Foliar application of molybdenum in common beans. I. Nitrogenase and reductase activities in a soil of high fertility

Although common bean (Phaseolus vulgaris L.) has a good potential for N₂ fixation, poor nodulation following inoculation, principally under field conditions, has led to increased nitrogen (N) fertilizer use in this crop. In the face of the negative environmental effects of N fertilizer, alternative methods have been studied to minimize the amount to be applied. In this sense, foliar application of molybdenum (Mo) has been cited as a promising method. Several papers show that high bean yields (1,500–2,500 kg ha^‐1), may be obtained in the southeasten region of Brazil, when there is an application of N as side dressing or Mo spray 25 days after plant emergence. A field experiment was carried out to verify the effect of Mo foliar application on nitrogenase and nitrate reductase activities and on bean yield. Treatments included Rhizobium inoculation (with and without), foliar application of Mo (0 and 40 g ha^‐1), N at planting (0 and 20 kg ha^‐1) and N applied as side dressing (0 and 30 kg ha^‐1). Molybdenum and N as side dressing were used 25 days after plant emergence. Molybdenum increased greatly the nitrogenase activity and extended the period of high nitrate reductase activity, with a consequent increase in total shoot N. Increase of nitrogenase activity did not depend on inoculation, showing that soil native rhizobia may increase in effectiveness when appropriately handled. Bean yield did not differ significantly when fertilized with either Mo or N as side dressing.     

Foliar application of molybdenum in common bean. II. Nitrogenase and nitrate reductase activities in a soil of low fertility

Foliar application of molybdenum (Mo) at 40 g ha^‐1 25 days after plant emergence greatly enhanced nitrogenase and nitrate reductase activities of common bean (Phaseolus vulgaris L.), resulting in an increase in total nitrogen (N) accumulation in shoots. Application of 20 kg N ha^‐1 as ammonium sulfate [(NH₄)₂SO₄] at sowing decreased nodulation and nitrogenase activity. Rhizobium inoculation did not affect nitrogenase activity which demonstrated that Mo application increased the efficiency of native Rhizobia strains. Nitrogen amendment, either at planting (20 kg N ha^‐1) or as a side dressing (30 kg N ha^‐1) 25 days after plant emergence, did not affect the foliar nitrate reductase activity. Molybdenum foliar spray as ammonium molybdate [(NH₄)₆Mo₇O₂₄2H₂O] and N applied as a side dressing increased equally the total amount of N in the pods. A 10% increase in the seed N concentration was obtained with foliar application of Mo, while N applied as a side dressing had no effect on seed N concentration. An average increase of 41% in N export to the seeds was obtained by either Mo or N as side dressing. Nitrogen applied at sowing or Rhizobia inoculation had no effect on the characteristics evaluated 74 days after plant emergence. Plants that received either Mo as foliar spray or as side dressed N had similar yields. This demonstrated that, in certain soils, N fertilization may be replaced by a small amount of Mo as a foliar application.     

Effects of Rhizobial inoculant and nitrogen fertilizer on yield and nodulation of common bean

A two‐year field experiment was conducted to determine if using mixed strains of Rhizobium inoculant and starter nitrogen (N) fertilizer could improve yield and nodulation of four common bean varieties on a Vertisol at Alemaya, Ethiopia. A granular mixed inoculant of CIAT isolates 384, 274, and 632 and a starter N fertilizer at a rate of 23 kg N ha^‐1 (50 kg urea ha^‐1) were applied separately at planting. Inoculation with mixed strains and starter N fertilizer gave a significantly higher grain yield, nodule number, and dry matter yield for most varieties used. Both grain yield and dry matter yield showed a significant correlation (r=0.93 and r=0.87; P<0.05 for grain yield and dry matter yield, respectively, for 1991 crop season and r=0.90 and r=0.86; P<0.05 for grain yield and dry matter yield, respectively, for 1992 crop season) with nodule number. It is recommended that resource‐poor farmers adopt the practice of using a Rhizobium inoculant or starter N to improve common bean yields in the Hararghe highlands, Ethiopia.     

