囊泡丛枝菌根促进石灰性土壤小麦的P、Zn吸收及转移

Vesicular-arbuscular mycorrhizal(VMA) fungi have been credited with improving the growth and mineral nutritons of many host plants but these effects are moderated by soil factors and nutrient balance.The combined effects of VAM,Zn and P application on the growth and translocation of nutrients in wheat were investigated using a calcareous soil marginal in P and Zn concentrations.Wheat was grown in a growth chamber under various combinations of VAM,P and Zn with measurements done at heading stage and maturity,Vegetative dry matter accumlation was increased by P application and reduced by VAM treatments.Both P and VAM increased grain yield.Zince oncentration and uptake were generally reduced by P addition and VAM infection,There were no antagonistic effects of Zn on P acquisition in the plant,The role of VAM in enhancing the translocation of Zn and P from root to grain would be beneficial to seed setting and yield.     

Relationships between sulfur concentration in mulberry Leaves and the quality of silkworm cocoon

A 40-day gnotobiotic microcosm experiment was carried out to quantify the effect of bacterial-feeding nematode on plat growth and nutrient absorption.The results showed that inoculation of bacterial-feeding nematode Protorhabditis sp.stimulated the growth of wheat (Triticum aestivum) and the uptake of N.By the end of the 40-day incubation wheat biomass and N uptake in the treatment with nematode and bacteria (Pseudomonas sp.)increased by 6.5% and 5.9%,respectively,compared with bacteria alone treatment.The presence of nematode mainly accelerated the growth of aboveground of wheat,while it slightly inhibited the root development.There was little difference in plant tissue N concentration between treatments.P concentration and uptake of wheat,however,were generally reduced by nematode, It appears that the enhancement of plant growth and nitrogen uptake is attributed to the enhancement of nitrogen mineraliztion induced by nematode feeding on bacteria,and the reduction of phosphorous uptake is the result of ewak root status and comptetition by bacteria immobilzation.     

树木年轮中养分元素含量的角分布及其环境信息

The effects of nitrogen,phosphorus and potassium application level,seed rate and transplanting density on the growth and development of rice plants were studied to find out nutrient status in high-yielding rice plants and to increase grain yield by adequate fertilization.There was an equilibrium relationship among nutrient elements for high-yielding rice plant populations.The equilibrium index of nutrient amount ,content and distribution in high-yielding rice plants should be generally greater than-2 but less than 2.The optimum nutritive proportion of nitrogen:phosphorus:potassium assimilated by the plants was about 10:2:9 at the ripening stage.But the content and the proportion varied with the growth stages,Therefore,the nutrient in rice plant populations should be in a dynamic equilibrium.So as to achieve high yield.     

接种食细菌线虫对小麦生长和N、P吸收的影响

A 40-day gnotobiotic microcosm experiment was carried out to quantify the effect of bacterial-feeding nematode on plant growth and nutrient absorption. The results showed that inoculation of bacterial-feeding nematode Protorhabditis sp. stimulated the growth of wheat (Triticum aestivum) and the uptake of N. By the end of the 40-day incubation wheat biomass and N uptake in the treatment with nematode and bacteria (Pseudomonas sp.) increased by 6.5% and 5.9%, respectively, compared with bacteria alone treatment. The presence of nematode mainly accelerated the growth of aboveground of wheat, while it slightly inhibited the root development. There was little difference in plant tissue N concentration between treatments. P concentration and uptake of wheat, however, were generally reduced by nematode. It appears that the enhancement of plant growth and nitrogen uptake is attributed to the enhancement of nitrogen mineralization induced by nematode feeding on bacteria, and the reduction of phosphorous uptake is the result of weak root status and competition by bacteria immobilization.     

