Effect of herbage mass per unit area and conditioning treatment on herbage drying rate

The rates of drying of herbage, cut from perennial ryegrass (Lolium perenne L.) – dominant swards and subjected to different treatments, were investigated under field conditions by changes in weight of herbage in wire mesh trays in 1995 and 1996. A series of replicated factorial experiments studied the effects, in different combinations, of intensity of conditioning achieved by passing the cut herbage through a laboratory‐scale macerator zero (0C), once (1C), three (3C) or six (6C) times; weight of herbage per unit area equivalent to 450, 675 and 900 g dry matter (DM) m^?2. In one experiment, pressing the herbage to form a mat was incorporated into the experimental design. A further experiment investigated the effect of varying the proportion of conditioned herbage in the herbage mass from 0·00, 0·25, 0·50, 0·75 and 1·00 on drying rate. On each occasion the trays plus herbage were weighed at hourly intervals over an ≈6‐h period and the DM content of the herbage estimated from the change in weight. On all occasions, conditioning and weight of herbage per unit area significantly (P < 0·001) influenced herbage drying rate. Lowering the weight per unit area of both unconditioned and conditioned herbage increased the rate of moisture loss. Unconditioned herbage at the equivalent of a herbage mass of 450 g DM m^?2 had a total moisture loss that was on average 1·5–1·8 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m^?2. Similarly, conditioned herbage at the equivalent of a herbage mass of 450 g DM m^?2 had a total moisture loss that was 1·8–2·3 times greater than unconditioned herbage at the equivalent of a herbage mass of 900 g DM m^?2. Increasing the level of conditioning produced a non‐linear response in rate of moisture loss, consequently 3 passes through the macerator produced >0·95 of the total moisture loss that was produced by 6 passes through the macerator. Increasing the proportion of conditioned herbage in the herbage mass increased rate of moisture loss and consequently final DM content (P < 0·001) although there was little effect from increasing the proportion of conditioned herbage above 0·75. The effects of conditioning and weight of herbage per unit area treatments on total nitrogen , water‐soluble carbohydrate and acid‐detergent fibre concentration of the herbage were small.     

The influence of weather factors on the drying rate of cut perennial ryegrass herbage under controlled conditions

The rates of drying of cut perennial ryegrass (Lolium perenne L.) herbage over short periods of time were measured in four experiments in a controlled environment room. Standard weights of 33·7 g grass dry matter (DM) were placed in half the area of wire‐mesh trays (0·5 m long × 0·3 m wide × 0·07 m high with 11‐mm‐square mesh) which, so as to simulate conditions in a swath, were supported on wooden frames within dark plastic boxes 25 mm above 35‐mm‐thick wet sponges. The trays of grass in the controlled environment room were weighed hourly for 7 h, drying rate being assessed by the change in grass fresh weight. Light was supplied from 400‐W mercury vapour lamps, while an air conditioning unit within the controlled environment room allowed control of vapour pressure deficit (VPD). Only one particular VPD could be created on any one day and resource limitations restricted the study to one replicate per day. The first experiment correlated drying rates under the mercury vapour lamps with drying rates in the open air under sunshine over 3 d. This work showed that a distance of 200 mm between the tray and lamps equated to 1081 W m^–2, 400 mm to 432 W m^–2 and 600 mm to 281 W m^–2. Experiment 2, conducted with previously frozen grass, was a 4 × 4 factorial design with light intensity and VPD as factors. The third experiment (Experiment 3) compared the drying rate of freshly cut grass with grass that had previously been frozen in a 2 × 2 × 2 factorial design with the two grasses, two light intensities and two wind speeds as factors. The final experiment (Experiment 4) was a 3 × 2 × 2 factorial design with light intensity, VPD and wind speed as factors. A wind of approximately 3 m s^–1 was simulated using a 22‐mm, 30 W fan set in a fixed position 600 mm from each tray plus grass. Fresh grass was cut each morning of the experiment. There were six replicates of each treatment. The effect of the three radiation intensities on grass DM concentration in Experiment 2 was highly significant (P < 0·001). VPD had less effect (P < 0·05). Results from Experiment 3 showed that previously frozen material dried much more rapidly than fresh grass and as a result would not simulate actual grass drying in the field. Consequently in Experiment 2 fresh grass was used as opposed to previously frozen material. In Experiment 4, light intensity had the greatest influence on grass drying followed by VPD and wind speed. However, the influence of wind speed was variable. A wind speed of ≈3 m s^–1 increased the rate of water loss from grass with a low initial DM concentration (<160 g kg^–1) receiving low levels of solar radiation (281 W m^–2), while at higher initial DM concentrations (>210 g kg^–1) and higher solar radiation levels (432 W m^–2) the effect of wind was to slow grass drying. The results from Experiments 2 and 4 also indicated that high levels of either wind (3 m s^–1) or VPD (>6 mbars), when associated with low levels of solar radiation, resulted in large increases in grass DM concentration. However, these extreme weather conditions are unlikely to occur in practice.     

