Polyphosphate‐fertilizer solution stability with time,temperature, and pH

Ammonium polyphosphate fertilizers are gaining popularity in agricultural industry due to ease of application and yield benefits in calcareous soils. In this study, the effects of temperature, pH, and time on the stability of ammonium polyphosphate–fertilizer solution simulating a range of storage conditions were evaluated. Ion chromatography was used for the speciation of orthophosphate, pyrophosphate, and tripolyphosphate in the polyphosphate‐fertilizer solution over time. Polyphosphate solutions were very stable when the pH was maintained close to neutral (pH 6.4) and the temperature was less than 25°C. In contrast, at the lowest pH (2.3) and highest temperature (50°C) almost all tripolyphosphate and 96% of pyrophosphate was hydrolyzed after 28 d. The hydrolysis rate constant for tripolyphosphate at 50°C was calculated to be 9.2 × 10^–7 s^–1 and the half‐life 20 d. At 25°C, the half‐life of tripolyphosphate was 34 d at pH 2.3 and 174 d at pH 5.4. The activation energy at pH 2.3 was 12.7 kJ mol^–1. The results demonstrate that increasing temperature and decreasing pH have a deleterious effect on the stability of condensed P species in polyphosphate fertilizer. The effect of acidification on polyphosphate‐fertilizer composition requires consideration when formulating mixed ammonium polyphosphate blends with acids and trace elements for application in the field.     

Effects of Source and Amount of Phosphorus on Sorption Kinetics in the Topsoil of a Highly Weathered Soil

Abstract

Soil chemical and physical reactions involving phosphorus (P) must be understood to predict the risk of P being transported from agricultural land to streams and lakes. The kinetics of P sorption by an Ultisols from West Virginia, USA, receiving P from fertilizers were compared to soils amended with turkey litter. Addition of 6.6 and 13.2 Mg turkey litter ha^?1 increased Bray 1P levels to about the same level as adding 53 and 115 kg P ha^?1, respectively. Phosphorus binding capacity decreased to a greater extent when P was added as fertilizer as compared to turkey litter. For example, P binding maximum was 360 mg P kg^?1 dry soil when soil was amended with 6.6 Mg turkey litter ha^?1 as compared to 260 mg P kg^?1 dry soil when amended with 53 kg P ha^?1. This study demonstrates that the decrease in P‐binding capacity with increasing soil P is less when P is added as turkey litter.     

Automated Modification of the Molybdenum Blue Colorimetric Method for Phosphorus Determination in Soil Extracts

A flow injection analysis (FIA) method capable of automation for molybdate reactive phosphorus (P) determination in soil extracts is described. Results obtained using this method in three soil extracts [calcium chloride (CaCl₂), Olsen, and Mehlich I] were the same as those provided by the manual molybdate blue colorimetric method. Linear range extending to 2 mg P L^?1, detection limits ranging from 6 to 26 µg L^?1 depending on the soil extract, and accurate recoveries from P‐spiked samples were achieved. The sensitivity of the system was around 0.3 absorbance units per mg P L^?1, and the sampling frequency was 72 samples h^?1, higher than those described for most of the flow injection methods.     

Elemental composition and release characteristics of some South African fly ashes and their potential for land application

Eight fly ash samples collected from South African power stations were evaluated for various chemical properties, liming potential and metal species release under incubation. All fly ashes had alkaline pH ranging from 10.97 to 12.75 with much wider variations of electrical conductivity (range 0.46–8.27 dS m^?1). Their total P content ranged from 553.3 to 1514 mg P kg^?1 and Olsen extractable P from 130 to 345.5 mg P kg^?1. Application of two of the fly ashes to three different soils showed a high ability to neutralize acidity, resulting in an average of 41% change in pH after 8 weeks of incubation. Across all three soils, the fly ash incorporation increased extractable P content from a P-deficient level to levels above 25 mg P kg^?1 in two of the three soils. Except for Cu, all metal species (Cr, Pb, Ni and Fe) showed significantly (P ≤ 0.05) low extractability under fly ash treated soils compared to the soil alone control. These results suggest that the South African fly ashes studied are effective liming materials and can provide essential elements such as P with minimum risk of soil contamination from metal species release.     

