Influence of plant growth and root architecture of Italian ryegrass (Lolium multiflorum) and tall fescue (Festuca arundinacea) on N recovery during winter

Nitrate () leaching is an environmental and health concern. In grazed pasture systems, leaching primarily occurs beneath animal urine patch areas due to high nitrogen (N) loading and the inability of pasture plants to capture all of this N. This study investigated the relative importance of plant growth and root architecture to recover soil N. Herbage N recovery, dry matter (DM) yield and root architecture, following injections of ¹⁵N‐enriched urea at different soil depths (5, 25 and 45 cm), were measured for Italian ryegrass (Lolium multiflorum Lam.) and tall fescue (Festuca arundinacea Schreb.) grown in soil monolith lysimeters (18 cm diameter × 70 cm depth) under simulated South Island, New Zealand winter temperature and light levels. Total herbage N uptake and DM yield were on average 24 and 48% greater in L. multiflorum than F. arundinacea respectively. Root length density (cm cm^?3 soil) in the 5‐ to 25‐cm‐depth horizon was similar between species. In the 25‐ to 45‐cm‐depth horizon, F. arundinacea roots were found at higher densities than L. multiflorum. In the 45‐ to 65‐cm‐depth horizon, root length density was fourfold to ninefold higher for F. arundinacea than L. multiflorum, but N uptake efficiency was greater in L. multiflorum (0·48 mg ¹⁵N m^?1 root) than F. arundinacea (0·09 mg ¹⁵N m^?1 root). The results suggest that deep F. arundinacea roots are relatively inactive during the winter period and confirm that plant growth is more important than root architecture (e.g. deep roots) to recover soil N and ultimately reduce nitrate leaching losses.     

Herbage production and persistence of two tropical perennial grasses and forage sorghum under different nitrogen fertilization and defoliation regimes in a summer‐dominant rainfall environment,Australia

An experiment was conducted in inland northern New South Wales (NSW) to assess the response of tropical perennial grasses Chloris gayana (Rhodes grass) cv. Katambora and Digitaria eriantha (digit grass) cv. Premier and annual forage sorghum (Sorghum bicolor ssp. bicolor × S. bicolor ssp. drummondii hybrid) cv. Sweet Jumbo fertilized with five rates of nitrogen (N; 0, 50, 100, 150 and 300 kg N ha^?1) and defoliated every 2 or 6 weeks over two growing seasons. Tropical perennial grasses were highly responsive to N fertilizer, while there was no significant response by forage sorghum. Herbage production of Rhodes grass increased linearly whereas digit grass had a high response at 50–100 kg N ha^?1. Nitrogen‐use efficiency was highest during the growing season when rainfall was higher. During this season, digit grass had the highest N efficiency (148 kg DM kg^?1 N applied) at 50 kg N ha^?1, and Rhodes grass (66 kg DM kg^?1 N applied) at 100 kg N ha^?1. Plant frequency of both perennial species increased and then stabilized at high levels (>84%, cell size 0·1 by 0·1 m) during the two growing seasons. Plant frequency of Rhodes grass declined over the winter period, but recovered within 6 weeks of commencement of the growing season. Soil nitrate levels indicated that unused nitrate moved down the soil profile during wet winters. Implications of leaching below the rooting zone are discussed.     

Production and nutritional value of sorghum and black oat forages under nitrogen fertilization

The effect of nitrogen (N) fertilization on the dry‐matter (DM) yield and nutritional value of sorghum (Sorghum sp., cv. Jumbo) and black oat (Avena strigosa cv., IPR 61) was investigated in the context of forage and livestock production in southern Brazil. Sorghum was cultivated with 0, 37·5, 75, 150, 225, 300 and 375 kg N ha^?1 during the summer crop seasons of 2010/11 and 2011/12. Black oat received 0, 40, 80, 120, 160, 200 and 240 kg N ha^?1 in the winter of 2011. According to the adjusted polynomial regression, sorghum DM yield increased in response to N up to 288 (12·9 t ha^?1) and 264 kg ha^?1 (5·6 t ha^?1) in 2010/11 and 2011/12 respectively. Crude protein (CP) content of sorghum was highest at 349 and 328 kg N ha^?1, but in vitro dry‐matter digestibility (IVDMD) was highest at 212–207 kg N ha^?1 in 2010/11 and 2011/12 respectively. Sorghum neutral detergent fibre (NDF) and acid detergent fibre (ADF) were not affected by N fertilization. In black oat, the maximum DM yield (6·0 t ha^?1) was obtained with 187 kg N ha^?1; the IVDMD, NDF and ADF were not affected by N fertilization, but the CP content increased up to 220 kg N ha^?1. It is concluded that these forage species can improve the year‐to‐year amount and quality of forage produced but high rates of N fertilizer are required to achieve high yields. Fertilizer N rates of 210–280 kg N ha^?1 in sorghum and 180 kg N ha^?1 in black oat in the crop rotation provide the greatest responses in DM yield consistent with good nutritional quality for livestock production.     

