Showing papers on "Sowing published in 1994"
TL;DR: Sixteen spring wheat genotypes were grown under hot, irrigated, low latitude conditions, during the 1990-1991 and 1991-1992 winter cropping cycles in Mexico, Egypt, India and the Sudan, and in the 1990 and 1991 winter cycles in Brazil.
Abstract: Sixteen spring wheat genotypes were grown under hot, irrigated, low latitude conditions, during the 1990-1991 and 1991-1992 winter cropping cycles in Mexico, Egypt, India and the Sudan, and in the 1990 and 1991 winter cycles in Brazil. The genotypes were chosen to represent a range of genetlc diversity within modem wheat varieties. In addition to grain yield, in Mexico a number of morphological and physiological traits were measured throughout the growing season on two sowing dates (December and February), to evaluate their correlation with yield in the other countries. The morphological traits - above-ground biomass at maturity, grains m-2, days to anthesis and days to maturity - measured on both sowing dates in Mexico showed generally significant correlations with yields measured at the other sites. Moreover, ground-cover estimates early in establishment, and at anthesis, also showed some association with performance at these sites, but only when measured on the hotter, February sowing date in Mexico. Membrane thermostability (MT), measured on field-acclimated flag leaves showed generally significant correlations with performance at all sites, and with MT measurements made on heat- acclimated seedlings of the same genotypes grown in growth chambers. Flag-leaf photosynthesis measured at booting, anthesis and during grain filling on both sowing dates, was generally significantly correlated with grain yield at all sites, as was rate of loss of leaf chlorophyll content during grain filling. Stomatal conductance was also significantly correlated with performance at all three stages. Canopy temperature depression (CTD) measured with an infrared thermometer was significantly positively correlated with performance at the international sites when measured between 1200 and 1600 hours, after full canopy establishment. The correlation of CTD with yield was not affected by the irrigation status of the crop under well-watered conditions. The possible use of these traits in selection for yield under hot conditions is discussed.
528 citations
TL;DR: In this paper, the authors identify barriers to lowland moist forest regeneration in highly degraded grasslands in the Sierra Nevada de Santa Marta, Colombia, and show that these barriers include seed source, seed predation, competition with grasses, microclimate and soil limitations on plant growth, and fire.
Abstract: Extensive areas of the tropics have been converted into pasture for cattle ranching. Frequently, abandoned pasture does not revert to forest. The goal of this project was to identify barriers to lowland moist forest regeneration in highly degraded grasslands in the Sierra Nevada de Santa Marta, Colombia. The barriers we considered were seed source, seed predation, competition with grasses, microclimate and soil limitations on plant growth, and fire. Seed dispersal into the grasslands is limited to within 10 meters of forest fragments, but this barrier can be overcome by sowing seeds and planting seedlings and by establishing perches to attract dispersers. In these degraded grasslands, seed predation was lower than in the adjacent forest patches, and there was no evidence that grasses inhibited the establishment of woody species. The most important barrier was the severe degradation of the soils. In much of the area, the A and B horizons have been eroded away, leaving saprolite at the soil surface. Seedlings of two fast-growing pioneer species, Ochroma pyramidale and Cochlospermum vitifolium, grew to a maximum height of only 2.5 and 12 cm, respectively, during the first eight months. The slow plant growth in the degraded grassland soils compared to forest soils was associated with lower levels of cation-exchange capacity, calcium, magnesium, and potassium. Even if these barriers could be overcome, the frequent and extensive use of fire in the region must be controlled to avoid killing established woody plants.
337 citations
TL;DR: In this paper, the photothermal quotient (PTQ) and temperature were used to determine optimum heading dates and therefore, therefore, sowing dates for different spring wheat cultivars.
239 citations
TL;DR: The objective of this work was to study the effect of sowing date on growth and dry matter partitioning of maize crops grown without water and nutrients limitations.
Abstract: Changes in the environment that are associated with different sowing dates can be expected to alter maize (Zea mays L.) growth and development in temperate regions. The objective of this work was to study the effect of sowing date on growth and dry matter partitioning of maize crops grown without water and nutrients limitations. A commercial hybrid (DK636) was grown in the field at four sowing dates (mid-September through mid-December) for 3 yr [...]
178 citations
TL;DR: Effects of maize (Zea mays L.) plant density on weed interference in maize throughout the growing season is quantified to quantify effects of the relative competitive ability of the crop during serious phases of development on weed growth.
