Nitrogen Fixation and Nitrate Assimilation of Determinate, Semi-determinate and Undeterminate Soybeans (Glycine max L.)

Soybean ( Glycine max L.) nitrogen nutrition is ensured by both symbiotic nitrogen fixation and mineral nitrogen assimilation. The relationship between these two modes of N nutrition was analysed in 3 growth types (determinate, semi-determinate and undeterminate) of soybean. The nitrate reductase activity and nitrogenase activity (acetylene reduction) of plants grown in the field and greenhouse showed that these enzymatic activity acted simultaneously or successively during the growth cycle, depending on the availability of inorganic nitrogen in the growing medium. Undeterminate soybean types had a higher potential nitrate reductase activities than determinate types.
The proportion of N₂ fixed as measured by ¹⁵N labelling or stem ureide content indicated that determinate soybeans derived a higher proportion of their N from N₂ fixation than the undeterminates.     

Nitrogen Fixation by Hybrids of White Clover (Trifolium repens L.) and Trifolium nigrescens

Development of hybrids between white clover ( Trifolium repens L.) and Trifolium nigrescens provides a novel route for genetically improving the reproductive capacity of white clover, provided the hybrids are agronomically viable, particularly with respect to N₂ fixation. A comparative study of growth and rates of N₂ fixation over 21 days was conducted with the parental species, F ₁ hybrids and backcross hybrids, in flowing solution culture, without a supply of mineral N to the plants. T. nigrescens was unable to fix N₂ in association with the strains of Rhizobium leguminosarum biovar. trifolii selected for inoculation. Rates of N₂ fixation per plant increased in the order T. nigrescens < F ₁ hybrid < T. repens < backcross 1. Specific rates of N₂ fixation (days 0–21) increased in the order T. nigrescens < F ₁ hybrid < backcross 1 <  T. repens . Dry matter production and nodule biomass per plant increased at a higher rate in backcross 1 hybrids than in T. repens. The results suggest that the potential for N₂ fixation by backcross 1 hybrids is at least as great as that by T. repens .     

Estimation and Partitioning of Nitrogen Fixed by Soybean in Mediterranean Climates

A field study was conducted to estimate the nitrogen fixation by soybean [ Glycine max (L.) Merr.], using the A-value and the N-difference methods, and to examine the N partitioning within the plant. The cultivar Clark and its non-nodulating isoline (as reference crop) were grown in a silty clay (Typic Xerothent) soil, in 1991 and 1992. ₁₅N-Labelled fertilizer was surface applied in solution, at rates of 20 and 100 kg N ha⁻¹ to the nodulating and non-nodulating soybean, respectively. Plant samples were taken at full bloom (R2), beginning of seed growth (R5) and physiological maturity (R7). There was little nitrogen fixation at the early growth stages but it increased rapidly during the seed filling period. At R7 nitrogen fixed was estimated by the A-value method as 155 kg N ha_-1 in 1991 and as 240 kg N ha⁻¹ in 1992. The corresponding estimates by the N-difference method were significantly smaller. The seeds had a higher, and the vegetative parts smaller, proportion of fixed nitrogen compared to the whole plant. During the seed filling period, the translocation efficiency for fixed nitrogen was greater (93 % in 1991 and 85 % in 1992) compared to the N derived from soil (75 and 56 %, respectively). It was estimated that, after the harvest of pods, the soil was depleted by a net amount of 121 kg N ha⁻¹ in 1991 and 90 kg N ha⁻¹ in 1992.     

The Performance of Pea (Pisum sativum L.) and its Role in Determining Yield Advantages in Mixed Stands of Pea and Oat (Avena sativa L.)

