Clover Pasture Research Articles

White clover growth patterns during the grazing season in a rotationally grazed dairy pasture in New York

White clover (Trifolium repens L.) is an important stoloniferous pasture legume in the Great Lakes region of the United States, but it often has limited persistence. Researchers in New Zealand and Wales have found that in spring, compared with other seasons, white clover plants have reduced branching complexity and have the fewest buds that produce leaves. They therefore suggested that in spring the plants are most vulnerable to grazing and climatic stress.Because of severe winter and cool, wet spring weather in New York State, it was hypothesized that white clover plants would also be of low branching complexity, smaller and have low axillary bud activity in spring compared with later in the grazing season. To test this, growth of white clover was monitored in an orchard grass (Dactylis glomerata L.)/white clover pasture in New York that was rotationally grazed with dairy cows during the 1993 and 1994 grazing seasons.Three sets of plants were sampled. The first set consisted of forty random plants sampled before each grazing event. Stolon branching order, number of each stolon branching type and area the plant occupied were determined. Approximately each month before one grazing event, a separate set of 32 random plants was measured in the field to determine the area they occupied; these plants were then removed to the laboratory for the measurement of stolon order, number of each stolon type, stolon lengths, total number of growing points, number of taproots and adventitious roots, root position and above‐ground dry matter. Once a month, 12 additional plants were removed to measure axillary bud activity at each node.Leaf development from nodes tended to increase from spring to summer. However, the stolon branching order of white clover plants was not simpler in spring compared with summer or autumn. In 1994 during and after a dry and hot period, white clover plants were smaller, of lower stolon branching order and had fewer roots. Climate and associated soil organism activity appear to explain the different white clover growth patterns observed in New York and New Zealand. Severe winters in New York limit earthworm activity and stolon burial, which is important in contributing to stolon/plant breakdown in New Zealand. During the years of this study in New York, a hot and dry period had the most negative effect on the growth pattern of white clover.

Effects of reducing anthelmintic input upon growth and faecal egg and larval counts in young farmed deer grazing chicory (Cichorium intybus) and perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture

A rotational grazing experiment using weaner deer was conducted at Palmerston North, New Zealand, during the autumn, winter and spring, to compare the voluntary feed intake (VFI), liveweight gain (LWG) and carcass production of deer grazing chicory with those grazing perennial ryegrass/white clover pasture. Deer were either treated with anthelmintic at 3-weekly intervals (T) or anthelmintic was withheld until trigger-treatment (TT) criteria were attained. Pure red and 0·75 red: 0·25 elk hybrid stags and hinds were given forage allowances of 5 kg DM/deer/day in autumn and early-mid winter, 6 kg DM/deer/day in late winter and 7 kg DM/deer/day in spring. Deer grazed chicory or pasture in autumn and spring, with all deer combined on pasture during winter when chicory was dormant. Organic matter digestibility of diet selected was greater for chicory than for pasture in both autumn and spring.Anthelmintic-treated deer grazing pasture in autumn had significantly higher VFI and LWG, contributing to higher carcass weights, than TT deer. Anthelmintic treatment had no effect on these measures for deer grazing chicory in autumn. Clinical signs of lungworm infection were evident in pasture TT deer during autumn and winter, and in chicory TT deer grazing pasture during winter. Faecal egg counts (FEC) were significantly greater for pasture TT deer during autumn and early winter than all other groups. Faecal lungworm larval counts (FLC) were significantly greater for chicory TT deer following transfer to pasture, than for all other groups in early winter, although both FEC and FLC were low. Faecal larval counts were poorly related to clinical signs of lungworm infection during autumn, but were a better guide in winter. Plasma pepsinogen concentrations appeared unrelated to gastrointestinal parasite infection. Trigger-treated deer grazing pasture required five anthelmintic treatments during autumn and winter. The chicory TT group required no anthelmintic treatment when grazing chicory during autumn, but required two treatments after transfer from chicory to pasture during winter.There was no effect of anthelmintic regime on VFI and LWG in spring, and LWG was greater for deer grazing chicory than those grazing pasture. Hybrid deer had greater spring LWG and carcass weights than red deer when grazing chicory, but similar LWG and carcass weights when grazing pasture.It was concluded that grazing chicory offers the potential for reducing anthelmintic use in farmed weaner deer, particularly during autumn.

