Information from 1999 Missouri Rice Research Update, February 2000.

Zinc Fertilization and Rice Production

Michael Aide, Justin Horn, David Dunn, Gene Stevens

Abstract

In a two year experiment three rice varieties were cultivated in a randomized complete block with treatments consisting of lime, no lime, no Zn, soil applied Zn, and foliar applied Zn. Soil samples were collected before planting and after harvest. Tissue concentrations of selected elements were measured. Soil levels of Zn were high enough to maintain adequate levels of Zn in plant tissues even at soil pH levels above 7.0. Rice grain yields were not influence by lime or Zn treatments.

Introduction

Zinc (Zn) is an important micronutrient in the establishment and development of the rice plant. Zn deficiencies result in the inability of the rice plant to support root respiration during flooded conditions. Typical Zn rice tissue levels are between 25 and 100 ppm with deficiency symptoms appearing when levels fall below 20 ppm. Zinc is less available to rice plants at soil pH above 7.0. High levels of plant available manganese (Mn) have been found to limit a plant's ability to uptake Zn.

Materials and Methods

Three rice varieties, 'Cypress', 'Drew', and 'Kaybonnet' were grown at the Missouri Rice Research Farm located near Qulin, MO. The experimental design was a randomized complete block with three replications. Two lime treatments; O and 2 ton/a were evaluated as well as three zinc treatments: No zinc, 20 lb/a Zn soil applied preplant, and 5 lb Zn EDTA as a foliar application preflood. Soil samples were collected from each plot before planting and after harvest. These samples were analyzed for pH, P, K, Ca, Mg, Zn, Cu Mn, and Fe.

Tissue samples were collected at maximum tillering and panicle initiation. These samples were analyzed for Ca, S, Mg, Al, P, K, B, Zn, Mn, Cu, and Na. Field measurements include tiller counts, panicles per row, spikelets per panicle, seed weight, dry matter accumulation, and yield.

Results

Yields of Cypress', 'Kaybonnet', and 'Drew' were not affected by the zinc treatments. Liming increased the yields of 'Cypress' in 1998. Seeds per panicle showed a similar trend (Tables 1 a,b,c).

Table 1a. Average rice yields and seeds per panicle for 'Cypress' in 1998 and1999. Table 1b. Average rice yields and seeds per panicle for 'Kaybonnet' in 1998 and 1999. Table 1c. Average rice yields and seeds per panicle for 'Drew' in 1998 and 1999.
Treatment Seed/
panicle
Yield
Cypress 1998 1999 1998 1999
No lime
No Zn
104 92 104 151
Lime
No Zn
145 81 112 139
No lime
Soil Zn
109 89 107 133
Lime
Soil Zn
95 101 121 146
No lime
Foliar Zn
123 95 105 142
Lime
Foliar Zn
147 93 110 145
Treatment Seed/
panicle
Yield
Kaybonnet 1998 1999 1998 1999
No lime
No Zn
127 128 150 146
Lime
No Zn
130 117 134 152
No lime
Soil Zn
116 128 134 146
Lime
Soil Zn
125 136 137 130
No lime
Foliar Zn
132 140 149 153
Lime
Foliar Zn
115 125 130 138
Treatment Seed/
panicle
Yield
Drew 1998 1999 1998 1999
No lime
No Zn
141 109 135 153
Lime
No Zn
143 104 140 142
No lime
Soil Zn
152 87 146 139
Lime
Soil Zn
112 105 131 138
No lime
Foliar Zn
136 85 138 151
Lime
Foliar Zn
153 116 141 146

The lime treatments consistently increased the soil pH, mostly from pH 6.3 to pH 7.2. Soil zinc levels were dramatically increased by soil zinc applications. Liming generally reduced the plant availability of zinc and manganese; however, this reduced availability was still sufficient to support rice growth (Table 2).

Table 2. Average soil test values for samples collected post harvest 1999.

Treatment pH Zn ppm Mn ppm
No lime
No Zn
6.3 1.21 42
Lime
No Zn
7.0 1.35 30
No lime
Soil Zn
6.8 8.91 32
Lime
Soil Zn
7.2 3.25 30
No lime
Foliar Zn
6.4 3.01 37
Lime
Foliar Zn
7.2 2.05 30

The rice varieties 'Cypress', 'Kaybonnet', and 'Drew' each showed zinc plant tissue levels above the deficiency level (approximately 20 ppm Zn), indicating that the soil was supplying sufficient zinc to support rice. The plant tissue levels of Ca, Mg, S, P, K, Na, Fe, Al, Cu, and B were normal. The plant tissue levels for manganese were excessive (Tables 3 a,b,c).

Table 3a. Average plant tissue levels for Zn and Mn for the rice variety 'Cypress' 1998 and 1999. Table 3b. Average plant tissue levels for Zn and Mn for the rice variety 'Kaybonnet' 1998 and 1999. Table 3c. Average plant tissue levels for Zn and Mn for the rice variety 'Drew' 1998 and 1999.
Treatment Zn ppm Mn ppm
Cypress 1998 1999 1998 1999
No lime
No Zn
44 54 1266 1104
Lime
No Zn
21 55 1247 1269
No lime
Soil Zn
34 49 1240 1107
Lime
Soil Zn
36 58 1105 1242
No lime
Foliar Zn
24 58 1341 1261
Lime
Foliar Zn
27 46 1289 1182
Treatment Zn ppm Mn ppm
Kaybonnet 1998 1999 1998 1999
No lime
No Zn
36 48 1772 1167
Lime
No Zn
31 46 1827 977
No lime
Soil Zn
28 65 1698 1231
Lime
Soil Zn
36 61 1569 1250
No lime
Foliar Zn
30 41 1629 1132
Lime
Foliar Zn
32 53 1178 1181
Treatment Zn ppm Mn ppm
Drew 1998 1999 1998 1999
No lime
No Zn
37 44 1392 1126
Lime
No Zn
30 52 1571 1468
No lime
Soil Zn
48 63 1758 1384
Lime
Soil Zn
25 66 1199 1269
No lime
Foliar Zn
33 53 1343 1374
Lime
Foliar Zn
41 54 1371 1131

Conclusion

Zinc fertilization did not influence the growth, development or yield of rice. Liming the soil to pH 7.0 or higher did not significantly reduce the plant uptake of zinc. We attribute this lack of response to high levels of zinc contained in soil concretions (buckshot). High levels of soil Zn did not result in a greater plant uptake of Zn. High tissue levels of Mn may have limited uptake of Zn. These high levels of Mn did not induce a Zn deficiency.

Acknowledgement

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

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