Sulfur composition of soybeans as affected by light and temperature

Abstract

Growth‐chamber experiments on effects of light and temperature on S constituents of leaf blades, total S concentrations, and S uptake in whole soybean plants are reported. A 5‐day dark period decreased concentration of soluble protein S and increased concentrations of nonsol‐uble S, soluble nonprotein S, sulfate S, organic S, reduced nonprotein S, and total S of leaf blades. Soluble protein was decreased but S content of soluble protein was unaffected. For whole plants, dry weight and S uptake decreased and S concentration increased.

A 5‐day cold period increased leaf blade concentrations of soluble protein S, soluble nonprotein S, sulfate S, organic S, and total S, but had little effect on nonsoluble S and reduced nonprotein S. Soluble protein increased but S content per unit of protein was unaffected. For whole plants, dry weight was less, S concentration increased, and S upr take was unaffected.     

Calcium nutrition of white rose potato in relation to growth and leaf minerals

Abstract

White Rose potato plants were grown in nutrient solutions containing Ca from 0 to 20 meq/l. After 32 days of growth, 16 plant parts were taken for analysis. The critical level for the immature to the recently matured leaf was determined to be about 0.15% Ca for the petiole and the blade tissues at the breaking point of the transition zone. Ca concentrations of petioles and blades (dry basis) increased with leaf age with the greatest increase in the blade tissues. The petioles of recently matured leaves under severe Ca deficiency were higher in Na, Mg, and PO₄‐P, lower in N0₃‐N and about the same in K concentration in comparison with non‐deficient petioles while the corresponding blades did not differ appreciably. Calcium deficiency has no major effect on the uptake of these minerals since all values were in the adequate range.     

Diagnosis of zinc deficiency in canola by plant analysis

Abstract

Canola plants (Brassica napus cv. Eureka) were grown in soil culture with seven levels of zinc (Zn) supply (0, 67, 133, 200, 267, 533, and 1,067 μg Zn/kg soil) for 39 days. Critical Zn concentrations in young leaf blades and petioles were established for the diagnosis of Zn deficiency in canola plants during vegetative growth by assessing the relationship between the Zn concentration in the leaves and shoot dry matter on 22 and 39 days after sowing (DAS). Zinc concentrations in leaf blades and petioles increased with increasing Zn supply, but Zn concentrations were always 50% higher in the youngest open leaf (YOL) than in the youngest mature leaf (YML). The relationship between shoot dry matter and Zn concentrations in leaf petioles exhibited Piper‐Steenbjerg curvature, indicating their unsuitability for Zn‐deficiency diagnosis either alone or by inclusion with leaf blades. By contrast, inclusion of leaf mid‐ribs with leaf blades did not alter the relationship between shoot dry matter and Zn concentrations, nor the critical Zn concentration. Critical Zn concentrations in the YOL, YOL+1, and YOL+2 blade on 39 DAS, corresponding with the stem elongation stage, were 15–17, 9–10, and 7–8 mg Zn/kg dry matter, respectvely. In comparison, the critical Zn concentration in the YOL+2 leaf blades with mid‐ribs was 7–8 mg Zn/kg dry matter. In conclusion, during the vegetative stage up to stem elongation, YOL+2 leaf blades which are also the YML are recommended for the diagnosis of Zn deficiency in canola plants with the critical Zn concentration being 7–8 mg Zn/kg dry matter.     

Diagnosis of zinc deficiency in peanut (Arachis hypogaea L.) by plant analysis

Abstract

Critical values of zinc (Zn) concentration in young leaves Here established for the diagnosis of Zn deficiency in peanut by examining the relationship of Zn concentration in leaves to shoot dry matter (DM) at two growth stages of plants grown in pots of Zn deficient sand at seven levels of Zn supply (0, 67, 133, 200 267, 533, and 1067 μg Zn/kg soil). Zinc deficient peanut accumulated reddish pigments in stems, petioles and leaf veins in addition to the more common symptoms of Zn deficiency in plants. Zinc concentrations increased with increasing Zn supply in the blades of the youngest fully expanded leaf (YFEL) and in the blades of the leaves immediately older (YFEL+1) and younger (YFEL‐1) than it: they also increased with increasing Zn supply in the petioles of the YFEL+1 and YFEL and in the basal stem internode but their Zn concentrations Here always much lower than those in the blades. Critical Zn concentrations in the blades of the YFEL and YFEL+1 Here 8–10 mg Zn/kg DM at early pegging and mid pod filling: values for YFEL‐1 were similar but more variable. The blade of the YFEL is recommended for diagnosis of Zn deficiency in peanut and 8–10 mg Zn/kg DM as its critical value.     

