70139 Annual Ryegrass (Lolium multiflorum Lam.) Production and Quality As Influenced by Planting Date and Irrigation During Early Seedling Development.

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Sunday, February 5, 2012
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William B. Smith1, Elizabeth A. Guertal2, Edzard van Santen2, Russell B. Muntifering3 and Donald M. Ball4, (1)Dept. of Animal Sciences, Dept. of Agronomy & Soils, Auburn University, Auburn, AL
(2)Dept. of Agronomy & Soils, Auburn University, Auburn, AL
(3)Dept. of Animal Sciences, Auburn University, Auburn University, AL
(4)Alabama Cooperative Extension System, Auburn University, Auburn University, AL
Annual ryegrass (Lolium multiflorum Lam.) is a commonly utilized cool-season forage in the Southeast. Yield is typically greater in early spring than winter, and management to achieve greater growth during late autumn/winter could increase total seasonal production. We conducted a field experiment to determine ryegrass DM yield as affected by planting date and irrigation during early seedling development. Ninety-six plots were established at 2-wk planting-date (PD) intervals (16 plots/date) at the E.V. Smith Research Center in Tallassee, AL, beginning in September and ending in November 2008. Cultivars were Marshall, Gulf, Shiwasuaoba, and SWIPAR. The experimental design was a randomized complete block (n = 4) with split-plot restriction on randomization in which irrigation treatments (+,–) were main plots and cultivars were subplots. Immediately after seeding, 2.54 cm of water was applied via a drip system to irrigated plots. Water applied for 2 wk thereafter was based on evapotranspiration (ET) and was gradually reduced to 65% ET. Plots were harvested when forage canopy height reached 20 cm. There was no effect of irrigation on cumulative forage yield from PD 1, 3, 4, 5 and 6; however, yield was significantly increased (P = 0.004) by irrigation for PD 2.  Across the first 3 PD, mean DM yield penalty of a 2-wk delay in seeding was 67 kg/ha/d in the first (primary growth) harvest and 55 kg/ha/d in the second (first regrowth) harvest. Regression of forage IVDMD vs. concentration of total nonstructural carbohydrates (TNC) had r2 values of 0.33 and 0.42 (first harvest), 0.77 and 0.59 (third harvest), and 0.41 and 0.96 (fourth harvest) for the first and second planting dates, respectively. Data are interpreted to mean that seasonal forage production from early plantings of ryegrass may be increased vs. delayed planting, and that forage concentration of TNC is an increasingly important determinant of nutritive quality with advancing forage regrowth cycles.