Sowing

About: Sowing is a research topic. Over the lifetime, 33888 publications have been published within this topic receiving 273438 citations. The topic is also known as: seeding.

Nitrogen Application Increases Yield and Early Dry Matter Accumulation in Late‐Planted Soybean

Abstract: In double-cropped soybean [Glycine max (L.) Merr.] planting is delayed, with a corresponding decrease in yield associated with photoperiod-induced early flowering and reduced accumulation of dry matter during the vegetative growth period. Application of nitrogen (N) has been shown to improve yield of late-planted soybean. We conducted a field study to determine the optimum economic rate of N that would stimulate early dry matter accumulation, and thus yield, in late-planted soybean. The effects of three planting dates (mid-June, late-June, and mid-July), two MG VIII cultivars (Kuell and Prichard), and five N rates (0, 25, 50, 75, and 100 kg ha -1 ) were studied for 2 yr at three Alabama locations (Fairhope, Shorter, and Crossville). Nitrogen application of 60 to 70 kg ha -1 maximized yield and R1 dry matter accumulation. However, N reduced nodule number and mass, but had no effect on R1 plant height, mature plant height, or seed quality, protein and oil content. Yield was reduced linearly by later planting, but there was no interaction between N rate and planting date for yield. Kuell was taller at maturity and had more R1 dry matter than Prichard, but Kuell yielded more than Prichard in only one environment and there was no cultivar X N rate interaction for yield. At current prices for N and soybean, we concluded that N can be a viable input for double-cropped soybean at an optimal economic rate of 59 kg ha -1 .

Seeding Rates for Establishing Big Bluestem and Switchgrass with Preemergence Atrazine Applications1