Wheat response to N2 fixed by faba bean (Vicia faba L.) as affected by sulfur fertilization and rhizobial inoculation in semi‐arid Northern Ethiopia

Nitrogen fixation in faba bean (Vicia faba cv. Mesay) as affected by sulfur (S) fertilization (30 kg S ha^–1) and inoculation under the semi‐arid conditions of Ethiopia was studied using the ¹⁵N‐isotope dilution method. The effect of faba bean–fixed nitrogen (N) on yield of the subsequent wheat crop (Triticum aestivum L.) was also assessed. Sulfur fertilization and inoculation significantly (p < 0.05) affected nodulation at late flowering stage for both 2004 and 2005 cropping seasons. The nodule number and nodule fresh weighs were increased by 53% and 95%, relative to the control. Similarly, both treatments (S fertilization and inoculants) significantly improved biomass and grain yield of faba bean on average by 2.2 and 1.2 Mg ha^–1. This corresponds to 37% and 50% increases, respectively, relative to the control. Total N and S uptake of grains was significantly higher by 59.6 and 3.3 kg ha^–1, which are 76% and 66% increases, respectively. Sulfur and inoculation enhanced the percentage of N derived from the atmosphere in the whole plant of faba bean from 51% to 73%. This corresponds to N₂ fixation varying from 49 to 147 kg N ha^–1. The percentage of N derived from fertilizer (%Ndff) and soil (%Ndfs) of faba bean varied from 4.3% to 2.8 %, and from 45.1% to 24.0%, corresponding to the average values of 5.1 and 47.9 kg N ha^–1. Similarly, the %Ndff and %Ndfs of the reference crop, barley, varied from 8.5 % to 10.8% and from 91.5% to 89.2%, with average N yields of 9.2 and 84.3 kg N ha^–1. Soil N balance after faba bean ranged from 13 to 52 kg N ha^–1. Beneficial effects of faba bean on yield of a wheat crop grown after faba bean were highly significant, increasing the average grain and N yields of this crop by 1.11 Mg ha^–1 and 30 kg ha^–1, relative to the yield of wheat grown after the reference crop, barley. Thus, it can be concluded that faba bean can be grown as an alternative crop to fallow, benefiting farmers economically and increasing the soil fertility.     

Single and double inoculation with Azospirillum/Trichoderma: the effects on dry bean and wheat

A plant growth-promoting rhizobacterium (Azospirillum brasilense Sp7) and a bio-control fungus, which can solubilize insoluble phosphorus (Trichoderma harzianum Rifai 1295-22), were evaluated for their single and combined effects on dry bean (Phaseolus vulgaris) and wheat (Triticum aestivum L.) grown in soil. A pot experiment with bean and a field experiment with both bean and wheat were established. In contrast to single inoculation of Trichoderma, the single inoculation of Azospirillum and the double inoculation did not significantly (P >0.05) increase nodule numbers and nodule mass at 45 days after planting in pot grown beans. However, the Azospirillum inoculation with supplementary phosphorus significantly (P <0.05) increased nodule mass. There were no significant (P >0.05) differences among the inoculation treatments for plant dry weight, total plant nitrogen, and total plant phosphorus at 45 days after planting in both pot and field experiments with bean. However, the combined inoculation and rock phosphate application at 1 Mg ha^–1 significantly (P <0.05) increased bean seed yield, total seed nitrogen and phosphorus in the bean field trial. This treatment more than doubled the mentioned properties compared to the control. The microbial inoculations, with the exception of the combined inoculation, significantly (P <0.05) increased total seed nitrogen, but never affected seed yield in the wheat field trial (P >0.05). The combined inoculation improves many plant and yield parameters and, therefore, has some advantages over single inoculation provided that rock phosphate was supplied at an amount not exceeding 1 Mg ha^–1. Higher rock phosphate application rates decreased many plant and yield parameters in our study.This work was carried out at Gaziosmanpaa University, Tokat, Turkey.     

