首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 46 毫秒
1.
SEASONAL VARIATION IN APPEARANCE AND GROWTH OF GRASS ROOTS   总被引:5,自引:0,他引:5  
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.  相似文献   

2.
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.  相似文献   

3.
C. N, P and S were determined in the roots of white- and red-clover, lucerne, perennial ryegrass, cocksfoot and timothy, taken at intervals over a period of several months, and in roots of ryegrass receiving four levels of fertilizer N. The results indicated that decomposition of The root material would result in The mineralization of N in substantial amounts from white clover, in smaller amounts from red clover and in negligible amounts from lucerne. The roots of grasses would tend to immobilize soil N, even when They bad received moderate applications of fertilizer N. The C:P ratios suggested that the legume roots would neither mineralize nor immobilize inorganic pbospbate but that the grass roots would induce immobilization. S was likely to be mineralized in appreciable amounts from roots of white– and red–clover, but not firom roots of lucerne or the grasses.  相似文献   

4.
Two experiments were set up in a semi-controlled glasshouse environment to determine the nature of the competitive stress, and the characters associated with competitive ability, during the seedling growth of some grass species. Over a period from sowing until the attainment of a relatively stable tiller population root competition was almost entirely responsible for the suppression of Festuca arundinacea in association with H1 ryegrass at two densities. In contrast, root and shoot competition were of equal importance in bringing about the suppression of Phalaris coerulescens in association with H1 ryegrass, an effect which only occurred at the high density.
Differences in the patterns of root growth of the species and populations are discussed in relation to differences in their competitive abilities.
It is suggested that the rate and extent of nodal root production are closely associated with seedling competitive ability.  相似文献   

5.
In young grass plants it is possible to relate the weight of the root to that of the shoot through the allometric formula y = bx k . Using this formula it was found that flower formation was associated with an increase in shoot growth relative to that of the root. Within varieties of Lolium , the greater the intensity of heading the more was the growth of the shoot relative to that of the root. Perenniality was associated with a high rate of root growth relative to that of the shoot. A decrease in the light intensity or soil water reduced the growth of the plant as a whole, but light decreased root growth more than that of the shoot while water supply had the opposite effect.  相似文献   

6.
The influence of defoliation on the root, stubble and herbage weights of perennial ryegrass during establishment was studied on spaced plants in the greenhouse and field.
In the greenhouse trial the rate of root elongation was reduced by a single defoliation. In both the field and greenhouse, cutting reduced the number of roots and tillers per plant but increased the number of roots per tiller. A few weeks after defoliating plants in the field there was a lower root weight on the cut plants than on the uncut. Eventually the influence of a single cut disappeared, but if the cutting was in the laie summer or autumn the plants commenced the winter with a smaller amount of root and stubble, and this appeared to have a deleterious effect on the earliest spring growth.
Herbage growth in March and April was positively correlated with both root and stubble weights in the previous November.
As the number of cuts during the establishment period (March-November) was increased from 0–4 the root and stubble weight per plant progressively decreased.
The root and stubble weights decreased during the winter.  相似文献   

7.
The effects of soil water conditions and soil temperatures on the growth of grass and clover roots and on the number of new adventitious roots were examined in the field and in glasshouse experiments.
Although significantly more new roots were produced when swards were irrigated during extremely dry periods, the effect was small, In general, irrigation appeared to have little effect on the seasonal pattern of production of new roots from the base of the plant.
High soil temperatures affected root growth. Branching of roots was increased by high temperatures, but the number of new roots formed at the base of the tillers was decreased, and the mean diameter of the roots was decreased. A multiple regression analysis of the number of new roots beneath a unit area of sward with soil-water conditions and soil temperatures at the time of sampling gave a significant inverse relationship with soil temperature. No relationship could be demonstrated  相似文献   

8.
The effect of irrigation on the weight of roots and on the vertical distribution of roots by weight in the soil profile under grass and grass/clover swards was examined in several field experiments.
The weight of root material was less under irrigated swards than under those which were subject only to natural rainfall; it is postulated that this occurred because dead roots decayed more rapidly in the irrigated swards. There was little evidence to suggest that irrigation had any major effect on the vertical distribution by weight of roots within the soil profile.
There was a significant interaction between nitrogen and irrigation; in the un-irrigated swards, root weight decreased with increased N but on the irrigated swards the highest root weight was at an intermediate level of applied N.  相似文献   

