Showing papers on "Sowing published in 1985"

Time, Temperature and Germination of Pearl Millet (.Pennisetum typhoides S. & H.)

Abstract: Seeds of pearl millet were germinated on wet filter paper at temperatures up to 50 °C. In one experiment, the temperature was held at 50 °C during imbibition and was then lowered to 32 °C or 25 °C. Germination rate and the maximum fraction of seeds germinating (Gm) both decreased as the time of exposure to 50 °C increased. In contrast, exposure to 50 °C after imbibition for 8 h slowed germination but did not significantly reduce Gm. When the 'high' temperature imposed after imbibition was reduced from 50 °C to 45 °C, there was a small reduction in the rate of germination but not in Gm. The responses have implications for the optimum time of sowing in the tropics when maximum daytime soil temperature at the depth of sowing is in the range of 45-50 °C.

Time, Temperature and Germination of Pearl Millet (Pennisetum typhoides S. & H.): III. INHIBITION OF GERMINATION BY SHORT EXPOSURE TO HIGH TEMPERATURE

Abstract: Seeds of pearl millet were germinated on wet filter paper at temperatures up to 50 °C. In one experiment, the temperature was held at 50 °C during imbibition and was then lowered to 32 °C or 25 °C. Germination rate and the maximum fraction of seeds germinating (Gm) both decreased as the time of exposure to 50 °C increased. In contrast, exposure to 50 °C after imbibition for 8 h slowed germination but did not significantly reduce Gm. When the 'high' temperature imposed after imbibition was reduced from 50 °C to 45 °C, there was a small reduction in the rate of germination but not in Gm. The responses have implications for the optimum time of sowing in the tropics when maximum daytime soil temperature at the depth of sowing is in the range of 45-50 °C.

Variation in development of wheat and barley in response to sowing date and variety

Abstract: A number of commercial varieties and advanced breeding lines of wheat and of barley were each sown successively in the field from early in September until late in February in 3 or 2 years. Shoot apex development was monitored throughout the growing season and the dates at which the double ridge stage and the terminal spikelet stage were attained are reported. There was considerable variation in the date at which these stages occurred, associated both with variety and date of sowing. When sown early, spring wheat varieties and the winter wheat, Fenman, developed more rapidly than the other winter wheats, but the difference disappeared in sowings made in the middle of October or later. Spring barley developed more quickly than winter barley and the difference persisted until sowings made in mid-November.Length of the longest leaf sheath, number of emerged leaves on the main shoot and the time when stem elongation began (‘ear at 1 cm’), plant characters used to assess the stage for various agronomic treatments, were measured in parallel with apex development. The relationships between number of emerged leaves and the length of the longest leaf sheath and stage of development were found to vary with sowing date. The stage ‘ear at 1 cm’ provided a good guide to shoot apex development. Stem length and number of elongated internodes varied with date of sowing. Some of the variation in number of emerged leaves at a given stage and in the final number of elongated internodes was found to be correlated with total number of leaves on the main shoot. The form of analysis used indicated that sowing date may have important effects, via its effect on the number of leaves on the main shoot, on the duration of ear growth in wheat and barley and on the duration of ear formation in barley.

Changes in the weed flora of an arable field cultivated for 20 years.

Abstract: (1) Changes in the weed flora of Boddington Barn field were monitored during 20 years of arable cropping after being ploughed out of grass in 1960. Seedlings were identified and counted in spring in a regular grid of 151 quadrats (0.1 IM2) in 14 of the 20 years. (2) The number of species recorded ranged from twenty-three to fifty-three. The maximum number occurred after 4 years of cultivation. Grassland weeds did not persist long under continuous arable cropping, though Trifolium repens survived the whole 20 years. Ranunculus bulbosus survived 14 years, Rumex obtusifolius 12 years, Plantago lanceolata 8 years and, of the thirteen other species recorded, nine had become extinct by 5 years. (3) When the permanent pasture was ploughed in 1960 two overlapping areas of the field yielded contrasting arable weeds. One area, probably cultivated sometime between 1940 and 1945, was characterized by Fumaria officinalis, Aethusa cynapium and four other weeds: seeds of these species evidently survived 15-20 years in the soil. The other area which had been cultivated sometime between 1949 and 1960 was characterized by Papaver rhoeas and three other weeds. (4) Mean seedling density increased over the period from 29 m-2 in the first arable crop to 196 m-2 after 20 years. (5) The season of planting the crop was one of the most important factors determining the weed flora composition in any year. Spring-germinating weeds predominated in spring-sown crops and autumn-germinating weeds in autumn-sown crops. The introduction of weeds in contaminated crop seed was another important factor though other species invaded temporarily by windborne seed.

