Genotypic Differences in Dry Bean Yield and Yield Components as Influenced by Nitrogen Fertilization and Rhizobia

Dry bean (Phaseolus vulgaris L.) is an important legume worldwide and nitrogen (N) is most yield limiting nutrients. A field experiment was conducted for two consecutive years to evaluate response of 15 dry bean genotypes to nitrogen and rhizobial inoculation. The N and rhizobia treatments were (i) control (0 kg N ha^?1), (ii) seed inoculation with rhizobia strains, (iii) seed inoculation with rhizobia strains + 50 kg N ha^?1, and (iv) 120 kg N ha^?1. Straw yield, grain yield, and yield components were significantly influenced by N and rhizobial treatments. Grain yield, straw yield, number of pods m^?2, and grain harvest index were significantly influenced by year, nitrogen + rhizobium, and genotype treatments. Year × Nitrogen + rhizobium × genotype interactions were also significant for these traits. Hence, these traits varied among genotypes with the variation in year and nitrogen + rhizobium treatments. Inoculation with rhizobium alone did not produce maximum yield and fertilizer N is required in combination with inoculation. Based on grain yield efficiency index, genotypes were classified as efficient, moderately efficient, and inefficient in nitrogen use efficiency (NUE). NUE defined as grain produced per unit N applied decreased with increasing N rate. Overall, NUE was 23.17 kg grain yield kg^?1 N applied at 50 kg N ha^?1 and 13.33 kg grain per kg N applied at 120 kg N ha^?1.     

Inoculation of rice plants with the endophytic diazotrophs Herbaspirillum seropedicae and Burkholderia spp.

 Four experiments were performed under gnotobiotic conditions to select strains of the endophytic diazotrophs Herbaspirillum seropedicae and Burkholderia spp. as inocula of rice plants. Eighty strains of H. seropedicae originally isolated from rice, sorghum and maize plants, were tested in test tube cultures with N-free agar as the substrate. Rice plants showed medium and high increases in their fresh weight in response to inoculation with nineteen strains. These strains were tested again, and six strains were then selected to evaluate their contribution to the N of the plant via biological N₂ fixation (BNF) using an agar growth medium containing 5 mg N l^–1of ¹⁵N-labelled (NH₄)₂SO₄. The contribution of the strains to plant N via BNF varied from 54% when rice plants were inoculated with strain ZAE94, to 31% when strain ZAE67 was used. These results were confirmed in the fourth gnotobiotic experiment, which also included strains of the new N-fixing bacteria belonging to the genus Burkholderia, isolated from rice, as well as a strain of Burkholderia vietnamiensis, isolated from rice rhizosphere. Burkholderia spp. strains showed similar effects to those observed for H. seropedicae strains, while B. vietnamiensis fixed only 19% of plant total N. The best four strains were tested in a pot experiment where pre-germinated, inoculated rice seedlings were grown in soil labelled with ¹⁵N. The results confirmed the gnotobiotic experiments, although the levels of N in the rice plants derived from BNF of the selected H. seropedicae and Burkholderia spp. strains were lower. Nevertheless, there was an increase in N content in grains of inoculated plants, and the results showed that the method used for strain selection is very useful and can be applied to other strains of N₂-fixing bacteria and plants. Received: 4 May 1999     

Grain yield response of Zea mays (hybrid AE 703) to Azotobacter chroococcum H23

Summary Field experiments were conducted during 1985 and 1986 to examine the effect of Azotobacter chroococcum on the grain yield of maize. Application of 40 kg N ha^–1 plus A. chroococcum caused a significant increase in maize yield. Azotobacter inoculation was more efficient at lower doses (40 kg N ha^–1) than at high doses (80 kg N ha^–1) of urea.     

Inoculant plant growth-promoting microorganisms enhance utilisation of urea-N and grain yield of paddy rice in southern Vietnam

