THE RELATIONSHIP BETWEEN TOTAL N INPUT AND YIELD OF CUT GRASS SWARDS

The response of clover-free grass swards to fertilizer N when cut repeatedly at grazing and silage stages of growth was measured in four experiments at North Wyke. There was variation between years in the yield obtained at a given fertilizer N rate (Fn) and this was attributable to differences in soil-N supply. By estimating soil-N supply from the N-yield of the non-fertilized plots (Zn), total N inputs (Tn) were assessed. Over a number of reported experiments it was found that grass-N yield (Gn) was related to Tn by the equation Gn=0.57 Tn, where Tn=Fn+l.7 Zn. The level of grass-DM yield depended on stage of growth at cutting, as well as on total N supply. These results, and others examined from the literature, suggest that while total N input is the main determinant of grass-DM yield, account must be taken of the time available, before defoliation, for the N taken up to be utilized in DM production. The use of Tn values has allowed the collating of N responses obtained over a range of sites, seasons and workers.     

A MATHEMATICAL RELATIONSHIP BETWEEN NITROGEN INPUT AND OUTPUT IN CUT GRASS SWARDS

The importance of predicting grass N yield lies in its controlling influence on grass DM output and thus on animal production. Results from 88 experiments studying the use of fertilizer N on cut grass swards show that the major part (97%) of the variation in grass N yield could be explained in terms of fertilizer N rate, an estimate of soil N and an interaction between the two. From this, it appears that high fertilizer N recovery is associated with a high uptake of soil N and vice versa.     

THE TESTING OF GRASS VARIETIES IN SWARDS WITH CLOVER: THE EFFECT OF GRASS SEED-RATE ON COMPARISONS OF GROSS YIELD

Three experiments were carried out to examine the influence of grass seed-rate upon the amount of clover growing with different varieties of perennial ryegrass. The bred varieties S23 and S24 were compared with Irish ryegrass. A larger quantity of clover grew with Irish ryegrass than with bred varieties at any given seed-rate. If the varieties were to be compared in terms of herbage of similar clover content, then Irish ryegrass sown at 20 lb/ac had to be compared with S23 or S24 sown at about a quarter of that rate. Reducing the seed-rate of the bred varieties from 20 to 5 lb/ac had only a small effect upon yield of ryegrass, and this was offset by an increase in yield of clover. Since weed grasses also took advantage of low grass seed-rate, it is concluded that other factors in the management of variety trials must be so controlled as to produce a satisfactory clover content without too drastic a reduction in the seed-rate of any variety. The relationship between grass seed-rate and yield of clover varied markedly with the availability of moisture.     

THE EFFECT OF TIME AND RATE OF N APPLICATION ON THE PRODUCTIVITY OF GRASS SWARDS IN TWO ENVIRONMENTS

Six identical experiments (3 in Devon and 3 in Suffolk) investigated the effect of 200, 300 and 400 lb N/ac (224, 336 and 448 kg/ha), given in 1, 2, 4 or 8 equal applications, on the yield and seasonal production of perennial ryegrass swards cut every 25 days. Each rate of N Increased DM and N yields. Giving the N in 4 or 8 dressings gave higher DM, bnt rather lower N yields, than applying the N in 1 or 2 dressings. The effect on DM yield of splitting the N was most marked at 400 lb NJac (448 kgJha). Seasonal production was closely related to the time of N application and most uniform where N was given in 8 dressings. Differences between Devon and Suffolk were most evident where the N was given in 4 or 8 dressings and occurred in the second half of the season when the low rainfall in Suffolk apparently restricted N uptake and DM yield. The efficiency with which N taken up by the plant was used for DM production was affected by sunshine. It is concluded that rainfall and sunshine will limit the extent to which fertilizer N can he used to control herbage production.     

THE EFFECT OF THE GRAZING ANIMAL ON THE N STATUS OF GRASS SWARDS

Thirty-one sets of N yield data were considered, taken from seven experiments grazed by sheep. N yield could be explained in terms of fertilizer N rate, an estimate of soil N and an interaction between the two. Fertilizer N increased grass N yield more on grazed swards than on cut swards, and this effect was greatest on soils with high available soil-N. It is concluded that N recircula-tion can be substantial on heavily-stocked swards receiving high rates of fertilizer N, so increasing the efficiency of fertilizer as a source of N in these conditions.     

THE OUTPUT OF SWARDS ON COMMERCIAL FARMS IN RELATION TO FERTILIZER AND OTHER MANAGEMENT FACTORS

Survey data collected during a grassland-recording investigation showed a strong positive correlation between nitrogen input and the output of utilized starch equivalent per acre. At the levels of output covered, sward type was not very important in relation to total yield. Herbage species were important for other reasons and the choice of seeds mixtures should be determined by factors such as earliness and lateness of growth and resistance to disease and drought. The survey showed that well-managed ley and permanent pasture are both capable of producing at a high level. A disturbing feature of the results was the low production of most spring resowings, primarily as a result of poor management. Although the records were obtained from an above-average group of farms, the results have general application. Potential responses to fertilizers may be even greater on less intensive farms, especially with regard to phosphate and potash. However, the level of production of a field will always depend finally on the level of management exercised by the farmer himself.     

