Effect of shallow, rotary cultivation with vertical tines and nitrogen fertilization on the seed productivity of creeping red fescue

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1 Effect of shallow, rotary cultivation with vertical tines and nitrogen fertilization on the seed productivity of creeping red fescue N. A. Fairey 1 and L. P. Lefkovitch 2 1 Beaverlodge Research Farm, Agriculture and Agri-Food Canada, P.O. Box 29, Beaverlodge, Alberta, Canada T0H 0C0 ( faireyn@agr.gc.ca); and 2 51 Corkstown Road, Nepean, Ontario, Canada K2H 7V4. Contribution no. BRS , received 10 December 2001, accepted 21 May Fairey, N. A. and Lefkovitch, L. P Effect of shallow, rotary cultivation with vertical tines and nitrogen fertilization on the seed productivity of creeping red fescue. Can. J. Plant Sci. 82: A field study in the Peace River region of northwestern Canada evaluated the effect of shallow rotary cultivation with vertical tines on the seed production of stands of creeping red fescue (Festuca rubra L. var. rubra). At four sites, rotary cultivation treatments (None, Low, Medium and High tine rotor speed) were applied after the harvest of the first and second seed crops, in factorial combination with the time of application of 68 kg ha 1 N fertilizer (Early fall, Late fall, and Split 1:1 early:late fall). In harvest years 2 and 3, the effect of site on seed yield per unit land area was modified by both N and rotary cultivation. In harvest year 2, seed yield at Site 1 was increased greatly by rotary cultivation, regardless of the tine rotor speed, but there was little difference among the four cultivation treatments at the other three sites. In harvest year 3, seed yield was increased with Low, Medium and High rotary cultivation to 6- to 11-fold that without rotary cultivation at Sites 1 and 2 but only to 1.4- to 2-fold at Sites 3 and 4. Seed yield response to rotary cultivation was dependent on site and year, a reflection of the physiological status of the fescue plants at each specific site. Rotary cultivation treatments may have been too detrimental to tiller growth and development for sustaining and enhancing seed yield, particularly at Sites 3 and 4 prior to harvest year 2. There was no consistent pattern of response in seed yield among the four sites to the three N treatments in either harvest year 2 or 3. Although there was a significant (P < 0.001) N rotary cultivation interaction for seed yield in harvest year 3, the pattern among cultivation treatments was generally similar for each N treatment; compared to no cultivation, the three cultivation treatments more than doubled seed yield to kg ha 1 with Early and Split N and increased it 4- to 6-fold to kg ha 1 with Late N. There is some potential for rotary cultivation, but the selected treatments were generally too aggressive in suppressing tillers. Key words: Rejuvenation of creeping red fescue, mechanical rejuvenation, rotary cultivation, power-harrowing, grass seed production Fairey, N. A. et Lefkovitch, L. P Incidence d un léger travail du sol avec des dents verticales et d un amendement azoté sur le rendement grainier de la fétuque rouge traçante. Can. J. Plant Sci. 82: Lors d une étude sur le terrain dans la région de la Rivière-de-la-Paix, dans le nord-ouest du Canada, on a évalué les effets d un léger travail du sol au moyen d un cultivateur rotatif à dents verticales sur le rendement grainier des peuplements de fétuque rouge traçante (Festuca rubra L. var. rubra). Quatre endroits ont fait l objet de divers traitements (aucun travail du sol, travail à faible vitesse, travail à vitesse moyenne, travail à vitesse élevée) après la première et la deuxième récolte de graines, dans une combinaison factorielle avec le moment où 68 kg d engrais azoté (N) par hectare ont été appliqués au sol (début de l automne, fin de l automne, et moitié début:moitié fin de l automne 1:1). La deuxième et la troisième année de récolte, l engrais azoté et le travail du sol ont modifié le rendement grainier par unité de surface. La deuxième année, le travail du sol a considérablement augmenté le rendement grainier au site 1, peu importe la vitesse du rotor, mais aux trois autres sites, les effets des quatre traitements n ont guère varié. La troisième année, le travail du sol à faible, moyenne ou haute vitesse a multiplié le rendement grainier de 6 à 11 fois, comparativement au non-travail du sol, aux sites 1 et 2, contre 1,4 à 2 fois seulement aux sites 3 et 4. La réaction du rendement grainier au travail du sol dépend de l endroit et de l année, et reflète l état physiologique du peuplement à cet endroit. Il se pourrait que le travail du sol ait trop nui à la croissance et au développement des talles pour que le rendement grainier se maintienne ou s améliore, surtout aux sites 3 et 4, avant la récolte de la deuxième année. Les auteurs n ont observé aucune tendance uniforme dans la réaction du rendement grainier aux trois amendements azotés, la deuxième et la troisième année de récolte, peu importe le site. Même s il existe une interaction significative (P < 0,001) entre l application d engrais azoté et le travail du sol au niveau du rendement grainier la troisième année, les résultats obtenus étaient sensiblement les mêmes pour tous les amendements, peu importe la méthode de travail du sol. Comparativement