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
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.
Table 1. Average germination and shoot length for untreated and Zn-treated seeds.
| Treatment | 3-day
% | 6-day
% | 8-day
% | Shoot length |
| 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.
| Treatment | Untreated seed | Treated seed | Post soak seed |
| Non treated | 27 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).
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.
| Treatment | Zn(ppm) | Dry matter (gr.) |
| Non-treated | 59 | 2.1 |
| Seed | 212 | 2.1 |
| Soak | 144 | 2.1 |
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.
Missouri Rice Research Reports