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United States Department of Agriculture

Agricultural Research Service

Title: Italian Ryegrass and N Source Fertilization in Western Oregon in Two Contrasting Climatic Years. I. Growth and Seed Yield.

Authors
item Griffith, Stephen
item Alderman, Stephen
item Streeter, Donald

Submitted to: Journal of Plant Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 15, 1996
Publication Date: N/A

Interpretive Summary: Prescription based N fertilization of crops in a given local environment begins by understanding factors affecting crop N use and relating these factors to a time scale most directly related to crop growth. For this reason the following objectives were sought for an economically important grass seed crop in western Oregon, Italian ryegrass (Lolium multiflorum Lam.). Objectives were, one, to determine the influence of N-source (NH4- N and NO3-N) on crop growth and seed yield, and two, to determine the relationship between accumulated growing degree days (GDD) and plant development and relate findings to N-source effects on growth and seed yield parameters. N-source treatments had no effect on root and shoot dry mass accumulation in either year. NH4-N source fertilization increased tiller number per unit area, compared to all NO3-N fertilization in 1991 only. N-source did not affect plant dry mass either year. Between year differences dry mass accumulation across N treatments were concluded to be the result of climatic and lodging factors. Grass seed growers could potentially protect the environment by increasing N use efficiency and economic seed yield by more effectively matching timing and amount of N applied to crop demand by using a GDD time scale. By using this scale, greater consistency of on-farm management practices (e.g., fertilization) from year-to-year could result. Data support findings that ryegrass performs best under enhanced ammonium nutrition.

Technical Abstract: Prescription based N fertilization of crops in a given local environment begins by understanding factors affecting crop N use and relating these factors to a time scale most directly related to crop growth. For this reason the following objectives were sought for an economically important grass seed crop in western Oregon, Italian ryegrass. One, to determine the influence of N-source on crop growth and seed yield. Two, to determine the relationship between accumulated growing degree days (GDD) and plant ontogeny and relate findings to N-source effects on growth and seed yield parameters. Five N-source treatments were administered: calcium nitrate, ammonium nitrate, ammonium sulfate, ammonium chloride, and urea- dicyandiamide (DCD). N-source treatments had no effect on root and shoot dry mass accumulation in either year. NH4-N source fertilization increased tiller number per unit area, compared to all NO3-N fertilization in 1991 only. N-source did not affect plant dry mass either year. Between year differences dry mass accumulation across N treatments were concluded to be the result of climatic and lodging factors. Across N treatments, 1992, seed yield was greatest with ammonium nitrate and urea-DCD fertilizers. Temperature was the major regulator of growth and development under conditions of equally applied N. Growth data comparisons on a GDD basis was a very effective means of comparing plant growth between years. Grass seed growers could potentially increase N use efficiency and economic seed yield by more effectively matching timing and amount of N applied to crop demand by using a GDD time scale. By using this scale, greater consistency of on-farm management practices (e.g., fertilization from year-to-year could result.

Last Modified: 9/1/2014
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