EFFECTS OF ELEMENTAL SULFUR AND MYCORRHIZAE ON THE YIELD OF WHEAT IN DIFFERENT SOILS

Yield responses of wheat (Triticum aestivum L.) to elemental sulfur (S), mycorrhizae (mycorrhizal fungus, Glomus mosseae), and phosphorus (P) alone and collectively in two different soils were investigated. Plants were grown on calcareous sterilized Karaburun and Menek?e soils (sub-group of Typic Xerorthent). In the all treatments mycorrhizae inoculation alone compared to the control treatment increased shoot and root yields. The yield responses to S alone, P alone, and combined application of S and P in mycorrhizal and non-mycorrhizal treatments in two different soils were interestingly fluctuating. The findings obtained in this study indicated that S tended to increase the efficiency of mycorrhizae in the well aerated Karaburun soil in comparison to a less aerated (heavier textured) Menek?e soil. This potential to increase the efficiency of mycorrhizae on the root growth indicate that yield increase of shoot and grain can occur being an important finding for ecological agriculture.     

Effect of Phosphorus in Alleviation of Adverse Impacts of Salinity on Wheat Grown on Different Soils

Fertilization management is an important technique to alleviate the adverse effects of salinity stress on plants. A pot experiment was conducted to evaluate the ameliorative role of inorganic phosphorus (P) and organic P sources on wheat grown under salt stress in three soil types deficient in available P. Wheat (Triticum asetivum L. cv. Shakha 93) was grown on alluvial, sandy, and calcareous soils under salinity levels of 4, 8, and 12 dS m^?1 of saturated paste extract (EC_e) and supplied with constant rate of 30 mg P₂O₅ kg soil^?1 as superphosphate (SP), cattle manure (CM), and 1:1 mixture of SP and CM. The results revealed that plants grown on the sandy soil were more susceptible to the adverse effects of salinity compared with those planted on the alluvial one, especially at zero P. Plants grown on the calcareous soil were moderately affected. Varying soil type caused significant differences in the aboveground biomass and uptake of nitrogen (N), potassium (K), P, and zinc (Zn). It was obvious that P ameliorated wheat growth under salt stress, and this role was greater under moderate and high salinity. The increases in N, P, K, and Zn uptake appeared driven by P application were more conspicuous in the sandy and calcareous soils. Results also indicated that combined application of inorganic and organic P sources surpassed both when applied solely under all soil types and salinity levels.     

Interaction of Iron with Copper,Zinc, and Manganese in Wheat as Affected by Iron and Manganese in a Calcareous Soil

Iron (Fe) availability is low in calcareous soils of southern Iran. The chelate Fe-ethylenediamine di (o-hydroxy-phenylacetic acid) (Fe-EDDHA), has been used as an effective source of Fe in correcting Fe deficiency in such soils. In some cases, however, its application might cause nutritional disorder due to the antagonistic effect of Fe with other cationic micronutrients, in particular with manganese (Mn). A greenhouse experiment was conducted to evaluate the influence of soil and foliar applications of Fe and soil application of manganese (Mn) on dry matter yield (DMY) and the uptake of cationic micronutrients in wheat (Triticum aestivum L. var. Ghods) in a calcareous soil. Results showed that neither soil application of Fe-EDDHA nor foliar application of Fe sulfate had a significant effect on wheat DMY. In general, Fe application increased Fe uptake but decreased that of Mn, zinc (Zn), and copper (Cu). Application of Mn increased only Mn uptake and had no significant effect on the uptake of the other cationic micronutrients. Iron treatments considerably increased the ratio of Fe to Mn, Zn, Cu, and (Mn + Zn + Cu). Failure to observe an increase in wheat DMY following Fe application is attributed to the antagonistic effect of Fe with Mn, Zn, and Cu and hence, imbalance in Fe to (Mn + Zn + Cu) ratio. Due to the nutritional disorder and imbalance, it appears that neither soil application of Fe-EDDHA nor foliar application of Fe-sulfate is appropriate in correcting Fe deficiency in wheat grown on calcareous soils. Hence, growing Fe-efficient wheat cultivars should be considered as an appropriate practice for Fe chlorosis-prone calcareous soils of southern Iran.     

