Showing papers on "Sowing published in 2001"

Suppression of weeds by spring wheat Triticum aestivum increases with crop density and spatial uniformity

Abstract: Summary 1. Recent advances in our understanding of the advantage of initial size in competition among individual plants (size-asymmetric competition) suggest that the potential for many crops to suppress weeds is much greater than generally appreciated. We hypothesize that this potential can be realized if: (i) the crop density is increased significantly and (ii) the crop is regularly (uniformly) distributed in two-dimensional space rather than sown in traditional rows. 2. We tested these hypotheses by sowing four varieties of spring wheat Triticum aestivum at three densities (200, 400 and 600 m ‐2 ) and in two spatial patterns (normal rows and a uniform grid pattern) in the presence of high weed pressure. 3. There were strong and significant effects of both crop density and spatial distribution on weed growth. Weed biomass decreased with crop density and was 30% lower in the grid pattern. 4. There was a negative linear relationship between above-ground weed biomass in early July and crop yield at harvest, so weed suppression translated directly into yield. The treatment with high crop density and the grid sowing pattern contained 60% less weed biomass and produced 60% higher yield than the treatment closest to normal sowing practices (crops sown in rows at 400 m ‐2 ).

Suppression of specific apple root pathogens by Brassica napus seed meal amendment regardless of glucosinolate content.

Abstract: The impact of Brassica napus seed meal on the microbial complex that incites apple replant disease was evaluated in greenhouse trials. Regardless of glucosinolate content, seed meal amendment at a rate of 0.1% (vol/vol) significantly enhanced growth of apple and suppressed apple root infection by Rhizoctonia spp. and Pratylenchus penetrans. High glucosinolate B. napus cv. Dwarf Essex seed meal amendments did not consistently suppress soil populations of Pythium spp. or apple root infection by this pathogen. Application of a low glucosinolate containing B. napus seed meal at a rate of 1.0% (vol/vol) resulted in a significant increase in recovery of Pythium spp. from apple roots, and a corresponding reduction in apple seedling root biomass. When applied at lower rates, B. napus seed meal amendments enhanced populations of fluorescent Pseudomonas spp., but these bacteria were not recovered from soils amended with seed meal at a rate of 2% (vol/vol). Seed meal amendments resulted in increased soil populations of total bacteria and actinomycetes. B. napus cv. Dwarf Essex seed meal amendments were phytotoxic to apple when applied at a rate of 2% (vol/vol), and phytotoxicity was not diminished when planting was delayed for as long as 12 weeks after application. These findings suggest that B. napus seed meal amendments can be a useful tool in the management of apple replant disease and, in the case of Rhizoctonia spp., that disease control operates through mechanisms other than production of glucosinolate hydrolysis products.

Participatory evaluation by farmers of on-farm seed priming in wheat in india, nepal and pakistan

Abstract: The mean time for 50% germination at 20°C of 12 Indian wheat (Triticum aestivum) cultivars was nearly halved, from 51 h to 27 h, by soaking seed in water for 8 h prior to sowing. A delay of 24 h without further soaking, intended to simulate postponement of sowing, reduced the time saved by priming to 16%. Priming had no effect on final germination percentage. These results were used in the design of 275 on-farm, farmer-managed, participatory trials of seed priming in wheat during the 1997-98 and 1998-99 rabi (post-monsoon) seasons. In forty-one trials in tribal areas of Bihar and West Bengal states of India, seed priming gave a 13% grain yield advantage for farmers growing wheat in marginal areas with low levels of agricultural inputs. Mean benefits from seed priming of wheat in nine trials in Chitwan, Nepal were 17%. In high potential areas of Gujarat, India, 205 trials had higher rates of input use. Yield benefit from priming in these trials averaged only 5% but constituted an extra 200 kg ha -1 grain at little or no cost. In 20 trials on marginal land, with slightly saline irrigation water in Ahmadwala, Pakistan, an average yield increase of 36% was obtained using seed primed with a 0.2% gypsum solution. Collaborating farmers reported that priming wheat seed overnight resulted in faster, more complete emergence, more vigorous early growth, better tillering, earlier flowering, larger ears, earlier maturity and higher yields. In addition, many farmers also reported that foliage in primed plots was a darker shade of green than that in non-primed plots, suggesting that primed plants may have been using nitrogen more efficiently. Seed priming was popular with farmers, most of whom reported that they would prime wheat seed the following year. A survey in Gujarat in 1998-99 of 63 farmers who had tested priming in 1997-98 showed that, while 65% had primed some of their own seed, none had primed more than 50 kg, suggesting that there were practical difficulties in priming larger volumes of seed.

