Effect of inoculum,variety, nitrogen,phosphorus, and potassium on yield,protein and oil content of soybeans at jabalpur,M.P. India

Abstract

Regardless of inoculum or fertility rate Bragg outyielded Clark 63 soybeans. Yields of Bragg and Clark 63 were increased about 1000 kg per ha by treatment with inoculum at the rate of approximately 313, 000 bacteria per seed. At the highest rate of applied N, yields of uninoculated soybeans, were lower than the inoculated soybeans at the lowest applied N rate. Phosphorus fertilizer increased yields at a decreasing rate and yields were decreased at the highest rate of applied P. Potassium fertilizer had a negative effect on soybean yields and did not significantly effect the protein or oil content of soybean seed. With increasing P fertilizer rates, there was a decrease in oil content and in increase in protein content of soybean seed.     

Effect of inoculum,variety, phosphorus,and potassium on certain attributes of two soybean varieties at Jabalpur,M.P., India

Abstract

An experiment to determine the effect of inoculum, N, P, and K on certain attributes of two soybean varieties was conducted in 1967 at JNKW. The experimental area had no prior history of soybean production and contained few, if any, soybean rhizobia.

Plant height, height to first pod, lodging, seed quality, and seed weight were affected by applied N. Applied P had a quadratic effect upon plant height, while plant height decreased linearly with increasing levels of applied K. The effect of N was linear and applied P curvilinear upon lodging. Uninoculated plants had seed with poorer seed quality scores and lower seed weights than inoculated plants. Applied P increased seed weight. Height to first pod was higher for Bragg than for Clark 63.     

Stability of sugar content in soybean strains

Abstract

Objectives in this study were to measure total sugar and individual sugar content in whole, mature, soybeans of certain strains and to determine the stability of these components in strains grown over a wide geographical area. Soybean seed of three selected strains from each Maturity Group in the 1970 Uniform Tests‐Northern States were analyzed for total sugar, sucrose, raffinose and stachyose content. For Maturity Groups 00, 0, I, II, III and IV there were 10, 12, 23, 33, 27 and 24 locations, respectively. The locations were in 17 states and 2 Canadian provinces.

The average content of total sugar, sucrose, raffinose and stachyose was 9.36, 5.96, 0.75 and 2.65 g per 100 g seed, respectively. Analysis of variance of total sugar content and individual sugars among the three strains within each Maturity Group revealed significant differences (P<.01) in total sugar among strains in Maturity Groups II and III but not in the other four Maturity Groups. Except for strains within Maturity Group IV, there were significant differences (P<.01 or P<.05) among the strains within each Maturity Group for sucrose, raffinose and stachyose. Few significant environmental index (linear) x strain interactions were observed for total sugar content or for any of the individual sugars.     

Evaluation of diagnosis and recommendation integrated system (DRIS) on early maturing soybeans

Abstract

The Diagnosis and Recommendation Integrated System (DRIS) appears to be a more sensitive tool in the early detection of mineral deficiency in soybeans (Glvcine max. L.) than the sufficiency range approach. A small data bank based on information collected in a survey over a two‐year period on early maturing soybeans grown in Quebec was used to calculate new modified DRIS norms. Remedial measures predicted by DRIS gave greater yield increases than those with the sufficiency range approach. Regional deviation in norms were identified and were more important with ? related ratios     

Nutrient concentration and yield variation within southern soybean germplasm grown on acid Norfolk soil

Abstract

Seventy‐one soybean genotypes were grown in the field on an acid Norfolk loamy sand to evaluate growth, seed yield, and nutrient concentrations in aerial plant fractions. The pH values in the Ap, A2, and B horizons were 4.6, 4.4, and 4.4, respectively. Cation exchange capacities (CEC) were 2.1, 0.9, and 2.8 me/100 g with an Al saturation of 34, 49, and 40%, respectively. Very few visual toxicity or deficiency symptoms were found among the genotypes. Analyses of aerial plant fractions collected when the genotypes were in bloom or early pod fill showed some significant differences, but In general P, K, Ca, and Mg concentrations were adequate, while Al, Fe, Mn, and Zn concentrations were very high. Average yields of genotypes in maturity groups IV, V, VI, VII, and VIII were 2.7, 2.7, 2.6, 2.4, and 2.2 t/ha, respectively. There were significant differences in seed yield among genotypes in maturity groups IV and VIII, but differences among genotypes in the other maturity groups were nonsignificant. Correlations between yield and nutrient concentration showed some significant relationships, but in general, this technique did not differentiate genotypes according to their tolerance to acid soil conditions.     