Interaction of salinity,nitrogen, and phosphorus fertilization on wheat

This study determined whether the application of nitrogen (N) and phosphorus (P) could ameliorate salt‐induced reduction in wheat production. Saline irrigation water (0.5, 4.0, 8.2, and 12.5 dS/m) and N and P fertilizers (150 kg N/ha and 37.5 kg P₂O₅/ha) were applied to wheat (Triticum aestivum L. ‘Saka 92') grown on a calcareous soil in a greenhouse experiment. Plants received equal amounts of each fertilizer, but the time and frequency of application differed. All salinity levels reduced straw and grain yields, leaf soluble proteins, nitrate (NO₃) content, actual and potential nitrate reductase activity (NRA), and grain protein content. The delay in pollen meiotic cell division increased with salinity. Under saline conditions, applying N and P fertilizers at the end of the grain filling stage improved yield and metabolic performance of the plants compared to other fertilizer treatments.     

Phosphorus-induced zinc deficiency in wheat pot-grown on noncalcareous and calcareous soils of different properties

High levels of phosphorus (P) often induce zinc (Zn) deficiency in plants grown on Zn-poor soils. We investigated P-induced Zn deficiency in durum wheat (Triticum durum L. ‘Carpio’) grown on 16 noncalcareous and 31 calcareous soils differing in levels of available (Olsen) P and available (diethylenetriaminepentaacetic acid (DTPA)-extractable) Zn using micropots. A completely randomized factorial design with two levels of P (0 and 40 mg P kg^?1 soil) and Zn (0 and 3 mg Zn kg^?1 soil), i.e. four treatments (‘control’, + P, + Zn, and + PZn), were used. Grain yield of control plants depended mainly on the Olsen P level. Phosphorus had a negative effect on yield in 6 soils with Olsen P/Zn_DTPA > 25, and Zn a positive one in 5 soils with Olsen P/Zn_DTPA > 50; and the + PZn treatment generally resulted in the highest yield. Grain Zn concentration of control plants was negatively correlated with growth and Olsen P. Calcareous soils were less sensitive to P-induced Zn deficiency than noncalcareous soils because phosphate is sorbed by calcite rather than being co-adsorbed with Zn on the Fe oxides. Co-application of P and Zn to soil at low and application of Zn at high Olsen P ensured both maximum yield and grain Zn bioavailability.     

Variation in zinc efficiency among and within Aegilops species

Fifteen accessions of Aegilops tauschii (DD), 10 of Ae. speltoides (SS) and 8 of the tetraploid Aegilops species sharing the U genome were used to study the influence of varied zinc (Zn) supply on development of Zn-deficiency symptoms, and on shoot dry weight and Zn concentration. Plants were grown in a Zn-deficient calcareous soil under greenhouse conditions with (+Zn = 5 mg kg^—1 soil) and without (—Zn) Zn supply. Four accessions of wild tetraploid wheat, Triticum turgidum var. dicoccoides (BBAA), a group known for its high sensitivity to Zn-deficiency, were used in the experiments for comparison. As expected, the accessions of wild T. turgidum var. dicoccoides showed the highest sensitivity to Zn deficiency, and had more severe leaf symptoms of Zn deficiency (whitish-brown necrotic patches). Among the Aegilops species, leaf symptoms of Zn deficiency were, in general, more distinct in Ae. tauschii (DD) and least in Ae. speltoides (SS). Zinc efficiency, expressed as the percentage of shoot dry weight produced under conditions of Zn deficiency compared to Zn supply, averaged, 15% for T. turgidum, 32% for Ae. tauschii, 52% for Ae. speltoides and 61% for the tetraploid Aegilops species carrying the U genome. Differences in Zn efficiency among and within Aegilops species and T. turgidum were significantly correlated with the Zn amount per shoot, but not with the Zn amount per unit dry weight of shoots. The results show that Aegilops species can be exploited as an important genetic source for Zn efficiency genes, particularly Ae. speltoides var. ligustica (SS) and Ae. triuncialis (UUCC). Transfer of these genes to cultivated modern wheat may bring about a greater variation in Zn efficiency in wheat, and facilitate production of Zn-efficient modern wheat cultivars for Zn-deficient soil conditions.     