Abstract: The purpose of this study was to determine seeding rates for establishing switchgrass (Panicum virgatum L.) and debearded big bluestem (Andropogon gerardii Vitman) when atrazine |6-chloro-Aethyl-W-(l-methylethyl)-l,3,5-triazine-2,4-diaminel is used as a preemergence herbicide. The high seed cost of these grasses makes it uneconomical to use higher seeding rates than necessary. The study was conducted on four eastern Nebraska sites during the period 1981 to 1985. The experimental design was a randomized complete block with six replications. Treatments were grasses (big bluestem and switchgrass) and seeding rates [107, 215, 325, and 430 pure live seeds (PLS) m~] in a factorial arrangement. Plots were seeded in late spring with a plot seeder with double disk openers on a clean, firm seedbed, and broadcast sprayed with 2.2 or 3.0 kg ha ' atrazine the day after seeding. Stands and forage yields were measured the first (Year 1) and second year (Year 2) following establishment. The 107 PLS m~ seeding rate resulted in thinner, but still acceptable, stands (10-20 plants m~) than the higher seeding rates in Year 1 and at two of the sites in Year 2. The stands from the higher rates, in general, did not differ within a site and were good to excellent (>20 plants nv~). The lowest seeding rate produced lower forage yields than the other rates in Year 1, but these differences were significant at only one site. There were no differences for Year 1 yield for the other rates or for Year 2 yields for all rates. Additional index words: Panicum virgatum L., Andropogon gerardii Vitman, Forage yields, Establishment, Prairie grasses, Warm-season grasses. ______________ S rates for switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) were developed primarily by empirical methods. Cornelius (1944) reported that 400 pure live seeds (PLS) m~ provided ample seeds for establishment of a warmseason grass mixture and that 20 established plants m~ would give a stand similar to that of native prairie in 2 yr. Launchbaugh (1966), in a stand establishment survey of over 3000 grass plantings in the Great Plains, classified plantings with 10 or more seedling m~ as good stands. In a designed study at Hays, KS, Launchbaugh and 1 A contribution of the USDA-ARS and the Univ. of NebraskaLincoln. Published as Paper no. 8066, Journal Series, Nebraska Agric. Res. Div. Received 19 May 1986. 2 Supervisory research geneticist, USDA-ARS, and adjunct professor, Dep. of Agronomy, Univ. of Nebraska, Lincoln, NE 68583. Published inAgron. J. 79:509-512 (1987). Owensby (1970) determined that establishment-year stands of 10 to 20 plants m~ of native grasses including big bluestem and switchgrass were generally ready to be grazed the following year. Seeding rates of 200 to 300 PLS m~ were needed to achieve these stands with big bluestem, but rates greater than 400 PLS m~ were needed for switchgrass. In a set of designed studies in eastern Nebraska, Sail (1963) determined that seeding rates in excess of 400 PLS m~ were not necessary for establishing switchgrass and indiangrass [Sorghastrum nutans (L.) Nash]. He also determined that midto late-spring dates of seeding are most suitable for these grasses in eastern Nebraska. Seeding rate recommendations of 200 to 400 PLS m~ for switchgrass and big bluestem are based on these reports, studies, and other unpublished observations. Two recent developments necessitated the re-evaluation of these seeding recommendations. Martin et al. (1982) documented that switchgrass and big bluestem have seedling tolerance to preemergence applications of atrazine [6-chloro-7V-ethyl-A'-(l-methylethyl)-l,3,5-triazine-2,4-diamine] and that preemergence applications of this herbicide greatly improved establishment of these grasses by reducing weed competition. The seed unit of big bluestem, which includes the fertile spikelet, the joint of the raceme, and the stalk of the sterile spikelet, has an awn and dense pubescence, which makes the seed extremely chaffy (Wheeler and Hill, 1957). Brown et al. (1981) developed a method of debearding (removing the chaffy awns and other seed appendages) big bluestem, which greatly increases its bulk density and its ability to flow through planting equipment. Previous seeding recommendations were based on seedings with chaffy seed. In contrast to big bluestem, switchgrass has a smooth seed that flows easily through planters. The purpose of this study was to determine seeding rates for switchgrass and debearded big bluestem when atrazine is used as a preemergence herbicide. Recently, Vassey et al. (1985) studied the optimum rate and date for seeding switchgrass in central Iowa when atrazine is used as a preemergence herbicide. They used seeding rates of 3.4, 6.7, 10.1, 13.4, and 16.8 kg ha" for 'Cave-in-Rock' switchgrass in early, 510 AGRONOMY JOURNAL, VOL. 79, MAY-JUNE 1987 mid-, and late-spring plantings. Seed weight values were not reported. If the mean of published seed weight values of 859 seeds g-' (Wheeler and Hill, 1957) and 814 seeds g-I (Martin and Leonard, 1967) is used to convert these values to PLS per square meter, the planting rates are equivalent to 284, 560, 844, 1120, and 1404 PLS m-2, respectively. Their conclusions were that switchgrass should be seeded during mid-to-late April or early May and that when atrazine is used for weed control, a seeding rate of 3.4 kg ha-I PLS (284 PLS m-2) is adequate to obtain productive stands. They suggested that higher seeding rates would be needed only if an adequate planter was not available or if severe stress conditions were anticipated. Seed rates lower than those tested by Vassey et al. (1985) were included in this study because the high seed cost of these grasses makes it uneconomical to use higher seeding rates than necessary. MATERIALS AND METHODS Seeding rate studies were conducted at the University of Nebraska Agricultural Research and Development Center at Mead, NE (35 km west of Omaha, NE), in 1981, 1982, and 1983, and on the Leonard Christian farm in Pawnee County, NE (120 km south of Omaha, NE), in 198 1. Seedings at Mead were made in 198 1 and 1983 on a Sharpsburg silty clay loam (Typic Argiudoll) and in 1982 on a Butler silty clay loam (Abruptic baquo l l ) . The Pawnee County seeding was made on a Pawnee clay loam (Aquic Argiudoll). Each seeding rate experiment was a randomized complete block with six replicates. Treatments were grasses, big bluestem and switchgrass, and seeding rates, 107, 215, 323, and 430 PLS m-2 (10, 20, 30, and 40 PLS ft.-'), in a factorial arrangement. Plots were seeded using the plot drill described by Vogel (1978). The plot size was 1.2 by 4.3 m long. The quantity of seed necessary to seed a 1.2by 6-m (7.4-m2) plot was placed in the drill's cone, and the cone was set to make one revolution in 6 m. Seeding began in the middle of an alley, and the drill was empty and cleaned in the middle of the next alley; the process was then repeated. After emergence, plots were uniformily trimmed to 4.3 m in length. Germination percentages and 100-seed weights of the seed lots used to determine PLS are listed in Table 1. Big bluestem seed was debearded using a small laboratory debearder that duplicates the results of the debearder described by Brown et al. (1981). The plots-were seeded into clean, firm seedbeds to a depth of 1 cm. The seeding dates were 3 June (Mead, 1981), 29 May (Pawnee, 1981), 4 June (Mead, 1982), and 24 May (Mead, 1983). Atrazine was broadcast on plots the day after seeding at a rate of 2.2 kg a.i. ha-', except at Mead in 1981 when a 3.0 kg ha-' rate was used. The experiments did not receive additional herbicide treatments the establishment year, except for Mead Table 1. Seed lots used to seed the rate of seeding studies in eastern Seed lot 100-seed weight Germination Nebraska in 1981, 1982, and 1983.

Relating Preseason Soil Nitrogen to Maize Yield in Tree Legume-Maize Rotations

Abstract: Legumes can be an important source of N for cereals in tropical, subsistence farming systems that use little or no fertilizers. Out objective was to identify measures of soil N availability, following growth of diverse legumes, that correlated with yield of a subsequent unfertilized maize (Zea mays L.) crop. Unfertilized maize followed nine 3-yr-old systems (six monocultures of planted trees legumes, a groundnut [Arachis hypogea L.]-maize-soybean [Glycine max (L.) Merr.] rotation, an uncultivated fallow with natural regrowth of vegetation, and unfertilized maize monoculture) in two experiments on a Ustic Rhodustalf in eastern Zambia. Total soil C and N before maize planting were not related to grain yield of maize. Preseason soil inorganic N (NO 3 + NH 4 ), aerobic N mineralization, and light-fraction N (N in macroorganic matter, 150-2000 μm and <1.37 Mg m 3 ) at 0- to 15-cm depth correlated (P < 0.01) with maize grain yield. Preseason inorganic N combined with light-fraction N accounted for 59% of the variance in maize grain yield. The predictahility of maize yield was slightly improved (64% of the variance) by including the population of the parasitic weed striga [Striga asiatica (L.) Kuntze] with preseason inorganic N and light-fraction N. The results suggest that yield of unfertilized, rain-fed maize following different rotational systems on a N-limiting soil in an area with monomodal rainfall was strongly related to the additive effects of preseason soil inorganic N and a soil N fraction related to N mineralization.