Evaluation of Zinc Seed Treatments for Rice

Transcription

1 Evaluation of Zinc Seed Treatments for Rice Nathan A. Slaton,* Charles E. Wilson Jr., Sixte Ntamatungiro, Richard J. Norman, and Danny L. Boothe ABSTRACT gence (Martens and Westermann, 1991). These studies Zinc seed treatments for rice (Oryza sativa L.) were previously have not investigated a complete range of Zn seed treatevaluated as an alternative to soil-applied Zn. Recommendations concerning ment rates and sources to compare with standard soil the effectiveness of Zn seed treatments were never clearly or foliar Zn fertilization methods. stated. Our objectives were to evaluate the utility of Zn seed treat- Martens et al. (1973) concluded that band application ments for supplying Zn to rice grown on soils prone to Zn deficiency. of Zn fertilizer in contact with the corn (Zea mays L.) In 1998, a study with three cultivars compared Zn-treated seeds [2.8 g seeds at rates ranging from 0.34 to 1.34 kg Zn ha 1 Zn (kg seed) 1 ] with a control and 11 kg Zn ha 1 as ZnSO 4 applied produced grain yields equal to those achieved when 26.9 to the soil. Because tissue Zn concentration did not differ among kg Zn ha 1 as ZnSO 4 was broadcast on the soil surface cultivars, a single cultivar, Drew, was used in studies at two locations in The control and the soil-applied Zn were compared with and incorporated before planting. Earlier research with seeds that were treated with three rates of ZnSO 4 and ZnEDTA rice (Haghighat and Thompson, 1982; Giordano and (ethylenediaminetetraacetic acid). Analysis showed net seed concensuggested that the application of low rates of Zn to rice Mortvedt, 1973; Mengel et al., 1976; Rush, 1972) also trations of 1.0, 2.2, and 4.7 g Zn (kg seed) 1 as ZnSO 4 and 1.4, 2.8, and 5.7 g Zn (kg seed) 1 as ZnEDTA. In 1998, neither visual Zn seeds or dipping the roots of transplanted rice in a Zn deficiency symptoms nor significant yield differences were observed solution may be effective alternatives to broadcast appliamong treatments. Soil-applied Zn and Zn seed treatments increased cations of Zn fertilizer. tissue Zn concentration by 11.9 and 4.7 mg Zn kg 1, respectively, In Arkansas, Zn fertilizer recommendations for rice above that of the control (19.7 mg Zn kg 1 ). In 1999, Zn deficiency are currently based on the soil ph and texture. Zinc is occurred at both locations. Measurements of dry matter, tissue Zn recommended for rice, regardless of soil test Zn levels, concentration, and grain yield showed that Zn-treated seed performed equal to or better than soil-applied Zn. These data suggest that seed Zn grown on silt and sandy loam soils having a ph 6.5. concentrations between 2.2 to 5.7 g Zn (kg seed) Sedberry et al. (1980) and Wells (1980) both found the are an economical alternative to soil-applied Zn. soil ph to best predict rice response to Zn fertilization during the early 1970s. However, much of this research was conducted before the widespread use of Zn fertilizers. Zinc seed treatments were evaluated in rice as an Since the development of Zn fertilizer recommendations, alternative to soil- or foliar-applied Zn by several the low native soil Zn concentrations have increased apresearchers in the early 1970s with limited success preciably due to repeated broadcast applications of inor- (Haghighat and Thompson, 1982; Giordano and Mortfrequency of both Zn deficiency symptoms and docu- ganic Zn sources to each rice crop. Subsequently, the vedt, 1973; Mengel et al., 1976; Rush, 1972). Due to the limited amount of research, Zn seed treatments for mented rice yield responses to Zn fertilization has de- rice and recommendations concerning their effective- clined (Slaton et al., 1995; Thompson and Kasireddy, ness were never clearly stated. Despite the lack of formal 1975). Until a critical soil test Zn level for Zn fertilizer recommendations, Zn-treated seed rice is available recommendations is established, alternative methods of throughout the southern USA rice-growing area. Literaing investigated. supplying Zn to the rice crop on high-ph soils are be- ture concerning the efficacy of micronutrient fertilizer applications to crop seeds is limited. Rasmussen and Because the application of small amounts of Zn to Boawn (1969) determined that Zn seed treatment alone rice seeds would be more economical and convenient was not effective in preventing Zn deficiency of kidney than either soil or foliar applications, our objectives beans (Phaseolus vulgaris L.). Yilmaz et al. (1997) also were to evaluate the effect of Zn seed treatments on concluded that soil-applied Zn was a superior fertilizagrain yield of rice in comparison with the standard rec- the dry matter production, tissue Zn concentration, and tion method compared with Zn-treated wheat (Triticum aestivum L.) seed or foliar Zn applications. Other studobjective of our studies