Abstract: Development of an integrated weed management system requires detailed information on crop-weed interactions, including the impact of the relative competitive ability of the crop during serious phases of development on weed growth. The objective of this study was to quantify effects of maize (Zea mays L.) plant density on weed interference in maize throughout the growing season. Experiments were carried out during 1990, 1991, and 1992 at the Elora Research Station, Elora, ON, on a London loam (Aquic Hapludalf) soil that had been tile drained. Maize was grown at three plant densities (4, 7, and 10 plants m −2 ) under three weed pressures. Weed pressures were established by varying the weedfree period after maize planting: all season (weed free), planting to 5to 7-leaf stage of maize (medium weed pressure), and planting to 3- to 4-leaf stage of maize (high weed pressure) [...]
171 citations
TL;DR: The objective was to study the effect of sowing date on the relationship between crop growth rates in the 4-wk-period bracketing silking and the components of final kernel number in maize.
Abstract: Kernel number in maize (Zea mays L.) depends on the physiological conditions of the crop at flowering. Our objective was to study the effect of sowing date on the relationship between crop growth rates in the 4-wk-period bracketing silking and the components of final kernel number. A commercial hybrid (DK636) was grown in the field at four sowing dates (mid-September, mid-October, mid-November, and mid-December) for 3 yr at INTA Balcarce Experimental Station, Argentina, at a density of 8.6 plants m -2 , without water and nutrients limitations [...]
126 citations
TL;DR: Field pea growth habit (cultivar) did not affect number of weeds, but increasing stand density (seed rate) reduced weed numbers in all 3 yr, and Herbicide application reduced weed dry matter production...
Abstract: Weed competition is a serious limitation to field pea (Pisum sativum L.) production. Trials were conducted in northeastern Saskatchewan to determine the effects of field pea growth habit, stand density and herbicide treatments on weed growth and on field pea stand and yield. Century, a long-stem leafy type, Tipu, a long-stem semi-leafless type, and Express, a short-stem leafy type, were seeded at 6, 12, 25, 50 and 100 seeds m−2. Some of each cultivar was unsprayed sprayed with a sethoxydim-metribuzin tank-mix for control of grass and broadleaf weeds. Field pea growth habit (cultivar) did not affect number of weeds, but increasing stand density (seed rate) reduced weed numbers in all 3 yr. Express reduced above-ground dry matter production of broadleaf weeds in 1988 and 1991. Increasing seed rate reduced above-ground dry matter production of weeds in all 3 yr. Field pea yield increased with increasing seed rate to a rate between 50 and 100 seeds m−2. Herbicide application reduced weed dry matter production...
83 citations
TL;DR: Dry matter partitioning and yield formation are key points for successful simulation of seed yield and increasing potential yield of the sunflower should focus on the improvement of the harvest index of the long-cycle hybrids.
73 citations
TL;DR: Seed priming has potential for improving seed germination and subsequent seedling establishment of canola seedlots with low germination, with low vigor, or when seeds are planted in cool (<10°C) soils.
Abstract: Some seedlots of canola (L. and L.) have low percentage germination and poor seedling vigor. The effect of priming canola on both seed germination and seedling emergence was investigated in controlled environment cabinets. Germination was investigated using petri dish assays, whereas emergence was studied by sowing seeds into pots containing a sandy loam soil. Seed germination and seedling emergence from soil at 10°C was enhanced for several cultivars of both species due to priming. Time to 50% germination and emergence was also reduced. A cv. Goldrush seedlot, which showed low germination in preliminary studies, was found to be particularly responsive to priming and, therefore, was used in subsequent studies to optimize the technique. The optimal priming time varied with temperature. Excellent responses occurred with priming for 14 to 16 h at 23°C or 60 h at 10°C. Temperature during priming had little effect on percentage germination, emergence percentage, or time to 50% germination or emergence. Seeds primed for 16 h at 23°C or for 60 h at 10°C initiated seedling emergence at 10°C 4 d earlier than nonprimed seeds. Seedling emergence of primed seeds was 73% compared with 31% for the nonprimed seeds. The benefits of priming on both percentage emergence and time to 50% emergence were reduced if the seeds were primed under anaerobic conditions. In addition, the leachate from primed seeds was inhibitory to both percentage germination and time to 50% germination, particularly at 10°C. The results obtained from this study indicate that seed priming has potential for improving seed germination and subsequent seedling establishment of canola seedlots with low germination, with low vigor, or when seeds are planted in cool (<10°C) soils.
