Increase In Number Of Pods Research Articles

Differential Response of Soybean Yield Components to the Timing of Light Enrichment

Solar radiation is an important environmental factor influencing seed yield in soybean [Glycine max (L). Merr.]. Our objective was to analyze the response of soybean seed yield components to light enrichment initiated at different growth stages. Light enrichment was imposed on the indeterminate soybean cultivars Altona and Evans by installing wire mesh fencing on either side of the center row to push the adjacent rows aside at different growth stages. Fences prevented plants in the neighboring rows from encroaching on the growing space of the center row plants. Pod number per plant and to a lesser extent seed size accounted for variation in seed yield. Light enrichment initiated at late vegetative or early flowering stages increased seed yield 144 to 252%, mainly by increasing pod number, while light enrichment beginning at early pod formation increased seed size 8 to 23%, resulting in a 32 to 115% increase in seed yield. Responses to light enrichment occurred proportionately across all node positions despite the differences in the time (15–20 d) of development of yield components at the different node positions. Although maximum seed size may be under genetic control in soybean plants, our results suggested seed size can still be modified by the environment with some internal control moderating the final size of most seeds in all pods. It indicates that plants are able to redistribute the available resources to components not yet determined, in an attempt to maintain or improve yield.

Yield components of soybean plants infected with soybean cyst nematode and sprayed with foliar applications of boron and magnesium1

Investigations into the effect of soybean cyst nematode (SCN, Heterodera glycines, Ichinoe) on the yield components of soybean [Glycine max (L.) Merr.] have shown that pod numbers are reduced with increasing SCN initial populations (Pi) present in the soil at planting. The main method by which SCN alters pod numbers is through reductions in the number of branches per plant. Foliar applications of boron (B) and B in combination with magnesium (Mg) (B+Mg) increase yield of soybean not infected with SCN by increasing pod number per plant, especially the number of pods on branches. The objective of this research was to determine if foliar applications of B and B+Mg ameliorates the effect of SCN by increasing yield on branches. Field experiments were conducted in 1993 and 1994 in 1 m2 microplots to compare foliar applied B and B+Mg to a control treatment. Foliar applications were made at four intervals spaced throughout soybean reproductive development of Pioneer brand 9391, an SCN susceptible cultivar. There were 12 levels of SCN Pi in 1993 and 11 levels in 1994. For each treatment, including control, grain yield was regressed on SCN Pi. Yield was reduced with increasing SCN Pi in both years, but the rate of decrease did not differ among treatments. In addition, ANOVA of yield components revealed no treatment effects on the number of branches per plant, the number of branch pods per plant, or the total number of pods per plant. Thus, foliar applications of B or B+Mg did not ameliorate the effects of SCN on soybean.

Polyamines as Modulators of Soybean Productivity

AbstractPolyamines have been shown to be involved in several aspects of plant growth and development. In soybean, increase in number of pods per plant, 100 seed weight, seed, biological and oil yield was highest with spray of spermine and lowest (but significantly higher than control) with putrescine. The soybean seed and oil yield increased by about 12.46 and 20.94% respectively with application of 10−3m spermine at 50% flowering stage. Another spray of polyamines at pod initiation stage had little effect on different parameters.

Heterosis in Spring Canola Hybrids Grown in Northern Idaho

Spring canola acreage has increased in the Pacific Northwest over the past 5 yr. Traditional cultivars are inbred lines, although a high proportion of newer cultivars are hybrids. This study examined the magnitude of heterosis in spring canola to determine the potential advantage of hybrid cultivars. Four inbred cultivars, with diverse geographic origins of development, were hand-pollinated in a diallel design. Performance of F1 hybrids and their respective inbred parents was evaluated under greenhouse conditions. Field trials were conducted at two locations to compare F1 hybrids and F2 progeny with inbred parents. Positive heterosis was found for yield, oil content, and oil quality, with the highest degree of heterosis observed for yield. Hybrids and F2 progeny produced higher yield than inbred parents because of increased pod number (primarily on the main raceme), larger seeds, and later maturity. However, the magnitude of heterosis observed varied between hybrids. Inbred and hybrid cultivars also were compared in the Pacific Northwest Regional Canola Variety Trials. In these trials, the most adapted hybrids had a yield advantage compared with the most productive inbred cultivars. However, average yield and oil content of hybrids were not significantly different from inbred cultivars. Inbred cultivars tended to have higher oil content and matured earlier. Introduction of hybrid canola cultivars in the Pacific Northwest region has potential to increase canola acreage and grower profit. However, choice of hybrid parents and economics of high quality hybrid seed production will be important factors in hybrid canola cultivar development and acceptance.