Source and mode of sulphur application on groundnut productivity

The effectiveness of 20 kg/ha sulphur (S) of the S‐containing compounds iron sulphate (FeSO₄), gypsum, phosphogypsum, elemental S, and pyrite on groundnut (Arachis hypogaea L.) productivity was determined for plants grown on calcareous soil in the field. Plants grown with S compared to those without S had increased plant height, number of flowers, nodule numbers and weight, higher dry matter, seed, haulm (leaves and stems), and oil yields; higher tissue concentrations of nitrogen (N), phosphorus (P), S, iron (Fe), and zinc (Zn); and higher total uptake of mineral nutrients. Elemental S, pyrite, and FeSO₄ were more effective than gypsum and phosphogypsum, with FeSO₄ being the most effective source of S for improving plant growth traits, yield, and nutrient uptake. The most effective method of FeSO₄ application was half to the soil at planting time (basal) followed by the remainder in three equal foliar sprays at 30,50, and 70 days after plant emergence (DAE). Pyrite and elemental S were most effective when applied to the soil only, half as a basal soil dressing, and the remainder in two equal doses at 25 and 50 DAE. Plant concentrations of S, P, and potassium (K) were similar for each source of S, but elemental S, pyrite, and FeSO₄ enhanced N, Fe, manganese (Mn), and Zn uptake. Gypsum and phosphogypsum enhanced calcium (Ca) uptake. Elemental S and FeSCM provided similar results when half was applied to the soil followed by three equal foliar sprays. The best results from pyrite, gypsum, and phosphogypsum were obtained when soil applied.     

Effect of different zinc application methods on grain yield and zinc concentration in wheat cultivars grown on zinc‐deficient calcareous soils

The effect of six different zinc (Zn) application methods on grain yield and concentrations of Zn in whole shoots and grain was studied in wheat cultivars (Triticum aestivum, L. cvs. Gerek‐79, Dagdas‐94 and Bezostaja‐1 and Triticum durum, Desf. cv. Kunduru‐1149) grown on severely Zn‐deficient calcareous soils (DTPA‐extractable Zn: 0.12 mg‐kg^‐1 soil) of Central Anatolia which is the major wheat growing area of Turkey. Zinc application methods tested were: a) control (no Zn application), b) soil, c) seed, d) leaf, e) soil+leaf, and f) seed+leaf applications. Irrespective of the method, application of Zn significantly increased grain yield in all cultivars. Compared to the control, increases in grain yield were about 260% with soil, soil+leaf, and seed+leaf, 204% with seed and 124% with leaf application of Zn. In a similar manner, biomass production (dry weight of above‐ground parts) was increased by Zn treatments. The highest increase (109%) was obtained with the soil application and the lowest increase (40%) with the leaf application. Significant effects of Zn application methods were also found on the yield components, i.e., spike number.m^‐2, grain number‐spike^‐1, and thousand kernel weight. Spike number.m^‐2 was affected most by Zn applications, particularly by soil and soil+leaf applications. Concentrations of Zn in whole shoots and grain were greatly affected by different Zn treatments. In plants without added Zn, concentrations of Zn were about 10 mg‐kg^‐1 both in shoots and grain and increased to 18 mg‐kg^‐1 dry weight (DW) by soil application of Zn, but not affected by seed application of Zn. Soil+leaf application of Zn had the highest increase in concentration of Zn in shoot (82 mg‐kg^‐1 DW) and grain (38 mg‐kg^‐1 DW). Soil application of Zn was economical and had long‐term effects for enhancing grain yield of wheat grown on Zn deficient soils. When high grain yield and high Zn concentration in grains are desired, soil+leaf application of Zn was most effective method of Zn application.     

Influence of Gyttja on Shoot Growth and Shoot Concentrations of Zinc and Boron of Wheat Cultivars Grown on Zinc‐Deficient and Boron‐Toxic Soil