73 citations
TL;DR: Environmental control plots adjusted to late season drought and elevated soil temperatures where inoculated at peanut planting with low and high levels of conidia, sclerotia, and mycelium from a brown conidial mutant ofAspergillus parasiticus, positively correlated with the incidence of seed infection in undamaged pods.
Abstract: Environmental control plots adjusted to late season drought and elevated soil temperatures where inoculated at peanut planting with low and high levels of conidia, sclerotia, and mycelium from a brown conidial mutant ofAspergillus parasiticus. Percentage infection of peanut seeds from undamaged pods was greatest for the subplot containing the high sclerotial inoculum (15/cm2 soil surface). Sclerotia did not germinate sporogenically and may have invaded seeds through mycelium. In contrast, the mycelial inoculum (colonized peanut seed particles) released large numbers of conidia into soil. Soil conidial populations of brownA. parasiticus from treatments with conidia and mycelium were positively correlated with the incidence of seed infection in undamaged pods. The ratio ofA. flavus to wild-typeA. parasiticus in soil shifted from 7:3 to 1:1 in the uninoculated subplot after instigation of drought, whereas in all subplots treated with brownA. parasiticus, the ratio of the two species became approximately 8:2. Despite high levels of brownA. parasiticus populations in soil, nativeA. flavus often dominated peanut seeds, suggesting that it is a more aggressive species. Sclerotia of wild-typeA. parasiticus formed infrequently on preharvest peanut seeds from insect-damaged pods.
64 citations
TL;DR: The experiment shows that high N applications can lead to high rice yields provided the microspores are protected from low temperatures by the use of deep water at the stage of microspore development, and recommendations for N fertiliser application need to be adjusted for sowing date and expected water depth at early pollenmicrospore.
Abstract: A field experiment was conducted to investigate the interaction of nitrogen (N) status, sowing date, and water depth on rice yield in the Murray Valley, New South Wales, where low minimum temperatures often lead to pollen sterility and low yield in high N status crops. The experiment combined 4 N rates (0, 75, 125, 250 kg N/ha) applied as urea just before permanent flood; 3 cultivars (Jarrah, early maturing; Amaroo and Doongara, midseason); 2 sowing dates (26 September, 31 October 1991); and 2 water depths (5, 20 cm) at the microspore stage. The early-sown crops and the later sown Jarrah crop encountered minimum air temperatures of 19¦C at the cold-sensitive microspore stage, compared with 15¦C for the other 2 later sown crops. Total dry matter production was little affected by either water depth or sowing date, but increased from 16 to 22 t/ha with N application. Shallow water depth and delayed sowing date affected yield through reduced harvest index. Grain yield response to N fertiliser was dependent on sowing date, water depth, and variety. For the early-sown crops grown in deep water, yields of Amaroo and Jarrah-increased from 7 to 13 t/ha with increasing N supply, while the yield response of Doongara plateaued at 9 t/ha. With shallow water, the yields of all varieties decreased from 7 to 3 t/ha with increasing N. For the later sowing date, Jarrah growing in deep water yielded up to 13 t/ha at high N, but yields of Amaroo and Doongara decreased from 7 to 2 t/ha with increasing N supply. For the later sowing date, yields of all varieties growing in shallow water decreased to <2 t/ha with applied N. In the deep water crops, developing microspores were submerged or partially submerged and so avoided low air minimum temperatures. In the early-sown crops, the microspore stage occurred during a period of relatively warm nights. Harvest index was successfully modelled using panicle temperature and N content at early pollen microspore. The experiment shows that high N applications can lead to high rice yields provided the microspores are protected from low temperatures by the use of deep water at the stage of microspore development. As a result, recommendations for N fertiliser application need to be adjusted for sowing date and expected water depth at early pollen microspore
TL;DR: The TMC prechill was applied to three conifer species, Douglas fir, Lodgepole pine, and Sitka spruce, and none of the seeds of any of the species germinated during the TMCprechill of up to 76 weeks at 4°C.
Abstract: Temperate conifer seeds are often considered to be shallowly dormant because a dormancy breakage treatment such as incubation of moist seeds at 4°C (prechilling) for 3–6 weeks improves germination. However, longer prechill durations can induce germination during the cold phase. Since the delicate radicles of prematurely germinated seeds are easily damaged and killed during sowing, potential benefits of extended prechilling are unknown.