Bahiagrass (Paspalum notatum Flugge) management combining nitrogen fertilizer rate and defoliation frequency to enhance forage production efficiency

Bahiagrass (Paspalum notatum Flugge) pastures are widespread in warm climates worldwide and respond to nitrogen (N) fertilizer. Nitrogen fertilization has recently decreased because of increased cost and concerns regarding excessive N in the environment. Responses of bahiagrass to treatments representing three alternative levels of pasture management were assessed. Treatments, each including 56 kg N ha^?1 applied for each growth period, were as follows: (i) six harvests with a total of 336 kg N ha^?1 annually (referred to as intensive management), (ii) three harvests with 168 kg N ha^?1 annually (intermediate management) and (iii) two harvests with 112 kg N ha^?1 annually (extensive management). The intensive management produced the most forage with the highest nutritive value. Intermediate management, with only half the amount of N fertilizer, produced at least 80% of the forage yield each year as the intensive management treatment (4‐year average of 8236 vs. 9122 kg ha^?1 for the intermediate and intensive management treatments respectively) with forage of acceptable nutritive value for some classes of livestock. Limited forage production from the last harvest each year restricts autumn management opportunities, even though crude protein concentration was usually sufficient for some classes of livestock. Extended growth periods, as those that occur with the less‐intensive management treatments, provide opportunities to accumulate forage for late‐season grazing. Matching livestock enterprises to the forage produced, particularly in terms of nutritive value, can contribute to favourable livestock production responses from a range of bahiagrass pasture management approaches.     

Red clover for silage: management impacts on herbage yield,nutritive value,ensilability and persistence,and relativity to perennial ryegrass

This 6‐year experiment quantified the impacts of management factors on red clover yield, persistence, nutritive value and ensilability, and compared these with perennial ryegrass receiving inorganic N fertilizer. Within a randomized complete block design, field plots were used to evaluate a 2 (cultivar, Merviot and Ruttinova) × 2 (alone and with perennial ryegrass) × 2 (0 and 50 kg fertilizer N ha^?1 in mid‐March) × 2 (harvest schedule) combination of the factors relating to red clover, and a 2 (harvest schedule) × 4 (0, 50, 100 and 150 kg N ha^?1 for each cut) combination of the factors relating to perennial ryegrass. The early and late harvest schedules both involved four cuts per year, but commenced a fortnight apart. Red clover treatments averaged 14 906 kg dry matter (DM) ha^?1 per year, whereas perennial ryegrass receiving 600 kg inorganic N fertilizer per year averaged 14 803 kg DM ha^?1 per year. There was no yield decline evident across years despite a decline in the proportion of red clover. The early harvest schedule and sowing ryegrass with red clover increased the herbage yield and digestibility. March application of fertilizer N to red clover treatments reduced the annual yield. Early harvest schedule increased and both fertilizer N and sowing with ryegrass decreased the proportion of red clover. Sowing with ryegrass improved the indices of ensilability, but reduced the crude protein content. Both red clover cultivars had similar performance characteristics. A selected red clover‐based treatment, considered to exhibit superior overall production characteristics, outyielded N‐fertilized perennial ryegrass in mid‐season. However, it had poorer digestibility and ensilability indices.     

Effects of 5 years of digestate application on biomass production and quality of cocksfoot (Dactylis glomerata L.)

