Shoot Nitrogen Content Research Articles

Quality of Enterolobium contortisiliquum (Vell.) Morong. seedlings in function of inoculation and natural nodulation in soils from southwest of Piauí, Brazil

Biological nitrogen fixation is an important alternative to provide nitrogen (N) to legumes. This study aimed to evaluate the quality of Enterolobium contortisiliquum (Vell.) Morong seedlings depending on the inoculation and natural nodulation in soils from southwest of Piaui, Brazil. The experimental design was completely randomized with five replications and treatments arranged in a (5 x 4) factorial design, consisting of five soil classes and four N treatments (a-inoculation with strain BR 4406, b- with application of mineral N, c- with mineral N and inoculation with BR 4406, d- without mineral N or inoculation). Seventy five days after sowing number and fresh weight of nodules, N2 fixation efficiency, nitrogen concentration in shoot and morphological parameters of seedlings were evaluated. The seedlings of E. contortisiliquum presented natural nodulation only when grown on Organosol and Fluvic Neossol. The inoculant strain BR 4406 showed a very low adaptation to the soils from Southwest of Piaui. Seedlings grown in Quartzarenic Neosol, Organosol and Fluvic Neossol have better quality compared to those grown in Oxisol and Litolic Neosol.

Simulation of Biomass and Nitrogen Dynamics in Perennial Organs and Shoots of Miscanthus × Giganteus Using the STICS Model

Biomass production by perennial plants promises to increase land use efficiency and reduce greenhouse gas emissions from cropping systems dedicated to bioenergy production. The modelling of both biomass production and the environmental impacts of these systems over the long term is needed in order to evaluate their sustainability. New equations have been added to the STICS soil-crop-atmosphere model to provide a better description of perennial organs and their relationship with non-perennial ones, corresponding to the rhizomes and shoots, respectively in the Miscanthus × giganteus case study. Their description is intended to be generic for perennial plants, supported by the functional approach of STICS. The new version of STICS 8 was calibrated using published data and then validated against independent data. It was able to simulate the biomass and nitrogen content of the shoots (with a model efficiency of 0.95 and 0.70, respectively) and reproduce the dynamic of biomass and nitrogen in perennial organs (with a model efficiency of 0.41 and 0.63, respectively). Some of the model’s improvements are discussed. Modifications to the model allowed simulations of the effect of cultural practices, such as nitrogen fertilisation or harvest date, on the biomass and nitrogen content of rhizomes and shoots.

Nitrogen budget in a soil-plant system after brachiaria grass desiccation

Brachiaria spp. have been grown in a variety of cropping systems and are often terminated with herbicides, which may cause nitrogen (N) loss from the soil-plant system. In this study ammonia (NH3-N) loss by shoots and N balance in a soil-plant system were determined after desiccation of palisade grass (Brachiaria brizantha (Hochst. ex A. Rich) Stapf, cv. Marandu), signalgrass (Brachiaria decumbens Stapf), humidicola (Brachiaria humidicola (Rendle) Schweick) and Congo grass (Brachiaria ruziziensis Germain et Evrard). The grasses were grown in pots filled with an Oxisol in a greenhouse. Sixty days after planting, the plants were desiccated with glyphosate. Analyses were performed on plant and soil at desiccation and then at 7, 14, 21 and 28 days after desiccation in order to assess NH3-N losses by shoots and to estimate the N balance in the system. Total nitrogen (Total-N) concentration in shoots and roots of brachiarias decreased after desiccation, thereby reducing the amount of N in plants of the four brachiaria species. However, as most of the N lost by plants was released into the soil, N losses from the soil-plant system were small compared with the total N in the system: 1.2, 0.5, 0.4 and 1.4% for palisade grass, signalgrass, humidicola and Congo grass, respectively. N losses as NH3 from the soil-plant system after desiccation with glyphosate varied among brachiaria species, ranging from 0.8 to 2.0 g m−2 kg−1, and accounted for 30–80% of total loss.

