Effect of nitrogen fertilizer application on growth, biomass production and N-uptake of torpedograss (Panicum repens L.)

A glasshouse study was conducted to evaluate the effects of different rates (0, 50, 100, 200 and 400 kg ha^?1) of nitrogen (N) fertilizer application on the growth, biomass production and N‐uptake efficiency of torpedograss. The growth responses of torpedograss to the N application were significant throughout the observation periods. Torpedograss grown for 60 days obtained the highest total biomass of 23.0 g plant^?1 with an application of 200 kg ha^?1 N, followed by 20.4 g plant^?1 with an application of 100 kg ha^?1 N; when it was grown for 90 days a significantly higher biomass of 102.3–106.0 g plant^?1 was obtained with the 200–400 kg ha^?1 N than the biomass (68.0 g plant^?1) obtained with the fertilizer applied at a lower rate. When the torpedograss was grown for 130 days the highest biomass was 230.0 g plant^?1 with the 400 kg ha^?1 N application, followed by a biomass of 150.0 g plant^?1 with the 200 kg ha^?1 N application, but the above‐ground shoot in all treatments was over mature for animal food. The ratio of the above‐ground shoot to the underground part increased with the increase in N application up to 400 kg ha^?1 during the 90 days after planting (DAP), but the above‐ground shoot biomass was the same with the 200 and 400 kg ha^?1 N. The agronomic efficiency of the N application decreased to 5–38 with the increase in N application to 400 kg ha^?1, which was less than half the agronomic efficiency with the 200 kg ha^?1 N. The agronomic efficiency of N was very low (5–22) during the 60 DAP, which indicated that the N application would not be economically viable in this period for torpedograss as a pasture, and short‐duration plants could be cultivated in torpedograss‐infested fields to minimize weed‐crop competition. The nitrogen concentration (%) in the torpedograss increased with the increase in N application, but N‐uptake efficiency was the opposite and the value was very low with the 400 kg ha^?1 N. The above results lead us to conclude that the N application rate of 200 kg ha^?1 is the most effective for torpedograss growth.     

Evaluation of Water and Nitrogen Use Efficiency,Digestibility and Some Quantitative and Qualitative Characteristics of Forage Beet Cultivars Under Different Irrigation Methods and Nitrogen Levels

The aim of this study was to evaluate the water and nitrogen use efficiency and some quantitative and qualitative characteristics of forage beet cultivars under the influence of different irrigation methods and nitrogen levels in two cropping years, 2017–18 and 2018–19, at Agricultural Research Station in Karaj, Iran. Experimental factors included the first factor with four irrigation methods (normal leakage, alternate furrow irrigation, fixed furrow irrigation, type (drip-strip)), the second factor was the amount of nitrogen fertilizer with three levels (150, 200 and 250?kg N ha^?1) and the third factor included three forage beet cultivars (Sbsi052, Jamon and Kyros). Among irrigation treatments, alternate furrow irrigation and fixed furrow irrigation had the highest sugar content with 9.28% and 9.17%, respectively. The highest yield of digestible organic matter was obtained in leakage irrigation treatment, nitrogen fertilizer of 250?kg ha^?1 and in Kyros at the rate of 19.45?t ha^?1. The highest yield of root digestible dry matter, potassium, sodium and free nitrogen was observed in leakage irrigation treatment and consumption of 200?kg ha^?1 nitrogen was observed in foreign cultivars. The highest crude protein was observed in alternate furrow irrigation conditions with a consumption of 200?kg ha^?1 nitrogen in cultivar Sbsi052 at 13.08%. Leakage irrigation and type tape had the highest consumption efficiency and efficiency of nitrogen uptake with application of 150 and 200?kg ha^?1 N, and the highest water use efficiency was also observed in leakage irrigation and type tape with application of 250?kg ha^?1 N in domestic and foreign cultivars. The type irrigation method showed better quantitative and qualitative yield than the furrow irrigation methods.