Anaerobic digestion of biomass produces biogas for combustion and also provides a residual digestate. Although sometimes regarded as a waste product, the nutrient‐rich chemical composition of digestate makes it a potential organic fertilizer for agriculture. The goal of this study was to evaluate the effectiveness of digestate as a fertilizer on the biomass yield and chemical composition of cocksfoot (Dactylis glomerata L.). In a 5‐year small‐plot field experiment digestate fertilization treatments supplying 90, 180, 270, 360 and 450 kg N ha^?1 were compared with untreated plots and plots fertilized with 180 kg N ha^?1 of mineral N fertilizer. Swards fertilized with digestate produced higher biomass yield compared with the control. The same rate of nitrogen fertilizer (180 kg N ha^?1) supplied as digestate and from mineral fertilizers gave similar results on biomass yield. Herbage in swards fertilized with digestate contained less nitrogen, but the C:N ratio was much more suitable for biogas production. Digestate fertilization resulted in higher concentrations of cellulose and hemicellulose in biomass and lower contents of the inhibitors of anaerobic digestion—sulphur, calcium, magnesium and phosphorus—compared with those of swards receiving mineral fertilizers.     

The effect of stocking rate and calving date on grass production,utilization and nutritive value of the sward during the grazing season

A 2‐year whole‐farm system study compared the accumulation, utilization and nutritive value of grass in spring‐calving grass‐based systems differing in stocking rate (SR) and calving date (CD). Six treatments (systems) were compared over two complete grazing seasons. Stocking rates used in the study were low (2·5 cows ha^?1), medium (2·9 cows ha^?1) and high (3·3 cows ha^?1), respectively, and mean CDs were 12 February (early) and 25 February (late). Each system had its own farmlet of eighteen paddocks and one herd that remained on the same farmlet area for the duration of the study. Stocking rate had a small effect on total herbage accumulation (11 860 kg DM ha^?1 year^?1), but had no effect on total herbage utilization (11 700 kg DM ha^?1 year^?1). Milk and milk solids (MS; fat + protein) production per ha increased by 2580 and 196 kg ha^?1 as SR increased from 2·5 to 3·3 cows ha^?1. Milk production per ha and net herbage accumulation and utilization were unaffected by CD. Winter feed production was reduced as SR increased. Increased SR, associated with increased grazing severity, resulted in swards of increased leaf content and nutritive value. The results indicate that, although associated with increased milk production per ha, grazed grass utilization and improved sward nutritive value, the potential benefits of increased SR on Irish dairy farms can only be realized if the average level of herbage production and utilization is increased.     

Deriving seasonally optimal nitrogen fertilization rates for a ryegrass pasture based on agricultural production systems simulator modelling with a refined AgPasture model

Productive pasture systems require a regular supply of mineral nitrogen (N) to replace the N removed through the export of animal products and other loss pathways such as leaching and emissions. High spatial and temporal variability of both N supply by the soil and demand by the plant means that synchronizing these is challenging, and early indicators are lacking. Optimum fertilization rates for an irrigated ryegrass pasture in Canterbury, New Zealand, were determined in a simulation study with twenty fertilization rates using the Agricultural Production Systems Simulator with a refined version of APSIM's pasture module (AgPasture). Improvements in AgPasture included ideal N concentrations for tissues of different ages (growing, mature, senescent and dead) and allowing N remobilization to occur from all tissue stages. The critical N concentration curve (the minimum N concentration required to achieve maximum aerial biomass) was tested as an early indicator for guiding N fertilization, which maximizes plant growth while avoiding unnecessary environmental impacts. Highest pasture yields were achieved with application rates of 20, 30, 140 and 160 kg N ha^?1 for winter, autumn, summer and spring. These rates also minimized simulated N losses. Pasture N contents corresponding to the standing dry matter of the pastures were similar to the critical N curve in summer and spring, but lower critical N concentrations were obtained for autumn and winter. Before the critical N reference curve can be used to guide fertilization for pastures, further experimental studies, model testing and parameterization are required. It is also possible that season‐specific critical N curves need to be established for pastures.     