Effect of Mn on growth,modulation, and nitrogen fixation by soybeans grown in the greenhouse

Abstract

Soybean (Glycine max (L.) Merr. cv Bragg) plants were grown in the greenhouse using a low‐Mn Leefield sand amended with 0, 2.5, 5, 20 and 50 yg Mn/g. The plants were inoculated and were primarily dependent on symbiotically fixed N. Measurements of DTPA‐extractable soil Mn, soil pH, leaf tissue Mn, top weight, top N content, and nodule weight, volume and number were made at 27, 42, 56, 63 and 69 days after planting. The DTPA extrac‐tant was a good predictor of leaf tissue Mn giving a highly significant (P = 0.01) overall correlation coefficient of 0.704 for this comparison. Because of an unexpected decline in soil pH from 6.8 to 6.0 and an associated increase in DTPA‐extractable Mn from 0.14 to 0.24 yg/g during preparation and handling prior to the first harvest time, Mn in the leaf tissue of the controls was never less than 21 yg/g. Since this concentration of Mn is above the deficient level, no significant responses in top growth, nitrogen fixation or nodule measurements were obtained from the addition of low rates of Mn. The highest Mn rate was only mildly toxic in terms of top growth and top N content, producing leaf tissue having Mn concentrations ranging from 171 to 180 yg/g at the last three harvest periods.     

Biofortification of soybean grains with foliar application of Li sources

Abstract

Biofortification of soybean grains with lithium (Li) is a strategy to improve a food with high social acceptance, in order to promote health benefits. The aim of this work was to evaluate the development of plants and the production of biofortified soybeans with two Li sources. The experiment was conducted in a completely randomized design with five replicates. Ten treatments were obtained in a 2x5 factorial scheme, comprising two sources of Li (LiOH - Li hydroxide and Li₂SO₄ - Li sulfate) and five doses (0, 30, 60, 90 and 120?mg kg^?1) in stages V4 and R1. The supply of Li promoted significant effects (p?≤?0.05) on the morphology, yield components and nutritional status of soybean plants. The highest grain yield was obtained with the use of Li₂SO₄ at the estimated dose of 45.7?mg kg^?1. The plants accumulated Li between 8.00 and 11.20?mg kg ^?1, respectively, with the use of Li₂SO₄ and LiOH. In the grains, the highest concentrations of Li were obtained with the application of 120?mg kg^?1. Li₂SO₄ and LiOH are good sources for biofortification of soybean grains.     

Effect of phosphorus,nitrogen fertilization and foliar applied manganese on yield and nutrient concentration of soybean

Abstract

A greenhouse experiment was conducted on clay loam soil of pH 7.8 to evaluate the effect of P, N fertilization and foliar applied Mn on yield and nutrient concentration in leaves and seeds of soybean. A significant yield increase was obtained for each added increment of P fertilizer up to 30 kg P₂O₅/acre. At application rates of 0, 15, 30 & 45 kg P₂O₅/acre, the seed yield was subsequently 27.8, 65.8, 82.8 & 83.6% of the maximum yield obtained at the maximum calculated P level. The yield increase accounted 14.2 and 10.2% for N and Mn applications. In all treatments, in which P was combined with N, the seed yield was relatively higher than with P or N applied alone.

Phosphorus, N and Mn content in leaves and seeds were positively correlated with the applied nutrient fertilizers. At any given level of applied P and Mn, P content was significantly higher in +N than ‐N treatments. By Mn application, P content in leaves and seeds was decreased. Phosphorus and Mn applications did not influence N content in leaves and seeds.     

“Starter nitrogen”; fertilization in soybean culture

Abstract

Proponents of the “starter nitrogen”; concept believe that a small amount of nitrogen fertilizer stimulates early vegetative growth of soybeans, thereby facilitating cultivation and weed control. To evaluate this concept, soybean leaf area, plant height, fresh weight, and yield were measured over three growing seasons. Growth parameters were measured at weekly intervals during the 7 weeks following planting of ‘Bragg’ soybeans (Glycine max (L.) Merr.) which had received 0, 16.8, and 50.4 kg N ha^‐1 banded pre‐plant into the soil.