Phosphorus release from cattle manure ash as soil amendment in laboratory-scale tests

ABSTRACT

Excessive application of animal manure to farmland leads to phosphorus (P) loss into the surrounding water. Manure is incinerated to convert it to P-rich ash as a slow-release P fertilizer. However, the potential P loss and P availability for plants from cattle manure ash (CMA) have not been fully understood. The aims of this study were to determine the P release mechanism from CMA and to propose appropriate application rates that mitigate P loss and increase available P to soil in Fukushima, where the soil is deficient in nutrients after the replacement of cesium-137-contaminated soil with sandy mountain soil. Different P fractions in CMA were sequentially extracted with H₂O, 0.5 M NaHCO₃, 0.1 M NaOH, and 1 M HCl. Phosphorus contents in different fractions of CMA were in the order of HCl–P > NaHCO₃–P > H₂O–P > NaOH–P. Water-soluble P release of CMA was also determined by kinetic experiments for 120 h. Results showed that total water-soluble P accounted for a maximum of 2.9% of total P in CMA over 120 h due to recalcitrant P compounds formed through incineration. The Fukushima sandy soil amended with CMA at three application rates, 94, 157, and 314 mg P kg^?1 (corresponding to 300, 500, 1000 kg P₂O₅ ha^?1) was incubated for 56 days. Cattle manure compost and KH₂PO₄ were applied at 157 mg P kg^?1 for comparison. Phosphorus release in water and CaCl₂ solution from ash-amended soil was significantly lower than those from compost and KH₂PO₄-amended soil at the same P application rate of 157 mg P kg^?1 (p < 0.05). Available P in ash-amended soil, determined by Fe-oxide impregnated strips, was not significantly different from those in compost-amended soil after day 7 and KH₂PO₄-amended soil on day 56 at the same P application rate. Thus, CMA reduces P losses from soil to the surrounding water while it increases P availability for plants. In comparison of different rates of CMA, P release in water or CaCl₂ was significantly greater at 314 mg P kg^?1 than at 94 or 157 mg P kg^?1, while the percentage of available P to total P was the lowest at the highest application rate (p < 0.05), suggesting that the best application rates were 94 and 157 mg P kg^?1 in this experiment.     

Characterization of nutrients uptake and enzymes activity in Khatouni melon (Cucumis melo var. inodorus) seedlings under different concentrations of nitrogen,potassium and phosphorus of nutrient solution

A nutrient solution experiment was done to evaluate effects of different concentrations of nitrogen (N), phosphorus (P) and potassium (K) on leaf mineral concentrations and some enzymes activity of melon seedlings (Cucumismelo var. inodorus subvar. Khatouni). Different levels of these nutrients including 0, 53, 105, 158 and 210?mg L^?1 N; 0, 8, 16, 23 and 31?mg L^?1 P; 0, 59, 118, 176 and 235?mg L^?1 K, all corresponding to 0, 25, 50, 75 and 100% of their concentrations in Hoagland nutrient solution, were applied to plants. The results showed that the highest leaf nitrate reductase (NR) activity was observed at highest N and P levels, whereas the three highest K levels showed the highest NR activity. The highest leaf peroxidase activity was observed at 8?mg L^?1 P, 59?mg L^?1 K and 158?mg L^?1 N. The leaf catalase activity was highest at zero concentration of P, 158?mg L^?1 N and 176?mg L^?1 K; however, catalase activity was decreased by increasing P levels. Leaf protein content showed an increasing trend with increasing N, P and K levels of nutrient solution, while there was no significant difference between 158 and 210?mg L^?1 N. The highest leaf concentrations of N, P, K and Mg were observed at highest nitrogen, potassium and phosphorus levels of nutrient solution, whereas the highest leaf concentration of Ca were obtained at 53 or 105?mg L^?1 N, 176?mg L^?1 K and 23–31?mg L^?1 P. The highest iron concentration of leaves was obtained from 23 to 31?mg L^?1 P, 176?mg L^?1 K and 210?mg L^?1 N.     