中国油菜单产增长要素贡献率分析

运用因子分析技术将影响中国油菜单产的众多因素综合为物质费用、劳动力、政策制度和“结构与灾害”四大因素,并利用Cobb-Douglas型生产函数模型分别测算了四大因素在中国油菜单产增长中的贡献率。根据1990-2004年间的数据计算,物质费用对中国油菜单产增长的贡献率最大,其次是劳动力和政策制度,而同期“结构与灾害”因子对单产有负向影响。     

The influence of trichome density on the drying rate of alfalfa forage

Trichomes decrease water loss in some plant species, but their influence on water loss from alfalfa ( Medicago sativa L.) forage is unknown. A study was conducted which measured the water loss from field-grown, harvested forage of three erect, glandular-haired alfalfa germplasms, KS161, KS210 and KS224, the eglandular 'Arc' cultivar and the 'Kenland' cultivar of red clover ( Trifolium pratense L.). Harvests were taken once in 1995 and 1997, and four times in 1996. Plant height, phenological stage, upper and lower stem diameters, leaf:stem ratio and apical stem densities of simple, procumbent glandular and erect glandular trichomes were determined. The drying rate constants of the forage were calculated by a combination of parametric and non-parametric modelling techniques. The harvest × germplasm interaction was significant for all parameters measured. The density of erect glandular hairs varied among entries for all harvests, while the drying rate of harvested forage differed among entries for three of the six harvests. Correlations between densities of erect glandular hairs and drying rate constants were generally low and non-significant, except for one harvest. Erect glandular hairs, at the densities measured in this study, generally did not influence drying rates of alfalfa forage. However, density of total trichomes was significantly and negatively correlated with drying rate for all alfalfa entries. The diameter of the stem had the greatest negative impact on drying rate.     

The influence of the epidermis on the drying rates of red clover leaf petioles and stems and of Italian ryegrass stems at low water contents

Previous results with red clover ( Trifolium pratense ) leaflets, leaf petioles and stems indicated that the epidermis continued to impose a barrier to water loss at low water contents. Further experiments with red clover leaf petioles and stems suggest that cuticular wax is the epidermal component concerned and that treatments which remove or merely modify this will also increase drying rate. However, when treatments to reduce epidermal resistance were applied to pseudostems and flowering stems of Italian ryegrass ( Lolium multiflorum ) the initial increase in drying rate produced was not sustained at low water contents. The pseudostems consisted of three layers of leaf material rolled one within the other and the true flowering stems were surrounded by one leaf sheath. Their pattern of response to treatments suggested that these affected only the outer sheath, which produced an initial acceleration in drying rate, but that this was not sustained after the outer sheath was dry because the lower untreated layers dried in a similar way to untreated controls.
The results suggest the possibility of devising practical treatments to increase drying rate at low water contents with crops containing a high proportion of leaf or stem not surrounded by leaf sheath. Devising such treatments for crops with a high proportion of grass pseudostem or flowering stem surrounded by leaf sheath will be considerably more difficult.     

A correction for the influence of changes in lamina weight per unit length in grasses on measurements of the weight of lamina removed by grazing

Changes in the weight per unit length along the first and second fully-expanded laminae of Lolium perenne, Agrostis stolonifera, Holcus lanatus and Poa trivialis were experienced in tillers harvested in April and June 1987 from a permanent pasture under contrasting nitrogen treatments. Schematic models representing the weight distribution along the laminae of the different species are presented. From these models, predictions of the weight of any given proportion of the lamina length have been calculated. The weight of segments of lamina have been estimated, using the appropriate lamina model for a species, and these estimates provided consistently greater precision than estimates of lamina weight when no correction for lamina shape was considered, the length of a segment of lamina simply being multiplied by the mean overall weight per unit length of the lamina.     