在富营养土壤斑块中根增值对玉米养分吸收和生长的贡献

Root proliferation can be stimulated in a heterogeneous nutrient patch; however, the functions of the root proliferation in the nutrient-rich soil patches are not fully understood. In the present study, a two-year field experiment was conducted to examine the comparative effects of localized application of ammonium and phosphorus (P) at early or late stages on root growth, nutrient uptake, and biomass of maize (Zea mays L.) on a calcareous soil in an intensive farming system. Localized supply of ammonium and P had a more evident effect on shoot and root growth, and especially stimulated fine root development at the early seedling stage, with most of the maize roots being allocated to the nutrient-rich patch in the topsoil. Although localized ammonium and P supply at the late stage also enhanced the fine root growth, the plant roots in the patch accounted for a low proportion of the whole maize roots in the topsoil at the flowering stage. Compared with the early stage, fine root length in the short-lived nutrient patch decreased by 44%-62% and the shoot dry weight was not different between heterogeneous and homogeneous nutrient supply at the late growth stage. Localized supply of ammonium and P significantly increased N and P accumulation by maize at 35 and 47 days after sowing (DAS); however, no significant difference was found among the treatments at 82 DAS and the later growth stages. The increased nutrient uptake and plant growth was related to the higher proportion of root length in the localized nutrient-enriched patch. The results indicated that root proliferation in nutrient patches contributed more to maize growth and nutrient uptake at the early than late stages.     

聚合果属生物炭引起的咸水灌溉下土壤养分有效性和番茄生长变化

Thermally modified organic materials commonly known as biochar have gained popularity of being used as a soil amendment.Little information, however, is available on the role of biochar in alleviating the negative impacts of saline water on soil productivity and plant growth. This study, therefore, was conducted to investigate the effects of Conocarpus biochar(BC) and organic farm residues(FR) at different application rates of 0.0%(control), 4.0% and 8.0%(weight/weight) on yield and quality of tomatoes grown on a sandy soil under drip irrigation with saline or non-saline water. The availability of P, K, Fe, Mn, Zn and Cu to plants was also investigated. The results demonstrated clearly that addition of BC or FR increased the vegetative growth, yield and quality parameters in all irrigation treatments. It was found that salt stress adversely affected soil productivity, as indicated by the lower vegetative growth and yield components of tomato plants. However, this suppressing effect on the vegetative growth and yield tended to decline with application of FR or BC, especially at the high application rate and in the presence of biochar. Under saline irrigation system, for instance, the total tomato yield increased over the control by 14.0%–43.3% with BC and by 3.9%–35.6% with FR. These could be attributed to enhancement effects of FR or BC on soil properties, as indicated by increases in soil organic matter content and nutrient availability. Therefore, biochar may be effectively used as a soil amendment for enhancing the productivity of salt-affected sandy soils under arid conditions.     

盐条件下产胞外多糖植物促生细菌研究

Salt-tolerant plant growth-promoting rhizobacteria (PGPR) can play an important role in alleviating soil salinity stress during plant growth and bacterial exopolysaccharide (EPS) can also help to mitigate salinity stress by reducing the content of Na + available for plant uptake.In this study,native bacterial strains of wheat rhizosphere in soils of Varanasi,India,were screened to identify the EPS-producing salt-tolerant rhizobacteria with plant growth-promoting traits.The various rhizobacteria strains were isolated and identified using 16S rDNA sequencing.The plant growth-promoting effect of inoculation of seedlings with these bacterial strains was evaluated under soil salinity conditions in a pot experiment.Eleven bacterial strains which initially showed tolerance up to 80 g L -1 NaCl also exhibited an EPS-producing potential.The results suggested that the isolated bacterial strains demonstrated some of the plant growth-promoting traits such as phosphate solubilizing ability and production of auxin,proline,reducing sugars,and total soluble sugars.Furthermore,the inoculated wheat plants had an increased biomass compared to the un-inoculated plants.     

土壤－水分－植物体系中铅和镉的交互作用及其机制: Ⅱ. 根际中Pb-Cd的交互作用

The interaction of Pb-Cd can be observed not only in the uptake process of elements by plants and in their influence on the growth,but also in rhizosphere.The changes in extractable Cd and Pb concentrations in the rhizosphere soil of rice plants ,root exudates from wheat and wheat plant and their complexing capacity,with Pa and Cd were investigated under different Pb and Cd treatments.Results showed that the concentration of extractable Cd in the rhizosphere of rice in red soil was markedly increased by Pb-Cd interaction,It increased by 56% in the treatment with Pb and Cd added against that in the treatment with only Cd added in soil . The considerable differences in both composition and amount of root exudate from wheat and rice were found among different treatments.Pb and Cd might be complexed by root exudates ,The concentrations of free Pb and Cd in the solution were increased markedly by adding root exudate from wheat and decreased by that from rice due to Pd-Cd interaction.The distribution patterns of Pb and Cd in roots were affected by Pb-Cd interaction,which accelerated transport of Pb into internal tissue and retarded accumulation of Cd in external tissue.     