     

The effect of nitrogen fertilizers on the germination and seedling emergence of wild oat (A. fatua L.) seed in different soil types

Ammonium-containing fertilizers such as granular limestone ammonium nitrate (LAN) and liquid ammonium nitrate (AN) proved to be most effective in stimulating germination and emergence of wild oat in sandy and loamy soil. In pot experiments, rates as low as 25 kg N ha^?1, significantly increased seedling emergence of wild oat. In sandy soil percentage emergence increased with increasing levels of LAN-fertilizer up to 125 kg N ha^?1 which gave 76·1 % emergence after 60 days. In control pots where no nitrogen was applied, only 21·6% of seeds planted emerged after 60 days, In loamy soil, as for AN in both soil types, high levels of LAN initially delayed seedling emergence. This negative effect disappeared approximately 15 days after seeding, resulting in no significant difference in emergence of wild oat where 25 to 125 kg N ha^?1 was applied as LAN or AN. All these rates, however, increased seedling emergence between 25 and 35% compared to the no-nitrogen treatments. Since the same rate of ammonia gas is not equally effective in breaking dormancy of semi- and deeply dormant wild oat seed, results of these experiments are not necessarily applicable to wild oat seeds differing in dormancy status.     

Response of weeds to application of nitrogen, phosphorus and potassium on low-fertility acid soils in Suriname

The effect of nitrogen, phosphorus and potassium on the growth of weeds was studied at two locations on low-fertility acid soils in Suriname. Nitrogen stimulated the growth of weeds in terms of ground-cover and weight on a loamy sand of comparatively low fertility, as well as on a sandy loam of higher fertility. Phosphorus ultimately only stimulated ground-cover development and growth on the sandy loam, and interacted positively with nitrogen on that soil. Potassium had no effect on weed weight, but at both locations the number of plants increased with application of K. Differences in the amount of weed growth between the two locations were related to differences in the composition of the weed flora. On the sandy loam with application of 50 kg N, 50 kg P and 40 kg K ha^?1, nutrient uptake by the weeds was 72 kg N, 10 kg P and 121 kg K ha^? over a period of 35 days. Réponse des adventices à l'application d'azote, phosphore et potassium sur des sols pauvres acides au Surinam En deux lieux du Surinam avec des sols pauvres acides, l'effet de l'azote, du phosphore et du potassium sur la croissance des adventices a étéétudié. L'azote a stimulé la croissance des adventices en terme de couverture du sol et de poids sur un sable limoneux relativement pauvre aussi bien que sur un limon sableux de plus grande fertilité. Le phosphore a finalement seulement stimulé le développement et la croissance sur le limon sableux et il y a eu une interaction positive avec l'azote. Le potassium n'a pas eu d'effet sur le poids des adventices, mais dans les deux situations le nombre de plantes a augmenté avec l'application de K. Les différences dans la quantité de mauvaises herbes entre les deux situations étaient liées aux différences dans la composition de la flore adventice. Sur le limon sableux avec une application de 50 kg d'azote, 50 kg de phosphore et 40 kg de potasse à l'hectare, l'absorption par les adventices a été en 35 jours de 72 kg N, 10 kg P et 121 kg K à l'hectare. Wirkung einer Stickstoff-, Phosphor- und Kaliumdüngung auf die Verunkrautung ertragarmer, saurer Böden in Surinam An 2 Orten mit ertragarmen, sauren Böden in Surinam wurde die Wirkung einer Stickstoff-, Phosphor- und Kaliumdüngung auf das Wachstum von Unkräutern untersucht. Stickstoff förderte das Wachstum von Unkräutern (Bodendeckung, Biomasse) sowohl auf einem verhältnismäßig ertragarmen lehmigen Sand als auch auf einem ertragreicheren sandigen Lehm. Phosphor förderte letzten Endes Deckungsgrad und Wachstum nur auf dem sandigen Lehm und wirkte da positiv mit Stickstoff zusammen. Kalium hatte keine Wirkung auf die Biomasse, aber an beiden Orten führte es zu einer größeren Pflanzendichte. Die Wachstumsunterschiede an den beiden Orten hingen von der Zusammensetzung der Unkrautflora ab. Auf dem sandigen Lehm betrug bei 50 kg N, 50 kg P und 40 kg K ha^?1 die Nährstoffaufnahme der Unkräuter 72 kg N, 10 kg P und 121 kg K ha^?1 innerhalb 35 Tagen.     