On a brown warp soil (Fluventic Eutrochrept) near Goettingen, Germany, conventional leafed pea ( Pisum sativum L. cvs Messire and Bohatyr) and semileafless types (cvs Profi, Juno and Azur) were grown in mixed stands together with oat ( Avena sativa cvs Alf and Lutz) in substitutively designed experiments from 1995 to 1997. Oat was the dominant component. Crowding coefficients for oat averaged 7.4. No relationship could be detected between the crowding coefficient of oat and any yield advantage from the mixture. Crowding coefficients for pea varied substantially, between 0.1002 (Juno and Alf in 1996) and 0.2979 (Bohatyr and Alf in 1996). Crowding coefficients for semileafless pea cultivars were smaller than for conventional leafed types. The yield advantage of the mixture increased as the crowding coefficient of pea increased. The maximum yield increase for the mixture was achieved when the relative yield total (RYT)=1.17 or + 11 dt grain DM ha^–1 for mixtures of the long-strawed conventional leafed cultivars Bohatyr and Alf (in 1996). The crowding coefficients of pea were positively correlated with the level of symbiotically fixed N₂ in the mixed stands. When N₂ fixation with mixed cropping was about 30 kg N ha^–1, RYT was unity. Increasing symbiotic N₂ in the mixtures resulted in increasing yield advantages in the mixture. Short-strawed pea cultivars seem unsuitable for mixing with oat. Plant height of pea appeared to be more important than plant leaf type. Accordingly, mixtures containing the long-strawed semileafless pea cultivars Profi and Alf were more successful. It is concluded that increased competitiveness of the pea component in the mixture with oat entails increasing the level of symbiotic N₂ fixation including resource complementarity and thus yield advantage in the mixed stands.     

The Effects of Intercrop Spacing Patterns on the Silage Yield of Maize and Soybean

The effects of intercrop spacing patterns on the silage yields of both maize (lea mays L.) and soybean (Glycine max [L.] Merr.) were examined from 1985 to 1987. Dwarf maize was intercropped with nonnodulatmg or nodulating soybean in the spacing patterns, S_40same (two crops in the same row, 40 cm row width) and S_20ait or S_40ak (two crops in alternate rows, 20 cm or 40 cm row width, respectively). Tall maize was intercropped with nodulating soybean in S_40sames S_40alt and S_40pair (maize in 40 cm paired rows, soybean rows 20 cm outside each maize row and 80 cm from the next set of four rows) at 0 or 60 kg N ha⁻¹ and at population densities of 67% maize: 67% soybean or 50 % maize: 50% soybean. Maize and soybean were also intercropped and stripcropped on a farm-scale. The only difference between intercrops arranged in the same rows versus those in alternate rows was that the average soybean protein yields were higher in S_40same than in S_40alt. In 1986, the S_40alt maize-soybean intercrops produced higher maize yields, total biomass yields and Land Equivalent Ratios (LERs) than in S_40pirs, and in 1987, these responses were higher in intercrops than in stripcrops. In 1986, at 0 kg N ha⁻¹, the soybean biomass and protein yields were lower in S_40alt, than in S_40pairs and in 1987, these responses were lower in intercrops than in stripcrops.     

N2-Fixierung und Ertragsstruktur der Weißen Lupine (Lupinus albus L.) im Vergleich zu Vicia faba L. und Glycine max (L.) Merr. auf verschiedenen Standorten

N₂-Fixation and Yield Structure of White Lupin ( Lupinus albus L.) in Comparison to Vicia faba L. and Glycine max (L.) Merr. on Different Sites
In field studies white lupin ( Lupinus albus L., Eldo ) was compared with faba bean ( Vicia faba L., Herz Freya ) in 1986 and soybean ( Glycine max [L.] Merr., Gambit ) in 1988 on five sites respectively. Total N₂-fixation, which was determined by the extended difference method, and yield components were correlated to weather and soil conditions:
1. While faba bean responded to low pH with delayed nodulation, white lupin showed no decrease in N₂-fixation at pH less than 5.5 as far as soil was not calcareous.
2. The white lupin developed its root system most quickly into further soil depths and produced a root dry weight six times as large as that of faba bean in the soil layer 60-90 cm until the end of July (Bayreuth).
3. Despite on the calcareous sites the white lupin showed the highest total-N₂-fixation (max. 36 g N/m²) throughout, the N-gain for the succeeding crop was up to 8 g N/m² for white lupin and faba bean as well. In contrast the N-balance of soybean was mostly negative.
4. Seed yields of white lupin (48-450 g/m²) ranged between those of faba bean (145-549 g/m²) and of soybean (89-290 g/m²); its raw protein yields were the highest found (max. 158 g/m²) though.     