Effect of application timing and grass height on the nitrogen fertilizer replacement value of cattle slurry applied with a trailing‐shoe application system

This study investigated the effect of using a trailing‐shoe system to apply cattle slurry, under different conditions of grass height (low [LG]: freshly cut sward [4–5 cm height] vs. high [HG]: application delayed by 7–19 d and applied to taller grass sward [4–11 cm] height) and month of application (June vs. April), on the nitrogen fertilizer replacement value (NFRV) and apparent N recovery (ANR_S) of cattle slurry applied to grassland. NFRV was calculated using two methods: (i) NFRV_N based on the apparent recovery of slurry‐N relative to that of mineral‐N fertilizer; and (ii) NFRV_DM based on DM yield. The effect of applying slurry into HG swards, relative to LG swards, decreased the DM yield by 0·47 t ha^?1 (P ≤ 0·001), N uptake by 5 kg ha^?1 (P = 0·05), ANR_S by 0·05 kg kg^?1 (P = 0·036), NFRV_N by 0·05 kg kg^?1 (P = 0·090) and NFRV_DM by 0·11 kg kg^?1 (P < 0·001). It was concluded that the main factor causing these decreases with HG, compared with LG applications, was wheel damage affecting subsequent N uptake and growth of the taller grass sward.     

The efficiency of nitrogen in cattle manures when applied to a double‐annual forage cropping system

The use of cattle manure (CM) for fertilization presents challenges for optimizing nitrogen (N) use. Our work aimed to assess N efficiencies, in a 6‐year experiment with three biennial rotations of four crops: oat–sorghum (first year) and ryegrass–maize (second year) in a rainfed humid Mediterranean area of Spain. Fertilization treatments included the following: control (no N), 250 kg mineral N ha^?1 year^?1 (250MN), three CM rates (supplying 170, 250 and 500 kg N ha^?1 year^?1) and four treatments where the two lowest CM rates were complemented with either 80 or 160 kg mineral N ha^?1 year^?1. Treatments were distributed randomly in each of three blocks. Maximum dry‐matter yield (~44–49 t ha^?1 rotation^?1) was achieved in the third rotation, and only the control and the 170CM yielded significantly less. Within the limitations of the EU Nitrate Directive, the N steady state supply of 170CM always requires a complement of mineral N (80 kg N ha^?1) to maximize N agronomic efficiency. The maximum N‐fertilizer replacement value (250CM vs. 250MN) was 0·67, without significant differences between the two treatments in other N‐related efficiency indexes, which indicates that plants took advantage of residual‐N effects. Nitrogen losses by leaching in the 250CM treatment were around 5–7% of the N applied. This reinforces the sustainability of manure recycling in long cropping seasons.     

Impact of deferred grazing and fertilizer on herbage production,soil seed reserve and nutritive value of native pastures in steep hill country of southern Australia

Developing sustainable grazing management systems based on perennial species is critical to preventing land degradation in marginal land classes. A field study was conducted from 2002 to 2006 to identify the impacts of deferred grazing (no defoliation of pastures for a period generally from spring to autumn) and fertilizer application on herbage accumulation, soil seed reserve and nutritive value in a hill pasture in western Victoria, Australia. Three deferred grazing strategies were used: short‐term deferred grazing (no defoliation between October and January), long‐term deferred grazing (no defoliation from October to the autumn break) and optimized deferred grazing (withholding time from grazing commenced between annual grass stem elongation and seed head emergence and concluded in February/March). These treatments were applied with two fertilizer levels (with or without fertilizer at 50 kg phosphorus ha^?1 and 2000 kg lime ha^?1 applied in year 1 only) in a factorial arrangement and two additional treatments: continuous grazing (CG) and no grazing (NG) in year 1. The deferred grazing treatments on average produced herbage dry matter of 4773 kg ha^?1, the NG produced 4583 kg ha^?1 and the CG produced 3183 kg ha^?1 in year 4 (2005–06) of the experiment. Deferred grazing treatments with and without fertilizer application produced an average of 5135 and 4411 kg DM ha^?1 respectively. Averaged over 4 years, deferred grazing increased the germinable seed pool of perennial grasses by 200% and annual grasses by 50% (except optimized deferred grazing that considerably decreased the annual grass seed pool) compared with the CG. The best of the deferred grazing strategies increased the digestibility of pastures by 7% compared with the CG. The results demonstrated that deferred grazing from spring to autumn followed by rotational grazing could be an effective tool to increase herbage production and soil seed pool and improve the digestibility of native pastures in the steep hill country of southern Australia.     