Phosphorus‐deficiency effects on response of symbiotic N2 fixation and carbohydrate status in soybean to atmospheric CO2 enrichment

The impact of phosphorus (P) deficiency on response of symbiotic N₂ fixation and carbohydrate accumulation in soybean (Glycine max [L.] Merr.) to atmospheric CO₂ enrichment was examined. Plants inoculated with Bradyrhizobium japonicum MN 110 were grown in growth chambers with controlled atmospheres of 400 and 800 μL CO₂ L^‐1 and supplied either 1.0 mM‐P (P‐sufficient) or 0.05 mM‐P (P‐deficient) nitrogen (N)‐free nutrient solution. When plants were supplied with sufficient P, CO₂ enrichment significantly increased whole plant dry mass (83%), nodule mass (67%), total nitrogenase activity (58%), and N (35%) and P (47%) accumulation at 35 days after transplanting (DAT). Under sufficient P supply, CO₂ enrichment significantly increased starch concentrations in nodules compared to the normal atmospheric CO₂ treatment. Under normal CO₂ levels (400 μL L^‐1) nonstructural carbohydrate concentration (starch plus soluble sugar) was significantly higher in leaves of P‐deficient plants than in leaves of P‐sufficient plants in which nonstructural carbohydrate concentration exhibited a strong diurnal pattern. Under deficient P supply whole plant dry mass, symbiotic N₂‐fixation parameters, and N and P accumulation were not enhanced by atmospheric CO₂ enrichment. Phosphorus deficiency decreased nonstructural carbohydrate accumulation in nodules at the end of a 10‐day period in which functional activity was developing by 86% relative to P‐sufficient controls. While P deficiency elicited significant increases in the nonstructural carbohydrate concentration in leaves, it caused significant decreases in the nonstructural carbohydrate concentration in nodules over the diurnal cycle from 30 to 31 DAT. Collectively, these results indicate that the lack of a symbiotic N₂‐fixation response to atmospheric CO₂ enrichment by P‐deficient plants may be related to the decreased carbohydrate status of nodules.     

Nitrogen and phosphorus nutritional interactions in a CO2 enriched environment

Nonnodulated soybean plants (Glycine max. [L.] Merr. ‘Lee') were supplied with nutrient solutions containing growth limiting concentrations of N or P to examine effects on N‐ and P‐uptake efficiencies (mg nutrient accumulated/gdw root) and utilization efficiencies in dry matter production (gdw²/mg nutrient). Nutritional treatments were imposed in aerial environments containing either 350 or 700 μL/L atmospheric CO₂ to determine whether the nutrient interactions were modified when growth rates were altered.

Nutrient‐stress treatments decreased growth and N‐ and P‐uptake and utilization efficiencies at 27 days after transplanting (DAT) and seed yield at maturity (98 DAT). Atmospheric CO₂ enrichment increased growth and N‐ and P‐utilization efficiencies at 27 DAT and seed yield in all nutritional treatments and did not affect N‐ and P‐uptake efficiencies at 27 DAT. Parameter responses to nutrient stress at 27 DAT were not altered by atmospheric CO₂ enrichment and vice versa. Nutrient‐stress treatments lowered the relative seed yield response to atmospheric CO₂ enrichment.

Decreased total‐N uptake by P‐stressed plants was associated with both decreased root growth and N‐uptake efficiency of the roots. Nitrogen‐utilization efficiency was also decreased by P‐stress. This response was associated with decreased plant growth as total‐N uptake and plant growth were decreased to the same extent by P stress resulting in unaltered tissue N concentrations. In contrast, decreased total P‐uptake by N‐stressed plants was associated with a restriction in root growth as P‐uptake efficiency of the roots was unaltered. This response was coupled with an increased root‐to‐shoot dry weight ratio; thus shoot and whole‐plant growth were decreased to a much greater extent than total‐P uptake which resulted in elevated P concentrations in the tissue. Therefore, P‐utilization efficiency was markedly reduced by N stress.     