Effects of Isolation Treatment of a Node on Flowering and Pod Set in Field Grown Soybean.

By pruning the top above the 12th node of the main stem and removing all of the leaves, petioles and floral organs except that on the 12th node at the beginning of flowering, the 12th node was isolated to investigate the effect of higher assimilative supply on the sing-determining process of soybean. Treatment caused an elongation of flowering duration due to the promotion of floral differentiation at the 12th node and produced 36 floral buds, which was three times more than that of the control. Treatment also increased the differentiation of the upper racemes with compound leaves. Although the pod setting ratio increased at the first-order raceme as a result of the treatment, there was only a small difference in that on the upper racemes between the plots. The isolated node produced a seed yield threefold as compared to the control due to the increase in pod number and seed size. These results indicated that potential sink-capacity in each node of the soybean plant is extremely large and elastic, and racemes with compound leaves play an important role for the process of sink determination. A slight increase in pod setting ratio makes clear the precedence of floral differentiation in the sink adjusting process.

The response of dryland canola to nitrogen fertilizer: partitioning and mobilization of dry matter and nitrogen, and nitrogen effects on yield components

Canola ( Brassica napus) was grown under dryland conditions in field experiments at Greenethorpe (1988) and Canowindra (1989) in the cereal belt of New South Wales to determine (1) the response of the crop to nitrogen (N) fertilizer when grown late in a cropping sequence; (2) the seasonal course of dry-matter production and N accumulation; (3) the distribution of dry matter and N among plant parts, including shed leaves; and (4) the apparent mobilization of dry matter and N from stems and leaves to seeds. At both sites, maximum dry-matter production and seed yields occurred at 75 kg applied N ha −1. Seed yields increased from 2.3 to 3.5 t ha −1 at Greenethorpe, and from 0.85 to 2.5 t ha −1 at Canowindra. Topdressing with a single application of N at the 5–6 leaf rosette stage, flower buds visible or the start of flowering resulted in 70–90% of the seed yields obtained when the equivalent amount of N was applied pre-sowing. At maximum seed yield, canola accumulated 165 kg N at Greenethorpe and 110 kg N ha −1 at Canowindra. Averaged over both seasons and all N treatments, 52% of the N content of the mature plants accumulated before flowering and 50% of the dry-matter content of the mature plants accumulated during flowering. Maximum dry-matter and N contents for leaves occurred at the start of flowering, and for the stem at the end of flowering. Averaged over all N treatments at Greenethorpe, about 20% of the dry matter and 60–65% of the N was apparently mobilized from the stem and leaves, after flowering. The combined mobilization from the stem + leaves could have contributed to about 17% of the dry matter and 55% of the N accumulated by seeds. Amounts of dry matter and N lost in shed leaves ranged from 1-1.75 t and 10–30 kg ha −1, and N removal in seed ranged from 63–112 and 27–96 kg ha −1 at Greenethorpe and Canowindra, respectively. N concentrations in whole shoots and vegetative organs declined during the season, irrespective of the rate of N fertilizer applied. N fertilizer increased pod number per plant but had little effect on seed number per pod or 1000 seed weights. Seed oil concentrations were unaffected by the N rate at which maximum seed yield was obtained. N fertilizer rate had no effect on dry-matter harvest indices (mean both sites 30%) which, when expressed on the basis of the biosynthetic costs for straw and seed production, were comparable to those reported for wheat (37%). N harvest indices (mean both sites 76%) were reduced only at the highest N rates at Greenethorpe. Indices of N fertilizer use-efficiency generally decreased with increasing N fertilizer rate, and were similar to values reported for wheat when differences in the biosynthetic cost of grain production were taken into account.

Nodulation, Nitrogen Fixation and Growth of Soybean Plants(Glycine max Merr.) in Soil Supplemented with Chitin or Chitosan.

