THE EFFECT OF SHEEP EXCRETA AND NITROGENOUS FERTILIZER ON THE BOTANICAL COMPOSITION AND PRODUCTION OF A LEY

Results are presented for the final two years of a previously described experiment.
The return of dung and urine by sheep to a ryegrass/white-clover ley was controlled by suitable harnesses to give four treatments (no dung or urine, dung, urine, dung and urine) which were combined in a replicated factorial design with four levels of nitrogenous fertilizer application (0, 52, 182, 312 1b. N per acre).
Applied nitrogen and urine were the dominant factors affecting botanical composition. The percentage of ryegrass increased and that of clover decreased with the progressive increases in nitrogen application. Volunteer species (mainly Poa spp.) contributed up to 20 per cent by the final year, the maximum occurring under the medium-high nitrogen treatment.
Urine restricted the incursion of weed grasses.
Combined with urine or the full return of excreta, high levels of applied nitrogen increased herbage production by up to 120 per cent. There was little response to dung except at the highest nitrogen level.
The yield response to applied nitrogen was almost linear. In the absence of animal returns response was poor, partly due to shortage of potash. When both excreta were withheld the light nitrogen dressing depressed the annual production compared with the control; where both excreta were returned together with this dressing no reduction occurred in annual yield and the spring yield was improved (p <0.05).     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS

In an experiment described earlier (13), the N content of Italian ryegrass in spring reached a high value one or two weeks after applying N and then fell quickly at first and then more slowly. After 10 weeks average N content (in DM) was 0.6% from an application of 25 lh N/ac (28 kg/ha), 0.9% from 75 lb N (84 kg/ha), and 12% from 125 lb N (140 kgJha). Nitrate-N content fell more abruptly and tben remained fairly constant. Percentage nitrate–N (in DM) fell below 0.10% during the second week after an application of 25 lb NJac, during the third week after 75 lb N, and during the fifth week after recciriag 125 lb N. The yield of N increased during the first 5 or 6 weeks, remained fairly constant for 3–5 weeks, and then hegan to fall. During the ninth and tenth weeks, the crop lost an average of 9 lb N/ac per week (10 kg/ha) after an application of 75 Ib N/ac and 12 lb N/ac per week (13 kg/ha) after 125 Ib N.     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS

This paper describes the rate of growth of Italian ryegrass in the spring, measured by recording DM yield at weekly intervals up to 10 weeks. There were 3 levels of applied N: 25, 75 aud 125 lhJac (28, S4 and 140 kgJha). Rate of growth declined after the sixth week at all 3 levels of N. Grass receiving 25 Ib N produced 5000 Ib DMJac (5600 kgJha) in 10 weeks, that receiving 75 lb N 6800 Ib (7700 kgJha) and that receiving 125 lb N 7100 lb (8000 kgJha). The DM content of herbage fell after the first week and subsequently increased steadily up to 10 weeks; the fall was least marked and the rate of increase most rapid at tbe lowest level of N. In vitro digestibility (measured in one year only) was much affected by stage of growth and little affected by level of N.     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS

The rate of growth of Italian ryegrass in the spring was measured by recording dry-matter yield at weekly intervals over periods of 6 weeks. There were 3 levels of applied N: 25, 75 and 125 lb/ac. Yield increased fairly slowly in the first 2 weeks and level of applied N had little effect. In the final 4 weeks the grass grew at a faster and fairly constant rate, which was very much affected by the level of N. Grass receiving 25 lb N produced 2900 lb of dry matter/ac in 6 weeks, 75 lb N 4400 Ib, and 125 Ib N 4700 lb. By the end of the first week, % N and % nitrate-N were higher at the 75 lb than at the 25 lb N level and by the end of the second week they were higher at the 125 lb than at the 75 lb N level. The effect of weather factors and the question of predictability of yield are discussed.     

THE EFFECT OF NITROGENOUS FERTILIZER ON THE RATE OF GROWTH OF ITALIAN RYEGRASS.