Germination and seedling growth of prairie grass, tall fescue and Italian ryegrass at different temperatures

Abstract: We measured the effects of temperature on the germination, emergence and growth during early tillering of Italian ryegrass (Lolium multiflorum), prairie grass (Bromus catharticus) and tall fescue (Festuca arundinacea) Radicle emergence (the percentage of seeds with emerged radicles) and 'field' emergence (the percentage of seeds with shoots > 1 cm long) were reduced at 35¦C (constant, all lines), or 30/25¦C (12/12 h, prairie grass and Tama Italian ryegrass only) All lines took longer to germinate at 15 and 10¦C (constant) than at higher temperatures, and final percentage germination of tall fescue lines was lower at 10¦C (constant) than at other temperatures Italian ryegrass had the fastest shoot extension, and consequently the fastest 'field' emergence Seed respiration rates were higher in fescue than in the other lines at 4 days from imbibition, and rates rose in all lines at 8 days Over the first 20 days after sowing, growth rates were closely related (r = 087-099) to weights of seed and caryopses, when account was taken of perenniality (which was associated with relatively slow growth) and polyploidy (which was associated with growth faster than might be expected from seed size alone), and a multivariate relationship including temperature was developed (R2 = 088) Growth rates of shoots at 20 days after sowing were ranked Tama Italian ryegrass > prairie grass > Ucivex Italian ryegrass > tall fescue, and 24/19 > 21/16 > 18/13 > 30/25 > 15/10¦C Growth during tillering, up to 42 days after emergence, was ranked Italian ryegrass > prairie > tall fescue and 21/16 = 18/13 > 24/19 = 15/1O¦C Relative growth rates and relative rates of tillering were independent of temperature in Italian ryegrass, but were lower at 15/10 and 24/19 than at 21/16 and 18/13¦C in prairie grass and tall fescue Prairie grass had higher yield per tiller but lower tiller numbers than Italian ryegrass; tall fescue had both lower yield per tiller and lower tiller number Italian ryegrass was therefore the species best adapted to variations in environment and competition at sowing

Some factors limiting the growth and yield of winter wheat and their variation in two seasons

Abstract: Multi-factorial experiments on winter wheat cv. Hustler in autumn 1979 and 1980 sown on a clay loam soil following potatoes tested the effects of combinations of the following eight factors, each at two levels: sowing date; amount of nitrogen; division of nitrogen; timing of nitrogen; irrigation; autumn pesticide (aldicarb); summer aphicide (pirimicarb); and fungicide (carbendazim, tridemorph, maneb and captafol). The mean grain yields of all plots in 1980 and 1981 were respectively 9·6 and 8·3 t/ha; the best eight-plot means were 11·2 and 9·9 t/ha. Fungicides had the largest effect on grain yield, increasing it by 0·8 and 1·7 t/ha in 1980 and 1981, mainly by increasing grain size. Effects were greater with earlier sowing and the larger amount of nitrogen. Benefits from fungicide were well related to the control of leaf diseases, mainly Septoria spp., which became severe after anthesis. Fungicide temporarily decreased the number of saprophytic fungi on the developing ears. Aphids that appeared in autumn on plots sown in mid-September were controlled by autumn pesticide, which also prevented the spread of barley yellow dwarf virus that occurred only in 1981. Consequently, yield of early-sown plots in 1981 was increased by autumn pesticide, but only when the severe infection with leaf diseases was controlled by fungicide. Autumn pesticide decreased nematode populations. Aphid populations in summer were small and yield was unaffected by the decrease in numbers that followed application of an aphicide. Sowing on 20 or 15 September, as compared with 19 or 30 October, caused faster growth and development and greater uptake of N from the soil early in the season. Effects were smaller after April: earlier sowing increased total dry weight by 2·5–3·0 t/ha and, when leaf diseases and barley yellow dwarf virus were controlled, increased yield by 0·9-l·0t/ha. Increasing the amount of N applied by 70 kg/ha (from 105 or 80), increased yield only in 1980 and then only when fungicide was used. Extra N decreased yield in 1981 in the absence of fungicide. Extra N always increased N uptake and decreased grain size. Applying most or all of the Non 4 or 19 March instead of 15 or 23 April resulted in less uptake of N from anthesis onwards and smaller yield, especially in 1980. N in three applications instead of one had negligible effect. Trickle irrigation decreased yield slightly, despite delaying leaf senescence and increasing straw weight. Attributes of wheat on best yielding plots differed little between years. Average values were: 534 ears/m2; 40·7 grains/ear; 40·4 mg/grain; 18·8 t/ha total dry matter and 214 kg N/ha uptake by grain plus straw.

