Information from 2000 Missouri Rice Research Update, February 2001.

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

Gene Stevens, David Dunn, Keith Birmingham, Chris Moylan, and Alan Sheckell

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

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
Cocodrie and Drew rice were drill seeded on May 8, 2000. Due to problems during planting, Drew had to be abandoned from the test. Cocodrie was 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 mid-season N to help determine the effects that the mid-season application would have on the rice.

Yield results from the experiment showed that in Cocodrie the highest yields occurred with 120 to 150 total lb N/acre. A preflood application of N along with a mid-season application resulted in an average of 15 bu/acre increase in yield over preflood application only (Table 1).

In 1999, Drew yields were higher in the plots where the mid-season application was included, averaging 9 more bu/acre than those with only a single application.

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.

This experiment funded by the Missouri Rice Research and Merchandising Council.

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

Variety         Preflood         Midseason         Yield bu/acre
                ------lb N per acre-------                       
Cocodrie             0             30+30                103
Cocodrie            30             30+30                 84
Cocodrie            60             30+30                161
Cocodrie            90             30+30                160
Cocodrie           120             30+30                142
Cocodrie           150             30+30                161
Cocodrie           180             30+30                155
Cocodrie             0               0                  109
Cocodrie            30               0                  118
Cocodrie            60               0                  114
Cocodrie            90               0                  109
Cocodrie           120               0                  146
Cocodrie           150               0                  146
Cocodrie           180               0                  163      
Chlorophyll meter readings were made before applying midseason N.

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