Impact of Irrigation Timing and Weed Management Practices on Chlorophyll Content and Morphological Traits of Tomato (Solanum lycopersicum Mill.)

Weeds are a major biotic constraint; compete with crop for the same resources and ultimately reduce productivity. This study evaluated the impact of irrigation intervals and weed management treatments on chlorophyll content and morphological growth of tomato to find an appropriate integrated weed management strategy. Two-year field experiments (2018/2019) were conducted at district Mardan (34°15′38″ N and 72°6′36″ E). Tomato F1 hybrid (Taj?3592) was transplanted during March. The experiments were laid out in a randomized complete-block design in split-plot arrangement with three replications. The main block comprised three irrigation intervals (3, 6, and 9 days) and the sub-block included weed management treatments: transparent polythene, black polythene, weeding except Orobanche, sole weeding of Orobanche, weeding of all weeds, copper oxychloride 1.5?kg a.i ha^?1 (single dose), copper oxychloride 1.5?kg a.i ha^?1 (split doses), copper oxychloride?+?humic acid 25?kg ha^?1 (single dose), copper oxychloride?+?humic acid 25?kg ha^?1 (split doses), copper sulphate 2?kg ha^?1 (single dose), copper sulphate 2?kg ha^?1 (split doses), ammonium sulphate 200?kg ha^?1 (single dose), ammonium sulphate 200?kg ha^?1 (split doses), pendimethalin 33 EC 1.44?kg a.i ha^?1, glyphosate 48 SL 1.5?kg a.i ha^?1, and weedy check. Lowest relative weed density (RWD) of O. cernua (2.23%) and highest RWD of O. cernua (38.01%) were recorded in the 3? and 9?day irrigation intervals, respectively. However, 3?day irrigation interval resulted in highest fresh weed biomass (5794?kg ha^?1). Moreover, the 6?day irrigation interval significantly increased chlorophyll content by 11 and 5%, leaf area by 23 and 6%, and number of branches plant^?1 by 30 and 22% compared to 9? and 3?day irrigation intervals, respectively. Among the weed management treatments, black polythene resulted in the highest weed control efficiency (96%), increasing chlorophyll content by 16%, leaf area by 33%, and number of branches plant^?1 by 64% vs. weedy check. Consequently, 6?day irrigation intervals?×?black polythene could be the best weed management strategy, followed by transparent polythene, weeding of all weeds, pendimethalin, glyphosate, and ammonium sulphate.

     

Residues in blackcurrants,fodder peas,spinach and potatoes treated with sublethal doses of 2,4,5-T to simulate wind drift damage

Blackcurrants, treated with 0.1 kg of 2,4,5-T ha^?1 (as esters of mixed C₄–C₆ alcohols; ‘Tormona 80’), contained 0.1 mg of 2,4,5-T residues kg^?1 in the berries at ripeness 29 days after treatment. Total residues in the berries were not reduced during growth and ripening, although the residue concentrations declined in the same period due to growth dilution. In spinach leaves from old plants, treated with 0.1 kg ha^?1, 0.05 mg of 2,4,5-T kg^?1 was found 14 days after treatment. Fodder peas showed no residues (< 0.002 mg kg^?1) at harvest 62 days after treatment with 2,4,5-T esters. After application of 0.1 kg ha^?1 on potato plants, the disappearance of 2,4,5-T was rapid during the first month, but residues were translocated into the tubers and reached a constant level of 0.02 mg kg^?1 after 1 month until harvest at 108 days after treatment. In all crops, visible effects were observed after treatment with 0.1 kg ha^?1. After the application at 0.01 kg ha^?1, phytotoxic effects were observed only in blackcurrants, but negligible residues were found in all the test crops.     