Optimum N and P rates for greenhouse production of vegetative coleus using constant liquid feed

Many new coleus (C. hybridus cv.) cultivars are vegetatively propagated and require different fertilization practices from seed propagated cultivars. Two experiments were conducted to evaluate growth responses of Henna, Indian Summer, Mint Mocha, New Orleans Red, Red Head, and Trusty Rusty to 0, 70, 140, 280 and 420 mg·L^?1 nitrogen (N), and Henna, Mint Mocha, Red Head, and Trusty Rusty to 0, 6.2, 12.4, 24.8, or 49.6 mg·L^?1 phosphorus (P) to determine optimum constant liquid feed rates to produce marketable size plants from rooted cuttings. Positive growth responses in terms of biomass were found with increasing N rates but not P rates. For medium-sized cultivars such as Henna, Indian Summer, and New Orleans Red, quadratic responses were found in aboveground biomass, and N at 280 mg·L^?1 resulted in similar plant size and dry weight as those fertilized at 140 and 420 mg·L^?1 N. For large-sized cultivars such as Mint Mocha, Red Head and Trusty Rusty, plant dry weight responded linearly within the N range tested and were greatest at 420 mg·L^?1. However, plant visual quality was negatively affected by N rates at 280 and 420 mg·L^?1 in that, leaf color became less intense at these high N rates. Plants fertilized at 70 mg·L^?1 were smaller than those fertilized at 140 mg·L^?1, however, they received similar visual quality ratings because of more intense leaf color. Therefore, N at 70 to 140 mg·L^?1 can be used to grow most vegetative coleus for similar marketable quality. Mint Mocha and Henna were the only cultivars responded to P treatments that, 12.4 mg·L^?1 P rate resulted in greater biomass than the no-P control. All other cultivars had no response to supplemental P except a linear response in tissue P%. Therefore, supplemental P is not required during the 8 week production period when there is an initial P charge in the substrate. We found that substrate pH decreases with higher P rates, therefore supplemental P fertilizer can be used for adjusting pH. Both N and P rates found optimum in this study are lower than current industry practices (N at 150 to 250 mg·L^?1 and P at 24 mg·L^?1) and can significantly lower production cost and potential leaching of excessive nutrient into waterway. Nutrient treatments in further study on postharvest performance of vegetative coleus will be selected based on this study.     

Petiole N,P, K Concentrations and Yield of the Potato Cultivar Molli from Certified Organic Amendments and Fertilizer Formulations

This study evaluated the petiole uptake of nitrogen, phosphorus, potassium, and sulfur (N, P, K, and S) by the potato from two seed meals, mint compost, and five commercially available organic fertilizers under an irrigated certified organic production system. Available soil nitrate (NO₃-N) and ammonium (NH₄-N) from each amendment averaged 115 kg N ha^?1 at application and 25 kg N ha^?1 30 d after planting through harvest, with minor differences between fertilizers. Petiole N declined from an average of 25,000 mg N kg^?1, 4 wk after emergence to 3,000 mg N kg^?1 prior to harvest. Petiole P and K concentrations were maintained above 4,000 mg P kg^?1, 10,000 mg K kg^?1, and 2,000 mg S kg^?1 tissue, respectively, throughout the growing season in all treatments. Tuber yields were not different between fertilized treatments averaging 53 Mg ha^?1. This study provides organic potato growers baseline information on the performance of a diverse array of organic fertilizers and amendments.     