9.
大豆根系生长和活性特点的研究   总被引:11,自引:4,他引:11  
孙广玉  何庸 《大豆科学》1996,15(4):317-321
本试验利用框架剖面法测定了大豆根系的生长动态和根系活性变化。结果表明:大豆根系生长过程呈S型曲线变化,形成慢生长(Ve-V3),快速生长(V3-R5)和衰老(R5),三个阶段,高峰值出现在R4-R5阶段。根系活性变化与根系生长特点相似,R1时期之前根系活性逐渐增强,R2时期之后根系活性下降。根系活性变化比根系生长提前。  相似文献   

10.
SOURCES OF VARIATION IN THE IN VITRO DIGESTIBILITY OF TROPICAL GRASSES   总被引:1,自引:0,他引:1  
The in vitro DM digestibility of four tropical pasture species, Cenchrus ciliaris, Chloris gayana, Digitaria spp., Setaria spp. and one temperate grass, Lolium perenne , were studied, using the method described by Tilley and Terry (13).
In vitro digestibility was affected by fineness of grinding, sample size, pH of original rumen fluid and size of rumen fluid inoculum. Different relations were found between the in vivo and in vitro results for the five species, with a maximum predicted difference of 3–5 digestibility units.
It was considered that the in vivo digestibility of tropical grasses could be accurately predicted by this method, provided that the procedure was standardized and samples of known in vivo digestibility similar to those being tested are included in each run.  相似文献   

11.
Normal-acid fibre content has been suggested as a useful indication of the digestibility of herbage. The changes in fibre content were therefore recorded during the spring and early summer of 1957 and 1958 to see whether regular differences occurred between species and varieties of herbage grasses.
All species showed an increase in fibre content during spring and early summer, but considerable year-to-year fluctuations occurred: fibre content was also influenced by manuring and spacing. Regular differences between species and varieties have been detecled and, in perennial ryegrass, differences between individual genotypes. It should be possible to select breeding material for high or low fibre content if required.  相似文献   

12.
Leaf and tiller development along the main shoot of cocksfoot, ryegrass, timothy, Hordeum bulbosum , meadow fescue, S170 tall fescue and an Algerian tall fescue are described. Comparisons between plants grown at two levels of applied nitrogen, and in a heated and an unheated glasshouse, from January to April, 1961, showed that timothy, cocksfoot and, to a lesser extent, H. bulbosum and ryegrass, generally developed leaves faster than the fescues. Numbers of live leaves per shoot, and numbers of actively-elongating leaves per shoot declined in a similar varietal order. Despite this, the large leaves of the fescues resulted in their having a leaf area per main shoot equal to, or exceeding that of, the other grasses for most of the experiment. In general, rate of leaf appearance, number of live leaves, number of actively-elongating leaves and leaf length were increased by a high level of N and high temperature, but high tesnperature reduced leaf width and, in some instances, tiller numbers.  相似文献   

13.
The effects of sowing from 10 to 50 lb/acre of tall-fescue seed on plant establishment and on the annual and seasonal distribution of DM yield of tall fescue and its companion grasses were measured through two growing seasons. Increasing the seed rate increased plant numbers per unit area and decreased per cent establishment. Adding Scots timothy as a companion grass depressed both plant number and per cent establishment. S37 cocksfoot and New Zealand perennial ryegrass reduced both still further. Total annual dry-matter production was relatively unaffected by varying either the seed rate or the companion grass. The contribution of tall fescue to total production was highest when sown alone and was successively reduced by timothy, perennial ryegrass and cocksfoot. When sown alone there were only slight differences in contribution of tall fescue due to seed rate. With any companion grass the contribution from tall fescue increased with increasing seed rate. Early growth was not reduced by modifying seed rate but was reduced by all the companion grasses. It is concluded that increasing the seed rate of tall fescue above 30 lb is not justified, that Scots timothy can be sown at 3 lb/acre with tall fescue without affecting total production or early growth of the mixture, with the advantages of control of unsown species and improved palatability of the herbage.  相似文献   

