Nitrogen Contribution of Peanut Residue to Cotton in a Conservation Tillage System

ABSTRACT

Leguminous crops, particularly winter annuals, have been utilized in conservation systems to partially meet nitrogen (N) requirements of succeeding summer cash crops. Previous research also highlights the benefits of utilizing summer annual legumes in rotation with non-leguminous crops. This study assessed the N contribution of peanut (Arachis hypogaea L.) residues to a subsequent cotton (Gossypium hirsitum L.) crop in a conservation system on a Dothan sandy loam (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) at Headland, AL during the 2003–2005 growing seasons. Treatments were arranged in a split plot design, with main plots of peanut residue retained or removed from the soil surface, and subplots as N application rates (0, 34, 67, and 101 kg ha^{? 1}) applied in fall and spring. Peanut residue did not influence seed cotton yields, leaf N concentrations, or plant N uptake for either growth stage or year of the experiment. There was a trend for peanut residue to increase whole plant biomass measured at the first square in two of three years. Seed cotton yields and plant parameters measured at the first square and mid-bloom responded favorably to spring N applications, but the recommended 101 kg N ha^{? 1} did not maximize yields. The results from this study indicate that peanut residue does not contribute significant amounts of N to a succeeding cotton crop, however, retaining residue on the soil surface provides other benefits to soils in the southeastern U.S.     

小麦和玉米中后期大量元素叶面施用的生物效应

采用盆载和田间小区试验了小麦和玉米叶面１０ｇ／Ｌ尿素、１０ｇ／ＬＫＨ２ＰＯ２和５．４ｇ／ＬＫＣｌ及其配合用一些生理效应,叶面施用尿素,尤其是Ｎ、Ｐ和Ｋ的配合施用可显著延缓两种作物在拔节后其根系活力的下降,叶面追肥增强职责上作物功能叶的生理活性,在Ｎ,Ｋ或Ｐ＋Ｋ三者之间,尿素的效果较佳。三者的配合施用是最大限度延长叶珠措施,作物后期喷尿素＋ＫＨ２ＰＯ４能显著增加小麦和玉米的籽粒产量。叶面施用Ｎ、Ｐ、     

Absorption and translocation of foliar applied triazone‐n as compared to other nitrogen sources in tomato

Absorption and translocation of foliar applied ¹⁵N labeled S‐tetrahydrotriazone (triazone), as compared to other N forms, was evaluated in tomato plants. Triazone‐N was taken up into leaf tissue in quantities similar to urea, ammonium, and nitrate‐N when applied at a N concentration of 0.35% w/v. Although >40% of the ¹⁵N label was exported from the treated leaf after 7 days, nearly 50% of the translocated triazone ¹⁵N label accumulated in non‐treated leaf tissue as compared to only 10% or less for the other N sources. The largest percentage of the translocated urea‐, ammonium‐, and nitrate‐¹⁵N label accumulated within developing fruit tissue. Multiple (3) foliar applications of triazone and urea at concentrations of 0.94% or higher and 1.0% N (w/v), respectively, enhanced both leaf and fruit tissue N concentrations. No growth responses to foliar applied N were observed.     

Effects of early‐season foliar fertilization on cotton growth,yield, and nutrient concentration

Many producers are using foliar fertilizers on seedling cotton (Gossypium hirsutum L.) with the intent of promoting early vigor and increasing yields. However, the hypothesis that foliar feeding young cotton increases seedling vigor and yield has not been rigorously tested. We conducted 5 studies during 1990 to 1992 to investigate the value of one, two or three foliar applications of 12–48–8 fertilizer to seedling cotton. Two studies also included foliar‐applied urea. Plant height and whole‐plant phosphorous (P) and nitrogen (N) were determined two weeks after each application in two studies. Yield and P and N concentrations were not influenced by foliar fertilizers in any study. Seedling height was not influenced by applications of 12–48–8. A slight early‐season height advantage was observed with foliar‐applied urea at one location. Our results suggest that application of foliar N and P fertilizers to seedling cotton has little agronomic value.     