Physiological Responses and Dry Matter Partitioning of Summer Mungbean (Vigna radiata L.) Genotypes Subjected to Drought Conditions

Drought is the most important limitation to summer mungbean production in the tropics and subtropics dependent on usually insufficient summer rainfall. As increased irrigation is not a viable answer to the problem, an economically and environmentally desirable solution is new varieties with drought tolerance. However, there is little genotypic information on drought tolerance in summer mungbean. The objectives of this study were to assess the genotypic differences in physiological traits and dry matter partitioning in mungbean and to measure the association of these traits with crop performance under drought conditions. Six mungbean genotypes were tested in drought micro plots at CCS Haryana Agricultural University, Hisar, India. A split plot design was used; two irrigation treatments (watered and droughted) in the main plots and six mungbean genotypes in the subplots with three replicate micro plots. Drought decreased leaf water status, rates of photosynthesis (P_n) and altered dry matter partitioning in different plant parts. Our results showed that P_n did not limit yield, but it was partitioning of dry matter governed by leaf water content (RWC) which influenced the final yield. RWC was positively correlated to the number of pods per plant and seed yield, genotypes maintaining high RWC produced higher seed yield. Therefore, the drought tolerance of summer mungbean was related to the maintenance of high RWC, which can be used as a physiological marker to identify and develop superior genotypes suited to drought-prone environments.     

Yield and Resource Use Optimization in Late Transplanted Mint (Mentha arvensis) under Subtropical Conditions

A field experiment was conducted during 1994 and 1995 at Lucknow (26.5°N, 80.5°E, 120 m above mean sea level) to optimize planting density and fertilizer-N application for high essential oil yield of late transplanted mint ( Mentha arvensis ). The treatments studied were 2.5, 2.0 and 1.66 × 10⁵ mint seedlings ha⁻¹ and 0, 80, 160 and 240 kg N ha⁻¹. Under 3 months delayed planting conditions using 2-month-old seedlings, the high planting density of 2.5 × 10⁵ plants ha⁻¹combined with 160 kg N ha⁻¹ gave significantly higher herb and essential oil yields compared with those of lower planting densities (2 and 1.66 × 10⁵ plants ha⁻¹) and all other rates of N application. It is demonstrated that a transplanted mini crop, yielding essential oil at a level of 164 kg ha⁻¹, is feasible after the harvest of rabi cereal, oil seed or legume crops in the north Indian plains.     

Direct and Residual Contributions of Symbiotic Nitrogen Fixation by Legumes to the Yield and Nitrogen Uptake of Maize (Zea mays L.) in the Nigerian Savannah

Field experiments were conducted to determine the direct and residual contributions of legumes to the yield and nitrogen (N) uptake of maize during the wet seasons of 1994 and 1995 at the University Farm, Abubakar Tafawa Balewa University, Bauchi, Nigeria, located in the Northern Guinea savannah of Nigeria. Nodulating soybean, lablab, green gram and black gram contributed to the yield and N uptake of maize either intercropped with the legumes or grown after legumes as a sole crop. Direct transfer of N from the nodulating soybean, lablab, green gram and black gram to the intercropped maize was 24.9–28.1, 23.8–29.2, 19.7–22.1 and 18.4–18.6 kg N ha^–1, respectively. However, the transfer of residual N from these legumes to the succeeding maize crop was 18.4–20.0, 19.5–29.9, 12.0–13.7 and 9.3–10.3 kg N ha^–1, respectively. Four years of continuous lablab cropping resulted in yields and N uptake of the succeeding maize crop grown without fertilizer N that were comparable to the yields and N uptake of the succeeding maize crop supplied with 40–45 kg N ha^–1 and grown after 4 years of continuous sorghum cropping. It may therefore be concluded that nodulating soybean, lablab, green gram and black gram may be either intercropped or grown in rotation with cereals in order to economize the use of fertilizer N for maize production in the Nigerian savannah.     

Variability and Correlations in Grain Sorghum Genotypes (Sorghum bicolor [L.] Moench) Under Drought Conditions at Different Stages of Growth

Twenty-two genotypes of grain sorghum were grown under drought conditions by omitting one irrigation during stages of before flowering period, kernel filling period, and physiological maturity period at Assiut Univ. Farm in 1987 and 1988 seasons. The results obtained revealed that considerable variation existed among genotypes for all the studied traits. The most effective moisture stress treatment in reducing grain yield, panicle weight and plant height was during flowering stage. While 1000-kernel weight was much affected by moisture stress during grain filling period. The genotype x year interaction (σ²_gy) was large compared to genotype x irrigation treatment (σ²_gl) indicated that genotypes responded differently when they were grown from year to year. The genotypic variance (σ²_g) for all traits were large reflecting the importance of genetic variability. Both phenotypic and genotypic correlations among traits showed that plant height and 1000-kernel weight were highly correlated with grain yield, while leaf area index was low associated with plant height.     