Abstract

Greenhouse experiments were carried out to study the influence of gyttja, a sedimentary peat, on the shoot dry weight and shoot concentrations of zinc (Zn) and boron (B) in one bread wheat (Triticum aestivum L., cv. Bezostaja) and one durum wheat (Triticum durum L., cv. Kiziltan) cultivar. Plants were grown in a Zn‐deficient (DTPA‐Zn: 0.09 mg kg^?1 soil) and B‐toxic soil (CaCl₂/mannitol‐extractable B: 10.5 mg kg^?1 soil) with (+Zn = 5 mg Zn kg^?1 soil) and without (?Zn = 0) Zn supply for 55 days. Gyttja containing 545 g kg^?1 organic matter was applied to the soil at the rates of 0, 1, 2.5, 5, and 10% (w/w). When Zn and gyttja were not added, plants showed leaf symptoms of Zn deficiency and B toxicity, and had a reduced growth. With increased rates of gyttja application, shoot growth of both cultivars was significantly enhanced under Zn deficiency, but not at sufficient supply of Zn. The adverse effects of Zn deficiency and B toxicity on shoot dry matter production became very minimal at the highest rate of gyttja application. Increases in gyttja application significantly enhanced shoot concentrations of Zn in plants grown without addition of inorganic Zn. In Zn‐sufficient plants, the gyttja application up to 5% (w/w) did not affect Zn concentration in shoots, but at the highest rate of gyttja application there was a clear decrease in shoot Zn concentration. Irrespective of Zn supply, the gyttja application strongly decreased shoot concentration of B in plants, particularly in durum wheat. For example, in Zn‐deficient Kiziltan shoot concentration of B was reduced from 385 mg kg^?1 to 214 mg kg^?1 with an increased gyttja application. The results obtained indicate that gyttja is a useful organic material improving Zn nutrition of plants in Zn‐deficient soils and alleviating adverse effects of B toxicity on plant growth. The beneficial effects of gyttja on plant growth in the Zn‐deficient and B‐toxic soil were discussed in terms of increases in plant available concentration of Zn in soil and reduction of B uptake due to formation of tightly bound complexes of B with gyttja.     

Diagnosis of zinc and boron availability in emerging vegetable‐based crop rotations in Nepal

Background : Nepal's traditional rice–wheat rotation systems are subject to continuing changes. Changing consumer demand currently drives a replacement of wheat by high‐value vegetables during the dry season, while emerging water shortages lead to a substitution of rice by maize in the wet season. Hence, associated changes in soil aeration status and shifting conditions of soil nutrient supply to match crop nutrient demand are expected to increase the requirements for the principle limiting micro‐nutrients such as boron (B) and zinc (Zn). Aim: Our aim was to investigate the changes in B and Zn availability as well as crop yields and nutrient uptake after system shifts from rice to maize and from wheat to vegetables. Method : We analyzed the B and Zn availability in rice‐ and maize‐based systems as well as crop yields and the nutrient uptake by wheat, cauliflower, and tomato during the dry season in Nepal. Plants were grown at two field sites (midhills vs. lowland) and under greenhouse conditions using soils from the field sites. Results : A change from irrigated rice to maize reduced soil C and N contents with resulting decreases in dry season crop yields. Low soil Zn after rice cultivation led to shortage in Zn uptake by vegetables in both greenhouse and field experiments. The shift from wheat to vegetables increased the demand for B and to a lesser extent for Zn, and consequently vegetables showed visual symptoms of B deficiency. Boron concentrations in dry biomass were below the critical limits with < 10 mg B kg^?1 in wheat, < 21 mg B kg^?1 in cauliflower, and < 23 mg B kg^?1 in tomato. Conclusions: Soils in larger parts of Nepal are low in available B and that the ongoing system shifts increase in the demand for B and Zn in the currently emerging and more diversified production systems.     

High rates of domestic sewage sludge on a calcareous soil and their effect on wheat growth using a pot experiment

A pot experiment was carried out to explore the use of high loading rates of domestic sewage sludge from Jeresh (Jordan) on a calcareous soil. Sludge was mixed with soil in volume ratios of 1:8, 1:6, 1:4, 1:2, 1:1, 2:1, and 4:1 with the unamended soil as a control. Wheat (Triticum durum L.) was grown in the pots for 60 days. The addition of sludge at a ratio of 1:8 increased wheat growth significantly; 1:6 ratio resulted in better growth than the control, although the increase was not significant at the 5% probability level. Other ratios suppressed wheat growth. The analysis of sludge-soil mixtures indicated that the addition of sludge increased the extractable P, K, Fe, Zn, Mn, and Cu in the mixtures. The addition of sludge to soil increased N and P in wheat tissue to optimum levels, but decreased K content. Iron and Zinc increased in wheat tissue due to the addition of sludge to soil, however Mn and Cu were not much affected.     