Use of soil color meter for aqueous iron and ammonium measurements

Abstract

In this paper, we proposed a new approach for on-site colorimetric analysis of ferrous ions (Fe²⁺) and ammonium-nitrogen (NH₄ ⁺-N) using a soil color meter as an alternative method to conventional spectrophotometry. The soil color meter we used can express solution color numerically on the basis of L*a*b* color space. After coloring of water by the 1, 10 phenanthroline method and the Indophenol blue method, the color of solution was measured by the soil color meter. A linear relationship between Fe²⁺ and a* or b* values, and systematic change of NH₄ ⁺-N with L* value, enable us to make a calibration curve. The Fe²⁺ and NH₄ ⁺-N concentrations in groundwater samples (Fe²⁺: 0.3–1.3 mg L^?1; NH₄ ⁺-N: 0.02–0.62 mg L^?1) determined by the proposed method agreed well with those determined by conventional spectrophotometry with the difference being ± 0.05 mg L^?1 and ± 0.02 mg L^?1, respectively. Since a similar apparatus is widely used in the soil science field, this technique would facilitate field surveys.     

Assessing the impact of phosphorus cycling on river water P concentration in Hokkaido

Abstract

We estimated the phosphorus (P) budgets for all 212 cities, towns and villages of Hokkaido, Japan. We also carried out water sampling from all major rivers flowing in the respective areas during the snowmelt season and measured total P (TP) concentration. Surplus P in the agricultural land was estimated by subtracting the amount of crop uptake from the input sources, such as the amount of chemical and compost fertilizers, crop residues, rainfall and irrigation. The livestock excreta P not utilized on farmland was assumed to be disposed P. Total P concentrations in most of the river water ranged from undetectable to 1 mg L^?1, rarely reaching up to 2.32 mg L^?1, and the areas surrounding the Funka Bay had comparatively higher concentrations. More than two-thirds of the areas had surplus P in farmland ranging from negative values to 30 kg ha^?1 of farmland, and areas with mixed farmland and livestock husbandry had higher surplus values ranging from 31 to 72 kg ha^?1, indicating that the source of the residual P was applied chemical and manure fertilizers. Total P concentration in river water was not correlated with the proportion of upland field and urban area or with the farmland surplus P resulting from the P cycling and the municipal waste P that mixes into the river water. However, TP concentration was positively correlated with the proportion of Andisol area occupied by farmlands (r = 0.25, P < 0.01). The TP concentration was also correlated with the topographic factors in areas (r = 0.49, P < 0.01) that possess more than 50% Andisols in farmlands. Multiple regression analysis showed that TP concentration was best explained by a combination of disposed excreta, the Andisol area occupied by farmland, the application rate of chemical fertilizers and topographic factors (r ² = 0.21, P < 0.001). Thus, P losses from farmlands to river water during the snowmelt season could mainly be attributed to fertilizer management and soil type along with the topographic condition of the area.     

Nutrient dynamics of field-weathered Delmarva poultry litter: implications for land application

To develop phosphorus-based agronomic application rates of phytase-diet, bisulfate-amended Delmarva poultry litter in conservation tillage systems, nutrient release dynamics of the organic fertilizer under local weather conditions were investigated. Delmarva poultry litter was placed in polyvinyl chloride columns to a depth of 5 cm and weathered in the field for 570 days. Leachate from the columns was collected and measured for concentrations of various nutrients. Cumulative release of the nutrients as a function of weathering time was modeled, and the nutrient supply capacity was determined. Poultry litter leachate contained high contents of dissolved organic carbon (15–31,500 mg L^?1), nitrogen (N 5–7,070 mg L^?1), phosphorus (P 5–230 mg L^?1), potassium (K⁺ 2–7,140 mg L^?1), and other nutrients. Release of most nutrients occurred principally in the first 100 days, but for P and calcium (Ca²⁺), it would last for years. The release kinetics of N followed a logarithm equation, while P and K demonstrated a sigmoidal logistic pattern. The nutrient supply capacity of surface-applied Delmarva poultry litter was predicted at 10.9 kg N Mg^?1, 6.5 kg P Mg^?1, 34.7 kg K⁺ Mg^?1, 5.4 kg Ca²⁺ Mg^?1, and 14.0 kg SO ₄ ^2? Mg^?1. The results suggest that Delmarva poultry litter should be applied to conservation tillage systems at 6.6 Mg ha^?1 that would furnish 25 kg P ha^?1 and 63 kg N ha^?1 to seasonal crops. In repeated annual applications, the rate should be reduced to 5.2 Mg ha^?1, with supplemental N fertilization to meet crop N requirements.     