Interactive Effect of Nitrogen and Sulphur on Growth and Yield of Rape-seed-Mustard (Brassica juncea L. Czern. and Coss. and Brassica campestris L.) Genotypes

A simple randomized field experiment was conducted to assess the growth and yield of rape-seed-mustard in relation to sulphur and nitrogen interaction. Three levels of sulphur (0, 40 and 60 kg ha⁻¹) in combination with three levels of nitrogen (60, 100 and 150 kg ha⁻¹) were tested as treatments, T₁, T₂, T₃, T₄, and T₅. Results indicated significant favourable effects of sulphur and nitrogen, when applied together, on yield components, seed and oil yield. Maximum response was observed with treatment T₃ (having S and N of 40 and 100 kg ha¹, respectively). Percentage oil content of seed was maximal at T₄ (having S and N of 60 and 100 kg ha¹) in both cultivars. The increase in N dose from 100 to 150 kg ha⁻¹ without any change in applied S, i.e. 60 kg ha¹ (T₅), decreased the percentage oil content. The seed and oil yield, however, were similar to T₃. Favourable responses of S and N interaction on leaf area index, rate of photosynthesis and biomass production were also observed.     

Assimilation, Dissimilation and Accumulation of 14C in Two Maize (Zea mays L.) Hybrids of Different Drought Tolerance

The effects of exposure in the vegetative phase of growth to 5- or 10-day spells of soil drought (30% field water capacity) on assimilation, dissimilation and accumulation of ¹⁴C and on dry matter growth were studied in two maize hybrids, nos. 8344 and 8388 (Garst Seed Co.) of high and low drought tolerance. Under control water regime in soil there was no difference in ¹⁴CO₂ uptake and dry matter growth between hybrids. After five days of drought ¹⁴CO₂ assimilation dropped by about 75% referred to unit weight of dry matter in hybrid 8344 and by 56% in hybrid 8388. After 10 days of drought ¹⁴CO₂ assimilation rate was reduced by 75% in both hybrids. Soil drought increased the ¹⁴C dissimilation. There were no significant differences between hybrids in all treatments, with the exception of 5 days drought; after this treatment the dissimilation rate of hybrid 8344 was higher than that of 8388. Changes of translocation of ¹⁴C and its accumulation in particular organs occurred in drought treated plants; the amount of ¹⁴C accumulated in roots of plants of hybrid 8344 increased, while that of hybrid 8388 decreased. Changes of ¹⁴C accumulation in roots were positively correlated to changes of dry matter of those organs. One day after 10 days of drought assimilation and dissimilation rates in both hybrids were about 60% of controls.     

Interactive Effects of Salinity and Biological Nitrogen Fixation on Chickpea (Cicer arietinum L.) Growth

The effect of salinity on the nodulation, N-fixation and plant growth of selected chickpea- Rhizobium symbionts was studied- Eighteen chickpea rhizobial strains were evaluated for their growth in a broth culture at salinity levels of 0 to 20 dS m⁻¹ of NaCl + Na₂SO₄. Variability in response was high. Salinity generally reduced the lag phase and/or slowed the log phase of multiplication of Rhizobium. Nine chickpea genotypes were also evaluated for salt tolerance during germination and early seedling growth in Petri dishes at five salinity levels (0–32 dS m⁻¹). Chickpea genotypes ILC-205 and ILC-1919 were the most salt-tolerant genotypes. The selected rhizobial strains and chickpea cultivars were combined in a pot experiment aimed at investigating the interactive effect of salinity (3, 6 and 9 dS m⁻¹) and N source (symbiosis vs. inorganic N) on plant growth. Symbiotic plants were more sensitive to salinity than plants fed mineral N. Significant reductions in nodule dry weight (59.8 %) and N fixation (63.5 %) were evident even at the lowest salinity level of 3 dS m-¹. Although nodules were observed in inoculated plants grown at 6 dS m-¹, N-fixation was completely inhibited. The findings indicate that symbiosis is more salt-sensitive than both Rhizobium and the host plant, probably due to a breakdown in one of the processes involved in symbiotic-N fixation. Improvement of salinity tolerance in field grown chickpea may be achieved by application of sufficient amounts of mineral nitrogen.     

