THE PRODUCTION OF EARLY SPRING GRASS

Spring nitrogen significantly increased the yields of early spring grass. The response per lb. of nitrogen applied in the early spring ranged from 9 to 28 lb. of dry matter, depending upon the weather. Autumn nitrogen significantly increased herbage yields during the autumn. The increase per lb. of nitrogen ranged from 12 to 22 lb. of dry matter.
Autumn nitrogen caused significant increases in the yield of early spring grass in 1956, but these increases were very small and not of practical importance.
The effects of autumn grazing on spring yields were not consistent and were small when compared with the effects of spring nitrogen. Both autumn grazing and autumn nitrogen tended to reduce the percentage of soluble carbohydrates in the stubble and roots of grasses in November.     

THE PRODUCTION AND UTILIZATION OF WINTER GRASS AT VARIOUS CENTRES IN ENGLAND AND WALES, 1954–60

The effects of management on the production of winter grass wen studied of 47 site England and Wales from 1954 to 1958.
Cocksfoot swards provided better grazing during December and January than perennial ryegrass. The best treatment for winter-grass production from cockfoot swards was to rest from mid-August, giving un application of 52 lb of nitrogen per acre at this time.
Perennial ryegrass produced relatively high yields if rested from early September, but the herbage should be grazed before the end of November because of the risk of it rotting.
Cocksfoot herbage in normal swards lost more weight from December to January than cocksfoot sown in wide drills.
Local Factors, such as aspect, altitude and sward vigour, were generally more important than latitude in determining level of yield in December. but there were greater lovsess of dry matter from December to January in the north than in the south.     

A COMPARISON OF THE REACTION OF DIFFERENT GRASS SPECIES TO FERTILIZER NITROGEN AND TO GROWTH IN ASSOCIATION WITH WHITE CLOVER

Seven species or varieties of grass, and a mixture of 3 of them, were sown in pure swards and treated with 4 levels of nitrogenous fertilizer (0,17·5, 35 and 70lb N per acre per cut). Each species, and the mixture, was also sown with white clover. The experiment was cut 4 or 5 times per year. The effect of fertilizer on the yield of each grass was compared with the effect of clover on the yield of the grass/clover swards. Mean annual yields showed an approximately linear response to N; there was a small but significant fall in response to the highest level of N. Response among the species ranged from 20 to 30 Ib of dry matter per Ib N applied for the intermediate level of fertilizer and from 14 to 23 Ib for the final increment of fertilizer.
S37 cocksfoot, S48 timothy, S24 ryegrass, and a mixture of these grasses, were high yielding and responded well to fertilizer N; Irish ryegrass and Agrostis tenuis were less productive and gave poorer responses to N. S215 meadow fescue and S23 ryegrass were intermediate in yield and response.
There were no significant differences between the annual yields of the 8 grass/clover mixtures; the yields of the grass and clover components of each mixture were inversely related. The effect of clover on the yield of the grass/clover mixtures was estimated to be equivalent to the effect of an annual application of 205 lb N per acre to Agrostis tenuis and 120 lb N to S48 timothy. The fluctuations in annual yields were greater with grass/ clover mixtures than with grass swards receiving N.
The yields of grasses when sown with clover were in similar order to their yields when sown pure; but whereas the latter tended to fall from year to year, the yields of the grass components of mixtures (except Irish ryegrass) did not.     

CLOVER NITROGEN AND SWARD PRODUCTIVITY

Under mowing conditions in the absence of the animal, ultra-simple swards based either on ryegrass or cocksfoot gave large increases in yield of dry matter and nitrogen from the inclusion of white clover in the seeds mixture. Raising the clover seed rate from 1 to 3 lb./acre gave a further response in yield.
As the swards aged, the continuing effect of increased clover seed rate was dependent on applied nitrogen.
The rate of transference of nitrogen from clover to the soil depended upon the species of the associated grass, the clover seed rate, the age of the sward and the degree of reduction of the clover in the sward.
Suppression of clover led to an increase in soil nitrogen, particularly with high seed rates of clover.
Dry matter response to applied nitrogen (69 lb./acre/annum) was greater in cocksfoot than in ryegrass. Fertilizer nitrogen had little effect on the yield of nitrogen from the sward except where the high seed rate of clover had been used.     