Yeast as a Biofertilizer Alters Plant Growth and Morphology

ABSTRACTIt has been previously demonstrated that dicotyledonous plants perform rhizophagy, a process in which live microbial cells are engulfed by root cells and digested to acquire the nutrients from the microbes. Here we tested the hypothesis that rhizophagy is a mechanism of nutrient acquisition that is not restricted to dicotyledonous plants. We report that the monocotyledonous species sugarcane (Saccharum officinarum x spontaneum), grown in controlled axenic conditions, incorporated yeast cells into root cells. This suggests that rhizophagy is an evolutionarily conserved trait that predates the divergence of dicot and monocot species. To explore the potential relevance and practical application of rhizophagy, we investigated brewers’ yeast (Saccharomyces cerevisiae), a waste product of the brewing industry, for its role as biofertilizer. The addition of live or dead yeast to fertilized soil substantially increased the nitrogen (N) and phosphorus (P) content of roots and shoots of tomato (Solanum lycopersicum) and young sugarcane plants. Yeast addition to soil also increased the root‐to‐shoot ratio in both species and induced species‐specific morphological changes that included increased tillering in sugarcane and greater shoot biomass in tomato plants. These findings support the notion that brewers’ yeast is a cost‐effective biofertilizer that improves not only plant nutrition but also plant vigor during the early growth phase. It remains to be established which yeast‐derived substances trigger the observed plant growth effects, and how rhizophagy contributes to plant nutrient acquisition.

Reduced tillage in temperate organic farming: Effects on soil nutrients, nutrient content and yield of barley, rye and associated weeds

AbstractIn temperate regions, reduced tillage is still not broadly accepted in organic farming although the guidelines often recommend the reduction of tillage intensity. During the years 5–7 of a long-term experiment, we studied the effects of the three tillage systems moldboard plowing (MP, soil inversion to 30 cm depth), two-layer plowing (TP, inversion to 15 cm, loosening to 30 cm) and layer cultivation (LC, loosening to 30 cm) on soil nutrients, nutrient content of barley, rye and associated weeds, and yield on a clay loam soil. Crops were cultivated within a five-course crop rotation consisting of green fallow, winter wheat, field peas, winter rye and spring barley; no additional fertilizers were applied. Tillage affected only soil nitrate under barley, which decreased with decreasing tillage intensity. Soil humus, phosphorus (P) and potassium (K) were unaffected by tillage under both crops. Barley shoot nitrogen content was significantly influenced by tillage, with, across years, 38 and 83% higher values under MP than under TP or LC, respectively. Weeds in barley had a higher P and K content at LC than at MP or TP. This resulted, across years, in 73% higher barley yields in MP than in LC. The TP showed a 29% higher barley yield than the LC. Tillage methods had no effect on rye nutrient contents, rye yields or on weeds associated with rye. The significant interaction between tillage and year for rye yield suggests that weather conditions in a given year (e.g., amount of rainfall) can considerably alter the effect of reduced tillage.

Azospirillum Inoculation Alters Nitrate Reductase Activity and Nitrogen Uptake in Wheat Plant under Water Deficit Conditions

Water deficit stress usually diminishes nitrogen uptake by plants. There are evidences that some nitrogen fixing bacteria can alleviate this stress by supplying nitrogen and improving its metabolism in plants. Four Azospirillum strains, A. lipoferum AC45-II, A. brasilense AC46-I, A. irakense AC49-VII and A. irakense AC51-VI were tested for nitrate reductase activity (NRA). In a pot culture experiment using a sandy loam soil, wheat plants ( Triticum aestivum L. cv. Sardari) were inoculated with these bacterial strains and three ranges of soil water potential (W1: -10 to -20, W2: -40 to -50 and W3: -65 to -75 kPa) were applied to the pots. All strains were positive in NRA test and the highest (7.63mg NO 2 -N.L -1 .48h -1 ) was recorded for AC49-VII and the least (0.23mg NO 2 -N.L -1 .48h -1 ) was belong to AC51-VI. Leaf and root NRA, root and shoot nitrogen concentrations, and dry weights of root and shoot decreased by increasing water deficit stress. All four bacterial strains caused a significant enhancement in root NRA and in each water deficit level, the higher root NRA was recorded in AC46-I and AC49-VII inoculated plants. The highest leaf NRA was achieved by AC49-VII. The mean increment of root NRA by bacterial strains was 171% compared to the non-bacterial plants. Moreover, at the highest level of water deficit stress, the highest dry weight and nitrogen concentration in root and shoot were obtained by AC46-I and AC49-VII treatments.

