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Limited information is available on frequency and seasonal timing of irrigation in perennial ryegrass seed crops. Two field experiments were conducted in Oregon to investigate irrigation effects on seed production in seven cultivars of perennial ryegrass. Three spring irrigation treatments were tested in Experiment 1 over a two-year period: none (control), single irrigation to fill the soil profile to field capacity (FC) at anthesis, and multiple irrigations to maintain soil water deficit ≤50 mm below FC until the beginning of seed fill; and single fall and spring irrigation timings were tested in Experiment 2 over a three-year period. Spring irrigation increased seed yield of perennial ryegrass in both experiments while fall irrigation had no effect in the second experiment. A single spring irrigation increased seed yield by an average 16.1% whereas multiple irrigations resulted in an average increased yield of 24.6% in Experiment 1. Single spring irrigation in Experiment 2 increased seed yield by an average 6.5%. Seed yield increases attributable to spring irrigation were the result of a combination of increased seed number and seed weight. Spring irrigation increased harvest index and seed set. Water use efficiency was reduced by spring and fall irrigation. Perennial ryegrass seed crops can benefit from spring irrigation but the frequency of irrigation is best determined by the quantity of water available and economic considerations. [ABSTRACT FROM AUTHOR]

Highlights: [•] Application of trinexapac-ethyl plant growth regulator reduced stem length and controlled lodging in perennial ryegrass across nine diverse lodging environments. [•] Trinexapac-ethyl consistently increased seed yield and harvest index in perennial ryegrass. [•] Timing trinexapac-ethyl applications between BBCH stages 32 and 51 produced the best seed yield results. [•] Seed yield increases resulting from trinexapac-ethyl application were attributable to a greater number of seeds spikelet−1 and improvements in seed set. [Copyright &y& Elsevier]

Abstract: Forage grass seed yields are often low and variable with only 10–20% of the above ground matter harvested as seed. Seed yield is affected by the amount of carbohydrate transported to the seed. However, information regarding the storage and mobilisation of carbohydrates during reproductive development in forage grasses is limited and the contribution of stored and current assimilate to seed yield from vegetative tissues is equivocal. To identify whether the total amount of carbohydrate in the plant might be limiting seed yield, and the contribution of vegetative and reproductive tissues to seed yield, the pattern of accumulation of water-soluble carbohydrates (WSC) and their remobilisation was investigated in field-grown perennial ryegrass (Lolium perenne L.) plants. Tillers were sampled from early head emergence through to harvest. Amounts of WSC in leaf blades, leaf sheaths, internodes and reproductive heads of the tillers were measured in two ways. Firstly, WSC were estimated indirectly by changes in tissue dry weight. These changes were then used to determine any apparent translocation of WSC from vegetative tissues to the developing seed. Secondly, WSC concentration was measured directly. Low molecular weight (LMW) and high molecular-weight (HMW) WSC were extracted from vegetative and reproductive tissues and the concentrations quantified using a colorimetric anthrone assay. The seed yield of the crop was high (2950kgh−1) and the dry weights and the amount of LMW and HMW WSC in vegetative and reproductive tissues changed significantly during reproductive development. High concentrations of HMW WSC were found in the internodes post head emergence and these concentrations continued to increase during seed fill through to harvest. Total dry weight of the internodes also increased over the same period. In contrast, in the leaf blades and leaf sheaths, total dry weight decreased only slightly while the initial low concentrations of WSC steadily declined. In the heads, WSC increased significantly during seed fill and subsequently declined while the dry weight continued to increase through to harvest. The ratio of LMW and HMW WSC also changed during development depending on the tissue type and growth stage. The present study indicates that the seed head itself maybe an important factor driving seed fill. Knowledge of the mechanisms that underlie carbohydrate partitioning to the seed could in future result in significantly higher yields. [Copyright &y& Elsevier]

Abstract: Perennial ryegrass (Lolium perenne L.) was grown for seed in field trials in order to investigate the temporal variation in plant nitrogen (N) concentration during ontogeny. Crops were sown in three successive years and grown with five N fertiliser rates applied in the autumn and in the spring (autumn–spring): 0–0, 0–50, 0–100, 30–120 or 60–140kg Nha-1. Within each N fertiliser rate, N concentration in the plants increased from the initiation of spring growth and reached a maximum of 4.8% at 450–500 growing degree-days (GDD) after which it decreased to 0.8% at 1150–1200 GDD. This pattern of plant N concentration was consistently low at each N fertiliser rate and between years whereas the variation in plant N concentration within each year was high as a result of the different N fertiliser rates. Nitrogen fertiliser rate up to 150kg Nha-1 increased the seed yields. During spring growth 89% of the variation in plant N concentration could be explained by a non-linear function of GDD. Maximum variation occurred at 480 GDD, with a 95% confidence interval between 428 GDD and 540 GDD. Plant N concentrations measured at 424 GDD in 1998, 447 GDD in 1997, and 497 GDD in 1996, and the resulting correlation coefficients (r2) between N concentration and seed yield were 0.81, 0.71 and 0.92, respectively. It is concluded that the variation in plant N concentration during ontogeny in perennial ryegrass is related to different N fertiliser rates and that the greatest variation in plant N concentration was in the period from 428 GDD to 540 GDD. [Copyright &y& Elsevier]

• Yields in variety trials showed significant genetic gains in forage maize and perennial ryegrass. • On-farm yields showed significant positive trends for forage maize, and no trend for grass. • Forage maize yields in farming practice are lower than in variety trials, and the gap is widening. Grass and forage maize are important forage crops in ruminant production systems in the temperate regions in northwest Europe. High yields of these crops contribute to farm profitability and local provision of feed, and hence local circularity of biomass and nutrients. Variety choice is an important option to raise potential and actual yields. We analysed 40 years of perennial ryegrass and 25 years of forage maize yield data from Value of Culture and Use (VCU) experiments to determine genetic and non-genetic trends of yields in time. For maize, we calculated an annual genetic trend of +173 kg DM ha−1 and a non-genetic trend of +65 kg DM ha−1. Further analysis of the non-genetic trend showed that maize yields increased with increasing temperature sum during the growing season, and with earlier sowing. The feeding value of forage maize showed a genetic trend of +1.7 feed unit milk (VEM) kg DM−1 year−1. The annual genetic gain of perennial ryegrass was +44 kg DM ha−1. In the grass trials we found opposing non-genetic trends for cutting and grazing. Further analysis of the non-genetic trend showed that drought and the number of days with ground frost during the growing season had a negative effect on yield. We compared the average yields and trends in VCU trials with those of on-farm yields. The on-farm maize yields showed an annual trend of +195 kg DM ha−1. We estimated an average realisation of the genetic gains of 75 % in farming practice, implying a widening gap between genetic potential and on-farm yields. Averaged over the entire period, on-farm maize yields were 4.6 t DM ha−1 (24%) lower than the yields of the VCU trials. The average annual on-farm grass yields did not show any trend, and were 1.6 t DM ha−1 (13%) lower than the yields of the VCU trials. In conclusion, our study revealed significant positive genetic and varying non-genetic trends in DM yields of forage maize and perennial ryegrass, the two dominant forage crops in the Netherlands. On-farm yields showed significant positive trends for forage maize, but no trend for grassland. [ABSTRACT FROM AUTHOR]