was to determine the effect of ommendation of broadcast soil applied Zn. A secondary ies have found that the application of Zn to seeds has either failed to prevent Zn deficiency or reduced emerthe radicle and Zn seed treatment on germination and the lengths of coleoptile. N.A. Slaton, S. Ntamatungiro, and D.L. Boothe, P.O. Box 351, Univ. of Arkansas Rice Res. and Ext. Cent., Stuttgart, AR 72160; C.E. Wilson Jr., P.O. Box 3508, Univ. of Arkansas Southeast Res. and Ext. Cent., Monticello, AR 71656; and R.J. Norman, Dep. of Crop, Soil, and Environ. Sci., Univ. of Arkansas, Plant Sci. 115, Fayetteville, AR Published with the approval of the director of the Arkansas Agric. Exp. Stn., Manuscript # Research was partially funded by rice grower check-off contributions administered by the Arkansas Rice Research and Promotion Board. Received 17 Feb *Corresponding author (Nslaton@uaex.edu). Published in Agron. J. 93: (2001). 152 MATERIALS AND METHODS A preliminary field study was conducted at the Rice Research and Extension Center (RREC) near Stuttgart, AR (34.30 N lat) during 1998 on a DeWitt silt loam (fine, smectitic, thermic, Typic Albaqualfs) that had received 4480 kg ha 1 lime (CaCO 3 ) in Rice grown in this field in 1997 exhibited Abbreviations: ICAP, inductively coupled Ar plasma spectrophotom- etry; PPI, preplant incorporated; PTBS, Pine Tree Branch Station; RREC, Rice Research and Extension Center; TDM, total dry matter.

2 SLATON ET AL.: EVALUATION OF ZINC SEED TREATMENTS FOR RICE 153 Zn deficiency symptoms after flood application. Soil samples Table 1. Selected soil chemical properties from 1998 and 1999 collected before seeding were analyzed for extractable cations Zn fertility studies. (including Zn 2 ) by Mehlich 3 extraction (Mehlich, 1984). Soil ph was determined in a 1:2 soil water suspension with a glass Factor RREC RREC PTBS electrode. Selected soil chemical properties are listed in Table 1. Soil ph Seeds of the rice cultivars Cypress, Drew, and Jefferson P, mg kg K, mg kg that were treated with either Vitavax (Carboxin) (5,6-dihy- Ca,mgkg dro-2 methyl-n-phenyl-1,4-oxathiin-3-carboxamide) or Vita- Mg,mgkg vax plus Zn (Zn Starter, Agtrol Chem., Houston, TX) (J. Zn,mgkg Garrett, personal communication, 1998) were obtained from Values are the average of four composite samples taken from control Garrett Seed Farms (Danbury, TX). An elemental analysis plots in each replication. Mehlich 3 soil extractant used for elements. of the Zn-treated seeds indicated a net concentration of 2.8 g RREC, Rice Research and Extension Center, near Stuttgart, AR. Zn (kg seed) 1 (0.34 kg Zn ha 1 ). Zinc-treated seeds were PTBS, Pine Tree Branch Station, Colt, AR. Soil weight/water volume ratio was 1:2. compared with seeds that received no Zn seed treatment but were fertilized with either 0 or 11 kg Zn ha 1 (ZnSO 4-31% Zn, Tetra Micronutrients 1, The Woodlands, TX) applied to ples were immediately washed in deionized water, 0.1 M HCl, the soil and preplant incorporated (PPI). Rice was seeded on and rinsed in deionized water before drying to remove possible 23 June at a rate of 120 kg ha 1 in plots consisting of nine sources of contamination (Wells, 1980). The samples were rows that were 4.88 m long and spaced 17.8 cm apart. dried at 60 C to a constant weight, weighed, and ground in a In 1999, studies were conducted at the RREC on a DeWitt Wiley mill to pass a 2-mm sieve. The ground tissue (0.5-g silt loam and at the Pine Tree Branch Station (PTBS) near subsample) was digested with concentrated HNO 3 and 30% Colt, AR (35.08 N lat) on a Calloway silt loam (fine-silty, H 2 O 2 (wt./wt.) for determination of the whole plant elemental mixed, thermic, Glossaquic Fragiudalfs). Selected soil chemiof the plant digests was performed by ICAP (Soltanpour et composition (Jones and Case, 1990). An elemental analysis cal properties are listed in Table 1. Because 1998 experiments failed to show Zn deficiency symptoms, 2240 kg ha 1 lime was al., 1996). At maturity, 2.6 m 2 from the center four rows of applied at the RREC. Soil Ca and Mg levels were higher at each plot was harvested for grain yield with a small plot com- the PTBS location, so lime was not applied. Split applications bine. The reported grain yields were adjusted to 120 g kg 1 of 68 kg P ha 1 were made at both locations before seeding of moisture. and again before establishment of the permanent flood to The treatments were arranged as a randomized complete enhance the likelihood of Zn deficiency. Potassium fertilizer block, 3 (cultivar) 3 (Zn fertilizer treatments) factorial de- was broadcast across all treatments as needed according to sign with four replications in During 1999, each location soil analysis. was arranged in a randomized complete block with four repli- The cultivar Drew was seeded at the RREC and PTBS on cations. A split-plot analysis was used