Factors influencing tissue turnover during winter in perennial ryegrass-dominated swards

Despite low net grass growth rates in Ireland between mid-November and February, tissue continuously turns over as new leaves are produced and older leaves senesce. The effects of closing swards from grazing on three dates in autumn (1 September, 20 September and 10 October) on tissue turnover in a perennial ryegrass sward during the winter were examined at two sites in the north-east and south of Ireland. Leaf extension and senescence rates were greater in the south than in the north-east, and were greatest on the earliest closing date at both sites. Leaf appearance and extension rates at both sites were closely correlated with accumulated daily air temperature above 6°C and mean soil temperature. Site-specific factors also influenced tissue flux, possibly including grazing intensity at closing and density of tillers of perennial ryegrass. Swards in the autumn with high herbage masses [>2000 kg dry matter (DM) ha⁻¹ approximately] and high leaf area index (LAI; about 2·5 and above) had the greatest leaf senescence rates and the greatest declines in herbage mass during the winter. Leaf senescence rates per tiller in high LAI swards were correlated positively with amount of leaf per tiller and also the proportion of green leaf in the second youngest expanding leaf lost to senescence. As potentially a complex of interactive factors influences tissue flux in winter, it is proposed that the data from this study be used in conjunction with other data to construct a dynamic model to predict more reliably optimum closing date in autumn for herbage utilization in winter.     

RESPONSE OF GRASSLAND TO NITROGENOUS FERTILIZER IN THE WEST OF ENGLAND

Extensive replicated plot experiments were carried out at Henley Manor Farm from 1956–1961 to obtain accurate measurements of herbage production and response to nitrogenous fertilizers under West of England conditions. 356 plots were used; use of the herbage by both cutting and grazing was studied. The principal results are: Grass/ clover swards (containing approx. 35% clover) grown without nitrogenous fertilizer averaged 75 cwt dry matter per acre per annum. Application of nitro-chalk to initially grass/clover swards reduced the clover content of the herbage. About 133 lb N/annum was required by an all-grass sward to equal the production of a grass/clover sward without N. Attempts to increase production of grass/clover swards by using N for early growth and relying on clover for mid-season growth were unsuccessful in 2 out of 3 years. Swards (initially grass/clover) gave significant increases in total dry-matter production from regular use of the lowest level of N (26.0 or 34.7 lb N/acre/cut or graze) in 44 out of 49 cases. Extremely high yields were obtained from the heaviest use of N (104.2 lb N/acre/silage cut). 52.1 lb N/acre/cut or graze was the optimum rate of application on ail-grass and grass/clover swards. Up to about 350 lb N/acre/annum the dosage-response curve was very nearly straight for all-grass and grass/clover swards. On the grazed plots herbage left ungrazed amounted on average to only 6% of the total. The health of all stock on the high nitrogen plots (as well as all others) was excellent.     

STUDIES IN THE DIGESTIBILITY OF HERBAGE

This paper presents the results of 125 digestion trials with sheep fed herbage at different stages of growth from three clover-free pure grass swards. During 1958 and 1959, a study was made of the yield, leaf lamina, nitrogen, ash and digestible organic matter percentage ( D ) of first growths, of regrowths cut at monthly and two monthly intervals and of swards receiving various quantities of fertilizer nitrogen.
For first growths in the spring D remained almost constant until the ears started to protrude from the leaf sheaths and then fell rapidly at approximately 0·5 per cent per day. The D values for S 23 ryegrass were three weeks later than S 24 ryegrass, which correspond with later ear emergence of the latter. S 37 cocksfoot was always less digestible than S 24 ryegrass although both were at similar stages of growth. This difference in D also occurred in the regrowths. The D of monthly regrowths tended to fall with each successive cut, although in 1959 ryegrass values improved in the autumn.
Fertilizer nitrogen had little effect on D .
Despite the warmer spring and drier summer in 1959 and corresponding changes in production per acre there was little effect on D .     

Effects of pesticides and fertilizer on invertebrate populations of grass and wheat plots in Kent in relation to productivity and yield

At a site in Kent, perennial ryegrass (Lolium perenne) variety S24 and Italian ryegrass (L. multiflorum) variety RVP, wheat varieties Armada and Norman, and the original mixed grass ley were grown in small plots during 1982–84. Two toxic pesticides (phorate and aldicarb) were applied to half the total number of plots three times each year to eliminate soil invertebrate populations. Fertilizer was also applied to most plots. The yields of the crops, grown with and without pesticide, and the effects of the fertilizer were compared. Grass herbage yield was measured on three occasions during the summers of 1983 and 1984. Wheat grain yields were also determined in 1983. During the first year significant differences were not apparent in grass dry matter yield between pesticide-treated and non-treated plots, but significant differences were found in the second year. The perennial ryegrass was more susceptible to pest damage than the Italian ryegrass or the grass ley. Grass yields varied between cuts and in relation to variety and pesticide treatment, yields tending to be greater in untreated plots. Fertilizer treatment greatly increased grass dry matter yields, particularly with the Italian ryegrass. The effects of pesticide treatment on both wheat varieties varied although some yield enhancement was evident. Invertebrate animal populations in pesticide and fertilizer-treated plots were also assessed in autumn 1982, spring and autumn 1983 and spring 1984. In contrast to pesticide treatment, fertilizer treatment had little effect on soil invertebrate populations. Nematode populations were reduced at each sampling occasion by the pesticide treatment. Slug populations were initially unaffected but were subsequently reduced. Leatherjackets, by far the most abundant pest in both grass and wheat plots, were markedly affected by pesticides on all sampling occasions. Generally, fewer soil-dwelling dipterous larvae were recovered in spring than in autumn. Stem-boring dipterous larvae were virtually absent.     

