Information from 2001 Missouri Rice Research Update, February 2002.

Boron Fertilization of Rice

David Dunn

Abstract

Boron fertilizer treatments were applied to a rice field that the soil tested low for boron. Soil and foliar applications were compared on Kaybonnett rice. Boron treatments increased rice yields, on average, 8 to 25 bushels per acre. The greatest rice yield was obtained with a 0.5 lb/a foliar application at first tiller growth stage.

Introduction

Boron is an essential plant nutrient. Its functions in rice plants are involved in cell growth and development of the flower. Boron is very water-soluble. As such it is mobile in soil-water solutions. Current University of Missouri soil test recommendations for rice call for a 0.5 lb/a boron application when less that .25 ppm of boron is found in the soil. Soil samples collected at the Missouri Rice Research Farm in 1998 were found to contain between .02 and .35 ppm boron.

Materials and Methods

Study 1
In this three year study, a location at the Missouri Rice Research Farm that tested low in soil boron (0.19 ppm average) was used to conduct this evaluation. Rice was drill seeded at a rate of 75 lb/a. Weeds were controlled with propanil applications, at 3 lb./acre when the grass had 2-3 leaves and then reapplied approximately 14 days later, shortly before flood establishment (Stam 3+3 program). No insect control was necessary. In this study four Boron application rates, .25, .50, .75, and 1.0 lb B/a, were compared to an untreated check. Two application methods, preplant soil applied and preflood (first tiller) foliar spray, were evaluated for each boron rate. Soil samples were collected prior to flooding from each plot receiving preplant boron. These soil samples were tested for plant available boron. Each plot was mechanically harvested and the yield recorded.

Study 2
In this study five pre-plant B rates were used create a range of soil test values for B. At pre-flood two rates of foliar B ( ½ and ¾ lb/a) were applied. Each plot was mechanically harvested and the yield recorded.

Study 3
In this study Boron was mixed with the rice herbicide Arrosolo. The 3 qt rate of Arrosolo was mixed with 0.25 or 0.50 lbs B/a in 20 gallons/a water. Applications were made when the barnyard grass reached 2-3 leaf stage and again immediately prior to flooding. This mixture was compared to a single application of Arrosolo (3qt) + Facet (8oz). The plots were rated for rice injury and barnyard grass control. Each plot was mechanically harvested and the yield recorded.

Results

Study 1
All boron applications increased rice yields over the untreated check (Table 1). In 1999, the foliar applications produced higher yields than soil applied boron. The average for all four boron treatments in an application type was also greater in the foliar in the first year of the project. In 2000, the soil application for the same rate of fertilizer was greater. The same is also true for the 2000 average for the four treatments. In 2001 the results were mixed. The three year average, however, showed the soil applications produced greater yields for the same boron application rate. The 0.5 lb B/a rate for foliar applications (162 bu/acre) showed the greatest increase compared to the untreated check (143 bu/acre). This represents an increase of 19 bu/a of grain.

Study 2
Soil applications of boron increased plant available soil test levels (Table 2). The magnitude of this increase was consistent with the application rate. Adding ½ or ¾ lbs.B/a did not increase rice grain yields when the Boron soil test was above 0.25 ppm B (Figure 1.).

Study 3
Additions of Boron to Arrosolo did not decrease the effectiveness of Arrosolo on barnyard grass control (Table 3). Rice injury was not increased by Boron addition to Arrosolo.

Table 1. Average rough rice yields for boron treatments in 1999 and 2000 for the rice variety Kaybonnett.

lb. B/a
Application type
Average rough rice yields (bu/a)
1999
2000
2001
Mean
0
146
144
140
143
0.25
Soil
150
165
151
155
0.5
Soil
151
189
139
160
0.75
Soil
150
173
148
157
1.0
Soil
147
185
147
160
Mean
Soil
150
178
146
158
0.25
Foliar
151
169
146
155
0.5
Foliar
160
180
145
162
0.75
Foliar
149
157
148
153
1.0
Foliar
151
154
155
151
Mean
Foliar
153
165
149
155

Table 2. Average soil test B levels for preplant soil applied treatments.

Soil Applied
Boron lbs./a
Soil test B in ppm
1999
2000
2001
Mean
0
0.17
0.21
0.19
0.19
0.25 Soil
0.24
0.30
0.26
0.27
0.5 Soil
0.43
0.33
0.36
0.37
0.75 Soil
0.37
0.42
0.45
0.41
1.0 Soil
0.49
0.54
0.56
0.53

Table 3. Effect of adding Boron to Arrosolo on barnyard grass control.

Treatment
% Barnyard
grass control
6-22-01
% Barnyard
grass control
7-03-01
6-7-01 6-22-01
Arrosolo (3qt)
Boron (0.5lb)
Arrosolo (3qt) 70.0 97.5
Arrosolo (3qt) Arrosolo (3qt) 77.5 95.0
Arrosolo (3qt)
Boron (0.25lb)
Arrosolo (3qt)
Boron (0.5lb)
70.0 100.0
Arrosolo (3qt) Arrosolo (3qt)
Boron (0.25lb)
72.5 97.5
Arrosolo (3qt)
Facet (0.5 lb)
  87.5 90.0
Untreated Check 0.0 0.0

Boron levels

Figure 1. Effect of adding 1/2; and 3/4; lbs. Boron at varying soil test B levels on rice grain yields.








Conclusions

Rice yields can be increased with boron applications. On the three year average, maximum yields were obtained when the University of Missouri recommended rate (0.5 lb B/a) of boron was applied as a foliar spray. In 1999 and 2001, the foliar application was better than the soil. While in 2000, soil applications were better than the foliar. But for the three year average, the foliar is on top. Producers should consider testing soils for Boron and applying boron when the soil test B levels are found to be less than 0.25 ppm.

Acknowledgement

We would like to thank the Missouri Rice Research and Merchandising Council for their generous and continuing support for this project.

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