Colonization of grassland by sown species: dispersal versus microsite limitation in responses to management

Abstract: Summary 1 Diversification of species-poor grassland often requires the introduction of desirable species by sowing seed. Little is known about the factors controlling the spread of introduced species, or how these interact with management. We determined whether management affected spread rates of two grassland species by modifying seed dispersal or seedling establishment. 2 An experiment was set up in 1995 on a species-poor grassland. It comprised five blocks, each with four treatments: (1) autumn grazed only; (2) cut July; (3) cut July and September; (4) cut July and aftermath grazed. Twenty-two plant species were separately slot-seeded into each treatment plot, providing discrete linear colonization foci. 3 The mechanisms controlling spread were studied in two species: Rhinanthus minor, an annual with large seeds adapted for wind dispersal; and Leucanthemum vulgare, a perennial with small seeds with no obvious dispersal adaptations. 4 Perpendicular spread of each species by 1998 was described well by a simple inverse power model. Rhinanthus had spread further in the hay-cut treatments (2–4) than in the grazed treatment (1). Leucanthemum spread poorly in all plots, with no treatment effects. 5 Seed dispersal from source slots was also described well by the inverse power model. Dispersal curves for Rhinanthus were much longer in the hay-cut treatment (3) than in the grazed treatment (1), because more seed dispersed during hay cutting than before, and cutting dispersed seed longer distances. There was no dispersal by grazing animals. Dispersal showed directional effects: seeds travelled further in the prevailing wind direction before the hay-cut and in the grazed treatment; dispersal by hay cutting was further in the cut direction than in the opposite direction. 6 Leucanthemum showed poor dispersal, with no treatment effects, except that more seeds were dispersed in the grazed (1) than the hay-cut (3) treatment. 7 The establishment and survival of sown seeds showed no treatment effects for either species. 8 Management effects on the spread of Rhinanthus reflected effects on dispersal, rather than establishment. Leucanthemum showed poor dispersal but good establishment in all treatments, suggesting its spread may also have been dispersal-limited. Rhinanthus was positively affected by hay cutting because it set seed at the time of cutting, whereas Leucanthemum set seed later and cutting reduced its seed production. 9 The results indicate that management of grassland to enhance the colonization of sown species might be best targeted at enhancing seed-dispersal distances. Hay cutting can do this, but must coincide with seed set.

Effects of Cereal and Legume Cover Crop Residues on Weeds, Yield, and Net Return in Soybean (Glycine max)1

Abstract: A 2-yr field study was conducted during 1998 and 1999 at Stoneville, MS, on a Dundee silt loam to determine weed control, yield, and net return associated with winter cover crops in soybean. Cover crop systems included Italian ryegrass, oat, rye, wheat, hairy vetch, crimson clover, subterranean clover, no-cover crop conventional tillage (CT), and no-cover crop no-tillage (NT), all with standard preemergence (PRE), postemergence (POST), PRE + POST, and no-herbicide weed management. Oat (11.1 Mg/ha) had highest dry biomass compared to all other cover crops (6.0 to 7.6 Mg/ha) at soybean planting. Biomass decreased 9 wk after planting (WAP) compared to the respective biomass at soybean planting in all cover crops. Italian ryegrass and rye biomass decay was slow and about two-thirds of plant residue persisted at 9 WAP. Cover crops had no effect on densities of barnyardgrass, prickly sida, and yellow nutsedge, but altered the density of browntop millet. Total weed biomass was higher in rye, wheat, and subterran...