The influence of the epidermis on the drying rate of red clover leaflets, leaf petioles and stems at low water contents

An apparatus is described which enables excised pieces of plant material lo be weighed al frequent intervals as they dry in controlled conditions of temperature, humidity and air-speed. The effect of removing the epidermis on the drying rate of red clover ( Trifolium pratense ) leaflets, leaf petioles and stems is examined. Initially this treatment caused a very large increase in the drying rate of leaflets. Although the effect declined as water content fell, leaflets from which the epidermis had been removed still dried more rapidly than the controls at a water content equivalent to 50% of the dry weight. Removing the epidermis had a greater effect on the drying rate of leaf petioles and stems at low water contents than it did on the drying rate of leaflets.
Slow drying at low water contents is a major factor responsible for the undesirably long periods for which hay may lie in the field. Slow drying occurs even though swath microclimate becomes more favourable for drying as water content falls. The results presented here suggest that treatments which reduce cuticular resistance have the potential to reduce field drying time.     

Effect of nitrogenous fertilizer on production per animal and per unit area by beef cattle offered similar daily allowances of herbage

An experiment repeated in 3 consecutive years in which 0, 200, 400 and 600 kg ha^?1 fertilizer N was applied annually is described. Cattle on all treatments were offered the same constant daily amount of 2.0 kg herbage DM per 100 kg liveweight above a 3.4 cm height of defoliation. Digestible OM intakes and daily rates of gain were in general not significantly different between treatments. Area required to support these intakes and gains however differed significantly between treatments (P < 0.001) and resulted in high outputs of liveweight gain per hectare on all treatments when compared with other published studies. These outputs together with other actual and theoretical outputs were used to predict optimum fertilizer N applications for grazing beef cattle and the predictions discussed in relation to commercial practice.     

The influence of weather on the effectiveness of mechanical and chemical conditioning on drying rate of lucerne hay

Field drying experiments in summer and winter compared the drying rate of lucerne hay cut with a rotary disc mower and mower-conditioner, with or without 300 1 ha⁻¹ of 2% aqueous potassium carbonate solution sprayed at cutting. Local farm practice was followed in cutting, raking and drying. Statistical analysis showed significant treatment differences in both summer and winter experiments. Mechanical-cum-chemical conditioning treatment provided the greatest field drying rate, followed by chemical conditioning alone, mechanical conditioning alone and non-conditioned luceme, respectively. The effectiveness of mechanical and chemical conditioning treatments was greater in summer than in winter. Under good S.E. Queensland summer conditions, mechanical-cum-chemical conditioning would allow hay to be cut and baled on the same day, but at least 4 days were required under cool winter weather conditions.     

The drying rates of component parts of inflorescence-bearing tillers of Italian ryegrass

Inflorescence-bearing tillers of Italian ryegrass (Lolium multiflorum cv. RvP) were dried in controlled temperature, relative humidity and air speed conditions chosen to be within the range likely to occur in a hay swath drying in the field. After drying for increasing intervals the tillers were separated into inflorescence, exposed flowering stem, leaf-laminae, leaf-sheath and flowering stem enclosed by leaf-sheath and the drying rates of these components in addition to that of whole tillers were measured. There were large differences in drying rate between components, but the differences were similar over the range of drying conditions employed. The drying rate of the inflorescence as well as that of stem enclosed by leaf-sheath was found to be very low and that of leaf-laminae and leaf-sheath very high.     

The effect of the weather on the drying rate of cut diploid and tetraploid perennial ryegrass (Lolium perenne L.) and diploid hybrid ryegrass (Lolium perenne×L. multiflorum)

The drying rate of cut diploid and tetraploid perennial ryegrasses ( Lolium perenne L.) and a diploid hybrid ryegrass ( Lolium perenne × L. multiflorum ), and associated meteorological characteristics, were studied in the field for three successive years: 1988, 1989 and 1990. Meteorological elements measured were: air temperature (at 0·1 in and 1·5 in height), dew point temperature (at 1·5m height), temperature within the grass sward, grass surface temperature, global radiation and wind speed (at 2 in height).
Apart from the weather, the drying depended on the grass species and the yield. Hybrid ryegrass had a lower initial moisture content at cutting in the morning than perennial ryegrass. Also, the hybrid ryegrass dried faster than the perennial ryegrass. Within the same varieties a low yield dried faster than a high yield. Frequent tedding did not influence the rate of drying. The temperature within the grass swath approached the air temperature at 1·5 m. The grass surface temperature was greatly affected by global radiation. Increasing wind speed had an adverse effect on the drying rate of grass.     