Nitrogen fertilization and yield losses of tea to red crevice mite (Brevipalpus phoenicis geijskes) in the Eastern Highlands of Kenya

A field trial using a mite-susceptible clone 11/4 of tea whose yield potential is over 3 t ha^-1 year^-1 was conducted to determine how yield losses due to infestation by red crevice mite (Brevipalpus phoenicis Geijskes) relate to nitrogen nutrition. This was done over a 3 year period in plots either receiving 0, 100, or 200 kg N ha^-1 year^-1. For determining the losses due to mites, an acaricide check method of yield loss assessment was used. Mites were controlled in the plots by spraying flucythrinate. The yield varied considerably between seasons with mean yields in the 3 year period ranging from 2.0 to 2.4 t ha ^-1 without fertilizer and 2.4 to 2.6 t ha^-1 year^-1 at 100 kg N and 2.5 to 2.7 t ha^-1 year^-1 at 200 kg N. Application of the acaricide decreased the mite population by 60-74%. Yield loss between sprayed and unsprayed treatments was 12-22% without fertilizer but this was reduced to 5-6% when fertilizer was supplied at 100-200 kg N ha^-1. The reduction in yield losses in fertilized plots indicate the beneficial effects of nitrogen in inducing tolerance to mites and possibly increasing plant vigour. Protecting the tea from mite attack resulted in yield advantage and a net benefit of $US 0.3, 0.2 and 0.2 per kg made tea at 0, 100 and 200 kg N ha^-1 respectively. Application of 100 kg N ha^-1 had higher net cost benefit than the 200 kg N application rate. The strategy for control of mites would be to integrate spraying with use of fertilizer.     

Effect of Phosphorus and Arbuscular Mycorrhizal Fungi (AMF) Inoculation on Growth and Productivity of Maize (Zea mays L.) in a Tropical Ferralsol

Soil fertility in the Lubumbashi region often proves to be limiting factor for crop production due to their low nutrient reserves. The objective of this work was to evaluate the impact of arbuscular mycorrhizae on phosphorus uptake by maize on Ferralsol. The trial was conducted in pots with 30?kg or 60?kg of P₂O₅ ha^?1 and a control. These three levels of phosphorus were combined or not with arbuscular mycorrhizae. The combinations of 30?kg or 60?kg of phosphorus with the inoculum led to a male flowering of maize at 63 days after semi. Maize treated with 60?kg of phosphorus ha^?1 formed very few or almost no blisters in the roots. Cob weight, length, diameter, number of rows and kernel weight varied significantly with phosphorus on both inoculated and uninoculated pots. The inoculated plants had high averages for these yield parameters. Due to the lack of phosphate fertilizer, inoculum alone can be an alternative to phosphorus provided that nitrogen and potassium are added, resulting in small but seed-filled ears compared to the phosphorus-free control without mycorrhizae, which resulted in empty ears. Yield varied significantly with the addition of phosphorus (0.3 to 6.1 tons ha^?1) and less significantly with inoculum (3 to 3.7?t ha^?1). The combination of treatments showed a significant difference in favour of the 60?kg of phosphorus or 60?kg of phosphorus associated with the inoculum. The highest phosphorus content was obtained on the inoculum treatment alone, which provided 1.4?mg phosphorus?g^?1 maize compared to other treatments, which provided 0.69 to 0.71?mg phosphorus?g^?1 maize.

     

Growth, Yield and Blossom-End Rot Incidence in Bell Pepper as Affected by Phosphorus Level and Amino Acid Applications

This study was conducted to examine the possibility of enhancing productivity and reducing blossom-end rot (BER) incidence in bell pepper (Capsicum annumn L.). Four rates of phosphorus application (30, 60, 90 and 120?kg?ha^{? 1} of P₂O₅) were combined with two commercial naturally occurring amino acid stimulants (Amino green and Aminofort). Water was used as a control treatment as well. Plants were sprayed with 500?ppm of solutions three weeks after transplanting. Increasing P application rate increased vegetative growth, fruit yield, fruit quality (fruit size, TSS, acidity and vitamin C.) and nutritional elements content (N, P, K and Ca). However, it was showed that the phosphorus level of 90?kg?ha^{? 1} had no significant differences to the level of 120?kg?ha^{? 1} for most parameters measured. Furthermore, P-applications had a remarkable effect on reducing blossom end rot, probably due to a positive effect on water uptake and Ca acquisition. In addition, positive effects on the vegetative growth parameters, individual fruit weight and number of fruits were showed concerning the amino acid used. Fruit quality in terms of total soluble solids (TSS), total acidity and ascorbic acid contents were also improved compared to control. Aminofort was superior in its effect as Amino green. However, the tested amino acids showed no effect on BER incidence.     

