Showing papers on "Sowing published in 1988"

Response of maize emergence rate and yield to soil water stress in period of seeding emergence and its meteorological assessment in central area of Jilin Province

Abstract: In spring of 2010-2011, an experiment with treatments on soil water stress and sowing by stages of spring maize (Zea mays) was conducted in the central Jilin Province. The responses of maize emergence rate and yield to soil water stress were analyzed, and the assessment models of the emergence rate and reduction of yield caused by drought were established based on meteorological conditions. The results showed that during the study period, the relationship between maize emergence rate or per unit yield, and the soil moisture in 0-20 cm layer or soil available water content presented a significant quadratic function. The emergence rate and yield increased with the higher surface soil moisture, while decreased obviously under the drought condition. The emergence rate and yield were higher in the conditions of soil moisture in the range of 22%-24% or soil available water content in 50-65 mm, while the emergence rate and yield decreased obviously with the soil moisture less than 19% or available water content less than 35 mm. The soil moisture decreased 1% each, along with the emergence rate decreased by about 6% , and the yield decreased by about 7%. The soil available water content decreased by 10 mm, along with the emergence rate and yield decreased by about 13% and 14%, respectively. The indicators and models in this article could be applied to assessment and prediction of maize emergence rate and the reduction of yield caused by drought.

Ecological and Evolutionary Consequences of Seed Size in Prunella Vulgaris

Abstract: Seed size has significant demographic consequences in Prunella vulgaris. Measurements of the effects of seed size were obtained by sowing seeds of known size at four field sites and recording seedling emergence, survival, and size. The intensity of selection on seed size was calculated from these data. Large seeds had a significantly greater probability of emergence at most study sites in each of 2 yr. The effects of seed size were expressed most strongly during the early part of the life cycle, between sowing and emer- gence, and much less so in later phases of the life cycle. In contrast to a prediction based on the greater relative frequency of large-seeded species in later successional habitats, the effect of seed size on percent seedling emergence did not differ significantly between an old-field and a woodland habitat. However, it is likely that the intensity of natural selection on seed size is greater in an old-field than in a woodland population because the natural distributions of seed size in old-field populations include more small seeds than do those in woodland populations. An analysis of the costs and benefits of producing large and small seeds revealed that in addition to selection favoring large seeds, there was selection favoring individuals that produced large seeds at three of the four study sites. At the fourth site, there was no selection favoring larger seeds or parents that produced larger seeds. Substantial capacity for phe- notypic plasticity in seed size suggests that there may be little opportunity for an evolu- tionary response despite strong selection favoring large seeds.

Phosphorus cycling in wheat-pasture rotations. II. The role of the microbial biomass in phosphorus cycling.

Abstract: The incorporation of phosphorus derived from fertilizer and plant residues into the soil microbial biomass was studied under field conditions by using isotopic double labelling. The 33P-labelled medic residues (Medicago truncatula cv. Paraggio) and 32P-labelled fertilizer were added to a solonized brown soil (Calcixerollic xerochrept) before sowing of a wheat crop ( Triticum aestivum cv. Warigal). Amounts of 31P, 32P and 33P in the microbial biomass were determined at 0, 7, 18, 32, 46, 61, 81 and 95 days after sowing of the wheat. Throughout the experiment, amounts of 31P in the microbial biomass were closely related to gravimetric soil water content, with a large and rapid increase in the amount of 3 1 ~ in the microbial biomass being observed in the first 7 days after wetting of the (initially) dry soil. Due to banding of the fertilizer at sowing, little (<5%) of the 32P was recovered in the microbial biomass throughout the experiment. Of the 33P applied in the medic residues, 22-28% was recovered in the microbial biomass. Most of the P taken up by the microbial biomass was derived from native soil P (i.e. not added that season).

