 lb./acre). These rates were applied at four different stages-preplant, preflood, 1/2-inch internode elongation (IE), and 1/2-inch IE + 1 week. The experimental design was a randomized complete block with four replications.

Results

For each variety, five treatments involved multiple applications of urea, while one involved a single-application of N fertilizer (Table 1). In Cypress, the one-application treatment had the highest yields, and would appear to be the most economical N timing program. However, results from last year showed that one-time applications of N on Cypress did not do as well as split applications.

Drew test results indicate that a single-application program would be largely ineffective. A three-treatment program (preflood, 1/2-inch IE, 1/2-inch IE +1 week) appears to be the best option.

Jefferson test results showed that a single-application of urea resulted in relatively good yields, although a three-application program (preplant, preflood, 1/2-inch IE) resulted in higher yields.

Conclusion

This experiment provides valuable information into N timing rates. While it may be less expensive to apply the total amount of fertilizer at once, yield consistency and/or yield increases brought about by multiple-application programs usually outweigh fertilizer application costs. Next year we will study reducing the rates on the one-application treatments. Research in other states suggests that less total N should be applied when the entire N for the season is applied preflood.

Table 1. Effects of nitrogen timing on yields of Cypress, Drew, and Jefferson varieties.

   Variety      Preplant  Preflood  -inch IE   - inch     Total      Yield
                                                + 1 week   Nitrogen   bu/Acre
               --------------------lb N per acre--------------------  
   Cypress          0        90        30        30          150        173
   Cypress          0        90        60         0          150        163
   Cypress          0       105        45         0          150        172
   Cypress          0        60        45        45          150        161
   Cypress          0       150         0         0          150        172
   Cypress         50        50        50         0          150        163
   Drew             0        75        30        30          135        162
   Drew             0        75        60         0          135        166
   Drew             0        90        45         0          135        160
   Drew             0        45        45        45          135        198
   Drew             0       135         0         0          135        129
   Drew            45        45        45         0          135        165
   Jefferson       50        50        50         0          150        179
   Jefferson        0        90        60         0          150        167
   Jefferson        0       105        45         0          150        169
   Jefferson        0        60        45        45          150        158
   Jefferson        0       150         0         0          150        169
   Jefferson       57        57        57         0          170        165

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