The analysis, a multiple linear regression maximum R² (multiple correlation coefficient) improvement procedure, showed that starter nitrogen did not significantly (.05) influence leaf area, plant height, fresh weight, or yield of Bragg soybeans.     

Residual effects of potassium placement for conservation-till corn on subsequent no-till soybean

Biannual surface application of potassium (K) fertilizer prior to corn (Zea mays L.) in a corn–soybean (Glycine max (L.) Merr.) rotation has been common in conventional-till crop production in North America; however, whether this traditional K management practice is effective for soybean when both corn and soybean are grown with conservation tillage is largely unknown. This study evaluated the residual effects of spring K fertilizer placement in conservation tillage systems applied to previous corn on subsequent no-till soybean. Experiments involving a corn–soybean rotation were conducted from 1997 to 2000 on a silt loam soil (Albic Luvisol) with 12 years of continuous no-till management near Paris, Ontario, Canada. The fields had low initial soil-test K levels (<61 mg l⁻¹) and evident soil K stratification in the top 20 cm. In the “corn” years from 1997 through 1999, spring K fertilizer placement methods of deep band (76 cm centers), surface broadcast, broadcast plus shallow band, and no K were evaluated for no-till, spring zone-till, and spring mulch-till tillage systems (1997 and 1998) but for no-till alone in 1999. From 1998 to 2000, soybean was no-till planted in 19 cm row widths on the respective previous-year corn treatments without further K fertilizer application. Soybean leaf K concentrations responded more frequently and positively to K application in no-till corn than in zone-till and mulch-till corn. Deep band and surface broadcast K placements were similar in their residual effects on soybean leaf K. Positive soybean yield responses to residual K fertilizer were observed in only 1 out of 3 years despite consistent increases in both soil K and soybean leaf K concentrations where K was applied to previous corn. On long-term no-till fields with low soil K levels, interrupting a continuous no-till corn–soybean system with mulch-till corn production provided residual benefits in soil K availability and leaf K nutrition for subsequent no-till soybean. Furthermore, the residual effects of K fertilizer applied to previous corn on subsequent no-till soybean were not affected by K placement method.     

Influence of lime and phosphorus on soybean (Glycine max (L.) Merrill) yield,leaf and seed composition on a paleudult soil

Abstract

This research was undertaken on a paleudult soil in southern Brazil, 30° south latitude, to quantify lime and P effect upon soybean (Glycine max (L.) Merrill). A lime x P factorial experience with lime treatments of 0, 0.5, 1, and 2 times SMP interpretation to pH 6.5, and 0, 44, 88, 132, and 176 kg P/ha with 3 replications were installed. The experiment was conducted for 2 years (1973–74, 1974–75), with leaf‐N, P, and K; yield; seed‐N, P, and K; Bray P₂ (0.03N NH₄F + 0.1N HC1) avail‐able‐P and soil pH measurements completed each year. Data was evaluated with linear, quadratic, logarithmic, polynomial, segmented line, and multiple regression using the coefficient of determination as goodness of fit.

The best model fit between P treatment and Bray P₂ available‐P was a quadratic equation; the model between relative yield and Bray P_2‐P with 54% of the relative yield attributed to Bray P₂ available‐P, a sigmented line. This model indicated point of maximum yield (91% relative yield) was obtained at 7.4 ppm‐P, with no increase in relative yield with increasing levels of soil available‐P. To calculate the P fertilizer necessary to increase available soil‐P to the level of maximum yield of equation Y_p = [1639(7.4 ‐ x_s)]^1/2, where Y_p = kg P/ha fertilizer needed; and x_s = initial Bray P₂ soil available‐P in ppm's. The lime effect upon soil pH was best described as a linear relationship. Yield increase with lime at this site was not significant at the 5% level.

The leaf‐N, P, and K increased significantly with soil available‐P levels. A second degree polynomial with logarithmic function best defined these relationships. The calculated DRIS indices and sum proved useful to evaluate the plant‐N, P, and K balance of each treatment.

Only seed‐P level was directly related to soil available‐P. Both seed‐N and seed‐K were highly correlated with indirect effects of soil available‐P levels.

Results from this study suggest the segmented line model would best interpret soybean yield response to Bray P₂ available‐P for this soil. To obtain maximum yield using this model rather than the second degree polynomial would require less fertilizer P. Foliar analyses interpretation confirmed adequate plant‐P level would be supplied for maximum yield at this level of fertilization.     