Cotton Response to Planting Date and Mepiquat Chloride

Abstract: Few studies have documented the effect of planting date on cotton (Gossypium hirsutum L.) response to mepiquat chloride (MC) (N,N-dimethylpiperidinum chloride). Planting dates were mid-April, early May, and mid-May during 1982, 1983, and 1984, and consisted of five cultivars representing three general maturity types: early—‘DES 422’; intermediate—‘Coker 3131’, ‘Stoneville 825’, and ‘McNair 235’ and full season—‘Deltapine 90’. Mepiquat chloride was applied at a rate of 49 g a.i. ha⁻ when the plants had about 0.7 white flowers per meter of row. More parameters were affected by chemical treatment and planting date than by cultivars. Plants were taller and produced fewer flowers, smaller bolls, and less lint as planting dates were delayed. In addition, most boll components were adversely affected by delayed planting dates. However, most of the adverse effects caused by delayed planting were mitigated by the MC treatment. Mepiquat chloride ✕ planting date interactions occurred for plant height, flower production, lint yield, and seed index. Mepiquat chloride caused a 4.5% reduction in lint yield from the early planted plots, and 5.4 and 12.7% yield increases from the optimum and late plantings, respectively. Mepiquat chloride increased boll weight in all plantings, but affected (increased) flower production only in the late planting. Seed index was increased and lint percentage reduced in all MC-treated plots from each of the three plantings. The MC early, intermediate-, and late-planting plots averaged 0.11, 0.25, and 0.30 less height, respectively, than the control plots. Statistical significance was achieved only for the latter two plantings. These studies indicate that MC application would be most beneficial in late-planted cotton, which tends to produce more vegetative growth than earlier plantings. Contribution from the USDA-ARS, Cotton Physiology and Genetics Res. Unit in cooperation with the Mississippi Agric. and For. Exp. Stn.

Phosphorus Cycling in Wheat-Pasture Rotations. I. The Source of Phosphorus taken up by Wheat

Abstract: Wheat plants (Triticum aestivum cv. Warigal) were grown in the field in a solonized brown soil (Calcixerollic xerochrept) to which 33P-labelled medic residues (Medicago truncatula cv. Paraggio) and 32P-labelled fertilizer had been added. Amounts of 31P, 32P and 33P in the wheat plants were determined at 7, 18, 32, 46, 61, 81 and 95 days after sowing. The 32P uptake by the wheat plants increased throughout the experiment and reached 11 -6% of the isotope applied by 95 days. Of the 33P applied in the medic residues, 5 -4% was recovered in the wheat plants. Most of the P taken up by the wheat plants was from soil P (i.e, from sources not added that season).

The effect of irrigation and nitrogen fertilizer on rapeseed (Brassica napes) production in South-Eastern Australia

Abstract: A field trial was conducted to determine the response of rapeseed (Brassica napus cv. Marnoo) to two irrigation treatments and six nitrogen fertilizer treatments. Dry matter accumulation, leaf area development and seed yield were measured. The dry matter and seed yield response to applied nitrogen was greater under irrigated compared to rainfed conditions. Maximum seed yield (approx. 3.8 t ha−1) was obtained from the irrigated treatment receiving 100 kg N ha−1 applied at sowing. This high rate of N application at sowing led to more rapid leaf area development and higher maximum LAI compared to treatments supplied with split application of the same amount of N at sowing and rosette stages. Greater partitioning of dry matter into the leaf component and higher specific leaf areas under the higher N regime were largely responsible for this increase. Higher maximum LAI's were associated with greater numbers of pods per plant, which combined with longer leaf area duration led to higher final seed yields.

Nitrogen Application to Cotton on Clay Soil: Timing and Soil Testing

Abstract: With the aim of improving utilization of N fertilizer and the flexibility of N application strategies in cotton (Gossypium hirsutum L.), five field experiments examined the response of cotton to N fertilizer, either applied before sowing or as applications before or after sowing, or both. The soils were Pellusterts with a high pH. Anhydrous ammonia was used as the N fertilizer throughout. Soil nitrate N, N uptake, and lint yield were measured in all experiments. There was a linear increase in N uptake with increased application of N fertilizer, with an average of 30% of applied N being taken up by the crop 120 d from sowing. Compared to a single presowing application, N recovery was increased by split application on two occasions, but on a further two occasions it was decreased. Split application increased lint yield on one occasion only—when compaction, waterlogging, and a long growing season allowed better utilization of sidedressed N. On all other occasions the two methods of N application produced similar yields. Therefore, sidedressing can be considered a viable practice on these soils and in this climate. Maximum yield was obtained when crop uptake was about 108 kg N/ha at 120 d from sowing, and was only partially affected by yield level. Soil nitrate N, sampled to a depth of 30 cm 4 wk before sowing, was closely correlated (r=0.86) with subsequent plant N uptake in nil fertilizer treatments. Therefore, N fertilizer requirement can be accurately determined by applying moderate levels of N before sowing, then subsequently testing for soil N on nil fertilizer strips to determine if any sidedressing is necessary. It was concluded that recovery of N fertilizer was generally poor, and improvement of this parameter has the potential to increase fertilizer use efficiency and productivity of cotton in this environment. Contribution from the Univ. of California, Davis.