The influence of vernalization on response to nitrogen of perennial ryegrass

Vernalized and unvernalized perennial ryegrass (Lolium perenne cv. Gremie) tillers planted in microplots in a glasshouse in April 1974 and 1975 were exposed to natural daylength thus inducing vernalized plants to produce reproductive, and unvernalized plants vegetative growth. Nitrogen was applied at 0–30 g m^?2 (to 24 g m^?2 in 1975) to both types of herbage. At the first defoliation in each year yields from vernalized grass were greater than those from unvernalized grass; subsequently differences were minimal or reversed. Vernalization had no significant effect (P > 0.05) on total yields over four defoliations in either year. Apart from the first cut in 1974 nitrogen application increased dry matter yields of both types of herbage. Tiller numbers were usually increased by the lowest level of nitrogen application but at higher levels the effect was variable. There was no evidence of an interaction effect of level of nitrogen application and vernalization on dry matter yields.     

The influence of climatic factors on physiological development in perennial ryegrass

Dates of initiation of reproductive development and of ear emergence were determined for four cultivars of perennial ryegrass (Lolium perenne) representing a range in maturity from early to late in a single trial in 1977. The influence of climatic factors upon the reproductive development was investigated and it was found that, while day-length largely influenced the dates of initiation, subsequent growth and development towards ear emergence was influenced mainly by temperature. The data indicated that cultivars may have similar requirements in terms of accumulated temperature between the physiological growth stage of initiation and the agronomically significant growth stage of ear emergence. The possibility of achieving greater accuracy in forecasting ear emergence dates by relating meteorological data to the physiological development of the individual cultivars is suggested.     

Impact of seeding rate on annual ryegrass performance

Annual ryegrass (Lolium multiflorum Lam.) is a primary forage resource for livestock producers throughout the south‐eastern USA during the winter‐growing season. It is important for livestock producers to begin grazing annual ryegrass as early as possible and any management practices maximizing early season production could be beneficial. To assess the impact of seeding rate on subsequent yield, yield distribution, quality, seedling density, and end‐of‐season plant and tiller density, a 2‐year study was initiated at four locations in Louisiana. Three annual ryegrass cultivars, varying in seed size, were established at four seeding rates based on pure live seed (PLS) rates of 400, 800, 1200 and 1600 PLS m^?2. There was no advantage in total yield from increasing seeding rates beyond 800 PLS m^?2. However, first‐harvest yields increased from 360 to 930 kg dry matter (DM) ha^?1 as seeding rate increased from 400 to 1600 PLS m^?2. Crude protein and neutral‐detergent fibre concentrations, and in vitro DM digestibility, were not affected by seeding rate. Seedling density and end‐of‐season plant numbers increased as seeding rate increased. However, stems per plant decreased as seeding rate increased, indicating compensatory tillering for the reduced plant numbers observed at the lower seeding rates. These results indicate first‐harvest yield can be increased by planting at higher seeding rates but total yields are not increased.     

云南省冬大豆高产栽培技术

冬大豆产量受品种生产能力，环境条件，栽培技术水平的综合影响。选出高产优质品种“661”，应用大豆高产理论与技术，以增加单位面临株数，提高单棉英粒数和粒重为原则，利用热区冬春光热资源，在栽培上采取适宜的技术，创造了单产268.14kg/667m^2的云南省冬大豆单产最高纪录，为冬大豆高产提供了科学依据。     

The effect of drying temperature on in vitro dry-matter digestibility and water-soluble carbohydrate content of perennial ryegrass varieties

