THE INFLUENCE OF LIME, LIME PELLETING, AND METHOD OF SOWING ON THE NODULATION AND GROWTH OF SUBTERRANEAN CLOVER

Lime pelleting of subterranean clover improved nodulation and growth during the establishment period. Lime improved nodulation slightly and increased herbage production. Drilling reduced nodulation slightly compared with broadcast sowing, unless the seed was pelleted or sown with lime.     

THE RESPONSE OF SOME HILL PASTURE TYPES TO LIME AND PHOSPHATE

A study was made of the responses of four upland soil- and vegetation-types to applied lime and phosphate in the north of Scotland. Light and heavy dressings were used, the former at a rate which might be economically considered for aircraft application. Two experiments were laid down on graminaceous communities and two on contrasting types of Callunetum. The low rate of lime produced little measurable soil response, whereas the high rate induced marked and persistent effects. In terms of botanical response, however, the high rate of liming showed little advantage over the low rate in the presence of phosphate at the two grassland sites. Only very minor vegetation effects were observed at the Calluna centres, particularly where the community was in the mature stage. The results emphasize the importance of an ecological approach to upland pasture improvement, involving a knowledge of the specific responses of different plant communities to fertilizer application, combined with an appropriate measure of stock control.     

大豆萌动种子及株体对渍水环境的反应

渍水(种子上3cm水层)条件下,萌动种子活力的受害程度、临界时间与温度有关,相对高温下,种子受害加速,受害临界时间也提前。大豆生育的不同阶段根际渍水,产量均有大幅度下降。供试22个大豆品种(品系)在V_3、R_1、R_3和R_5期开始渍水15天的平均结果,分别减产35.1、40.2、38.3和36.9％。营养生长阶段渍水,株高下降、茎重减少,健壮“骨架”形成受阻造成单株粒数减少。开花期渍水,大量落花和成荚率减少影响单株粒数。结荚阶段渍水,因大量落荚,而影响单株粒数。鼓粒期渍水,一是开始鼓粒的种子因停止其发育而造成秕粒,二是鼓粒旺期的种子生长受阻而百粒重严重下降。总之,V_3、R_1、R_3和R_5期开始渍水的处理,减产均与其单株粒数的减少呈显著正相关。相关系数(r)分别为0.957、0.935、0.930和0.480。渍水还造成大豆对根际缺氧环境的适应性变化:如水中茎的增粗、大量增生气生根。随着气生根的生长发育,地上部,尤其是叶色逐渐有所恢复。大豆萌动种子受害临界及生育期根际渍水,对产量的胁迫存在着显著的品种间差异。品种内时间不同生育期的耐渍水性也不一致,这就给选育耐渍水大豆材料提供了成功的可能。     

NAA和2,4-D对脱毒马铃薯扦插苗生长及产量的影响

本文研究了不同浓度NAA和2,4-D配合使用对马铃薯扦插苗的生根、生长及产量的影响。结果表明,6种处理中,其中浓度为NAA5mg／l,2,4－Dlmg／l的处理扦插苗生根数多,成活率高,植株长势强,产量最高。     

LIME AND PHOSPHATE TREATMENTS FOR RECLAMATION OF HEATHER MOORLAND

The use of lime and phosphates in reclaiming heather moorland was investigated in two experiments.
Large initial dressings of hme resulted in a rapid rise in pH. An initial dressing of 9 tons CaCO₃/ac resulted in a more rapid rise to pH 6 than did 6 tons/ac and the soil was maintained above pH 6 for a longer period. Three annual dressings of 3 tons/ac gave a slower rise in pH and a longer period above pH 6. Split treatments, half before and half after the first ploughing, gave no long–term advantage where a programme of pioneer cropping was being followed.
Basic slag and North African phosphate were as effective as superphosphate for root crops at low pH values. Basic slag was as effective as superphosphate for grassland establishment and gave a greater rise in soil phosphate. North African phosphate was virtually worthless as a source of phosphate for establishing grasses and clovers, and gave a negligible rise in soil phosphate.
Given adequate supphes of lime and phosphate, frequent small apphcations of N over the first 2 or 3 years are vital to the success of a reclamation programme under the conditions described.     