Canopy height and N affect herbage accumulation and the relative contribution of leaf categories to photosynthesis of grazed brachiariagrass pastures

The effects of three canopy heights (10, 25 and 40 cm) and two N rates (50 and 250 kg ha^?1 year^?1) on herbage accumulation (HA), participation of leaf categories in the leaf area index (LAI) and photosynthesis of grazed “Mulato II” brachiariagrass (Brachiaria brizantha × B. decumbens × B. ruziziensis) were investigated during two summer growing seasons in Piracicaba, São Paulo, Brazil. The HA and LAI increased linearly from 8560 to 13600 kg DM ha^?1 year^?1 and 2.3 to 5.5 m² m^?2, respectively, as canopy height increased. Mulato II brachiariagrass maintained at 10 cm canopy height showed greater proportion of young leaves, but was less productive than taller canopies. Taller canopies had greater proportion of mature leaves in the LAI as well as greater photosynthesis. The greater N rate contributed to increased LAI, leaf and canopy photosynthesis rates and HA but did not affect the LAI composition. The total leaf area is more important to HA than the proportion of young leaves in the LAI, as taller canopies were more productive, suggesting that maintaining Mulato II brachiariagrass at 25 or 40 cm is advantageous for this grass.     

Seasonal nitrogen effects on nutritive value in binary mixtures of tall fescue and bermudagrass

The addition of cool‐season, tall fescue [Lolium arundinaceum (Schreb.) Darbysh.], to warm‐season, bermudagrass [Cynodon dactylon (L.) Pers.], pastures can improve forage productivity and nutritive value. Effects of four binary mixtures consisting of cv. Flecha (incompletely summer dormant) and cv. Jesup (summer active) tall fescue overseeded into established stands of cv. Russell and cv. Tifton 44 bermudagrass and three seasonal N treatments were evaluated on dry‐matter (DM) yield, crude protein (CP), in vitro true digestible DM (IVTDDM), acid detergent fibre (ADF) and neutral detergent fibre (NDF). Nitrogen‐timing treatments were 168 kg N ha^?1 (as ammonium nitrate) split into three applications per season with an additional 8·6 t ha^?1 of broiler litter (as‐is moisture basis) split into two applications varied to favour either tall fescue (in October and January), bermudagrass (in March and May) or both grasses (in January and March). Treatment effects were determined in samples of mixed herbage harvested in April, May, July, August and September of 2009 and 2010. Regardless of bermudagrass cultivar, herbage DM yield was greater (P < 0·05) in Flecha–bermudagrass than Jesup–bermudagrass in July of both years and in August 2010. Nutritive value generally was greatest in Jesup–Tifton 44, based on high CP and IVTDDM, and low ADF and NDF. Averaged across mixtures, avoiding fertilizer N and litter applications beyond April increased (P < 0·01) DM yield in April and May and IVTDDM in July (603 vs. 629 g kg^?1; 2‐year average) and August (618 vs. 660 g kg^?1) compared with applications in January–July. The timing of N and broiler litter applications on tall fescue–bermudagrass to favour growth of tall fescue appeared to increase fescue cover during the cool season and nutritive value of the mixed herbage during the warm season.     

Effect of grazing management on herbage protein concentration,milk production and nitrogen excretion of dairy cows in mid‐lactation

The objective of this experiment was to use diurnal and temporal changes in herbage composition to create two pasture diets with contrasting ratios of water‐soluble carbohydrate (WSC) and crude protein (CP) and compare milk production and nitrogen‐use efficiency (NUE) of dairy cows. A grazing experiment using thirty‐six mid‐lactation Friesian x Jersey cows was conducted in late spring in Canterbury, New Zealand. Cows were offered mixed perennial ryegrass and white clover pastures either in the morning after a short 19‐day regrowth interval (SR AM) or in the afternoon after a long 35‐day regrowth interval (LR PM). Pasture treatments resulted in lower pasture mass and greater herbage CP concentration (187 vs. 171 g kg^?1 DM) in the SR AM compared with the LR PM but did not affect WSC (169 g kg^?1 DM) or the ratio of WSC/CP (1·0 g g^?1). Cows had similar apparent DM (17·5 kg DM cow^?1 d^?1) and N (501 g N cow^?1 d^?1) intake for both treatments. Compared with SR AM cows, LR PM cows had lower milk (18·5 vs. 21·2 kg cow^?1 d^?1), milk protein (0·69 vs. 0·81 kg cow^?1 d^?1) and milk solids (1·72 and 1·89 kg cow^?1 d^?1) yield. Urinary N concentration was increased in SR AM, but estimated N excretion and NUE for milk were similar for both treatments. Further studies are required to determine the effect of feeding times on diurnal variation in urine volume and N concentration under grazing to predict urination events with highest leaching risk.     