Importance of different components of green roof substrate on plant growth and physiological performance

Green roof substrate is arguably the most important element of a green roof, providing water, nutrients and physical support to plants. Despite this there has been a lack of research into the role that different substrate components have on green roof plant growth and physiological performance.To address this, we assessed the importance of three green roof substrate components (organic matter type, brick particle size and water absorbent additive) for plant growth and plant physiological performance. Lolium perenne (Ryegrass) was grown in eight substrates in a controlled greenhouse environment with a factorial design in composition of (i) small or large brick, (ii) conifer bark or green waste compost organic matter, and (iii) presence/absence of polyacrylamide water absorbent gel (‘SwellGel™’).We found that large brick substrates had a lower water holding capacity than small brick (−35%), which led to decreased shoot growth (−17%) and increased root:shoot ratio (+16%). Green waste compost increased shoot and root growth (+32% and +13%) shoot nitrogen concentration and chlorophyll content (20% and 57%), and decreased root:shoot ratio (−15%) compared to bark. The addition of swell gel increased substrate water holding capacity (+24%), which increased shoot growth (+8%). Total evapotranspiration (a proxy for potential cooling) was increased by greater shoot biomass and substrate water holding capacity. Overall, this study provides one of the first quantitative assessments of the relative importance of commonly used green roof substrate components. It is clear that substrate composition should be considered carefully when designing green roofs, and substrate composition can be tailored for green roof service provision.

Patterns of night-time water use are interrelated with leaf nitrogen concentration in shoots of 16 deciduous woody species

Although the impact of nitrogen availability on the night-time water relations of plants has received a lot of attention during the last decade, knowledge of how these two traits are interrelated is contradictory and still limited. The aim of the current study was to investigate the impact of leaf nitrogen concentration on night-time (Enap) and daytime (Ed) transpiration rate, nightly water-use percentage of daytime water use (NWU), and increase in night-time transpiration rate (INT) in artificial predawn hours in the cut shoots of 16 woody species measured in the controlled conditions of a growth chamber. Two distinct patterns of night-time water use associated with leaf nitrogen concentration ([N]) were observed: shoots with high NWU were characterised by significantly (P<0.05) lower [N], whereas shoots with highest INT had greater [N]. The forward stepwise regression analysis revealed that variability in Ed, NWU and INT depended on [N], whereas the impact of other predictor variables (leaf phosphorus concentration, habitat soil water content and light availability) was insignificant (P>0.05). Our results suggest that high NWU could potentially compensate limited nitrogen uptake in species able to grow in nutrient-poor habitats. Furthermore, night-time stomatal regulation mechanisms may differ between species according to their [N] and this may explain the contradictory results between previous studies.

Isolation and characterization of nitrogen deficit Rhizobium isolates and their effect on growth of haricot bean

Nitrogen deficiency in recognized as the limiting factor for reduction in the yield of haricot bean in Ethiopia. The nitrogen fixing bacteria have the ability to enhance the plant growth and yield by fixing the atmospheric nitrogen and also play a significant role to conquer this problem. The aim of study was to isolate and characterize the haricot bean nodulating Rhizobium isolates and also to evaluate their effect on the growth of haricot bean. Out of total, twelve isolates were selected as representative samples and were screened for morphological, physiological and biochemical characteristics. On the basis of screening, eight potential isolates (MJUML1, MJUML3, MJUML4, MJUML6, MJUML8, MJUML10, MJUML11 and MJUML12) were selected for the further greenhouse experiment. The result indicated that inoculation of plants with Rhizobium isolates have significant effect on shoot dry weight, shoot nitrogen contents, nodule numbers, and nodule dry weight per root system (p < 0.05). Among all the tested Rhizobium isolates, MJUML11, MJUML12 and MJUML1 were best isolates and significantly increased the growth of haricot bean in nitrogen deficit soils and also survive in the soil as saprophytes. Key words: Biological nitrogen fixation, Nitrogen content, N-deficit soil, Phaseoulus vulgaris.