Residual response to an initial application of nitrogen was measured in 3 years and was found to be quite large, e.g. a response of 8 Ib DM per extra Ib N at the first harvest, when applying 125 Ib N/ac (140 kg/ha) rather than‘75 Ib (84 kg/ha) and allowing 6 weeks' growth, was increased to 21 Ib DM when yield from residual cuts was taken into account. Response was large in relation to the amount of N estimated to have been left behind after the first harvest. Marginal recovery of N, already quite high at the first harvest, was increased to a little over 90% when yield from residual cuts was taken into account Recovery, however, was lower than this when 10 weeks' growth was allowed before the first harvest, and it seems that, in this case, some N may have been lost from the system. A supplementary experiment suggested that the residual effect of N on DM yield could be obscured to some extent by fresh applications of N.     

THE INFLUENCE OF VARIOUS FORMS OF NITROGENOUS FERTILIZER ON THE GROWTH OF A PERENNIAL RYEGRASS / WHITE CLOVER SWARD IN EARLY SPRING

The effect of 4 or 5 forms of nitrogenous fertilizer on the yield and botanical composition of a perennial ryegrass/white clover sward was examined in 3 different years. The uptake of N by the grass was also estimated. Ammonium nitrate (as Nitro-Chalk), ammonium sulphate and urea gave similar yield increases, although in one year, when high rainfall followed the application of fertilizer, urea was slightly inferior. Gas liquor gave variable responses in the 3 years. Nitroform, a urea-formaldehyde, was generally less effective than the other forms of fertilizer. The uptake of N from Nitro-Chalk, sulphate of ammonia and urea did not vary greatly from year to year although the uptake of soil N by the untreated control did.
Response to N in the yield of dry-matter varied from year to year. This variation was due partly to differences in the amount of clover present and partly to differences in the extent to which N taken up by the grass was used for the synthesis of dry-matter.
The white clover content of the sward was not greatly reduced in spring by the application of the fertilizer, and there were no consistent differences between the effects on clover of the forms of the fertilizer. A reduction was apparent in the summer but not in the autumn.
It may be necessary to increase replication above the level of 3 to 6 which is frequently employed in field experiments if more precise quantitative estimates of response and of the relative efficiency of various forms of nitrogenous fertilizer are required.     

THE EFFECTS OF DIFFERENT LEVELS OF NITROGEN FERTILIZER ON THE YIELDS OF VARIETIES OF PERENNIAL RYEGRASS AND COCKSFOOT

Little is known about the possible differential responses to Nitrogen fertilizer in varieties within grass species. Two trials were conducted to study interactions between varieties and level of N. The dry-matter yields of 3 varieties of perennial ryegrass were compared in 4 cuts/yr at 3 levels of N fertilizer. Four cocksfoot varieties under the same cutting management were compared at 2 levels of N. In a total of 20 comparisons, the variety effect was significant on 10 occasions, and the N effect significant in all 20 sets of data. The interaction of variety and N level was significant in only one case suggesting that all varieties in each trial responded similarly to increasing levels of N fertilizer.     

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

Data from an experiment already reported (2) are used to examine a statistical method proposed by Walker et al . (8) for apportioning the nitrogen harvested in grass in a grass/ legume sward to legume, fertilizer and soil. Multiple regressions of the yield of N in the grass (G_n) upon N harvested in the associated legume (C_n) and N applied in fertilizer (F_n) were highly significant; but they were very variable, mainly because of the strong (negative) correlation between C_n and F_n. In some cases the coefficient for clover N was negative, in some cases the coefficient for fertilizer N exceeded unity; and the residual constant varied widely among 4 sets of plots on the same soil. The interpretation of such equations in physical terms is criticized on these grounds. The use of pure grass swards in conjunction with mixed swards gave estimates of the recovery of fertilizer N, and of the transfer of N from clover to grass, which agreed better with other published data than did the coefficients in a multiple regression. A simple regression of the estimate of transferred N in the grass upon the N harvested in the clover yielded a second constant. This constant, which varied considerably from one series of plots to another, is thought to indicate interactions between the various sources of N, which would be attributed to a direct effect of soil N if the multiple regressions were interpreted as Walker et al . suggest.     

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.     

