Information from 2001 Missouri Rice Research Update, February 2002.

Effect of Zinc Seed Treatment on Early Growth of Water-seeded Rice

David Dunn


Two methods of supplying Zinc to rice seeds were compared relative to an untreated check.


Zinc (Zn) is an essential plant nutrient. Rice zinc deficiency occurs in Southeast Missouri. When present in drill-seeded, the deficiency is usually observed shortly after the permanent flood is established at the first tiller growth stage. Low levels of zinc in rice plants can cause loss of turgidity of the leaves, basal chlorosis of the leaves, delay of plant development, "bronzing" of leaves, and in some cases death of the rice seedlings. Zinc tissue concentrations generally range from 25 to 150 ppm, with deficiency symptoms appearing whenever the tissue concentrations are less than 20 ppm.

The current University of Missouri soil test recommendations call for 5 lbs. Zn/a when less than 1.0 ppm Zn is found in the soil. The effectiveness of zinc seed coatings in increasing plant tissue concentrations and grain yields in drill-seeded rice is well known. Little is know about the effectiveness of Zn seed coatings in water seeded rice production.

Materials and Methods

The rice variety Drew was used in this study. A 50 lbs. bag of rice seed was split into two 25 lbs. portions. One twenty five pound split was treated with 2 oz. Zinche ST(Drexel Chemical), the other was not.

To evaluate the effect of Zinche ST on seed viability and early plant growth, 50 treated and untreated seeds of each variety were placed in a petri dish and 8 ml of deionized water was added to each dish. This evaluation was conducted at room temperature. Each treatment was replicated four times. The germination of seeds was checked at 3, 6, and 8 days. A seed with a visible shoot or root was counted as germinated. At 10 days the emerged shoots of 10 randomly selected seeds were measured from each treatment.

To evaluate the effect of Zinche ST on the growth of water seeded rice treated and untreated seeds were cultivated in 5-gallon aquariums using masonry sand as the growing medium. Two inches of sand and two inches of water were placed in each aquarium. This evaluation was conducted in a green house with no supplemental lighting and an average temp of 82oF. The following three treatments were evaluated, untreated seed, treated seeds, and untreated seeds soaked in a 1:1,000 solution of Zinche ST in distilled water. These treatments were randomized and replicated four times. For the treated and untreated seeds 15 grams of each were selected. Of this 10 grams were wrapped in cheesecloth and soaked in 100 ml of distilled water or the 1:1,000 solution for 24 hours. The remaining 5 grams of seed was dried, ground, and analyzed for Zn content. At the end of 24 hours the seed packages were removed from the water and allowed to germinate for an additional 24 hours. Following the second 24 hours 5 grams of each seed package were placed into each aquarium. The remaining 5 grams of seed was dried, ground, and analyzed for Zn content. The growth of the seeds was measured at 7-day intervals. At 28 days after planting the rice plants were harvested, washed with deionized water, and dry mater mass determined. The plants were dried, ground and analyzed for Zn content.


Zinc treatment decreased the three and six day germination rates of the rice. At eight days the germination rate was the same for treated and non-treated seeds (Table 1). The average shoot length was reduced from 34 to 29 mm by Zn treatments.

Table 1. Average germination and shoot length for untreated and Zn-treated seeds.

None 79 99 100 34
Zn 65 96 100 29

Both Zinc treatments, seed and soak, were effective at increasing Zn concentrations in the seed (Table 2). The Zn levels were higher for the seed treated seeds (1180 ppm) than soak treated seeds(970 ppm).

Table 2. Zinc content of rice seeds used in greenhouse study.

TreatmentUntreated seedTreated seedPost soak seed
Non treated27 ppm -------- 29 ppm
Seed 27 ppm 1821 ppm 1180 ppm
Soak 27 ppm -------- 970 ppm

The number of rice plants that had grown above the water in one week after seeding was influenced by Zn treatments. Compared to the untreated check seed treatment reduced the number from 20 to 17, while soak treatment increased the number to 26. At two weeks the number of plants above the water was about the same for each treatment (Figure 1).

Above Water Plants
Figure 1. Number of rice plants above water for Zn treatments at one and two weeks after seeding.

The increased zinc levels found in treated seeds were reflected in increased plant tissue concentration of zinc. The untreated seed produced plants that contained 59 ppm Zn. Seed and soak treatments produced plants which contained 212 and 144 ppm Zn respectively (Table 3). Zinc treatments had no effect on dry matter accumulations.

Table 3. Effect of treatments on Zn tissue concentrations and dry matter accumulations.

TreatmentZn(ppm) Dry matter (gr.)
Non-treated 59 2.1
Seed 212 2.1
Soak 144 2.1


Rice seeds treated with zinc germinate slower than untreated seeds. This may be a problem in a water seeded rice production system. About 2/3 of the zinc applied to seed in seed traeting is retained in the seed following soaking. Using zinc treated seed in a water seeded rice production system is a way of insuring that the developing rice plant has sufficient Zn to develop properly.

Adding one gallon of Zinche ST per 1,000 gallons of soak water is also effective in supplying zinc to rice seedlings in a water-seeded production system.


I would like to thank Drexel Chemical Company of Memphis, TN and Carter-Cox Seeds, Inc. of Knobel, AR for supplying the Zinche ST and rice seed used in this evaluation.

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