Morphology and growth in seedlings of several C4, perennial grasses.

Abstract: Establishment of forage grasses depends upon their ability to compete for resources in the critical seedling establishment phase. Desirable native grass species are generally considered to be more difficult to establish from seed than the introduced Old World bluestems (Bot~ocUut spp.), although comparative data are generally lacking. This study compared the responses of morphological attributes commonly associated with seedling vigor and some growth parameters in 17 perennial, C4 grasses including 5 native and 12 Old World bluestems. Plants were grown in a greenhouse under well-watered and limited watering regimes. The objective was to document differences in morphology and growth among these grasses from emergence through 7 weeks post emergence. The Bothriochloa species generally rated higher than the native species in morphological characters commonly associated with seedling vigor. The exotics produced as much or more biomass and had more leaf area per plant, more tillers, and leaves per tiller than the natives. Although the native grasses produced less leaf area, the cost of these leaves in terms of biomass per unit area was higher than in the introduced grasses. The natives tended to partition relatively more biomass aboveground and more of this to leaves, rather than sheaths plus stems, than the Old World bluestems. However, partitioning of total plant biomass among roots, sheaths plus stems, and leaf blades was remarkably insensitive to water stress in all entries. Approximately one-third of total biomass was partitioned among kaf blades, sheaths plus stems, and roots, respectively, with sheaths+stems tending to be a slightly smaller fraction than the other 2 components. Recurring water stress cycles reduced most parameters significantly and generally accentuated the normal ontogenetic decline in relative growth and unit rates. Across all entries, total plant biomass and leaf blade area were reduced over 4m by a limited watering regime. Although water stress reduced the size of the assimihttory surface, the remaining leaves were more effkient in the production of new biomass. This response correlated with an increase in specific leaf weight under water stress. Successful establishment of forage grasses from seed depends on numerous environmental factors (see Vallentine 1980) which interact with the plant’s genetic component during germination, emergence, and post-emergence growth. Plant vulnerability to environmental stresses is particularly high during seedling establishment because of limited food reserves (Johnson 1984) resulting from small seed size and limited photosynthetic capacity. The amount of food reserves stored in the endosperm is an important factor related to establishment potential (Davies 1967). Also contributing to this vulnerability is the lack of a well-developed root system. Frequently, competitive advantages gained during the seedling stage are maintained in the mature plant stage (Johnson 1984). Variability in establishment success among species and genotypes within species is common knowledge, and high success is often associated with rapid germination, rapid root and top growth, a robust growth habit, and resistance to stress (McKell 1972). These traits are collectively referred to as seedling vigor. Numerous techniques for assessing seedling vigor have been developed (reviewed by Whalley and McKelll973) and much effort has been expended to enhance vigor in forage plant germplasm (Kneebone 1972). Thirty years of research have shown that selections from the Authors are plant physiologists, USDA-AR& Southern Plains Range Research Station, 2000-18th Street, Woodward, Okla. 73801. C.L. Dewald provided the plant materials used in this study. Tom Popham and George Hilton are acknowledged for their assistance with the statistical analyses. Manuscript accepted March 13, 1985. genus Bothriochloa (Asiatic or Old World bluestems) can contribute significantly to beef production and soil conservation in the Southern Great Plains (Sims and Dewald 1982). The Old World bluestems have been found to