where location was the 20 May and 22 April, respectively. Rice was seeded at a rate whole-plot factor and Zn fertilizer treatment was the subplot of 120 kg ha 1 in plots consisting of nine rows that were 4.88 m factor. All data were analyzed using the PROC GLM proce- long and spaced 17.8 cm apart. The treatments included an dure of SAS. Differences among treatments were identified untreated control, 11 kg Zn ha 1 PPI (as previously described), using Fisher s protected LSD test at the 0.05 or 0.10 signifi- and six treatments with different amounts of Zn applied to cance level. seeds. Zinc was applied to seeds at three rates using either a ZnSO 4 solution or liquid 9% ZnEDTA chelate (wt./wt.). The Seed Viability ZnSO 4 solutions were prepared by dissolving 100, 200, or 400 g To evaluate the effect of Zn seed treatment on seed viabilof reagent grade ZnSO 4 7H 2 Oin1LofH 2 O. The seeds were ity, treated and untreated seeds from 1999 field studies were then treated by mixing g of seeds with 7.5 ml of the placed in a germinating chamber at 20 C, approximately 8 mo ZnSO 4 solution. For the EDTA treatment, g of seeds after treatment. Seeds were stored in paper envelopes at room was mixed with a total volume of 100 ml of EDTA solution temperature during this period. Fifty seeds from each treatof which 25, 50, or 100 ml was 9% ZnEDTA (wt./wt.). ment were placed in a petri dish, and 3 ml of deionized water To determine the amount of Zn coated on the seeds, treated was added to each dish. Each treatment was replicated three and untreated seeds were digested with HNO 3 and 30% H 2 O 2 times. The germination of seeds was checked at 6, 8, and 10 d. (wt./wt.) (Jones and Case, 1990) and analyzed by inductively A seed with a visible radicle or coleoptile was counted as coupled Ar plasma spectrophotometry (ICAP) (Soltanpour germinated. Germination data are reported as the percent of et al., 1996). Seed analysis showed a net Zn coating content seeds germinated. At the 10-d measurement, the emerged of 1.0 (0.12 kg Zn ha 1 ), 2.2 (0.26 kg Zn ha 1 ), and 4.7 g Zn radicle and coleoptile of 10 randomly selected germinated (kg seed) 1 (0.56 kg Zn ha 1 ) as ZnSO 4 and 1.4 (0.17 kg Zn seeds were measured from each treatment replicate. ha 1 ), 2.8 (0.34 kg Zn ha 1 ), and 5.7 g Zn (kg seed) 1 (0.68 The treatments were arranged as a randomized complete kg Zn ha 1 ) as ZnEDTA. Therefore, approximately one-half block design with three replications. All data were analyzed of the added Zn was retained on the seeds. using the PROC GLM procedure of SAS. Differences among For all studies, 150 kg N ha 1 was applied as urea treatments were identified using Fisher s protected LSD test [(NH 2 ) 2 CO] to the dry soil surface immediately before flooding at the 0.05 significance level. at the 4-leaf growth stage. Plant samples were collected 14 d after flooding by removal of the aboveground plant tissue in a 0.9-m row section of the second inside row. The tissue sam- RESULTS AND DISCUSSION 1998 Experiment 1 Mention of trade names and commercial products in this article is solely for the purpose of providing specific information, does not The total dry matter (TDM) production, harvest grain constitute a guarantee or warranty, and does not signify that these moisture, and grain yield of rice were not significantly products are approved to the exclusion of comparable products. affected by Zn fertilizer treatment or the cultivar Zn

3 154 AGRONOMY JOURNAL, VOL. 93, JANUARY FEBRUARY 2001 Table 2. Effect of rice cultivar on grain yield, total dry matter (TDM), and harvest moisture averaged across Zn treatments during 1998 at the Rice Research and Extension Center (RREC), near Stuttgart. Cultivar Grain yield TDM Grain moisture Table 4. Effect of Zn seed treatment source and rate on rice total dry matter (TDM) by 14 d after flooding compared with an untreated and standard check at two locations in TDM Zn fertilizer treatment PTBS RREC kg ha 1 gkg 1 kg ha Drew Cypress Control Jefferson kg Zn ha 1 PPI LSD(0.05) 353*** 95* 21* 1.0 g Zn-ZnSO 4 (kg seed) 1 # g Zn-ZnSO 4 (kg seed) * Significant at the 0.05 level. 4.7 g Zn-ZNSO 4 (kg seed) *** Significant at the level. 