TL;DR: This research was conducted to measure seed yield and seed quality of Maturity Group (MG) III and IV genotypes planted in early April of 1989 and 1990 under nonirrigated conditions at three locations in Arkansas.
Abstract: A new soybean [Glycine max (L.) Merr.] production system, in which early-maturing indeterminate cultivars are planted in early April, has been used by some growers in Arkansas and other Southern states. The intent is to escape late-season moisture deficits. This research was conducted to measure seed yield and seed quality (as determined by seed germination and viability) of Maturity Group (MG) III and IV genotypes planted in early April of 1989 and 1990 under nonirrigated conditions at three locations in Arkansas (approximately 34° to 36° N lat). Yields across the six environments averaged 1816 and 1992 kg ha −1 for four MG III and four MG IV cultivars, respectively. 'Williams 82' produced the highest average yield (2072 kg ha −1 ) in MG III and 'Competitor' produced the highest (2110 kg ha −1 ) in MG IV [...]
TL;DR: In this paper, the hyperbolic yield-density model was applied to phytomass and seed yield, and predictions and parameters of the model were used to quantify intra-and interspecific competition, and to evaluate yield potential of the mixtures.
TL;DR: This study investigated seed and plant development of 10 contrasting genotypes of pea with differences in seed size, foliage type, and number of branches, and found that seed water content was closely related to seed development.
Abstract: Pea (Pisum sativum L.) yields are generally highly dependent on seed number. The objective of the present study was to investigate seed and plant development of 10 contrasting genotypes of pea with differences in seed size (0.1-0.3 g seed -1 ), foliage type (semi-leafless and leafed), and number of branches. The periods of seed set and seed filling were studied in the field for 2 yr at two sowing dates. Seed water content (WC) was closely related to seed development (.)
TL;DR: In this paper, the authors investigated the effect of leaf nitrogen gradient on crop photosynthetic performance and radiation use efficiency in peanut canopies and found that the gradient appeared to be largely controlled by the light environment within the canopy, as evidenced by the commonality (across environments) of the relationship between SLN and cumulative light interception throughout the canopy.
Abstract: The allocation pattern of leaf nitrogen throughout a crop canopy can theoretically affect crop photosynthetic performance and radiation use efficiency (RUE). No information is available on the existence of leaf nitrogen gradients in peanut (Arachis hypogaea L.) canopies, nor on how these gradients might impact on RUE. Peanut crops (cv. Tifton-8) were grown in warm and cool environments, and the canopy profiles of leaf area index, light interception, specific leaf weight (SLW), leaf nitrogen concentration (LNC) and specific leaf nitrogen (SLN) were examined at 73 and 112 days after planting. Crop RUE was also measured during this period. There was a marked decline in SLN from the top to the base of the canopy in both environments. The gradient in SLN occurred due to changes in SLW and LNC in the warm environment, but only due to changes in SLW in the cool environment. The gradient appeared to be largely controlled by the light environment within the canopy, as evidenced by the commonality (across environments) of the relationship between SLN and cumulative light interception throughout the canopy. Radiation use efficiency was 33% higher in the crop grown in the warm compared to the cool environment, suggesting that cool temperatures can limit RUE in peanut. For the crop at the warm site, RUE was 32% higher than the theoretical RUE assuming a uniform SLN distribution in the canopy. It is suggested that the existence of non-uniform SLN distribution in the canopy may allow enhanced RUE compared to canopies with uniform SLN distribution.
TL;DR: The foundation of a successful revegetation or restoration program is quality native seed, which requires careful collection, processing, and storage of mature seed from healthy, local stands with a sufficiently broad genetic base.
Abstract: The foundation of a successful revegetation or restoration program is quality native seed. This requires careful collection, processing, and storage. Mature seed should be collected from healthy, local stands with a sufficiently broad genetic base. Careful identification of the site characteristics and seed-lot tracking are essential. Yearly variation in seed production and seed quality can be very high, and an early determination of seed quality can prevent expensive failures. Nondestructive evaluation using X-rays is effective and economical, but techniques such as staining, inspection, and germination tests can also be helpful. Cleaning, dewinging, and upgrading seed before storage can (1) reduce weight and bulk, (2) improve storage life, (3) increase germination, and (4) make greenhouse production and field planting easier and more economical. The seeds of many native plants can lose their viability quickly if they are not stored under controlled conditions. Seeds in storage must also be protected from rodents, pests, and disease. Dormancy is common in the seeds of many native species, and experimentation is often necessary to determine the best way to break seed dormancy. This can be complicated by year-to-year and plant-to-plant variation.
