Information from 1999 Missouri Rice Research Update, February 2000.

Using Chlorophyll Meter and Plant Area Board to Monitor Plant Nitrogen Status

Gene Stevens, David Dunn, Brian Henson, and Chris Moylan

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Abstract

An experiment was performed at the Missouri Rice Farm near Glennonville to form calibration curves for Jefferson and Drew rice varieties using a chlorophyll meter and an area board.

Introduction

The use of the chlorophyll meter and area board can prove to be valuable tools in monitoring the growth and development of rice plants. In developing the calibration curve, the chlorophyll meter was used to determine the N levels of the plants, since a primary component of chlorophyll is N (see University of Missouri Extension Bulletin MP 729). The area board was used to determine average plant height and width.

Materials and Methods

Jefferson and Drew rice were drill seeded on May 11, 1999. Both varieties were tested at preflood application rates of 0, 30, 60, 90, 120, 150, and 180 lb./acre. Half included midseason applications of 30+30 lb./acre. The other half only included the first application.

The experimental design was a randomized complete block with four replications. Chlorophyll meter and area board readings were taken before applying midseason N to help determine the effects that the midseason application would have on the rice.

Results

Yield results from the experiment showed that in Jefferson rice, a single application of preflood N was preferableto the preflood in addition to the midseason application, averaging approx. 15 more bu./acre (Table 1).

Conversely, the Drew variety yields were higher in the plots where the midseason application was included, averaging 9 more bu./acre than those with only a single application.

Conclusion

This experiment illustrates the importance of carefully monitoring the growth, development, and fertilizer needs of different rice varieties. Without such knowledge, a producer may be inclined to use the same fertilizer strategy on all his rice, giving too much to some varieties, resulting in wasted money and greater susceptibility to disease; and not giving enough N to other varieties, resulting in unrealized yield potential. Chlorophyll meters and area boards provide relatively quick and accurate results when trying to obtain this data.

Table 1. Rice yields from chlorophyll meter/plant area board calibration test.

     Variety            Preflood     Midseason                Yield
                     --------lb N per acre-------            bu/acre
       
    Jefferson            0                30+30                147
    Jefferson           30                30+30                159
    Jefferson           60                30+30                191
    Jefferson           90                30+30                180
    Jefferson          120                30+30                184
    Jefferson          150                30+30                185
    Jefferson          180                30+30                173
    Drew                 0                30+30                173
    Drew                30                30+30                210
    Drew                60                30+30                179
    Drew                90                30+30                165
    Drew               120                30+30                162
    Drew               150                30+30                200
    Drew               180                30+30                153
    Jefferson            0                    0                130
    Jefferson           30                    0                136
    Jefferson           60                    0                193
    Jefferson           90                    0                194
    Jefferson          120                    0                178
    Jefferson          150                    0                174
    Jefferson          180                    0                179
    Drew                 0                    0                164
    Drew                30                    0                182
    Drew                60                    0                197
    Drew                90                    0                175
    Drew               120                    0                156
    Drew               150                    0                166
    Drew               180                    0                136

Chlorophyll meter readings and plant area board measurements were made before applying midseason N.

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