Varietal tolerance to Zinc deficiency in wheat and barley grown in chelatorbuffered nutrient solution and its effect on uptake of Cu,Fe, and Mn

Tolerance to zinc (Zn) deficiency was examined for three wheat (Triticum aestivum L.) and three barley (Hordeum vulgare L.) varieties grown in chelator‐buffered nutrient solution. Four indices were chosen to characterize tolerance to Zn deficiency: (1) relative shoot weight at low compared to high Zn supply (“Zn efficiency index”), (2) relative shoot to root ratio at low compared to high Zn supply, (3) total shoot uptake of Zn under deficient conditions, and (4) shoot dry weight under deficient conditions. Barley and wheat exhibited different tolerance to Zn deficiency, with barley being consistently more tolerant than wheat as assessed by all four indices. The tolerance to Zn deficiency in the barley varieties was in the order Thule=Tyra>Kinnan, and that of wheat in the order Bastian=Avle>Vinjett. The less tolerant varieties of both species accumulated more P in the shoots than the more tolerant varieties. For all varieties, the concentrations of Mn, Fe, Cu, and P in shoot tissue were negatively correlated with Zn supply. This antagonism was more pronounced for Mn and P than for Cu and Fe. Accumulation of Cu in barley roots was extremely high under Zn‐deficient conditions, an effect not so clearly indicated in wheat.     

The effectiveness of seed priming with synthetic zinc-amino acid chelates in comparison with soil-applied ZnSO4 in improving yield and zinc availability of wheat grain

The effect of soil applied zinc (Zn) sulfate and seed priming with Zn-glutamine [Zn(Gln)₂], Zn-glycine [Zn(Gly)₂], Zn-arginine [Zn(Arg)₂], and Zn-histidine [Zn(His)₂] on yield and grain nutritional quality of two bread (Triticum aestivum L. cvs. Back Cross and Kavir) and a durum wheat genotype (Triticum durum L. cv. Durum) was investigated. Seed priming with [Zn(Gly)₂] and [Zn(Gln)₂] increased grain yield of wheat over soil applied Zn-sulfate treatment by 46 and 14%, respectively. Seed priming with [Zn(Gln)₂], [Zn(Arg)₂], and [Zn(His)₂] significantly increased grain protein content of wheat in comparison with control treatment. Seed priming with [Zn(Arg)₂] and [Zn(His)₂] resulted in higher Zn and Fe accumulation in wheat grain as compared with the other Zn treatments. Priming seeds with [Zn(Arg)₂] reduced phytic acid to Zn molar ratio of wheat grain. Seed priming with [Zn(Arg)₂] and [Zn(His)₂] might be used as an alternative approach for soil application of Zn-sulfate to overcome Zn deficiency in calcareous soils.     

Responses of Wheat Genotypes to Zinc Fertilization Under Saline Soil Conditions

ABSTRACT

A greenhouse experiment with four bread wheat [Triticum aestivum L.] genotypes, ‘Rushan,’ ‘Kavir,’ ‘Cross,’ and ‘Falat,’ and a durum wheat [Triticum durum L.] genotype, ‘Dur-3,’ at two zinc (Zn) rates (0 and 15 mg Zn kg^?1 dry soil) and four salinity levels (0, 60, 120, and 180 mM NaCl) was conducted. After 45 d of growth, the shoots were harvested, and Zn, iron (Fe), potassium (K), sodium (Na), and cadmium (Cd) concentrations were determined. In the absence of added Zn, visual Zn deficiency symptoms were observed to be more severe in ‘Dur-3’ and ‘Kavir’ than in other genotypes. The effect of Zn deficiency on shoot dry matter was similar to its effect on visual deficiency symptoms, such that shoot growth was most depressed in ‘Kavir’ and ‘Dur-3.’ At the 180 mM treatment, Zn fertilization had no effect on shoot dry matter of genotypes. Genotypes with high Zn efficiency had greater shoot Zn content than genotypes with low Zn efficiency. In the absence of added Zn, the Dur-3, and ‘Cross’ genotypes had the highest and lowest Cd concentrations, respectively. Application of Zn had a positive effect on salt tolerance of plants.     