TL;DR: In this paper, gas exchange and dry-weight production in Opuntia ficus-indica, a CAM species cultivated worldwide for its fruit and cladodes, were studied in 370 and 750 μmol mol−1 CO2 at three photosynthetic photon flux densities (PPFD: 5, 13 and 20 mol m−2 d−1).
Abstract: Gas exchange and dry-weight production in Opuntia ficus-indica, a CAM species cultivated worldwide for its fruit and cladodes, were studied in 370 and 750 μmol mol−1 CO2 at three photosynthetic photon flux densities (PPFD: 5, 13 and 20 mol m−2 d−1). Elevated CO2 and PPFD enhanced the growth of basal cladodes and roots during the 12-week study. A rise in the PPFD increased the growth of daughter cladodes; elevated CO2 enhanced the growth of first-daughter cladodes but decreased the growth of the second-daughter cladodes produced on them. CO2 enrichment enhanced daily net CO2 uptake during the initial 8 weeks after planting for both basal and first-daughter cladodes. Water vapour conductance was 9 to 15% lower in 750 than in 370 μmol mol−1 CO2. Cladode chlorophyll content was lower in elevated CO2 and at higher PPFD. Soluble sugar and starch contents increased with time and were higher in elevated CO2 and at higher PPFD. The total plant nitrogen content was lower in elevated CO2. The effect of elevated CO2 on net CO2 uptake disappeared at 12 weeks after planting, possibly due to acclimation or feedback inhibition, which in turn could reflect decreases in the sink strength of roots. Despite this decreased effect on net CO2 uptake, the total plant dry weight at 12 weeks averaged 32% higher in 750 than in 370 μmol mol−1 CO2. Averaged for the two CO2 treatments, the total plant dry weight increased by 66% from low to medium PPFD and by 37% from medium to high PPFD.
TL;DR: A substantial decrease in the amount of mulch was observed during the growing season and resulted in little difference between mulch and no mulch sown in a rye cover/soybean system.
Abstract: The optimum killing time of a rye (Secale cereale) cover crop is an important management decision and can determine the yield of the subsequent soybean (Glyane max) crop The objective of this research was to study a rye cover/soybean system. Soybeans were grown on sandy (Delhi) and loam (Woodstock) soils (1989/1990) with mulch on the soil surface obtained by killing rye approximately 1 and 2 wk before soybean planting. A conventional tillage treatment was used as a control. Soil water content, soil temperature, rye mulch amount and soybean growth were monitored over the season. Rye mulch amount for the late killing (LK) date was always larger than for the ear y killing (EK) date. LK decreased soil water content at soybean planting time at Delhi in 1989. The rye mulch produced with the LK increased soil water content early in the soybean growing season in 1990. A substantial decrease in the amount of mulch was observed during the growing season and resulted in little difference between mulch and no mulch s...
TL;DR: Bluebunch wheatgrass is an important native bunchgrass often planted in the Intermountain and Pacific Northwest regions and the cultivar 'Goldar' was evaluated for germination rate, seedling emergence and growth, and seed weight.
Abstract: Development of plant materials adapted to the demands of a harsh environment and conditions created by standard planting practices has resulted in improved seedling establishment for some species. Bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] Love) is an important native bunchgrass often planted in the Intermountain and Pacific Northwest regions. Though cultivars have been developed, this species continues to have a reputation for weak seedlings. Forty-seven accessions of bluebunch wheatgrass collected from naturally occurring populations in 9 geographic regions and the cultivar 'Goldar' were evaluated for germination rate, seedling emergence and growth, and seed weight. Significant differences in seed weight and germination rate at optimum (15/25 degrees C) and cold (1 degree C) temperatures were observed. Seedling emergence from a 4-cm depth ranged from 5 to 66%. Mean dry shoot weight 28 days after planting varied among accessions by a factor of 6. Simple correlations between seed weight and percentage emergence (r = 0.62) and seed weight and mean shoot weight (r = 0.63) indicate seed weight could be used as a preliminary screening test for these traits. Seed weight was not useful in predicting germination rate. Results suggest establishment success may be improved through careful selection for traits associated with seedling vigor.