The allocation of assimilated carbon to shoot growth: in situ assessment in natural grasslands reveals nitrogen effects and interspecific differences

In grasslands, sustained nitrogen loading would increase the proportion of assimilated carbon allocated to shoot growth (A shoot), because it would decrease allocation to roots and also encourage the contribution of species with inherently high A shoot. However, in situ measurements of carbon allocation are scarce. Therefore, it is unclear to what extent species that coexist in grasslands actually differ in their allocation strategy or in their response to nitrogen. We used a mobile facility to perform steady-state (13)C-labeling of field stands to quantify, in winter and autumn, the daily relative photosynthesis rate (RPR~tracer assimilated over one light-period) and A shoot (~tracer remaining in shoots after a 100 degree days chase period) in four individual species with contrasting morpho-physiological characteristics coexisting in a temperate grassland of Argentina, either fertilized or not with nitrogen, and either cut intermittently or grazed continuously. Plasticity in response to nitrogen was substantial in most species, as indicated by positive correlations between A shoot and shoot nitrogen concentration. There was a notable interspecific difference: productive species with higher RPR, enhanced by fertilization and characterized by faster leaf turnover rate, allocated ~20% less of the assimilated carbon to shoot growth than species of lower productivity (and quality) characterized by longer leaf life spans and phyllochrons. These results imply that, opposite to the expected response, sustained nitrogen loading would change little the A shoot of grassland communities if increases at the species-level are offset by decreases associated with replacement of 'low RPR-high A shoot' species by 'high RPR-low A shoot' species.

Determination of genetic diversity in onion (Allium cepa L.) by multivariate analysis under long day conditions

A pot culture experiment was conducted at Indian Institute of Soil Science to compare the nutrient uptake pattern of rainy season crops such as maize, soybean, sorghum, pearl millet, finger millet and rice. Crop biomass was taken at 30, 50, 75 and 90 days after sowing (DAS) and at maturity from each crop. Among the crops grown, total dry biomass was decreasing in the following order; maize > pearl millet > sorghum > soybean> rice > finger millet. With respect to nutrient uptake, soybean crop showed highest nitrogen (N) content in shoot (1.73%), followed by maize (1.12%), pearl millet (1.10%), finger millet and rice (0.79%) and sorghum (0.78%), whereas, maximum phosphorus (P) concentration was in maize followed by pearl millet and sorghum. Micronutrient concentration was more in shoot as compared to roots in all crops except soybean. This study might be useful in the bio-fortification process for fodder purpose. Higher biomass producing maize crop with higher nutrient uptake capacity can be used for agronomic biofortification. It will help for reducing nutritional deficiency in animals. Key words: Biomass, nutrient uptake, soil fertility.

Deposição de sílica e teor de nitrogênio e silício em arroz

The nitrogen fertilization is an important practice to reach high productivity, however, nitrogen high level can cause lodging and make the plants more sensitive to disease. Numerous studies has demonstrate that a lot of grasses accumulate silicon at its tissues, and the biggest part of this element is deposited on the leaf, that would work like a mechanical barrier to diseases come in. However, high levels of nitrogen can reduce the silica deposition at the plants. The objective of this study was to evaluate silicon and nitrogen content in shoot and silica deposition in upland rice leaf as a result of Si and N levels. The experimental design used was completely randomized in factorial schema 3 x 2 with five replications. The treatments consisted from levels of N (5, 75 and 150 mg dm-3 of soil) in urea form and two levels of SiO2 (0 e 400 mg dm-3) in calcium silicate form (Wollastonita). The increased of urea fertilization reduced the silicon content of rice plants and the silica deposition at the external cells wall the epidermal rice leafs.