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 production.
Data from the grass-alone swards allowed an estimate to be made of the effect of N on production at different cutting dates. This was compared with the effect of clover.
The effect of N was greater than that of clover in the mid- and late-season cuts. Clover made its greatest contribution, both directly and indirectly, at the first cut, taken in May.
Under very dry conditions (1959), N was more effective than clover in maintaining production and the proportional response was large in relation to that produced under moist conditions.
The results are discussed with reference to the present seasonal use of N on grassland and an argument is advanced for increasing its use in mid-season.     

THE EFFECT OF PESTICIDES ON THE YIELD AND BOTANICAL COMPOSITION OF A NEWLY-SOWN RYEGRASS LEY AND OF AN OLD MIXED PASTURE

Newly-sown S24 perennial ryegrass at Hurley and old established ryegrass-dominant mixed pasture at Rothamsted were treated with several pesticides, singly and in combination, over the period 1969–73. Yields were either unaffected or increased by up to 30% in any one year, depending on the treatment, the newly-sown sward giving the more consistent response from year to year.     

SOME EFFECTS ON THE YIELDS OF RYEGRASS STRAINS OF VARYING THE GROWING TECHNIQUE AND THE CONDITIONS OF MANAGEMENT

The effects are reported of varying the growing technique, and the conditions of management, on green and air-dry yields of herbage from five strains of ryegrass during 1952 and 1953. All strains were grown in three ways: as spaced plants, in drill-rows and in stands broadcast with white clover. There were two experiments, one managed for hay and aftermath, the other cut more frequently.
In both experiments the broadcast plots reached their peak of herbage production first; the spaced plants took longest. There were considerable differences in the seasonal distribution of yields from the different growing techniques during the first harvest year. In 1953, the differences were smaller but the secondary annual peak of herbage production observed in the broadcast plots was not detected in the spaced plants.
The total annual production per unit area was greatest from the broadcast, and least from spaced-plant plots. Yields on certain occasions, however, were greatest from spaced plants and least from broadcast areas.
The effects of varying the conditions of management were greatest on population samples sown broadcast and least on those growing as spaced plants, their reaction when grown in drills being intermediate.
Differences in plant population in the various growing techniques are discussed in relation to the above results.     

THE EFFECTS OF LEVEL OF NITROGEN FERTILIZER ON BEEF PRODUCTION FROM GRAZED PERENNIAL RYEGRASS/WHITE–CLOVER PASTURES

The treatments in this summer–grazing experiment were designed as a 3X3 factorial; 3 levels of nitrogenous fertilizer, supplying 0, 336 and 672 kg N/ha per annum, and 3 stocking rates. The fertilizer was applied in 6 to 8 dressings at intervals of 3 to 4 weeks. The animals used were fattening Hereford X Friesian steers. The stocking rates were calculated on the basis of data available on herbage production under N and irrigation treatments and varied according to the level of N input. The experiment was laid out in 6 randomized blocks, which were grazed in rotation. Blocks were removed from the grazing cycle in spring and early summer of each of the 3 years (1962—-4) over which the experiment was conducted and cut for conservation: yields were recorded. Details are given of: grazing management; results of studies of soil–N levels; the quantities of herbage removed for conservation: the quantity, chemical and botanical composition of the herbage available for grazing; and herbage consumption.     

THE INFLUENCE ON THE FOLLOWING ARABLE CROP OF SHEEP EXCRETA AND FERTILIZER TREATMENTS APPLIED TO A LEY

The differences in soil fertility in a ley as a result of treatments applied for four years in a sheep-grazing trial were measured by growing crops of wheat and kale. The pasture treatments had been: control, dung, urine and dung plus urine, each combined with four levels of fertilizer nitrogen.
Yields of winter wheat harvested in 1956 ranged from 27.1 to 38.6 cwt. per acre. Plots to which faeces had been allowed to return during the pasture phase outyielded (p <0.001) those from which it was withheld. Urine was relatively ineffective except in combination with nitrogen. In the absence of animal returns, nitrogenous fertilizer depressed grain and straw yields. A top-dressing of K applied to the wheat in spring as a sub-treatment had no significant effect. The percentages of N and K in the grain were unaffected by the former pasture treatments, or by the K top-dressing.
A subsidiary small-plot experiment in which the above pasture treatments had been combined with P and K, each at two levels, was cropped with marrow-stem kale. In general, N applied to the pasture increased kale yields except where dung and urine had been withheld. Neither P nor K had a significant effect, except when combined. The leaf/stem ratio of the kale was reduced by applied N and by P (both p <0.05).
The pasture/arable-crop relationship is considered.     