Weed suppression by annual legume cover crops in no-tillage corn

Abstract: Cover crops often reduce density and biomass of annual weeds in no-till cropping systems. However, cover crops that over-winter also have the potential to reduce crop yield. Currently, there is an interest in annual medics (Medicago spp.) and other annual legumes that winter-kill for use as cover crops in midwestern grain cropping systems. A 2-yr study was conducted at East Lansing and the Kellogg Biological Station, Michigan, to investigate the influence of annual legume cover crops on weed populations. Two annual medic species [burr medic (M. polymorpha cv. Santiago) and barrel medic (M. truncatula Gaertn. cv. Mogul)], berseem clover (Trifolium alexandrinum L. cv. Bigbee), and medium red clover (Trifolium pratense L.) were no-till seeded as cover crops into winter wheat (Triticum aestivum L.) stubble in a winter wheat/corn (Zea nays L.) rotation system. Density of winter annual weeds were between 41 and 78% lower following most cover crops when compared with no cover control in 2 out of 4 site years, while dry weight was between 26 and 80% lower in all 4 site years. Impact of cover crops on the density of summer annual weeds was infrequent; however, weed dry weights were reduced by 70% in 1995 following burr medic and barrel medic. Dry weight of perennial weeds before corn planting were 35 to 75% lower following annual legumes compared with the control, while weed density was not affected. This study indicated a potential for annual legumes to reduce weed density and growth in no-till corn grain systems.

Effects of sowing time and nitrogen fertiliser on canola and wheat, and nitrogen fertiliser on Indian mustard. I. Dry matter production, grain yield, and yield components

Abstract: Canola, Indian mustard, and wheat were grown under dryland conditions at Ariah Park and Cowra (canola only) in the cropping belt of New South Wales, Australia, to determine the effects of sowing time (canola and wheat) and nitrogen (N) fertiliser on the growth, grain yield, and yield components of the crops. Compared with an April sowing, the grain yield of canola at Ariah Park was reduced by 35% for a May sowing and by 67% for a July sowing. Canola yield at Cowra was reduced by 45% between early and late May sowings. Wheat yield declined by 35% between the May and July sowings at Ariah Park. Grain yields of canola and wheat at Ariah Park responded to N fertiliser in the April and May sowings, but not in the July sowing. Indian mustard had a higher yield than the comparable sowing of canola. Canola yields at Cowra were more responsive to N fertiliser than at Ariah Park, and increased from 0.5 to 2.9 t/ha with 100 kg N/ha. For each day that sowing canola was delayed at both sites after April-early May, anthesis was delayed on average by 0.52 days. For Dollarbird wheat, the delay in anthesis was 0.39 days per day sowing was delayed. Dry matter accumulation by the oilseeds was greatest during flowering, but before anthesis for wheat. Late sowing had little effect on the proportions of dry matter accumulated in a particular growth period. Irrespective of sowing time, grain yields and dry-matter harvest indices of the oilseeds were similar to values for wheat when differences in the biosynthetic costs of grain and straw production were taken into account. Late sowing usually resulted in a greater reduction in canola oil concentration than high N fertiliser rates. Canola oil concentration was reduced by 1.7 percentage points per 1°C increase in mean temperature during grain filling as a result of sowing late. It was concluded that N fertiliser could not compensate for the yield reduction in canola and wheat due to sowing late. Early sowing was essential to achieve high oil levels in canola. Additional keywords: Brassica juncea, Brassica napus, dry-matter harvest indices, oil concentration, oilseed rape. AR011 Poctapp Pck S C, wan musr

