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Sheep farmers can increase production levels as a means to improve economic outcomes. However, this intensification can potentially result in more nitrogen (N) leaching which is at odds with the increasing pressure on farmers to reduce the quantity of N lost into the environment. Therefore, there is increasing interest in the use of alternative forages, such as Italian ryegrass and plantain, which could potentially allow farmers to increase production while decreasing N leaching. This study quantified and compared the quantity of N leaching under sheep grazing four different forages: perennial ryegrass/white clover (RGWC), Italian ryegrass/WC (IRWC), plantain/WC (PWC) and a winter brassica. Five replicates of each forage were established on plots of 800 m2 (40 m x 20 m). Each plot had an independent mole-pipe drain system with tipping-bucket monitoring equipment at the end of the pipe drain. Drainage volume and N concentrations (nitrate-N: NO 3 ⁻-N; ammonium-N; total-N) in drainage water were measured to estimate N losses. The forages were grazed according to the best management practice for each forage type over a two-and-a-half-year period (Year 1: July-December 2019; Year 2: January-December 2020; and Year 3: January-December 2021). In the first two years of this study, NO 3 ⁻-N leaching losses under IRWC and PWC were very small (ranging from 0.4 to 0.5 kg N/ha), and they were not different (P > 0.05) from those under RGWC. However, in Year 3, the leaching losses under IRWC and PWC treatments were greater (P < 0.05) than those under RGWC. This increased leaching was probably due to the need to re-establish these pastures. As part of renewing these swards, the IRWC and PWC plots were fallow during the key late summer-autumn period. In contrast, NO 3 ⁻-N leaching losses under brassica forages (3.5–6.4 kg N/ha) were greater (P < 0.05) than under RGWC (0.5–1.5 kg N/ha). Overall, the leaching losses measured under sheep grazing the forages were much smaller than those commonly reported by dairy studies. [Display omitted] • In recent years, there has been significant concern regarding the leaching of nutrients from grazing systems. • This study quantified the amount of nitrogen leaching lost in drainage water from sheep grazing four different forages. • Mole-and-pipe drainage systems were used to monitor drainage volume and collect samples. • Overall, leaching losses under sheep grazing forages were small. • Modern sheep grazing systems may offer mitigation options for dairying areas with high NO 3 - leaching. [ABSTRACT FROM AUTHOR]

In dairy systems, grass–clover swards are fertilized with on–farm cattle slurry as a basic dressing and often supplemented with mineral fertilizer throughout the season. Uncertainty remains on consequences for N input from atmospheric N 2 -fixation by grassland legumes. The aim of this study was to examine the N response of slurry versus mineral N fertilization on clover dynamics, the proportion of N derived from the atmosphere (%Ndfa) and the quantitative N 2 -fixation (qBNF) using the 15N isotope dilution method. This was done in an on farm setting at two sites in two years with increasing rates of N fertilizer (0–480 kg available N ha-1) either of mineral N only or combined with application of cattle slurry. The leys were at one site composed a 2–species mixture of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.) and at the other site of a 4–species mixture of white clover, red clover (Trifolium pretense L.), festulolium (Festulolium braunii) and ryegrass. Species dynamics were significantly affected by fertilizer rate in the 2–species sward and by fertilizer rate and type in the 4–species sward. Reduction of the clover proportion in response to fertilization was due to a clover yield decrease (2–species sward) or a grass yield increase (4–species sward). In the 4–species sward, in treatments with mineral N only %Ndfa decreased markedly with N rate, whereas the corresponding slurry + mineral N treatments did not. Thus, apart from fertilization with mineral N only at one site the general picture was a relatively high (>80%) %Ndfa over the season when the N level was below 200–300 kg available N ha-1. The qBNF of the harvested biomass in sward without fertilization reached 193–216 kg N ha-1 in the 2–species sward and 203–286 kg N ha-1 in the 4–species sward. Clover persisted at high fertilization rates, but qBNF was reduced to 16–79 kg N ha-1 and 58–163 kg N ha-1 in 2– and 4–species swards, respectively. Interestingly, in the 4–species sward amended with slurry + mineral N, qBNF was high and independent of fertilization rate. We conclude that response of clover dynamics to N fertilization differed with fertilizer type and level – slurry have lower effect whereas the effect of mineral N only on N 2 -fixation is less predictable. • N response of grass–clover leys was investigated as affected by mineral N or slurry. • Dry matter yield and grass fraction increased as expected with N level. • Leys at two sites showed two patterns of N 2 -fixation activity response to fertilizer type. • Slurry in combination with mineral N sustained high N 2 -fixation until 240 kg N ha-1. • Clover N 2 -fixation response to mineral N only was less predictable among sites. [ABSTRACT FROM AUTHOR]