Field experiments were conducted during successive rainy seasons in 2006 in the Chau Thanh district of southern Vietnam to evaluate the effects of an inoculant plant growth promoter product called “BioGro” and N fertiliser rates on yield and N and P nutrition of rice. The results indicated that inoculation with BioGro, containing a pseudomonad, two bacilli and a soil yeast, significantly increased grain and straw yields and total N uptake in both seasons, as well as grain quality in terms of percentage N. Nitrogen fertilisation increased grain and straw yields as well as total N and P uptakes significantly in both cropping seasons. The estimated grain yield response to added N was quadratic in nature with and without added BioGro. In the first crop, BioGro out-yielded the control up to 90 kg urea N ha^?1 whilst in the second season the beneficial effect of BioGro was observed up to 120 kg urea N ha^?1, indicating either an interaction of the inoculant with higher yielding seasonal conditions or a cumulative effect of BioGro application. In the first season, the estimated N rate for maximum grain yield was 103 kg N ha^?1 with BioGro while it was 143 kg N ha^?1 without BioGro. The maximum estimated grain yields were 3.21 and 3.18 t ha^?1 with and without BioGro, respectively. This information indicates that BioGro was able to save 40 kg N ha^?1 with an additional rice yield of 30 kg ha^?1 in the season. In the second rainy season, the estimated N rates for maximum grain yields were 94 and 97 kg N ha^?1 with and without BioGro, respectively. The estimated maximum grain yields were 3.49 and 3.25 t ha^?1 with and without BioGro, respectively. The two seasons’ combined results indicate that application of BioGro improved the efficiency of N use by rice significantly, saving 43 kg N ha^?1 with an additional rice yield of 270 kg ha^?1 in two consecutive seasons at the experimental site. The extra efficiency was shown by the fact that the same yield of rice was obtained with about 40 and 60 kg less fertiliser-N that the maximum yields with urea alone in the two successive harvests on the same plots.     

Maize genotype effects on the response to Azospirillum inoculation

Two field experiments were carried out in Northern Argentina, during the 1989–1990 and 1990–1991 growing seasons, on Argentinian and Brazilian maize genotypes. The inoculant consisted of a mixture of four Azospirillum brasilense strain isolated from surface-sterilized maize roots in Argentina and three A. lipoferum strains isolated from surface-sterilized maize or sorghum roots in Brazil. Establishment of the inoculated strains was confirmed by the antibiotic resistance of the strains in the highest dilution vials. In all treatments, numbers of Azospirillum spp. were increased and the inoculated strains were found in the highest dilutions. While grain yields of the different genotypes varied between 1700 and 7300 kg ha^-1, total N accumulation was much less variable. Significant inoculation effects on total N accumulation and on grain yields were consistently negative with one Argentinian genotype and positive with four Argentinian and two Brazilian genotypes. Significant inoculation effects on leaf nitrate reductase activity at the flowering stage, observed in the range-55% to +176%, indicated the presence of various interactions between the plant NO _inf3 ^sup- metabolism and Azospirillum spp. Three Brazilian and one Argentinian maize genotype showed significant decreases in leaf nitrate reductase due to inoculation while four Argentinian genotypes showed significant increases in leaf nitrate reductase activity. The results of the present study, were consistent over the two field experiments and strongly indicate that more detailed plant genotype-Azospirillum spp. strain interaction studies, taking the entire N metabolism in the plant into account, are needed to allow better inoculation results of cereal crops.     

Nitrogen use in maize-grain legume cropping systems in semi-arid Kenya

Locally suitable cultivars of maize, beans, and cowpeas were grown in field experiments for four seasons in semi-arid Kenya. For three seasons, the dry matter production and grain yield of maize and beans were not increased by N fertilizer additions up to 120 kg N ha^-1. Fertilizer recoveries measured by ¹⁵N isotope dilution techniques were low, less than 20%. Inoculated and uninoculated beans failed to fix N₂. By contrast the cowpea derived 50% of its N from fixation, equivalent to 197 kg N ha^-1. The N content of the grain generally exceeded 40 kg N ha^-1, and the N content of the seeds from the grain legumes were greater than those from the cereals. Large inputs of N fertilizer or N by fixation are required if maize-grain legume cropping system in semiarid Kenya are to be sustained in the long term.     

Quantification of nitrogen fixation by the peanut/Rhizobium symbiotic system in a virgin sandy soil

Nitrogen balance studies were conducted to quantify the nitrogen fixed by peanut/Rhizobium symbiotic system under field conditions in a sandy soil. Large scale inoculation with three NifTAL strains of cowpea rhizobia, 1000, 169, 1371 was done using two inoculation techniques: peat-based inoculant or injection of inoculant with irrigation water through an injection tank attached to the central pivot system. The results show nitrogen fixation amounting up to 186 kg N ha^?1 in peat-based inoculant and 171 kg N ha^?1 in liquid inoculant injected through the irrigation system. However, no significant differences in yield response were recorded between both inoculation techniques.     