Growth and carcass production of young farmed deer grazing sulla (Hedysarum coronarium), chicory (Cichorium intybus), or perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture in New Zealand

Liveweight gain, voluntary feed intake, and carcass production were compared for pure red and hybrid (0.75 red: 0.25 elk) deer calves grazing sulla (Hedysarum coronarium cv. Necton), chicory (Cichorium intybus cv. Grasslands Puna), or perennial ryegrass (Lolium perenne cv. Nui)/white clover (Trifolium repens cv. Huia) pasture from weaning in March to slaughter in December of the same year, at approx one year of age. Organic matter digestibility (OMD) of diet selected was similar for all forages during autumn, but OMD of chicory (88.4%) was greater than both sulla (78.3%) and pasture (83.8%) during spring (P < 0.05). Sulla diet selected contained 5.1% condensed tannin (CT) in autumn and 8.4% CT in spring (P < 0.05); pasture and chicory contained 0.14–0.26% CT. VFI of deer grazing sulla was greater than for deer grazing chicory in autumn (2027 versus 1014 g OM d−1; P = 0.07), but not spring (2029 versus 2251 g OM d−1). In autumn, deer gained 293 g d−1 on sulla, 218 g d−1 on pasture (P < 0.01), and 183 g d−1 on chicory (P < 0.001). In winter, deer gained 150 g d−1 on sulla and 133 g d−1 on pasture. Final liveweight of deer grazing sulla was 106 kg, which was significantly higher than 97 kg for deer on pasture or 95 kg for deer on chicory (P < 0.01). Deer grazing sulla had greater carcass weights (59.9 kg) than deer grazing pasture (52.3 kg) or chicory (52.1 kg) (P < 0.01 hinds; P< 0.05 stags). Hybrid stags had significantly greater carcass weights than red stags (64.1 kg versus 56.3 kg; P < 0.01) and hybrid hinds (52.8 kg; P < 0.001). It was concluded that the increased growth and carcass weight of young deer grazing sulla was caused by a higher feeding value of sulla, with a component of this being increased utilisation of digested nutrients.

Sistema de pastejo rotativo "ponta e rapador" para novilhas de corte: 1. Desenvolvimento corporal

O objetivo deste trabalho foi avaliar o desenvolvimento de novilhas de corte no sistema de pastejo rotativo "ponta" e "rapador" durante o primeiro (Ano-1) e segundo (Ano-2) invernos/primaveras pós-desmama até o final do primeiro acasalamento aos 22-24 meses de idade. Setenta e seis bezerras de corte mestiças foram mantidas durante Ano-1 e Ano-2 em pastagem nativa melhorada de azevém (Lolium multiflorum L.) e trevo vesiculoso Yuchi (Trifolium vesiculosum cv. Yuchi). No período de verão/outono e acasalamento os animais foram mantidos em campo natural, em lote único. Os tratamentos Ponta (TP): grupo consumindo a metade superior da pastagem disponível; Rapador (TR): consumindo a metade inferior da pastagem foram testados. A evolução do peso vivo (PV) em cada etapa do experimento e ganho de peso médio diário (GMD) por período foram analisados. O peso vivo de TP diferiu do TR ao final do Ano-1 (195,6 vs. 168,1 kg), ao final do Ano-2 (316,3 vs. 274,1 kg) e ao início (318,5 vs. 275,7 kg) e final (341,5 vs. 304,4 kg) do acasalamento, respectivamente. O maior PV foi atribuído ao maior GMD obtido por TP sobre TR durante o uso da pastagem melhorada, com GMD de 0,790 vs 0,563 kg/dia e 0,753 vs. 0,522 kg/dia, no Ano-1 e Ano-2, respectivamente. Houve inversão no GMD com melhor desempenho do TR em relação ao TP (0,377 vs. 0,303 kg/dia) no acasalamento. O sistema de recria de novilhas para reposição, favorecendo determinado grupo de animais (TP), é uma das alternativas para obter pesos vivos satisfatórios, tornando-as aptas à concepção aos 22-24 meses de idade.