Effects of Swine Lagoon Effluent and Commercial Fertilizer Applications on Phosphorus Status of an Acid and Alkaline Soil

Abstract

Two separate field experiments were conducted to evaluate the effects of swine lagoon effluent relative to inorganic fertilizer at equivalent rates on phosphorus (P) status of an acidic Vaiden (very fine, montmorillonitic, thermic, Aquic Dystrudert) and an alkaline Okolona (fine, montmorillonitic, therimic, Typic Chromudert) silty clay soil. In each site, a randomized complete block design with a factorial arrangement of treatments was used. Treatments were replicated four times. Cumulative swine lagoon effluent P application rates for the year 1994 through 1996 were 0, 59, 121, and 175 kg P ha^?1 on the Vaiden soil and 0, 72, 148, and 223 kg P ha^?1 on the Okolona soil. In each replication, commercial fertilizer P at rates equivalent to swine effluent P application were also included. For both sites, soil P concentration increased with increasing swine effluent and commercial fertilizer P applications. No significant difference in soil P level was observed between two P sources. At high application rate, desorbed P was 1.20 and 0.59 mg P kg^?1 in the Okolona and Vaiden soil respectively. In the Vaiden soil, P adsorption approached the maximum for equilibrium P concentration greater than 600 mg L^?1. However, Okolona soil displayed a linear adsorption potential with application of swine effluent P. Among P fractions, NH4Cl‐P and HCl‐P concentrations increased the most compared to the check in both Okolona and Vaiden soils. Results indicated that P status differs between the soils, but no significant differences in P concentration were obtained between swine lagoon effluent and commercial fertilizer, suggesting that both P sources had similar effect on soil P after 3 years of application.     

Interactive effects of charcoal and earthworm activity increase bioavailable phosphorus in sub-boreal forest soils

The purpose of this study was to assess the effects of charcoal and earthworm presence in contrasting soil types of northern Japan using the biologically based phosphorus (BBP) extraction method, which employs a variety of plant P acquisition strategies. Using soils developed in serpentine and sedimentary parent materials, we tested the interactive effects of Eisenia japonica (Michaelsen) earthworms and 500 kg ha^?1 of dwarf bamboo charcoal (Sasa kurilensis (Rupr.) Makino et Shibata) in a microcosm incubation that lasted four weeks. Soils were extracted in parallel after the incubation with the BBP method using 0.01 M CaCl₂ (soluble P), 0.01 M citric acid (chelate-extractable P), 0.02 phosphatase enzyme units ml^?1 (enzyme-extractable organic P), and 1.0 M HCl (mineral occluded P). Dwarf bamboo charcoal alone contained up to 444 mg total BBP kg^?1 prior to application to soil microcosms. Treatment effects in soil microcosms were highest in sedimentary soil types and where charcoal was combined with earthworms (15.97 mg P kg^?1 ± SE 1.23 total inorganic BBP). Recalcitrant inorganic P (HCl extracted) in combination treatments yielded the highest single inorganic BBP measure (12.41 mg kg^?1 ± SE 1.11). Our findings suggest that charcoal, as a legacy of wildfire, and native earthworm activity may help stimulate cycling of recalcitrant inorganic BBP pools.     