Nutrient uptake and yield of tomato under various methods of fertilizer application and levels of fertigation in arid lands

With rising concern about current irrigation and fertilizer NPK management, the present study was conducted to evaluate the effect of sources and methods of fertilizer application on nutrient distribution, uptake, recovery and fruit yield of tomato grown in a sandy soil. Equal amounts of NPK were applied in solid form or through fertigation at levels of 0%, 50%, 75% and 100% with the remainder 100%, 50% and 25% applied as solid fertilizers to the soil. Available NO₃ ^?-N and K were confined to the root zone of tomato in 75% and 100% NPK fertigation levels, while they moved beyond the root zone when they applied in two equal splits as solid fertilizers with drip (0% fertigation) and furrow irrigation. The mobility of P was greater in the root zone following its application through fertigation compared to a solid application as super phosphate. Drip irrigation showed significantly higher absolute growth rate (AGR), total dry weight (TDW) and leaf area index (LAI) of tomato over furrow irrigation. Moreover, tomato plants were able to utilize applied nutrients more efficiently in fertigation system than with conventional solid fertilizer application. Highest AGR, TDW and LAI were recorded when nutrients were applied to 100% by drip fertigation. The fruit yield of tomato was higher with drip irrigation (58.62 t ha^?1) than with furrow irrigation, (47.37 t ha^?1). Maximum fruit yield was recorded with 100% NPK fertigation (74.87 t ha^?1) and was associated with a higher number of fruits per plant and a bigger fruit size than the solid applied fertilizers under both drip and furrow irrigation. On average, tomato accumulated more NPK across the fertigation levels than with drip and furrow irrigation. Similarly, the more controlled application of nutrients in fertigation treatments improved NPK recovery and fertilizer use efficiency (FUE) and resulted in lesser leaching of NO₃ ^?-N and K to deeper soil layers.     

Residues of aldicarb and its main metabolites in the leaves of sugar beet plants

The residues of aldicarb and of its main metabolites (aldoxycarb, 2-mesyl-2-methylpropionitrile, and 2-mesyl-2-methylpropan-1-ol) were measured, by a gas-liquid chromatographic procedure, in the leaves of ripe sugar beet plants from cultures made by several farmers. The sugar beet plants had been grown in normal fields and treated at sowing with aldicarb at the usual rate of 1 kg ha^?1 in the form of ‘Temik’, the commercial formulation of aldicarb which contains 10% by weight of aldicarb. The samples of sugar beet plants were taken from three fields of different soil types. The residue concentrations, ranged in order of soil type, were: sandy loam > silt loam > clay.     

Abscisic acid as a protectant of Avena fatua L. against diclofop-methyl activity

The imposition of water stress before or al the time of spraying diclofop-methyl reduced efficacy against wild oat (Avena fatua L.). Similar reductions in herbicide performance were obtained by application of 20 μg of the methyl ester of abscisic acid (ABA) to plants with three to four leaves before spraying with I kg ha^?1 diclofop-methyl. Application of 40–100 μg ABA per plant effectively protected plants against damage from diclofop-methyl applied at 1 5–2 0 kg ha ^?1. The application of 20 μg ABA induced rapid stomatal closure and a reduction in leaf extension rate, which were sustained for 7–8 days after treatment. These changes were associated with an overall reduction in shoot growth. ABA-treated plants that were additionally sprayed with diclofop-methyl sustained ABA symptoms, but no additional weight loss or leaf chlorosis. The mechanism of the protective action of ABA on diclofop-methyl has not been determined.     

Paraquat, diesel oil and kerosene for ratoon clearing of pineapple

Three chemical methods of clearing pineapple ratoons were compared with the traditional method of cutting and burning after the plants have dried. The best chemical treatment was paraquat at 0.84 kg ha^?1 which gave full scorching at leaves on 92% of plants so that they could be easily burnt 3 weeks after treatment. Plants sprayed with diesel oil or kerosene at 570 1 ha^?1 could be satisfactorily burnt after 9 weeks compared with 12 weeks required for satisfactory burning with the traditional method.     