1.4 g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) fertilizer treatment interaction but were significantly LSD(0.10) within location 136 different among cultivars (Table 2). The lack of differences among the Zn fertilizer treatments suggested that P-value for Zn fertilizer treatment location LSD(0.10) between locations rice was not Zn deficient and would not show a significant yield and growth response to Zn fertilization. Although not statistically significant at the 0.05 level of probability (P 0.16), the grain yield for both 11 kg Zn ha 1 PPI and 2.8 g Zn (kg seed) 1 was 214 and 360 kg ha 1 greater than the control, respectively, when averaged across the cultivars (Table 3). The tissue Zn concentration of whole-plant seedlings 14 d after flooding did show significant differences between Zn fertilizer treatments (Table 3). The tissue Zn concentration followed the highest-to-lowest order of 11 kg Zn ha 1 PPI 2.8 g Zn (kg seed) 1 control. Rasmussen and Boawn (1969) suggested that Zn seed treatment of kidney bean was not an adequate alternative to broadcast Zn fertilizer applications to the soil because Zn deficiency symptoms occurred, and Zn seed treatment failed to produce yields equal to soil Zn appli- cation. Based on the 1998 tissue concentration data, 11 kg Zn ha 1 PPI was superior to 2.8 g Zn (kg seed) 1 for supplying Zn to seedling rice plants. However, both treatments increased tissue Zn in rice seedlings above the level considered deficient (20 mg kg 1 ) while the control was near the critical threshold (Sedberry et al., 1987). Although Zn tissue concentration data were a useful means of evaluation, the effectiveness of Zn seed treatments can best be made under Zn deficient conditions. PTBS, Pine Tree Branch Station, Colt, AR. RREC, Rice Research and Extension Center, near Stuttgart, AR. Standard check. PPI, preplant incorporated. # Seeding rate for all treatments was 120 kg ha 1 seed. plots while few or no symptoms were observed in the 4.7 g Zn (kg seed) 1 as ZnSO 4 and 5.7 g Zn (kg seed) 1 as ZnEDTA plots. The deficiency symptoms were most severe at the RREC. Thus, the response of the rice TDM among Zn treatments differed between locations for some treatments (Table 4). The rice TDM response at each location was indicative of the degree of Zn deficiency symptoms expressed among Zn treatments at each location. At the PTBS, seeds that were treated with Zn pro- duced significantly greater TDM by 14 d after flooding than both the control and 11 kg Zn ha 1 PPI, regardless of the Zn source or rate. It is unclear why Zn deficiency symptoms occurred in the 11 kg Zn ha 1 PPI treatment. The random occurrence of deficiency symptoms within each 11 kg Zn ha 1 PPI plot suggests that uniform fertil- izer distribution at the applied rate could not supply the plants that were physically located between fertilizer granules with adequate Zn nutrition. Both the control and 11 kg Zn ha 1 PPI treatments recovered from the early Zn deficiency symptoms within 14 d after plant samples were taken. Within the Zn seed treatments, the TDM tended to increase as the Zn application rate in Experiments creased. At the RREC, the TDM for 11 kg Zn ha 1 PPI was Zinc deficiency symptoms similar to those described by Sedberry et al. (1978) were observed at both locations in The symptoms were most severe in the control significantly greater than the control, 1.0 g Zn (kg seed) 1 as ZnSO 4, and 1.4 g Zn (kg seed) 1 as ZnEDTA treatments and equal to all other treatments. Stand loss occurred in two of four replications of the control plots at the RREC and resulted in a significantly lower TDM than the control at the PTBS. The only other treatments that showed significant differences between locations were the 11 kg Zn ha 1 PPI and 1.4 g Zn (kg seed) 1 as ZnEDTA treatments. It is unclear why the 11 kg Zn kg ha 1 mg kg 1 ha 1 PPI treatment responded differently between the two locations. The 1.4 g Zn (kg seed) 1 as ZnEDTA Table 3. Effect of Zn fertilizer treatment, averaged across cultivars, on grain yield and tissue Zn concentration of seedling rice 14 d after flooding during 1998 at the Rice Research and Extension Center (RREC), near Stuttgart. Tissue Zn Zn fertilizer treatment Grain yield concentration Control kg Zn ha 1 PPI g Zn (kg seed) and 1.0 g Zn (kg seed) 1 as ZnSO 4 treatments apparently LSD(0.05) NS 2.6*** contained insufficient Zn to maximize plant growth at *** Significant at the probability level. the RREC. Based on the TDM data from both locations, PPI, preplant incorporated. Seeding rate for all treatments was 120 kg ha 1 seed. Zn seed treatments should be applied at rates between NS, not significant at the 0.05 level of probability. P and 5.8 g Zn (kg seed) 1 for optimum growth under

4 SLATON ET AL.: EVALUATION OF ZINC SEED TREATMENTS FOR RICE 155 Table 5. Effect of Zn seed treatment source and rate on rice Table 6. Effect of Zn seed treatment source and rate on rice grain tissue Zn concentration by 14 d after flooding compared with yield and harvest grain moisture compared with an untreated an untreated and standard check at two locations in and standard check in 1999 (data averaged across two lo- Tissue Zn concentration cations). Treatment PTBS RREC Zinc treatment Grain yield Grain moisture kg ha 1 gkg mg kg 1 Control Control kg Zn ha 1 PPI kg Zn ha 1 PPI g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) LSD(0.05) 726*** 16*** LSD(0.05) within location 2.8*** LSD(0.05) between locations 4.0*** *** Significant at the probability levels. Standard check. PPI, preplant