au non-travail du sol, les trois méthodes de travail du sol font plus que doubler le rendement grainier, à kg par hectare, avec la fertilisation au début de la saison ou moitié-moitié, et l augmentent de 4 à 6 fois, à kg par hectare, avec une fertilisation tardive. Le travail rotatif du sol présente un certain potentiel, mais les méthodes choisies entraînaient généralement une suppression trop agressive des talles. Mots clés: Rajeunissement des peuplements de fétuque rouge traçante, rajeunissement écanique, travail rotatif du sol, hersage mécanique, production de graines de graminées For creeping red fescue, the principal grass seed crop of the Peace River region, a method of periodic stand rejuvenation has evolved to maintain stand productivity over years and 709 combat the build-up of stem eyespot disease (Didymella festucae) (Elliott and Baenziger 1977; Fairey 1997). The rejuvenation process generally follows the harvest of two

2 710 CANADIAN JOURNAL OF PLANT SCIENCE consecutive seed crops. It involves plowing and/or discing the stand in the fall or subsequent spring (prior to mid-june), levelling the land with a float and a roller-packer, then allowing the plants to regenerate from rhizome buds and volunteer seedlings. At least one year with no seed harvest occurs, and sometimes the land may be sown to an annual cereal or canola crop, which may severely limit the seed yield of the fescue in the subsequent year. A less costly rejuvenation procedure, which eliminates the year without seed production would be particularly beneficial to growers. In the Peace River region, floral induction of creeping red fescue occurs in well-developed tillers in early November (Elliott 1966) and the lack of seed productivity in the year following standard rejuvenation is caused primarily by an inadequate density of inducible tillers. In other growing regions, various types of cultivation have been evaluated for the rejuvenation of grass seed crops but, as reviewed by Simon et al. (1997), beneficial effects on seed yield are not always realized. Most studies have involved severe harrowing or gapping after a seed harvest using a rotary cultivator fitted with L-shaped blades attached to a horizontal shaft, or using various types of conventional harrows/cultivators. Such practices were advocated in the United Kingdom for perennial ryegrass, meadow fescue, orchardgrass, timothy and tall fescue (Ministry of Agriculture, Fisheries and Food 1968) in order to provide more space, light and air for new tiller development; however, no reference was made to the use of this practice for red fescue, despite its noted propensity for developing a thick mat of thatch after seed harvest. Canode (1980) concluded that the removal of thatch accumulation in Kentucky bluegrass was an effective management practice in the Pacific Northwest USA for maintaining seed production as the stand ages, and reported that this could be achieved effectively by post-harvest burning. In the United Kingdom, seed yields of orchardgrass were increased by gapping by an average of 33% (272 kg ha 1 ) per year over a 3-yr period and the increase over the control became greater as the stand aged (Lambert 1963). However, gapping failed to increase seed yields of meadow fescue and generally had no affect on those of timothy (Lambert 1964). Subsequent to these trials, Bean (1978) concluded that gapping could not be adopted in the United Kingdom as a general principle for all grass seed crops drilled in rows, although species such as orchardgrass and tall fescue appeared to benefit from it in their second and subsequent harvests. In the Pacific Northwest USA, the drop in seed yield of Kentucky bluegrass with increased stand age was not prevented by any gapping treatment applied in late summer of alternate years (Evans and Canode 1971). In the year after gapping, seed yield increased with lower rates of N fertilizer. Seed weight per panicle increased and panicle numbers decreased, particularly at higher rates of N fertilizer. In the Peace River region, Fairey and Lefkovitch (1996) found that a density of only plants m 2 of creeping red fescue, in rows no wider than 40 cm, was required to optimize seed yield in each of 2 successive harvest years. In New Zealand, where the environment in the fall and much of the winter is favourable for the growth of grasses, fine fescue stands can be prevented from becoming sod-bound by an early fall application of atrazine and, if already sod-bound, can be rejuvenated for seed production by a light surface cultivation after harvest (Hare 1998). The conventional machinery utilized for reducing tiller density generally removes strips of plants from the stand, but the plants that remain are essentially undisturbed. This lack of uniformity in the reduction of tiller density may be one of the reasons for the inconsistent effects on seed yield. Stand rejuvenation with a pto-driven, vertical-tine, rotary cultivator should provide a more uniform reduction in tillers compared to that achieved with L-shaped blades that rotate on a horizontal shaft or with various types of conventional harrows and cultivators. The objective of this study was to determine the feasibility of using shallow rotary cultivation with vertical tines, applied annually in combination with the strategic application of N