Straw Production and Grain Yield Relationships in Winter Wheat

Abstract: use of traditional intensive tillage practices during fallow (Papendick, 1998). During most years, use of summer Winter wheat (Triticum aestivum L.) ‐fallow is the predominant fallow allows growers to sow winter wheat into adequate cropping system in low-precipitation regions (,250 mm annually) of the inland Pacific Northwest (PNW) in the USA. Wind erosion is a carryover soil water for seed germination during midrecurrent problem during and after fallow periods when inadequate to-late August. Sowing must sometimes be delayed due crop residue amounts are retained on the soil surface. Management to insufficient seed‐zone soil water (Schillinger et al., options that optimize both grain yield and straw production are 1998), or the need to control winter annual grass weeds needed. A 3-yr field study was conducted to determine sowing rate (Ogg, 1993). Early stand establishment is an important and sowing date effects on straw and grain yield, and grain yield factor for increasing grain yield, and it is strongly influcomponents of winter wheat cultivars with semidwarf, standard height, enced by seed‐zone water content and depth of soil or tall growth habit. Four winter wheat cultivars were evaluated at covering the seed (Lindstrom et al., 1976). Because of three sowing rates (65, 130, and 195 seeds m2 2 ) and three sowing frequent dry seed‐zone conditions and the need for dates in August, September, and October. A split plot design was seedlings to emerge from deep sowing depths, tall and

Tillage, cover crop, and kill-planting date effects on corn yield and soil nitrogen

Abstract: Tillage and spring kill date may affect cover crop N accumulation and subsequent N release to the soil, thereby influencing corn (Zea mays L.) N uptake and yield. We examined the influence of three tillage practices [no till (NT), chisel plowing (CP), and moldboard plowing (MP)], two cover crop management systems [hairy vetch (Vicia villosa Roth) vs. winter weeds], and two cover crop kill-corn planting dates [early (early April cover crop kill and mid to late April corn planting) vs. late (mid to late April cover crop kill and late April to early May corn planting)] on cover crop N accumulation, soil inorganic N, and silage corn N uptake and yield. An experiment was conducted on a Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1997 to 1999 in central Georgia. Cover crop N accumulation was higher with late kill than with early kill (113 vs. 104 kg ha -1 ). Corn yield was higher with late planting in NT than in CP or MP (19.5 vs. 15.1-16.6 Mg ha -1 ) and higher in CP or MP with early planting than in MP with late planting (18.1-18.4 vs. 15.1 Mg ha -1 ). Similarly, corn N uptake was higher in NT with late planting than in CP or MP with early or late planting (217 vs. 133-171 kg ha -1 ). Soil inorganic N (0- to 30-cm depth) at corn planting was higher in CP than in NT (18.4-30.2 vs. 9.9-20.5 mg kg -1 ). Corn yield and N uptake in NT and N concentration and uptake in CP and MP can be increased by delaying cover crop kill by 2 wk, but corn yield in CP and MP can be maintained by killing cover crop early in the spring.

Short duration chickpea to replace fallow after aman rice: the role of on-farm seed priming in the high barind tract of bangladesh

Abstract: Chickpea (Cicer arietinum) is a promising post-wet-season crop to follow rainfed rice (Oryza sativa) in the High Barind Tract of northwestern Bangladesh. Yields in farmers' fields, however, remain low (<1 t ha-1) primarily due to factors such as poor crop establishment, late sowing, and terminal drought and heat stress. Having been shown to improve plant stand and yield of chickpea in other environments, seed priming - soaking the seed overnight before surface drying and sowing the next day - of chickpea cv. Barichola-2 was tested for its efficacy under Barind conditions. In the 1998-99 season, 30 trials, grown entirely on residual soil moisture were conducted in farmers' fields in districts of Rajshahi and Nawabganj. A statistically significant mean yield response to priming of 47% was obtained. In 1999-2000, 105 on-farm trials (in Rajshahi, Nawabganj, Noagaon and Niamatpur) and 15 demonstrations (in Godagari) comparing presence and absence of priming were conducted. The crop received rain during this growing season. In a randomly chosen subset of 35 trials, scientists recorded a mean yield increase due to priming of 20%; it was 22% (from 1.02 to 1.25 t ha-1) in the remaining 64 trials (6 of the 105 trials were abandoned) where farmers recorded yields. Using a different cultivar (Barichola-5), the mean yield response to priming in 15 demonstrations was 17% (from 1.25 to 1.46 t ha-1). The priming response was attributed mainly to rapid seedling establishment, with higher plant stand and earlier crop maturity allowing escape from end-of-season stresses. Priming also reduced the incidence of stem and root diseases, and increased nodulation by native rhizobia. This simple technology can substantially increase chickpea yields to remunerative levels for the resource-poor farmers in this difficult environment. Furthermore, it is suggested that this technology can act as a catalyst for the introduction of further technologies that will permit reliable and profitable cultivation of post-rainy-season crops and thus improve the livelihoods of the rural population

