Nitrogen fertiliser rate affects the frequency of nitrate-dissimilating Pseudomonas spp. in the rhizosphere of Lolium perenne grown under elevated pCO2 (Swiss FACE)

The effect of elevated pCO₂ (60 Pa) on the frequency of nitrate-dissimilating Pseudomonas (NDP) was investigated in the rhizosphere of fertilised Lolium perenne swards in the Swiss Free Air Carbon dioxide Enrichment (FACE) experiment. Numbers of cultivable root-associated Pseudomonas were greater under elevated (60 Pa) than under ambient (36 Pa) pCO₂ in both high and low N-fertilised swards. For both pCO₂ conditions, the NDP frequency decreased with closer root proximity to L. perenne roots in low fertilised swards. Anyway, in high N swards the NDP frequency was similar in root and soil fractions. Thus, N availability may be a major factor influencing NDP populations under elevated pCO₂, most likely due to increased competition for N between plant and nitrate-dissimilating bacteria.     

高氮条件下硫氮互作对冬小麦幼苗生长及氮、硫吸收利用的影响

本试验在水培条件下,研究了不同氮、硫水平对小麦幼苗生长及氮、硫吸收利用的影响。结果表明,同一供氮水平下,在0.15 mmol/L～2.40 mmol/L供硫水平范围内,小麦幼苗根系活力随供硫水平的提高而显著下降。在4 mmol/L供氮水平下提高供硫水平,小麦幼苗植株地上部含硫量和含氮量均增加,叶片光合速率提高,对叶片和次生根的发育均有促进作用,增加了地上部和根系干物质积累量,但硫素利用效率和氮素利用效率降低。在8 mmol/L供氮水平下,随供硫水平的提高,小麦幼苗地上部含硫量增加,含氮量无显著变化;供硫水平过高则导致幼苗叶片光合同化能力降低,对幼苗发育、地上部和根部干物质及氮硫素积累不利,氮、硫利用效率降低。在0.15 mmol/L供硫水平下提高供氮水平有利于增加小麦幼苗地上部和根系含氮量,在2.40 mmol/L供硫水平下提高供氮水平对小麦幼苗地上部和根系含氮量无显著影响。说明在一定的氮、硫供应水平下,氮素和硫素之间存在互促效应;供应水平过高,则相互抑制,不利于小麦对氮、硫的吸收和利用。不同品种对氮、硫供应水平的反应不同,与鲁麦21和烟农19相比,在4 mmol/L供氮水平下,较高的供硫水平更有利于豫麦34和淄麦12各器官硫素和氮素的积累;在8 mmol/L供氮水平下,豫麦34和淄麦12对过高供硫水平的耐受能力较强。     

A radiotracer technique for studying the nutrient release from different fertilizer materials and its uptake by plants

Abstract

In the technique presented, ³⁵S was used to label the soil available sulfur pool in intact pasture cores, which were subsequently treated with different sulfur fertilizers. Dilution of the ³⁵S in the soil by sulfur released from the fertilizers was monitored by measuring the changes in specific radioactivity of sulfur in plants growing in the cores. The results showed the effects of fertilizer form, particle size and application rate on the supply of sulfur to plants. This technique will be useful for making direct comparisons of the ability of commercially available fertilizers to maintain the supply of sulfur to plants.     

Long-Term Sulfur Fertilization: Effects on Crops and Residual Effects in a No-Till System of Argentinean Pampas

A long-term experiment has been conducted between 2001 and 2008 at Balcarce, Argentina, to determine the effect of sulfur (S) fertilization on S concentration in grains, crop yield, and residual S in soil. Two treatments were evaluated: annual S application to crops (15 kg ha^?1; S1) and a control with no S fertilization (S0). Sulfur fertilization only increased wheat yield (22% of the crops in the experiment). However, S application increased S concentration in grains in wheat, soybean, and maize (56% of the crops). Although, for all years, the S mass balance was positive for S1 and negative for S0, no differences in soil S extracted as sulfate (S-SO₄ ^?2) content previous to the crop sown were determined. The absence of differences in S accumulation in aboveground vegetative biomass and grain of the maize used as a check also suggest that long-term S fertilization did not affect the soil S availability for crops.     