fertilizer, for maintaining the seed productivity of stands of creeping red fescue over several consecutive years. MATERIALS AND METHODS The study was conducted at four sites in the Peace River region of north-western Canada in the vicinity of the Beaverlodge Research Farm of Agriculture and Agri-Food Canada (55 12 N, W). Site 1 was located on the Beaverlodge Research Farm. It was a 15- to 20-yr-old stand of creeping red fescue, most probably of the cultivar Boreal, that had received no fertilizer or other management inputs for several years. The stand was sod-bound, had a dense mat of organic litter at the soil surface, and had produced seed panicles very sparingly for several years prior to the study. The other three sites (i.e., Sites 2, 3 and 4) were located in commercial fields of creeping red fescue. Each stand had been established with certified seed and the growers intention was to market the harvested crop as common seed, the predominant production practice for the region. Site 2 had been established with the cultivar Flyer and had been rejuvenated previously. Sites 3 and 4 were of the cultivar Boreal and the fields had been established in 1992 by undersowing with canola. At these two sites, the competition from the canola had precluded seed production in 1993, and the stands had been mowed and managed for a seed harvest in Each of the three growers planned to harvest at least one more seed crop in 1995 before initiating the rejuvenation of the fescue by plowing or discing (Elliott and Baenziger 1977), or rotating the field into an annual crop of grain/canola. With the exception of the experimental treatments, the production practices used at each site conformed to local recommendations for seed production of creeping red fescue (Elliott and Baenziger 1977). A split-plot factorial experiment, with three N fertilizer treatments and four rotary cultivation treatments, was used with four complete blocks at each site. The N fertilizer treatments were assigned to the main plots (4 80 m) of each block at each site according to a randomized complete block design. The rotary cultivation treatments were allocated at random to the subplots (4 20 m) within each main plot. The N fertilizer treatments were 68 kg ha 1 N applied as ammonium nitrate (34-0-0) in late-august/early-september

3 FAIREY AND LEFKOVITCH MAINTENANCE AND REJUVENATION OF RED FESCUE SEED STANDS 711 Table 1. The response variables, their units, the type of distribution and link function for transformation, and the random effects terms removed from the final GLMM analysis because of minimal/zero variance Random terms z not in final Response variable Units Distribution Link function GLMM Grass seed yield kg ha 1 Gamma Natural logarithm S B MP for harvest years 2 and 3 Grass seed yield mg panicle 1 Gamma Natural logarithm S B MP for each harvest year; S B for harvest year 2 Grass seed yield g g 1 Pseudo binomial y Logit S B MP (per unit land area or per panicle) for harvest years as a proportion of that for harvest years Panicle density n m 2 Gamma Natural logarithm S B MP for harvest years 1 and 2 Panicles for harvest years n n 1 Pseudo binomial y Logit S B MP 2+3 as a proportion of those for harvest years z S = Site; B = Blocks; MP = Main plots. y The proportion of a component to the whole. (Early N), in mid-october (Late N), or split equally between these two times (Split N). The rotary cultivation treatments were applied at a forward speed of 3 km h 1 using one pass of a 3-m wide Amazone KG30 Rotary Cultivator with an integral 50-cm-diameter packer-roller (Amazonen-Werke H. Dreyer GmbH & Co., KG-27794, Hude, Germany). The pto-driven, vertical tines of this machine were set to work at a depth of 3 5 cm. The four treatments were tine rotor speeds of 0, 145, 197, and 240 min 1 (None, Low, Medium, and High, respectively). The fertilizer applied for the Early N treatments was broadcast immediately prior to the application of the rotary cultivation treatments so that it would be incorporated into the soil. The fertilizer applied for the Late N treatments was surface broadcast. At each site, the experimental plots were delineated on a uniform area of fescue in the spring of The 1994 seed crop was harvested prior to the application of treatments to provide a base for comparing subsequent crop performance within each site, and to assess within-site uniformity. The treatments were applied initially in late August/early September of 1994, soon after the seed harvest and removal of residue of the 1994 crop. The treatments were re-applied in late August/early September of 1995, soon after the seed harvest and removal of residue of the 1995 crop. Observations were made on the 1994, 1995 and 1996 seed crops, i.e., harvest years 1, 2 and 3, respectively. Soon after the commencement of vegetative growth in the spring of each harvest year, three 200-cm 2 circular quadrats were placed at soil level along the centre line of each plot; they were positioned at 5, 10, and 15 m from either end of each 20-m-long plot and in between the two zones of each plot designated for seed harvest. After panicle emergence, fertile tillers that had grown up through the open area of each of the three quadrats within each plot were removed, counted, and used for the determination of the panicle density. At seed maturity, two 