施用钾肥对叶菜产量和品质的影响

Over a period of two years, field experiments were conducted on four silty loam soils grown with foliar vegetable crops including Chinese cabbage (Brassica pekinensis Rupr., cv.Lu-Bai 3), autumn greens (B. chinensis L., cv.Piao-Geng-Bai), winter greens (B. var.rosularis Tsen et Lee, cv.You-Dong-Er), and summer greens (B. chinensis L., cv.Zao-Shu 5), respectively. Each experiment included one CK treatment without K, N and P fertilizers applied, and four treatments with from low to high doses, 0~300 kg hm^-2 for Chinese cabbage, 0~150 kg hm^-2 for autumn and winter greens and 0~180 kg hm^-2 for summer greens, of K fertilizers in the form of sulfate of potash (SOP) applied together with N and P fertilizers. One treatment of K fertilizer in the form of muriate of potash (MOP) applied at high levels (150 or 180 kg hm^-2) together with N and P fertilizers was included in the experiments of autumn, winter and summer greens, respectively, in order to compare the effects of SOP and MOP. The market yields of the tested crops increased significantly with the increasing rate of K application. The crops supplied with K fertilizers yielded more stably as the CV% of their yields decreased with the rate of K application. K fertilization increased not only K contents but also the amounts of N, P and K absorbed in shoots of autumn, winter and summer greens, which were statistically significantly correlated to their yields. It can also be found that potassium improved the quality of the foliar vegetable crops as their dry mater contents were generally increased and Vc contents obviously increased and nitrate contents markedly decreased. As compared to MOP, SOP was more effective on the yields and quality of autumn, winter and summer greens at the high levels of fertilization.     

Copper,nitrogen, and Rhizobium japonicum relationships in determinate soybean

A relationship among Cu, N, and Rhizobium japonicum was hypothesized because previous research had shown that (a) 35% or more legumes in the Atlantic Coastal Plain have Cu concentrations of 6 mg kg^‐1 or less, (b) Cu influences N fixation in some legumes, and (c) irrigated soybean (Glycine max L. Merr.) can accumulate most of its N through fixation. Soybean were grown on a Cu‐deficient Norfolk (fine‐loamy, siliceous, thermic Typic Paleudult) loamy sand with 3 fertilizer sources of Cu, 2 strains of R. japonicum, and with or without 336 kg ha^‐1 of N fertilizer. Application of Cu significantly increased the number of pods plant^‐1 suggesting pod abortion in determinate soybean may be caused by low Cu, but seed yield was not increased. Fertilization with N increased vegetative growth, but not total biomass or seed yield. Inoculation with R. japonicum strain 110 significantly increased seed yield by 0.3 Mg ha^‐1 compared to strain 587. The yield increase was similar with or without fertilizer N application indicating strain response was not totally caused by improved N efficiency. There was no relationship between seed yield and nodule occupancy as measured by the ELISA technique.     

Simulation of effects of soil bulk density and p addition on k uptake by soybeans

Abstract

Increasing soil bulk density has been shown to reduce root growth and decrease K uptake by soybeans (Glycine max L. Merrill). Changing soil bulk density also affects soil buffer power, b, and effective diffusion coefficient, De, which affect K influx. The relative decrease in K uptake due to reduced root growth as compared to reduced K influx is not known. Addition of P may affect root growth and P influx properties of plant roots. The objectives of this paper were (1) to use the Cushman mechanistic model to simulate the effect of changing soil bulk density and soil P on K uptake by soybeans, and (2) to determine the parameters that are changed by changes in bulk density and added P and their effect on K uptake. Plant and soil data of an experiment where Williams soybeans were grown for 21 days in pots of Raub (Aquic Argiudoll) silt loam with factorial treatments of two rates of K (0 and 100 mg K kg^‐1 soil), two rates of P (0 and 100 mg P kg^‐1 soil), and two bulk densities (1.25 and 1.45 g cm^‐3 ) were used to verify the model. Plant and soil parameters for the model were measured independently of the verification experiment. Predicted K (y) uptake agreed with observed uptake (x) (y = 1.09x‐0.19; r = 0.97) for the P x K factorial and (y = 1.19X‐0.22; r = 0.90) for the K x soil bulk density factorial treatments. In a sensitivity analysis, the model predicted a maximal K influx at a soil bulk density of 1.38 g cm^‐3. The greatest effect of soil bulk density on K uptake was due to reduction of root growth. Increased K uptake as a result of P addition was because of the effect on root growth.     