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.     

THE EFFECT OF COMPANION GRASSES ON TIMOTHY PRODUCTION IN SWARDS CUT FOR CONSERVATION

To assess the effect of companion grasses on timothy productivity, swards of timothy sown alone or with one of eight companion grasses were harvested as for silage four times per year for two years. The companion grasses were: diploid perennial ryegrasses S24 and S23; tetraploid perennial ryegrasses Reveille and Taptoe; meadow fescues S215 and S53 and cocksfoots Trifolium and S143. Averaged over the N application rates (226, 339 and 452 kg N/ha per year) the total herhage yields of timothy/companion-grass mixtures were all significantly superior to that from timothy alone in the first year. Only perennial ryegrass S24 and the cocksfoot mixtures significantly outyielded timothy alone in the second year. Winterkill hecame evident in April of the second year and pure timothy and timothy/meadow-fescue swards were least affected. Over all swards, timothy DM increased hy a mean of 19% from the first to the second year, compared with a fall of 20% in total herhage DM. The contrihution of timothy herhage to the mixtures was very low with companions other than meadow fescue. Late-heading varieties were more compatihie than early-heading varieties, and tetraploid ryegrasses were more compatihie than diploid ryegrasses. It is concluded that if the inherently valuahle characteristics of timothy are to he exploited, it should not he sovm with aggressive companion grasses.     

不同氮肥管理对毛豆共生固氮及产量的影响

以两个不同基因型毛豆品种为试材，研究不同的氮肥管理对毛豆产量及其共生固氮的影响，结果表明，氮肥的施用时间对毛豆的产量及固氮量具有显著的影响，二对复叶始期（Ｖ１．５），每公顷追施５０公斤尿素和在种子形成中期（Ｒ４．５）每公顷再追施２５公斤尿素，两个品种都获得了最高的饱荚产量及最大的固氮量。四对复叶期（Ｖ４），土壤中的速效氮含量与毛豆的固氮率呈正相关，但在开花期和种荚形成期表现为显著的负相关。每公顷仅施２５公斤尿素不能满足毛豆丰产及最大限度利用其共生固氮的需要。     

THE EFFECT OF NITROGEN FERTILIZER AND CLIPPING FREQUENCY UPON THE YIELD AND IN VITRO DIGESTIBILITY OF INTERMEDIATE WHEATGRASS

The effect of rate of nitrogen fertilizer and clipping frequency on total production of dry matter (DM), in vitro digestible organic matter (DOM), and crude protein (CP) was investigated in the first harvest year of intermediate wheatgrass. The highest yields of DM and DOM, but not of CP, were obtained at the longest clipping intervals and at the higher rates of fertilizer application. Fertilizer failed to give satisfactory increases in yield even at very high rates of application when a 2-week clipping interval was used. The interaction between clipping frequency and fertilizer rate had a highly significant effect on yields of both DM and DOM. A sharp decline in percentage DOM that occurred with increasing length between clippings was offset to some degree by application of N fertilizer. A similar assessment of treatments was obtained from DOM and DM yield data when the grass was fertilized with N, but not when N was deficient. The CP data gave a different assessment of treatments from that obtained from either DOM or DM data.     

PATTERNS OF SPRING GROWTH IN SWARDS OF DIFFERENT GRASS VARIETIES

Production of dry matter by swards of ryegrass and cocksfoot varieties in winter and spring is dependent on a number of growth processes, each with different environmental requirements. Growth in the strict sense with the production of new leaves has been found to continue throughout the winter in Aberystwyth, although the rate of production fell very low during periods when the mean air temperature approached freezing, especially in cocksfoot varieties.
Because of the ceiling set by the natural balance between leaf death and leaf formation, net increases in weight of above–ground parts in undefoliated plants may not occur for extended periods during winter. When, however, tiller numbers start to increase, or the ceiling is raised by an increase in size of tillers, dry–weight increases can come about. The extension of leaves and intern odes in spring, measured in terms of sward height, seems to be largely governed by flower initiation. A certain degree of extension was found to be present before this in an Algerian type.
Practical distinctions between early and late types, which are based on flowering dates or sward height, or on parameters influenced by these characters, are not associated with similar differences in production of above–ground parts. These distinctions do not, therefore, permit a completely full and accurate picture to be obtained of winter– and spring–growth potentials in different varieties.     