30-cm wide 10-m long strips were harvested from the central section of each 20-m-long plot. The strips were cut at a height of 8 10 cm with a rice binder from either side of the centre line of each plot (i.e., just outside the zone used for the assessment of panicle density). Each sample was placed in a cotton bag, air-dried on a storage rack outdoors for several weeks to mature the seed, and then placed in a forced-draft drier at room temperature for several days to complete the drying process. The two samples from each plot were amalgamated and the seed was threshed, cleaned and weighed. A sample of the seed was used for the determination of moisture content and seed yield was corrected to 12% moisture (fresh-weight basis). Immediately after each seed harvest at each site, the crop residue was removed with a flail-type forage harvester set to cut at a height of cm, in preparation for the application of the N fertilizer and rotary cultivation treatments. Each response variable is necessarily non-negative and a priori is unlikely to exhibit homogeneous variance, making the analysis of variance less efficient than generalized linear models (McCullagh and Nelder 1989). As the block and treatment structure for the experimental design has more than one residual term, a generalized linear mixed model (GLMM) was used for the analyses. For each response variable, a GLMM was fitted by the iterative re-weighted residual maximum likelihood (IRREML) method utilizing the IRREML procedure of Keen and Engel (1998) in association with Genstat 5 Release 4.1 (Lawes Agricultural Trust 1997). For the analysis of each response variable, the guidelines of Lefkovitch (1993) were used to select an appropriate error distribution and link function for transformation (Table 1). The fixed effect terms incorporated into the model were site, N fertilizer and rotary cultivation, and their interactions. The random effect terms incorporated initially into the model were site blocks, site blocks main plots, and the remaining residual. The most parsimonious model was developed for each response variable by the removal of

4 712 CANADIAN JOURNAL OF PLANT SCIENCE Table 2. Monthly precipitation (mm) at Beaverlodge during the years of the study and the long-term monthly means for Year Long-term Month mean January February March April May June July August September October November December Total annual the random effect term(s) that the GLMM procedure identified as having zero or negligible variance (Table 1). The statistical significance of each fixed effect was determined using the F-test on the Wald statistic (Elston 1998) and a probability of 0.05 was deemed significant. RESULTS AND DISCUSSION A summary of precipitation during the study (Table 2) indicates that each year was wetter than average (136, 114 and 119% of the total, annual, long-term mean for 1994 to 1996, respectively), and that the monthly receipt of precipitation varied greatly. The main effects of site, N fertilizer and rotary cultivation, and the statistical significance of their interactions, are summarized for each of the 3 harvest years for seed yield per unit land area (Table 3), panicle density (Table 4), seed yield per panicle (Table 5), and for the proportion of seed and panicles produced during harvest years (i.e., subsequent to the initial application of the N fertilizer and rotary cultivation treatments that occurred immediately after the first year harvest in 1994) relative to the respective totals over all three harvest years (i.e., 1994 to 1996, inclusive) (Table 6). The nature of each statistically significant (P 0.05) two-way interaction is presented for the Site Rotary cultivation interaction for the seed yield and panicle response variables (Fig. 1), for the Site N interaction for seed yield per unit land area in harvest years 2 and 3 (Fig. 2), and for the N Rotary cultivation interaction for the seed yield and panicle response variables (Fig. 3). The results for harvest year 1 (1994) are an indication of crop performance prior to the application of the experimental treatments. They illustrate the degree of uniformity among the individual plots at the trial sites. In a perennial seed crop such as creeping red fescue, seed productivity in any year is not only affected by prevailing environmental conditions but also by the condition and performance of the Table 3. The effects of site, N fertilizer, rotary cultivation and year of harvest on the seed yield (kg ha 1 ) of creeping red fescue Harvest year 1 (1994) Harvest year 2 (1995) Harvest year 3 (1996) Back- Back- Back- Transformed transformed Transformed transformed Transformed transformed Factor mean z mean y mean mean mean mean Site (S) SED x F-probability and significance *** *** NS N fertilizer Early Split Late SED x F-probability and significance NS *** *** Rotary cultivation (C) None Low Medium High SED x F-probability and significance NS * *** Interaction F-probability and significance S N NS *** * S C NS *** *** N C NS NS *** S N C NS NS NS z On the scale used for the link function of each response variable (see Table 1). y On the original scale of the response variable. x SED, standard error of the difference among transformed means. *, **, *** Statistically significant at P 0.05, P 0.01, and P 0.001, respectively; NS, not signficant.