Production,size, and germination of broad‐leaved dock seeds collected from mother plants grown under different nitrogen,phosphorus, and potassium supplies

Rumex obtusifolius is believed to be a nitrophilous weedy species that spreads mainly by seed. However, the effects of nutrient availability on seed production never have been investigated. In this study, how the amount of seed production per plant, the chemical composition of the seeds, and their size and germination are affected by the supply of N, P, and K was investigated. A pot fertilizer experiment with 10 treatments (combinations of 0, 150 [N1], and 300 [N2] kg N ha^?1, 0, 40 [P1], and 80 [P2] kg P ha^?1, and 0 and 100 [K] kg K ha^?1 applied twice per vegetation season) was carried out in Prague, Czech Republic, in 2008 and 2009. The seeds from plants that were cultivated since the spring were collected each August. The germination of the seeds was determined in long‐daylight conditions at a stable temperature of 20°C. The number of seeds per plant ranged from 0 in the P1 and P2 treatments and <200 in the control and K treatments to almost 9000 in the N2P2K treatment. The number of seeds per plant was positively correlated with the number of stems per plant and the number of seeds per stem. The relationship between the amount of seeds per plant and the individual seed weight was positive. The concentration of N, P, and K in the seeds was affected by the treatments. The weight of 1000 seeds ranged from 1.3 to 1.7 g. The seed length ranged from 2.11 to 2.34 mm and the seed width varied from 1.26 to 1.42 mm. With the exception of the control (with 94% germination), the amount of seed germination was >98% in all the other treatments in 2008. In 2009, the amount of seed germination was >95% in all the treatments, except N1 and N2, where 93% and 89% germination, respectively, was recorded. The germination rate was positively related to the P concentration in the seeds. The amount of time that was necessary for 50% seed germination ranged from 1.53 to 2.89 days and was not related to the N concentration in the seeds, but it was negatively related to the P and K concentrations. A balanced N, P, and K supply to the mother plant strongly affected the number of produced seeds and their chemical composition and germination ability.     

The HPLC determination of residues of maleic hydrazide in cloves of garlic bulbs following foliar application

A method was developed for the extraction and HPLC analysis of the plant growth regulator maleic hydrazide (MH) from garlic bulbs. Recovery of MH from fortified garlic tissue was 75.8(±6.1)% at the 1 and 2 mg kg^?1 fortification levels. MH residues were determined by HPLC in cloves of garlic bulbs following treatment at three sites in southern Ontario with foliar applications at 3.75 kg ha^?1. MH residues in the cloves were in the order of 3 mg kg^?1 at two sites, and 11 mg kg^?1 at the third side.     

Effects of tillage on winter wheat production in Mediterranean dryland fields

The benefits of conservation agriculture (CA) and associated technologies are not equal for all agro ecosystems. This study used a field experiment to examine winter-wheat yield and weeds under conservational and conventional systems in the central region of Spain. The three tillage treatments were conventional tillage (CT), minimum tillage (MT) and no-tillage (NT). The climatic conditions influenced wheat yield, yield components, soil water content and weeds. When the autumn-winter rainfall was abundant and constant (69.7% of annual rainfall), wheat grain yield (4465?kg?ha^?1) and yield components (3897?kg?ha^?1 of straw biomass and 584.5 ear m^?2) were highest. Wheat grain yield was highest with NT: 3549.9?kg?ha^?1 (compared to MT: 2955.1?kg?ha^?1 and CT: 2950.3?kg?ha^?1) and ear number per m² was significantly lower with MT (332 no ear m^?2, compared to 426 and 411.6?ear?m^?2 in CT and NT-systems respectively). Soil water content, at earing stage, was the highest in NT (27.36% of soil moisture) while MT showed the lowest content (11.83% of soil moisture). The higher weed measurements (means of 2.557 plants m^?2; 1.443 species m^?2 and 2.536 g m^?2) was with higher annual rainfall (488?mm). Throughout the experiment it was the dominant presence, in MT-wheat plots, of Lolium rigidum Gaudin (with means from 4.87 to 7.71 plants m^?2), which reduced the ear number per m². Our study revealed that in the short term, under semi-arid conditions, only the adoption of NT system (rather than MT) showed economic benefits.     