Mycorrhizal Symbioses of Cotton Grown on Sodic Soils:A Review from an Australian Perspective

The majority of terrestrial plants form some type of mycorrhizal symbiosis.This established symbiosis therefore exists in most commercially important crops, which includes cotton.Arbuscular mycorrhizal fungus(AMF) can colonise 50%–90% of cotton root length under field and controlled conditions.Mycorrhization improves growth and nutrient uptake(especially phosphorus) of cotton,particularly at the early growth stages.Mycorrhizal symbioses help plants to counter the stresses imposed by physical and chemical soil constraints; however, adverse environmental conditions may restrict the mycorrhizal associations and consequently may reduce nutrient uptake and impair plant growth.In Australia, cotton is mainly grown on sodic soils that contain more than 6% of the total cations as exchangeable sodium.High levels of sodium in the soil create adverse physical and chemical soil conditions that may negatively affect mycorrhizal symbioses of cotton.This review discusses the cotton mycorrhizal colonisation, plant growth, and disease protection effects, potential negative effects of physical and chemical properties of sodic soils, and influences of some agronomic management practices.In addition, the research gaps were identified and some practical applications of the research outcomes were suggested.     

栽培方法对穗直立型稻株养分含量的影响

Field experiments were carried out with rice variety of Shennong 91 of short culms and erect panicles to study nutrient contents in high-yielding rice plants and to increase rice yield by appropriate fertilization. Nitrogen, phosphorus, potassium, magnesium, zinc, manganese, iron and copper contents in rice plants varied with different treatment factors. The relationship between the nutrient contents and treatment factors could be simulated using a multiple quadratic equation. The nutrient contents in plants should be appropriate for high-yielding rice. If the mean nutrient content in rice plants producing 11 t ha^-1 or more of grain (μ_j) was set as the standard value and the standard deviation (σ_j) was set as the range of variation, the nutrient content in high-yielding rice plants should be μ_j ± 1.99σ_j. Rice leaves were sensitive to the nutrient elements. Heavy nitrogen dressing increased the content of nitrogen in rice plants. Sparse transplanting also increased nitrogen content. Improper application of nitrogen, phosphorus and potassium could affect the nutrient contents and decrease the grain yield.     

High monosilicic acid supply rapidly increases Na accumulation in maize roots by decreasing external Ca2+ activity

Both calcium (Ca²⁺) and silicon (Si) improve plant performance under salt (NaCl) stress. Although these two mineral elements share numerous similarities, the information on how their extracellular interactions in the root apoplast affect uptake of sodium (Na⁺) is still lacking. Here, we investigated the effect of high Si supply in the bioavailable form of monosilicic acid (H₄SiO₄) on the activity of Ca²⁺ in the external root solution, and subsequent root uptake and compartmentation of Na in maize (Zea mays L.). In the short‐term experiments (6 h), 14‐d‐old maize plants were exposed to various concentrations of Ca²⁺ at three different pH‐values (6.5, 7.5, and 8.5) and two Si concentrations, i.e., low (1 mM) and high (4 mM) supply of H₄SiO₄. The activity of Ca²⁺ and Na⁺ in the external solution as well as the root concentrations of total and cell sap and BaCl₂‐exchangeble apoplastic fractions of both elements were analyzed. The pH of the nutrient solution affected neither the ion activities nor the root accumulation of both Ca²⁺ and Na⁺. At higher pH values (7.5 and 8.5) the interactions of Ca²⁺ and Si at high Si supply led to a decrease of Ca²⁺ activity and, hence, an increase of Na⁺ : Ca²⁺ activity ratio in the external root solution. Concomitantly, despite the elevated exchangeable apoplastic fraction of both Ca²⁺ and Na⁺, the total and cell sap concentrations were remarkably decreased for Ca²⁺ and increased for Na⁺ by the addition of 4 mM H₄SiO₄. This work demonstrates that at high Si supply extracellular Ca‐Si interactions leading to lowered activity of Ca²⁺ might rapidly compromise the ameliorative effect of Ca²⁺ on Na⁺ accumulation in roots. Practically, Si over‐fertilization of saline and, in particular, sodic soils may further promote the accumulation of Na⁺ in root tissues hours after Si application and, hence, increase a potential risk of Na⁺ toxicity.     