Comparative effects of food processing liquid slurry and inorganic fertilizers on tanner grass (Brachiaria arrecta) pasture: grass yield,crude protein and P levels and residual soil N and P

This small‐plot field study evaluated food processing liquid slurry (FPLS) as a potential fertilizer for tanner grass (Brachiaria arrecta) production on an acidic loam soil. The treatments, arranged in a randomized complete block design with three replicates, consisted of an unfertilized control, inorganic fertilizer applied at 50 and 200 kg nitrogen (N) ha^?1 with and without phosphorus (P) at 50 kg P ha^?1, and FPLS applied at 50 and 200 kg N ha^?1. Compared to the unfertilized control, the FPLS applied at 200 kg N ha^?1 significantly increased grass dry‐matter yield (DMY), herbage crude protein (CP) and P content, and N and P uptake in the second of two trials and P uptake in both trials. However, DMY and contents, of CP and P were generally lower for the FPLS treatments compared to the inorganic fertilizers. Apparent N recovery was higher for the inorganic fertilizer treatments than FPLS treatments in trial 1, while apparent P recovery was similar among all treatments in both trials. The FPLS treatments did not significantly increase soil NO₃‐N and P concentrations, but increased NH₄‐N in the 0–15 cm layer. The results suggest that application of FPLS to tanner grass pastures is an alternative to its disposal in landfill.     

Urea and composted cattle manure affect forage yield and nutritive value in sandy soils of south‐central Vietnam

Improved forage management can support increased production in smallholder beef systems. Our objective was to evaluate the effects of mineral nitrogen (urea) and composted cattle manure on Brachiaria cv. Mulato II yield and nutritive value in south‐central coastal Vietnam. Study design was a randomized complete block on six farms (blocks), with treatments derived from the factorial combination of five rates of composted cattle manure (0, 4, 8, 12 and 24 Mg DM ha^?1 year^?1) and three urea rates (0, 60 and 120 kg N ha^?1 year^?1), split into six yearly applications. Yield was measured from 2011 to 2013 with 36‐day average harvest intervals. Forage nutritive value was measured in September 2011 and December 2012. Highest yields were achieved when both compost and urea were applied at high rates. The initial yield and tiller responses to urea application were not sustained over the duration of the study when no compost was applied. Compost applied in isolation did not increase yield. Compost application increased ash concentration. Urea increased nutrient yield for all forage nutritive value parameters measured. Composted cattle manure combined with urea benefits grass yield, but high application rates are needed for sustained high yields on sandy soils.     

Radiation‐use efficiency for forage kale crops grown under different nitrogen application rates

Crop growth is related to radiation‐use efficiency (RUE), which is influenced by the nitrogen (N) status of the crop, expressed at canopy level as specific leaf N (SLN) or at plant level as N nutrition index (NNI). To determine the mechanisms through which N affects dry‐matter (DM) production of forage kale, results from two experiments (N treatment range 0–500 kg ha^?1) were analysed for fractional radiation interception (RI), accumulated radiation (R_acc), RUE, N uptake, critical N concentration (N_c), NNI and SLN. The measured variables (DM, RI and SLN) and the calculated variables (NNI, R_acc and RUE) increased with N supply. RUE increased from 0·74 and 0·89 g MJ^?1 IPAR for the control treatments to 1·50 and 1·95 g MJ^?1 IPAR under adequate N and water in both experiments. This represented an increase in RUE of 52–146% for the range of N treatments used in both experiments, whilst R_acc increased by 9–17%, compared with the control treatments. Subsequently, the total DM yield of kale increased from 6·7 and 8 t DM ha^?1 for the control treatments to ≥ 19 t DM ha^?1 when ≥150 kg N ha^?1 was applied. The DM yields for the 500 kg N ha^?1 treatments were 25·5 and 27·6 t DM ha^?1 for the two experiments. RUE increased linearly with SLN, at an average rate of 0·38 g DM MJ^?1 IPAR per each additional 1 g N m^?2 leaf until a maximum RUE of 1·90 g MJ^?1 IPAR was reached in both experiments. There were no changes in RUE with SLN of > 2·6 g m^?2 and NNI >1, implying luxury N uptake. RUE was the most dominant driver of forage kale DM yield increases in response to SLN and NNI.     