The importance of small-scale disturbance for seedling establishment in Cirsium vulgare and Cynoglossum officinale

Abstract: (1) Germination and establishment of Cirsium vulgare and Cynoglossum officinale in various micro-environments were studied in a sand-dune area at Meijendel, The Netherlands. (2) The number of established seedlings was increased forty-fold in Cirsium vulgare and five-fold in Cynoglossum officinale by artificial speed input of 11 seeds dm-2. In Cirsium vulgare, seed input was the primary prerequisite for seedling emergence. Disturbance of soil and vegetation alone had little effect on the number of seedlings establishing naturally, but increased the number of seedlings in plots with seeds sown. (3) Disturbance had the additional effect of advancing the germination period and accentuating autumn germination in Cirsium vulgare. (4) Seedling mortality did not differ between disturbed and undisturbed plots. In both species seedling recruitment was high in thickets and Crateagus scrub and low in open vegetation. (5) After seed sowing, significantly less seedlings were found in May and July on sites where the naturally occurring population had disappeared (Cirsium vulgare) or dropped to a low density (Cynoglossum officinale) than on sites where the natural population still thrived. These differences were not found (Cynoglossum officinale) or reduced (Cirsium vulgare) on disturbed plots with seeds sown, indicating the importance of small-scale disturbances for population maintenance.

Light quality effects on the appearance of tillers of different order in wheat (Triticum aestivum)

Abstract: SUMMARY Plants of Triticum aestivum cvs Norkin Pan 70, La Paz Inta, Buck Cencerro and Buck Cimarron were grown outdoors in individual pots with two sowing dates and irradiated at the end of the day either with red or far-red light. In red-treated plants the number of tillers was close to the potential calculated from the number of leaves on the main shoot but far-red treated plants produced less tillers. The magnitude of the effect was larger for secondary and tertiary than primary tillers. Thus, the proportion of primary to secondary and tertiary tillers was larger in FR-treated plants. Leaf sheath and lamina were longer under FR in the second sowing date, possibly due to warmer nights. These responses were greatly affected by the genotype. Significant differences in ear number were not found but in one of the sowing dates red-light-treated plants showed a lower grain number and yield than those treated with far-red.

High phosphorus concentrations in seed of wheat and annual medic are related to higher rates of dry matter production of seedlings and plants

Abstract: Seed of 2 cultivars of wheat (Triticum aestivum) and 1 burr medic (Medicago polymorpha) with increasing phosphorus (P) concentrations (wheat 1.4-3.7 g P/kg dry matter, medic 3.3-7.9 g P/kg dry matter) were collected from field experiments with variable levels of applied superphosphate (wheat 0- 577 kg P/ha, medic 0-364 kg P/ha) in south-western Australia. These seeds were used in further experiments to examine the effect of seed P concentration on the subsequent dry matter (DM) production of seedlings and plants in 3 glasshouse pot experiments and 1 field experiment. Seed of the same size (wheat, 35 mg/seed; medic, 3.6 mg/seed) but with increasing P concentration produced substantially higher DM yields in the absence or presence of freshly applied superphosphate P up to 28-35 days after sowing in the pot experiments and 67 days after sowing in the field experiment.

Planting Date and Temperature Effects on Germination, Emergence, and Seed Yield of Chickpea

Abstract: Commercial production of chickpea (L.) in the Palouse region of northern Idaho and eastern Washington was initiated in 1981. Since the cool springs and short growing season of this area limit the adaptation of chickpea, field and laboratory studies evaluating 10 chickpea lines were conducted to optimize the planting date of this new pulse crop. Laboratory germination and radicle elongation of the 10 lines at 5, 13, and 20 °C were compared to field emergence and seedling growth at Moscow, ID, on a Palouse silt loam (fine-silty, mixed, mesic Pachic Ultic Haploxeroll) during 1982 and 1984. The 10 lines were also planted in late April, early May, and late May to determine the effect of planting date on yield components and seed yield. Greatest germination and radicle elongation of all 10 lines occurred at 20 °C. At 5 °C, less than half of the seed germinated within 7 d, and radicle elongation was less than 4% of that observed at 20 °C. The 10 lines did not differ in their ability to germinate under cold conditions in the laboratory. Under field conditions of 1984, the Desi lines with pigmented testa showed a higher percentage of emergence than the non-pigmented Kabuli lines. Seedling dry weight accumulation was most rapid in the large seeded Kabuli seedlings and slowest in the smaller seeded Desi seedlings. Planting in late April produced higher seed yields than planting in late May (34 and 5% in 1982 and 1984, respectively). However, seedling emergence was slower at the early planting date. These results indicate that chickpea grown in areas with cool climates such as northern Idaho should be planted in the early spring when average soil temperatures exceed 13 °C to insure optimum seed yield.