A lysimeter study of the impact of cow urine, dairy shed euent, and nitrogen fertiliser on nitrate leaching

The effect of cow urine, dairy shed effluent (DE), and urea fertiliser on nitrate leaching was determined using undisturbed soil lysimeters (500 mm diameter by 700 mm deep) with ryegrass (Lolium perenne)–white clover (Trifolium repens) pasture. Cow urine was applied to the lysimeters, at rates of 0 and 1000 kg N/ha in May 1996. Urea and DE were applied to urine-applied and non-urine-applied lysimeters at rates of 0, 200, and 400 kg N/ha in 4 split equal applications in May, August, and November 1996 and February 1997. Natural rainfall was supplemented with simulated rainfall in winter and spring (May–October) to achieve the 75th percentile of winter–spring rainfall records in the region. Flood irrigation was applied 6 times during summer–autumn (November–April) at 100 mm per application, which is a typical practice used by dairy farmers in the region. Drainage water was collected and analysed for nitrate, nitrite, bromide (added tracer), and ammonium. Over the first year of the experiment (May 1996–April 1997), 12% of the urine-N applied was lost through leaching, mainly in nitrate form. When urine (1000 kg N/ha) was applied in combination with DE (200 kg N/ha) and urea (200 kg N/ha), the mineral N leaching loss increased to 14% of the total N applied. The annual average nitrate concentrations in the drainage from the lysimeters that received urine alone, or urine+DE and/or urea, were 33–57 mg N/L, with a mean peak concentration of 110 mg N/L. These nitrate concentrations were significantly higher than in those treatments that did not receive urine (1–5 mg N/L). Because, on average, about 25% of the area of a grazed dairy paddock receives urine per year, the field-scale leaching losses were calculated by taking into account the dilution effect of drainage water from non-urine patch areas of the paddock. The calculated annual paddock losses were 33–60 kg N/ha, and on average the annual paddock nitrate concentrations were 10–17 mg N/L. This demonstrates the importance of accounting for the dilution of nitrate in the leachate from non-urine patch areas of the paddock. The annual average concentration from the treatment DE at 400 kg N/ha was significantly lower than that from the urea treatment at the same rate. This was probably because of the different chemical forms of N in each material, and needs to be taken into account when developing regional rules for land application of urea and effluents.

Effect of rate and time of nitrogen application from autumn to midwinter on perennial ryegrass - white clover dairy pastures in western Victoria. 1. Growth and composition

Field experiments were carried out at 2 sites to study the effects of time and rate of nitrogen (N) application from autumn to midwinter on perennial ryegrass–white clover pasture dry matter (DM) yield and species composition. Nitrogen (0, 15, 25, 30, 45, and 60 kg/ha) was applied in mid-April, early May, mid-May, early June, and mid-June 1996 onto a grazed pasture. Dry matter yield was estimated when perennial ryegrass in the 45 kg N/ha treatment reached the 3-leaf stage of development. Species composition estimates were made on all plots in autumn, late winter, and late spring (November). Asecond DM yield estimate was taken one regrowth cycle after the primary DM yield estimate to determine residual N impact on pasture growth, and then the pastures were returned to the grazing routine of the farm. Increasing levels of N fertiliser resulted in a linear (Site 1) and curvilinear (Site 2) primary DM yield response. Residual DM yield responses were linear at both sites. The highest primary DM yield response at Site 1 was 9.1 kg DM/kg N (mid-April application), whereas the highest residual N response was 9.4 kg DM/kg N (mid-May application). The time taken for the 45 kg N/ha treatment to reach the 3-leaf stage of development ranged from 38 (early June application) to 47 (mid-April application) days for the primary harvest, and from 46 (early May application) to 72 (early June application) days for the residual harvest. At Site 2, the highest primary DM yield response to N was 15.8 kg DM/kg N at 45 kg N/ha (mid-April application), whereas the highest residual N response was 8.3 kg DM/kg N (mid-June application). The time taken for the 45 kg N/ha treatment to reach the 3-leaf stage of development ranged from 24 (early June application) to 36 (mid-April and early May applications) days for the primary harvest, and from 30 (mid-April) to 57 (early June application) days for the residual harvest. Based on the current cost of urea, the study concluded that N fertiliser use during autumn to midwinter is economically viable for dairy farmers. Botanical composition was unaffected by N application. There were no treatment effects on botanical composition of the sward at either site the following spring (November). It is concluded that a ‘once-off’ strategic N application up to 60 kg N/ha during autumn to midwinter is not likely to influence dairy pasture composition in western Victoria.