The inorganic N requirement,nodulation and yield of common bean (Phaseolus vulgaris L.) as influenced by inherent soil fertility of eastern Ethiopia

Though mineral N application impaired nodulation initiation and function, it improves the productivity of common bean. The effect of inorganic application on common bean productivity, however, is dependent on the availability of plant nutrients including nitrogen (N) in the soils. Therefore, multilocation field experiments were conducted at Babillae, Fedis, Haramaya, and Hirna to evaluate the effect of inherent soil fertility status on responsiveness of common bean to different rates of N fertilizer application and its effect on nodulation, yield, and yield components of common bean. The treatments were six levels of N fertilizer (0, 20, 40, 60, 80, and 100 kg N ha^?1) laid out in randomized completed block design with three replications. The result revealed that 20 kg N ha^?1 application significantly improved the nodule number (NN) and nodule dry weight (NDW) except Hirna site, in which reduction of NN and NDW was observed. Although the remaining investigated yield and yield components were significantly improved due to N fertilizer in all study sites, 40 kg N ha^?1 application resulted in significantly increased GY of common bean at Fedis, Haramaya, and Hirna site, while 60 kg N ha^?1 at Babillae site. The highest total biomass yield (7011.6 kg ha^?1) and GY (2475.28 kg ha^?1) of common bean were recorded at Hirna and Haramaya sites, respectively, indicating the importance of better fertile soil for good common bean production. Hence, it can be concluded that the effect of inorganic N on common bean was irrespective of soil fertility rather the total amount of N in soil would affect the need of different rate of inorganic N.     

Field evaluation of N2 fixation and N partitioning in climbing bean (Phaseolus vulgaris L.) using 15N

Summary The common bean (Phaseolus vulgaris L.) is generally regarded as a poor N₂ fixer. This study assessed the sources of N (fertilizer, soil, and fixed N), N partitioning and mobilization, and soil N balance under field conditions in an indeterminate-type climbing bean (P. vulgaris L. cv. Cipro) at the vegetative, early pod-filling, and physiological maturity stages, using the A-value approach. This involved the application of 10 and 100 kg N ha^-1 of ¹⁵N-labelled ammonium sulphate to the climbing bean and a reference crop, maize (Zea mays L.). At the late pod-filling stage (75 days after planting) the climbing bean had accumulated 119 kg N ha^-1, 84% being derived from fixation, 16% from soil, and only 0.2% from the ¹⁵N fertilizer. N₂ fixation was generally high at all stages of plant growth, but the maximum fixation (74% of the total N₂ fixed) occurred during the interval between early (55 days after planting) and late podfilling. The N₂ fixed between 55 and 75 days after planting bas a major source (88%) of the N demand of the developing pod, and only about 11% was contributed from the soil. There was essentially no mobilization of N from the shoots or roots for pod development. The cultivation of common bean cultivars that maintain a high N₂-fixing capacity especially during pod filling, satisfying almost all the N needs of the developing pod and thus requiring little or no mobilization of N from the shoots for pod development, may lead to a net positive soil N balance.     

Low root zone temperature effects on bean (Phaseolus vulgaris L.) plants inoculated with Rhizobium leguminosarum bv. phaseoli pre-incubated with methyl jasmonate and/or genistein