Potassium fertilization of cotton on two high testing soils under two tillage systems

Potassium (K) fertilization of cotton (Gossypium hirsutum L.) has been a major research focus the last few years throughout the cotton belt. The objective of this field research, conducted from 1991 through 1994 on two high Mehlich I extractable K (EK) soils, was to evaluate broadcast and foliar applied K for conventional‐ (CT) and no‐tillage (NT) production. Main plot broadcast K rates were 0, 28, 56, and 112 kg K ha^‐1. Foliar sub‐plot treatments were a non‐foliar check, KNO₃, and Ca(NO₃)₂. The KNO₃ was applied four times per year at 4.1 kg K ha^‐1 application^‐1. Calcium nitrate was applied at 1.6 kg N ha^‐1 to equal the N applied in the KNO₃. Extractable K increased annually with broadcast K for both tillage systems and soils and was higher for NT than CT. Lint yields from CT of both soils were increased two of the eight site‐years while yields from NT were increased five of eight site‐years by broadcast K. Three of the NT site‐year yields plus four‐year mean yields of both soils were increased by applying 56 kg K ha^‐1, a rate higher than currently recommended for high EK soils. Yield responses to foliar fertilization were from added N rather than the K. Petiole K levels were sufficient so that extra K applied foliarly was not recommended for either soil or tillage system.     

Effects of autumn foliar application of 15n‐urea on nitrogen storage and reuse in apple 1

Effects of autumn foliar application of N‐urea on N storage and reuse in young apple seedling (Malus Pumila Mill.) were studied. Foliar application of urea^‐15 N (3.5%) during autumn enhanced the retranslocation of leaf N to other plant parts and increased stored N. Foliar N sprays increased the proteolytic activities of the leaves; therefore, such activities appear to be a major mechanism of retranslocation of leaf N. Foliar applied N enabled the plant to produce more growth during the following seasons. A considerable portion of the plant total N during second and third years was attributable to the foliarly applied N during the first year.     

Interaction of 15N-labelled ammonium nitrate,urea and ammonium sulphate with soil N during growth of wheat (Triticum aestivum L.) under field conditions

The effects of ¹⁵N-labelled ammonium nitrate, urea and ammonium sulphate on yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L. cv. Mexi-Pak-65) were studied in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 64.0–74.8%, 61.5–64.7% and 61.7–63.4% of the N from ammonium nitrate, urea and ammonium sulphate, respectively. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea and ammonium sulphate. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the three N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied with the method of application of fertilizer N. Ammonium nitrate, urea and ammonium sulphate gave 59.3%, 42.8% and 26.3% more added N interaction, respectively, when applied by the broadcast/worked-in method than with band placement. A highly significant correlation between soil N and grain yield, dry matter and added N interaction showed that soil N was more important than fertilizer N in wheat production. A values were not significantly correlated with added N interaction (r=0.719). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N stood proxy for unlabelled soil N.     

INFLUENCE OF FOLIAR FERTILIZATION AND GROWTH REGULATOR ON MILK THISTLE SEED YIELD AND QUALITY

The effects of foliar fertilization and a growth regulator 5-tert-butyl-N-m-tolylpyrazine-2-carboxamide (MD148/II) on the growth, seed yield, and silymarin content of milk thistle (Silybum marianum Gaertn.) plants were evaluated. The study was conducted over two years at an experimental field on a slightly acid-leached cinnamonic meadow soil. The MD148/II was applied in the beginning of milk thistle flowering stage. Foliar fertilizer was applied at different plant developmental stages with different proportions of nitrogen (N), phosphorus (P), and potassium (K). Treatments with foliar fertilizer and MD148/II resulted in improvement of plant biomass, number of plant lateral shoots, flowering rate, and seed yield and the content of some active substances in milk thistle seeds. A reduction of high molecular fatty acids was observed. The increase of seed yield was a result of the flower head setting enhancement. Therefore the combined treatment of foliar fertilizer and MD148/II was efficient in elicitation milk thistle production under field conditions.     

Effect of Foliar Application of Phosphorus on Winter Wheat Grain Yield,Phosphorus Uptake,and Use Efficiency

ABSTRACT

One would expect foliar applied phosphorus (P) to have higher use efficiencies than when applied to the soil, but limited information is available concerning this. Experiments were conducted in 2002, 2003, and 2004 to determine the effect of foliar applications of P on winter wheat grain yields, P uptake, and use efficiency. Twelve treatments containing varying foliar P rates (0, 1, 2, and 4 kg ha^{? 1} in 2002 and 2003 and additional 8, 12, 16, and 20 kg ha^{? 1} in 2004) with and without pre-plant rates of 30 kg ha^{? 1} were evaluated. Foliar applications of P at Feekes 7 generally increased grain yields and P uptake versus no foliar P. Use efficiency was higher when P was applied at Feekes 10.54. Results from this study suggested that low rates of foliar applied P might correct mid-season P deficiency in winter wheat, and that might result in higher P use efficiencies.     