Uptake of Microelements by Crops Grown on Heavy Metal–Amended Soil

Abstract

A small‐plot field experiment on microelement pollution (Aluminum (Al), Arsenic (As), Cadmium (Cd), Chromium (Cr), Copper (Cu), Mercury (Hg), Lead (Pb), Zinc (Zn)) was initiated in 1994 at Tass‐puszta Model Farm of Gyöngyös College, Hungary. The experimental plants were winter wheat (Triticum aestivum L. emend. Fiori et Pool.) in 1995, maize (Zea mays L.) in 1996, and sunflower (Helianthus annuus L.) in 1997. Plant samples were taken each year during the vegetation period at phenophases characterized by intensive nutrient uptake. The Al content of crops was not influenced by Al load of the soil. Arsenic accumulation was not considerable in the grain with the highest As load. Cadmium accumulation was significant both in vegetative and reproductive parts of crops with increasing Cd loads of the soil. The Cd content was about 10–40 times higher in treated sunflower seeds than in the control; as a result the seeds were not suitable for consumption. Cadmium can accumulate in the reproductive tissue, so it is a real risk in the food chain. In the first year, Cr(VI) had a toxic effect on wheat, but it was not mobile in the soil–plant system. Vegetative parts of winter wheat accumulated significant amounts of Hg, but maize and sunflower seeds did not accumulate Hg. Lead, Cu, and Zn showed only moderate enrichment in crops following increasing loads in the soil.     

Zinc fertilization in rice-wheat cropping system under upland calcareous soil

Zinc (Zn) fertilization is important for Zn crop biofortification as well as increasing yields, thus proper Zn recommendations for soil application is needed for Zn deficient soils. The effectiveness of Zn applications was evaluated in different combinations of rates (2.5, 5.0, 7.5, and 10.0?kg?ha^?1 per year) and frequencies (initial, alternate, and every year) in rice (Oriza sativa L.) – wheat (Triticum aestivum L.) cropping system in a Zn-deficient upland calcareous soil in the fourth year. Zn applications to rice at 7.5 and 10?kg?ha^?1 of alternate year and 5.0 to 10?kg?ha^?1 of every year had the highest rice equivalent yield as compared to no-Zn treatment. Hence, Zn application to rice at 7.5?kg?ha^?1 at alternate years is the lowest rate at which highest rice equivalent yield of rice-wheat cropping system can be obtained.     

Effect of Zinc Humate on Growth of Soybean and Wheat in Zinc‐Deficient Calcareous Soil

Abstract

Humic acids have many benefits for plant growth and development, and these effects may be maximized if these materials are combined with micronutrient applications. In the present study, pot experiments were conducted to evaluate the effects of zinc (Zn) humate and ZnSO₄ on growth of wheat and soybean in a severely Zn‐deficient calcareous soil (DTPA‐Zn: 0.10 mg kg^?1 soil). Plants were grown for 24 (wheat) and 28 days (soybean) with 0 or 5 mg kg^?1 of Zn as either ZnSO₄ or Zn humate. Zinc humate used in the experiments was obtained from Humintech GmbH, Germany, and contained 5% of Zn. When Zn was not supplied, plants rapidly developed visible symptoms of Zn deficiency (e.g., chlorosis and brown patches on young leaves in soybean and necrotic patches on middle‐aged leaves in wheat). Adding Zn humate eliminated Zn‐deficiency symptoms and enhanced dry matter production by 50% in soybean and 120% in wheat. Zinc‐humate and ZnSO₄ were similarly effective in increasing dry matter production in wheat; but Zn humate increased soybean dry matter more than ZnSO₄. When Zn was not supplied, Zn concentrations were 6 mg kg^?1 for wheat and 8 mg kg^?1 for soybean. Application of Zn humate and ZnSO₄ increased shoot Zn concentration of plants to 36 and 34 mg kg^?1 in wheat and to 13 and 18 mg kg^?1 in soybean, respectively. The results indicate that soybean and wheat plants can efficiently utilize Zn chelated to humic acid in calcareous soils, and this utilization is comparable to the utilization of Zn from ZnSO₄. Under Zn‐deficient soil conditions, plant growth and yield can be maximized by the combined positive effects of Zn and humic acids.     