Abstract

Methyl jasmonate (MeJA) has recently been shown to act as a plant-to-bacteria signal. We tested the hypothesis that pre-induction of Rhizobium leguminosarum bv. phaseoli cells with genistein and/or MeJA would at least partially overcome the negative effects of low root zone temperature (RZT) on bean nodulation, nitrogen fixation and plant growth. Otebo bean plants were grown at constant air temperature (25^oC) and two RZT regimes (25 and 17^oC) and inoculated with R. leguminosarum bv. phaseoli pre-induced with MeJA and/or genistein. Our results indicate that low RZT inhibited nodulation, nitrogen fixation and plant growth. The plants growing at low RZT began fixing nitrogen seven days later compared to those at higher RZT. The low RZT plants had fewer nodules, lower nodule weight, less N fixation, slower plant growth, fewer leaves, smaller leaf area, and less dry matter accumulation comared to plants at a higher RZT. Rhzobium leguminosarum bv. phaseoli cells induced with genistein and/or MeJA enhanced bean nodulation, nitrogen fixation and growth at both optimum and suboptimum RZTs. The results of this study indicate that MeJA improves bean nitrogen fixation and growth at both optimum and suboptimum RZTs, and can be used alone or in combination with genistein to partially overcome the low RZT induced inhibitory effects on nodulation and nitrogen fixation.     

Nodulation and N2 fixation of faba bean (Vicia faba L.) after soil amendment with crop residues

The effect of prior soil amendment with different N sources at 50 mg N (kg soil)^—1 on nodulation and N₂ fixation of faba bean (Vicia faba L. cv. Troy) using wheat (Triticum aestivum L. cv. Star) as reference crop was assessed in a pot experiment. Four treatments viz legume manure (LEGM) as clover shoots, cereal manure (CEREM) as barley straw, N fertilizer (FERT‐N) as Ca(NO₃)₂, and no‐manure control (NOMAN) were investigated consecutively at 45, 70, and 90 days after sowing (DAS). Faba bean nodulated profusely, with an increase on average from 629 nodules per pot at 45 DAS to nearly 2.3‐ and 3.3‐fold at 70 and 90 DAS, respectively. Low nodule numbers and nodule dry matter occurred under FERT‐N and CEREM, whereas high values were found for NOMAN and LEGM. Soil amendment affected percent N₂ fixation in relation to N source and plant age. Highest percent N₂ fixation (≥ 90 %) was found under the lowest N‐supplying amendments, no‐manure, and cereal manure, respectively. FERT‐N depressed N₂ fixation particularly at 45 DAS when N₂ fixation was reduced to as low as 23 %. The rise in N₂ fixation thereafter suggests that faba bean adjusted after depletion of mineral N in the soil. N₂ fixation was also decreased after cereal straw application, even though N concentration in faba bean plants was high. The results indicate that plant residues, both with high and low N concentration, applied to soil to raise its fertility may interfere with N₂ fixation of faba bean.     

Symbiotic efficiency of Sesbania rostrata and S. cannabina as affected by agronomic practices

A field experiment was conducted to study the N₂ fixation efficiency of Sesbania rostrata and S. cannabina as affected by agronomic practices in semi-arid subtropical climate, Sowing seeds resulted in smaller numbers of nodules, lower dry weight, lower total biomass, less N uptake, and less N₂ fixation for S. rostrata than S. cannabina, while cut-stem planting improved the symbiotic efficiency. Flooding the soil increased the relative humidity of the crop micro-environment by 4–11% and induced early appearance of stem nodules in S. rostrata. Only 67 kg N ha^-1 was fixed by S. rostrata compared to 160 kg N ha^-1 by S. cannabina when normal agronomic practices (sowing and non-flooding) were followed. In contrast, planting stem cuttings and flooding resulted in greater biological N₂ fixation, 307 and 209 kg N ha^-1 by S. rostrata and S. cannabina, respectively. Therefore, S. rostrata can be successfully exploited as a green manure when stem cuttings are planted under flooded conditions.     