THE EFFECT OF WHITE CLOVER AND NITROGENOUS FERTILIZER ON THE PRODUCTION OF A SWARD

Three-year leys of cocksfoot/white clover and cocksfoot alone were dressed with 0, 35, 105 and 210 lb. N per acre every year to provide information on the effect of clover and N on annual production.
White clover contributed 40% of the dry-matter yield but its presence was responsible for 77% of this yield where no N was used: it was responsible for less than 8%, and contributed 5%, where 210 lb. N per acre was applied annually, lt was estimated that grass alone receiving 160 lb. N per acre would yield as much dry matter as a mixed sward receiving none.
Clover had the indirect effect of raising yield of nitrogen in the companion grass by 60 lb. per acre per year. A maximum of l06 lb. was recorded in 1958.
The response of the tnixed sward averaged 10 lb. of dry matter per lb. N. Prevailing economic circumstances will determine if this level is satisfactory in practice.
The recovery of N by grass alone varied from 54% at the lowest level of N to 80% at the highest. On mixed swards apparent recovery was negative or low: N was to a large extent only replacing the effect of clover which was suppressed by its use.
Factors influencing response and the difference between that obtained under experimental and practical conditions are discussed.
The use of N to produce out-of-season grass may give good response, but may cause a reduction in clover contribution.     

SEASONAL VARIATION IN APPEARANCE AND GROWTH OF GRASS ROOTS

Data from two field experiments, and from a root observation trench, suggest an annual cycle of root growth by grass swards. The production of adventitious roots from the tillers of four grass species, and from perennial ryegrass in a grass/clover sward varied greatly during the year. They were produced in increasing numbers through late winter to early spring; this rate fell sharply in April or May, and was low in summer. The differences in this annual cycle between grass species were small. Examination of roots of perennial ryegrass in a glass-sided trench showed that root elongation was most rapid in summer and was largely confined to the lower soil horizons. Rather more roots were produced in early autumn than during summer, but the rate of elongation was slow from October until spring.
Individual roots of grasses appeared to survive for limited periods. Their longevity depended upon the time of year in which they were first formed; those produced in autumn or winter lived longer than those produced in spring or summer.     

A comparison of perennial ryegrass‐ and tall fescue‐based swards with or without a cropping component for dairy production: Animal production,herbage characteristics and financial performance from a 3‐year farmlet trial

Perennial ryegrass/white clover swards have some limitations in temperate grazed dairying systems. This study tested the hypothesis that farmlets based on alternative species would be equally or more profitable than those perennial ryegrass‐based, and would produce more herbage in summer‐dry conditions. Six farmlets were established; three with perennial ryegrass‐ and three with tall fescue‐based swards. For each grass species, one farmlet was solely based on grass‐clover swards while the other two had either chicory‐red clover or lucerne crops planted on 20%–25% of the area. Animal‐ and herbage performance‐related variables were measured for 3 years, and calculated financial performance was evaluated. Using tall fescue improved total annual herbage yield compared with perennial ryegrass, but animal production and operating profit were lower. This was likely due to the reduced yield and nutritive value of tall fescue during spring and an associated decline in daily milksolids production. The deficit in spring milksolids production was never recovered, despite greater herbage production from tall fescue during summer/autumn. Incorporating chicory‐red clover or lucerne crops reduced both annual herbage and milksolids production. This reduced farm income, while increasing operating expenses as the farmlets required crop renewal and more purchased supplementary feed to maintain feed supply. Under the conditions of this study (i.e., partial irrigation, high nitrogen supply), changing the forage base from perennial ryegrass to tall fescue did not improve animal production or profitability, nor did incorporation of crops on 20%–25% of the farmlet area.     