Effects of seed dispersal on Juniperus communis recruitment on a Mediterranean mountain

Abstract: . The recruitment of the relict shrub Juniperus communis on a mountain in SE Spain was studied during the period 1994–1998. The main objective was to determine both the quantitative and qualitative effects of bird dispersal on seedling establishment. Seed removal by birds, seed rain, post-dispersal seed predation, germination, and seedling emergence and survival were analysed in different microhabitats. Birds removed 53 - 89% of the seeds produced by plants. Seed rain was spatially irregular as most seeds accumulated near stones used by birds as perches and below mother plants while a few seeds were dropped in wet meadows and open ground areas. Post-dispersal seed predation by rodents affected < 10% of dispersed seeds but varied significantly among microhabitats. Only 3.6 - 5.5% of dispersed seeds appeared viable, as many seeds had aborted or showed wasp damage. Seeds germinated in the second and third springs after sowing, reaching a germination percentage of 36%. Seedling emergence was concentrated in wet meadows. Seedling mortality was high (75–80%), but significantly lower in wet meadows, the only microhabitat where seedlings could escape from summer drought, the main mortality cause. Seed abortion, germination and seedling mortality proved to be the main regeneration constraints of J. communis on Mediterranean mountains. Birds exerted a strong demographic effect, although their qualitative effect was limited by abiotic factors which caused the pattern of seed rain to differ from the final pattern of recruitment between microhabitats.

The effects of elevated CO2 on seed production and seedling recruitment in a sheep-grazed pasture.

Abstract: Seed production and seedling recruitment were measured over 2 years under ambient (360 ppm) and elevated (475 ppm) atmospheric CO2 in a free air carbon dioxide enrichment (FACE) experiment, carried out in a sheep-grazed pasture on dry, sandy soil in New Zealand. In both years elevated CO2 led to more dispersed seeds of the grasses Anthoxanthum odoratum, Lolium perenne and Poa pratensis, the legumes Trifolium repens and T. subterraneum and the herbs Hypochaeris radicata and Leontodon saxatilis. The increased seed dispersal in A. odoratum, H. radicata, Leontodon saxatilis and T. repens reflected both more inflorescences per unit area and more seeds per inflorescence under elevated CO2. The increased seed dispersal in Lolium perenne, P. pratensis and T. subterraneum was due solely to more inflorescences per unit area. The number of seedlings that emerged and survived to at least 7 months of age was increased by elevated CO2 for H. radicata, Leontodon saxatilis, T. repens and T. subterraneum in both years and for A. odoratum and Lolium perenne in the first year. For species where increased seedling recruitment was noted, there was a significant positive correlation between seed production in summer and seedling emergence in the following autumn and winter, and sowing 200 extra seeds per species m–2 resulted in more seedlings compared to unsown controls. Elevated CO2 did not affect seedling survival in any species. There was no measurable effect of elevated CO2 on canopy and soil surface conditions or soil moisture at the time of seedling emergence. The results suggest the dominant effect of elevated CO2 on seedling recruitment in this pasture was an indirect one, reflecting effects on the number of seeds produced. The biomass of H. radicata, Leontodon saxatilis, T. repens and T. subterraneum in the above-ground vegetation was greater under elevated than ambient CO2. However, the size of individual seedlings and mature plants of these four species was unaffected by elevated CO2. The results indicate an important way elevated CO2 influenced plant species composition in this pasture was through changes in the pattern of seedling recruitment.