FERTILIZER USE ON GRASSLAND IN ENGLAND AND WALES

The paper describes the use of fertilizers on grassland in England and Wales, as shown by surveys of fertilizer practice carried out during 1957–60.
About a third of the total consumption of N and K and almost half the total consumption of P is on grassland. Fertilizer use on leys has increased rapidly in recent years and the overall average rate of application is now of the order of 0·3 cwt N, P₂O₅ and K₂O per acre per annum; permanent grass receives about half as much P and very much less N and K than the leys.
Generally speaking, consumption of N and K per acre of grassland was higher in arable districts than in livestock-farming areas, and on dairy farms than on rearing and feeding farms. However, rearing and feeding farms received more P per acre of grass (in particular, more basic slag) than arable farms. Little farmyard manure was used on grassland in the arable districts, whereas in the dairy counties of the western half of England and in Wales it formed a substantial part of the total plant nutrients supplied to grassland, particularly on fields mown for hay.
The paper also gives information on types of fertilizers used and the timing of fertilizer applications to grassland. All but about a fifth of the nitrogen used on grassland was applied between February and April.     

寒地不同肥料对大豆产量影响的研究

在黑龙江省海伦市寒冷地区进行不同肥料对大豆产量影响的试验研究,其目的是为筛选适应寒冷地区绿色大豆生产的较佳肥料.结果如下:黑农科有机无机复混肥(简称黑农科肥)对大豆品种绥农14产量正向效应＞三元素复合肥＞惠满丰＞有机肥＞双绿肥＞生物钾肥,其增产原因主要是开花期单株叶面积、根容量和根瘤数的增加,进而促进其生长发育导致增加了单株荚数和粒数;施用黑农科肥土壤有机质含量5.95%,略低于施有机肥(有机质含量6%),而其土壤容重与有机肥相同均为0.82 g/cm3.全氮为0.45%,全磷为0.16%,表明其有利于土壤结构和肥力的改善;在寒冷地区每公顷施375kg黑农科肥有利于绿色大豆生产.     

THE EFFECTS OF CUTTING AND GRAZING SYSTEMS ON HERBAGE PRODUCTION FROM GRASS SWARDS

Studies were made on two perennial ryegrass–dominant swards of the effects of cutting and grazing systems of herbage production. A motor scythe was used for cutting and sheep in small enclosures for grazing. In both systems, herbage production was measured by a ground-level sampling technique, using sheep shears, and the difference between pre-treatment and post-treatment herbage was expressed as ‘utilized yield’. Correction for soil contamination is ensured by quoting all results on an organic-matter basis. Grazing treatments averaged 14–16% more organic matter and 36–45% more crude protein than cutting treatments in both experiments. These differences were ascribed to recycling of N under grazing. Infrequent defoliation gave higher yields than frequent, and severe defoliation higher yields than lenient under both cutting and grazing systems. The trends shown by cutting and grazing intensities are comparable and can be quantified. There is need to examine closely the relationships between the effects of cutting and grazing techniques on herbage production, since such knowledge would allow a more accurate prediction of the relevance to the grazing situation of results obtained under cutting.     

THE RECOVERY OF FERTILIZER NITROGEN FROM VARIOUS DEPTHS BELOW SWARDS

A microplot technique for the placement of nitrogen at depth under an established grass sward is described. The effect of nitrogen placement at various depths on the dry matter yields, root yields and nitrogen uptake of two grass species is recorded. The results for cocksfoot and red fescue indicate that there is little fall-off in uptake of nitrogen from placement at depths down to 12 inches, and that cocksfoot also recovers substantial amounts of nitrogen from 18 inches and 2 feet. Recovery by red fescue at these depths was not investigated.
Althotigh there is little difference between the two grasses in their relative ability to absorb nitrogen at the various depths, there is an indication that, weight for weight, cocksfoot roots are probably more efficient absorbers of nitrogen than those of red fescue.
The significance of the findings is discussed in the light of present-day methods of fertilizer application.     

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

Seven species or varieties of grass, and a mixture of 3 of them, were sown in pure swards, treated with 4 levels of nitro-chalk (0, 17·5, 35, and 70 Ib N/ac/cut) and cut 4 or 5 times each year. Each species and the mixture were also sown with white clover, and the effect of fertilizer N on the yield of N in each grass was compared with the effect of clover on the yield of N harvested from the grass/clover swards.
The regression line for response in yield of N with increasing levels of fertilizer N showed slight, but significant, upward curvature. The grasses differed in their uptake of N from the soil, S37 cocksfoot and S48 timothy showing relatively high uptakes, and the ability of each grass to take up fertilizer N was usually related to its uptake of N from the soil. Differences in the yield of dry matter between the species, at a similar level of N, are discussed, and it was concluded that perennial ryegrasses were most efficient and Agrostis tenuis was least efficient in using the N taken up in the production of DM.
In general, there were no significant differences between the yields of N of the grass/clover mixtures; the N yields of the grass components were significantly different and tended to be inversely related to the N yields of clover.
Grasses which gave high yields of N with fertilizer were also high yielding when grown in association with clover. Pure grass swards required more than 200 Ib fertilizer N/ac/yr in order to yield the same amount of N as the grass/clover swards. The amount of N estimated to have been derived by grass from clover (indirect effect of clover) increased each year; it was highest with S37 cocksfoot and lowest with Irish perennial ryegrass, averaging 46 and 23 Ib N/ac/yr, respectively.