Paddy System with a Hybrid Rice Enhances Cyanobacteria Nostoc and Increases N2 Fixation

Biological nitrogen(N) fixation(BNF) plays a significant role in maintaining soil fertility in paddy field ecosystems. Rice variety influences BNF, but how different rice varieties regulate BNF and associated diazotroph communities has not been quantified. Airtight,field-based ~(15)N_2-labelling growth chamber experiments were used to assess the BNF capacity of different rice varieties. In addition,both the 16 S rRNA and nifH genes were sequenced to assess the influence of different rice varieties on bacterial and diazotrophic communities in paddy soils. After subjecting a rice-soil system to 74 d of continuous airtight, field-based ~(15)N_2 labelling in pots in a growth chamber, the amounts of fixed N were 22.3 and 38.9 kg ha~(-1) in inbred japonica(W23) and hybrid indica(IIY) rice cultivars planted in the rice-soil systems, respectively, and only 1%–2.5% of the fixed N was allocated to the rice plants and weeds. A greater abundance of diazotrophs was found in the surface soil(0–1 cm) under IIY than under W23. Sequencing of the 16 S rRNA gene showed significantly greater abundances of the cyanobacterial genera Nostoc, Anabaena, and Cylindrospermum under IIY than under W23.Sequencing of the nifH gene also showed a significantly greater abundance of Nostoc under IIY than under W23. These results indicate that the hybrid rice cultivar(IIY) promoted BNF to a greater extent than the inbred rice cultivar(W23) and that the increase in BNF might have been due to the enhanced heterocystous cyanobacteria Nostoc.     

Timing and Method of 15Nitrogen-Labeled Fertilizer Application on Grain Protein and Nitrogen Use Efficiency of Spring Wheat

ABSTRACT

Grain protein content is one of the most important quality constraints for bread wheat (Triticum aestivum L.) production in eastern Canada. A field experiment was conducted for two years (1999 and 2000) on the Central Experimental Farm, Ottawa, Canada, to study whether split application of nitrogen (N) fertilizer improved grain protein content and nitrogen-use efficiency (NUE). Two cultivars (‘Celtic,’ as N-responsive and ‘Grandin’, as N-non-responsive) were grown using three different N doses and application methods: (1) 100 kg N ha^?1 as NH₄NO₃, soil-applied at seeding with ¹⁵N₂-labeled NH₄NO₃ to microplots, (2) 60 kg N ha^?1 soil-applied at seeding plus 40 kg N ha^?1 foliar-applied at the boot stage with ¹⁵N₂-labeled urea to microplots, and (3) 90 kg N ha^?1 as soil-applied at seeding plus 10 kg N ha^?1 foliar-applied at the boot stage with ¹⁵N₂-labeled urea to microplots. Plants were sampled at heading and maturity. While dry-matter production and grain yields were not affected by the treatments in either year, N application methods influenced tissue N concentration and NUE. In 1999, extended drought stress led to significant yield reduction; in 2000, foliar application of 10 kg N ha^?1 at the boot stage significantly increased grain N concentration when grain protein was under the limit for bread quality, suggesting that later-applied N can contribute to grain protein content. At maturity, the average NUE was 22.3% in 1999 and 34.5% in 2000, but was always greater when all N was applied at seeding (42.5%) than when N was foliar-applied at the boot stage (18.5% to 24.5%). We conclude that application of a small amount of fertilizer N at the boot stage can improve the bread-making quality of spring wheat by increasing grain protein concentration.     

Developing nitrogen management strategies under drip fertigation for wheat and maize production in the North China Plain based on a 3‐year field experiment

The intensive winter wheat (Triticum aestivum L.)–summer maize (Zea mays L.) cropping systems in the North China Plain (NCP) rely on the heavy use of mineral nitrogen (N) fertilizers. As the fertigated area of wheat and maize in the NCP has grown rapidly during recent years, developing N management strategies is required for sustainable wheat and maize production. Field experiments were conducted in Hebei Province during three consecutive growth seasons in 2012–2015 to assess the influence of different N fertigation rates on N uptake, yield, and nitrogen use efficiency [NUE: recovery efficiency (RE_N) and agronomic efficiency (AE_N)]. Five levels of N application, 0 (FN₀), 40 (FN_40%), 70 (FN_70%), 100 (FN_100%), and 130% (FN_130%) of the farmer practice rate (FP: 250 kg N ha^?1 and 205.5 kg N ha^?1 for wheat and maize, respectively), corresponding to 0, 182.2, 318.9, 455.5, and 592.2 kg N ha^?1 y^?1, respectively, were tested. Nitrogen in the form of urea was dissolved in irrigation water and split into six and four applications for wheat and maize, respectively. In addition, the treatment “drip irrigation + 100% N conventional broadcasting” (DN_100%) was also conducted. All treatments were arranged in a randomized complete block design with three replications. The results revealed the significant influence of both N fertigation rate and N application method on grain yield and NUE. Compared to DN_100%, FN_100% significantly increased the 3‐year averaged N recovery efficiency (RE_N) by 0.09 kg kg^?1 and 0.04 kg kg^?1, and the 3‐year averaged N agronomic efficiency (AE_N) by 2.43 kg kg^?1 and 1.62 kg kg^?1 for wheat and maize, respectively. Among N fertigation rates, there was no significant increase in grain yield in response to N applied at a greater rate than 70% of FP due to excess N accumulation in vegetative tissues. Compared to FN_70%, FN_100%, and FN_130%, FN_40% increased the RE_N by 0.17–0.57 kg kg^?1 and 0.03–0.34 kg kg^?1and the AE_N by 4.60–27.56 kg kg^?1 and 2.40–10.62 kg kg^?1 for wheat and maize, respectively. Based on a linear‐response relationship between the N fertigation rate and grain yield over three rotational periods it can be concluded that recommended N rates under drip fertigation with optimum split applications can be reduced to 46% (114.6 kg N ha^?1) and 58% (116.6 kg N ha^?1) of FP for wheat and maize, respectively, without negatively affecting grain yield, thereby increasing NUE.     