incorporated. *** Significant at the probability level. Seeding rate for all treatments was 120 kg ha 1 seed. PTBS, Pine Tree Branch Station, Colt, AR. RREC, Rice Research and Extension Center, near Stuttgart, AR. Standard check. PPI, preplant incorporated. treatments to supply the Zn that is required for normal Seeding rate for all treatments was 120 kg ha 1 seed. plant growth, development, and grain production. Rush (1972) found significant increases in rice grain Zn deficient conditions, with the higher rate being preferred. yield from Zn seed treatments but also observed that some Zn products and application rates were toxic and The tissue Zn concentration also showed a significant reduced stand density. Rasmussen and Boawn (1969) Zn fertilizer treatment location interaction (Table 5). also noted a delay in the germination and emergence The general response of the tissue Zn concentration of kidney bean as well as reduced seedling vigor for among Zn fertilizer treatments was similar to that found from some Zn seed treatments. Plant population measurements for the TDM. Comparison of data in Tables 4 and 5 were not made in our field studies, but no reveals that the treatments at each location with the visual differences were noticed among the treatments. lowest tissue Zn concentrations also tended to produce However, germination data from seeds used in these the lowest TDM. The fact that Zn seed treatments in- tests did suggest that Zn seed treatments could influence creased the TDM and tended to increase the tissue Zn stand establishment (Table 7). Although the seed germi- concentrations, and thus the total Zn uptake, suggests nation among treatments by 6 d was not significant, the that Zn-treated seeds are capable of supplying sufficient general order of germination established by 8dwas Zn to maximize plant growth under conditions of Zn evident. By 8 d, the germination of untreated seeds deficient soil. The total Zn uptake by rice at maturity was significantly lower than all of the Zn-coated seed is approximately 0.5 kg ha 1, and crop removal accounts treatments. By 10 d, the germination of untreated seeds for about one-half of the total Zn uptake (unpublished and the 5.7 g Zn (kg seed) 1 as ZnEDTA treatment data, 1997). The application of Zn rates that are equal was lower than all other treatments, which were not to the total crop uptake should be adequate to supply different. The decrease in the germination of seeds the crop nutritional requirements if the uptake of fertil- treated with ZnEDTA was likely due to fungal growth. izer Zn is highly efficient. Broadcast fertilizer applications Fungal growth completely covered some ZnEDTA- made to the soil are about 20 times the total Zn treated seeds by 10 d, and thus hid the radicle or coleop- requirement of rice. tile from view. The trend for the percent germination The grain yield was significantly affected only by Zn to decline as the ZnEDTA rate increased was representative fertilizer treatment, and thus was averaged between locations of the increased fungal growth. Despite the good (Table 6). All of the treatments with Zn-treated initial germination of seeds treated with ZnEDTA, the seeds or 11 kg Zn ha 1 PPI produced significantly higher potential may exist for this product to reduce seedling yields than the control. All of the Zn seed treatments vigor, so it should be further evaluated before being produced yields that were similar to the standard recommendation used as a Zn seed treatment. of 11 kg Zn ha 1 PPI. The control also had Radicle and coleoptile measurements were made only the highest grain moisture at harvest, indicating that on germinated seed at 10 d (Table 7). The radicle length the application of Zn enhanced maturation, and thus of untreated seeds was greater than that of all of the normal crop growth and development (Table 6). Grain treatments, except the 1.0 g Zn (kg seed) 1 as ZnSO 4. harvest moisture is not a parameter that is commonly The radicle length tended to decrease as the Zn rate reported to evaluate fertility treatments, except when increased, suggesting that Zn may inhibit radicle elonga- the degree of maturation is important. When the Zn tion. The coleoptile length was different only for seeds deficiency of flood-irrigated rice is uncorrected, as in that were treated with ZnEDTA. Seeds that were the control of these studies, stand loss may occur, plant treated with ZnSO 4, regardless of the rate, and untreated maturity may be delayed, or both. This can result in seeds had significantly longer coleoptiles than additional production costs and reduced milling (qual- seeds that were treated with all rates of ZnEDTA. The ity) and grain yields. Thus, harvest moisture provides coleoptile length of seeds treated with ZnEDTA also valuable information concerning the effectiveness of tended to decline as the rate increased.