Increased growth and phenolic compounds in bilberry (Vaccinium myrtillus L.) following forest clear-cutting

Bilberry (Vaccinium myrtillus L.) is a keystone species in boreal forests, but the few studies available concerning influence of forestry on bilberry growth, reproduction and chemical composition reveal conflicting results. We compared bilberry from mature stands and clear-cuts in a spruce forest landscape in south-central Norway, and applied the following experimental treatments: fertilisation, root cutting and flower removal to evaluate the effect of resource availability. During the second growing season we estimated bilberry shoot biomass as well as flowering and berry production, while bilberry shoots and leaves were collected in early summer and autumn for analysis of nitrogen, carbon and phenolic compound concentrations. The biomass of bilberry shoots was highest on clear-cuts and after fertilisation. All groups of phenolic compounds were also highest on clear-cuts, and phenolic acids and flavonols were highest in non-fertilised plots. Catechins and condensed tannins were highest in autumn, while phenolic acids and flavonols were highest in summer. Removal of flowers and root cutting had no effects. Nitrogen concentrations in shoots were highest in summer, after fertilisation, and when flowers were removed. The amount of flowers was highest in non-fertilised, mature forest sites, while the berry production was not significantly affected by any of the treatments or the site type. Our results indicate that in the studied area, the performance of bilberry is not negatively affected by clear-cutting, it rather seems that the environment on the clear-cuts give the plants abundant resources for enhancements both in growth, reproduction and defence compared with the mature forest sites. In the eyes of a herbivore, however, the quality of bilberry shoots as a feed-plant may be reduced on a clear-cut because of the higher phenolic concentration.

Growing Media and Nutrient Solution Concentration Affect Vegetative Growth and Nutrition of Laelia anceps Lindl

The domestication of wild orchids for commercial production is a new endeavor, which may represent a sustainable alternative to the collection/harvest from natural populations of threatened or endangered orchid species. In the present study, the growth and nutrition of vegetative plants of Laelia anceps Lindl. as affected by three components of the growing medium (peat, volcanic rock, and/or horticultural grade charcoal) and the nutrient solution concentration, measured as osmotic potential (ψS), were assessed using mixture experiments methodology. Leaf dry mass (DM) was the highest when plants were irrigated with nutrient solutions of –0.076 MPa. The lower leaf DM at lower or higher ψS was influenced by the medium because plants grown in 100% volcanic rock exhibited no effect, whereas plants grown in either 100% charcoal or 100% peat had a marked reduction. Regardless of the ψS of the nutrient solution, the highest leaf DM was observed in mixtures of two components containing charcoal and peat at high proportions. Dry mass of pseudobulbs and roots was highest in plants irrigated with solutions of –0.051 MPa, especially in mixtures with charcoal or 100% peat. Decreasing the ψS of the nutrient solution resulted in increased shoot nitrogen (N) and potassium (K) concentrations and decreased concentration of phosphorus (P), calcium (Ca), magnesium (Mg), boron (B), manganese (Mn), zinc (Zn), and copper (Cu). Increasing charcoal proportion in the growing media resulted in increased plant iron (Fe) and Cu concentration. However, increasing volcanic rock reduced plant P and K and increased Mn concentration. A higher proportion of peat was correlated with a decrease in plant Fe concentration. Leaf DM fit models on which macronutrient:micronutrient or micronutrient:micronutrient ratios were calculated, suggesting that nutrient imbalance may be responsible for a plant’s responses. The coefficients with the higher values included a micronutrient:micronutrient ratio, suggesting that an extremely fine balance in the uptake of a given micronutrient in relation to other micro- or macronutrient is of major importance for adequate growth of Laelia.