Critical Limit of Extractable Phosphorous in a Gleysol for Rice Production in the Senegal River Valley of West Africa

Abstract

Soil‐test correlation and calibration, a useful tool for fertilizer recommendations, has been little used in West Africa. Soils from a long‐term fertility experiment have been used to study the relationship between rice yields and soil extractable phosphorus (P) with Bray 1 and Olsen methods. The Cate and Nelson graphical method was used for critical limits of soil P determination. The critical limits of soil extractable P at 95% relative grain yield were 9 mg P for the Bray 1P and 17 mg P kg^?1 for Olsen P. The Olsen P was more correlated (r=0.63) with rice grain yields than Bray P (r=0.50), but a strong correlation (r=0.92) was also observed between the values of the two methods. Results indicate that at levels less than these critical levels of extractable P, P fertilizers should be applied to increase rice yields.     

Variable inhibition of iron uptake by oat phytosiderophore in five soybean cultivars

Abstract

Greenhouse experiment was conducted to evaluate the effect of arbuscular mycorrhizal fungi (AMF) on plant growth, and nutrient uptake in saline soils with different salt and phosphorus (P) levels. The following treatments were included in this experiment: (i) Soil A, with salt level of 16.6 dS m^?1 and P level of 8.4 mg kg^?1; (ii) Soil B, with salt level of 6.2 dS m^?1 and P level of 17.5 mg kg^?1; and (iii) Soil C, with salt level of 2.4 dS m^?1 and P level of 6.5 mg kg^?1. Soils received no (control) or 25 mg P kg^?1 soil as triple super phosphate and were either not inoculated (control) or inoculated with a mixture of AM (AM1) and/or with Glomus intraradices (AM2). All pots were amended with 125 mg N kg^?1 soil as ammonium sulfate. Barley (Hordeum vulgar L., cv. “ACSAD 6”) was grown for five weeks. Plants grown on highly saline soils were severely affected where the dry weight was significantly lower than plants growing on moderately and low saline soils. The tiller number and the plant height were also lower under highly saline condition. The reduced plant growth under highly saline soils is mainly attributed to the negative effect of the high osmotic potential of the soil solution of the highly saline soils which tend to reduce the nutrient and water uptake as well as reduce the plant root growth. Both the application of P fertilizers and the soil inoculation with either inoculum mixture or G. intraradices increased the dry weight and the height of the plants but not the tiller number. The positive effect of P application on plant growth was similar to the effect of AM inoculation. Phosphorus concentration in the plants was higher in the mycorrhizal plant compared to the non mycorrhizal ones when P was not added. On the other hand, the addition of P increased the P concentration in the plants of the non mycorrhizal plants to as high as that of the mycorrhizal plants. Iron (Fe) and zinc (Zn) uptake increased with AM inoculation. The addition of P had a positive effect on micronutrient uptake in soil with low level of soil P, but had a negative effect in soil with high level of soil P. Micronutrient uptake decreases with increasing soil salinity level. Inoculation with AMF decreases sodium (Na) concentration in plants grown in soil of the highest salinity level but had no effect when plants were grown in soil with moderate or low salinity level. The potassium (K) concentration was not affected by any treatment while the K/Na ratio was increased by AM inoculation only when plant were grown in soil of the highest salinity level.     

Persistence of CaCl2 washing effect for amelioration of a Cd-contaminated paddy field soil