Effect of Sulfur on the Yield and Essential and Nonessential Element Composition of Alfalfa Determined by Polarized Energy Dispersive X‐ray Fluorescence

Alfalfa crops were grown in the field at the University of Ankara (473939 E, 4385149 N), over two seasons between 2001 and 2003 with sulfur (S) supplied at two different rates. The experimental design was a randomized complete block with five replicates and three cutting dates in each season. Sulfur was applied at rates of 0 (control), 160 (S₁), and 240 (S₂) kg ha^?1 as gypsum. Alfalfa hay was harvested three times each year, and the concentrations of elements in the hay were measured by polarized energy dispersive x‐ray fluorescence (PEDXRF). Sulfur fertilization increased S concentrations and improved alfalfa hay yield for both years. Applied S slightly reduced phosphorus (P) and magnesium (Mg) concentrations in the first year and had no significant effect on the potassium (K) and calcium (Ca) concentrations of alfalfa hay for either year. The highest S (240 kg ha^?1 S) level increased sodium (Na) concentrations in the first year but decreased them in the second year. Sulfur application also decreased chloride (Cl) concentration in the first year. Molybdenum (Mo) concentration of the alfalfa was significantly reduced by S₁ treatment in year 1. Iron (Fe) concentration was increased by S₂ treatment in the second year, and zinc (Zn) concentration was increased by S₁ treatment in the first year. However, applied S had no effect on manganese (Mn), copper (Cu), titanium (Ti), vanadium (V), cobalt (Co), nickel (Ni), barium (Ba), uranium (U), and lead (Pb) concentrations for either year. Applied S decreased aluminum (Al) and silicon (Si) and increased bromine (Br) and rubidium (Rb) concentrations of alfalfa in the first year. In addition, strontium (Sr) concentration was increased by S₂ treatment in the first year but was decreased in the second year. The stage of cutting greatly affected mineral concentrations. Compared with the first cutting, S concentrations were higher in the second and third harvest for both years. In general, the concentrations of P, Mg, Na, Cl, Mo, Ti, V, Br, Co, Ba, Sr, Rb, U, and Pb were increased, whereas the concentrations of Fe, Zn, Mn, Cu, and Ni were decreased with later cutting. The concentrations of K and Ca did not vary between cuts.     

Effect of Elemental Sulfur Supply on Cadmium Uptake into Rice Seedlings When Cultivated in Low and Excess Cadmium Soils

Effects of sulfur (S) (0, 30 mg S kg^?1 soil) supply on cadmium (Cd) uptake into rice when cultivated in low-Cd soil [38.8 μg kg^?1 for diethylenetriaminepentaacetic acid (DTPA)–extractable Cd] and in excessive-Cd soil (748.7 μg kg^?1 for DTPA-extractable Cd) were investigated in a combined soil–sand culture experiment. The significant difference in the Cd uptake into rice between –S and +S treatments were observed in relation to soil Cd levels. When rice was exposed to excessive Cd soil, application of S restrained the uptake of Cd into rice, the S supply tended to increase Cd uptake into rice when cultivated in low-Cd soil. The possible mechanisms explaining the interactions among soil Cd level, S supply, and Cd accumulation in rice are proposed. These results suggest that S fertilization may be important for the development approaches to reducing Cd accumulation in rice when cultivated Cd-contaminated soils.     

Alfalfa Responses to Combined Use of Lime and Limiting Nutrients on an Acidic Soil

An on-farm field experiment was conducted on an acidic soil to investigate the effects of combined use of lime and deficient nutrients on herbage yield of alfalfa (Medicago sativa L.). Omitting lime and limiting nutrients led to elevated concentrations of aluminium (Al), iron (Fe), and manganese (Mn) in alfalfa leaves and stems and caused severe reductions in herbage yield of alfalfa. Combined use of lime (2 t ha^?1) and nutrients [phosphorus (P): 20 kg ha^?1, sulfur (S): 20 kg ha^?1, zinc (Zn): 4 kg ha^?1, and boron (B): 2 kg ha^?1] had the maximum increase in groundcover, root biomass, nodulation, leaf retention, leaf-to-stem ratio, herbage yield, crude protein, and nutrient composition of alfalfa. These beneficial effects were due to raised soil pH; improved calcium (Ca), P, S, Zn, and B nutrition; and reduced Al, Mn, and Fe toxicity. Aluminium and all the nutrients except copper (Cu) were more concentrated in alfalfa leaves than stems.