Changes in weed community composition as influenced by cover crop and management system in continuous corn

Abstract: Weed suppression by cover crops grown during the winter fallow period in continuous corn may lead to a reduction in herbicide use. Rye, crimson clover, and subterranean clover cover crops were compared with corn stubble under a conventional management system (CS) that included plowing and use of preemergence residual herbicides and a low-input management system (LIS) that included no-tillage and use of a presowing nonresidual herbicide for three consecutive years (1994–1996). Cover crop and above-ground weed biomass prior to desiccation were not influenced by management system. Cover crop biomass ranged from 1,420 to 5,657 kg ha−1 for rye, from 563 to 4,217 kg ha−1 for crimson clover, and from 563 to 4,248 kg ha−1 for subterranean clover. At crop planting, rye reduced weed biomass from 54 to 99%, crimson clover from 22 to 46% (with a negative value in 1995), and subterranean clover from 21 to 67%. Weed growth suppression was usually higher in years when cover crop biomass was higher. There were n...

Seed Coating Technologies and Treatments for Onion: Challenges and Progress

Abstract: Conventional methods to control the onion maggot or onion fly, Delia antiqua (Meigen), have relied on in-furrow applications of the toxicant pesticide, chlorpyrifos. The objective of this research was to develop an onion (Allium cepa L.) seed treatment that utilizes a new chemistry compound that is environmentally safe. Cyromazine is an insect growth regulator with a mode of action different from traditional pesticides used to control onion maggot. Cyromazine has low mammalian toxicity and is relatively nontoxic to other insects, including beneficials. High seed loading rates (50 g.kg -1 active ingredient) are required for optimal efficacy, and conventional slurry methods are inadequate to apply these high loading rates. Film coating and pelleting were performed at Cornell Univ. to apply cyromazine and a registered fungicide (a formulation of thiram and carboxin) to onion seeds. Results of field studies performed over several years revealed that stand losses due to the onion maggot ranged from 20% to 60%. Cyromazine applied by either film coating or pelleting decreased the loss by onion maggot from 1% to 8%, and efficacy was comparable to an in-furrow application ofchlorpyrifos. Cyromazine was registered as a seed treatment and is commercially used in the northeastern and midwestern United States, where onion maggot is a serious pest. Field emergence was not negatively affected by cyromazine coated onto the seeds when onion seeds are sown in organic (muck) soils. There is other evidence, however, that cyromazine seed treatments may cause phytotoxicity to germination and seedling growth. Testing seed quality in sand or on roll towels revealed a high percentage of abnormal seedlings. Retarded root growth was observed in seeds treated with cyromazine, resulting in an increase in abnormal seedling classifications. A finely ground sphagnum peatmoss applied over the seeds in a roll towel test ameliorated the abnormal root growth symptoms, and seedlings had robust growth. Collectively, film coating and pelleting were effective delivery systems for the application of plant protectants required at time of sowing. Modification of the standard germination test was needed to accurately assess onion seed quality. Moreover, this project was successful due to a team effort of a university seed scientist and entomologists working with onion growers and industry. Future registrations on small acreage, high-value horticultural crops are envisioned to require similar multi-partner approaches.

Planting Date and Foliar Fungicide Effects on Yield Components and Grain Traits of Winter Wheat

Abstract: In the eastern Great Plains, winter wheat (Triticum aestivum L.) typically is planted from late September through November. However, grain yield and grain quality often are reduced by variable weather conditions in the spring and foliar disease infections. Field studies were conducted in southeastern Kansas from 1990 through 1995 on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf) to evaluate effects of planting date, with and without a foliar fungicide (propiconazole: (1-{[2-(2,4-dichloro-phenly)-4-propyl-1,3-dioxolan-2-yl] methyl}-1H-1,2,4-triazole), on grain yield, yield components, and grain quality (test weight and protein) of hard and soft red winter wheats with different maturities and disease resistances. In 2 of 6 yr, grain yields of all cultivars planted in late September were reduced significantly by barley yellow dwarf virus (BYDV) infection. Intermediate planting dates in mid- to late October resulted in the best grain yield and quality in most years. Grain yields and test weights of November-planted wheats were more variable and depended on specific environmental conditions. Grain yield and test weight responses to foliar fungicide depended on severity of specific foliar diseases, cultivar disease resistance, and environmental conditions, but significant yield increase occurred 77% of the time. Planting date had no significant effect on foliar fungicide effectiveness. Foliar fungicide had no effect on grain protein, head density, or kernels per head. Results indicate that a foliar fungicide application could be beneficial in protecting grain yield and test weight potential of both hard and soft winter wheat cultivars when conditions are favorable for foliar disease epidemics in the eastern Great Plains wheat-growing region.