Abstract

Soil washing is one of the methods used to remediate soil contaminated with heavy metals, and when the contaminated elements have been effectively removed the washed soil can be used for agriculture. Soil washing was conducted using 0.5 mol L^?1 CaCl₂ solution at pH 4 as an extracting agent to remediate a paddy field soil contaminated with Cd. Dolomite powder was applied to neutralize the soil to the original pH 6.2. After CaCl₂ washing, the content of Cd extractable in 0.1 mol L^?1 HCl decreased from 2.4 to 0.8 mg kg^?1. Subsequently, a pot experiment was carried out to evaluate the effect of soil washing on Cd concentration in polished rice (Cd_pr) for three successive years. Using the washed soil, Cd_pr was ≤ 0.2 mg kg^?1 with and without a treatment that simulates midseason drainage, whereas it was > 0.5 mg kg^?1 in the unwashed soil with the midseason drainage treatment. The reasons for low Cd_pr growth in the washed soil were the low content of exchangeable Cd in the soil and the resultant high soil pH (> 7). To evaluate the effect of soil pH on Cd_pr in the fourth year, we adjusted soil pH to 5 with H₂SO₄ before transplanting rice seedlings. The Cd_pr in the washed soil with the midseason drainage treatment increased to 0.47 mg kg^?1, whereas it was less than 0.2 mg kg^?1 under continuous flooding. Thus, high pH or whole season flooding are important to keep Cd_pr at ≤ 0.2 mg kg^?1 even after soil washing. With the application of dolomite and other ordinary fertilizers, soil properties were little affected by the present soil washing procedure because the difference in rice yield between the washed and unwashed plots was not significant within each year.     

Phytoremediation of High-Phosphorus Soil by Annual Ryegrass and Common Bermudagrass Harvest

Removal of soil phosphorus (P) in crop harvest is a remediation option for soils high in P. This 4-year field-plot study determined P uptake by annual ryegrass (ARG, Lolium multiflorum Lam.) and common bermudagrass (CB, Cynodon dactylon (L.) Pers.) from Ruston soil (fine-loamy, siliceous, thermic Typic Paleudult) enriched in P by five previous annual applications of poultry litter, and related P removed to Bray 2 P in surface (0–15 cm) soil. Decreases in surface soil Bray 2 P were largely attributable to uptake. Phosphorus uptake was positively related to Bray 2 P but approached a limit. Mass of P removed in harvest closely approximated the decrease in mass of surface soil Bray 2 P. Maximum Bray 2 P drawdown per harvest (ARG and CB, average) was ?3 mg kg^?1 at Bray 2 P ? 300 mg kg^?1, generally consistent with measured decreases in Bray 2 P.     

Physiological Response of Wheat to Foliar Application of Zinc and Inoculation with some Bacterial Fertilizers

Abstract

In a pot experiment, sterilized sandy soil (irrigated with Long-Ashton nutrient solution containing a half of the recommended dose of ZnSO₄ · 7H₂O) was used to study the effects of zinc (Zn) foliar-application, and soil biofertilization on some physiological traits of wheat (Triticum aestivum cv. Sakha 155) plant grown for 70 days in greenhouse under controlled conditions. The treatments comprised different levels of the foliar applied Zn (0, 25, 50, 100, and 200 mg L^?1) which was added in the form of ZnSO₄ · 7H₂O, and supported by Azotobacter chroococcum (Ar) and/or Azospirillum brasilense (Am) isolates. All test attributes (minerals, photosynthesis, metabolites, and dry matter accumulation) were significantly enhanced by the moderate doses of Zn (25 and 50 mg L^?1), while a contrary trend was observed in case of the higher levels (100 and 200 mg L^?1). Applying the bacterial fertilizers (Ar, Am) to the experimental soil, influenced the most test characters in the direction of improving growth, photosynthesis and dry matter accumulation by the plant. This response was more evident in the case of applying Ar plus Am than Am than Ar, particularly, at the elevated levels of Zn. Zinc application at 50 mg L^?1 supported by the biofertilization with Ar plus Am resulted in the highest shoot contents of nitrogen (N), magnesium (Mg), manganese (Mn), carbohydrate and total-soluble proteins. Superior values of the photosynthetic criteria (Chl a + b concentration and photosystem II activity) as well as shoot concentration of indole-3-acetic acid, and dry matter accumulation by shoots and roots were obtained by the same treatment. The highest phosphorus (P) concentration was achieved at 25 mg L^?1 Zn supported by Ar plus Am. Irrespective of the bacterial inoculum, shoot contents of potassium (K) and Zn showed a positive correlation with the sprayed dose of Zn.     