In official forage grass variety trials in the UK, herbage samples are dried at 100°C or more to facilitate quick drying of the large numbers of samples that are currently needed. When assessing herbage quality, however, 80°C has been recommended as the highest temperature that can be used during drying without serious deterioration. Herbage from six perennial ryegrass varieties, which were known to show a range of variation in in vitro concentration of digestible dry matter (DMD) and water-soluble carbohydrate concentration (WSC) during the vegetative phase of growth, was dried in an oven with forced ventilation at 100°C and at 80°C before analysis. Mean DMD over all varieties was slightly lower [6 g kg⁻¹ dry matter (DM)] and mean WSC over all varieties was considerably lower (24 g kg⁻¹ DM) at 100°C. Varieties differed in mean DMD over both drying temperatures by 37 g kg⁻¹ DM and in mean WSC by 63 g kg⁻¹ DM. There was, however, no significant interaction between variety and drying temperature for either DMD or WSC. Although drying at the higher temperature underestimated both DMD and WSC, it did not significantly alter the ranking of varieties or the range among them.     

优化良种与良法单产籽棉超千斤

彭泽县是全国优质棉生产基地县 ,也是江西省重点产棉县之一 ,棉花的辉煌 ,曾经带来县域经济的繁荣 ,随着市场经济的不断增强 ,我国已加入ＷＴＯ ,经济全球化 ,传统的产业结构被打破 ,植棉效益受到了挑战和冲击 ,在此情况下 ,如何寻找棉花经济新的增长点 ?作者从优化良种与良法着手 ,从中棉所引进良种进行试种比较、示范推广 ,通过近五年的示范推广 ,2 0 0 1年彭泽县种植中棉所 2 9面积达 30 0 0余公顷 ,在种植过程中 ,由于认真实行了规范化模式栽培 ,出现了大面积产籽棉 375 0ｋｇ·ｈｍ- 2 以下很少见 ,4 80 0～ 5 2 5 0ｋｇ·ｈｍ- 2 很普…     

Photosynthetic rate and carbon balance of grazed ryegrass pastures

The relationship between net canopy photosynthesis (Pnc) measured at 400 J m⁻² s-¹ and leaf area index (LAI) was determined on ryegrass-dominant swards over a range of her bage masses in five grazing experiments. In three experiments the swards were continuously stocked either by sheep or by cattle to maintain a number of herbage heights and hence LAI values. In two experiments the swards were intermittently grazed with 21 -d regrowth intervals. On the continuously stocked swards measurements were made over nine periods each of 7 to 21 d in length. On the intermittently grazed swards measurements were made over six periods while the herbage was being grazed down from a high to a low LAI and over three periods during the regrowth phase.
On all the swards where measurements were made while grazing was in progress, the relation of Pnc to LAI was linear. The photosynthetic rate was greater on the continuously grazed than on the intermittently grazed swards up to LAI 35 and in two experiments to LAI 5. The relationship of Pnc to LAI of swards in the regrowth phase was predominantly curvilinear and such that over much of the LAI range they had a greater photosynthetic potential than the same swards being grazed down from high to low mass. Daily rates of CO₂ uptake and growth in the field were calculated for one continuously stocked experiment. Both were linearly related to LAI in the range LAI 2–4·5. The agronomic implications of the results are discussed.     

Varietal differences in tiller and panicle development determining the total number of spikelets per unit area in rice

ABSTRACT

Rice varietal differences were compared between japonica type (JAT) and indica type (INT) and between panicle number type (PNT) and panicle weight type (PWT) in terms of tiller and panicle development. Rice varieties PNT-JAT Hinohikari, PWT-JAT Akenohoshi, PNT-INT IR36, and PWT-INT Takanari were used in the field experiments. Tiller bud formation and tiller leaf emergence occurred slightly later in the PWT than in the PNT varieties. These parameters occurred slightly earlier in the INT than in the JAT varieties. The maximum number of tillers was greater in IR36 than in Takanari, Hinohikari, and Akenohoshi. The number of panicles per unit area (PN) was greater in IR36 and Hinohikari than in Akenohoshi and Takanari. The widths of the shoot apical meristem (SAM) just before panicle initiation were in the order of Akenohoshi > Hinohikari = Takanari > IR36. The number of spikelets per panicle (SN) was in the order of Takanari = Akenohoshi > IR36 > Hinohikari. In conclusion, the PWT varieties, which had relatively wider SAM, presented with the promotion of main shoot development and the suppression of tiller development. Consequently, PN decreased and SN increased in PWT varieties. INT varieties presented with the promotion of tiller and rachis branch development, which resulted in increases in both PN and SN. These developmental factors may determine varietal differences in the total number of spikelets per unit area.