Nutrient deficiency diagnosis of corn (Zea Mays L.) plants from yield and composition responses to additions of N and S

Abstract

Corn (Zea mays L.) was grown in the greenhouse in a Laughlin (Ultic Haploxeroll) loam soil, with various amounts of N and S added in order to determine possible interactions of these nutrients with the relationship between plant composition and grain yields. Previous field experience and preliminary experiments had shown that this soil gave yield responses to N and S additions.

Regression equations were used to describe the relationship between composition of various plant parts and grain yields. The best correlation (R² = 0.943) was obtained using the total N concentration in leaf samples taken at the silking stage, but excluding data from plants which, based on their amide N concentrations (greater than 500 ppm), were considered S deficient. Calculations using the first derivative of the cubic polynomial indicated that a concentration of 2.5% N in the lower leaves was necessary in order to obtain maximum grain yields. The concentrations of total N in the upper leaves and the stalks at the silking stage also correlated well with the grain yields. The relationship of NO₃‐N in the stalks at silking to grain yields could be better described mathematically with an exponential function, but the correlation coefficient was low (R² = 0.58). The responses of two genotypes, one containing the opaque ‐ 2 gene, the other its normal counterpart, were similar.

The total N concentration in the leaves collected at the tassel stage did not correlate quite as well with grain yield as those collected later, but using the exponential model NO₃‐N concentrations in the stalks at the earlier stage showed a closer relationship to grain yield than for samples collected at silking. Excluding data for the plants showing S deficiency, a correlation coefficient of 0.90 was obtained. At both tasseling and silking stages, the S deficient plants were characterized by high N:S ratios, with values of 18 to 50 for the stalks, compared to values of less than 10 for the S adequate plants. The marked effect of inadequate S on grain formation was not evident in the amounts of leaves and stalks produced.

Field studies will be necessary to evaluate further the merit of the diagnostic procedure indicated by these experiments.     

Nitrogen nutrition of white rose potato in relation to vegetative growth and mineral content of leaves and roots

Abstract

White Rose potato plants were transplanted to nutrient solutions provided vith nine treatments of Ca(NO₃)₂ ranging from 0 to 64 mmoles per liter. Eighteen days later, symptoms of N‐deficiency ranging from very severe to none vere observed. The plants at this time were harvested, and leaves were sampled, oven dried, ground, and then analysed for K, Na, Ca, Mg, NO₃‐N, and acetic acid soluble H₂PO₂‐P.

Shoot and fibrous root growth increased with nitrate supply to an optimum, and then decreased with increased nitrate supply, suggesting nitrate toxicity due to the high nitrate supply of the nutrient solution. The nitrate content of the tissues increased with increased nitrate supply. Toxicity due to excess nitrate was associated with a very high nitrate content of the leaf tissues.

The critical NO₃‐N concentration at a 10% reduction in vegetative growth due to N‐deficiency is about 2000 ppm (0.2%) on a dry basis for the petioles and about 300 ppm (0.03%) for the blades of recently matured leaves.     

Rice genotype differences in nutrient status under excessive ferric‐iron conditions

To investigate the relationship between rice genotypic variation in tolerance to iron (Fe) toxicity and nutrient element status, 10 rice genotypes with different growing performances under Fe toxicity were grown under normal culture solution and with excessive ferrous (Fe²⁺)‐Fe concentrations of 250 and 500 mg Fe²⁺ L^‐1. A close relationship was obtained between the relative ratio of symptomatic leaf numbers to total leaf numbers (SLN/TLN) and a relative decrease in dry matter under Fe²⁺‐toxicity conditions. The genotypic variations in nitrogen (N), phosphorus (P), potassium (K), and magnesium (Mg) uptake were evaluated by the relative decrease in the N, P, K, and Mg content in the plants. Remarkable genotypic variation in tolerance to excessive Fe²⁺ was observed. The results indicated that excessive Fe²⁺ reduced N, P, K, and Mg uptake. The nutrient element concentrations, however, were still higher above deficient criteria even in severely affected plants, suggesting that the retardation of growth may not be intirely due to the deficiency of these elements in plants at the seedling stage. Significant correlations were found between the genotypic variation and the decrease in N, P, K, and Mg uptake and in their tolerance to Fe²⁺ toxicity, which suggests that the ability to maintain higher nutrient element uptake under a Fe²⁺‐toxic condition contributes the tolerance to Fe²⁺ toxicity.     