exhibit relatively high seedling vigor at Woodward, Okla. in comparison with native species (C.L. Dewald, pers. comm.). Harlan et al. (1958) noted that ecologically, the Old World bluestems are best fitted to some stage of secondary succession and that they tend to increase under grazing pressure. They also noted that these grasses reproduce freely by seed, tend to be somewhat weedy, and are generally easily established in plantings. Experience has shown that establishment of stands of climax, decreaser species in the Southern Plains usually requires 2 growing seasons while only 1 is required to establish the Old World bluestems. Of the 3 phases of seedling establishment (germination, emergence, postemergence growth), it was felt that a manager would have least control over the last phase since high quality seed, proper seedbed preparation, and timing of planting with periods of soil moisture sufficient to ensure germination would reduce the risk associated with phases I and 2. Therefore, phase 3 was isolated for study. The objective of the study was to determine differences in morphology and growth behavior among 5 native and 12 Old World bluestem perennial forage grasses from emergence through I2 weeks post emergence under near optimum conditions which could be used as indices of comparative performance potential. Because post-emergence failure is frequently associated with drought stress (Vallentine 1980, Whalley and McKell 1973) and because drought conditions can be prevalent during the normal period for establishing warm-season grasses, a suboptimal soil water treatment was included to assess relative departure of the measured parameters from potential. Materials and Methods Plant Materials and Culture Seventeen perennial, warm-season grasses, including 5 native and 12 exotic Old World bluestems, were included in this study (Table 1). Woodward sand bluestem is a leafy grass of medium height with good seed production characteristics. Hachita blue grama is a relatively tall and productive selection compared to blue grama selections in general. Two switchgrass varieties were included: one is a robust upland type (Caddo), and the other (Kanlow) is adapted to lowland sites. Western indiangrass is an experimental strain selected for ease of establishment and it has low dormancy and rapid emergence compared to other indiangrass cultivars such as Cheyenne and Osage. The Old World bluestems included 3 species. B. cuucusicu and B. intermediu have secondarily branched inflorescences, B. ischuemum does not. B. cuucusicu has a relatively small crown diameter (basal spread) compared to the other.2 species.‘B. cuucusicu, B. intermediu var. indicu and B. ischuemum var. ischuemum exhibit early seed maturity compared to B. intermediu var. montunu. A gradation of leaf widths is present in these grasses. Wide-leaf types include B. intermediu var. montunu. medium-leaf types include B. cuucusicu and 8. ischuemum var. ischuemum. while B. intermediu var. indicu is composed of narrow-leaf types. WW-477 is an introgression between the B. intermediu and B. ischuemum and has many characteristics in common with King Ranch bluestem (B. ischuemum). WW-Spar bluestem, WW-535, and WW-604 are 3 of 30 yellow bluestem strains blended together to make ‘Plains’bluestern (Taliaferro et al. 1972). Potential variability in post-emergence seedling growth resultJOURNAL OF RANGE MANAGEMENT 38(e), November 1985 Table 1. Idenilfication of piant materials and seed weigbht. Entry Scientific name Cultivar/ Accession Country of Origin Air-valve setting&i> -Seed SizeMean U> SD Native Species: 1 Andropogon ha/Iii 2 Ponicum virgatum 3 ,t 4 Sorghasrrum nutans 5 Bouteloua gracilis Old World Bluestems (Bothriochloa spp.): 6 B. caucosica 7 ,, 8 B. intermedia var. indica 9 9, 10 ,, II ,, var. montana 12 n 13 B. ischaemum var. ischaemum 14 . . 15 9. 16 9. 17 1, var. songorica Woodward sand bluestem Caddo switchgrass Kanlow switchgrass WW-Western indiangrass (Woodward experimental) Hachita blue grama Caucasian bluestem, WW4%2 Caucasian bluestem, WW-765 ww-517 ww-811 ww-822 ww-857 WW-886 Ganada bluestem WW-Spar bluestem ww-535 ww-604 ww477 U.S.A. ,. 9, 9.