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.     

THE EFFECTS OF LEVEL OF NITROGEN FERTILIZER ON BEEF PRODUCTION FROM GRAZED PERENNIAL–RYEGRASS/WHITE–CLOVER PASTURES

The treatments in this summer–grazing experiment were designed as a 2 × 3 factorial, there being two levels of nitrogenous fertilizer (nitro–chalk), supplying 0 and 336kg of N/ha per annum (NO and N3, respectively) and three stocking rates. The fertilizer was applied in 7 dressings at approximately three–weekly intervals. The animals used were Hereford x Friesian steers; these were slaughtered at the end of the grazing season. The stocking rates were calculated on the basis of expected herbage production. The experiment was laid out in 6 randomized blocks which were grazed in rotation. Two blocks were cut for conservation before grazing each year; up to the end of June only 4 blocks were used for grazing.
There was little contamination of the swards with unsown species. With the NO swards the clover contents declined each year, but remained fairly high at over 20% in 1965. Clover contents also declined each year in the N3 swards and by 1965 were only 2 to 4%.
The quantities of herbage cut for conservation were higher from the swards receiving N. The live–weight gains of the cattle (per head) were higher at the lower stocking rates, the effect of stocking rate being more noticeable in the July to Oct. period. Live–weight gains per ha increased at the higher stocking rates. In 1963 and 1965, as stocking rates increased carcass weights per animal decreased and carcass quality, as indicated by the commercial grades, was poorer. In 1964, a dry spell from July to Oct. necessitated the removal of cattle from the experiment and the effects of treatment on carcass weight and quality were not apparent.     

THE EFFECT OF NITROGENOUS FERTILIZER ON AN ESTABLISHED WHITE CLOVER SWARD

The effect of nitrogenous fertilizer on a white clover sward was studied to obtain information to be used in the evaluation of white clover in grassland. There was no evidence of a yield response. The weight of nodules was depressed by the addition of fertilizer.
Where management is adjusted to maintain white clover in swards receiving large quantities of nitrogenous fertilizer the clover may use part of this fertilizer at the expense of symbiotic fixation.
The relation of the results obtained to the assessment of the benefit derived from white clover in mixed swards is briefly discussed.     

A NOTE ON THE LIVEWEIGHT CHANGE OF SHEEP GRAZING AT THREE STOCKING RATES AND TWO LEVELS OF NITROGENOUS FERTILIZER

The liveweight changes of sheep grazing at 3 stocking rates and 2 levels of N fertilizer were recorded. The results are discussed in relation to the model proposed by Owen and Ridgman (1) for short–term periods of grazing.     

硫肥对油菜的增产效应

在３个地区７个点进行油菜硫肥试验。结果表明，施用硫肥比不施硫肥的油菜生长好，菜籽产量高。土壤ＳＯ—Ｓ含量在２６．０ｍｇｋｇ－１以下，施用硫铵的比对照增产１４．８％—４９．８％，达到极显著或显著水平，施用硫磺比对照增产６．５％—３４．２％，达极显著或显著水平。土壤ＳＯ—Ｓ含量＞４５．０ｍｇｋｇ－１，施硫铵、硫磺和石膏均比不施硫肥的增产，但未达显著水平。     

THE EFFECTS OF HARVEST DATE ON THE YIELD AND QUALITY OF SEED OF TETRAPLOID HYBRID RYEGRASS

The ripening process in a tetraploid ryegrass is described in terms of seed moisture content changes. The heavier seeds of tetraploids appear to be shed at an earlier stage in the ripening process than those of diploid ryegrass. The seed moisture level at which a tetraploid ryegrass seed crop is harvested is shown to be a critical factor determining the yield and quality of from the crop harvested seed.