Survey of farm management practices of the northern wheat belt of New South Wales

Abstract: A survey of management practices on wheat farms in northern New South Wales was carried out on 50 farms between 1983 and 1985 and was supplemented by a questionnaire mailed to 750 growers in 1985. Information was collected on crop rotation, tillage practice, fertiliser use and weed control practices. Data were collected from 1 paddock on each farm and included: wheat grain yield and quality, available soil water and nutrients at sowing, wild oat density, and incidence of soil-borne diseases. The 3-year average grain yield in survey paddocks was 2.2 t/ha. Multiple regression analysis was used to identify factors affecting grain yield and protein in 1985. Of the variation in wheat grain yield, 74% was explained by variation in available soil water at sowing, available soil nitrate at sowing, sowing date and wild oat density. Grain protein content declined with increasing available soil water and phosphate at sowing and with earlier sowing, but increased with available nitrate at sowing. Agronomic practices aimed at maximising wheat grain yield, in the presence of a deficiency ofavailable soil nitrate, are likely to result in a reduction of grain protein content. Likewise, responses to application of nitrogenous fertiliser are likely to be inversely related to available soil water at sowing. The mean gross margin for 1984 and 1985, based on $100/t of wheat grain, was $128. The mean gross margin for the least profitable 20% of paddocks was $37, and $253 for the top 20%. New varieties of wheat and herbicides were readily adopted by farmers. On the other hand, adoption of nitrogenous fertiliser use was slow, considering the widespread and long-standing deficiencies of nitrogen in cropping soils of the region. Crop rotation and tillage practices have changed only marginally since the late 1940s. The results of this survey indicate that the usefulness of soil testing for predicting fertiliser requirements could be improved by taking into account levels of available soil water, weed competition and sowing date and by using multiple regression analysis.

Effects of a water-depth gradient on the germination of lakeshore plants

Abstract: The germination requirements of many wetland species commonly found in the seed bank are poorly understood. The purpose of this study is to explore the germination responses of lakeshore plant species to a water-depth gradient on each of two soil types normally found on shorelines and to test whether germination patterns predict field distributions of adults. Germination patterns were determined in a greenhouse by sowing seeds of 24 lakeshore species along an artificial water-depth gradient, using two soil types (sand and organic soil). Those species showing significant treatment effects were then tested for similar or different germination patterns, using Kendall's coefficient of concordance. Species had similar germination patterns (n = 5, P = 0.02) on sand. Species had different germination patterns (n = 7, P > 0.50) on the organic soil. Mean water-depth of germination was significantly correlated with the mean depth occupied by adults in the field for seven species (r = 0.81, P = 0.04). This study sho...

The response of field beans (Vicia faba L.) to irrigation and sowing date. 2. Growth and development in relation to yield.

Abstract: The growth and yield of four crops of field bean cv. Maris Bead in response to irrigation and sowing date were analysed in relation to leaf area expansion and senescence and their absorption and utilization of photosynthetically active radiation (PAR). Total dry matter (D.M.) production and seed yield were strongly correlated with total green area duration (GAD) and post-flowering GAD respectively.Total D.M. production was also strongly related to radiation absorbed by the green surfaces of the crop although autumn sowing and drought both decreased the constant of proportionality, i.e. the growth efficiency (Eg). Autumn sowings yielded more than spring sowings because they grew for longer and received 22% more radiation. Their harvest index was also about 40% higher than in spring sowings. These more than compensated for their smaller Eg. Drought decreased yield mainly by decreasing radiation received and Eg. Growth duration was shorter and harvest index was smaller.The rate of phenological development was strongly dependent upon temperature and to a lesser extent on photoperiod. The average thermal duration from emergence to flowering was 790 °Cd above a base of 0 °C. The time from sowing to the end of the pod growth was well represented by a simple multiplicative model in which development rate was a linear function of temperature above a base of 0 °C and photoperiod above a base of 6 h. The average photothermal duration required for 10 crops was 980 °Cd.An attempt was also made to determine the crop physiological and environmental factors which govern the change in size of the yield components of field bean crops caused by irrigation and sowing date. The final number of pods per plant was closely correlated with the rate of supply of assimilates during pod filling. Irrigation increased assimilate flux by increasing leaf area, growth rate and total dry matter during pod growth. Both the rate and duration of pod growth were little affected by irrigation. Autumn sowings produced heavier pods and beans due to both a faster rate and a longer duration of growth which were associated with a greater production of assimilate during the seed growth period. Seed growth depends on both the current assimilate and stored reserves, the latter especially when plants were subjected to environmental stress.