Pot soil was supplemented with varying concentration of chitin or chitosan to investigate their influence on the nodulation, nitorgen fixation and growth of soybean plants. Significant (P=0.05) reductions in nodule fresh weight and nitrogen fixaton (measured as acetylene-reduction activity) were observed at the early growth stage (28 DAP) for plants grown in soil supplemented with chitin or chitosan as compared to regular pot soil. However, the nodule numbers were not affected at the early growth stage with the exception of 1% of chitin or chitosan. Both nodulation and nitorgen fixation activity at a later growth stage (42 DAP) were markedly enhanced in soils supplemented with 0.10% of either chitin or chitosan. These results suggest that all concentrations of chitin or chitosan have a severe influence on nodule development and N2-fixation activity at the early growth stage in soybean plants. The production of total dry matter was higher in untreated control plants at 28 DAP, while plants treated with 0.10∼0.25% chitin or chitosan produced higher dry matter at 42 DAP. Soybean seed yield increased with the increasing pod number at these levels of treatment. However, the above parameters did not differ greatly between chitin and chitosan at corresponding levels of concentration.

Growth Dynamics during the Vegetative Period Affects Yield of Narrow‐Row, Late‐Planted Soybean

AbstractNarrow‐row culture is recommended for increasing soybean [Glycine max (L.) Merr.] yield at late plantings in the southeastern USA. Increased pod number resulting from greater light interception (LI) and crop growth rate (CGR) during the early reproductive period [first flowering to seed initiation (R1 to R5)] is mainly responsible for narrow‐row yield increases. However, little is known about rowspacing effects on Ll, CGR, and other growth dynamic parameters during the vegetative period [emergence (E) to R1] and how these parameters affect yield. Our objectives were to determine when LI and CGR differences in narrow vs. wide rows appear during E to R1, to determine if these differences contribute to narrow‐row effects on CGR(R1 to R5), and to determine the roles of leaf area index (LAI) and light interception efficiency (LIE = LI/LAI) in causing narrow‐row LI increases during the vegetative period. Seed of ‘Centennial’ soybean (Maturity Group VI) was planted in mid‐July in 1992 and 1993 at Baton Rouge, LA, on a Commerce silt loam soil (fine‐silty, mixed, nonacid, thermic Aeric Fluvaquent). Experimental design was a randomized complete block in a split‐plot arrangement. Main plots were row spacings of 100, 50, and 25 cm. Split plots were eight sampling dates during E to R5. The CGR(R1 to R5) advantage of narrow‐row culture developed from CGR advantage in the vegetative period, caused by greater LI originating from increased LIE during the first 26 d of the vegetative period. Yield was significantly correlated with CGR during most of the vegetative period. In conclusion, source strength (CGR) during the vegetative period was shown to affect yield at late planting dates.

A Criterion for Acceptance of Narrow‐Row Culture in Soybean

AbstractSoybean [Glycine max (L.) Merr.] yield response to narrow compared with wide rows in the southeastern USA has usually been greater for late than for optimal plantings. Identification of growth responses explaining this pattern could help develop criteria for acceptance of narrow‐row culture. Narrow‐row yield responses result from increased pod number created by greater light interception and crop growth rate between first flowering and seed initiation (R1 to R5). Lack of yield response to greater light interception in narrow rows in optimal plantings may be related to the association between pod number and total dry matter at harvest maturity (R8). Our objectives were to determine if total dry matter at R8 [TDM(R8)] could be used as a criterion for acceptance of narrow‐row culture and to identify the morphological relation between pod number and TDM(R8). Field studies conducted in 1987 through 1990 used optimal and late planting dates, two soybean cultivars, and several row spacing‐plant density combinations. Results indicate a quadratic response of pod number to TDM(R8). Narrow‐row yield responses occurred when light interception (R1 to R5) increased crop growth rate (R1 to R5) to ≤ 15 g m−2 d−1 and increased TDM(R8) to ≤ 800 g m−2. The ratio of pod number to TDM(R8) declined as TDM(R8) approached 800 g m−2, because of a reduced ratio of branch nodes to branch dry matter. In conclusion, narrow‐row yield responses can be expected if TDM(R8) in wide rows is <800 g m−2.