14.
THE EFFECT OF GROWTH-REGULATING WEEDKILLERS ON THE MORPHOLOGY OF GRASSES   总被引:1,自引:0,他引:1  
A series of experiments were carried out in 1954 and 1955 designed to investigate the effects of MCPA and 2,4-D applied at different stages of growth to grasses grown for seed. Single, spaced plants were sprayed at the rate of 1·5 lb. a.e. per acre with 2,4-D amine in 1954 and with 2,4-D amine and ester and MCPA ester in 1955. The development of the grass growing point was used as a criterion of the developmental stages at which the plants were sprayed.
Some treatments caused abnormal types of growth. S.23 perennial ryegrass and S.143 cocksfoot developed ear malformations, S.53 meadow fescue had leaf and ear malformations, while S.51 timothy showed leaf, stem and ear abnormalities.
Leaf malformations developed only after spraying when the growing points showed vegetative primordia while ear abnormalities usually appeared after treatment at most early stages of development. Stem malformation in timothy occurred after spraying at all stages in 1954, but only at the vegetative stages in 1955.
The percentage of abnormal ears in a random sample of tillers in all but one case fell as the growing point developed and most damage occurred after treatment when the apex was at the vegetative stage. Normally, treatment when glume ridges were visible on the apex produced no significant difference between the number of abnormal ears in the treated and untreated plots.
The results suggest that the chemicals act on that part of the apex which is just beginning its development but is not yet visible as a protuberance on the apex.
The type of abnormalities occurring in grasses as a result of spraying with growth regulating weedkillers is similar to those found in cereals after similar treatment.
Provided that the chemicals are applied in the 4 to 5 weeks prior to ear emergence the amount of malformation occurring in the grasses will be small.  相似文献   

15.
Percentages and yields of N in various grasses and grass mixtures with clover and in associated clover grown at various levels of N application over 5 years are given. Grasses varied consistently in N content, percentages being highest in meadow fescue (cv. S53) and lowest in perennial ryegrass (cv. S24). N application did not significantly affect the N percentage in clover, but the associated grasses had a highly significant effect Percentages were highest in clover associated with meadow fescue and lowest in clover associated with ryegrass. The apparent transfer of N to grass per Ib N in associated clover was calculated for various treatments each year. Reasons for the changing levels of apparent transfer from year to year are considered.  相似文献   

16.
The yield and phosphorus uptake of grasses and clovers from Welsh soils were studied in 6-inch flower pots. Attempts were made to relate the phosphorus that the plants had been able to absorb to various measurements of the labile phosphorus in the soil. It is shown that in these'phosphate fixing' soils, absorption is not related to the exchangeable phosphorus as measured by equilibration. The values obtained for the latter are very high compared with the small amounts of phosphorus that the plants have been able to absorb, giving support to the view that the conversion of phosphorus to insoluble forms is not the main feature of'fixation' in these soils. Absorption of phosphorus by the grass was, however, related to the Larsen (L) values. In previously unfertilized soils, the fact that the L values were also related to the acetic-soluble phosphorus content confirmed the belief that acetic extraction is a suitable means for assessing the abilities of such soils to provide the necessary phosphorus for plant growth. In soils containing reserves of residual phosphorus, however, much of the phosphorus that contributed to the L values was not extracted by acetic acid, and this method of extraction is unsuitable for use with such soils. Placement of the applied phosphorus near the root zone led to a decrease in L values.  相似文献   