Application of different sources of manganese sulfate decreases take-all (Gaeumannomyces graminis var. tritici) of wheat grown in a manganese deficient soil.

Abstract: Two experiments tested the effectiveness of manganese (Mn) decreasing take-all of wheat. The first experiment was conducted under controlled environmental conditions. Mn sulfate was mixed through the soil at sowing or 2 weeks before, or applied to the seed or leaves, and manganese dioxide (MnO2) was mixed through the soil at sowing or 2 weeks before. Mixing manganese sulfate (MnSO4) through the soil was the most effective treatment at decreasing take-all, followed by seed applied Mn. MnO2 and foliar applied Mn had little effect on take-all. All Mn treatments, except foliar Mn, completely eliminated Mn deficiency in the plants. In the second experiment, which was conducted in the field at a Mn deficient site, Mn sulfate and MnO2 were applied to the soil at sowing. MnSO4 decreased take-all and increased grain yields in take-all inoculated plots nearly threefold, but increased yields only slightly in uninoculated plots. MnO2 was not effective in decreasing take-all or increasing grain yield. This is the first report of take-all infection being suppressed by MnSO4in the field. The results of these experiments support the hypothesis that Mn may be acting through the physiology of the wheat plant to decrease take-all.

Contributions of fixed nitrogen and soil nitrate to the nitrogen economy of irrigated soybean

Abstract: Effects of soil nitrate and numbers of Bradyrhizobium japonicum on the development and functioning of a soybean symbiosis and on crop production were studied in a field experiment at Breeza, New South Wales, Bragg soybean was grown with irrigation on soil, initially free of B. japonicum , with four rates of fertilizer-N (0, 100, 200, 300 kg N ha −1 as ammonium nitrate applied 6 weeks before sowing to provide four concentrations of soil nitrate) and four rates of inoculation [nil, normal (n). 100n, 1000n]. The inoculant strain was B. japonicum CB1809. Observations were made on nodulation, the relative abundance of ureidcs in xylem exudates as an index of N 2 fixation, dry matter and seed yield, and total nitrogen in shoots and seed. Results showed clearly that soil nitrate repressed nodulation, that the effect was magnified as soil nitrate concentrations increased, but that inhibition was substantially ameliorated by increased numbers of rhizobia. The relative abundance of ureides in xylem exudates responded similiarly. The highest yields of dry matter and of N in shoots and in seed occurred at the highest rates of inoculation (100n, 1000n) at intermediate and high soil nitrate (N100, N200, N300); at low soil nitrate (N0), yields were increased by inoculation per se but not by the rate used. Uninoculated plants did not nodulate and yields in these plots reflected concentrations of soil nitrate. Data suggested that soil nitrate and N 2 fixation were not always complementary in meeting the N requirements of the growing crop. Absence of rhizobia. except at the highest rate of nitrate, and repression of nodulation at the normal rate of inoculation by intermediate concentrations of nitrate resulted in reduced N yields because of insufficient N supply to the crop during the final stages of growth.

Effects of moisture stress on the oil and protein components of soybean seeds

Abstract: Over a five year period, early-maturing indeterminate soybean lines were evaluated in parallel dryland and fully irrigated field experiments. Moisture stress effects on yield, seed weight, and oil and protein content of seeds were evaluated by comparing genotype x moisture regime means. Both the amount and distribution of rainfall varied among seasons, resulting in dryland yields from 6% to 84% of the fully irrigated experiments. Seed weight also responded to seasonal rainfall patterns with reductions owing to moisture stress contributing from 29% to 54% of the yield response. Between 57% and 68% of the seed weight loss was attributed to changes in weight per seed of oil and protein. An index relating response to stress to irrigated performance was calculated for each trait. Regression equations showed significant (P > 0.05) relationships between the effect of stress on seed weight and the resultant oil and protein responses to stress. When compared to the irrigated treatments, oil and protein percentages of dryland seed varied, depending on the balance between reduction in seed weight and response of these constituents to the pattern of stress. In one season when severe stress occurred very early in podfill, the result was reduced protein and increased oil percentages. In three other years the protein percentage of dryland seed increased, and was accompanied by a decrease in oil percentage. In a high rainfall season, non-significant (P > 0.05) increases in both oil and protein percentage were obtained. Sowing early-maturing genotypes into soils with more than 150 mm available soil moisture will usually avoid moisture stress until after podfill commences. Stress will usually increase during podfill, which will most often result in higher protein and lower oil content of dryland produced soybean seed.