Boron foliar fertilization of soybean and lychee: Effects of side of application and formulation adjuvants

Experiments to assess the rate of absorption and translocation of foliar‐applied, isotopically labeled boric acid (BA) were carried out with lychee (Litchi chinensis Sonn.) and soybean (Glycine max [L.] Merr.) plants. Boron (B) absorption and translocation within the plant, one week after treatment, was investigated after adding to the boric acid (BA solutions 0.5 mM CaCl₂ and/or 50 or 500 mM sorbitol). The contribution of stomata to the absorption process was assessed by applying the solutions either to the adaxial or to the abaxial leaf side. Both plant species differed greatly in total absorption rates. The adaxial leaf surface (lacking stomata) of lychee leaves was nearly impermeable, while the stomatous abaxial surface was permeable to BA solutions. In this species, no translocation of ¹⁰B to other leaf parts and no effect of adjuvants in increasing ¹⁰B absorption were recorded. In contrast, ¹⁰B was absorbed both by adaxial and abaxial leaf surfaces of soybean leaves. Boron concentrations measured in treated soybean leaves were sixfold higher after application to the abaxial as compared to the adaxial leaf surface. The addition of adjuvants significantly enhanced the rate of ¹⁰B absorption, but not its translocation within the plant. Treatments containing 500 mM sorbitol led to increased ¹⁰B absorption and enhanced acropetal ¹⁰B movement, whereas adding only 50 mM sorbitol had no significant effect. Application of 0.5 mM CaCl₂ in combination with 500 mM sorbitol decreased the rate of ¹⁰B absorption, compared to the performance of 500 mM sorbitol alone. Basipetal ¹⁰B translocation was very limited. A distinct effect of B‐sorbitol complexes on B translocation apart from the pure adjuvant effect could not be discerned in this investigation.     

渗透胁迫与大豆幼苗叶片多胺含量的关系

用高效液相色谱(HPLC)法对渗透胁迫下两个抗旱性不同的大豆品种(抗旱性弱的豫豆6号和抗旱性强的豫豆24号)幼苗叶片的三种不同形态多胺游离态(Free:f)、酸可溶性共价结合态(Acid.soluble.covalently.conjugated:AS-CC)和酸不溶性共价结合态(Acid.insoluble.covalently.conjugated:AISCC))的含量变化进行了研究。结果如下:三种游离态多胺:腐胺(fPut)、亚精胺(fSpd)和精胺(fSpm)均在渗透胁迫条件下上升,但是豫豆24号的fSpd和fSpm的上升幅度明显大于豫豆6号,而豫豆6号的fPut的升幅明显大于豫豆24号。甲基乙二醛-双(鸟嘌呤腙)(MGBG)处理豫豆24,明显抑制了渗透胁迫诱导的fSpd和fSpm的增加,并且加重了渗透胁迫的伤害;外源Spd处理豫豆6号明显促进了渗透胁迫诱导的fSpd和fSpm的增加,并且减缓了渗透胁迫的伤害。统计分析表明:在渗透胁迫条件下,大豆幼苗叶片的fSpd+fSpm/fPut的比值与相对干重增长率(RDWIR)呈显著正相关。渗透胁迫下,豫豆24叶片的AISCC-PAs含量的上升幅度明显大于豫豆6号。菲咯啉处理明显抑制了渗透胁迫所诱导AISCC-PAs的增加,同时也加重了渗透胁迫对幼苗的伤害。渗透胁迫也引起了幼苗叶片中ASCC-PAs含量的上升,但是在两个大豆品种之间的上升幅度没有差异。这些结果表明,渗透胁迫条件下,大豆幼苗叶片的fSpd、fSpm及AISCC-PAs含量的上升有利于增强大豆幼苗的抗胁迫能力。     

Effect of supplying P to a portion of the soybean root system on root growth and P uptake kinetics 1

Abstract

Knowledge of the effect of supplying P to portions of the soybean (Glycine max L. Merr) root system on P influx kinetics and root growth is important in developing P fertilizer placement practices for efficient fertilizer use. The objective of this research was to determine the effect of restricting P supply to portions of the root system on plant P status, root growth, and P influx kinetics. Two solution experiments were conducted in a controlled climate chamber. Phosphorus influx kinetics were determined on 25‐day‐old soybean plants that had been grown with 100, 75, 50, 25, and 12.5% of their roots initially exposed to P. Phosphorus influx kinetics were also measured on 25‐day‐old plants that had been P‐starved for the last 1, 2, 4, and 6 days prior to the determining P influx kinetics in order to relate plant P status to P influx kinetics.