Effects of 15N-labelled ammonium nitrate and urea on soil nitrogen during growth of wheat (Triticum aestivum L.) under field conditions

We studied the effects of ¹⁵N-labelled ammonium nitrate and urea on the yield and uptake of labelled and unlabelled N by wheat (Triticum aestivum L., cv. Mexi-Pak-65) in a field experiment. The dry matter and N yields were significantly increased with fertilizer N application compared to those from unfertilized soil. The wheat crop used 33.6–51.5 and 30.5–40.9% of the N from ammonium nitrate and urea, respectively. Splitting the fertilizer N application had a significant effect on the uptake of fertilizer N by the wheat. The fertilizer N uptake showed that ammonium nitrate was a more available source of N for wheat than urea. The effective use of fertilizer N (ratio of fertilizer N in grain to fertilizer N in whole plant) was statistically similar for the two N fertilizers. The application of fertilizer N increased the uptake of unlabelled soil N by wheat, a result attributed to a positive added N interaction, which varied according to the fertilizer N split; six split applications gave the highest added N interaction compared to a single application or two split applications for both fertilizers. Ammonium nitrate gave 90.5, 33.5, and 48.5% more added N interaction than urea with one, two, and six split N applications. A values were not significantly correlated with the added N interaction (r=0.557). The observed added N interaction may have been the result of pool substitution, whereby added labelled fertilizer N replaced unlabelled soil N.     

Influence of Foliar and Ground Fertilization on Yield,Fruit Quality,and Soil,Leaf, and Fruit Mineral Nutrients in Apple

ABSTRACT

The effectiveness of nitrogen (N)+ zinc (Zn) soil and foliar fertilizer applications on growth, yield, and quality of apple (Malus domestic Borkh ‘Golden Delicious’) fruit was studied in the Zanjan province, Iran. There were eight treatments 1) control (no fertilizer), 2) soil applied N, 3) soil applied Zn, 4) soil applied N+Zn, 5) foliar applied N, 6) foliar applied Zn, 7) foliar applied N+Zn and 8) combined soil and foliar applied N+Zn. The N source was urea [CO(NH₂)₂, 46% N] applied at 276 N tree^{? 1} yr^?1 and the Zn source was zinc sulfate (ZnSO₄,7H₂0, 23% Zn) applied at 110 g Zn tree^{? 1} yr^{? 1}. The soil treatments of N and Zn, were applied every two weeks during June through August (total of 6 times/year) in a 1 m radius around the tree trunk (drip line of trees). The foliar solutions of N (10 g l^{? 1} urea) and Zn [8 g l^{? 1} zinc sulfate (ZnSO₄)] were sprayed at the rate of 10 L tree^{? 1} every two weeks at the same times as described for soil applications. The highest yield (49 kg tree^{? 1}), and the heaviest fruits (202 g) were obtained in the soil and foliar combination of N+Zn treatment. The lowest yield (35 kg tree^{? 1}), and the smallest fruits (175 g) were recorded in the control. Nitrogen, and to a lesser extent Zn, foliar application resulted in decreasing fruit quality (caused russeting, and lower soluble solid), but increasing N leaf and fruit concentrations (2.4% DW and 563 mg kg^{? 1}, respectively). There were significant differences among yield and leaf mineral nutrient concentration in different treatments. But there was no significant difference between fruit mineral nutrient concentration (except N). Ratio of N/calcium (Ca), potassium (K)/Ca, and [magnesium (Mg)+K]/Ca in fruits were found suitable for fruit quality prediction. Combining the zinc sulfate with urea in the foliar applications increased the concentration of Zn from 0.7 to 1.5 mg per kg of apple tissue. Leaf N concentration varied during growth season. Foliar applied nutrient can be more efficient than soil applied, but a combination of soil and foliar applications is recommended for apple tree nutrient management.     