Grass seedling emergence, morphology, and establishment as affected by planting depth

Abstract: The seeding depth of grasses affects emergence and adventitious root development. Seedling root morphology and development should be considered when determining planting depth for forage grasses. A field study was conducted on a Kennebec silt loam (fine-silty, mixed, mesic Cumulic Hapludolls) during June to August 1985 and 1986 to investigate the effect of planting depth on seedling emer- gence, morphology, and establishment of smooth bromegrass (Bro- mus inermis Leyss.), big bluestem (Andropogon gerardii var. gerardii Vibnan), indiangrass (Sorghastrum nutans (L.) Nash), and switch- grass (Panicum virgatum L.). Seeds were planted by hand to insure seeding depths of 1.5, 3.0, 4.5, and 6.0 cm. Emergence percentage decreased with increased planting depth for all grasses except switchgrass, which had similar percentages at the 1.5- and 3.0-cm planting depths. Coleoptile length and seedling crown depth were positively correlated with actual planting depth in smooth brome- grass, while subcoleoptile internode length was positively correlated with actual planting depth in big bluestem, indiangrass, and switch- grass. lndiangrass differed from big bluestem and switchgrass, since its coleoptile length was positively correlated with actual planting depth. Smooth bromegrass may have the potential of increased ad- ventitious root development due to deep placement of the seedling crown in the soil. Big bluestem, indiangrass, and switchgrass do not have the potential of increased adventitious root development as seeding depth increases, since there was no correlation of seedling crown depth with actual planting depth. Rapid increase in adven- titious root number of big bluestem, indiangrass, and switchgrass was noted after three or more consecutive days of rainfall after 4 wk from planting.

Seed and seedling vigour

Abstract: Seeds start to deteriorate as soon as they have reached peak maturity on the mother plant at a rate which depends on seed moisture content and temperature. Symptoms of reduced vigour include slower and more variable rates of germination, a greater proportion of morphologically abnormal seedlings, and a decreased ability to emerge from seedbeds under stressful conditions. Poor vigour can decrease yields in two ways: first, decreased emergence may lead to sub-optimal populations of irregularly distributed plants: secondly, those seedlings which do emerge grow more slowly and, under some circumstances, this can affect final yields, even when anticipated sub-optimal emergence is compensated by increased sowing rates. Seed vigour is a function of both genotype and environment; accordingly, improvements are feasible through breeding as well as through improved agronomic practices and seed handling. The principles of reliable vigour testing as an aid to seed production and genetic improvement are discussed.

Seed production and seed survival under grazing of annual medics medicago spp in north syria

Abstract: Three experiments which measured seed production and seed survival of annual medics (Medicago spp.) were conducted at Tel Hadya in north Syria. In Expts 1 and 2, conducted in consecutive years, the effects of rate and date of sowing on seed yield and its components were measured, while in Expt 3, the residual seed under summer grazing was monitored. In all three experiments seed permeability was observed at frequent intervals in summer and autumn. Selected ecotypes of three native medics (Medicago rigidula (L.) All., M. rotata Boiss. and M. noeana Boiss.) were compared with cultivars of M. truncatula Gaertn. and M. polymorpha (L.).Seed production was greatest at sowing rates of 20–40 kg/ha. The native species produced more seed (up to 1000 kg/ha) than the cultivars (less than 500 kg/ha), although not significantly so in the case of the late-flowering ecotype of M. noeana. Seed yields of 500–1000 kg/ha were considered to be sufficient to perpetuate the pastures, but even higher seed yields are desirable.Seed yield was closely related to number of pods in all ecotypes and, in Expt 2, up to 95% of flowers failed to produce mature pods. Flowers were more likely to mature at high sowing rate (256 kg/ha), in striking contrast to flower production itself which was greatest at sowing rates of less than 30 kg/ha. Flowers produced early in the season (before mid-April) were far more likely to give mature pods than late-produced flowers.In late October, seeds of the native species were less permeable (10%) than those of the cultivars (30%), although their permeability was similar to that of the cultivars in Australia. In the three experiments the seasonal pattern of permeability varied, although there was a tendency for seeds to gain permeability in autumn. In Expt 1 there was a strong suggestion that the change from impermeability to permeability was reversible.Ewes grazing mature pods gained weight, apparently as long as pod availability exceeded 10 kg/ha. It was clear that the condition of ewes was not a good guide to appropriate stocking rate for persistence of pastures, and that farmers will have to use other methods to assist them in grazing management.