5 FAIREY AND LEFKOVITCH MAINTENANCE AND REJUVENATION OF RED FESCUE SEED STANDS 713 Table 4. The effects of site, N fertilizer, rotary cultivation and year of harvest on the panicle density (n m 2 ) of creeping red fescue Harvest year 1 (1994) Harvest year 2 (1995) Harvest year 3 (1996) Back- Back- Back- Transformed transformed Transformed transformed Transformed transformed Factor mean z mean y mean mean mean mean Site (S) SED x F-probability and significance *** *** ** N fertilizer Early Split Late SED x F-probability and significance NS NS * Rotary cultivation (C) None Low Medium High SED x F-probability and significance NS NS *** Interaction F-probability and significance S N NS NS NS S C * *** * N C NS * NS S N C NS * NS z On the scale used for the link function of each response variable (see Table 1). y On the original scale of the response variable. x SED, standard error of the difference among transformed means. *, **, *** Statistically significant at P 0.05, P 0.01, and P 0.001, respectively; NS, not signficant. crop in previous years. Therefore, the results for harvest year 1 provide a benchmark to which crop performance in subsequent years can be compared. As could be anticipated, Site was the only factor for which major significant effects on seed yield were detected for harvest year 1 (Table 3) although the Site Rotary cultivation interaction was significant for panicle density (P = 0.023, Table 4 and Fig. 1c) and seed yield per panicle (P = 0.011, Table 5 and Fig. 1f). These significant interaction effects are possibly a consequence of the zero yield and panicle density for each of the four rotary cultivation treatments at Site 1; the old stand of creeping red fescue at this site was almost totally vegetative, so no assessment of seed productivity was possible. However, the inclusion of the stand at Site 1 provided an opportunity to assess the potential of the separate and combined effects of N fertilization and rotary cultivation for rejuvenating an old, vegetative, stand of creeping red fescue for the production of common seed, without resorting to the conventional practices that involve plowing and multiple passes with other equipment (Elliott and Baenziger 1977). In harvest years 2 and 3, the effect of Site on seed yield per unit land area was modified by both the N and Rotary cultivation treatment factors (Table 3, Fig. 1a and b and 2a and b). In harvest year 2, compared to no cultivation, seed yield was increased 5- to 7-fold by cultivation at Site 1, decreased by about 50% with cultivation at Site 3, and was unaffected by cultivation at Sites 2 and 4 (Fig. 1a). In harvest year 3, seed yield was increased with Low, Medium and High rotary cultivation to 6- to 11-fold that without rotary cultivation at Sites 1 and 2 but only to 1.4- to 2-fold at Sites 3 and 4 (Fig. 1b). Thus, the seed yield response to the rotary cultivation appears to be dependent on the site and year; this is presumably a reflection of the physiological status of the fescue plants at each specific site. The rotary cultivation treatments may have been overly effective in suppressing the growth and development of reproductive tillers, particularly at Sites 3 and 4 prior to harvest year 2. There was no consistent pattern of response in seed yield among the four sites to the three N treatments in either harvest year 2 or 3 (Fig. 2a and b). Although there was a significant (P < 0.001) N rotary cultivation interaction for seed yield in harvest year 3 (Table 3), the yield response to cultivation was positive for each of the three N treatments (Fig. 3a); compared to no cultivation, the three cultivation treatments more than doubled seed yield to kg ha 1 with Early and Split N and increased it 4- to 6-fold to kg ha 1 with Late N. A high incidence of variability among sites and years was also found in a previous N fertility study on seed production of creeping red fescue in the Peace River region (Fairey and Lefkovitch 2000). That study included six trials that were initiated over a 4-yr period. The mean seed yield of these six trials varied from 142 to 1240 kg ha 1 and the overall mean seed yield was 566 kg ha 1. This diverse set of trials revealed no significant effects of the time (late fall, early and late spring) or method (surface-broadcast granular, foliar/soil spray, and soil-

6 714 CANADIAN JOURNAL OF PLANT SCIENCE Table 5. The effects of site, N fertilizer, rotary cultivation and year of harvest on the seed yield (mg panicle 1 ) of creeping red fescue Harvest year 1 (1994) Harvest year 2 (1995) Harvest year 3 (1996) Back- Back- Back- Transformed transformed Transformed transformed Transformed transformed Factor mean z mean y mean mean mean mean Site (S) SED x F-probability and significance *** *** *** N fertilizer Early Split Late SED x F-probability and significance NS NS ** Rotary cultivation (C) None Low Medium High SED x F-probability and significance NS ** *** Interaction F-probability and significance S N NS NS NS S C * * * N C * * NS S N C NS ** NS z On the scale used for the link function of each response variable (see Table 1). y On the original scale of the response variable. x SED, standard error of the difference among transformed means. *, **, *** Statistically significant at P 0.05, P 0.01, and P 0.001, respectively; NS, not signficant. injected) of N application on seed yield. The present results are a further indication of the insensitivity of the reproductive growth of creeping red fescue in the study region to markedly different strategies of N application. In harvest year 1, prior to the