Enhancement of Growth and Yield of Rice (Oryza Sativa) by Plant Probiotic Endophyte,Lysinibacillus sphaericus under Greenhouse Conditions

ABSTRACT

Nitrogen (N) is the “prime” among the three major nutrients required for plant growth. The large potential demand of nitrogen for plant growth is mainly achieved through biological nitrogen fixation. We have attempted to study the growth enhancement of rice crop under greenhouse conditions using the endophytic diazotrophic bacteria Lysinibacillus sphaericus. The effect of inoculation of L. sphaericus on yield and nutrient uptake was studied. All the parameters studied showed significantly higher values than that obtained in uninoculated absolute control. The highest yield was given by treatment T7 (seed and foliar) followed by T9 (soil and foliar) and T5 (seed and soil) and were statistically at par. The highest dry weight of grains was found to be in treatment T2 (13.0 g^?1plant) which received soil treatment of L. sphaericus followed by T9 (12.2 g^?1plant) which received combined application of L. sphaericus as soil and foliar treatment. It can be deduced from the results, there is a high influence of endophytic bacteria L. sphaericus in plant growth despite the mode of inoculation. This establishes the potential of diazotrophic endophyte L. sphaericus to limit the use of industrial N fertilizers thereby enhancing the fertility of the soil.     

Effect of a Chemical Modified Urea Fertilizer on Soil Quality: Soil Microbial Populations Around Corn Roots

Slow‐release nitrogen (N) fertilizers are used to increase N‐use efficiency and extend N availability over a plant‐growing season. One formula of this fertilizer commonly used in turf and horticultural crops is methylene–urea–triazone. After this compound is applied in the soil, it is subject to bacterial degradation and becomes available for uptake by plants. The objective of this work is to elucidate the application of methylene–urea–triazone in the soil microbial population as well as effects on soil quality. Zea mays was planted in a silty loam soil. Urea and methylene–urea–triazone were incorporated into the soil. Two weeks and 6 weeks after inoculation, soil samples were collected and used to inoculate agar plates and for DNA extraction. Bacterial colony morphology was examined. Denaturing gradient gel electrophoresis (DGGE) was performed with the polymerase chain reaction (PCR) amplicons from the internal transcribed spacer (ITS) of the rRNA gene cluster. The Shannon Wiener index was determined for colony morphology and DGGE bands. There was a difference between urea and the slow‐release fertilizer on both plant responses and bacterial diversity. Although for the first 2 weeks DGGE did not show any difference in bacterial diversity, after 6 weeks, differences in the composition of the bacterial community were observed. There were concomitant effects on plant growth and microorganism population and diversity, probably reflecting changes in the richness and in the eveness of the bacterial population in the rhizosphere caused by the fertilizers. Therefore, both soil microorganisms and plant growth respond to environmental changes over time.     

利用15N示踪研究不同肥力土壤棉花氮肥减施的产量与环境效应

【目的】华北平原棉区中等肥力棉田经济最佳施氮量为300 kg/hm2左右,这一结果仅从产量效应得出,未充分考虑棉花对氮肥的回收利用和土壤中氮肥的残留。探讨低肥力土壤施氮量及施氮比例对棉花产量及氮肥利用率的影响,以及低、中、高肥力土壤条件下等量施氮效应,旨在为棉花减氮增效提供理论依据。【方法】田间试验选择了高 (S1)、中 (S2)、低 (S3) 三个肥力水平的地块,其全氮含量分别为0.83、0.74、0.60 g/kg。低肥力地块设置低氮 (N1 113 kg/hm2)、中氮 (N2 225 kg/hm2)、高氮 (N3 338 kg/hm2) 3个氮肥用量;中肥力和高肥力地块设低氮量处理,氮肥两次追施在苗期与初花期进行,氮肥比例为1∶2;此外,设置低肥力土壤低氮量,氮肥追施在苗期与初花期进行,氮肥分配比例为1∶1。在吐絮70%时采集棉株和土壤样品,用15N技术分析了棉株氮素吸收来源、籽棉产量、棉株氮肥回收率和土壤氮肥残留率。【结果】低氮处理,土壤肥力对棉花籽棉产量无显著影响,随土壤肥力提升,棉株吸收氮素来源于肥料的比例下降,相对增加了对土壤氮素的吸收。棉花植株15N回收率随施氮量增加显著下降,随土壤肥力提高呈下降趋势,低肥力土壤与中肥力土壤间棉花植株15N回收率差异不显著,但显著高于高肥力土壤。高肥力土壤15N残留率高于低肥力土壤和中肥力土壤。15N损失率随施氮量和土壤肥力提高显著增加。低土壤肥力低氮量条件下氮肥分配比例1∶2处理籽棉产量高于1∶1处理。低肥力土壤条件下,中氮处理籽棉15N积累量相对高于高氮和低氮处理,籽棉产量较优。【结论】在较低土壤肥力条件下,施氮225 kg/hm2籽棉产量和氮回收率均优于施氮338 kg/hm2,氮肥损失率较低,减氮增效是可行的。高肥力土壤条件下减少氮肥投入可减少肥料的浪费。     