The response of field beans (Vicia faba L.) to irrigation and sowing date. 1. Yield and yield components.

Abstract: The response of 4 crops of autumn- and spring-sown field beans cv. Maris Bead to irrigation applied during the vegetative, flowering and pod-filling phases was examined during 1981–2 and 1982–3. The crops, grown on a Templeton silt-loam, were irrigated weekly in amounts equal to the difference between the estimated evapotranspiration and rainfall of the previous week using trickle irrigation.Seed yield of fully irrigated autumn- and spring-sown crops (averaged over the two seasons), was 5·2 and 3·3 t/ha respectively, about 45% greater than the yield of unirrigated crops. The increase in yield due to irrigation was mainly associated with an increase in total dry matter (TDM) production as harvest index varied little within each sowing. The yield response to each mm of applied irrigation water ranged from 0 to 9 kg/ha and did not appear to be related in any way to the developmental phase of the crop when irrigation was applied.Seed yield within each sowing was closely correlated with the number of beans per unit area and the number of pods per plant. Autumn sowings yielded about 55% more than spring sowings mainly due to a higher harvest index which was associated with a much heavier mean weight per bean.

Studies on alternative means of legume inoculation: microbiological and agronomic appraisals of commercial procedures for inoculating soybeans with Bradyrhizobium japonicum

Abstract: Four commercial procedures for inoculating soybean (Glycine max [L.] Merr.) with Bradyrhizobium japonicum were compared at three sites in New South Wales. Three procedures involved applying inoculant to the seed shortly before sowing (seed inoculation) as a slurry in water or gum arabic adhesive or by sprinkling inoculant on the seed in the seed box of the planter. In the fourth, inoculant was suspended in water and sprayed directly into the seed bed alongside and beneath the seed (liquid inoculation).With seed inoculation substantial losses of viability of inocula (94%-99.95%) occurred between inoculation and sowing. Some of the loss was attributable to separation of inoculant and seed, as it passed through the machinery; no such loss of viability occurred with liquid inoculation. Colonization of the rhizosphere relative to the numbers of rhizobia delivered into the seed bed was poorer with liquid inoculation than with the slurry treatments. This was attributed to the uniform distribution of rhizobia applied as liquid inoculant in the seed bed, in contrast to the concentration of rhizobia applied as slurries in the vicinity of each seed. Slurry treatments generally promoted earlier nodulation than liquid inoculation, but as the crops aged, the differences disappeared and were not reflected in seed yield or seed nitrogen. Application of inoculant to seed in the seed box, although better than an uninoculated control, was consistently inferior to the other inoculation procedures.Given favourable environmental conditions both at sowing and afterwards, slurry inoculation and liquid inoculation were equally likely to initiate a successful symbiosis. Slurry inoculation may be superior when there is limited soil moisture after sowing, whereas liquid inoculation may be better when seed is sown into relatively dry soil with good moisture beneath.

Effects of inoculum source and irrigation on black dot disease of potatoes (Colletotrichum coccodes (Wallr.) Hughes) and its development during storage.

Abstract: In 1985 and 1986 plots were planted with seed tubers affected with black dot and with healthy seed inoculated or not with cultures ofColletotrichum coccodes at planting. Half the plots were irrigated from shoot emergence to the end of July. Seed tubers rotted more often when they were diseased than when they were not and rotting was increased by irrigation; by contrast, up to 18 weeks after planting irrigation decreased infection of stem-bases, roots and tubers. Tuber infection, first recorded in July, increased throughout the season and most rapidly from September, when the irrigation applied earlier increased disease. Soil-applied inoculum gave most disease in both years and tubers from healthy seed gave least in 1986 but as much as from diseased seed in 1985. Incidence and severity of black dot increased more during storage at 15°C than at 5°C and only on unwashed tubers.