Aluminum concentration was about three times greater in the lower leaves than in upper leaves. Lower leaves also had much greater concentrations of Ca, Mg, K, S, Fe, Mn, Cu, and B compared with upper leaves. In contrast, P and Zn concentrations were greater in the upper leaves than in lower leaves. Results suggest that the combined use of lime and all the limiting nutrients may realize potential beneficial effects of alfalfa on acidic soils where more than one essential nutrient is deficient. This may increase growth potential, nitrogen contributions, and groundcover by alfalfa and reduce soil erosion and runoff.     

Sulfur in soils

Sulfur (S) deficiency of crops, which has been reported with increasing frequency over the past two decades on a worldwide scale, is a factor that reduces yield and affects the quality of harvested products. Especially in Western European countries, incidence of S deficiency has increasingly been reported in Brassicaceae. For this reason, more attention should be paid to the optimization of S‐fertilizer application, in order to cover plant S requirements whilst minimizing environmental impacts. In soils, S exists in inorganic and organic forms. While sulfate (SO ), which is a direct S source for plants, contributes up to 5% of total soil S, generally more than 95% of soil S are organically bound. Organic S is divided into sulfate ester and carbon‐bonded S. Although not directly plant‐available, organically bound S may potentially contribute to the S supply of plants, especially in deficiency situations. Sulfur turnover involves both biochemical and biological mineralization. Biochemical mineralization, which is the release of SO from the ester sulfate pool through enzymatic hydrolysis, is controlled by S supply, while the biological mineralization is driven by the microbial need for organic C to provide energy.     

Influence of Sulfur Fertilization on Infection of Potato Tubers with Rhizoctonia solani and Streptomyces scabies

ABSTRACT

Under conditions of sulfur (S)-deficient soil, applied S fertilization had a significant repressive effect on fungal infections such as that of oilseed rape and grapes with light leaf spot (Pyrenopeziza brassicae) and powdery mildew (Uncinula necator), respectively. For potatoes (Solanum tuberosum L.) it has been shown in earlier literature that elemental sulfur fertilization increased yield of potato tubers and improved tuber quality and resistance against Streptomyces scabies; the bactericidal effect was attributed to a reduced soil pH. So far, however, no information is available about the influence of S supply on bacterial and fungal diseases in potatoes. It was the aim of the present investigation to quantify the influence of S form and dose on infections of potato tubers with Rhizoctonia solani and Streptomyces scabies as a contribution to plant nutrition strategies for healthier plants. Field experiments with potatoes were conducted in 2001 and 2002 in Poland in a split-plot design with different sulfur forms (elemental S and K₂SO₄) and rates (0, 25, and 50 kg ha^{? 1} S). The application of sulfur significantly increased tuber yield in both years of experimentation. Generally, with increasing sulfur dose a significant decrease of the infection rate with Rhizoctonia solani was found for elemental S as well as for K₂SO₄ applications. Infection rate and severity of the disease was improved only by elemental S application due to a reduction in soil pH in the case of Streptomyces scabies. Thus it can be concluded that the health-promoting effect of sulfur fertilization was related mainly to the S status of the plant in case of infections with Rhizoctonia solani, while for Streptomyces scabies no mechanisms of S-induced resistance were found. The identification of differences in the S metabolism of Rhizoctonia solani and Streptomyces scabies may therefore elucidate S-induced resistance mechanisms in plants.     

Sulfur metabolism in Allium cepa is hardly affected by chloride and sulfate salinity

Salinity as a major agricultural problem can affect crop growth and quality. Onion (Allium cepa L.) plant contains a wide variety of sulfur-containing compounds which may be involved in plant protection against salt stress. In the current study, a similar reduction in growth caused by chloride and sulfate salts was observed when onion was exposed to equimolar concentrations of Na⁺. Also, no difference was observed for shoot/root ratio and dry matter content of roots and shoots. Plants accumulated Na⁺ and the respective anions (chloride and sulfate) which in turn caused changes in the content of other nutrients. The content of potassium and calcium was decreased more than the other elements by both sodium salts. Sulfate salinity resulted in substantial increase in total sulfur and sulfate content but chloride salinity affected neither the total sulfur nor sulfate content of the roots and shoots, only in onion exposed to 200 mM chloride salt, those of roots and shoots were reduced. Furthermore, the water-soluble non-protein thiol content as well as the content of alliin remained rather unaffected. In conclusion, either salts affected the uptake and distribution of sulfate in onion, but had no or only a minor effect on the plant sulfur metabolism.