5 156 AGRONOMY JOURNAL, VOL. 93, JANUARY FEBRUARY 2001 Table 7. Effect of Zn seed treatment on rice seed germination, radicle length, and coleoptile length approximately 8 mo after zinc application. 6-d 8-d 10-d 10-d 10-d Zn source germination germination germination radicle length shoot length % mm Control g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-ZnSO 4 (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) g Zn-EDTA (kg seed) LSD(0.05) NS 13.6** 17.4** 6.0* 3.1*** * Significant at the 0.05 level. ** Significant at the 0.01 level. *** Significant at the level. More germination and seedling vigor tests are needed ble interactions with other seed treatment chemicals, to evaluate the effect of the Zn application rate, Zn and the detrimental effects that have been observed source, temperature, and storage time on seed vigor and with Zn seed treatments for the vast number of Zn viability. These preliminary data from the germination products that are available. The potential use of Zn chamber illustrate the importance of thorough testing seed treatments for other Zn sensitive crops should also of new recommendations, especially when stand failure be investigated. is a potential risk. Although stand establishment problems were not observed in the 1999 field studies with any REFERENCES Zn seed treatment, environmental conditions in future Giordano, P.M., and J.J. Mordvedt Zinc sources and methods years could favor the development of seedling diseases of application for rice. Agron. J. 65: and stand loss. Growers and seed dealers are encourwith rice. p In Proc. Rice Tech. Working Group, 19th, Univ. Haghighat, N.G., and L.F. Thompson Zinc seed coating studies aged to use Zn seed treatments, but they should use only products that have been tested and deemed safe of Arkansas, Hot Springs, AR Feb Texas Agric. Exp. Stn., Texas A&M Univ., College Station, TX and effective. Jones, J.B., and V.W. Case Sampling, handling, and analyzing plant tissue samples. p In R.L. Westerman (ed.) Soil testing and plant analysis. 3rd ed. SSSA Book Ser. 3. SSSA, Madi- SUMMARY son, WI. Martens, D.C., G.W. Hawkins, and G.D. McCart Field response Rice response to Zn fertilization by soil or seed treat- of corn to ZnSO 4 and Zn-EDTA placed with the seed. Agron. ment was limited in the 1998 study due to a lack of Zn J. 65: deficiency. Despite the lack of yield response, the 1998 Martens, D.C., and D.T. Westermann Fertilizer applications for results showed that Zn seed treatments increased the correcting micronutrient deficiencies. p In J.J. Mortvedt (ed.) Micronutrients in agriculture. 2nd ed. SSSA Book Ser. 4. Zn concentration of rice seedlings and may hold promise SSSA, Madison, WI. as an economical alternative to more expensive broad- Mehlich, A Mehlich 3 soil test extractant: A modification of cast Zn fertilizer applications. Grain yield, tissue Zn Mehlich 2 extractant. Commun. Soil Sci. Plant Anal. 15: concentration, and TDM data generated at two locazinc oxide seed treatment on stand establishment, leaf zinc concen- Mengel, D.B., W.J. Leonards, and J.E. Sedberry Jr Effect of tions in 1999 support the use of Zn-treated seeds as a trations, and yield of Saturn rice. p In 68th Annu. Prog. safe, effective means of fertilizing rice grown on Zn Rep. Rice Exp. Stn. Crowley, LA. Louisiana State Univ. Agric. deficient soils. The grain yield was significantly im- Exp. Stn., Baton Rouge. proved by the use of Zn seed treatment compared with Rasmussen, P.E., and L.C. Boawn Zinc seed treatment as a the control and was equal to the yield from the standard source of zinc for beans. Agron. J. 61: Rush, M.C Effects of seed treatment with four zinc sources on recommendation of 11 kg Zn ha 1 PPI. stand and yield of Saturn rice. p In 64th Annu. Prog. Seeds that were treated with ZnSO 4 had a higher Rep. Rice Exp. Stn. Crowley, LA. Louisiana State Univ. Agric. germination rate than untreated seeds after an 8-mo