The effect of condensed tannins in Lotus corniculatus upon reproductive efficiency and wool production in sheep during late summer and autumn

(23 g condensed tannins (CT) /kg DM) and perennial ryegrass-white clover pasture (1 g CT/ kg DM) during the late summer/autumn of 1997 (Experiment 1) and 1998 (Experiment 2). Ewes were in thin condition and weighed 54 kg in Experiment 1 and were fat and weighed 60 kg in Experiment 2. Oestrus was synchronised for two cycles in Experiment 1 and four cycles in Experiment 2. Ewes were grazed at maintenance for the first 10 days of each oestrus cycle and then ad libitum for the last 6 days, including ovulation. Half the ewes grazing L. corniculatus were drenched twice daily with polyethylene glycol (PEG), to inactivate the condensed tannins. Relative to ewes grazing pasture, grazing ewes on L. corniculatus increased both ovulation rate (OR) and wool production, with the response in OR being greater in Experiment 1 (34%) than in Experiment 2 (13%). Maximum increase in OR occurred after grazing lotus for two cycles (5 weeks). Increases in fecundity were caused by a reduction in the proportion of ewes exhibiting single ovulation and increases in the proportions having doubled and triple or quadruple ovulations. As judged by responses to PEG supplementation, part of the L. corniculatus response in OR could be explained by action of CT in Experiment 1 but not in Experiment 2. As voluntary feed intake was similar between the treatments, feeding L. corniculatus improved the efficiency with which ingested nutrients were used for reproduction and wool growth. It was concluded that grazing L. corniculatus during autumn has most potential for increasing OR in lighter ewes. Keywords: condensed tannin, forage, Lotus corniculatus, nutritive value, ovulation rate, wool growth Abbreviations

Production, faecal egg counts and worm burdens of ewe lambs which grazed six contrasting forages

Lambs were grazed on monospecific swards of one of six forages, some containing condensed tannins (CT); sulla ( Hedysarum coronarium), Lotus corniculatus and L. pedunculatus and some without CT (lucerne ( Medicago sativa), plantain ( Plantago lanceolata) and a ryegrass/white clover pasture ( Lolium perenne/ Trifolium repens)) to evaluate effects of forage type on gastrointestinal nematode burdens, faecal egg count as well as liveweight gain (LWG), wool growth and dag formation over a 42-day period. A new allotment of feed was provided at seven-day intervals, and feed was available ad libitum. Total worm burdens in a pre-treatment slaughter group were ca. 22 000 of which ca. 5000 were in the abomasum. Within each forage type, 10 of the 25 lambs (NP) were given an anthelmintic drench at 14-day intervals and the remaining 15 lambs (P) were not drenched. Daily gains of the NP lambs were double that of P lambs which grazed either L. corniculatus, lucerne or pasture, but parasitism had a lesser effect on performance of lambs which grazed sulla and L. pedunculatus. Plantain was not palatable and all lambs performed poorly. Highest daily gains in P lambs were for those which grazed sulla (175 g/day) and L. pedunculatus (160 g/day) with total worm burdens of 13 100 and 23 000 for the respective treatment groups. The other forages resulted in lower daily LWG in P lambs, and performance was not related to either worm burdens or worm species. This experiment has shown that, when sulla is fed, there is a reduction in worm burdens and faecal egg count (FEC), but with Maku lotus which also contains CT, the good level of performance was achieved despite in high worm burdens and FEC. The mechanisms by which these forages enable high levels of productivity in the face of a parasitism appear to differ, but both could be incorporated into forage feeding systems to reduce dependence on anthelmintic drenches.

Investigation into the mechanisms causing lime responses in a grass/clover pasture on a clay loam soil

A mowing trial was conducted on the Mangatea clay loam (a yellow‐grey earth or Umbric Dystrochrept fine hallositic mesic) to examine the mechanisms causing lime responses in a grass/ clover pasture. The trial site was located on a sheep and beef farm 8 km south of Te Kuiti, New Zealand. The site generally had cool winters and warm moist summers, with an annual rainfall of about 1400 mm. The treatments consisted of 3 lime rates (0, 5000, 10 000 kg ha−1) in the absence of P and 6 lime rates (0, 1250, 2500, 5000, 7500, 10 000 kg ha−1) in the presence of P (50 kg P ha−1 yr−1), all in the presence of sodium molybdate (Mo), and an additional treatment where P was applied in the absence of lime and Mo. Lime increased grass yield but decreased clover yield for the first 2 years after application. In Years 3 and 4, the responsiveness of the grass decreased and that of clover increased. Lime increased net N mineralisation by up to 58 kg ha−1, resulting in increased grass growth. Plant P uptake in both grass and clover also increased when lime was applied. However, yield responses were only seen in summer in clover when plant P concentrations in clover were less than 3.0 mg g−1. The lime‐induced increase in Mo availability would contribute to lime responses if basal Mo was not applied. Subsoil Al toxicity, particularly in summer, was limiting growth in some parts of the trial. However, there was no evidence that Mn toxicity was limiting yield, nor of any lime‐induced trace nutrient deficiencies. Results from the application of P and Mo indicate that there was at least a 6‐month delay in the transfer of N from clover to grass, with about 30% of the extra clover N uptake in Year 1 being transferred to extra N uptake in grass in Year 2.