Reducing the portion of the roots supplied with P reduced P uptake. This resulted in a reduction in plant P concentration and was related to a 3.41‐fold increase in maximum P influx measured on 25‐day‐old plants. Restricting the proportion of roots supplied with P had no significant effects on the Michaelis‐Menten constant or on the concentration in solution where net influx was zero. Root growth rate of the roots in the P containing solution was not significantly different from those in the ‐P solution.

Phosphorus uptake was correlated with final root surface area exposed to P (r² = 0.88??). Starving the plants for P reduced P concentration in the shoot and root and this resulted in as much as a 1.68‐fold increase in maximum influx.     

Comparison of four phosphorus extraction methods on three acid southeastern soils

Abstract

Phosphorus extractants have not been tested extensively in the Southeast. An experiment was carried out to compare four P extractant methods using samples from a field P‐K factorial experiment with soybeans (Glycine max (L.) Merr.) at three locations in Georgia over four years. There were five P rates ranging from none to 80 kg ha^‐1. Soils and plant tissue were sampled at mid‐summer and yields were recorded. The four P extractants compared were Olsen, Mehlich 1, Mehlich 2, and Bray 1. Quadratic regressions for soil P versus plant P and P rates were not significant compared to linear regressions. There were no significant yield responses to P. All extractants except Olsen were similar in their response to added fertilizer P as measured by linear r² values. Olsen P gave lower linear r² values both with P rate and with plant P. Mehlich 1 values were highly correlated with Mehlich 2 (0.94**) and Bray 1 (0.96**). Mehlich 2 and Bray 1 gave nearly the same soil P values with linear regressions of slope of 1.0 and low intercepts. Results from these experiments show that Mehlich 1, Mehlich 2, or Bray 1 could be used successfully on these soils, but that Olsen should be avoided.     

Foliar diagnosis of soybean by dris

Abstract

The Diagnosis and Recommendation Integrated System (DRIS) has proven useful in the interpretation of tissue elemental analyses for many crops, and research was undertaken to apply the same method for foliar diagnosis of soybean (Glycine max [L.] Merr.). Using a data bank in excess of 3500 tissue samples, reference values for evaluating the status of soybean with respect to N, P, K, Ca, Mg, Mn, Fe, Cu, Zn, Mo, B and Al were derived. DRIS diagnoses generally agreed with those obtained by the sufficiency range method. In addition, DRIS assessed the nutrient balance in plant tissue, and identified not only the most‐limiting element, but the order in which other elements would likely become limiting. Further, DRIS was able to diagnose plant nutrient needs earlier in the life of the crop than the sufficiency range method (5 weeks compared to 10 weeks), which would allow remedial steps to be taken earlier. Treatments indicated by DRIS to be needed gave greater yield increases than those indicated by the sufficiency range approach. Geographic differences in DRIS norms were identified, and indicate that regional derivation of diagnostic values may be necessary.     

Potassium uptake by soybean as affected by exchangeable potassium in soil

Abstract

Soybean (Glycine max (L.) Merrill) has been shown to have a great capacity to take K from soil, suggesting that it might absorb K from non‐exchangeable forms. In this paper, the effect of level of K fertilization on soil exchangeable K content and K uptake by soybean are discussed. The experiment was conducted on a Typic Haplortox (sandy loam), fertilized with 0, 40, 80, 160 and 240 kg K₂O/ha as KC1 or K₂SO₄. During five years before the experiment, half of the plots received those K rates annually and the other half only in the first three years, providing an opportunity to study the residual effect of applied K. Plant samples were taken at pod filling and at harvest. Soil cores were collected in 20 cm increments down to 80 cm deep at plant emergence, pod filling and after harvest. There was a residual effect of K, and 240 kg K₂O/ha applied in a 3‐year term led to the same yield and K uptake as 80 kg ICO/ha applied annually for 3 years. Fertilized plants absorbed 160% more K than unfertilized ones, but soil exchangeable K accounted for less than 50% of plant uptake; therefore the exchangeable pool must have been replaced in time for soybean uptake. On the other hand, the K recycled from the plant to the soil was not found in the exchangeable form. There was evidence of K leaching deeper than 80 cm, and in addition, the K recycled from the plants may have turned into non‐exchangeable forms in the soil.