application of the N and rotary cultivation treatments, panicle density differed markedly among sites and was not consistent among the plots that eventually received the different cultivation treatments (Table 4, Fig. 1c); the significant (P = 0.023) Site Rotary cultivation interaction is associated with the zero panicle density for each cultivation treatment at Site 1, together with the inherent variation in the spatial distribution of plants and panicles in the plots. It is an indication that the number and/or area of the sampling quadrats 200 cm 2 ) for the determination of panicle density may have been inadequate in relation to the prevailing variability within the plots at each site. The same interaction was evident in harvest year 2, subsequent to treatment application, but the degree of significance was far greater (P = <0.001) (Table 4); when compared to no cultivation, panicle density increased 2- to 3-fold with cultivation at Site 1, was reduced by about 50% with cultivation at Sites 2 and 3, and was very low and unaffected by cultivation at Site 4 (Fig. 1d). Furthermore, there was a significant (P = 0.019) Site N Rotary cultivation interaction in harvest year 2 (Table 4) when Late N tended to reduce panicle density to a greater extent, and more consistently among sites, than Early or Split N as the intensity of cultivation increased (Table 7). In harvest year 3, there was a Site Rotary cultivation interaction for panicle density (P = 0.032; Table 4) that revealed an increased density with the Low, Medium and High cultivation treatments, compared to None, at Sites 1 and 2 but little effect at the other two sites (Fig. 1e). There was also a greater panicle density with Split N compared to either the Early or Late N treatments (Table 4). With respect to the seed yield of individual panicles (Table 5), there was a significant Site Rotary cultivation interaction (P 0.05) in each harvest year (Fig. 1f, g, h), a significant N Rotary cultivation interaction (P 0.05) in harvest years 1 and 2 (Fig. 3d, e), and a significant Site N Rotary cultivation interaction (P = 0.007) in harvest year 2 (Table 8). This three-way interaction is presumably directly related to the one mentioned above for panicle density but a meaningful agronomic interpretation is not apparent. It is helpful, therefore, to consider the seed yield per panicle for each consecutive harvest year for the main effects of N and rotary cultivation (Table 5). In the first harvest year, no significant differences were expected or revealed among the treatments of either main effect. In harvest year 2, there was no significant difference among the N treatments but the Low, Medium and High rotary cultivation treatments produced 1.4 to 2-fold as much seed per panicle as the no-cultivation treatment. In harvest year 3, the Early N produced 1.4-fold as much seed per panicle as either Split or Late N,

7 FAIREY AND LEFKOVITCH MAINTENANCE AND REJUVENATION OF RED FESCUE SEED STANDS 715 Table 6. The effects of site, N fertilizer and rotary cultivation on the proportion (%) of seed and panicles of creeping red fescue produced during the harvest years relative to the respective totals over all three harvest years (i.e., total for as a percentage of the total for ) Seed yield per unit land area Seed yield per panicle Panicle density Back- Back- Back- Transformed transformed Transformed transformed Transformed transformed Factor mean z mean y mean mean mean mean Site (S) SED x F-probability and significance *** ** *** N fertilizer Early Split Late SED x F-probability and significance *** ** * Rotary cultivation (C) None Low Medium High SED x F-probability and significance *** *** NS Interaction F-probability and significance S N NS NS NS S C *** NS * N C NS ** ** S N C NS NS NS z On the scale used for the link function of each response variable (see Table 1). y On the original scale of the response variable. x SED, standard error of the difference among transformed means. *, **, *** Statistically significant at P 0.05, P 0.01, and P 0.001, respectively; NS, not signficant. and the Low, Medium and High rotary cultivation treatments produced fold as much seed per panicle as the no-cultivation treatment, with the amount increasing as the intensity of the cultivation increased (Table 5). A similar increase from rotary cultivation, to 165% of the control, was observed in the seed yield of individual panicles of creeping red fescue in another trial in the study region, but panicle density was decreased such that seed yield per unit land area was not increased (Fairey and Lefkovitch 2001). Similarly, in the Pacific Northwest USA, the drop in seed yield of Kentucky bluegrass with increased stand age was not prevented by gapping the stand in alternate years although seed yield was increased at lower rates of N fertilizer, seed weight per panicle was increased, and panicle numbers were reduced particularly at higher rates of N fertilizer (Evans and Canode 1971). A comparison of the performance characteristics before and after the application of the N and rotary cultivation treatments (Table 6) revealed that seed yield per unit land area was dependent on the N treatment and the interaction of site with rotary cultivation (Fig. 1j), that seed yield per panicle was dependent on the site and the interaction of N and rotary cultivation (Fig. 3f), and that panicle density was dependent on the interaction of site and rotary cultivation (Fig. 1i) and of N and rotary cultivation (3c). In general, the responses involving the three N treatments are of insufficient