Common ragweed (Ambrosia artemisiifolia) dry matter allocation and partitioning under different nitrogen and density levels

Dry matter partitioning and allocation is a major determinant of plant growth and its competitiveness. Common ragweed (Ambrosia artemisiifolia) is a troublesome agronomic weed species and it is also a major health concern in Europe and many other countries because of its rapid spreading and production of allergenic pollen. A field experiment was conducted in 2009 to determine the effect of nitrogen fertilizer levels (0, 100, and 200 kg ha^?1) and plant density levels (1.3, 6.6, and 13.2 plants per m²) on the leaf, stem dry matter partitioning, and dry matter allocation of ragweed. With an increasing density, the stem partitioning coefficient increased, whereas the leaf partitioning coefficient decreased. The addition of nitrogen had a limited effect on the leaf and stem dry matter partitioning. The root dry matter production decreased with an increasing density and was not influenced by the addition of nitrogen. Under intraspecific competition, ragweed exhibited a stronger above‐ground competition intensity than below the ground, which resulted in a greater root : shoot ratio, compared to the low‐density stands. The level of nitrogen influenced the vertical leaf, stem, and total dry matter distribution, with a greater allocation to the top stratum of the plants, thus increasing their competition for light. The biomass allocation of ragweed to the roots in response to the nitrogen supply exhibited a low plasticity, compared to the shoots, which displayed a high plasticity. The results of this study suggested that, under intraspecific conditions and with an increasing nitrogen supply, ragweed would be more competitive in above‐ground resource acquisition.     

Growth response of six weed species and spring barley (Hordeum vulgare) to increasing levels of nitrogen and phosphorus

A glasshouse experiment was carried out to investigate the influence of increasing levels of nitrogen and phosphorus on the growth of six common weed species growing alone or in competition with spring barley (Hordeum vulgare). Capsella bursa‐pastoris, Chenopodium album, Papaver rhoeas, Sinapis arvensis, Spergula arvensis, Viola arvensis and spring barley were grown in pots with different levels of nitrogen (0, 30, 60, 90, 120 and 150 kg N ha^?1) or phosphorus (0, 10, 20, 30, 40 and 60 kg P ha^?1). The aboveground parts of the plants were harvested after 7 weeks and the dry weight of shoots, percentage N and P content of the shoot and uptake of N and P were determined. A linear or a polynomial model was used to describe the data. Growing alone, Spergula arvensis was the only weed species that increased its dry weight at the same rate as barley. Weed species with low dry weight increase had larger increases in percentage N or P content than barley, indicating a luxury accumulation of nutrients. The uptake of N and P per pot did not differ much between weeds and barley. V. arvensis and P. rhoeas accumulated least nutrients (per cent of dry matter) and Spergula arvensis accumulated most. Weeds grew poorly in competition with barley. The percentage N and P content in barley did not change when they grew in competition with weeds.     

Effects of fluazifop-butyl on shoot growth and rhizome buds of Elymus repens (L.) Gould

A series of glasshouse experiments was conducted to evaluate the activity of fluazifop-butyl, butyl 2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy] propionate, against Elymus repens. Foliar applications of doses 0·25–1·0 kg ha^?1 consistently gave better control than did soil applications. The most obvious phytotoxic symptoms were chlorosis and necrosis, beginning with the youngest leaves 5–6 days after spraying, which spread to all leaves within 2 weeks. Translocation was measured by defoliating plants at different times after spraying and assessing regrowth and by evaluating rhizome-bud viability. At low doses (0·125 and 0·25 kg ha^?1) translocation to rhizomes occurred mainly between 6 and 48 h. When fluazifop-butyl was sprayed at a dose range of 0·125–1·0 kg ha^?1, at least 90% of the rhizome buds had accumulated a lethal dose within 72 h of spraying. In another experiment, with a dose of 0·25 kg ha^?1, 31, 72 and 92% of rhizome buds were found to be non-viable when sampled 2, 24 and 48 h respectively after spraying. At 1·0 kg ha^?1 all the buds had accumulated sufficient herbicide to prevent sprouting 48 h after spraying.