THE PROBLEMS OF RELATING GREENHOUSE AND CONTROLLED ENVIRONMENTAL WORK TO SWARD CONDITIONS

When the rate of dry-matter production of a grass crop is determined only by the incoming light energy, it increases exponentially until a closed green surface is reached. Thereafter the production is linear for some time, but soon it decreases and finally drops to zero. This decrease is partly caused by an increase in the rate of respiration relative to photosynthesis. However, there are still unknown factors affecting the rate of production, especially in the second half of the season. When a sward receives an optimal supply of water and nutrients the organic plant constituents at a given growth stage remain fairly constant throughout the season. It would be advantageous, however, to harvest grass with a higher sugar and a lower protein content. This seems to give better rumen digestion and, besides, would improve the regrowth of the sward. Since plants with a high rate of dry-matter production usually have a fairly low reserve level, it is unlikely that selection could provide a strain with both a high reserve level and a high rate of production.     

氮肥对大豆不同类型品种结瘤固氮影响的差异性研究

本研究选用生育期和蛋白质含量不同的六个夏大豆品种，在磷钾肥基础上施用三个氮肥水平（０、６、１２ｋｇ氮／亩）。结果表明：施氨抑制结瘤，氮肥越多抑制越严重；抑制作用主要在盛花期前，至鼓粒期有的品种受抑制作用较小；对固氮的抑制在不同品种间存在明显差异，品种豫豆８号表现出较耐氮。酰脲相对丰度与根瘤干重极显著正相关，六叶期、盛花期和鼓粒期两者的相关系数分别为ｒ＿ａ＝０．９５４５、ｒ＿ｂ＝０．８０２５、ｒ＿ｃ＝０．６５３１，Ｐ＜０．０１。酰脲的相对丰度反映了品种的固氮差异和不同氮肥水平下固氮的变化。     

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。     

淹水大豆的生长与固氮研究

试验于1989年7月至10月在泰国清迈大学农学院多熟制研究中心的农业试验场进行。在淹水栽培与常规栽培条件下,对二个大豆品种SJ5和NW1的生长与产量、根瘤生长与固氮率和固氮量及其对增施每公顷50kg氮素肥料的反应进行测定。结果表明,淹水能促进根瘤生长,增加固氮率、比常规栽培法多固定氮素44％以上。但是淹水栽培法对干物质和产量的增加并不显著。增施氮肥能防止淹水初期的植株落黄现象,但抑制根瘤生长和固氮。     

磷肥配施石灰石粉对红壤上大豆生长和养分吸收的影响

通过红壤上石灰石粉与磷肥配施对盆栽大豆生长和养分吸收影响的研究表明,施石灰石粉、钙镁磷肥均能提高土壤pH,显著增加大豆的产量,提高其养分的转运率;施石灰石粉能提高植株含钙量,却抑制了对钾的吸收,施磷肥提高植株含磷量,但降低植株含钙量。     

THE GROWTH AND DEVELOPMENT OF SOME GRASS SPECIES UNDER COMPETITIVE STRESS

Three experiments were carried out in a semi-controlled glasshouse environment to determine the response of individual plants to competition; (i) between seedlings of different species, (ii) between seedlings derived from seeds of differing sizes within a species, and (iii) between seedlings and established plants.
Differences were detected in seedling competitive ability between species and between plants derived from differing seed sizes. In associations of species of very high and very low competitive ability the differences in competitive ability were accentuated by an increase in plant density.
Established plants of Phalaris coerulescens were less aggressive to seedlings growing in close proximity than were plants of Lolium rigidum and H1 ryegrass. Despite the early death of established swards of L. rigidum , and the consequent removal of competitive stress, there was no rapid increase in the growth and development of seedlings in these swards. Possible mechanisms causing this effect are discussed.
There was evidence of a specific relationship between the species of the established sward and the seedling species, in particular seedlings of HI ryegrass were particularly susceptible to competition from established plants of their own species.
Dry weight per plant, tiller production, rate of leaf appearance and leaf size were ail affected by competition between seedlings; however, tiller production was generally more severely affected than rate of leaf appearance and leaf size.
Dry weight per plant, tiller production, seedling height, number of leaves per tiller and number of seeds per seedling were all affected by competition from established plants.     

