Information from 2000 Missouri Rice Research Update, February 2001.

Nitrogen Timing on Yields of Cypress, Drew and Cocodrie Rice

Gene Stevens, David Dunn, Alan Sheckell, Chris Moylan

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 Cocodrie rice. Two year average test results indicated that a single N application on Cypress produced similar yields to multiple applications of urea. Drew consistently produced higher yields with split applications. One year results with Cocodrie showed that one-time N application produced the highest yield.

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. The cost of urea increased from $175/ton in 1999 to $260/ton in 2001. 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.

Cypress, Drew, and Cocodrie were drill seeded on May 8, 2000. Recommended total N rates were applied to each variety (Cypress and Cocodrie, 150 lb/acre; Drew, 135 lb/acre). The treatments were different timings and splits of nitrogen applications. Rates were applied at four different stages- preplant, preflood, ½-inch internode

elongation (IE), and ½-inch IE + 1week. The experimental design was a randomized complete block with four replications.

For each variety, five treatments involved multiple applications of urea, while one involved a single-application of N fertilizer (Table 1). In 1999, there was not much difference in yields from application timing on Cypress. In 2000, the one-application treatment had the highest yields, and would appear to be the most economical N timing program for Cypress.

Drew test results indicate that a single-application program would be less effective. A three-treatment program (preflood, ½ inch IE, ½ inch IE + 1 week) appears to be the best option for Drew.

In 2000, Cocodrie test results showed that a three-application program resulted in relatively good yields, although a single-application of N resulted in higher yields. This was the first year that we tested Cocodrie.

This experiment demonstrates that rice yield response to N timing can be variable. In 1999, results showed that multiple application programs outweighed fertilizer application costs because of yield increases. However, results in 2000 showed that it was more profitable to use a one-time application program. Research in other states suggests that less total N should be applied when the entire N for the season is applied preflood. In Arkansas, the total N recommendation is reduced 40 lb N/acre for single application in most varieties.

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

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