consistency and magnitude to be of agronomic significance. The interactions of rotary cultivation with site are, to a large extent, related to the contrasting nature of Site 1 at the commencement of this study, i.e., an old stand that had become totally vegetative and with a dense layer of thatch. Some agronomically meaningful responses in panicle and seed productivity were realized with the application of the rotary cultivation treatments, particularly at Site 1 in harvest year 2 and at each of the four sites in harvest year 3. At Sites 2, 3 and 4, productivity responses were not consistent over years like those at Site 1. The results indicate that rotary cultivation with vertical tines has some potential for rejuvenating seed stands of creeping red fescue. However, the rotary cultivation treatments selected for this study generally resulted in too low a density of reproductive tillers for optimizing seed yield. Future research should focus on less aggressive tine action (e.g., slower rotation speed), bi-annual rather than annual application, and on the timing of the application (possibly delaying the treatment until spring when floral induction has been completed). Such modifications might increase the consistency of the beneficial effects on the growth and development of reproductive tillers of creeping red fescue. In the northerly latitude of the study region, burning, the principal non-mechanical option of rejuvenating stands of creeping red fescue, is overly detri-

8 716 CANADIAN JOURNAL OF PLANT SCIENCE Fig. 1. The interaction of site and rotary cultivation on some seed production characteristics of creeping red fescue. SED a, SED b and SED c are the standard errors of the differences among any two transformed means, among transformed means at the same level of the site and at the same level of the cultivation, respectively. Note that the secondary y-axis is the scale for the transformed values.

9 FAIREY AND LEFKOVITCH MAINTENANCE AND REJUVENATION OF RED FESCUE SEED STANDS 717 Fig. 2. The interaction of site and N fertilizer on seed yield per unit land area of creeping red fescue for harvest years 2 and 3 (1995 and 1996). SED a, SED b and SED c are the standard errors of the differences among any two transformed means, among transformed means at the same level of the site and at the same level of the cultivation, respectively. Note that the secondary y-axis is the scale for the transformed values. Fig. 3. The interaction of N fertilizer and rotary cultivation on some seed production characteristics of creeping red fescue. SED a, SED b and SED c are the standard errors of the differences among any two transformed means, among transformed means at the same level of the N and at the same level of the cultivation, respectively. Note that the secondary iy-axis is the scale for the transformed values.

10 718 CANADIAN JOURNAL OF PLANT SCIENCE Table 7. The site N cultivation treatment interaction in harvest year 2 (1995) for the panicle density (n m 2 ) of creeping red fescue Cultivation treatment None Low Medium High Back- Back- Back- Back- Nitrogen Transformed transformed Transformed transformed Transformed transformed Transformed transformed Site treatment mean z mean y mean mean mean mean mean mean 1 Early N Split N Late N Early N Split N Late N Early N Split N Late N Early N Split N Late N Standard error of the difference (SED) between transformed means = SED for the same level of site factor = SED for the same level of nitrogen factor = SED for the same level of cultivation factor = z On the scale used for the link function of the response variable (see Table 1). y On the original scale of the response variable. Table 8. The site N cultivation treatment interaction in harvest year 2 (1995) for the seed yield (mg panicle 1 ) of creeping red fescue Cultivation treatment None Low Medium High Back- Back- Back- Back- Nitrogen Transformed transformed Transformed transformed Transformed transformed Transformed transformed Site treatment mean z mean y mean mean mean mean mean mean 1 Early N Split N Late N Early N Split N Late N Early N Split N Late N Early N Split N Late N Standard error of the difference (SED) between transformed means = SED for the same level of site factor = SED for the same level of nitrogen factor = SED for the same level of cultivation factor = z On the scale used for the link function of the response variable (see Table 1). y On the original scale of the response variable. mental to seed yield because there is insufficient time, between seed harvest and the onset of winter, for the formation and growth of an optimum density of inducible tillers (Fairey and Lefkovitch 2001). CONCLUSIONS 1. Shallow rotary cultivation with vertical tines can stimulate panicle production and seed productivity in creeping red fescue, particularly in stands that have become highly vegetative. 2. There were no consistent advantages or disadvantages for seed productivity of creeping red fescue from an early fall, a late fall or a split application of N fertilizer; the responses varied with site, year, and the nature of the rotary cultivation treatment. 3. Shallow rotary cultivation with vertical tines should be compared directly to current practices (involving plowing, discing, floating, rolling and packing) of stand rejuvenation for seed stands of creeping red fescue, both from an agronomic and an economic viewpoint. More research is required to determine the most appropriate timing, frequency and aggressiveness of the procedure for stimulating reproductive tiller production in creeping red fescue.