Influence of nitrate and ammonium on critical nitrogen deficiency concentrations and mineral composition of Dupontia fisheri grown hydroponically in a controlled environment

Dupontia fisheri plants, derived from a clone, were propagated in plant growth chambers by the open‐pot nutrient solution technique, with vermiculite as the solid phase. The plants were illuminated continuously at 21, 500 lux (2,000 f.c.) by a combination of fluorescent and incandescent lamps. Air temperature was kept constant at 20°C. The plants, after transplanting to 20‐liter pots (closed‐pot system), were nourished by a modified half‐strength Hoagland solution, supplied with a one time addition of nitrogen at the rate of zero, 0.25, 0.5, 1.0, 2.0, 4.0 and 8.0 me/1 derived from (NH₄)₂SO₄, Ca(NO₃)₂ or NH₄NO₃. They were harvested 49 days after transplanting at a time when those in the three lowest treatments were distinctly deficient in nitrogen. Critical nitrate‐N values (the concentration at a 10% reduction in vegetative growth) were found to be identical, at 100 μg/g (dry basis), in the stem, blade‐1 and blade‐3 tissues, and those for total‐N at 0.901, 2.251, and 2.501, respectively.

Absence of nitrate in stem tissue indicated a nitrogen deficiency while the total‐N value indicated the degree of deficiency: the lower the value the greater the deficiency. Nitrogen also influenced the mineral composition of stem and blade tissues directly, mainly by ionic competition, and possibly indirectly, by decreasing dry matter content as the plants became less deficient in nitrogen. Transitions from nitrogen deficiency to sufficiency caused relatively large changes in the concentration of other nutrients in both stems and blades, but sometimes in opposite directions. For example, soluble‐P and total‐P in stems increased dramatically with increases in total‐N, but decreased greatly in the blade‐1 and blade‐3 tissues. Potassium, on the other hand, increased greatly in all tisues with increases in total‐N. These effects were much smaller for phosphorus with ammonium‐N as a nitrogen source than with nitrate, but for potassium there was no appreciable effect of nitrogen source in stems, a larger effect in blade‐1 and an erratic effect in blade‐3. Additionally, there were rather large decreases in manganese concentration with increases in nitrogen while effects on other nutrients were either small (Mg and Zn) or not significant (Ca, Fe, Cu and Na). All values were above critical concentrations.     

Effects of deep placement of controlled-release nitrogen fertilizer on soybean growth and yield under sulfur deficiency

Sulfur (S) and Nitrogen (N) metabolisms in plants are interacted and it is known that S deficiency decrease N absorption and metabolism. In leguminous plants S deficiency also decreases N₂ fixation by rhizobia in the nodules. Deep placement of a controlled-release N fertilizer is a good method to provide nitrogen to soybean without inhibiting N₂ fixation; thus, it was hypothesized that this method is able to provide nitrogen effectively to sulfur-deficient soybean plants. In this study effects of deep placement of coated urea on S-N physicological interaction, growth and productivity in soybean plants were examined using pot experiments. Soybean plants were grown with sulfate concentrations of 30, 100, or 1000 μM, with or without deep placement of coated urea. Shoot weights at the developing stage were not affected by S deficiency. SPAD values of leaves during the flowering stage decreased with S deficiency and increased with the deep placement of coated urea. S deficiency decreased seed weight per plant at the harvesting stage, but this decrease was attenuated by the deep placement of coated urea. N and S content in shoots at the developing stage increased with the deep placement of coated urea, whereas in seeds, only the N content increased. N₂ fixation activity based on the relative ureide-N content in xylem sap indicated that the deep placement of coated urea did not inhibit N₂ fixation activity at the early flowering stage. Without deep placement of coated urea, the relative ureide-N content decreased under S deficiency at the seed filling stage. These results suggest that the deep placement of coated urea is an efficient method to supply N to support soybean yield under S deficiency.