English

Pinus wallichiana seeds were sown in polybags filled with sterilized riverbed sand in 2010. Seedlings were thinned out to one seedling per polybag, which were treated weekly with Ingestad pretreatment nutrientsolution for 4 weeks and then were fertigated with nitrogen levels of 0.99, 1.98, 2.97, 3.96, 4.95, 5.94, 6.93, 7.92, 8.91 and 9.90 mg and fixed levels of phosphorus, potassium, calcium and magnesium dissolved in 50 ml of water seedling-1 week-1 upto or until 28 weeks. Biomass allocation to needles, (separated by hand from shoot axis), stem (Includes hypocotyls and epicotyls) and roots increased significantly with the increase in nitrogen level and seedling age. At 7.92 mg level of nitrogen fertigation biomass allocation and nitrogen concentration partitioning at 28 weeks got increased by 190, 32 and 44%, and 179, 101 and 147% in needles, stem and roots, respectively as compared to control. Nitrogen concentration in shoot and root decreased at lower nitrogen level as seedlings age increased, but increased at higher nitrogen fertigation levels in needles, stem and roots. To the end of the experiment, nitrogen uptake per seedling increased, whereas, nitrogen use efficiency (NUE) decreased with the increasing nitrogen levels. Key words: Pinus wallichiana, Biomass allocation, nitrogen partitioning, nitrogen uptake, nitrogen use efficiency (NUE).

PHYSIOLOGICAL EFFECT OF SOME GROWTH RETARDANTS ON PERFORMANCE OF GROWTH, LODGING DEGREE AND YIELD OF RICE

Two field experiments were conducted at Research Farm of Rice Research and TrainingCenter, Sakha, Kafr El-Sheikh, Egypt during 2010 and 2011 seasons. The study aimed to evaluate the effect of Cycocel (CCC), a mixture of Cycocel and Dicloro Iso Butyric acid (DCIB) (MLU 208), Triapenthanol (RSW041I) and Uniconazole on physiological and growth behavior of rice plants, as well as lodging degree of Sakha 104 rice cultivar(long stem cultivar that is characterized by high rate of lodging).The most important results showed that CCC did not exhibit any significant retarding effect on rice plants .All levels of MLU 208, RSW04ll and Uniconazole markedly decreased the height of plants in the terms of decreasing its lodging degree. Number of tillers/m2, flag leaf area and dry weight of rice plants were increased under all growth retardants except CCC. Degree of lodging was decreased by the application of proper levels of MLU 208, RSW04ll and Uniconazole. RSW performed better regarding lodging and reduced it to 75% of the control. All growth retardants increased the concentration of Chlorophyll A and Chlorophyll B in rice leaves but caratenoids were decreased. Nitrogen concentration in shoots and grains was increased while K was decreased. GA3 concentration in shoots was decreased but ABA was increased by the application of MLU 208, RSW0411 and Uniconazole. The high levels of growth retardants increased the weight of l000-grain, starch and protein yields. Grain yield was the highest when Uniconazole, MLU 208and RSW041Iwere applied, respectively.

Response of rice nitrogen physiology to high nighttime temperature during vegetative stage.

The effects of night temperature on plant morphology and nitrogen accumulation were examined in rice (Oryza sativa L.) during vegetative growth. The results showed that the shoot biomass of the plants was greater at 27°C (high nighttime temperature, HNT) than at 22°C (CK). However, the increase in both shoot and root biomasses was not significant under 10 mg N/L. The shoot nitrogen concentrations were 16.1% and 16.7% higher in HNT than in CK under 160 and 40 mg N/L. These results suggest that plant N uptake was enhanced under HNT; however, the positive effect might be limited by the N status of the plants. In addition, leaf area, plant height, root maximum length, root and shoot nitrogen concentrations, soluble leaf protein content, and soluble leaf carbohydrate content were greater in HNT than in CK under 40 and 160 mg N/L, while fresh root volume, root number, and the content of free amino acid in leaf were not significantly different between HNT and CK regardless of nitrogen levels. Moreover, leaf GS activity under HNT was increased at 160 mg N/L compared with that under CK, which might partly explain the positive effect of HNT on soluble protein and carbohydrate content.