11 FAIREY AND LEFKOVITCH MAINTENANCE AND REJUVENATION OF RED FESCUE SEED STANDS 719 ACKNOWLEDGEMENTS The technical assistance of Lois Connelly, Tom Cramer, Marlene Probst, and Lia Scheunhage is gratefully acknowledged, as is the provision of the field sites by Tom Adams, William Jones, and by Melvin and Wayne Longson. Bean, E. W Seed crop management general principles. Pages (Chapter 3) in Principles of herbage seed production. 2nd ed. Welsh Plant Breeding Station, Aberystwyth, UK. Canode, C. L Grass-seed production in the Intermountain Pacific North-west USA. Pages (Chapter 13) in P. D. Hebblethwaite, ed. Seed production. Butterworths, London, UK. Elliott, C. R Floral induction and initiation in three perennial grasses. Ph.D. thesis, University of Saskatchewan, Saskatoon, SK. 90 pp. Diss. Abstr. 27(6): 1686-B. Elliott, C. R. and Baenziger, H Creeping red fescue. Rev. ed. Agriculture Canada, Ottawa, ON. Publ. 1122, 19 pp. Elston, D. A Estimation of denominator degrees of freedom of F-distributions for assessing Wald statistics for fixed-effect factors in unbalanced mixed models. Biometrics 54: Evans, D. W. and Canode, C. L Influence of nitrogen fertilization, gapping, and burning on seed production of Newport Kentucky bluegrass. Agron. J. 63: Fairey, N. A Festuca rubra L. (creeping red fescue) in Canada. Pages in D. T. Fairey and J. G. Hampton, eds. Forage seed production. Volume 1. Temperate species. CAB International, Oxford, UK. Fairey, N. A. and Lefkovitch, L. P Crop density and seed production of creeping red fescue (Festuca rubra L. var. rubra). 1. Yield and plant development. Can. J. Plant Sci. 76: Fairey, N. A. and Lefkovitch, L. P Effects of method and time of application of nitrogen fertiliser on yield and quality of seed of creeping red fescue. Can. J. Plant Sci. 80: Fairey, N. A. and Lefkovitch, L. P Effect of post-harvest management on seed production of creeping red fescue, tall fescue, and Kentucky bluegrass in the Peace River region of north-western Canada. Can. J. Plant Sci. 81: Hare, M. D Fine fescue. Pages in J. Rowarth, ed. Practical herbage seedcrop management. Lincoln University Press, Canterbury, New Zealand. Keen, A. and Engel, B Procedure IRREML in P. W. Goedhart and J. T. N. M. Thissen, eds. CBW Genstat Procedure Library Manual Release 4[1], Centre for Biometry Wageningen (CBW) Wageningen, The Netherlands. Lambert, D. A The influence of density and nitrogen in seed production stands of S37 cocksfoot (Dactylis glomerata L.). J. Agric. Sci. (Camb.) 61: Lambert, D. A The influence of density and nitrogen in seed production stands of S48 timothy (Phleum pratense L.) and S215 meadow fescue (Festuca pratensis L.). J. Agric. Sci. (Camb.) 63: Lawes Agricultural Trust Genstat 5 Release 4.1 Command Language Manual. Genstat 5 Committee, Statistics Dept., IARC-Rothamsted, Harpenden, Hertfordshire, UK. Numerical Algorithms Group Ltd., Oxford, UK. 384 pp. Lefkovitch, L. P Some fundamental concepts in planning and analysing field experiments. J. Appl. Seed Prod. 11: McCullagh, P. and Nelder, J. A Generalized linear models. 2nd ed. Chapman and Hall, London, UK. Section Ministry of Agriculture, Fisheries and Food Growing the crop. Pages in R. Ede, ed. Grass and clover crops for seed. Bulletin No. 204, Her Majesty s Stationery Office, London, UK. Simon, U., Hare, M. D., Kjaersgaard, B., Clifford, P. T. P., Hampton, J. G. and Hill, M. J Harvest and postharvest management of forage seed crops. Pages in D. T. Fairey and J. G. Hampton, eds. Forage seed production. Volume 1. Temperate species. CAB International, Oxford, UK.

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