Abbreviations: Deep+: with deep placement of coated urea; Deep–: without deep placement of coated urea     

Effect of dicyandiamide on growth and nutrient uptake of cotton

Abstract

The nitrification inhibitor dicyandiamide (DCD) offers potential for improving efficiency of N applications to cotton grown on sandy soils of the southeastern Coastal Plain. Research has indicated that cotton is sensitive to DCD. The purpose of this greenhouse experiment was to investigate the effect of DCD on growth and nutrient uptake of DPL 90 cotton grown for 73 days in pots containing a typical Coastal Plain soil (Norfolk sandy loam, Typic Paleudult). Nitrogen (50 mg kg^‐1) as NaNO₃ or urea, and DCD (0, 2.5, 5, 10, 15 and 20 mg kg^‐1) were applied to the soil at first true leaf and plants were harvested 58 days later. Sodium nitrate increased leaf dry weight and total dry weight of plants 9.1 and 6.0%, respectively, over urea fertilized plants. Leaf area, dryweight, and stem dry weight were reduced linearly with DCD. Fertilization with urea increased concentrations of leaf P, K, and Mn and reduced the concentration of Mg in leaf tissue. Dicyandiamide increased leaf N, P, and K concentrations but reduced concentrations of Ca, Mg, and Mn. Uptake rates (μg^‐1 g^‐1 fresh root day^‐1) of Ca and Mg were increased 7.5 and 13.7%, respectively, with NaNO₃ vs. urea, while P uptake rate was 15.5% greater for urea‐fertilized plants vs. NaNO₃‐fertilized plants. Dicyandiamide reduced Ca and Mg uptake rates. Phosphorus uptake rates were increased by DCD when urea was the N source. The effects of DCD on cotton growth and nutrient uptake generally resulted from the compound itself and were not an indirect result of nitrification inhibition. Although significant reductions in plant growth did not occur unless DCD exceeded that normally applied with recommended N rates on this soil, these results suggest a need for caution when applying DCD to cotton grown on sandy soils.     

Positional difference in potassium concentration as diagnostic index relating to plant K status and yield level in rice (Oryza sativa L.)

Plant tissue testing is used as a guide for rice (Oryza sativa L.) fertilization and has been extensively used in the diagnosis of potassium (K) deficiency. However, little attention has been paid to the variation in the diagnostic index of K status in different parts of the rice plant. Here, we assessed the feasibility by testing K concentrations of whole plants, leaf blades and leaf sheaths to develop a suitable diagnostic index of plant K status and yield level in rice under different K application rates. The results showed that this research could satisfy the requirements of K status diagnosis, based on the quadratic-plus-plateau relationship between K application rates and grain yield. The K concentrations of the leaf blades and leaf sheaths on the main stem showed differences based on position. Leaf blade K concentrations significantly decreased from the top of the plant to the bottom in the effective tillering and jointing stages. Conversely, K concentrations in the lower leaf blades exceeded those in the upper leaf blades in the booting and full heading stages. K concentrations in the leaf sheath were significantly reduced with declining leaf position except during the jointing stage under high K treatments. Leaf sheath/leaf blade K concentration ratios increased significantly more in lower tissues than in upper plant tissues. Correlation analysis showed that the K concentrations of all sampled plant tissues were positively correlated to plant K uptake and grain yield. However, K concentrations of the whole plant were more useful as a diagnostic index at the effective tillering stage than at other growth stages. Leaf sheaths in lower positions were preferable to upper leaf sheaths and all leaf blades for evaluating plant K status, although their K concentrations were greatly influenced by plant growth stage. Furthermore, this study demonstrated that the ratio between the K concentrations of the first and fourth leaf blades (LBKR_1/4) was grouped into significantly exponential curves (P < 0.01) to describe the relationship between plant K uptake and relative grain yield. Thus, LBKR_1/4 could be an ideal indicator of rice plant K status and yield level, as it eliminated the effects of plant growth stage.     

High night temperature stimulates photosynthesis,biomass production and growth during the vegetative stage of rice plants

Abstract

The effects of night temperature on biomass accumulation and plant morphology were examined in rice (Oryza sativa L.) during vegetative growth. Plants were grown under three different night temperatures (17, 22 and 27°C) for 63 days. The day temperature was maintained at 27°C in all treatments. The final biomass of the plants was greatest in the plants grown at the highest night temperature. Total leaf area and tiller number were also the greatest in this treatment. Growth analysis indicated that the relative growth rate in the 27°C night-temperature treatment was maximal between days 21–42 and this was caused by increases in leaf area ratio, leaf weight ratio and specific leaf area. Plant total nitrogen contents did not differ among treatments. However, nitrogen allocation to the leaf blades was highest and the accumulation of sucrose and starch in the leaf blades and sheaths was the lowest in the 27°C night-temperature treatment by day 42. Despite this, dark respiration was also highest, and both the gross and net rates of CO₂ uptake at the level of the whole plant at day 63 were the highest in the 27°C night-temperature treatment. Thus, high night temperature strongly stimulated the growth of leaf blades during the early stage of rice plant growth, leading to increased biomass during the vegetative stage of the rice plants. As the CO₂ uptake rate per total leaf area was higher, photosynthesis at the level of the whole plant was also stimulated by a high night temperature.     