• Temporal stability of forage provision was assessed in white clover mixtures. • Mixture partner effects on yield and quality stability were site-dependent. • Stability benefited from adding chicory to mixtures in years with low precipitation. • Clover populations affected stability independently of the mixture partner. Clover-based crop stands are gaining importance in temporary grasslands for intensive livestock production. However, knowledge of their optimal composition to achieve high temporal stability of forage provision is insufficient, particularly so for long cultivation periods. A five-year field trial was conducted to study the effect of adding a non-leguminous forb to clover-based crop stands and to evaluate the impact of the clover variety on inter- and intra-annual stability of forage yield and quality. At two contrasting sites, we cultivated eight white clover (Trifolium repens) populations in pure stands and in mixtures with perennial ryegrass (Lolium perenne) and/or chicory (Cichorium intybus) under a four-cut system without fertilization and determined the seasonal and annual forage yield and quality. Temporal stability of forage provision differed between crop stand types, with marked differences between years and cropping sites. In the study years with lower than long-term precipitation, adding chicory enhanced temporal stability of forage yield as compared to white clover pure stands or clover-grass mixtures at least at the site with deep soil, and maintained or enhanced that of forage quality as compared to clover-grass mixtures. This was often reversed in the study years with higher than long-term precipitation. The white clover populations only slightly varied in temporal stability of forage provision, and did so independently of the crop stand type. Our findings highlight the potential but also constraints of including a non-leguminous forb in unfertilized mown clover-based crop stands, as well as of decisions on the clover variety, to improve temporal stability of forage provision. [ABSTRACT FROM AUTHOR]

Abstract: The genetic implications and economics of regenerating forage species in different environments was studied in a multi-site field experiment. Two accessions of perennial ryegrass (Lolium perenne L.) and two accessions of white clover (Trifolium repens L.) from germplasm collections of the United Kingdom (UK), Czech Republic, Norway, Portugal and Denmark were cloned and planted in regeneration plots, each comprising 49 plants, at sites in the UK, Denmark, Czech Republic and Portugal. Inflorescence emergence date and seed yield of each plant within the plot was measured. G×E effects were quantified. Inflorescences of accessions of both species emerged earlier but with a greater spread in Portugal than in the other countries. Plants also exhibited significant variation in inflorescence emergence which was generally less in L. perenne than in T. repens apart from in Portugal where variation in T. repens was less than in L. perenne. Plant survival of L. perenne in Portugal was less than at the other sites in contrast to T. repens where there were few differences in survival between sites. The proportion of plants contributing to seed yield varied between sites and accessions. In L. perenne, seed yield was greatest in Denmark and lowest in Portugal but for T. repens, seed yield was greatest in the UK and lowest in Denmark; however, accessions differed in their sensitivity to site of multiplication due to differential response of plants to environment. The cost of regeneration in Portugal was 50% of the other sites but cost per gram of seed produced was lowest in Denmark (for L. perenne) and in Portugal (for T. repens). Regeneration costs as well as the sensitivity of accessions of forage grasses and legumes to environment during regeneration are therefore important when appropriate sites for regeneration are being considered. [Copyright &y& Elsevier]

Using data from a decomposition study, we aimed to test the parameterisation of the soil organic matter module of the DAISY model, and link measurable plant litter fractions (lignin, water-soluble) with the model defined plant litter pools. Shoot and root material from perennial ryegrass and white clover was incubated in a sandy loam soil at 9 °C for 94 days. Accumulated CO2 evolution, soil mineral nitrogen (N) and soil microbial biomass-N were measured during the incubation. Marked differences in decomposition rates between above- and below-ground material as well as between the two plant species were observed. The DAISY model was used to interpret the incubation results. Decomposition rates and utilisation efficiencies were modified, under the constraint that rates of specific pools were independent of the type of material, to obtain good agreement between observed and simulated values. Measurable quality parameters were evaluated against the sizes of pools in the model and measured fluxes. The size of the slowest decomposing fraction of the DAISY model was proportional to the lignin content of the plant material, but twice as large. The easily decomposable fraction in the model was well correlated with the water-soluble fraction of the plant material (r2=0.84). The size of this pool in the model was larger than the water-soluble fraction of the plant material in three of the five plant materials. The initial carbon mineralisation was correlated with water-solubility of the plant material and total mineralisation with the lignin:N ratio. Net N mineralisation was well correlated with the C:N ratio and the N content of the added material. At the end of the experiment, the mineral N content was overestimated by the DAISY model for all treatments, except one. A soil microbial residual pool, consisting of undecomposed microbial tissue is suggested as a possible N-sink during the incubation. The study demonstrated a correlation between the model-defined pools and chemical plant fractions, but also that the pools in the model were larger than their measured counterparts. [Copyright &y& Elsevier]