Influence of surfactants on potassium uptake and yield response of cotton to foliar potassium nitrate

Foliar potassium (K) applications are intended to supplement soil K uptake, and thereby, increase cotton (Gossypium hirsutum L.) yields. Considerable research has been conducted to evaluate yield response to foliar K, but research evaluating surfactant effects on foliar uptake has been limited. Research was initiated in West Tennessee in 1991 to evaluate effects of foliar applied potassium nitrate (KNO₃) with and without surfactants on leaf and petiole K concentrations and on lint yield. Field research was conducted on three sites over a four year period using upland cotton ‘DPL 50’. Treatments included a check (no foliar treatment), 4.1 kg K/ha in water, 4.1 kg K/ha with Penetrator Plus, 4.1 kg K/ha with X‐77, 2.0 kg K/ha with Penetrator Plus, and 2.0 kg K/ha with X‐77. Surfactants were added to KNO₃ solutions at 1.25% v/v for Penetrator Plus and 0.5% v/v for X‐77. Kinetic was substituted for X‐77 after 1991 and was applied at 0.12% v/v. Cotton leaves and petioles were collected one, three, and seven days after each foliar application for K concentration determinations. Applying 4.1 kg K/ha (high‐K rate) as KNO₃ in water increased four‐year average leaf K but not petiole K concentrations in tissue collected 24 h after treatment relative to the check. Applying the high‐K rate with a surfactant increased the four‐year average concentration of leaves and petioles collected one, three, and seven days after application relative to the check or to the high‐K rate applied with water. Increases in both leaf and petiole K concentrations varied with year, with significant increases in two of the four years of the study. Yearly K concentrations of the day‐one and day‐three petioles were higher after applying the high‐K rate with Penetrator Plus relative to the check. Petiole K was not increased by applying low‐K rates with surfactants or the high‐K rate in water. First harvest lint yields were generally unaffected by foliar treatments. Second harvest and total yields were increased by applying the high‐K rate with Penetrator Plus relative to the other treatments. Yield responses may have been due in part to the nitrate anion (NO₃‐) being applied with the K+ cation, but higher K concentrations generally accompanied higher yields. These results suggest that surfactants may enhance K uptake and yield, but that more research is needed to determine why responses vary from year to year.     

Foliar application of urea to almond and olive: Leaf retention and kinetics of uptake

Regression equations relating volume of urea solutions retained on leaves initially and leaf area were developed to assess urea deposition nondestructively and facilitate measurement of urea uptake by leaves of olive (Olea europaea L.) and almond [Prunus dulcis (Mill.) D. A. Webb], Foliar uptake of urea was slower in olive than it was in almond, but uptake in both species was proportional to the concentration of the urea applied. Foliar uptake of urea was not influenced by previous applications. No phytotoxicity was apparent in almond and olive following single applications of 0.5% w/v urea and 4% (w/v), respectively. Approximately 15 times more urea could be applied per cm of an olive leaf than per cm of an almond leaf at the threshold of phytotoxicity. Leaf N content in olive was increased 47% with minimal phytotoxicity following 5 successive foliar applications of 2% urea within ten days.     

Foliar Fertilization of Crop Plants

Essential plant nutrients are mainly applied to soil and plant foliage for achieving maximum economic yields. Soil application method is more common and most effective for nutrients, which required in higher amounts. However, under certain circumstances, foliar fertilization is more economic and effective. Foliar symptoms, soil and plant tissue tests, and crop growth responses are principal nutrient disorder diagnostic techniques. Soil applications of fertilizers are mainly done on the basis of soil tests, whereas foliar nutrient applications are mainly done on the basis of visual foliar symptoms or plant tissue tests. Hence, correct diagnosis of nutrient deficiency is fundamental for successful foliar fertilization. In addition, there are some more requirements for successful foliar fertilization. Foliar fertilization requires higher leaf area index for absorbing applied nutrient solution in sufficient amount, it may be necessary to have more than one application depending on severity of nutrient deficiency. Nutrient concentration and day temperature should be optimal to avoid leaf burning and fertilizer source should be soluble in water to be more effective. Foliar fertilization of crops can complement soil fertilization. If foliar fertilization is mixed with postemergence herbicides, insecticides, or fungicides, the probability of yield response could be increased and cost of application can be reduced.     