Balanced and adequate nutrition of phosphorus and sulphur in pasture

Pasture production responses and nutrient concentrations from 5 rates of phosphorus (P) (0, 10,20,40, 80 kg ha−1) and sulphur (S) (0,5, 10,20,40 kg ha−1) applied three times in two years were measured on a direct‐drilled ryegrass/white clover pasture in a small plot mowing trial on a site with low fertility (initial soil Olsen P 5 μg ml−1, soil sulphate‐S 3 μg g−1, soil organic‐S 4 μg g−1) over two years. There were responses in total pasture and clover DM (dry matter) production to P and S in the second year. The response to S was much greater than to P. A bivariate Mitscherlich‐related equation accounted for 88–96% of the variation in measured values of clover DM production and ratios of P, S, and nitrogen (N) concentrations. The fitted equations were used to identify ratios of clover P, S, and N concentrations that resulted in balanced and adequate nutrition. Two nutrient elements are in balance when the yield response to one added on its own in relation to the maximum, equals the possible response to the other added on its own in relation to the maximum. Balanced nutrition in the second year occurred at a clover S/P ratio of 0.81–0.93. Using N concentration as an internal standard, nutrient adequacy is defined as the herbage yield with P and S in physiological balance relative to the maximum yield with P and S in physiological balance and expressed as RY [PS]. At 95% RY [PS], adequate nutrition was achieved at 100 × P/N of 7.10 and 100 × S/N ratio of 5.64. Clover S/P ratios derived from economically optimal fertiliser S/P ratios ranged between 1.03 and 0.82 for P and S fertiliser expenditure of $50–200 ha−1. Clover S/P and S/N ratios were higher than those determined in an earlier trial on a more developed site with higher soil fertility. Overall, the results from the trial reported here confirm that ratios of nutrient concentrations are useful indicators of balanced and adequate P and S nutrition for white clover.

A comparative study of nitrate leaching from intensively managed monoculture grass and grass–clover pastures

Nitrate leaching losses from intensively managed monoculture grass and grass–clover pastures were measured during 1994–96 at a long-term experimental farm in south-west Scotland. Field-size lysimeter plots were established in 1993 on the existing pastures on a silty clay loam non-calcareous gley. No fertilizer-N was applied to the grass–clover, while the monoculture grass was fertilized with c. 240 kg N ha−1 year−1, but both swards received 2–3 cattle slurry applications annually (120–390 kg total N ha−1 year−1). The pastures supported 2–3 cuts for silage conservation, and were grazed by dairy cattle and stocked with sheep during the winter months.Initially, leachate nitrate concentrations from the fertilized grass were considerably larger than those from the clover-based pasture, but became similar with time. The annual nitrate leaching losses from the grass–clover (24–38 kg NO3-N ha−1) were less than that from the monoculture grass (30–45 kg NO3-N ha−1), but the differences were not large considering the additional fertilizer-N applied to the latter treatment. Results also suggested that greater leaching losses occur during a warmer, drier year, compared to a cooler, wetter year, regardless of the source of N-input.

Evaluation of Lotus corniculatus for increasing pre-weaning growth of red and hybrid deer