Delayed emergence of four conifer species on postfire seedbeds in eastern Canada

Abstract: This study compares the emergence of jack pine (Pinusbanksiana Lamb.), eastern white pine (Pinusstrobus L.), black spruce (Piceamariana (Mill.) B.S.P.) and balsam fir (Abiesbalsamea (L.). Mill.) for three seasons after sowing on two postfire seedbeds to test the hypothesis that conifer species differ in their ability to store viable seeds in the soil. Less than 20% of all viable seeds produced emergent seedlings in the first growing season. Emergence continued in the second growing season but not in the third. No viable seeds of any species were found at the end of the experiment. During the second growing season (July 1), the emergence of jack pine was greatest at the warmer and drier site but at the cooler and moister site, large numbers of black spruce emerged; by the end of the second season jack pine seedlings predominated at both sites. Although this delayed emergence accounted for <3% of the viable jack pine seeds sown, this percentage would be sufficient to produce a dense stand given normal postf...

Effect of sowing time on growth, yield and water-use of rain-fed wheat in the Wimmera, Vic.

Abstract: Crops of wheat (Triticurn aestivum cv. Olympic) were sown after a 10-month fallow at three times in both 1979 and 1980 in the Wimmera district of Victoria. Total above-ground plant material (biomass) and soil water content were measured for each crop at monthly intervals from sowing to anthesis and thereafter every 2 weeks. The duration of the phenophase, sowing to anthesis, varied from 88 to 163 days, but the maximum difference between anthesis date for the early (May) and late (August) sown crops was only 21 days. The duration of this phenophase was best described by a photothermal unit of 6846 day-degree-hours (>2OC, >6 h). The pattern of biomass accumulation varied markedly between crops, with biomass ranging from 9 to 13 t ha-' and yield between 3 and 4 t ha-'. Total wateruse efficiency in the production of biomass to anthesis ranged from 30.5 to 19.8 kg ha-' mm-' and in the seasonal production of grain from 8.6 to 6.6 kg ha-' mm-'. Whilst the data include only one early sown crop, it was possible to identify an optimum balance between pre- and post-anthesis growth in crops sown in June to produce 9 t ha-' of biomass at anthesis in early November, a yield sink of 12500 grains m-2 and in the 2 years of the experiment a grain yield of 4 t ha-'.

Response of Maize to Planting Dates in a Tropical Rainforest Location

Abstract: Grain yield of maize (Zea mays L.) was decreased by 30, 38 and 34 kg ha−1 for each day by which sowing was delayed after the first planting in March in 1978, 1980 and 1981, respectively. Yield reduction was associated with reduced plant size (plant and ear heights, tassel weight and branch numbers), ear number, ear weight, grain weight, ear length, ear diameter and kernel weight. High yields can thus be obtained by planting with the first rains of the year, especially if a good rate of emergence and seedling vigour under relatively hot, dry soil conditions can be ensured either culturally or genetically.

Seed survival and seasonal pattern of seedling emergence in some Leguminosae

Abstract: SUMMARY Seeds of 11 species of Leguminosae were collected, usually in each of 3 years, and mixed with the top 7·5 cm of sterilised soil confined in cylinders sunk in the ground outdoors and cultivated three times yearly. Emergence was recorded for at least 3 yr. Some seedlings of all species emerged soon after sowing but their numbers varied both within and between species, a probable reflection of the percentage of ‘hard’ seeds in the samples. Appreciable numbers of seedlings appeared in the following 3 yr but few seeds remained viable and dormant after 5 yr. The annual weed Vicia hirsuta was an exception, with an average of 11% of the seeds sown still viable at this time. Most seedlings of Lotus corniculatus, Medicago lupulina, Melilotus altissima, Trifolium repens and Vicia cracca emerged in spring, V. cracca rather later than the others. In contrast, maximum emergence of Trifolium arvense, T. campestre and T. dubium took place from June to September. Limited data indicated a similar pattern for T. striatum and Lathyrus pratensis. Seedlings of Vicia hirsuta emerged from October to May but scarcely at all in summer. Although variation in the percentage of hard seeds influenced the extent of immediate germination and seed persistence, the seasonal patterns in seedling emergence of most species were found to be very consistent.