Exp. Stn., Baton Rouge. storage period. Seeds that were treated with ZnEDTA Sedberry, J.E. Jr., M.C. Amacher, D.P. Bligh, and O.D. Curtis Plant-tissue analysis as a diagnostic aid in crop production. Louisialso tended to germinate better than the untreated ana Agric. Exp. Stn. Bull Louisiana State Univ., Baton Rouge. seeds, but ZnEDTA encouraged fungal growth and re- Sedberry, J.E. Jr., F.J. Peterson, F.E. Wilson, D.B. Mengel, P.E. Schilduced the coleoptile length, thereby reducing vigor as ling, and R.H. Brupbacher Influence of soil reaction and the study progressed. Despite excellent results from applications of zinc on yields and zinc contents of rice plants. field studies for TDM and grain yield, the ZnETDA Commun. Soil Sci. Plant Anal. 11: Sedberry, J.E. Jr., P.G. Schilling, F.E. Wilson, and F.J. Peterson sources should be avoided due to the potential risks of Diagnosis and correction of zinc problems in rice production. Louistand failure. The application of relatively low rates of siana Agric. Exp. Stn. Bull Louisiana State Univ, Baton Zn to rice seeds has potential for substantial cost savings Rouge. to producers when compared with conventional broad- Slaton, N.A., C.E. Wilson Jr., B.R. Wells, R.J. Norman, and R.S. Helms Evaluation of zinc deficiency of rice produced on cast soil or foliar Zn fertilization methods. Additional alkaline soils. p In W.E. Sabbe (ed.) Arkansas soil fertility research studies are needed to develop recommenda- studies Arkansas Agric. Exp. Stn. Res. Ser Fayetteville, tions for the best application rate and Zn source, possi- AR.

6 HOWARD ET AL.: N FERTILIZATION OF NO-TILL COTTON 157 Soltanpour, P.N., G.W. Johnson, S.M. Workman, J. B. Jones Jr., and Wells, B.R Zinc nutrition of rice growing on Arkansas soils. R.O. Miller Inductively coupled plasma emission spectrome- Ark. Agric. Exp. Stn Bull Univ. of Arkansas, Fayetteville, AR. try and inductively coupled plasma-mass-spectroscopy. p Yilmaz, A., H. Ekiz, B. Torun, I. Gultekin, S. Karanlik, S.A. Bagci, In D.L. Sparks (ed.) Methods of soil analysis: III. SSSA Book Ser. and I. Cakmak Effect of different zinc application methods 5. SSSA, Madison, WI. on grain yield and zinc concentration in wheat cultivars grown on Thompson, L.F., and N.R. Kasireddy Zinc fertilization of rice zinc-deficient calcareous soils. J. Plant Nutr. 20: by seed coating. Rice J. 78: Nitrogen Fertilization of No-Till Cotton on Loess-Derived Soils Donald D. Howard,* C. Owen Gwathmey, Michael E. Essington, Roland K. Roberts, and Mike D. Mullen ABSTRACT mature senescence and reduced yields (McConnell et Information on nitrogen (N) fertilization of no-till (NT) cotton al., 1995). (Gossypium hirsutum L.) is needed to optimize lint yields and earlithe optimum N rate for cotton production varies with Research conducted within the mid-south shows that ness. We evaluated five N rates and three application methods for NT cotton production on Loring silt loam (fine-silty, mixed, active, location, soil type, tillage system, winter cover, and apthermic Oxyaquic Fragiudalfs) with natural winter annuals as a cover; plication method. On conventionally tilled (CT) Dunand on Memphis silt loam (fine-silty, mixed, active, thermic Typic dee very fine sandy loam (fine-silty, mixed, active, ther- Hapludalfs) having corn (Zea mays L.) stover as a cover and on mic Typic Endoaqualfs), Ebelhar and Welch (1996) Lexington silt loam (fine-silty, mixed, active, thermic Utlic Hapludalfs) reported optimum yields from banding 50% of the N having winter wheat (Triticum aestivum L.) as a cover. Nitrogen rates at planting followed by banding 50% at pinhead square. of 0, 34, 67, 101, and 134 kg ha 1 were either broadcasted as ammonium nitrate (AN) or injected as urea ammonium nitrate (UAN) at Their evaluation included N rates ( kg ha 1 ) and planting. Additional treatments included broadcasting 67 kg N ha application timing (at planting and three splits) from 1 as AN at