THE GROWTH AND DEVELOPMENT OF SOME GRASS SPECIES UNDER COMPETITIVE STRESS

Two pot experiments were carried out in a semi-controlled environment to examine the response of individual plants to competitive stress in simple systems incorporating varying cutting frequencies and soil–nitrogen levels. A third experiment was set up outdoors to examine the effect of competition on individuals in an association, on the association as a whole, and to extend the controlled environment studies to a more complex model involving micro-plots.
Phalaris coerulescens , although its seedlings possessed a high competitive ability, showed a dramatic decline in competitive ability in later stages of the association, this decline being associated with extensive floral development. In micro–plots the effect of competition was so severe as to prevent the expression of seasonal growth characteristics by P. coerulescens .
Considerable inter-specific differences existed in the response to competition of leaf-area production per tiller during periods of regrowth.
Whilst P. coerulescens remained highly productive and maintained a dense tiller population in monocultures, its tiller regeneration following flowering was severely suppressed in competition with vegetative plants of HI ryegrass or Festuca arundinacea .
The number of heads produced per plant, head length and time of head emergence were all affected by competitive stress, the former response being a reflection of the relative competitive abilities at the time of floral initiation. The response of the latter two characters reflected the decline in competitive ability which occurred during later stages of the growth and development of P. coerulescens .     

THE GROWTH AND DEVELOPMENT OF SOME GRASS SPECIES UNDER COMPETITIVE STRESS

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.     

THE INFLUENCE OF NIGHT GRAZING ON THE GROWTH RATES OF ZEBU CATTLE IN EAST AFRICA

Results are reported from a 10-month trial, using 50 oxen, in which growth rates of groups receiving restricted and normal night grazing were compared. The resiriction of night grazing was found to lead to a significant decline of 30% in live-weight gain. This difference was largely attributed to periods of moderate grass shortage (i.e. marginal day grazing) when those animals with the longer grazing period were able to select a diet of superior quality and quantity. Under good, or very bad, grazing conditions the availability of night grazing did not appear to be critical.     

平衡施肥对重茬大豆幼苗生理及生长的影响

平衡施肥能改善重茬大豆幼苗的生理性状，使大豆主根长培养，侧根数增多，根系活力增强，总根长增加、叶面积增大，叶绿素含量增加，光合作用增强，大豆地上，地下部干重显著增加，NPK与多元微肥配合施用效果最佳。     

不同阶段施用氮肥对大豆氮吸收及固氮的影响

以两种不同基因型的大豆品种为试材，研究不同阶段施用氮肥对大豆吸氮及固氮的影响。试验结果表明，氮肥的施用时间对大豆氮吸收、根瘤干重及固氮，具有重要影响。仅施２５ｋｇ／ｈｍ２的启动氮，两个大豆品种都获得了最高的根瘤干重和固氮率。在开花期或种于形成初期，再追施５０ｋｇ／ｈｍ２氮，两个大豆品种都获得了最高的氮吸收总量和固氮总量。大豆的根瘤干重与固氮率呈线型正相关。     

INFLUENCE OF DRYING AND STORAGE CONDITIONS ON NONSTRUCTURAL CARBOHYDRATE ANALYSIS OF HERBAGE TISSUE—A REVIEW

No one method of drying can be relied upon for all plant species, plant parts, or form (e.g., fresh v. ensiled herbage). Least changes in nonstructural carbohydrates appear to occur when fresh tissue is immersed in boiling alcohol. Freeze-drying provides results more similar to fresh tissue than heat-drying. Heat-drying at high temperatures (above 80°C) can cause thermo-cbemical degradation, while slow drying at low temperatures (below 50°C) allows time for DM losses by respiration and enzymatic conversions. The most acceptable heat-drying results have been obtained by drying for a short time at a high temperature (i.e. 100°C) and thereafter at a moderate temperature (i.e. 70°C). Changes in nonstructural carbohydrate concentrations occur during the storage of either freeze- or heat-dried tissues. Thus, analyses should be conducted as soon as possible after tissue sampling. The least changes occur during storage in alcohol, following killing of the tissue in boiling alcohol.     

THE EFFECT OF HEIGHT OF CUTTING ON THE SUBSEQUENT GROWTH AND YIELD OF LUCERNE

Three experiments designed to test the effect of height of cutting of lucerne on subsequent yield are described and the results discussed. Extremely low cutting, at ground level, can cause the death of individual lucerne plants, but if such extreme cutting is avoided there is no evidence to show any advantage in leaving a long stubble. In fact, in a sward, the lower the cutting the greater is the yield to be expected.