The effect of the nitrification inhibitor dicyandiamide (DCD) on spring and annual herbage production in urine patches when applied in late summer or early autumn

A cut plot experiment was undertaken at two sites in Ireland, one a free‐draining acid brown earth at Moorepark (MPK) and the other a fine loam soil with imperfect drainage at Johnstown Castle (JC). The effect of applying the nitrification inhibitor dicyandiamide (DCD) at 10 kg ha^?1 in July, August and September or not applying DCD to plots receiving synthetic urine or zero urine on spring and annual herbage production was examined. In the experiment, each site received 350 kg nitrogen (N) fertilizer ha^?1 year^?1. The application of DCD in August at a rate of 10 kg ha^?1 significantly increased spring and annual herbage production by 14 and 15%, respectively, at MPK, when applied following urine application in year 1. There was no effect of DCD applied in year 1 on herbage production at JC. The application of DCD in August resulted in lower soil total oxidized N (TON) content up to sampling day 56 post‐urine application, at MPK in year 1, retaining higher N content in the soil. There was no effect of DCD on any of the parameters measured in year 2 at MPK or at JC. Urine application did not increase spring herbage production at either site. Urine application significantly increased annual herbage production at MPK only in year 1. Urine application increased annual herbage N uptake, herbage crude protein (CP) content and soil mineral N at both sites in both years.     

Stocking rate effects on liveweight gain of ewes and their twin lambs when grazing subterranean clover–perennial grass pastures

Two grazing experiments were conducted on non‐irrigated tall fescue–subterranean clover and cocksfoot–subterranean pastures subject to summer‐dry conditions in Canterbury, New Zealand, to measure the effect of low (8·3–10 ewes and their twin lambs ha^?1) vs. high (13·9–20 ewes and their twin lambs ha^?1) stocking rates (SR) on lamb and ewe liveweight gain in spring. In tall fescue–subterranean clover pasture, lambs grew faster at low (374 g per head d^?1) than high (307 g per head d^?1) SR, but total liveweight gain per ha was greater at high (12·3 kg ha^?1 d^?1) than low (7·5 kg ha^?1 d^?1) SR. In successive years in spring in cocksfoot–subterranean clover pastures, lambs grew faster at low (327, 385 g per head d^?1) than high (253, 285 g per head d^?1) SR but total liveweight gain per ha was greater at high (7·26, 7·91 kg ha^?1) than low (5·43, 6·38 kg ha^?1) SR. These studies indicate that in summer‐dry areas, subterranean clover‐based pastures will support high twin lamb growth rates in spring, with lower SR leading to higher lamb growth rates and more lambs reaching slaughter weights before the onset of dry conditions.     

The effect of applying cattle slurry using the trailing‐shoe technique on dairy cow and sward performance in a rotational grazing system

The effects of applying cattle slurry using the trailing‐shoe technique on dairy cow and sward performance were examined in two experiments in Northern Ireland. In Experiment 1, forty‐eight cows were allocated to two treatments, with or without slurry application. In Experiment 2, sixty cows were allocated to four treatments, a combination of high and normal grazing stocking rate, with or without slurry application. In Experiment 1, slurry was applied during the first and fourth rotations. In Experiment 2, slurry was applied prior to the first grazing rotation and during the second, fifth and sixth grazing rotations. In Experiments 1 and 2, the total inorganic fertilizer nitrogen (N) inputs applied within the slurry treatments were 200 and 133 kg N ha^?1, with 280 and 285 kg N ha^?1 used within the fertilizer‐only treatments in each experiment respectively. Varying responses of milk yield to slurry application were observed. In Experiment 1, with a normal stocking rate, no effect was observed. In Experiment 2 with two stocking rates, reduced milk yields were observed at both stocking rates. Although not significant, there were indications that this reduction in milk yield when slurry was applied was higher at higher stocking rates.