|Spring Nitrogen Fertilization of Perennial Ryegrass Seed Crop
|Year of Publication
|Young, WC, Youngberg, HW, Chilcote, DO, Hart, JM
|Journal of Production Agriculture
Nearly the entire U.S. supply of perennial ryegrass (Lolium perenne L.) seed is produced in western Oregon. Little information is available regarding N fertilization effects on seed production of this crop in the region. Effects of 16 combinations of four N rates (0, 54, 81, and 108 lb N/acre) applied at the double-ridge (DR) stage of development, and the same four rates applied at the spikelet initiation (SI) stage, were measured on seed production of two older cultivars, Linn (forage-type) and Pennfine (turf-type). In a second experiment, effects of 60, 100, and 140 lb N/acre applied at the DR stage were also measured on two more recently developed turf-type cultivars, Regal and Pleasure. In both experiments, between 25 and 42 lb N/acre was applied in the fall. Seed yield of cultivar Linn was near maximum at 54 to 81 lb N/acre, but Pennfine seed yield was the highest at 108 lb N/acre. Growth stage when N was applied did not affect seed yield of either cultivar. Also, splitting the N application was not superior to applying all of the N at one time. Responses of Regal and Pleasure seed yield to N rates varied among years. In years without severe lodging, seed yields of Regal and Pleasure were the highest at 140 lb N/acre. Research Question Nearly the entire U.S. supply of perennial ryegrass seed is produced in Oregon. Growers in the region typically apply 100 to 150 lb N/acre in the spring, split 50% in March and 50% in April, which correspond to double-ridge (DR) and spikelet initiation (SI) stages, respectively. Because of the recent widespread concern regarding the loss of nitrate into underground and surface water, and the ever-increasing cost of N fertilizer, re-evaluation of spring N fertilization of perennial ryegrass seed crop is warranted. This research was conducted to determine whether perennial ryegrass seed crop responds to spring N applications, and if so what the adequate rate is. The study was also designed to determine the appropriate application timing, and whether or not splitting spring-applied N is beneficial. Literature Summary More than half of the world's perennial ryegrass seed is produced in Oregon. However, nearly all the published information regarding N fertilization rates and timing effects on seed yield of this crop are from research conducted in Europe and New Zealand. Research conducted in those countries indicates that optimum levels of spring applied N is between 60 and 120 lb/acre, and seed yield is apparently insensitive to timing of N application from apex initiation to anthesis. Based on unpublished research, the Oregon State University Extension Fertilizer Guide recommends application of 80 to 100 lb N/acre in the spring split 50% in March and 50% in April. Seed growers in Oregon typically apply 30% more than this recommended value. More information on the effects of N rate and application timing on perennial ryegrass seed yield would help in making recommendations for more efficient use of the fertilizer to meet crop demand while safeguarding the environment. Study Description Two experiments were conducted on perennial ryegrass seed crops at Corvallis, OR; the first experiment during 1982–1983 and the second during 1989–1991. Cultivars: Older cultivars Linn (forage-type) and Pennfine (turf-type) in Exp. 1, and more recently developed turf-type cultivars Regal and Pleasure in Exp. 2. Soil type: Woodburn silt loam in Exp. 1, and Willamette silt loam in Exp. 2. N application timing: DR and SI in Exp. 1, and only DR in Exp. 2. N rates: All 16 combinations of 0, 54, 81, and 108 lb/acre applied at DR, and the same rates applied at SI, in Exp. 1; and 60, 100, and 140 lb/acre applied only at DR in Exp.2. Previous crop: Sites were fallowed for 2 yr before starting Exp. 1. In Exp. 2, Regal followed Regal and Pleasure followed Newport Kentucky bluegrass. Fall fertilizer application: 42 lb N /acre (Exp. 1) and 30 lb N/acre (Exp. 2) during the establishment year, and 30 lb N/acre following harvest of subsequent seed crops in both experiments. Plant density: Seeding rate was 6 lb/acre, planted in 12-in. row spacing. Applied Questions What is the appropriate rate of spring applied N for perennial ryegrass seed production? Although seed yields of both Linn and Pennfine varied between years, the trends for N treatment effects on seed yields were the same for the 2 yr. Averaged across years, Linn seed yield was near maximum when 54 to 81 lb N/acre was applied (Fig. 1). Pennfine seed yield was the highest when 108 lb N/acre was applied. Considering that Linn is a forage-type and Pennfine is a turf-type, results suggest that appropriate rate of spring-applied N for seed production of perennial ryegrass is about 60 to 80 lb/acre for forage-type cultivars and 80 to 100 lb N/acre for turf-type cultivars. Seed yield of newer turf-type cultivars Regal and Pleasure varied among years (Fig. 2). In 1991, when little crop lodging was observed, seed yields of both cultivars were the greatest at 140 lb N/acre. These findings suggest that the seed yield of more recently developed turf-type cultivars may respond positively to spring N rates up to 140 lb/acre. Should spring N be applied at DR or SI stages of development? Figure 1 indicates that, for Linn and Pennfine, there was little difference between the two application timings when 108 lb N/acre was applied. Data suggest, however, that if only 54 lb N/acre is used for Linn, it may be more beneficial to apply it at the DR stage. Is splitting spring-applied N advantageous for seed production compared with single application? Comparing Linn and Pennfine seed yield for 108 lb N/acre, applied at DR or at SI, with 54 lb N/acre applied at both stages of development indicates that splitting spring N is not superior to applying all of the N at one time (Fig. 1). 1 Effects of spring-applied N fertilization treatments on seed yield of perennial ryegrass cultivars Linn and Pennfine. The first number in bars is N rate (pounds per acre) applied at the double-ridge stage of plant development and the second number is the rate applied at spikelet initiation. The numbers in parentheses are total N rates applied. Seed yields are averages of two years. 2 Effects of spring-applied N on seed yield of perennial ryegrass cultivars Regal and Pleasure in 1989, 1990, and 1991.