THE PRODUCTION OF WINTER GRASS FROM A ROW CROP OF COCKSFOOT AND LUCERNE

A crop of cocksfoot and lucerne in alternate rows was subjected to various autumn treatments for winter pasture. The yield of grass in winter, and the effect of autumn and winter treatments upon yield and composition in the following spring, are reported and discussed.
Maximum yield of winter grass was achieved by resting from an early date and applying nitrogenous fertilizer. The response to fertilizer applied in August and mid-September for winter grass production was as good as that obtained on ordinary swards at other times of the year. To ensure an adequate yield in any year the crop would need to be rested from early August and to receive about 70 lb N per acre.
The spring growth of cocksfoot was distinctly retarded by cutting twice in winter, i.e. in November and February. Cutting once only had no such adverse effect.
Both cocksfoot and lucerne persisted satisfactorily. The use of nitrogenous fertilizer to promote autumn growth of grass did not greatly reduce the overall productivity of the lucerne.
The two species were complementary in the sense that, in combination, they maintained a high aggregate yield of herbage under a range of weather conditions in midsummer and in winter.     

THE INFLUENCE OF TWO LEVELS OF NITROGENOUS FERTILIZING ON THE LONG-TERM PRODUCTIVITY OF LEYS

Two levels of nitrogen application (70 and 180 lb per acre per annum) were compared on 6 long-duration leys. The treatments were repeated for periods of up to 4 years on tiie same swards. The higher N dressing produced 2230 lb more dry matter per acre than the low rate, an increase of 28%, and the yield was also more evenly spread throughout the season. There was virtually no clover on the high-N swards. The proportion of clover varied under low N but tended to increase as the season progressed. The sown grasses remained the dominant sward constituents throughout the experiment, and there was no sign of loss of vigour on the high-N swards. Utilized-starch-equivalent outputs were calculated from 3 different swards for 1956–8 and there was a significant positive correlation between the dry-matter yields and utilized-starch-equivalent output of swards.     

The effects of separated cow slurry liquor on soil and herbage nitrogen in Phalaris arundinacea and Lolium perenne

Simulated swards of reed canary grass ( Phalaris arundinacea L ) and ryegrass received applications of separated cow slurry liquor in winter, at rates up to the equivalent of 500 m³ha⁻¹. Subsequent measurement of oxidized nitrogen in the soil under the different species indicated that lower levels of soluble forms of nitrogen were found under the reed canary grass than were under the ryegrass sward. At the first harvest after liquor application, the dry weight yield of reed canary grass responded positively to increasing applications of slurry liquor, but the ryegrass sward appeared to be damaged by very high rates of application. At later harvests, yields of the two species were similar, but over the season, apparent recovery of the nitrogen applied to the swards was greater in the reed canary grass than in ryegrass, suggesting that this species could be of value in the control of losses of nutrients from livestock wastes.     

EFFECTS OF NITROGEN FERTILIZATION OF MIXED SWARDS ON HERBAGE YIELD, DRY MATTER DIGESTIBILITY AND VOLUNTARY FOOD INTAKE OF THE CONSERVED HERBAGES

In 2 experiments nitrogenous fertilizer was applied at 3 levels (0, 46 and 92 lb N/ac) to a permanent pasture and a ryegrass/clover ley and the swards were harvested before ear emergence and conserved as either artificially dried grass or tetrapod hay. Apparent dry matter digestibility and voluntary food intake of the conserved herbages were measured with sheep.
N caused a small but significant depression in apparent DM digestibility but did not affect voluntary food intake. It increased yields of DM and digestible DM significantly.
The DM digestibility and voluntary food intake of hay were always significantly lower than those of the corresponding dried grass. Voluntary food intake of all fodders was directly related to herbage digestibility and inversely related to herbage crude fibre content.     

NITROGENOUS FERTILIZATION OF ITALIAN RYEGRASS IN SPRING

A series of experiments in eastern Scotland, carried out over a 7–year period, on the application of N fertilizers to Italian ryegrass for producing early spring grass, indicated that maximum yields are likely to be produced if the fertilizer is applied not later than the middle of March in most seasons. Only rarely did application in February result in a loss of N and in reduced herbage yields. Italian ryegrass appears to be able to make some growth at temperatures below 40†F.
Increasing the rate of N application resulted in increased DM yield, the response averaging 9–4 lb DM per lb N. Herbage N concentration was increased by the additional N fertilizer. Nitro–chalk and ammonium sulphate were equally effective in producing early grass, irrespective of application date.     