TL;DR: It is suggested that the nutrient level in seed exudates is the primary reason for the differences observed among seeds and the timing and difference in expression of phenazine biosynthesis on seeds have implications for the potential efficacy of biocontrol microorganisms against plant pathogens.
Abstract: A derivative of Pseudomonas aureofaciens PGS12 expressing a promoterless ice nucleation gene under the control of a phenazine biosynthesis locus was used to study the expression of a phenazine antibiotic locus (Phz) during bacterial seed colonization. Seeds of various plants were inoculated with wild-type PGS12 and a PGS12 ice nucleation-active phz:inaZ marker exchange derivative and planted in soil, and the expression of the reporter gene was monitored at different intervals for 48 h during seed germination. phz gene expression was first detected 12 h after planting, and the expression increased during the next 36-h period. Significant differences in expression of bacterial populations on different seeds were measured at 48 h. The highest expression level was recorded for wheat seeds (one ice nucleus per 4,000 cells), and the lowest expression level was recorded for cotton seeds (one ice nucleus per 12,000,000 cells). These values indicate that a small proportion of bacteria in a seed population expressed phenazine biosynthesis. Reporter gene expression levels and populations on individual seeds in a sample were lognormally distributed. There was greater variability in reporter gene expression than in population size among individual seeds in a sample. Expression on sugar beet and radish seeds was not affected by different inoculum levels or soil matric potentials of -10 and -40 J/kg; only small differences in expression on wheat and sugar beet seeds were detected when the seeds were planted in various soils. It is suggested that the nutrient level in seed exudates is the primary reason for the differences observed among seeds. The lognormal distribution of phenazine expression on seeds and the timing and difference in expression of phenazine biosynthesis on seeds have implications for the potential efficacy of biocontrol microorganisms against plant pathogens.
TL;DR: The objective was to find a simple technique to germinate seed of each species so that such a technique can be applied under village conditions in Malawi.
TL;DR: Grain yield was reduced by about 16% when forage was removed at stage 30 and by nearly 33% at stage 31, and grain-yield reductions following forage removal may be attributed to grain-weight decreases caused by a prolonged cycle to anthesis.
TL;DR: Recommendations for management of CMV infection in lupins are supported by sowing seed with low infection (<0.5%) to minimize infection sources, and sowing early at high seeding rates to remove seed-infected plants through improved canopy formation.
Abstract: During 1990-92, narrow-leafed lupins (Lupinus angustifolius) cv. Gungurru, were grown in six field experiments in which plots were sown with healthy seed or seed that carried 0.5-5% infection with cucumber mosaic virus (CMV). Seed-infected plants were the primary source for subsequent virus spread by aphids. The rate of CMV spread and the extent of infection in plots depended on the level of infection in the seed sown, the proportion of infected seeds that successfully developed into established plants and the time of arrival and number of aphid vectors. In general, higher seed infection levels, better establishment of seed-infected plants and early aphid arrival favoured greater virus spread, yield loss and infection in the harvested seed. In 1991, in two experiments, late arrival of aphids resulted in minimal CMV spread, no effect on yield and much less infection in the harvested seed than in the seed sown. In the other four experiments, significant yield losses (25-42%) always resulted when seed with 5% or 3% infection was sown. Sowing 1% infected seed resulted in significantly decreased yields in two experiments, while 0.75% and 0.5% infected seed caused significant losses in one experiment (16-19% losses). Yield decreases were due to both fewer seeds being formed and decreased seed size. Levels of infection in harvested seed did not exceed 15%. In a further field experiment in 1991, individual plants that developed CMV symptoms before initiation of flowering or during flowering had significantly smaller yields than those that developed symptoms after flowering had finished. In four field experiments during 1990-91, 10-15% CMV-infected lupin seed was sown at rates of 20-150 kg ha-' to generate a range of plant densities. The numbers of seed-infected plants were recorded at different times. The extent of loss of seed-infected plants due to shading by neighbouring healthy plants depended on plant density and the time when canopy closure developed. Where no canopy formed there was little or no loss of seed-infected plants, while early canopy formation at high plant density was most effective in removing them. Current-season spread was also decreased by early canopy formation and high plant density, but this effect was smaller when aphids arrived early. This work supports recommendations for management of CMV infection in lupins by sowing seed with low infection (<0.5%) to minimize infection sources, and sowing early at high seeding rates to remove seed-infected plants through improved canopy formation.
TL;DR: It is concluded that hot wire presowing treatment is worth considering as an alternative to sulphuric acid because of safety problems associated with handling the acid.
