Evers, Gerald Wayne

Melson, N. B.

Parsons, Margaret J.

Vietor, D. M.

English

Texas A&M University

Nitrogen uptake and distribution in annual ryegrass

Texas A&amp;M Repository

    PUBLICATIONS 2004 NITROGEN UPTAKE AND DISTRIBUTION IN ANNUAL RYEGRASSG. W. Evers, N. B. Melson, M. J. Parsons, and D. M. VietorBackground. Nitrogen (N) is the most limiting of the three major plant nutrients forannual ryegrass growth. Nitrogen level in leaves has a direct effect on the photosynthetic ratewhich is responsible for the synthesis of carbohydrates that drives plant growth. Because of thelow fertility, sandy soils in East Texas, from 100 to 250 Ib N/acre are necessary for good ryegrassgrowth. Because N is rapidly solubilized in water, it can be lost by leaching through the soil pastthe plant root zone or in runoff during heavy rainfall. Nitrogen loss by leaching results in lowutilization of the applied N and possible nitrate contamination of groundwater. For these reasonsit is important to know how N rate and time of application influence N uptake and its distributionin the plant. TAM 90 annual ryegrass was seeded at 25 Ib/acre in a prepared seedbed in October2001 and 2002. Fall growth was measured on plots fertilized with 0, 50, 100, or 150 Ib N/acre atryegrass emergence. Winter growth was measured on plots fertilized with 50 Ib N/acre atemergence to provide moderate fall growth and then mowed to a 2-in. height in late Decemberand fertilized with 0, 50, 100, or 150 Ib N/acre. Spring growth plots were treated the same as thewinter plots except they were fertilized with 50 Ib N/acre in late December, mowed to a 2-in.height in late February, and fertilized with 0, 50, 100, or 150 Ib N/acre. Plots were sampled at 2,4, 6, and 8 weeks after the N fertilizer treatments were applied. Plants were separated into roots,stems, and leaves and analyzed for N.Research Findings. Nitrogen concentration increased in root, stems, and leaves as Nfertilizer rate increased both years (data not shown). Nitrogen concentration in all plantcomponents decreased, from fall to winter to spring (Table 1). Leaves always had the highest Nconcentration followed by stems and then roots. The higher N level (directly related to proteinlevel) in the leaves is one of the reasons they have a higher nutritive value than stems. Thepercentage of total plant N in the roots, stems, and leaves differed between the 2 years. The firstyear only 10% of the N was found in the roots during the fall and then increased to about 20% inwinter and spring (Table 2). The second year, when fall growth was about 50% less, almost 40%of the plant N was in the roots and then decreased through winter and spring. Percentage of totalplant N in the stems increased with succeeding seasons which coincides with increasing stemweight. Percent N efficiency (percent of the N applied that was taken up by the plant) wascalculated at 6 weeks of growth (Table 3). Comparing N efficiency during the fall for both yearsdemonstrates what an impact growing conditions can have on N efficiency. With yields over2000 Ib/acre at 6 weeks in 2001-2002, N efficiencies were from 44 to 54 %. In 2002-2003 when11yields were less than 1000 lb/acre at 6 weeks, N efficiencies were only 8 to 14%. Althoughmaximum winter yields occurred at 100 lb N/acre the first year and 50 Ib N/acre the second year,N efficiency was similar or increased slightly from 50 to 150 lb N/acre. Ryegrass continued totake up N without an increase in plant growth.Application. Nitrogen concentration was highest in the leaves followed by stems androots. Most of the plant N was in the leaves in the fall but shifted to the stems with succeedingseasons. Annual ryegrass can take up additional N without an increase in growth.bdlfT bl 1 Aa e vera~e m o~en concentration 0 roots, stems, an eaves )y season.2001-2002 2002-2003Season Roots Stems Leaves Roots Stems Leaves-------------------------------------------------N (%}--------------------------------------------Fall 1.23 at 2.24 a 3.60 a 1.59 a 3.13 a 3.62 aWinter 1.23 a 1.83 b 3.34 b 1.28 b 1.96 b 3.51bSpring 0.93 b 1.38 c 2.89 c 0.98 c 1.46 c 2.64 ctValues 10 a column followed by the same letter are not slgmficantly dIfferent at the 0.05 level,Fishers Protected LSD.bd It std' trib fT bl 2 Aa e veragem o~en IS u Ion among roo s, ems, an eaves )y season.2001-2002 2002-2003Season Roots Stems Leaves Roots Stems Leaves-------------------------------------------------N (%)--------------------------------------------Fall 10.0 ct 22.1 c 67.9 a 38.8 a 30.3 c 30.9 bWinter 21.6 a 35.9 b 42.8 b 25.9 b 34.6 b 39.5 aSpring 18.0 b 42.6 a 39.4 c 15.9 c 51.6 a 32.5 btValues in a column followed by the same letter are not SIgnIficantly different at the 0.05 level,Fishers Protected LSD.Percent of nitrogen applied that was taken up by plants 6 weeks after nitrogenbTable 3.r fappilca Ion yseason.2001-2002 2002-2003Nrate Fall Winter Spring Fall Winter SpringIb/acre --------------------------------------Nitrogen efficiency (%)---------------------------------50 54 47 73 14 29 58100 54 53 64 8 30 65150 44 50 39 10 35 6012

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Nitrogen uptake and distribution in annual ryegrass

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Texas A&M University

Texas A&M Repository

Nitrogen uptake and distribution in annual ryegrass

Abstract

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Full text

Available Versions

Texas A&M University

Texas A&amp;M Repository

Texas A&M Repository