A Split Application Approach to Nitrogen and Growth Regulator Management for Perennial Ryegrass Seed Production

Abstract

Experiments were conducted during 2009 and 2010 in first year perennial ryegrass (Lolium perenne L.) fields under limiting or adequate spring N. Three N application methods (single, two‐split, and three‐split), five growth regulators (split and single applications of prohexadione Ca or trinexapac ethyl) and two spring N rates (56 or 100 kg N ha−1) were evaluated in a split‐split plot design. Under adequate spring N, all N application methods resulted in similar seed yields but when spring N was limiting, a single application of N resulted in up to 14% greater yield vs. the three‐split. The three‐split N application improved relative chlorophyll index (RCI) 6 to 20% late in the harvest season and reduced stem rust (Puccinia graminis Pers. subsp. graminicola) area under the disease progress curve (AUDPC) by 18 to 39% vs. the single N application. Other effects of three‐split N applications observed in 2010 were 8 to 19% less biomass, 2 to 3% greater harvest index (HI), 4% greater seedling vigor, and 25% less lodging. The split prohexadione Ca treatment gave the most consistent results and when vegetative growth was greatest it resulted in a 36% increase in seed yield, a 5.5% increase in HI, 14 cm shorter plants, 70% less lodging, 30% greater RCI, 13% lower stem rust incidence, and 3% lower stem rust severity. Development of a model to optimize rates and timings for split N and growth regulator applications based on growth stage, soil N availability, and growing degree days (GDD) could improve efficacy of split applications.

Seeding Rate, Row Spacing, and Nitrogen Rate Effects on Perennial Ryegrass Seed Production

“…Therefore, our analysis initially tested treatment effects across all environments along with the effect of environment (Table 1). Growing degree day accumulation, an important influence on agronomic characteristics in this region (Koeritz et al, 2013), began earlier during the 2010 harvest season (E1 and E2) than in the 2011 harvest season (E3 and E4) (Fig. Growing degree day accumulation, an important influence on agronomic characteristics in this region (Koeritz et al, 2013), began earlier during the 2010 harvest season (E1 and E2) than in the 2011 harvest season (E3 and E4) (Fig.…”

“…Growing degree day accumulation, an important influence on agronomic characteristics in this region (Koeritz et al, 2013), began earlier during the 2010 harvest season (E1 and E2) than in the 2011 harvest season (E3 and E4) (Fig. Previous observations have indicated that more N may be required for optimum perennial ryegrass seed yield at the site of E3 and E4 in this study (Kurcinka, 2009;Koeritz et al, 2013). The soil type for E1 and E3 (Roseau) was also different from the soil type for E2 and E4 (Roosevelt).…”

“…‡ nS, indicates not significant P < 0.05. A study evaluating N and growth regulator effects on stem rust in perennial ryegrass also indicated that stem rust incidence was less severe in plants that were shorter with more robust stems, which may have been due to greater cell density, cell wall thickening, or concentration of plant protective compounds (Koeritz et al, 2013). (Table 2); however, the greatest difference between the 10and 30-cm RSW treatments in terms of percentage volunteer wheat (9 vs. 20% cover for the 10-and 30-cm RSW, respectively) was observed when the perennial ryegrass crop was seeded at a rate of 5.2 kg PLS ha −1 and fertilized at the 67 kg ha −1 N rate (Data not shown; P < 0.05).…”

“…Urban) severity was greater at lower planting densities and suggested that differences in microenvironment at different plant densities could affect pathogen growth (Dill-Macky and Roelfs, 2000). In northern Minnesota, higher spring N rates (100 vs. 56 kg N ha −1 ) can increase vegetative biomass production by up to 45% and fertile tiller number by up to 15%; both of these canopy characteristics affect light interception (Koeritz et al, 2013). For organic seed production in Denmark, researchers have suggested that wider row spacing of 24 cm can be used, without affecting seed yield, to facilitate mechanical weed control (Deleuran et al, 2010).…”

Trinexapac-ethyl rate and application timing effects on seed yield and yield components in tall fescue

“…Reduction in stem length and lodging by TE resulted in increased seed yield in perennial ryegrass (Lolium perenne L.) seed crops (Borm and van den Berg, 2008;Rolston et al, 2010;Koeritz et al, 2013;Chastain et al, 2014a). While the effects of TE on lodging control and seed yield in perennial ryegrass (Rolston et al, 2010;Koeritz et al, 2013;Chastain et al, 2014a) and strong creeping red fescue (Festuca rubra L. subsp. rubra) seed crops (Zapiola et al, 2006(Zapiola et al, , 2014 are well known, there have only been three investigations on these effects of TE in tall fescue.…”