Lactating red deer (Cervus elaphus) hinds and their calves were rotationally grazed on Lotus corniculatus or perennial ryegrass/white clover pasture at an allowance of 12 kg DM/hind/day during summer 1996 in Palmerston North, New Zealand. Half the hinds suckled pure red deer calves and half suckled hybrid (0·25 elk[ratio ]0·75 red deer) calves. Measurements were made of the diet selected, voluntary feed intake of the hinds and liveweight changes of the hinds and calves.Lotus corniculatus and perennial ryegrass constituted c. 90% of green material in the diet selected on the respective forages. Total nitrogen (N) content and organic matter digestibility (OMD) were higher for Lotus corniculatus than for perennial ryegrass/white clover pasture. Lotus corniculatus contained 21 g condensed tannin (CT)/kg dry matter (DM), whilst pasture contained only traces of CT (1·6 g/kg DM).Hinds grazing Lotus corniculatus tended to have higher voluntary feed intake, and calf liveweight gain (485 v. 399 g/day) and weaning weight (52·6 v. 48·1 kg) were greater than for deer grazing perennial ryegrass/white clover pasture. Hybrid calves grew faster than pure red deer calves (P&lt;0·01), with hybrid calves grazing lotus having very high liveweight gain (c. 520 g/day). Liveweight gain of hinds grazing Lotus corniculatus also tended to be higher (91 v. 20 g/day) than for hinds grazing perennial ryegrass/white clover pasture. CT was bound more strongly during chewing by red deer than had been found in comparable studies with sheep and the nutritional significance of this is discussed. Nutritional reasons for the superior performance of deer grazing Lotus corniculatus are discussed.

Symbiotic effectiveness and tolerance to early season nitrate in indigenous populations of subterranean clover rhizobia from S.W. Australian pastures

The effects of indigenous rhizobial communities on the establishment and functioning of subterranean clover- Rhizobium symbioses was examined using inocula obtained from soils of nine clover pastures and applied as dilute soil suspensions to pot-cultured subterranean clover ( Trifolium subterranean cv. Trikkala). The clover was grown without added N (minus N) or in pots fed with 5 mM KNO 3 (+NO 3 − treatment) for the first 4 weeks of a 12 week growth period. Symbiotic performances were compared with that of the recommended commercial inoculant, Rhizobium leguminosarum bv. trifolii strain WU95. Harvests involved separation of the plants into shoot, root and nodules and counting and weighing of nodules. Using NO 3 − of known δ 15N, the proportions of plant N derived from NO 3 − and N 2 were determined. Total N accumulated in the +NO 3 − treatment inoculated with WU95 was close to the average of that of the 9 soil-based inocula, but this Rhizobium performed poorly in the minus N treatment ( viz. 67 for WU95 versus a mean of 81 mg N plant −1 for soil inocula). Some inocula, including WU95, proved to be relatively tolerant of early season NO 3 −, with fixation in +NO 3 − treatments up to 80% of those of corresponding minus N cultures. In other associations fixation under +NO 3 − treatment was less than half that of matching minus N plants. Highly variable performances were recorded between associations in respect of nodule number, mean nodule size, nodule biomass per plant and nodule fixation rate. Several instances were recorded where total N accumulations in the presence of nitrate were more than 30% less than that of fully symbiotic plants. The reasons for variation in nodulation and N 2 fixation under early season NO 3 − are not clear, but suggest complex Rhizobium-directed influences shaping host plant response. The possibility of selecting NO 3 − tolerant rhizobia as alternative inoculants, for situations in which early season nitrate availability is restrictive to nodulation, is discussed.

Seasonal and lactational influences on bovine milk composition in New Zealand.

This study was designed to evaluate the respective influences of stage of lactation (SOL) and time of year on the seasonal variation in milk composition for pasture-fed dairy cows in New Zealand. Four herds of approximately 20 Friesian cows were used, one herd calving in a 6 week period beginning in each of January, April, July and October. Cows grazed rye-grass-white clover pasture only, except during June when all cows received supplementary pasture silage. Milk samples were collected from each cow in milk on four occasions during the year (September, December, March and June), to give a total of three samples per cow (early, mid and late lactation; about 30, 120 and 210 d respectively after calving). Samples were analysed for a detailed range of components. Concentrations of many milk components (e.g. total protein, fat, casein and whey protein) increased as lactation progressed; the extent of these increases depended on the time of year. These results indicated that spreading calving throughout the year would lessen seasonal variations in the gross composition of mill supplied to factories, leading to a more even distribution of product yield across the year. Despite this, variations in some important manufacturing properties were affected by time of year but not by SOL. Ratios of protein: fat and casein: whey protein were not significantly affected by SOL, but were affected by time of year. The solid fat content of milk was also affected by time of year. Seasonal variations in the manufacturing properties of milk may be reduced but not eliminated by changing the time of calving.