Differential response of two taro cultivars to aluminum: II. Plant mineral concentrations

Abstract

One proposed mechanism of aluminum (Al)‐tolerance involves the ability of plants to maintain uptake of essential mineral elements in the presence of Al. To examine this hypothesis, taro [Colocasia esculenta (L.) Schott] cultivars (cv.) Lehua maoli and Bun long were grown in hydroponic solution at six initial Al levels (0, 110, 220, 440, 890, and 1330 μM Al), and plant mineral concentrations were determined after 27 days. Increasing Al levels significantly increased Al concentrations in taro leaf blades, petioles, and roots. This increase in Al concentrations in the leaf blades as solution Al levels increased was greater for Al‐sensitive cv. Bun long compared to cv. Lehua maoli, resulting in significant interaction between Al and cultivar effects. However, no significant cultivar differences were found for Al concentrations in the petioles or roots. Increasing Al levels in solution significantly depressed concentrations of calcium (Ca), magnesium (Mg), manganese (Mn), and iron (Fe) in taro leaf blades, and significantly depressed concentrations of Ca, Mg, copper (Cu), and zinc (Zn) in taro roots. Aluminum‐induced Ca deficiency appeared to be one possible mechanism of Al phototoxicity in taro, becvasue Ca concentrations in the leaf blades and roots at the higher Al levels were within the critical deficiency range reported for taro. Significant cultivar differences were found, in which Al‐tolerant cv. Lehua maoli had significantly greater Ca and Cu concentrations in the roots, and significantly greater potassium (K) concentrations in the leaf blades across all Al levels. Our results show that Al‐tolerance in taro cultivars is associated with the ability to maintain uptake of essential mineral nutrients, particularly Ca and K, in the presence of Al.     

Yield,nutrient, and soil sulfur response to ammonium sulfate fertilization of soybean cultivars 1

With the reduction of sulfur levels in high‐analysis nitrogen (N) and phosphorus (P) fertilizers and in atmospheric deposition, sulfur (S) fertilization may become more important, especially with intensive cropping systems. When high clay content is likely to limit root development into the subsoil, low extractable sulfate‐sulfur (SO₄‐S) levels in the topsoil may suggest possible plant response to S fertilization. Even though ammonium sulfate [(NH₄)₂SO₄] is widely used and readily available for plant uptake, field data are limited on the use of (NH₄)2SO₄ as an S source for soybeans [Glycine max (L.) Merr.]. A study was initiated to determine the effect of S fertilization as (NH₄)₂SO₄ on: (i) the yield, seed weight, grain quality, and leaf and whole‐plant nutrient concentrations of four soybean cultivars grown on soils with high clay content subsoils; and (ii) selected soil chemical characteristics. Sulfur rates were 0, 28, 56, and 84 kg/ha, and soybean cultivars were two Maturity Group IV beans, DeSoto and Douglas, and two Maturity Group V beans, Bay and Essex.

The study was conducted on a Parsons silt loam soil (fine, mixed, thermic, Mollic Albaqualf) in 1986 and 1987, and on a Cherokee silt loam (fine, mixed, thermic, Typic Albaqualf) in 1987. Sulfur application did not significantly affect soybean yield or seed protein or oil concentrations. For whole plants, S concentration increased and N:S ratios decreased with increasing S fertilization. Similar trends were found in soybean leaves. Although N:S ratios of both whole plant and leaf tissue were lowered with S fertilization, the values generally were not below 20:1 which is above cited critical levels. Fertilization with (NH₄)₂SO₄ increased the levels of extractable SO₄‐S in the soil, especially in the 15–30 cm depth. The first‐year accumulation of soil SO₄‐S with increasing S fertilization appeared to be more at a site that was lower in organic matter.     