Okra production with pine straw mulch

Conventional planted okra in Booneville, Arkansas and Lorman, Mississippi were mulched with loblolly pine straw (Pinus taeda L.) and longleaf pine straw (P. palustris Mill.), respectively, at a rate of 11 t/ha or left bare. At Booneville, plant stand, season yields (18.6 t/ha), pod weight (16.3 g), plant dry weight (2.3 kg), or stem diameter (3.5 cm) were not affected by the loblolly pine mulch. However, mulch application increased pod number (1.22 vs. 1.06×106/ha) and plant height (1.5 vs. 1.6 m), while reducing weed competition (0.05 vs. 0.40 t/ha) and visible plant stress, during periods of soil moisture deficits. Soil temperatures at 5 and 15 cm depth were reduced by mulch until mid-August when plant canopies covered the rows. Seasonal moisture at 30 and 45 cm depths was similar between mulched and bare soils, based upon unreplicated neutron probe measurements. At Lorman, season okra yield (29.8 vs. 24.6 t/ha), number of pods per ha (1.24 vs. 1.07×106) and weed competition were reduced and soil pH lowered 0.56 units by longleaf pine straw mulch. Mulch reduced early season yield at both locations.

Compensatory Growth Responses During Reproductive Phase of Cowpea after Relief of Water Stress

AbstractUnpredictable drought affects growth and yield of dryland cowpea (Vigna unguiculata [L.] Walp.) during rainy season. With the objective of identifying compensatory growth responses after relief of water stress, pot‐grown plants (cv. C‐752) were water‐stressed at flowering, and physiological responses, short term dry matter partitioning upon relief of water stress, and productivity at maturity were studied. Water stress decreased, to varying degrees, leaf water potential, stomatal conductance, photosynthesis rate and transpiration rate. Recovery in assimilation lagged behind that in water relations. Assimilate supply seemed to be limiting early pod growth upon relief of water stress due to low photosynthesis rate, reduced leaf area per pod, and increased partitioning to leaf expansion. However, later pod growth was not limited by assimilate supply and final dry matter per pod was similar in both non‐stressed and stress‐affected plant. Cowpea exhibited the following growth responses during pod‐fill stage upon relief of water stress: 1. increase in leaf area, 2. shift in dry matter partitioning in favour of leaf expansion, 3. extended green leaf duration, and 4. increase in pod number. These partially compensating physiological responses probably ensure reasonable productivity of dryland cowpea during rainy season.

Soil Acidity and Liming Effects on Stand, Nodulation, and Yield of Common Bean

AbstractThe area planted to common bean (Phaseolus vulgaris L.) has been declining in the Southern Mexican State of Chiapas. To determine factors limiting bean productivity in this region, on‐farm experiments were conducted at four locations. Soils were Acrisols (Ustults) at two sites and a Cambisol (Tropept) and Phaeozem (Ustoll) at the other two sites, with pH (H2O) of unlimed soil from 4.6 to 5.0. Insecticide application, genotype, and lime were treatments in a split‐plot design with a factorial combination of two genotypes and 0 or 2000 kg Ca(OH)2 ha−1 as subplots. Across sites, lime addition raised soil pH by 0.4 to 1.3 units, decreased Al saturation by 13 to 38%, and increased extractable Ca two‐to three‐fold. Mean yield without lime was 444 kg ha−1 ha. Insecticide and bean genotype had negligible effects on yield. Lime application resulted in a yield increase of 76 to 313% above unlimed controls across locations. Liming resulted in 40% greater shoot and 18% greater root dry weight, and also improved nodule weight per plant by 110% at early flowering. At maturity, plant density in limed treatments was 23% higher than in unlimed controls, and counts made during the season indicated that soil acidity factors inhibit seedling establishment. Liming also increased pod number per plant by 67%, seed number per pod by 18%, and seed weight by 7%. Increased yield from lime therefore resulted from better stand establishment, and increased seed yield per plant. Increased nodulation and N2 fixation may also contribute to the response to lime.

Soybean Pod Set Enhancement with Synthetic Cytokinin Analogs

The previously reported activity of benzyladenine and selected other cytokinin analogs to increase pod set in soybean (Glycine max [L.] Merr.) was further investigated to define the structure-activity relationship and evaluate the effects of the cytokinins on yield parameters. Enhancement of pod set was found to be greatest with N-6 saturated alkyl substituted analogs, and was only weakly associated with activity in a callus growth bioassay. The response of yield parameters to increasing pod load was evaluated by applying various cytokinin analogs having a range of pod set enhancement activity. The increased pod load at the treated nodes was not compensated by a reduction in pod number on the remainder of the plant. However, there was a compensatory decrease in seed size. Overall, a significant trend to greater total seed weight per plant was associated with the increased pod number. Initial evaluations indicated that foliar applications of select cytokinins could temporarily increase pod number. However, the increases in pod number obtained with foliar treatments were too small to be of practical utility and were not maintained to maturity.

