Grain Yield Performance of Rice Cultivars Grown in Northeast Arkansas as Influenced by Seeding Date

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1 RICE CULTURE Grain Yield Performance of Rice Cultivars Grown in Northeast Arkansas as Influenced by Seeding Date C.E. Wilson Jr., R.J. Norman, N.A. Slaton, M. Duren, D.L. Boothe, K.A.K. Moldenhauer, and J.W. Gibbons ABSTRACT The growth and development of the rice cultivars produced in Arkansas are temperature dependent, and therefore, the date at which they are seeded greatly influences their maturity and potential grain yield. A study has been initiated at the Northeast Research and Extension Center, Keiser, Ark., to determine the optimum seeding dates for rice producers in this region of Arkansas. Eleven widely grown rice cultivars and one new cultivar ( Medark ) were studied over three seeding dates. The highest grain yields, averaging 153 bu/acre, were measured when the rice cultivars were seeded on 30 April. The rice cultivars with the highest yields when seeded on 30 April were LaGrue, Cypress, and Bengal. INTRODUCTION The growth and development of the rice cultivars produced in Arkansas are temperature dependent, and therefore, the date at which they are seeded greatly influences their maturity and potential grain yield (Norman et al., 1999). The short-season cultivars are typically not the best choices for late seeding. Consequently, seedingdate studies are very important in determining the best seeding-date window for a particular cultivar in a particular region. A seeding-date study that is inherently incorporated into the annual DD50 Program study is conducted on newly released rice cultivars at the Rice Research and Extension Center near Stuttgart. Being somewhat 327

2 AAES Research Series 517 centrally located in the rice-growing region of Arkansas, data from the DD50 study and other seeding-date studies at this location are extrapolated across the rest of the ricegrowing region of Arkansas based on known temperature differences across this region. Recently, the extrapolation of the data collected at Stuttgart to growing conditions in northeast Arkansas has been questioned by rice producers and extension personnel in that area. Although data indicate only a 3 to 4 F temperature difference between east-central and northeast Arkansas, producers in northeast Arkansas feel this is not a true reflection of growing-condition differences between the two areas. Their practical field experience suggests that cutoff dates for the rice cultivars Bengal and Cypress may be as much as 10 days earlier than currently recommended for this region. These producers indicate that late-seeded fields produce rice that has excessive blanking and reduced yields as well as lower milling yields. Because of this concern, a seeding-date study was initiated at the Northeast Research and Extension Center, Keiser, with the objective of determining the influence of seeding date on the grain yield performance of important rice cultivars grown in northeast Arkansas. PROCEDURES This seeding-date study was conducted at the Northeast Research and Extension Center, Keiser, Ark., on a Sharkey clay (very-fine, smectitic, thermic Chromic Epiaquerts). The rice cultivars selected for this study were: Ahrent, Bengal, CL 161, Cocodrie, Cypress, Francis, Jefferson, LaGrue, Medark, Kaybonnet, Wells, and RiceTec XL8. The cultivars were arranged in a randomized complete block design with four replications and were seeded on the following dates: 18 April, 30 April, 27 May, and 10 June The rice was drill-seeded in 9-row (7-in. spacing) wide plots, 15 ft in length. Nitrogen fertilizer (urea) was applied preflood at a rate of 150 lb N/acre at the 4- to 5-leaf growth stage, and a flood was immediately established and maintained until maturity. At maturity, 12 ft of the center four rows of each plot were harvested with a small-plot combine, and the moisture content and weight of the grain were determined. Ratings for kernel smut (Neovossia horrida) were made for Ahrent, CL 161, Cocodrie, Francis, LaGrue, and Wells to determine the effects of seeding date on the development of this disease in cultivars of varying susceptibility. Grain yields are expressed on a 12% moisture basis in bu/acre. Statistical analyses were conducted with SAS and mean separations were based upon Fisher s protected LSD (P = 0.05) where appropriate. RESULTS AND DISCUSSION The time required for emergence ranged from 14 days for the 18 April and 27 May seeding date to 6 days for the 10 June seeding date (Table 1). While the late seeding date required shorter time to emerge, the April and May seeding dates were similar. Cooler than normal weather in May delayed emergence during this time period, while warm weather in early April encouraged emergence. The days between emergence and 328