Growth and nodulation response of soybean (Glycine max L) to Bradyrhizobium inoculation and phosphorus levels under controlled condition in South Western Ethiopia

The study was conducted to investigate growth and nodulation response of Clark 63-K soybean variety toBradyrhizobium japonicum inoculation and phosphorus levels under lath house condition at Jima Agricultural Research Center in 2010. The crop was evaluated in terms of nodule number, nodule volume, nodule dry weight, shoot nitrogen content, plant height, number of pod bearing branches, shoot dry matter and root dry matter. The result revealed that an interaction effect of the main factors did not significantly (P < 0.05) influence number of pod bearing branches, shoot dry matter and root dry matter yield of the crop. In terms of shoot nitrogen content and plant height, Clark 63-K soybean had no response to inoculation when it was grown without phosphorus. However, inoculation significantly (p < 0.05) increased these parameters over the uninoculated control when 60, 120 and 180 mg kg-1 phosphorus were applied. For uninoculated and inoculated treatments, phosphorus significantly (p < 0.05) influenced all nodulation and growth traits. The three phosphorus treatments (60, 120 and 180 mg kg-1) significantly (p < 0.05) improved pod bearing branches, shoot and root dry matter yield over the untreated control. Inoculation coupled with 120 mg kg-1 phosphorus level being considered an optimal combination for Clark 63-K soybean production in the area. Key words: Growth, nodulation, phosphorus, soybean.

Demand-driven fertilization. Part II: Influence of demand-driven fertilization on shoot nitrogen concentration, growth rate, fructan storage and playing quality of golf turf

The ability of demand-driven fertilization, based on the growth potential provided by solar radiation and temperature, to regulate golf turf characteristics such as growth rate, leaf nitrogen (N) concentration, carbohydrate storage and playing quality was investigated in a 2-year field experiment at Landvik, Norway. Three N regimes (100, 60 and 40% of the estimated N requirement for maximum growth) were applied on a sand-based green with a turf cover consisting of creeping bentgrass, colonial bentgrass, velvet bentgrass, slender creeping red fescue or chewings fescue. In the 100% treatment, this corresponded to 3 (creeping bentgrass), 2.1 (colonial and velvet bentgrass) and 1.5 (chewings and slender creeping red fescue) kg N 100 m−2 yr−1. The weekly liquid fertilizer dose basically followed the potential growth curve provided by solar radiation and temperature from early April to late October. The turf was exposed to artificial wear and daily maintenance followed conventional standards. Growth, leaf N concentration, carbohydrate storage in clippings, green appearance and playing quality were determined once per month. The results indicated that solar radiation and temperature can successfully be used as driving variables when quantifying turf fertilizer requirements from early spring to late autumn. The desired leaf N concentration, i.e. growth rate, and the resulting effects on fructan content and playing quality can be achieved by raising or lowering the seasonal fertilizer curve. A leaf N level of 3.1–3.5% was indicated as the lower limit for producing healthy-looking turf with high playing quality.

Efficient nitrogen-fixing Rhizobium strains isolated from amazonian soils are highly tolerant to acidity and aluminium

One of the most cultivated and consumed vegetables in Brazil is the common bean, Phaseolus vulgaris L. The symbiosis of this plant species with nitrogen-fixing bacteria that are adapted to the stresses commonly found in tropical soils can increase production. The aim of this study was to evaluate the symbiotic effectiveness of bacterial strains from soils under different land uses in the Amazon region. Further, rhizobia tolerance to acidity and aluminium and the involvement of some possible physiological mechanisms of such tolerance were also investigated. In assessing the efficiency of biological nitrogen fixation, inoculation with strains UFLA04-195, UFLA04-173 and UFLA04-202, belonging to the genus Rhizobium, resulted in greater plant growth, higher shoot nitrogen content and good nodulation compared to the inoculation with the strain CIAT 899 (R. tropici), and to the mineral nitrogen control or Burkholderia fungorum strains that nodulated or not bean plants. These efficient strains grew better at pH 5.0 than at pH 6.0 or pH 6.9; they also tolerated up to 1 mmol l(-1) of Al(3+) and showed an increased production of exopolysaccharides where the growing rates were less (pH 6.0 and pH 6.9). With respect to aluminium, the highest production of EPS produced greater tolerance to this element. Taken together, these results indicate that the strains evaluated in this study were tolerant to acidity and aluminium; they appeared to have developed resistance mechanisms such as EPS production and a resistant cell outer membrane (indicated by resistance to polymyxin and methyl violet). As these strains also gave increased yields of the host species, further studies on whether to recommend these strains as inoculants are already underway.