Vegetative and reproductive dry weight inhibition in nitrogen‐ and phosphorus‐deficient Pima cotton 1

Whether the extent of dry weight inhibition by nitrogen (N) or phosphorus (P) deficiencies on different plant parts is the same and whether imposing moderate N and P deficiencies selectively suppress undesirable vegetative growth has not been studied in Pima cotton (Gossypium barbadense L.). The purpose of this study was to determine the extent to which dry matter accumulation in leaves, stems, and reproductive structures is inhibited by N and P deficiencies in Pima cotton. The study was conducted in 1991 and 1992 in a Uvalde silty clay loam soil (fine‐silty, mixed, hyperthermic Aridic Calciustolls). The treatments included applied rates of 0, 67, 135, 202, and 269 kg N ha^‐1 in a factorial combination with 0, 15, 29, and 44 kg P ha^‐1. Nitrogen deficiency (0 kg N ha^‐1) significantly (P≤0.05) reduced leaf (LDW) and stem (SDW) dry weights in both years and reproductive dry weight (RDW) in 1992. Nitrogen deficiency suppressed dry weight accumulation in leaves to a greater extent than in stems. Relative to 269 kg N ha^‐1, the 0 kg N ha^‐1 treatment resulted in a maximum LDW reduction of 62% at 144 DAP (days after planting) in 1991 and 36% at 121 DAP in 1992, compared with a corresponding SDW reduction of only 39% in 1991 and 25% in 1992. Dry weight accumulation in reproductive parts was the least affected by N deficiency. The decline in LDW associated with senescence and defoliation began earlier in treatments that received 0 or 67 kg N ha^‐1 than treatments that received ≥135 kg N ha^‐1. Phosphorus affected LDW and SDW in 1991, but its differential effect on LDW, SDW, and RDW was much smaller than that of N. Imposing a moderate level of N deficiency, not P deficiency, may be an effective Pima cotton management strategy to selectively suppress undesirable vegetative growth and enhance maturity.     

Effects of density of planting and time of nitrogen application on maize varieties in different ecological zones of West Africa

Abstract

Field experiments were conducted in 1992 on soils which have been classified as Alfisols ranging from Paleustalf to Oxic Paleustalf which represent three different ecological zones of West Africa. This research was conducted to determine the effect of density of planting on yield and yield components at 53,333, 66,666, and 79,999 plants‐ha^‐1 and time of nitrogen (N) fertilizer application [50% at planting and 50% at four weeks after planting (4WAP), entire N application at two weeks after planting (2WAP), and 50% at planting and 50% at anthesis]. The experiment was a factorial arrangement fitted to randomized complete block design and replicated three times. The maize (Zea mays L.) varieties used in this study gave increased yields at population density up to 53,333 plants‐ha^‐1 in Ikenne and Mokwa, while a response of 79,999 plants‐ha^‐1 was obtained at Kaduna. The results also showed that a split application of N at planting and 4 WAP appeared to be the best for Ikenne, while the entire application at 2WAP appeared to be the best in savanna ecologies. The results indicate increase yield with increasing latitude suggesting that the higher solar radiation in the savanna ecologies increase the photosynthetic capacity of the maize plants used in the study. Maize genotypes used in this study did not respond to density beyond 53,333 plants‐ha^‐1 at Ikenne and Mokwa, though a response was obtained up to 79,999 plants‐ha^‐1 at Kaduna. Thus, it can be concluded that density response is location dependent and that farmers should plant maize at highest optimum plant population density as determined by experimental results in each ecological zone of West Africa. The results also showed that a split application of N at planting and 4WAP appeared to be the best for Ikenne, while the entire N application at 2WAP appeared to be the best for the savanna ecologies.     

Relationships between nitrogen rate,plant nitrogen concentration,yield and residual soil nitrate‐nitrogen in silage corn