3 B.R. Wells Rice Research Studies 2003 flooding were similar for the seeding dates, indicating that the difference in days to flood from seeding is due to differences in emergence. The exception was the 30 April seeding date which required approximately a week longer to reach the 4- to 5-leaf growth stage. The average days required to reach 50% heading ranged from 78 days for the 27 May seeding date to 89 days for the 30 April seeding date. The week delay in flooding the 30 April seeding date seemed to result in approximately a week delay in heading date, compared to the other seeding dates. This is supported by relatively similar time periods required to reach 50% heading. The time between flooding and 50% heading ranged from 51 to 54 days. The 27 May seeding date was not harvestable due to severe black bird infestations after heading. The mean grain yields for all cultivars when seeded on 18 April, 30 April, and 10 June were 140, 153, and 85 bu/acre, respectively (Table 2). Similar to previous years (Norman et al., 2003), most cultivars performed better when planted near the end of April than in mid-april or early June. Overall, the highest-yielding cultivars were LaGrue, Bengal, and Cypress. The rice cultivars with the highest yields were LaGrue, Bengal, and Cypress, with an average yield of 185, 163, and 171 bu/acre, respectively, when seeded on 30 April. Those cultivars with the most stability included LaGrue, Kaybonnet, and Bengal, with each of these cultivars showing less than 40% yield decrease when seeding was delayed until June. In contrast, yields of Ahrent, CL 161, and Wells were reduced in excess of 50% when seeded in June compared to those cultivars seeded in April. Kernel smut incidence was highest in Cocodrie, Francis, and LaGrue, which are typically rated as very susceptible (Table 3). The rice cultivars generally showed disease incidence and severity levels that corresponded to their disease ratings (Tables 3 and 5). Specifically, those cultivars that are rated very susceptible (Cocodrie, Francis, and LaGrue) tended to have higher incidence and severity of kernel smut than those rated as susceptible (CL 161) or moderately susceptible (Wells and Ahrent). Kernel smut incidence tended to increase as seeding date was delayed; with maximum disease occurring for the late May seeding dates (Table 4). Similarly severity also tended to increase, maximizing in the late May seeding dates, particularly for the cultivars most susceptible to kernel smut (Table 5). Even the lower susceptible cultivars increased significantly in severity of kernel smut with delayed seeding, although the severity was much less than the very susceptible cultivars even in the late May seeding. Few differences were observed among cultivars when seeded early. SIGNIFICANCE OF FINDINGS Twelve cultivars were studied over three seeding dates to assist with variety selection at various seeding dates. The highest grain yields, averaging 153 bu/acre, were obtained when the rice cultivars were seeded on 30 April. The cultivars with the highest and most stable yields were LaGrue, Bengal, and Cypress. The order of the remaining cultivars in grain yield performance over the three seeding dates were: Francis, Cocodrie, Jefferson, XL8, Ahrent, Wells, Medark, and Kaybonnet. 329

4 AAES Research Series 517 ACKNOWLEDGMENTS This research was funded by the Arkansas Rice Research and Promotion Board. LITERATURE CITED Norman, R.J., N.A. Slaton, and K.A.K. Moldenhauer Development of the DD50 database for new rice cultivars. In: R.J. Norman and T.H. Johnston (eds.). B.R. Wells Rice Research Studies University of Arkansas Agricultural Experiment Station Research Series 468: Fayetteville, Ark. Table 1. General seeding, seedling emergence, and flooding-date information for the seeding date study at the Northeast Research and Extension Center near Keiser, Ark., during Seeding date Parameter 18 April 30 April 27 May 10 June Emergence date 2 May 12 May 10 June 16 June Flood date 29 May 16 June 7 July 15 July Average 50% heading date 21 July 9 August 27 August 7 September Days from seeding to emergence Days from seeding to flooding Days from seeding to 50% heading Days from emergence to flooding Days from emergence to 50% heading

5 B.R. Wells Rice Research Studies 2003 Table 2. Influence of seeding date on grain yields of 12 rice cultivars grown at the Northeast Research and Extension Center near Keiser, Ark., during Grain yield Cultivar/hybrid 18 April 30 April 10 June Mean (bu/ace) Ahrent Bengal CL Cocodrie Cypress Francis Jefferson Kaybonnet LaGrue Medark Wells XL Mean C.V.(%) Table 3. Comparison of kernel smut incidence on six rice cultivars across four seeding dates at the Northeast Research and Extension Center, Keiser, Ark., during Cultivar Kernel smut incidence (%) Ahrent 37.8 CL Cocodrie 65.9 Francis 65.6 LaGrue 55.5 Wells

6 AAES Research Series 517 Table 4. Kernel smut incidence of rice from four seeding dates at the Northeast Research and Extension Center, Keiser, Ark., during Seeding date Kernel smut incidence (%) 18 April April May June Table 5. Influence of seeding date on kernel smut severity in six rice cultivars at the Northeast Research and Extension Center, Keiser, Ark., during Kernel smut severity Cultivar 18 April 30 April 27 May 10 Jun Ahrent CL Cocodrie Francis LaGrue Wells Mean within seeding dates 1.0 between seeding dates 332