Foliar calcium spray confers drought stress tolerance in maize via modulation of plant growth,water relations,proline content and hydrogen peroxide activity

Water and nutrient restrictions are the factors that limiting growth of maize in arid/semi-arid climate. Calcium (Ca²⁺) uptake is affected severely under drought stress (DS). The objectives of this study were to investigate the effects of DS and foliar applied Ca²⁺ on growth, physiological, biochemical, yield and grain-nutrient content in two maize cultivars i.e. drought-tolerantDekalb-6525 and drought-sensitive Yousafwala-hybrid. The study comprised of two phases; firstly the best rate of Ca²⁺ (20, 40 and 60 mg L?1) was evaluated. Secondly, optimized rate of Ca²⁺ (40 mg L?1) was used to assess physio-biochemical and yield responses of maize under DS. The applied DS caused significant reduction in maize growth, water-status, photosynthesis and grain nutrient contents. Foliar Ca²⁺ markedly improved plant growth, water-potential (18%), turgor-potential (75%), photosynthesis (45%), stomatal-conductance (47%), transpiration rate (43%) and accumulation of total soluble sugars (20%) along with decline in H2O2 content (23%) in both cultivars under DS. Furthermore, optimized rate of Ca²⁺ improved maize grain yield and quality under water-deficit conditions. Cultivar Dekalb-6525 presented significant response to Ca²⁺ over Yousafwala-hybrid. Results of the study surmise that foliar supply of Ca²⁺ is an effective approach to make plants vigorous to thrive under limited-water supply.     

WHEAT GENOTYPES DIFFERED SIGNIFICANTLY IN THEIR RESPONSE TO SILICON NUTRITION UNDER SALINITY STRESS

We studied the growth and ionic composition of five wheat genotypes (Inqlab-91, Uqab 2002, SARC-1, SARC-3, and SARC-5) grown under salinity stress to applied silicon. Plants were grown with three levels of salinity [0, 60, and 120 mM sodium chloride (NaCl)] in the presence of 0, 2, and 4 mM Si in nutrient solution for 40 days. Salinity stress significantly decreased shoot and root biomass in plants with varying degrees. Genotype SARC-3 exhibited higher salt tolerance than other genotypes. Silicon (Si) application significantly (P < 0.05) increased plant biomass at both control as well as under saline conditions. Genotypes differed significantly for their response to applied Si in terms of biomass production. Silicon application significantly (P < 0.01) increased potassium (K⁺) concentration in shoots. Enhanced salinity tolerance in wheat by Si application was attributed to increased K⁺ uptake thereby increasing K⁺/sodium (Na⁺) ratio and lower Na⁺ translocation towards shoot.     

Effects of water and exogenous Si on element concentrations and ecological stoichiometry of plantain (Plantago lanceolata L.)

Silicon (Si) is widely distributed in nature and can promote plant growth under various biotic and abiotic stresses. Drought stress seriously affects plant growth and the concentration and ecological stoichiometry of nutrients. Integrated nutrient management effectively protects plants from stresses. However, the role of water and Si availability on element concentrations and stoichiometry in plantain (Plantago lanceolata L.) are unclear. Accordingly, this study observed changes in the concentration and stoichiometry of macro- and micro-elements in plantain leaves supplied with various levels of Si under variable water availabilities through a greenhouse experiment. Supplemental Si increased Si concentration of leaves under both well-watered and drought conditions. Without supplemental Si, drought conditions decreased concentrations of carbon (C), C: nitrogen (N), C: phosphorus (P), silicon (Si):N, Si:P and increased concentrations of N, P, N:P, Si:C, calcium (Ca²⁺), magnesium (Mg²⁺), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu). Increased Si under water stress increased concentrations of C, C:N, C:P, Si:C, Si:N, and Si:P, and decreased concentrations of Ca²⁺, sodium (Na⁺), and Mg²⁺. These results suggested that exogenous Si changed the concentrations and ecological stoichiometry of macro- and micro-elements.     

Nitrogen and Sulfur Effects on Macro- and Micronutrient Contents in Canola (Brassica napus L.) Grown on Acidic Soils of the Western Cape Province of South Africa

Soil pH and nutrient contents influence the uptake and utilization of nutrients required for plant growth. Soil characteristics in the canola-growing areas of the Western Cape Province of South Africa are often very variable. Hence, the major aim of this research was to determine the effects of soil and climatic differences as experienced at different localities on macro- and micronutrient contents and uptake in canola plants fertilized with different nitrogen (N) and sulfur (S) application rates. Plants fertilized with 0, 15, and 30 kg S ha^?1 in combination with N rates of 0 and 90 kg ha^?1 were sampled at 90 days after planting (DAP) (flowering stage) at Altona, Elsenburg, Langgewens, Roodebloem, and Welgevallen localities in the Western Cape during 2009 2010, and 2011. Nutrient content in canola plants were affected by locality and interactions between locality and N application rates. Sulfur content within the plants remained less than the sufficient quantity of 0.5%, and a dilution effect on elemental concentration in canola especially at greater N rates (plus lack of sufficient S) is apparently evident from the results. The results also reveal that canola S application should match S adsorption capacity of the low pH soils of the Western Cape.     