Effect of one phosphorus rate placed in different soil volumes on p uptake and growth of wheat

Abstract

The volume of soil treated with P fertilizer affects P uptake by the crop. Earlier studies have shown that the stimulation of root growth in P‐fertilized soil was similar for both corn (Zea mays L.) and soybean (Glycine max L. Merr). The objective of this research was to determine the effect of fertilizer P placement on P uptake and shoot and root growth of spring wheat (Triticum vulgare L.). Wheat was grown for 34 days in Raub silt loam (Aquic Argiudolls) in a controlled climate chamber. One rate of phosphate per pot, 150 mg P per three kg of soil, was mixed with 2, 5, 10, 20, 40 and 100% of the soil in the pot. The P was equilibrated with moist soil for 5 days at 70°C followed by 21 days at 25° C before transplanting 8‐day‐old wheat plants into each 3 L pot. The P stimulation of root growth in the P‐treated soil was similar to that for corn and soybeans. The effect could be described by the equation y = x^0.7 where y is the fraction of the root system in the P‐fertilized soil where P is mixed with x fraction of the soil. The greatest P uptake and plant growth occurred when added P was mixed with 20% of the soil.     

Effects of sulfur application and Thiobacillus inoculation on soil nutrient availability,wheat yield and plant nutrient concentration in calcareous soils with different calcium carbonate content

In this research, elemental sulfur was applied at eight rates with and without Thiobacillus inoculation in calcareous soils which had 23%, 17% and 8.5% Total Neutralizing Value(TNV). The highest grain yield, biological yield, plant height, and concentrations of iron (Fe) and zinc (Zn) in shoot were obtained with application of S⁰ at rates which neutralized 2% and 4% of soil TNV, while highest available nutrients and plant-phosphorus (P) were recorded with application of S⁰ at rates which neutralized 16% and 20% of soil TNV. Maximum indices were recorded in soil which had 17% TNV, so that available P, Fe and zinc (Zn) increased by 167.33%, 35.67% and 81.70% compared with control respectively with application of 9.14 g S° g^?1soil. Thiobacillus inoculation increased all of indices (except Fe concentration) compared with non-inoculated control. The results reveal that sulfur application along with Thiobacillus can increase nutrients availability, nutrients uptake and yield of wheat grown in calcareous soils.     

Phosphorus Influx and Root‐Shoot Relations as Indicators of Phosphorus Efficiency of Different Crops

Abstract

The large variation in phosphorus acquisition efficiency of different crops provides opportunities for screening crop species that perform well on low phosphorus (P) soil. To explain the differences in P efficiency of winter maize (Zea mays L.), wheat (Triticum aestivum L.), and chickpea (Cicer arietinum L.), a green house pot experiment was conducted by using P‐deficient Typic ustochrept loamy sand soil (0.5 M NaHCO₃‐extractable P 4.9 mg kg^?1, pH 7.5, and organic carbon 2.7 g kg^?1) treated with 0, 30, and 60 mg P kg^?1 soil. Under P deficiency conditions, winter maize produced 76% of its maximum shoot dry weight (SDW) with 0.2% P in shoot, whereas chickpea and wheat produced about 30% of their maximum SDW with more than 0.25% P in shoot. Root length (RL) of winter maize, wheat, and chickpea were 83, 48, and 19% of their maximum RL, respectively. Considering relative shoot yield as a measure of efficiency, winter maize was more P efficient than wheat and chickpea. Winter maize had lower RL/SDW ratio than that of wheat, but it was more P efficient because it could maintain 2.2 times higher P influx even under P deficiency conditions. In addition, winter maize had low internal P requirement and 3.3 times higher shoot demand (i.e., higher amount of shoot produced per cm of root per second). Even though chickpea had 1.2 times higher P influx than winter maize, it was less P efficient because of few roots (i.e., less RL per unit SDW). Nutrient uptake model (NST 3.0) calculations satisfactorily predicted P influxes by all the three crops under sufficient P supply conditions (C_Li 48 µM), and the calculated values of P influx were 81–99% of the measured values. However, in no‐P treatment (C_Li 3.9 µM), under prediction of measured P influx indicated the importance of root exudates and/or mycorrhizae that increase P solubility in the rhizosphere. Sensitivity analysis showed that in low P soils, the initial soil solution P concentration (C_Li) was the most sensitive factor controlling P influx in all the three crops.