Effect of phosphorus fertilization and foliar application of chelated zinc and calcium on seed, protein and oil yields and oil properties of cotton

Abstract: Field experiments were conducted during two successive seasons in the Agricultural Research Center, Giza, Egypt (a clay loam soil), to study the effects of phosphorus fertilization (addition at rates of 44 and 74 kg of P 2 O 5 /ha) and foliar application of zinc (at 0.0 and 40 ppm of Zn applied twice, 75 and 90 days after planting) and calcium (at 0.0, 20, 40, and 60 ppm of Ca applied twice, 80 and 95 days after planting) on seed, protein and oil yields and oil properties of the Egyptian cotton cultivar Giza 75. Application of P at the high rate and spraying plants with zinc and calcium at any concentration increased cottonseed yield/ha, seed index, seed oil content, oil and protein yields/ha, seed oil unsaponifiable matter, and total unsaturated fatty acids (oleic and linoleic). Conversely, decreases in oil acid value, saponification value and total saturated fatty acids occurred. The seed protein and oil refractive index tended to increase when the high P rate and Zn were applied. Seed protein content tended to decrease slightly with Ca application. Regardless of the slight decrease in protein content as a result of Ca application, the yield of protein increased, due to the fact that there was an obvious increase in seed yield which counterbalanced the negative effect of the decrease in protein content. The highest Ca concentration (60 ppm) gave the highest values of cottonseed yield/ha, seed index, seed oil and protein yields/ha and oil unsaponifiable matter, followed by the concentration of 40 ppm. The concentration of 40 ppm gave the lowest total saturated fatty acids. The effect of Ca concentrations on oil refractive index was very limited.

Influence of nitrogen on competition between winter cereals and sterile oat

Abstract: Field experiments were carried out in northern Greece during 1994, 1995, and 1996 to study the effect of nitrogen fertilization on competition between sterile oat and wheat, barley, and triticale. Dry weight of all crops was not affected until early March by sterile oats (110 plants m−2), but wheat and triticale dry weight were significantly reduced by sterile oats competition after that time. Grain yield of both wheat and triticale was equally reduced by 61% due to the presence of sterile oats, whereas the reduction for barley grain yield was 9%. Nitrogen fertilization (150 kg N ha−1) slightly increased yield of all crops grown without weed competition compared to the control (0 kg N), whereas the same treatment increased sterile oats dry weight as well as its competitive ability against wheat and triticale. Split application of nitrogen (50 kg N ha−1 before planting and 100 kg N ha−1 in early March) caused a slightly higher increase in sterile oats dry weight compared to the control or one appl...

SIMPLE : A model for SIMulation of PLant Emergence predicting the effects of soil tillage and sowing operations