Impact of a biochar or a biochar-compost mixture on water relation, nutrient uptake and photosynthesis of Phragmites karka

Soil water and nutrient status are both of major importance for plant appearance and growth performance. The objective of this study was to understand the effect of biochar (1.5%) and a biochar-compost mixture (1.5% biochar + 1.5% compost) on the performance of Phragmites karka plants grown on a synthetic nutrient-poor sandy clay soil (50% sand, 30% clay, and 20% gravel). Indicators of plant performance, such as growth, lignocellulosic biomass, water status (leaf water potential, osmotic potential, and turgor potential), mineral nutrition status, leaf gas exchange, and chlorophyll fluorescence, and soil respiration (carbon dioxide (CO₂) flux) were assessed under greenhouse conditions. Biochar-treated plants had higher growth rates and lignocellulosic biomass production than control plants with no biochar and no compost. There was also a significant increase in soil respiration in the treatments with biochar, which stimulated microbial interactions. The increase in soil water-holding capacity after biochar amendment caused significant improvements in plant water status and plant ion (K⁺, Mg²⁺, and Ca²⁺) contents, leading to an increase in net photosynthesis and a higher energy-use efficiency of photosystem II. Biochar-treated plants had lower oxidative stress, increased water-use efficiency, and decreased soil respiration, and the biochar-compost mixture resulted in even greater improvements in growth, leaf turgor potential, photosynthesis, nutrient content, and soil gas exchange. Our results suggest that biochar and compost promote plant growth with respect to nutrient uptake, water balance, and photosynthetic system efficiency. In summary, both the soil amendments studied could increase opportunities for P. karka to sequester CO₂ and produce more fodder bio-active compounds and biomass for bio-energy on nutrient-poor degraded soils.     

WHEAT RESPONSE TO NITROGEN SOURCE UNDER SALINE CONDITIONS

ABSTRACT

The influence of nitrogen (N) sources on biomass yield and nutrient uptake of wheat (Triticum aestivum L.) under saline conditions was studied in a greenhouse experiment. Six different forms of N {nitrate-N as Ca(NO₃)₂, urea-N [CO(NH₂)₂], ammonium-N as (NH₄)₂SO₄, nitrate-N+urea-N, nitrate-N+ammonium-N and a control (no N fertilizer)} were factorially combined with three levels of salinity to give a total of 18 treatments that were replicated three times. Each of the five levels of applied N was at the rate of 100?kg?ha^?1. The salinity levels (ECe) were 6.2 and 12.1?dSm^?1, denoted as S ₁ and S ₂ and untreated soil (S ₀), respectively. A basal dose of phosphorus (P) and potassium (K) was also applied. Five wheat plants were grown in each pot for six weeks. Data were collected for shoot and root biomass and shoot samples were analyzed for N, P, K, calcium (Ca), magnesium (Mg), sodium (Na), chloride (Cl), and micronutrients contents. Plant growth and nutrient uptake were influenced by both salinity and source of N. As expected, increasing salinity decreased dry matter production of shoot and root, whereas N application increased plant growth across all levels of salinity. The total dry biomass (shoot and root) of wheat was significantly higher in combined N treatments than in single sources. Irrespective of N forms most of the nutrient concentrations in the shoot was increased with increasing level of salinity. Among the fertilizers the concentration of cation was higher in nitrate-treated plants than in other forms of N. Ammonium-N and urea-N tended to inhibit the uptake of cations compared to nitrate-N under saline conditions. The trend for P and Cl concentration was almost opposite to that of cations concentration in the shoot. The uptake of nutrients seemed to be influenced by cation–anion balance in soil-plant system. Nitrogen concentration of shoot was greatly enhanced by all forms of N in the following order: Ni>NiAm>Am>NiUr>Ur>control. The interactive effect of salinity and fertilizer on iron (Fe), manganese (Mn), and zinc (Zn) contents was not consistent. Among the fertilizers the concentration of trace elements in the shoot was also not significantly different. It was concluded that the plant growth and nutrient concentration of shoot could depend upon N source and level of salinity. The mixed application of both ammoniacal and nitrate forms of N could possibly be conducive to plant growth in salt affected soils.     