Abstract

Nitrogen (N) fertilizer is a key factor of yield increase but also an environmental pollution hazard. The sustainable agriculture system should have an acceptable level of productivity and profitability and an adequate environmental protection. The objectives of this study were to determine the relationships between N rate, DM yield, plant N concentration (NC) and residual soil nitrate‐nitrogen in order to improve the predicted N rate in corn (Zea mays L.) silage. The experiment was conducted over a period of three years in the province of Quebec on three soil series in a continuous corn crop sequence. Treatments consisted of six rates of N: O, 40, 80, 120, 160, and 200 kg N ha^‐1 as ammonium nitrate applied at planting: broadcast and side banded. Four optimum N rates were calculated using different models: (i) economic rate base on fertilizer and corn price using the quadratic model (E); (ii) economic rate based on fertilizer and corn price using the quadratic‐plus‐plateau model (QP); (iii) critical rate based on linear‐plus‐plateau model (P); (iv) lower than maximum rate (L) corresponding to 95% of maximum yield. The optimum plant NC at all growing stages and the N uptake at harvest were calculated depending on these N rates and yields.

The NC of whole plant at 8‐leaf stage (25–30 cm plant height) of ear leaf at tasselling and of whole plant at harvest stage, the N rate, the N uptake at harvest and the DM yield were all significantly intercorrelated and affected by soils and years, but not affected by N fertilizer application method. The DM yield was linearly and significantly related to NC of whole plant at 8‐leaf stage (rv = 0.932**). At this stage, the average NC corresponding to the optimum N rate and yield was of 3.71, 3.68, and 3.66% as calculated with E, L, and P model, respectively. Our data suggest that the NC of whole plant at 8‐leaf stage may be used to evaluate the N nutrition status of plant and the required optimum N fertilizer rate. The NC of ear leaf at tassel stage was also significantly correlated to corn yield (r = 0.994**). It may be used as an indicator to evaluate the near‐optimum N rate in the subsequent years.

The N uptake by whole above‐ground plant at harvest was quadratically related to corn yield. Data show that at high fertilizer N rate, the N uptake still increased without significantly increasing yield. The N uptake was of 176.5, 163.0, and 155.0 kg N ha^‐1 using the E, L and P rates of 146, 126, and 115 kg N applied ha^‐1, respectively. The optimum N rate and yield were affected by soil type and year, but not by the method of N fertilizer application. The yield increased rapidly up to a N rate of about 120 kg N ha^‐1 and then quite slightly to a maximum N rate of 192 kg N ha^‐1. The optimum N rate was of 115 and 126 kg N ha^‐1 using the P and L model respectively and as high as 146.8 kg N ha^‐1 using the E model. The L model, using a much smaller N rate, gave a reasonably high yield compared to E rate (12.2 and 12.5 Mg ha^‐1, respectively). The data show that a relatively much lower N rate than maximum did not proportionally diminish the yield. Thus, for a difference of 40.4% between maximum N rate and P rate a difference of only 7.4% in yield was observed. Using the L model the differences in rate and yield were of 34.4% and 4.7%, respectively. The QP model gave no significant difference compared to E model.

At harvest the residual soil NO₃‐N increased significantly with increasing N fertilizer rate in whole of the 100 cm soil profile, but mainly in the top 40 cm soil layer. The total NO₃‐N found in 0–100 cm profile at rate of 0, 120 and 200 kg applied N ha^‐1 at planting was as high as 33.7, 60.5, and 74.5 kg N ha^‐1 respectively in a light soil and 37.5, 97.5, and 145.5 kg N ha^‐1 in a heavy clay soil. The difference in NO₃‐N content in the 60–100 cm layer between different applied N rate suggests that at harvest, part of fertilizer N applied at planting was already leached below the 100 cm soil layer. Results, thus, show that reasonably high corn yields can be obtained using more adequate N fertilizer rates which avoid the overfertilization and are likely to reduce the air and ground water pollution.     

Fiber‐optic spectrophotometry of cowpea nodules treated with nitrate or ammonium

Abstract

Cowpea nodules (Vigna unguiculata [L.] Walp. cv. CB5) were pierced with two opposing optical fibers (280 μm diameter), and absorbance spectra of 0.1 mm of nodule tissue were recorded from 415 to 600 nm using a modified spectrophotometer with a nodule sampling stage.