Influence of single applications of nitrogen on white clover nitrogen fixation in autumn and winter dairy pastures in south‐west Victoria, Australia

Effects of nitrogen (N) (0, 15, 30, 45 and 60 kg N ha−1) applied at five different times during autumn and early winter on the N fixation of Trifolium repens L. (white clover) in Lolium perenne L. (perennial ryegrass) / white clover pastures were examined (Experiment 1). Effects of applying different N fertilisers (e.g. urea and ammonium nitrate) at 45 kg N ha−1 in autumn, with and without phosphorus (P), potassium (K) and sulphur (S) on N fixation were also tested (Experiment 2). In Experiment 1, percentage N derived from the atmosphere (percent Ndfa) by white clover varied between 87% and 91% in the period after (24 to 36 days) N application. Increasing rates of N and time of application did not influence percent Ndfa. The amount of N fixed by white clover ranged from 0.8 to 3.7 kg N ha−1 in the period after N application. Increasing rates of applied N produced a significant (P<0.05) linear increase in the amount of N fixed. In Experiment 2, percent Ndfa and amount of N fixed (1.9 to 4.1 kg N ha−1) were unaffected by different N fertilisers, with and without P, K and S, in the period after (37 days) fertiliser application. For both experiments, fertiliser N increased dry matter yield while having no effect on white clover composition. It is concluded that single applications of N during the autumn and early winter benefit pasture growth without adversely affecting white clover N fixation or clover composition. This finding, however, will require further investigation.

Influence of the ryegrass endophyte (Neotyphodium lolii) in a cool‐moist environment II. Sheep production

The impact of the ryegrass endophyte on sheep production in a cool moist environment was examined in a field experiment in Southland, New Zealand. Ryegrass staggers were observed in one year when drought conditions were experienced, but not in years with average summer rainfall. There was a negative correlation (r = ‐0.9) between ryegrass staggers score and liveweight changes in animals forced to consume a high proportion of basal plant material, and animals grazed endophyte‐infected pastures less closely than endophyte‐free pastures. Lamb liveweight gains were not significantly affected by the presence of endophyte, except when drought conditions were experienced, although this is probably more a reflection of differences in pasture composition than of a direct endophyte effect. Faecal soiling was higher (P = 0.052) on endophyte‐infected pastures, especially under drought conditions (P = 0.025), and wool yields on mixed ryegrass/white clover pastures were 10% higher on endophyte‐free than on endophyte‐infected pastures (P = 0.003). There was no evidence of an endophyte effect on fat deposit. It is concluded that the endophyte had moderate negative effects on animal production in a cool moist environment.

Effects of complementary grazing by goats on sward composition and on sheep performance managed during lactation in perennial ryegrass and white clover pastures

The liveweight (LW) response of Gallega and Lacha ewes with their single suckling lambs when grazing with a mob of goats on perennial ryegrass ( Lolium perenne L.)/white clover ( Trifolium repens L.) pastures and its consequence on sward composition were analysed. From early March (turnout) to mid-June (lamb weaning), swards were grazed either simultaneously mixed in a 1:1 goat to sheep ratio or separately in a goat-first and sheep-last sequential grazing at 6 or 8 cm sward heights or in a 4-paddock rotation where goats grazed swards from 9 to 7 cm followed by sheep from 7 to 4 cm. Changes in botanical composition and in sheep liveweight performance were more significantly affected by the management and species grazing than by the sward height treatment. Swards where goats were last in had higher herbage masses, higher live clover and lower dead and stem proportions than swards where sheep and goats were mixed or sheep were last in. As a consequence of a sward clover enhancement over all treatments, ewe and lamb performances were benefited especially in the Lacha genotype, with the rotational and sequential managements having, respectively, an output of 298 and 252 kg LW/ha greater than the mixed management. These results suggest that goats could be used as a pasture management tool when integrated with sheep under these different grazing systems to enhance ovine performance during lactation.

Nitrate leaching from dairy shed effluent and ammonium fertiliser applied to a free‐draining pasture soil under spray or flood irrigation