Effect of Exogenous Silicon on Ion Distribution of Tomato Plants Under Salt Stress

Seedlings of two tomato cultivars were exposed to 0, 50, or 100 mM sodium chlroide (NaCl) stress with or without silicon (Si) for 10 days, and leaf electrolyte leakage, root activity, plant growth, and ion sodium, potassium, calcium, and magnesium (Na⁺, K⁺, Ca²⁺, and Mg²⁺) contents were determined. No significant differences were observed in total biomass and the root/crown ratio of salt-stressed plants treated with exogenous Si, but leaf electrolyte leakage of both cultivars treated with 50 mM NaCl and Si was lower than that in the same salt treatment without Si. Root activities of both cultivars were significantly affected by treatment with NaCl and exogenous Si. Application of Si induced a significant decrease in Na⁺ content and increases in K⁺, Ca²⁺, and Mg²⁺ contents in leaves of plants treated with 50 mM NaCl, and consequently the K⁺/Na⁺ and Ca²⁺/Na⁺ ratios increased by at least two times. The effects of Si on the ion contents of the roots were not notable.     

Calcium and humic acid affect seed germination,growth, and nutrient content of tomato (Lycopersicon esculentum L.) seedlings under saline soil conditions

The effects of calcium and humic acid on seed germination, growth and macro- and micro-nutrient contents of tomato (Lycopersicon esculentum L.) seedlings in saline soil conditions were evaluated. Different levels of humic acid (0, 500, 1000 and 2000 mg kg^?1) and calcium (0, 100, 200 and 400 mg kg^?1) were applied to growth media treated with 50 mg NaCl kg^?1 before sowing seeds. Seed germination, hypocotyl length, cotyledon width and length, root size, shoot length, leaf number, shoot and root fresh weights, and shoot and root dry weights of the plant seedlings were determined. Macro- and micro-nutrient (N, P, K, Ca, Mg, S, Cu, Fe, Mn and Zn) contents of shoot and root of seedlings were also measured. Humic acid applied to the plant growth medium at 1000 mg kg^?1 concentration increased seedling growth and nutrient contents of plants. Humic acid not only increased macro-nutrient contents, but also enhanced micro-nutrient contents of plant organs. However, high levels of humic acid arrested plant growth or decreased nutrient contents. Levels of 100 and 200 mg kg^?1 Ca²⁺ application significantly increased N, Ca and S contents of shoot, and N and K contents of root.     

Silicon mitigates boron deficiency and toxicity in cotton cultivated in nutrient solution

Silicon (Si) application, both via foliar application and via roots, may be promising to improve plant growth under different biotic or abiotic stresses. In the present study, we investigated whether application of Si can also mitigate the harmful effects of boron (B)‐related nutritional disorders, such as B deficiency, when the application of B is inefficient or insufficient, and B toxicity, when the soil presents high levels of B. This may enable producers to apply Si preventively, if there is a low availability of B in the environment or if B deficiency is induced during the growth season due to a water deficit reducing the plant's B absorption. The objective of this study was to investigate the influence of leaf and root Si application on alleviating the harmful effects of B deficiency and toxicity in cotton. Three experiments were carried out with cotton plants (Gossypium hirsutum cv. Bayer FM910®), using a soilless system. In a first experiment, we determined that highest plant Si concentrations were obtained with application of stabilized sodium and potassium silicate at concentrations of 0.8 g L^?1 (foliar) and 0.056 g L^?1 (roots). Experiment 2 indicated that the B concentrations in the nutrient solution associated with moderate B deficiency, sufficiency and moderate toxicity were 33.7, 83.6, and 130.5 µM B L^?1, respectively. In Experiment 3 we evaluated the effect of optimum Si applications on the physiology and dry weight production of cotton plants subjected to B deficiency, sufficiency, and toxicity. Silicon mitigated the harmful effects of both B deficiency and toxicity by increasing whole‐plant biomass production and levels of chlorophyll a, chlorophyll b, and total chlorophyll, and reduced initial and maximum fluorescence, thereby improving the quantum efficiency of photosystem II. Collectively, these results indicate that the greatest benefit of Si in mitigating B deficiency occurred with foliar B application, while Si supplied via the nutrient solution was more effective against B toxicity.