The nodule spectra exhibited two absorbance bands, a major band in the near‐UV (415–450 nm) and a lesser one in the green‐yellow region (510–585 nm); the latter exhibited a prominent peak at 550 nm. Nodule spectra were consistent with the superposition of the spectra of ferroleghemoglobin (Lb²⁺), oxyleghemoglobin (Lb²⁺‐ O₂), and cytochrome c (550 nm). The detection of leghemoglobin in vivo was confirmed by demonstrating the reversibility of binding of CO to Lb, and by comparing the spectra of live nodules with those obtained from anaerobic leghemoglobin preparations.

The effects on the nodule spectra of two successive applications (36 and 39 days after planting) of 5 and 10 mM NO₃ ^‐ or NH₄ ⁺ to the nutrient solution bathing the nodulated roots were determined. The spectra of NO₃ ^‐‐ and NH₄ ⁺‐treated nodules were indistinguishable; in each case the height of both the near‐UV and green‐yellow absorbance bands decreased with treatment. Treatment with N caused a significant reduction in the area of the green‐yellow absorbance band.

The spectra of green leghemoglobin pigments were obtained from senescent nodules; these exhibited a reduction in the height of the near‐UV absorbance band and a flattening of the green‐yellow band similar to that of nodules treated with N, but the broadening of the near‐UV band was greater in green nodules.     

Is it possible to attain high-yielding common bean using molybdenum fertilizer instead of side-dressed nitrogen?

We evaluate the feasibility of using foliar-applied molybdenum, (Mo) instead of side-dressed nitrogen (N) in three experiments. In soils with native rhizobia, plants received 0, 30, 60, 90 or 120 kg N ha^?1 with +Mo (80 g ha^?1) or -Mo. N concentration in leaves (NCL) -Mo ranged from 35.1 to 42.5 g kg^?1 and NCL +Mo from 40.3 to 49.2 g kg^?1; yield -Mo ranged from 1560 to 3350 kg ha^?1and yield +Mo from 2829 to 3567 kg ha^?1. In two experiments, NCL or yield -Mo increased linearly or quadratically with increasing N rates, but NCL or yield +Mo did not. In one experiment, NCL increased linearly with increasing N rates and 16% with +Mo relative to –Mo, but yield was not affected significantly. Our results suggest that using Mo fertilizer instead of side-dressed N can allow common bean plants to meet crop demands for N to support yields as high as 3000 kg ha^?1.     

Effectiveness of native Rhizobium on nodulation and yield of faba bean (Vicia faba L.) in Eastern Ethiopia

This study was initiated to evaluate the effect of locally isolated Rhizobium on nodulation and yield of faba bean at Haramaya, Ethiopia for three consecutive years. Ten treatments comprising of eight effective isolates of rhizobia, uninoculated, and N-fertilized (20 kg N ha^?1) were laid out in a randomized complete block design with three replications. The result of the experiment indicated that all inoculation treatments increased nodule number and dry weight over the control check in all cropping seasons. The result, however, showed the non-significant effect of Rhizobium inoculation on shoot length, number of tiller per plant and 100 seed weight in all cropping season. Inoculating Haramaya University Faba Bean Rhizobium (HUFBR)-15 in 2011 and National Soil Faba Bean Rhizobium (NSFBR)-30 in 2012 and 2013 gave the highest grain yields (4330, 5267 and 4608 kg ha^?1), respectively. These records were 75%, 48%, and 5% over the uninoculated treatment of respective years. Over the season, NSCBR-30 inoculation resulted in the highest nodulation and grain yield production as compared to the other treatments. In general, isolates from central Ethiopia were better than those isolated from eastern Ethiopia and Tropical Agricultural Legume (TAL)-1035 in enhancing faba bean production at Haramaya site. Therefore, NSFBR-30 is recommended as a candidate isolate for faba bean biofertilizer production in eastern Ethiopia soils.     