The Physiological Basis for Cytokinin Induced Increases in Pod Set in IX93-100 Soybeans

Previous investigations have shown the feasibility of increasing pod number on legumes by the application of 6-benzylaminopurine (BA) directly to the raceme. These investigations were designed to determine what reproductive parameter was affected by cytokinin application, and if these applications were overcoming a deficiency in root-produced cytokinins during late flowering. Five individual main stem racemes on greenhouse grown soybeans (Glycine max L. Merr.) were treated with 2 millimolar BA. A single application of BA when pods appeared at 25 to 50% of the proximal floral positions resulted in a 58% increase in pod set due primarily to a 33% reduction in floral abscission. Applications of BA at later intervals also resulted in significant reductions in total abscission. When three applications of BA were imposed on the upper five nodes of field grown soybeans, total pod number and seed weight were significantly increased in this section of the canopy by 27 and 18%, respectively. Throughout the flowering period, root pressure exudate was sampled for the subsequent separation and quantification of zeatin, dihydrozeatin, zeatin riboside, dihydrozeatin riboside, and isopentenyladenine. Total cytokinin flux peaked from 0 to 9 days after flowering began, and then dropped to one-half of this level by 15 days postanthesis. The probability that a flower would initiate a pod was directly related to the concentration of total cytokinins present in the exudate when the flower opened.

Effects of sowing date on the growth, yield and quality of okra (Abelmoschus esculentus (L.) Moench.) in southern Nigeria

SUMMARYTwo varieties of okra were sown at approximately 14-day intervals from 1 April to 1 June for 2 years during the main rainy season in Nigeria. Low soil temperature and moisture, which resulted from a combined effect of high solar radiation, high atmospheric temperature and low rainfall, led to poor seedling emergence at the early sowing dates.The growth of the fewer plants of the early sowing dates were more vigorous than those of later sowing dates and they attained 50% flowering earlier and had a longer harvest duration. This resulted in increases in number of pods per plant, pod length, pod diameter, pod volume, pod weight and pod yield per ha, indicating compensatory growth by the fewer plants in the early plantings. The relatively lower values obtained for these variables with the late sowing dates were also attributed to possible poor soil aeration arising from the increased rainfall during their growth period.Sowing dates did not generally affect the percentage moisture, oil and protein in the pods. The effects of varieties on the variables measured were more uniform than those of sowing dates and mostly not significant.

Oviposition and development of Bruchidius atrolineatus (Pic) and Callosobrochus maculatus (F.) (Coleopterae: Bruchidae) in Vigna unguiculata (Walp) cultures in Niger

Bruchidius atrolineatus (Pic) is present in crops of Vigna unguiculata towards the end of the dry season at the beginning of September when pods start to form. Females lay many eggs on most available green pods. However, this oviposition behaviour results in an important egg mortality. During September, pods gradually reach maturity whilst new pods are formed. Females therefore have at their disposal a growing number of differently mature pods. Confronted with such a situation, B. atrolineatus females show an opportunist behaviour and lay most of their eggs on the most abundant stage, i.e. the most easily discovered stage (ripening green pods in mid-September or dry pods towards the end of September). However, they also lay eggs on other phenological stages no matter how abundant they are. B. atrolineatus females therefore show a certain behavioural plasticity enabling them to reproduce on all stages of pods whose maturity, chemistry and texture may differ. Larvae can develop either in maturing or dry seeds. The number of eggs laid from mid September is lower and lower whatever the phenological stage attacked. This decrease would be due to a reduction of the first generation adult bruchids and of the reproductive potential of females. Callosobruchus maculatus appears in crops at the same time as B. atrolineatus, but oviposits preferentially on dry pods. Eggs are observed during the whole period of study, but the numbers laid are always low. With the increase in pod number, eggs are dispersed among the different substrates available. However, the average number of eggs laid on the pods remains constant. Despite the high mortality due to the oviposition behaviour of B. atrolineatus and to other factors (impact of hymenopterous parasitoids), these two bruchids cause important losses to seeds of V. unguiculata. Control methods against these pests should be envisaged.in the field before harvesting.