Abstract: A model predicting seedling emergence is described and applied to sugarbeet (Beta vulgaris L.). The input variables are the soil surface texture, soil temperature, rainfall, aggregate size distribution and position in the seedbed, sowing depths, characteristics of the seeds (initial seed mass distribution, germination time, and hypocotyl elongation distributions). A three-dimensional seedbed layer is created where the aggregates and seeds are placed. Soil water content is assumed not to limit sugarbeet emergence (sowing conditions in northern Europe). The time needed to reach the soil surface is calculated using germination thermal time, soil temperature, the presence or absence of aggregates, and the hypocotyl elongation function. The ability of seedlings to break through the soil surface is a function of crust development and moisture. The seedling growth after emergence is calculated with reference to seed mass distribution, emergence delay, and the presence or absence of mechanical obstacles. The emergence prediction was tested in field experiments with four seedbeds, from fine earth to cloddy structure, and a sowing depth of 17 to 35 mm. The predicted number and sizes of clods encountered by seedlings and the calculated hypocotyl length were not significantly different from measured ones. Predicted germination times were longer than the observed ones (differences <5°C d); final rates were well predicted. Predicted vs. measured final emergence rates differed by less than 10%; changes with time differed from 15 to 30°C. This was due to the hypocotyl elongation functions, which must be improved. Further improvements will be to predict soil water content variations and effects on emergence via water stress and soil strengthening.

Effects of water supply and sowing date on performance and essential oil production of anise (pimpinella anisum l.)

Abstract: Field and greenhouse experiments were carried out in order to determine the effects of water supply and sowing date on the performance and essential oil production of anise (Pimpinella anisum L.). The results indicated that mean leaf area (LA), specific leaf area (SLA), relative growth rate (RGR), relative water content (RWC), grain yield and essential oil decreased, while the root/shoot ratio and the oil percentage of the seeds increased when the available soil water decreased to below 80% in the greenhouse. It was concluded that for higher grain and essential oil production, anise must be sown early in the spring (April 4 to 16) in Tabriz. Water deficit during stem elongation and umbel appearance reduced anise growth, grain yield and oil production. Seeds harvested at the waxy stage had higher oil content than those harvested at earlier or later stages.

Pre-sowing treatments for improving emergence of bitter gourd seedlings under optimal and sub-optimal temperatures

Abstract: Bitter gourd (Momordica charantia L.) requires high temperature (between 25 and 28°C) for successful seedling emergence, and poor emergence is common at sub-optimal temperature. This study evaluated the effect of suboptimal temperature on seedling emergence and several physiological characteristics related to seedling growth in bitter gourd cultivar Special Six. Priming was achieved by mixing the seeds with moist No. 3 vermiculite, incubating at 25°C for 36 h, then air-drying to the original moisture level. Warm water soaking was achieved by soaking the seeds in water at 50°C for 60 min, and then air-drying to the original moisture level. Seedling emergence from vermiculite was determined at 25, 20 and 15°C. The emergence of non-treated seeds at 25°C was 50%. No seedlings emerged at 20 or 15°C. However, both priming and warm water soaking improved the emergence responses of bitter gourd seeds under 25 and 20°C. The observed decrease and delay in emergence at sub-optimal temperature were linked to the reduced activity of enzymes (i.e. isocitrate lyase, malate-synthase and malate dehydrogenase) involved in lipid and sucrose conversion. Both priming and warm water soaking improved the low temperature (20°C) seedling emergence. These improvement were attributed to the increased enzyme activities. Nevertheless, the morphological changes and softening in seed coat and seed treatment-stimulated embryo growth might also play crucial role in speeding up the seedling emergence.

The effects of seed treatments on germination and establishment of Kentucky bluegrass (Poa pratensis L.)

Abstract: Common Kentucky bluegrass seeds were subjected to four hydration treatments: hydropriming, accelerated germination, matric priming and osmotic priming. Seeds from each hydration treatment were subjected to the 15°C or 25°C germination assay either without drying or with drying for 1 week at 25°C. Hydropriming failed to improve germination. Accelerated germination greatly increased germination rate provided the seeds were not dried before sowing. Primed seeds germinated faster than non-treated seeds at either germination temperature, although germination percentage was not increased. Drying the primed seeds slowed germination and this was more pronounced in matrically than in osmotically primed seeds germinated at 15°C. From the subsequent greenhouse seedling emergence test, we conclude that matric priming, using water as the hydrating agent and without postpriming drying was the most satisfactory hydration treatment for KB. Compared to responses of non-treated seeds, this treatment resulted in 49% less time to 50% emergence, 13% greater emergence and 84% higher shoot dry weight.