Establishment of ryegrass, cocksfoot, and white clover by oversowing in hill country

Abstract: ‘Grasslands Nui’ perennial ryegrass (Lolium perenne L.), ‘Grasslands Wana’ cocksfoot (Dactylis glomerata L.), and ‘Grasslands Huia’ white clover (Trifolium repens L.) were surface-sown in spring into pre-treated hill country swards. Appearance, survival, and morphological development of seedlings were measured. Final seedling appearance of the grasses was similar (33% of seed sown) although ryegrass seedling appearance was more rapid than cocksfoot for the first 24 days after sowing. White clover seedling appearance was 58%. Survival of seedlings in plots laxly grazed before sowing was generally poorer than in hard-grazed or herbicide-treated plots. Species differed in seedling survival in the order: ryegrass= cocksfoot = white clover. Mean establishment levels 145 days after sowing were 30% for white clover, 23% for cocksfoot, and 25% for ryegrass. Herbicide treatment substantially improved seedling development for all 3 species. Analysis of the fate of grass seed showed losses were greatest imm...

Equipment and Methods for No-Tillage Wheat Planting

Abstract: FOUR experiments were conducted to evaluate grain drill performance in no-tillage seeding of spring and winter wheat in the Palouse region of eastern Washington The drill survey experiment showed similar stands and yields for six drills in winter wheat seeding, except that the highest two in yield were significantly better than the lowest yielder The opener design experiment showed better winter wheat yields for the double disk opener in pea (light) residue, while the hoe openers gave significantly better yields in wheat and barley (heavy) residue The use of colters did not effect yield but enhanced drill operation in heavy surface residue The fertilizer placement experiment showed a significant 330 kg/ha (5 bu/acre) winter wheat yield increase for deep banded nitrogen fertilizer compared to broadcast for wheat and barley residue, but no difference for pea residue For spring wheat planted into winter wheat and spring barley residues, subsurface banding of the fertilizer gave an advantage of approximately 723 kg/ha (11 bu/acre) compared with surface banding A second fertilizer placement experiment done in the greenhouse indicated that the seed-fertilizer separation distance must be at least 50 mm (2 in) to avoid seedling damage at the fertilizer rates and row spacing used in the experiment

Time of sowing and the yield of winter wheat

Abstract: Research conducted on sowing dates for wheat shows a trend towards increased yield as sowing is advanced (U.K.: Walker, 1980; Bingham et al. 1983; the Netherlands: Darwinkel, Hag & Kuizenga, 1977; Canada: Nass et al.1975; Briggs & Aytenfisu, 1979). In a review of the influence of drilling time on winter wheat in the U.K. McLean (1981) suggested October planting as the optimum. However, sowing before this time often results in increased yield (Bingham et al.1983).

Comparison of the effects of autumn and spring sowing date on growth and yield of combining peas ( Pisum sativutn L.)

Abstract: Experiments were conducted between 1978 and 1981 to investigate the effect of autumn and spring sowing on emergence, winter survival, growth and yield of combining peas (varieties ‘Frimas’, ‘Filby’ and ‘Vedette’). Effects of growth regulator PP 333 (Paclobutrazol, ICI pic) application and defoliation on winter survival of Filby were also investigated. Field emergence of autumn-sown Frimas (winter hardy) was less than Vedette or Filby but percentage winter survival was greater. PP 333 application, but not defoliation, increased percentage winter survival of Filby sown in September. Total dry-matter production and photosynthetic area of autumn- compared with spring-sown crops varied considerably between seasons. Yield data indicated that autumn-sown crops produce similar seed yields to spring sowings when winter survival is adequate. November sowings matured 2–4 weeks before March-sown crops, depending on variety and season. Optimum sowing dates were mid-November and early March. Large seed-yield reductions occurred when sowing was delayed until mid-April.

Reduced phytic Acid content does not have an adverse effect on germination of soybean seeds.