Effects of Rhizobium inoculation and magnesium application on growth and nodulation of soybean (Glycine max L.)

Abstract

Magnesium (Mg) deficiency is one of the major nutritional problems in tropic and subtropic areas, where the most soils are acidic. In this study, the effects of Mg application and Bradyrhizobium inoculation on growth, nodulation, symbiotic nitrogen (N) fixation as well as N nutrition status in soybean (Glycine max L.) were investigated in hydroponics under greenhouse conditions. With the increase of Mg up to 0.75?mM at low N and up to 0.5?mM at high N solutions, the dry weights of shoots, roots, and pod grain yield in soybean were increased, while further increase in Mg supply inhibited soybean growth. The availability of Mg was found to entail an improved uptake of N by plants and nodulation process in the root by Bradyrhizobium. Inoculation with rhizobial inoculants not only formed many nodules, but also increased soybean shoot, root biomass and yield, as well as plant N nutrient status.     

Mineral‐nutrient synergism and dilution responses to nitrogen fertilizer in field‐grown maize

Nitrogen (N)‐fertilizer applications to field‐grown maize may result in a dilution response whereby essential mineral‐element concentrations in shoots would decrease as shoot‐dry‐matter accumulation increased. To investigate this, the effect of N‐fertilizer treatments (no N or fertilizer rate based upon 5.3 or 8.5 t ha^–1 yield goal) on maize (Zea mays L.) shoot dry weight and shoot mineral concentrations (N, P, K, S, Mg, Ca, and Mn) at the sixth leaf (V6), twelfth leaf (V12), and tassel (VT) development stages were investigated in a 2‐year study conducted at Brookings, South Dakota (USA). With increasing N‐fertilizer application rates, shoot dry weight was greater and shoot P and K concentrations decreased. A possible explanation of this dilution response is that planting‐time P and K fertilizers, which were applied in a band near the seed furrow, may have enhanced the uptake of P and K in a manner that was independent of N‐fertilizer treatments. Increased shoot‐dry‐weight production due to the application of N fertilizers, if P and K uptake were similar across N‐fertilizer treatments, would lead to decreased shoot P and K concentrations in N‐sufficient compared with N‐deficient plants. Conversely, N‐fertilizer‐induced increases in shoot dry weight were accompanied by increased shoot concentrations of N, Ca, and Mn. This synergistic response between dry‐weight accumulation and shoot N concentration was present at all leaf developmental stages studied, while that for Ca was present only at VT. Thus, N fertilizer applications that increase shoot dry weight can affect the dilution and synergistic responses of specific mineral nutrients in maize shoots. Crop developmental stage as well as the location of these specific mineral nutrients in the soil profile might play important roles in mediating these responses.     

Corn forage yield and chemical composition as influenced by sulfur fertilization

Abstract

Soil sulfur (S) deficiency for plant growth has become an increasing problem in the United States. A field experiment was conducted to investigate effects of fertilization with 0 and 67 kg S/ha as a single or split application, in a Latin square design, on corn (Zea mays L.) forage yield and chemical composition. Sulfur fertilization by either method increased yield of whole plant and grain 7% and increased number of plants with two ears. Total S and sulfate‐S concentration in whole corn plants, leaf, stem, and grain were increased with S fertilization. The nitrogen (N):SO₄‐S ratio was a useful indicator of S deficiency.     

Macronutrient deficiency and anatomic modifications in crambe leaves

Abstract

This study had the objective of assessing growth, deficiency symptoms and leaf anatomy of crambe plants submitted to macronutrient availability. The experimental design was the complete randomized with four replications. The first treatment consisted of cultivating crambe plants in a nutrient solution completed with N, P, K, Ca, Mg, and S. Using the diagnosis by subtraction, the other treatments consisted of the same solution with individual omission of each nutrient, totaling seven treatments. Supplement of different solutions took place two weeks after emergence. One week forward, visual symptoms of deficiency started to be evaluated. By the end of the experiment, the number of leaves, number of branches, shoot dry matter and leaf anatomic parameters were evaluated. Nutrient deficiency limited shoot dry matter in the following order: N?>?Ca?>?P>Mg?>?S?>?K. Subtracting Ca from the solution was most limiting to crambe growth once plants did not even reach reproductive stages. Individual subtractions of each macronutrient anatomically altered crambe leaves, especially omitting Ca, K, and S, which reduced tissue thickness.