planting with either 34 or 67 kg N ha 1 banded 6 wk later. which they concluded that the split application Relative to no N, broadcasting 67 kg N ha 1 as AN increased 4-yr of 101 kg N ha 1 resulted in the highest yields. In an average NT lint yields on Loring silt loam from 739 to 1281 kg lint additional study, Ebelhar et al. (1996) showed that inha 1 and 2-yr average yields on Lexington silt loam from 1086 to 1535 jecting a split (at planting and pinhead) at a higher kg ha 1. A higher N rate (101 kg N ha 1 ) was needed to increase 2- rate (134 kg N ha 1 ) resulted in maximum cotton yields yr average yields on Memphis silt loam from 821 to 1169 kg ha 1. on CT Bosket very fine sandy loam (fine-silty, mixed, Broadcasting AN was a satisfactory placement method producing active, thermic Typic Hapludalfs) and Dubbs silt loam yields equal to or higher than injecting UAN or splitting AN for (fine-silty, mixed, active, thermic Typic Hapludalfs). In NT cotton produced on these loessial soils despite different covers and residues. Mississippi, Thompson and Varco (1996) reported that broadcasting 121 kg N ha 1 as ammonium nitrate (AN) and injecting 110 kg N ha 1 as urea ammonium nitrate Nitrogen (N) fertilization affects yield, maturity, and (UAN) produced maximum NT cotton yields on Marietta fine sandy loam (fine-loamy, siliceous, active, therlint quality of cotton. Evaluating N rates, sources, mic Fluvaquentic Eutrudepts). Hutchinson et al. (1995) and application timing for optimum lint production has reported the need for a higher N rate for both CT and been a major research emphasis within the cotton pro- NT cotton production on Gigger silt loam (fine-silty, ducing states. For cotton, applying an optimum N rate mixed, active, thermic Typic Fragiudalfs) having a winis essential and may differ within the production areas ter wheat cover. Their research indicated that NT yields due to climatic or soil differences. An optimum N rate were increased with injected N up to 78 kg ha should maximize yields, while excessive or inadequate 1 when N applications may reduce cotton yields (Maples and native winter vegetation was the cover, while yields were Keogh, 1971). High N fertilization may produce exceswheat. increased with N rates up to 118 kg ha 1 with winter sive vegetation that delays maturity and harvest, and these conditions may reduce yields and lint quality dur- In Tennessee, cotton yields were maximized at lower ing years of early frost or prolonged fall rain (Hutchinresponse to N fertilization by CT cotton on well-drained N rates than were reported for surrounding states. Yield son et al., 1995; McConnell et al., 1995). Crop maturity is a critical production consideration for cotton producers loessial upland soils ranged from 34 kg N ha 1 (Overton and Long, 1969) to 67 kg N ha along the northern edge of the U.S. Cotton Belt (Gwathkinson, 1986). From a review of Tennessee research, 1 (Howard and Hos- mey and Howard, 1998). Nitrogen deficiency causes pre- Howard and Hoskinson (1990) reported that CT cotton yield responses to N fertilization varied with soil and D.D. Howard and C.O. Gwathmey, Plant and Soil Sciences Dep., physiographic position. The current N recommendation Univ. of Tennessee, West Tennessee Exp. Stn., Jackson, TN 38301; for Tennessee cotton production, regardless of tillage, M.E. Essington and M.D. Mullen, Plant and Soil Sciences Dep., Univ. is to apply 34 to 67 kg N ha 1 to alluvial soils and 67 of Tennessee, P.O. Box 1071, Knoxville, TN ; and R.K. to 90 kg N ha 1 for upland soils (Univ. of Tennessee, Roberts, Agric. Economics and Rural Sociology Dep., Univ. of Tennessee, P.O. Box 1071, Knoxville, TN Received 26 Jan. 2000). These ranges allow the producer to select an *Corresponding author (dhoward2@utk.edu). Abbreviations: AN, ammonium nitrate; UAN, urea ammonium nitrate; DD60, degree days 60; NT, no-tillage; CT, Published in Agron. J. 93: (2001). conventional-tillage.