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Determining Preflood Nitrogen Rates for Rice

May 23, 2014
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By Trenton Roberts, Research Assistant Professor, Crop, Soil & Environemntal Sciences, University of Arkansas

It is that time of year to start thinking about applying preflood nitrogen (N) to rice. If your rice has been planted recently or has recently emerged I would encourage you to consider taking N-STaR (Nitrogen Soil Test for Rice) soil samples to determine your season total N rate as well as your preflood N rates. N-STaR is the first field-specific N soil test for rice and has been developed for silt loam as well as clay soils. Already this season we have seen a large number of fields, especially on clay soils, that have recommended considerably lower N rates than the producer had intended to apply. Using the N-STaR program to guide N fertilizer recommendations in rice is a great way to see if you are on track with your N fertilization program or see where you can potentially benefit from lowering your N rates or increasing your N rates and increasing your yield.

For those producers who are too close to flooding and cannot take N-STaR samples please see the attached 2014 Recommended N rates and Distribution for Rice Varieties in Arkansas. This document can also be found under the publications tab at the Arkansas Row Crops Blog or under Rice Production Page on the newly renovated University of Arkansas Division of Agriculture Cooperative Extension Service Website. This document provides variety specific "generalized" N rate recommendations for the commonly grown rice varieties in Arkansas.

Major changes to this year’s list are the inclusion of two popular varieties Rice Tec XL 753 and Mermentau. Over the past few seasons XL 753 has been a very consistent variety with high yield potential. Variety x N trials have indicated that the N needs for this variety are similar to CL XL 745 and will require 150 total units of N per acre (120 units preflood followed by 30 units at boot) to maximize yield on silt loam soils following soybean in rotation (please see guidelines for N rate adjustments based on soil texture and previous crop). Similar to Cheniere and Cocodrie, Mermentau has a recommended season total N rate of 150 total units of N per acre (105 units preflood followed by 45 units at midseason) and has also shown to be well adapted and have high yield potential. Another change to this year’s format is the addition of a column that outlines Optimum Preflood N rates for producers who can flood timely and maintain a permanent flood for 3 weeks following flood establishment. The Optimum Preflood N application can allow producers that meet the requirements for timely flood establishment and maintenance to apply all of their N preflood and eliminate the need for a midseason N application, while saving N fertilizer and maintaining yield potential.

Several varieties have been removed from the 2013 list because they were either outdated or producers are no longer able to obtain seed for these varieties. The varieties that have been removed from the list are CL 131, CL 162, CL 171 AR, CL 181 AR, Neptune, Templeton and Trenasse. In the event that you or one of your producers has planted one of these varieties and needs guidance on recommended N fertilizer rates and distribution please feel free to contact myself Trenton Roberts (tlrobert@uark.edu) or Jarrod Hardke (jhardke@uaex.edu) for more information.

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RELATED TOPICS: Other Crops, Rice, Inputs, Fertilizer

 
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