Effect of Sowing Season and Seeding Rate on the Morphological Traits and Yields in Pea Cultivars of Differing Leaf Types

Determination of optimal N-fertilization rates, N_OR , for crop production that minimize risk of environmental degradation require accurate application of a response model. Several models are available to describe crop yield response to N fertilization. The objective of this work was to compare the relative accuracy of a quadratic, f(N _Q), a modified Mitscherlich, and tanh( N ) models on 48 data sets. Data were collected from a Tara silt loam (fine-silty, mixed, frigid Pachic Udic Haploboroll) over a 6-year period using two maize ( Zea mays L.) hybrids and four tillage treatments, mouldboard plough, chisel plough, ridge tillage and no-tillage. In about one-third of the cases, all models performed about equally well. Generally, the tanh( N ) and modified Mitscherlich models gave better fit between N rate and grain yield data. The N_OR, ranged from about 140 to 170 kg ha⁻¹ for the modified Mitscherlich model, 136 to 184 kg ha⁻¹ for the tanh( N) function, and 124 to 173 kg ha⁻¹ using the f(N _Q) model. Estimated grain yields at these rates ranged between 6.58 ± 1.30 to 7.59 ± 1.69 Mg ha⁻¹ for the 90-day Minnesota maturity rated (MR) hybrid and between 7.52 ± 2.40 to 8.72 ± 1.70 Mg ha⁻¹ for the 95-day MR hybrid.     

Differences between Maize Cultivars in Yield Formation, Nitrogen Uptake and associated Depletion of Soil Nitrate

In a 3-year field experiment conducted on a Gleyic Luvisol in Stuttgart-Hohenheim, ten maize cultivars (nine commercial and one experimental hybrid) were compared in their ability to utilize a high soil nitrogen (N) supply. Total N content of the shoots at about silage maturity ranged from 213 to 328 kg N ha⁻¹ (1986), from 177 to 223 kg N ha⁻¹ (1987) and from 185 to 226 kg N ha⁻¹ (1988). In all three experimental years, total shoot N uptake was significantly positively correlated to stover yield, and also to N concentrations in the ears and in the total plant dry matter. In contrast, a negative correlation between ear yields of the cultivars and total N uptake was indicated. Differences between the cultivars in N uptake were reflected in a corresponding soil nitrate depletion. At harvest, residual nitrate-N in the 0–90 cm soil layer ranged from 34–63 kg N ha⁻¹ m 1987 and 32–71 kg N ha⁻¹ in 1988. The results indicate, that growing of cultivars selected for high N uptake-capactiy of the shoots may contribute to an increased utilization of a high soil N supply and thus to a reduction of nitrate leaching.     

Intercropping Maize with Climbing Beans, Cowpeas and Velvet Beans

When one of the crops is a legume, intercropping has potential to reduce fertilizer nitrogen (N) needs and increase food quality. Total dry matter (DM) and grain yields of different plant populations of intercropped maize ( Zea mays L.) and climbing beans ( Phaseolus vulgaris L.), cowpeas ( Vigna unguiculata [L.] Walp.), or velvet beans ( Mucuna pruriens [L.] DC. var utilis [Wight] Bruck.) were compared in two experiments. Maize populations were 40,400 and 50,500 plants ha⁻¹ in combination with climbing bean populations of 0, 20,200, 40,400 and 80,800 plants ha⁻¹ in Experiment 1. In the second experiment, climbing beans, cowpeas and velvet beans at 215,200 plants ha⁻¹ were intercropped with maize at 64,600 plants ha⁻¹. Climbing beans contributed up to 5% to total DM yields in the first experiment. In the second experiment legume contributions to total DM were 20% for climbing beans, 12% for cowpeas and 8% for velvet beans. Increasing populations of maize and climbing beans increased grain and DM yields. Dry matter yield of maize was lowered by intercropping. However, DM yields of the intercrop were not different to maize sole cropped. Maize/cowpeas produced more total DM than maize/climbing beans. Cowpeas increased the total yield of crude protein by over 15% without lowering total DM yield of the intercrop compared to maize alone and are promising as a legume for intercropping with maize. Climbing beans show little promise as a possible legume for intercropping with maize.     

Morphogenetic Effects of Different Mineral N-compounds on Roots of Maize (Zea mays L.), Spring Barley (Hordeum vulgare L.) and Broad Bean (Vicia faba L.)

Plants of maize ( Zea mays L.), spring barley ( Hordeum vulgare L.) and broad bean ( Vicia faba L.) were raised in tubes filled with a soil-sand mixture and supplied with nutrient solution. The nutrient supply was varied with regard to concentration and typ of compound of "N". Due to the relatively high concentrations of "N", dry matter of shoots and roots was reduced in comparison to the control; root morphology was affected in terms of root length and root thickness. The N-compounds, used in the experiment, exerted quantitatively different influences on dry matter production and root morphology, NH₄NO₃ being the N-form which had the weakest detrimental effects. There was no specific response to NH⁺₄ or NO⁻₃ but a strong influence could be shown for NH₄Cl and N_aNO₃. Probably not only the concentration of "N" and the form of "N" have a specific influence, but also the cations and anions associated with the N-containing ion are effective.     