17.
Herbage production and quality of swards of brome grass (Bromus carinatus. Hook and Am) were compared with other commonly sown grasses at two sites in Scotland. At Ayr, the comparison was with perennial ryegrass ( Lolium perenne L.), cocksfoot ( Dactylis glomerata L.) and timothy ( Phleum pratense L.) under 6-cut (experiment 1) and 4-cut (experiment 2) regimes over 3 years with 360 kg ha−1 fertilizer N applied annually in each experiment. At Edinburgh, brome grass was compared over 3 years with perennial ryegrass and cocksfoot under a 7-cut system given 3(X)-35O kg N ha−1 year−1 (experiment 3) and with perennial ryegrass, cocksfoot and Italian ryegrass ( Lolium multiflorum Lam.) under a 4-cut system given 250–325 kg N ha−1 annually (experiment 4).
Over the 3 years, brome grass gave 1.18, 6.19 and 1.3% less dry matter (DM) production than the other grasses in experiments 1, 2 and 3 respectively; in experiment 4, it was 1 % less productive than Italian ryegrass but 1.2% more productive than the other grasses. The organic matter digestibility (OMD) of brome grass was lower than that of perennial ryegrass but higher than timothy at Ayr, similar to perennial and Italian ryegrasses at Edinburgh but markedly superior to cocksfoot at both sites. N concentrations in brome grass were higher than in the ryegrasses but lower than in cocksfoot. Mineral composition data showed brome grass to be high in P and K, low in Ca and Mg and very low in Na compared with corresponding concentrations in the other grasses.
The variable performance of this brome grass species ( B. carinatus ) against commonly used grasses in the reported experiments, together with similar evidence from the literature, leads to the conclusion that it is unlikely to be suitable for widespread use in the UK; nevertheless, it has shown some promise in drought-prone situations.  相似文献   

18.
Herbage, stubble and root weights were recorded for thirteen months on various leys subjected to two treatments differing in frequency of cutting.
The root-weight per unit area of a ryegrass/white-clover ley was not affected by the frequency of cutting, but the less frequently cut plots had fewer tillers per unit area; the root- and stubble-weight per tiller was, therefore, higher on the less frequently cut plots, On a cocksfoot ley the root-weight was not affected by the cutting treatment, but in late summer and early autumn the stubble-weight was considerably higher on the less frequently cut plots.
When cocksfoot was grown in rows 2 feet apart, the more frequent cutting decreased both the root- and stubble-weight.
On grass leys root-weights were heaviest in the summer and thereafter decreased until the following spring.
The root-weight of lucerne decreased from May to July, increased to a maximum in December and then decreased in weight. The changes in root-weight under lucerne leys were mainly due to changes in the weight of the tap-roots.
The vertical distribution of roots was recorded, and, in the case of the cocksfoot in rows, the lateral distribution of roots is also given.  相似文献   

19.
The Aberystwyth district experienced exceptionally cold winter weather in 1954, 1955 and 1956, especially during the period from the end of January to early March. Its effect on the grasses, both in the single-plant nurseries and in the agronomic experimental areas, is briefly described.
It was observed that plants which entered the winter carrying a bulk of herbage in a winter-proud condition were at a disadvantage compared with those which had been reasonably grazed or cut back during the autumn. The younger plants were found to be better able than the older ones to withstand extreme conditions.
Suggestions are made as to how some simple-mixture swards can be managed so as to be reasonably likely to provide keep in situ during the difficult months December to April. The species under consideration are cocksfoot ( Dactylis glomerata ), timothy ( Phleum pratense and P. nodosum ), tall fescue ( Festuca arundinacea ), perennial ryegrass ( Lolium perernne ) and Italian ryegrass ( L. italicum ).  相似文献   

20.
A 2-year experiment on competition between sainfoin ( Onobrychis viciifolia Scop.), meadow fescue ( Festuca pratensis ) and tetraploid perennial ryegrass ( Lolium perenne ) was conducted using plants grown in plastic containers outdoors. Root and shoot systems of sainfoin and the grasses were separated in order to investigate full and no competition of root and shoots, at two planting ratios (0·33 grass:0·66 sainfoin and 0·66 grass:0·33 sainfoin). Survival of sainfoin plants was lower at the higher grass:sainfoin ratio. More sainfoin plants died in the winter than during the growing season. Root competition had no effect on survival of sainfoin plants, but shoot competition reduced survival of sainfoin plants during one growing season. Companion grass species had no effect on survival of sainfoin plants, except in the first winter, when fewer sainfoin plants survived when grown with meadow fescue than perennial ryegrass.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号