Seed and Soil Treatments to Improve Emergence of Muskmelon from Cold or Crusted Soils

Abstract: Cold soil temperatures, seedling diseases, and soil crusting may limit stand establishment of early-season muskmelons (Cucumis melo L.). We tested the ability of seed and soil treatments to overcome these factors and improve seedling emergence. The seed treatments were seed priming (6 d at 25 °C in aerated 0.3 M KNO₃ solution followed by drying) to improve the rate of germination at low temperatures, and metalaxyl [N-(2,6-dimethylphenyl)-N-(methoxyacetyi) alanine methyl ester] fungicide (Apron 25W) to prevent damping- off diseases. The soil treatments were spot applications of soil drenches containing metalaxyl fungicide (100 μg L⁻¹ Ridomil 2E), an anticrostant [2% Naico 2190, (Nalco Chemical Corp, Carson, CA)] or both fungicide and anticrustant. In laboratory tests at 18 °C, both germination rate and final germination were markedly improved by seed priming in ‘PMR 45’, ‘Magnum 45’, ‘Topmark’, and ‘Topscore’ plants. Seedling emergence from sterilized soil in flats under ambient outdoor temperatures (7-23 °C) was also improved by seed priming. Seed priming resulted in more rapid emergence or increased final emergence in five of seven field trials in two locations. Anticrustant applications to the soil covering the seed consistently improved stand establishment, particularly in badly crusted soils. Metalaxyl application to the seed or soil generally improved emergence, but the effect varied with cultivar, location, and planting method. None of the treatments significantly influenced final fruit yield. The combination of seed priming, fungicides, and anticrustants could allow lower seeding rates of expensive hybrid seed while achieving earlier emergence and adequate plant densities in earlyseason muskmelon crops. Supported in part by an allocation to K.J. Bradford through Regional Res. Project W-168 and by grants from the Melon Research Board, Dinuba, CA.

Role of seed reproduction in the population ecology of Sorghum halepense in maize crops

Abstract: (1) Sorghum halepense (L.) Pers., a perennial weed, reproduces by seed and from rhizomes. This study examines the contribution of seed reproduction to population growth in maize fields. (2) Seed production in dense patches was very high (8080 + 4300 full seeds m-2). Ninety per cent of the total seed yield was produced during December and early January. (3) Shedding of seed began 30 days after panicle emergence. Daily seed shedding in dense patches ranged from 75 to 100 m-2 during most of the summer. (4) After an initial rise in January, seed density on the soil surface decreased about fivefold during the summer months. Using seed sources of known size, seed losses from the soil surface were found to vary between 3 and 15 % per day during the crop cycle, and between 20 and 50% per day during the fallow period. Loss of seed was substantially reduced by seed burial and completely prevented if seeds were covered with 5 mm plastic mesh. Results indicated that predators (most likely rodents) were the agents of seed loss. (5) Seedlings emerged during the month after sowing maize. Average seedling survival was 25%, between-row cultivation being the main cause of mortality. Forty per cent of the established plants produced seeds. The average fecundity of seed plants was forty-one seeds per plant. (6) A simple model indicated that the potential for multiplication during the 'plant phase' is about four seeds per seedling per year. However, when losses during the 'seed phase' are incorporated in the model, the multiplication rate of a population reproducing solely by seeds is substantially lower than one. It is inferred that reproduction by seeds would not maintain the population under continuous maize.

Seed Germination of American Pokeweed (Phytolacca americana). I. Laboratory Techniques and Autotoxicity

Abstract: Seeds of pokeweed (Phytolacca americana L.), an underinvestigated species, were studied to determine optimal conditions for laboratory germination. Soaking seeds in acid solutions prior to sowing increased rates of germination. Concentrated (conc) H2SO4 was more effective than conc NO3 or conc HCI acids. Physiological evidence from seed germination studies suggests that autotoxicity, or intraspecific inhibition, exists in pokeweed, a species known to possess several biologically active compounds. Seed germination was investigated in the laboratory with aqueous extracts of vegetative and reproductive structures of the plant. The presence of extracts from most plant parts correlated with reduced or no germination by seeds of its own species, whereas the presence of distilled water correlated with high percentages of germination by control seeds. Whether diluted with water by 5-fold (20% v/v) or undiluted, juice of pokeweed fruits completely inhibited the laboratory germination of pokeweed seeds. Also, extracts of freshly harvested mature leaves, stems, and immature fruits inhibited seed germination. However, results with root extracts, obtained from a single individual, depended more on concentration, since the highest concentration (50% v/v) inhibited germination, and lower concentrations (10 and 20% v/v) increased germination percentages over control samples. Results with extracts of juvenile leaves correlated with neither inhibition nor promotion of germination. Thus, except for juvenile leaves and the root, most extracts of the pokeweed plant inhibited seed germination with more mature structures exerting more inhibition and less mature structures exerting less or no inhibition. The ecological implication of autotoxicity is that seeds are more dispersed through time and space. In regard to seed germination by other species, especially those taxa known to possess biologically active compounds, these and other results suggest that the phenomenon of autotoxicity might be more widespread than previously suspected.