Efficiency and response of sunflower to rate and timing of banded nitrogen

Abstract

Nitrogen use efficiency and response of sunflower (Helianthus annuus L.) to timing and rate of surface banded N was characterized in a split‐plot 4x2 factorial experiment. Nitrogen rates (main plots) were 0, 34, 67, and 134 kg ha^‐1 at Mississippi State and 0, 45, 90 and 180 kg ha^‐1 at Brooksville, MS. Nitrogen, applied as NH₄NO₃, was surface banded either at planting or at the four leaf stage (subplot). Seed yield was significantly influenced by rate of N application at both locations. Seed yield showed a quadratic response at Mississippi State and a Mitscherlich‐type response at Brooksville. Maximum seed yields of 2606 and 2380 kg ha^‐1 were obtained at the respective sites. Sunflower responded to N fertilizer application when inorganic N content of the soil to 60 cm depth at planting was less than 50 kg ha^‐1. Nitrogen efficiency was influenced by rate and timing of application, exhibiting exponential declines with increasing N rates. Fertilizer losses at the highest rates of applied N were 19 and 52% at Mississippi State and Brooksville, respectively. Clay‐fixed NH^⁺ accounted for 26% of the applied N fertilizer loss at Brooksville. Nitrogen fertilizer efficiency and recommendations for sunflower could be improved if initial soil inorganic N is taken into account.     

Effects of biochar,urea and their co‐application on nitrogen mineralization in soil and growth of Chinese cabbage

Experiments were conducted to study the effect of soil applications of kunai grass (Imperata cylindrica) biochar (0 and 10 t/ha) and laboratory grade urea (0, 200 and 500 kg N/ha) and their co‐application on nitrogen (N) mineralization in an acid soil. The results of an incubation study showed that the biochar only treatment and co‐application with urea at 200 kg N/ha could impede transformation of urea to ammonium‐N (NH₄⁺‐N). Soil application of biochar together with urea at 500 kg N/ha produced the highest nitrate‐N (NO₃^?‐N) and mineral N concentrations in the soil over 90 days. Co‐application of urea N with biochar improved soil N mineralization parameters such as mineralization potential (N_A) and coefficient of mineralization rate (k) compared to biochar alone. In a parallel study performed under greenhouse conditions, Chinese cabbage (Brassica rapa L. ssp. chinensis L.) showed significantly greater (P < 0.05) marketable fresh weight, dry matter production and N uptake in soil receiving urea N at 500 kg/ha or co‐application of biochar with urea N compared to the control. Application of biochar only or urea only at 200 kg N/ha did not offer any short‐term agronomic advantages. The N use efficiency of the crop remained unaffected by the fertilizer regimes. Applications of biochar only at 10 t/ha did not offer benefits in this tropical acid soil unless co‐applied with sufficient urea N.     

Response of soybean to foliar‐applied boron and magnesium and soil‐applied boron 1

Annual plants may partition carbon (C) preferentially to reproductive structures slowing root elongation and subsequent nutrient uptake. Although foliar applications of nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) supplement uptake by roots, soybean [Glycine max (L.) Merr.] yield increases have not been found in most studies. Experiments were designed to determine if foliar applications of boron (B), magnesium (Mg), or B+Mg would increase soybean yield and if soybean would respond to B applied to the soil several weeks prior to planting. Foliar B or Mg applied separately four times during reproductive growth did not affect soybean yield. However, four foliar applications of B+Mg increased soybean yield 12% at Mt. Vernon and 4% at Columbia over a three‐year period. Two foliar applications of B+Mg during the late reproductive stages increased soybean yield 8% over a two‐year period. The yield increase from foliar B+Mg treatment resulted from an increased number of pods on the main stem (18%) and branches (44%). A 2.8 kg/ha B application to soil eight weeks prior to planting increased soybean yield 11% during the first year and 13% the second year but had no effect on soybean yield by the third year after application. When results from the first two years were combined, 2.8 kg/ha B applied to soil increased the number of pods per branch by 17% and the number of branch pods per plant by 39%. Foliar applications of B+Mg increased soybean yield in four of six site‐years in the three‐year experiments at two locations.