Effects of Morphactin and Other Auxin Transport Inhibitors on Soybean Senescence and Pod Development

Because triiodobenzoic acid increases pod number, albeit variably, in soybean (Glycine max), we tested other auxin-transport inhibitors. Morphactins, especially methylchlorflurenol (MCF), were found to be very active (optimal concentration 10 micromolar) when sprayed onto the foliage. Applications at 1 week after the start of flowering were most effective, producing a 40% increase in pod number with little inhibition (12%) of stem elongation. MCF increased the number of pods initiated (reaching 1 cm length) at least partially by prolonging the initiation period, while pod abortion (failure of pods > 1 cm long) remained low. Generally, MCF did not increase seed yield (dry weight/plant); more, but smaller seeds, were formed by the treated plants. The promotive effect of MCF on pod initiation seems to be independent of its inhibition of stem elongation, which is insignificant at 10 micromolar. MCF delayed pod maturation by 3 to 4 days, while foliar yellowing, blade abscission, and petiole abscission were retarded by 2, 4, and 2 days, respectively. MCF has only a small effect on senescence and that could be indirect, due to a delay in pod development. Other auxin-transport inhibitors tested, including N-1-naphthylphthalamic acid, produced little or no increase in pod number; however, 0.1 millimolar 5-[2'-carboxyphenyl]-3-phenylpyrazole caused a 27% increase. These results implicate auxin as a potential regulator of pod development, and they show that soybean seed yield is not simply sink limited.

Phosphorus nutrition of peanut (Arachis hypogaea L.) on Cockatoo Sands of the Ord River Irrigation Area

Yield response of field-grown Virginia Bunch peanuts to a range of soil phosphorus levels, determined using 0.5M NaHCO3 extractant, in the top 10 cm of the soil profile was evaluated on Cockatoo Sands of the Ord River Irrigation Area. Critical levels of soil phosphorus (required to attain 90% of maximum yield recorded in fertilized plots) was 7.3 ppm for pods and 7.9 ppm for kernels. Yield increases obtained with higher soil phosphorus status were due to increased pod number and kernel size. Trends in tissue phosphorus concentration in uppermost fully expanded leaves were monitored during the season, and critical concentrations for 90% of maximum pod yield were derived. The critical concentration (0.30% P, dry-weight basis) did not change with time during the vegetative phase of development, but declined in a linear fashion over time during reproductive development, from 0.27% P at 60 days after emergence to 0.12% P at 100 days after emergence.

Response of rapeseed (Brassica napus) to phosphorus, boron and lime on an acid soil near Canberra

The failure of a rape crop on a light-textured acid soil was investigated by a factorial field experiment with four rates of lime (0, 500, 1000 and 2000 kg/ha), four rates of phosphorus (0, 13, 28, 42 kg/ha) and, at stem extension, two levels of a boron spray (0, 0.6 kg/ha). The second crop failed in the same way as the first unless phosphorus was applied at sowing; the lowest rate was adequate, and higher rates did not increase the response. On the phosphate-treated plots the boron spray increased seed yield (measured on hand-harvested quadrats) substantially (75%) as the result of a small increase in flower number (32%) and a large increase in pod number (1 16%). Machine-harvested yields on the 'plus boron' plots were reduced by shattering and were 40% higher than controls (P<0.01). There was no response to lime applied one month before sowing and no interaction of lime with boron or phosphorus. The boron response was not lime-induced. The mechanism of the response to phosphorus and the questions raised by the lack of response in yield to lime in relation to aluminium and manganese toxicity were not resolved. The results indicate that phosphorus should receive at least as much attention as lime in the investigation of rape-growing on acid soils. Boron should also be investigated because of its important role in seed set of rape.

Effect of two granular nematicides on growth and nodulation ofArachis hypogea L.

The effect of two granular nematicidesviz. oxamyl and fenamiphos, on the nodulation and growth of Rhizobium inoculatedArachis hypogaea L. was studied in glasshouse and field trials. In the glasshouse trial at the suggested rates of application shoot fresh weight was significantly reduced by oxamyl whilst root fresh weight was similarly affected by fenamiphos. In the field trial vegetative growth and plant emergence were significantly reduced by both nematicides. Nodulation at the higher rates of application was increased by both oxamyl and fenamiphos whilst oxamyl caused a significant increase in pod number at the highest rate of application.