POTENTIAL PASTURE PRODUCTION IN THE UPLANDS OF WALES

Study of the growth of heavily fertilized swards of S23 perennial ryegrass (Lolium perenne) at a hill and a lowland centre in mid-Wales during 1968–69 demonstrated that lower productivity in the uplands could only be partially attributed to a shorter growing season and poorer summer growth conditions. Comparison of yields with potential transpiration estimates indicated that winter damage had an important bearing on production during the following year. In 1969, the adverse combination of a mild autumn and a severe winter led to a spring tiller density which was less than 25% of normal at the hill centre. With an annual fertilizer input of over 500 kg N/ha (480 lb N/ac) total DM production in 1968 and 1969 was 10.6 and 4.4 t/ha at the upland site compared with 14.8 and 10.1 t/ha in the lowlands (9450, 3920, 13,190 and 9000 lb/ac).     

Effects of an autumn defoliation on overwintering, spring growth and yield of a white clover/grass sward

An established sward of binary mixtures of meadow fescue (Festuca pratensis) and white clover (Trifolium repens) (either AberHerald, Grasslands Huia or Sandra) was subjected to (A) no further defoliation, (B) a defoliation in late September or (C) a defoliation in late October after four harvests had been taken during the grazing season. About a tonne of dry matter (DM) was removed by the autumn defoliations. There were two levels of nitrogen application in spring, either 0 or 90 kg ha^?1. The development of grass and clover morphology and population sizes from early autumn until the first harvest the following year was followed by regular sampling of the above-ground material. Stolons were analysed for total non-structural carbohydrates (TNCs), and the temperature at stolon level was continuously recorded. There were no interactions between autumn defoliation, clover cultivar or nitrogen treatments on any of the parameters studied. White clover growing-point numbers and stolon morphological characteristics were reduced in size during the winter and did not recover during the spring. A defoliation in late September resulted in the greatest reduction, whereas there were no differences between the other two treatments. The grass tiller population increased from early autumn until the last sampling occasion in May, but both autumn defoliations resulted in a smaller increase. Defoliation in late September had the greatest impact. The TNC content of white clover stolons fell from about 350 g kg^?1 to 150 g kg^?1 DM from late autumn until late April. There were small differences between the treatments, but a defoliation in late September resulted in a significantly lower level in late autumn. The temperature amplitude at stolon level was consistently greater in plots defoliated in late September. Total DM harvested in spring was 4367, 2564 and 3536 kg ha^?1, of which 388, 352 and 460 kg ha^?1 was white clover, from treatments A, B and C respectively. It is concluded that an autumn defoliation may affect the overwintering of white clover negatively, but that the effect on the grass may be even more detrimental.     

A COMPARISON OF THE HERBAGE YIELD OF ITALIAN RYEGRASS AND TALL FESCUE MIXTURES IN THE SECOND AND THIRD YEAR AFTER SOWING

The annual yield of tall fescue was higher than that of Italian ryegrass in the third year after sowing, but the total yield of herbage from grass plus clover swards was similar.
In both the second and third year after sowing, the yield of herbage in the spring grazing was higher when fescue was used as the sown grass. The method of establishment of both tall fescue and Italian ryegrass affected the total and seasonal yield in the second and third year after sowing, but the magnitude of these effects was not nearly as marked as it was earlier in the life of the leys. In the second year after sowing, swards of both Italian ryegrass and tall fescue had a higher yield of total herbage and of white clover, and a lower ingress of unsown species, when established without a cover crop and grazed frequently in the year of sowing.
The inclusion of red clover did not increase total yield of DM in the second and third year after sowing, and it slightly decreased the yield of the tall fescue mixture in the third year following sowing when N was applied. S170 tall fescue was readily grazed by sheep in spring and autumn.
The apparent recovery of applied N varied with the mixture sown, and the management given during establishment.     

Short-term effects of nitrogen on the growth and nitrogen nutrition of small swards of white clover and perennial ryegrass in spring

Small swards of white clover and perennial ryegrass were established in Perlite in a heated glasshouse, as either monocultures or mixtures of equal plant numbers. On 26th March, 1984 the swards were moved outside and their growth studied over the period to 29th May. All swards received a basal level of nitrate N to simulate soil mineralization and two-thirds received additionally the equivalent of 80 kg N ha⁻¹. Over the experimental period (26th March-29th May) clover maintained its proportion of total mixture dry weight In swards given 'fertilizer'-N and increased its proportion in those given only 'basal' N, However, clover declined as a percentage of total mixture dry weight during the first period of the experiment when total leaf area index (LAI) and ambient temperatures were low, and increased its percentage later when temperature and LAI had risen. Changes in tiller and stolon growing point numbers were not good indicators of changes in dry weight. Relative yields and relative replacement rates also were not good indicators of relative performance in mixture. Where 'fertilizer'-N was applied, clover derived less of its nitrogen from that source than grass although their uptakes per unit shoot dry weight were similar.