The potential for contamination of groundwater by dairy shed effluent (DSE) and ammonium N fertiliser (NH4CI) was assessed by measuring nitrate leaching from 16 large soil lysimeters (80 cm diam. × 120 cm depth). Each lysimeter contained an undisturbed monolith of Templeton fine sandy loam (Udic Ustochrept) located in Canterbury, New Zealand, with established perennial ryegrass (Lolium perenne) and white clover (Trifolium repens) pasture plants. DSE and NH4CI were applied at 400 kg N ha−1 yr−1, in two split applications of 200 kg N ha−1. During the summer, each lysimeter received either spray (50 mm mo−1) or flood (100 mm mo−1) irrigation. During the winter, the natural rainfall received was supplemented with simulated rainfall in order to reach the 75th percentile of local rainfall records for the winter period. The concentration of nitrate in the leachate reached 5 mg N l−1 under both flood and spray irrigation following the first N fertiliser application (Dec 1995), but did not increase above control values (<1 mg N l−1) following the first DSE application. After the second DSE/fertiliser application (May 1996), the nitrate concentration in the leachate increased significantly during the winter/spring period, and appeared to be influenced by the antecedent summer irrigation conditions. Under spray irrigation, the nitrate concentration peaked at 40 and 17 mg N l−1 for the N fertiliser and DSE, respectively. Under flood irrigation, nitrate reached 25 and 10 mg N l−1 for the N fertiliser and DSE, respectively. The lower nitrate concentrations in the leachate under flood irrigation were attributed to the greater loss of nitrogen by denitrification and the greater dilution of soil solution nitrate by the larger volume of irrigation water applied. Enhanced denitrification from the higher moisture content in the flood/DSE treatment resulted in a smaller N leaching loss compared with the spray/DSE treatment. The amount of total mineral N (nitrate, ammonium, and nitrite) leached was smaller from the DSE than from the N fertiliser.

The fate of potassium, calcium, and magnesium in simulated urine patches on irrigated dairy pasture soil

A lysimeter study was carried out at Lincoln University, Canterbury, New Zealand from July 1990 to July 1991 to determine the fate of potassium (K), calcium (Ca), and magnesium (Mg) in urine patches on an irrigated dairy pasture soil (Templeton silt loam). Five undisturbed monolith lysimeters (800 mm diam. × 1200 mm depth) were extracted from an established ryegrass/white clover pasture. The lysimeters were installed in an underground lysimeter facility, where a 2 litre solution of synthetic urine, containing the equivalent of 55 g m−2 of K, was applied evenly to the surface of each lysimeter (c. 0.5 m2) to simulate a dairy cow urination event. No Ca or Mg was applied in the urine. During the following year, leachate composition and pasture yields from each lysimeter were determined. Twenty percent (10.76 g m−2) of the urine‐applied K was retained within the exchangeable fraction in the top 0–5 cm depth of soil. Total leaching losses of K during the experiment were negligible (0.99 g m−2 yr−1), and represented only 1.8% of the applied K (55 g) in the urine. Leaching from below animal urine patches was found to be a major loss pathway for soil Ca and Mg, with 7.4 and 4.9 g m−2 leached, respectively, over the duration of the experiment.

Strategic nitrogen fertiliser use on perennial ryegrass and white clover pasture in north-western Tasmania

Summary. The strategic application of nitrogen (N) fertiliser on temperate pasture is a popular management tool for boosting pasture production, particularly when low soil temperatures limit clover-derived N availability. The responsiveness of a perennial ryegrass and white clover pasture to increasing rates of N fertiliser (0, 15, 30, 45 and 60 kg N/ha), applied as a single application, was investigated for 5 pre and 5 post mid winter N application dates. The trial was laid out in a randomised split-plot design, replicated 4 times, with N application date in the whole plots and N fertiliser rate in subplots. Herbage yields were estimated by mowing small plots, with animals excluded for the duration of a single regrowth period on each plot. The data are presented as averages for the 5 pre and 5 post mid winter responses separately, as the means of the pre and post winter partitions were significantly (P&lt;0.001) different at all rates of N fertiliser for both years. Significant (P&lt;0.05) yield responses were noted between increments of N fertiliser up to the 45 kg N/ha application rate. In contrast, no significant (P&gt;0.05) increases in dry matter yield were noted between the 45 and 60 kg N/ha rates in all but one response, consistent with diminishing returns. The efficiency with which N fertiliser was utilised ranged between 9.0 and 15.9 kg N dry matter/kg. Nitrogen efficiency was consistently lower at the 60 kg N/ha rate than for lower rates of N fertiliser. The application of N fertiliser increased pasture dry matter yields by between 582 and 703 kg dry matter/ha. Based on the 1997 cost of urea, the additional forage produced cost between 6.4 and 10.1 cents/kg dry matter. The data are reviewed in terms of the potential for strategic N fertiliser applications during the winter, while still maximising utilisation of clover-derived N during the warmer months.