Response of Mustard (Brassica juncea L.) to Applied Nitrogen with or without Ethrel Spray under Non-irrigated Conditions

Field studies were conducted during the winter seasons of 1995–96 and 1996–97 at the Agricultural Farm of Aligarh Muslim University, Aligarh, India on mustard ( Brassica juncea L. Czern & Coss., var. Alankar) under non-irrigated conditions, to evaluate the effect of foliar spray of 200 p.p.m. ethrel (2-chloroethyl phosphonic acid) at flowering growth stage along with basal 0, 40, 80 or 120 kg N ha⁻¹ on net photosynthetic rate (P_N), stomatal conductance (C_S), stomatal resistance (R_S), leaf K content, relative water content (RWC), leaf area index (LAI) and total dry matter (TDM) production monitored at 20 days after spray application, and plant N content, seed N content, nitrogen harvest index (NHI), nitrogen yield merit (NYM), pods plant⁻¹, 1000 seed weight, seed yield, biological yield, harvest index (HI), seed yield merit (SYM) and merit of genotype (MOG) at harvest. Results indicated that, at 0 or 40 kg N ha⁻¹, ethrel did not produce any significance effect, but at basal 80 kg N ha⁻¹, ethrel affected the parameters favourably with the exception of 1000 seed weight, HI, seed N and NHI. Ethrel-sprayed plants utilized N from the soil more effectively and showed increased NYM. Yield attributes, seed yield and merit of genotype (in terms of NYM and SYM) were also enhanced. Ethrel spray enhanced seed yield under water stress conditions mainly by increasing K uptake and retaining higher RWC, thereby decreasing R_S and increasing LAI, P_N and TDM production.     

Seasonal Changes in the Photosynthetic Capacity of Winter Rape Plants under Different Nitrogen Regimes Measured in the Field

Winter rape (cv.'Falcon') grown under different nitrogen regimes (N₀, N₁₂₀; 0 and 120 kg.ha⁻¹, respectively) in northern Germany was investigated over the 1996 spring–summer season. Using a CO₂, H₂O diffusion porometer, diurnal courses or net photosynthesis and respiration were measured in situ and were related to microclimatic conditions and leaf water relations. Photosynthesis was modelled and daily CO₂ gain was calculated. In contrast to the N₁₂₀ plants, plants of the low nitrogen plot (N₀) grew less densely and their leaves behaved more like sun leaves. Increased nitrogen supply had little influence on photosynthetic capacity but it increased productivity through higher leaf area index and an extended period of photosynthetic activity. N₁₂₀ plants also appeared to be better acclimated to hot, summer conditions. Higher nitrogen supply substantially increased seed production with the yield of the N₁₂₀ plants being 16% of the N₀ plants.     

Effect of Gibberellic Acid Spray and Basal Nitrogen and Phosphorus on Productivity and Fatty Acid Composition of Rapeseed-Mustard

Two field experiments were conducted during] 994-95 to study the effect of spray of 10⁻⁵ M GA3 at 40 days after sowing on mustard ( Brassica juncea (L.) Czern & Coss.) cv. Varuna grown with basally applied 0, 40, 80 and 120 kg N ha⁻¹ (Expt. 1) and 0,15, 30 and 45 kg P ha⁻¹ (Expt. 2) on pod number per plant, seeds per pod, 1000 seed weight, seed yield, biological yield, harvest index and fatty acid composition of oil. No significant difference between water and GA3 spray was found when basally applied nitrogen was 0 or 40 kg N ha⁻¹. N₈₀ proved to be the best for yield characteristics. In another experiment on phosphorus, GA₃ and 30 kg P ha⁻¹ individually enhanced the yield, but interaction of GA₃ and P remained non-significant. The fatty acid composition of oil in both experiments was significantly affected only by nitrogen and phosphorus treatments for oleic acid and erucic acid. It was found that return in the form of yield was more for every kg applied fertilizer under GA, spray treatment. The response was more for N fertilizer in comparison to P. GA₃ at a low level of fertilization significantly increased the return from fertilization.