TL;DR: Different aspects of seedling recruitment in Actaea spicata were investigated in deciduous and mixed coniferous forests in central Sweden, implying that, in general, local seed dispersal is very limited, and that clustering in adult A. Spicata populations reflects local seed disperseal pattern.
TL;DR: Effects of N level and time of N increase were consistently significant for most crop responses, and an increase in seed oil content was accompanied by a decrease in seed protein.
Abstract: Effects of N level (15 to 30 mM), time of N increase (14 to 28 days after planting), and planting density (1163 to 2093 plants/m2) were determined for crop yield responses of dwarf, rapid-cycling brassica (Brassica napus L., CrGC 5-2, Genome: ACaacc). Crops were grown in solid-matrix hydroponic systems and under controlled-environment conditions, including nonsupplemented (ambient) or elevated CO2 concentrations (998 +/- 12 micromoles mol-1). The highest seed yield rate obtained (4.4 g m-2 day-1) occurred with the lowest N level (15 mM) applied at the latest treatment time (day 28). In all trials, CO2 enrichment reduced seed yield rate and harvest index by delaying the onset of flowering and senescence and stimulating vegetative shoot growth. The highest shoot biomass accumulation rate (55.5 g m-2 day-1) occurred with the highest N level (30 mM) applied at the earliest time (day 14). Seed oil content was not significantly affected by CO2 enrichment. Maximum seed oil content (30% to 34%, dry weight basis) was obtained using the lowest N level (15 mM) initiated at the latest treatment time (day 28). In general, an increase in seed oil content was accompanied by a decrease in seed protein. Seed carbohydrate, moisture, and ash contents did not vary significantly in response to experimental treatments. Effects of N level and time of N increase were consistently significant for most crop responses. Planting density was significant only under elevated CO2 conditions.
01 Jan 1994
TL;DR: A high rate of blossoming seedlings enabled the completion of selection for all the important breeding objectives including the resistance to scab, mildew and fire blight within 6 years after sowing the seeds.
Abstract: A very important aim for the acceleration of the breeding progress in apple is the development of methods for shortening the juvenile period. The period from sowing the seeds to the first bloom of the seedlings can take from 5 to 12 years. Only then we can begin with the complete evaluation of the progenies. Various cultivation methods were considered at the Pillnitz Institute. The basic idea is to grow the seedlings rapidly from the germination stage to the change from the juvenile to the adult stage. The best method appeared to be cultivation in the greenhouse under 16 hours light per day. At a minimum height of 180 cm graftsticks of each seedling were cut and grafted in April in the field on M9 rootstocks with Hibernal interstem. This way the growth was controlled and blossoming began earlier. Fruit size was normal and not smaller as on M 27. A few grafted seedlings began to blossom in the year of grafting. In the second year after grafting 20–25% blossomed, in the third year 65–85%, and in the fourth year nearly 95%. This high rate of blossoming seedlings enabled the completion of selection for all the important breeding objectives including the resistance to scab, mildew and fire blight within 6 years after sowing the seeds.
TL;DR: The seeds of both species exhibited dormancy, although to different degrees, caused by impermeable hard seed coats, and it is recommended that untreated seeds should be used at a higher sowing density to compensate for the dormancy until a cheap, safe, convenient and rapid method of germination is found.
TL;DR: Quality parameters were measured in two seasons for seeds produced from early and late crops of garden pea (Pisum sativum L.) ‘Pania’ as both conductivity and hollow heart were greater in seeds from the November sown crop, and as a consequence, expected field emergence (EFE) was significantly lower.
Abstract: Quality parameters were measured in two seasons for seeds produced from early (sown November, harvested January) and late (sown December, harvested February) crops of garden pea (Pisum sativum L.) ‘Pania’. Harvest was by hand at 15% seed moisture content (SMC). Time of sowing had no effect on the germination of the seeds produced, but did affect seed vigour as both conductivity and hollow heart were greater in seeds from the November sown crop, and as a consequence, expected field emergence (EFE) was significantly lower. At a 40% SMC harvest in the second year of study, germination and conductivity did not differ between the two sowing dates and so the EFE also did not differ significantly. However as harvest was delayed until 25 and 15% SMC, there was a higher hollow heart incidence and higher conductivity in seeds from the early crop compared with the late crop. Seeds from the November sowing encountered greater climatic extremes (temperature, rainfall, and relative humidity) during their matur...