Soil‐Applied Selenium Effects on Tissue Selenium Concentrations in Cultivated and Adventitious Grassland and Pasture Plant Species

Abstract

According to international nutritional standards, plant selenium (Se) concentrations in Belgium are too low. To correct this situation, adding Se in fertilizers for pastures and grasslands is suggested, similar to activities in Finland. However, there is a lack of data on meadow plant species' ability to absorb Se. Therefore, a pot experiment was initiated using 24 meadow plant species cultivated on a Belgian cambisol receiving standard fertilizer treatment, with or without the addition of 9 g Se ha^?1 yr^?1 as sodium selenate. Soil Se analysis confirmed the low Se status of the native soil. Mean foliar Se concentration in the control group was 0.05 mg kg^?1. Because plant deficiency may occur at levels less than 0.10 mg Se kg^?1, data provided further evidence for Se deficiency in Belgium plant production. When grown with Se, plant species showed wide variations for Se concentration, ranging from 0.08 to 0.49 mg Se kg^?1. All values were less than 2 mg Se kg^?1, the suggested threshold toxicity level for dairy cattle. There were two different types of plants in terms of response to Se fertilization. Most of the tested plants were known as nonaccumulators. There were also two probable secondary accumulators: Sinapis arvensis and Melilotus albus. Finally, one has to question the reliability of plant Se enhancement using this method when floristic composition is poorly controlled.     

Variation in Yield,Phosphorus Uptake,and Physiological Efficiency of Wheat Genotypes at Adequate and Stress Phosphorus Levels in Soil

Genetic differences among crop genotypes can be exploited for identification of genotypes more suited to a low‐input agricultural system. Twenty wheat (Triticum aestivum L.) genotypes were evaluated for their differential yield response, phosphorus (P) uptake in grain and straw, and P‐use efficiency at the zero‐P control and 52 kg P ha^?1 rates. Substantial and significant differences were obvious among genotypes for both grain and straw yields at stress (8 mg P kg^?1 soil, native soil P, no P addition) and adequate (52 kg P ha^?1) P levels. Genotype 5039 produced maximum grain yield at both P levels. Relative reduction in grain yield due to P‐deficiency stress [i.e., P stress factor (PSF)] ranged between none and 32.4%, indicating differential P requirement of these genotypes. Pasban 90, Pitic 62, Rohtas 90, Punjab 85, and line 4943 did not respond to P application and exhibited high relative yield compared to those at adequate P level. FSD 83 exhibited the best response to P with maximum value for PSF (32.4%). Genotypes were distributed into nine groups on the basis of relationship between grain yield and total P uptake. Rohtas 90 and lines 4072 and 5039 exhibited high grain yield and medium P uptake (HGY‐MP). However, line 5039 with high total index score utilized less P (12.2 kg P ha^?1) than line 4072 and Rohtas 90 (13.5 and 13.6 kg P ha^?1, respectively). Moreover, this genotype also had greater P harvest index (PHI, %) and P physiological efficiency index (PPEI) at stress P level. Pasban 90, Pitic 62, and Pak 81 had the greatest total index score (21), mainly due to high total P uptake, but yielded less grain than lines 5039 and 4072 under low available P conditions. Line 6142 had minimum total index score (15) and also produced minimum grain yield. A wide range of significant differences in PPEI (211 to 365 kg grain kg^?1 P absorbed at stress and 206 to 325 kg grain kg^?1 P absorbed by aboveground plant material at adequate P) indicated differential utilization of absorbed P by these genotypes for grain production at both P levels. It is concluded from the results that wheat genotypes differed considerably in terms of their P requirements for growth and response to P application. The findings suggest that PSF, PHI, and PPEI parameters could be useful to determine P‐deficiency stress tolerance in wheat.