Nitrogen fixation,biomass production,and nutrient uptake by annual Sesbania species in an alkaline soil

Summary In three field trials conducted during the summer season of 1986, 1987 and 1989 in an alkaline soil, 17 accessions of annual Sesbania spp. were evaluated for nodulation, N₂ fixation (acetylene reduction assay), dry weight of roots and shoots, woody biomass production, and nutrient uptake. At 50 days after sowing all the accessions were effectively nodulated (average 36.4 root nodules plant^-1) with a high nodule score (3.4). There was a lot of variation in nodule volume and mass and in acetylene reduction activity but not in N content (5.2%). N uptake in shoots, roots and nodules averaged 639, 31, and 13 mg plant^-1, respectively, and much of the fixed N remained in shoots. Accessions of S. cannabina complex performed better than others. S. rostrata had poor root nodulation but exhibited excellent stem nodulation (300 nodules plant^-1) even though not inoculated with Azorhizobium sp. Average concentrations of N, P, K, S, Ca, and Mg in the shoots were high, at 3.2, 0.28, 1.5, 0.28, 1.5, and 0.4% respectively, and Na was low (0.15%), reflecting the usefulness of Sesbania spp. as an integrated biofertilizer source. Green matter production was 26.0 Mg ha^-1 (5.9 Mg dry matter) and N uptake was 158 kg ha^-1, 54 days after sowing. Average woody biomass of six accessions at maturity, 200 days after sowing, was high (19.9 Mg ha^-1), showing its potential for shortterm firewood production. Total nutrient uptake for production of woody biomass (200 days of growth) was no more demanding than growing the plant to the green-manuring stage of 50–60 days' growth.     

“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.     

Physiological changes in soybean treated with ozone and molybdenum

Abstract

An open‐top field chamber experiment was conducted to evaluate the impact of Molybdenum (Mo) addition to soil on the physiological changes in soybean (Glycine max L. Merrill) exposed to ozone (O₃). Plants grown with Mo (0, 1.0, or 2.0 mg kg"¹ soil dry weight) were exposed to O₃ (O, 0.06, or 0.12 μmol mol^‐1) in open‐top field chambers for 12 h d^‐1 for 21 d with a N‐free fertilizer, during the sensitive growth stage (R2). The rate of photosynthesis (PN), specific root nodule nitrogenase activity (SNA), leaf nitrogen (N), chlorophyll (chl‐a, chl‐b) and biomass of soybean were measured. The increase in O₃ levels significantly reduced PN, SNA, leaf‐N, chl‐a, chl‐b, and biomass. Addition of Mo increased leaf‐N, shoot, root, and nodule dry weights but did not change PN, SNA, or chlorophyll. The addition of Mo (2 mg kg ^‐1) helped in significantly increasing PN and chlorophyll in the presence of 0.06 umol mol^‐1 O₃ but no change was observed in the presence of 0.12 μmol mol^‐1 O₃.     

Yield and yield components of two irrigated red bean cultivars and some soil properties as influenced by wheat residues and nitrogen management

Crop residues are beneficial substances affecting crop production and soil properties. A field experiment was carried out to evaluate the effects of wheat (Triticum aestivum L.) residue rates (0, 25, 50 and 75%) combined with N levels (0, 34.5, 69, 103.5 kg ha^?1) on yield and yield components of two red common bean (Phaseolus vulgaris L.) cultivars and to monitor chemical soil parameters. The experiment was conducted at Research Center, College of Agriculture, Shiraz University, Shiraz, Iran for two years (2008–2009). The experiment was conducted as a split–split plot arranged in a randomized complete blocks design with three replications. The highest seed yield was obtained when 25–50% of residues were incorporated. The highest seed yield, seed weight per plant, 100-seed weight and seed number per pod were obtained with 103.5 kg N ha^?1 with no significant difference to 69 kg N ha^?1. Residue incorporation significantly increased soil organic carbon (SOC) as well as available K and P content. It is possible to sow red common bean as a double cropping by soil incorporation of 25–50% wheat residues with application of 69 kg N ha^?1.