Abstract: Altering the level of phytic acid phosphorus by nutritional means had no effect on the ability of soybean ( Glycine max L. [Merr.], cv `Williams 799) seeds to germinate under laboratory or greenhouse conditions. Dry matter moved out of the cotyledons at similar rates whether the germinating seeds initially contained low (0.19), medium (0.59), or high (1.00 milligram per seed) phytic acid phosphorus. Growth of roots and shoots from 3 to 9 days after planting was similar for seeds containing low and medium levels of phytic acid phosphorus. The medium level of phytic acid resembles that found in field-grown seed, so it is clear that soybean seeds normally contain a phosphorus reserve far above that needed for germination and early seedling growth.

Time of sowing and the development of winter wheat

Abstract: Research conducted on sowing dates has shown a trend towards increased yield as sowing is advanced for winter wheat (Darwinkel, Hay & Kuizenga, 1977; Walker, 1980) and winter barley (Selman, 1980; White, 1981). Green & Ivins (1985) have quantified the rate of yield decline for winter wheat as sowing is delayed after mid-September, giving a mean value of 0–35% per day. For a similar study on winter barley (Green, Furmston & Ivins, 1985) a yield decline of 0–43% per day delay in sowing was attributed to reductions in the number of ears per unit area as planting was delayed.

Establishment and Expression of Soybean Symbiosis in a Soil Previously Free of Rhizobium japonicum

Abstract: An irrigated crop of Chaffey soybeans [Glycine max (L.) Merrill] was grown at Leeton, N.S.W., on a soil that was initially free of Rhizobium japonicum, with six rates of seed bed inoculation, three plant spacing treatments (4.5, 9.0, 18 cm), and two soil pretreatments (cropped, fallow). Rhizosphere populations were larger, nodulation throughout growth was better, and increases in amount of N in the plants between 78 and 114 days were greater on previously cropped than on previously fallow land because there was more plant-available soil N in the fallow than in the previously cropped treatments. Especially in the previously cropped treatments, there were h~ghly significant correlations, In sequence, between rate of inoculation, number of R. japonicum in the rhizosphere, extent of early nodulation, and progressive increase in nodulation. Lower, but still significant, correlations were found between extent of nodulation, shoot N, seed yield, and seed N. Plants compensated for wider spacing by increased growth. However, plants grown 18 cm apart were unable to compensate fully and yielded less seed and less seed N per hectare than plants grown at 4.5 and 9.0 cm. Plant spacing had little effect on the sequential development of the symbiosis. Rate of inoculation and seed yield were highly correlated and the correlation coefficients were higher in previously cropped treatments than treatments on previously fallow land. The amount of seed N in the treatments on previously cropped land with the highest rate of inoculation was 207 kg N ha-1, whereas shoot N in that treatment 47 days before final harvest was 355 kg N ha-1. This substantial quantity of N taken up by the well-nodulated soybeans in response to high levels of inoculation was greatly in excess of the requirements for seed production and might contribute to the nitrogen nutrition of subsequent crops.

Serradella (Ornithopus sp.): maturity range and hard seed studies of some strains of five species

Abstract: Two experiments are described which measured the maturity range and the softening of hard seeds of several species and strains of serradella (Ornithopus sp.) grown in field experiments near Esperance, Western Australia. Softening of hard seeds was measured in a diurnal 15/60¦C alternating temperature oven (laboratory oven) and from germination tests of samples collected periodically during summer from the field experiments (field test). Within O. compressus, there was a difference of about 30 days between strains, in time from sowing to appearance of the first flowers. The earliest flowering strains of the other species were included in the experiments; none commenced to flower as early as the earliest flowering O. compressus strains. When stored in the laboratory oven, the rate of softening of podded serradella seed varied markedly depending on species and strain, particularly for strains of O. compressus. Compared to naked (dehulled) seed, podded seeds of O. compressus and O. pinnatus softened in the laboratory oven at a much slower rate. The numbers of soft seeds were between 35 and 75% less, depending on strain and year. However, for O. isthmocarpus and O. perpusillus, the rate of softening was similar for both dehulled and podded seed. Irrespective of pod treatment, O. sativus was very soft-seeded. Within the bounds of the data, compared to the field test, the numbers of soft seeds counted for the laboratory oven tests were generally higher. Qualitatively the trends were similar for both methods.