Response of traditional upland rice varieties to inoculation with selected diazotrophic bacteria isolated from rice cropped at the Northeast region of Brazil

The largest numbers of the Brazilian traditional upland rice varieties are found in the Maranhão state, Northeast region of Brazil. However, no information is available on the diazotrophic bacterial population associated as well as the plant growth promoting potential when these traditional genotypes are inoculated with native strains. Here, we evaluated the response of ten traditional rice varieties to inoculation with ten diazotrophic strains, previously isolated from rice soil of this region and screened for their ability to produce indole-3-acetic acid (IAA) in vitro. The procedure for selection of the best diazotrophic strain/rice variety interaction involved three steps: gnotobiotic conditions, soil pot and field experiments. The gnotobiotic experiment showed that the Azospirillum amazonense strain AR3122 increased the biomass of the traditional varieties Cana Roxa and Cana Forte (28 and 48%, respectively) while this effect was less evident for the other combination of strains/rice varieties. The soil pot experiment showed that the combination of Burkholderia vietnamiensis strain AR 1122 and traditional variety Arroz 70 was superior to the other strains/varieties and the treatment fertilized with 100 kg N ha⁻¹. The best performance of the Burkholderia vietnamiensis strain AR1122/variety Arroz 70 was confirmed in the field experiment. There was an increase of up 10 and 29% in the grain yield in comparison to both the N fertilization and Herbaspirillum seropedicae ZAE 94 strain treatments, respectively. In contrast, the response of the commercial variety Bonança to inoculation with strain AR1122 was much lower, suggesting that a biofertilizer inoculation program for traditional rice varieties should consider the genetic interaction between strain and rice variety. The diazotrophic B. vietmaniensis strain AR1122 was a good biofertilizer candidate for inoculation of traditional rice varieties and therefore should be used for further studies to confirm the strain-genotype effect envisaging a sustainable rice crop system mainly in the Northeast region of Brazil.     

Effects of inoculation with N2-fixing cyanobacteria on the nitrogenase activity in soil and rhizosphere of wetland rice (Oryza sativa L.)

Summary A greenhouse experiment was conducted with wetland rice (Oryza sativa cv. IR-50) in a clay-loam soil (Fluventic Eutrochrept) to study the effect of cyanobacterial inoculation a mixed culture of Aulosira fertilissima, Nostoc muscorum, Nostoc spp., and Anabaena spp., applied at the rate of 0.15 g (dry weight pot^-1 or 43 kg ha^-1) on acetylene reduction activity in soil and the root system (excised root), and the grain and straw yield. The effects of applying P (40 kg ha^-1), N (60 kg ha^-1), and P+N to the soil were also evaluated. Cyanbacterial inoculation significantly increased (more than 200% on average) photo-dependent acetylene reduction activity in soils, particularly where the indigenous activity was considerably low, i.e. under unfertilized and N-fertilized conditions. The effect of inoculation was prominent at the maximum tillering and grain formation stages of the crop. This inoculation benefit was, however, marginal in P-applied soils (P and P+N), where the indigenous activity was stimulated more than threefold. The inoculation led to a remarkable increase in root-associative acetylene reduction activity after the maximum tillering stage of the crop, particularly with applied N but for other treatments this inoculation effect was not significant. Cyanobacterial inoculation also increased the grain and straw yield of the crop when N was not applied. The grain and straw yield was significantly correlated with the acetylene reduction activity in flooded soils and in the root system during the tillering and maximum tillering stages of rice growth, respectively.     

Fate of Fertilizer-15N to a Maize Crop Grown in Northern Zambia

Abstract

A field study with maize (Zea mays L.) was conducted in the 1988/89 cropping season to investigate the fate of ¹⁵NO₃-N-labelled NH₄ ¹⁵NO₃ applied at 40, 80 and 120 kg N ha^?1 (unlabelled N applied at 0, 80, 160 and 240 N ha^?1) with and without lime. The investigations were conducted in northern Zambia at Misamfu Regional Research Centre, Kasama on a Misamfu red sandy loam soil. The experimental design was a split plot arrangement with four replications with main plots receiving 0 and 2 Mg ha^?1 dolomitic limestone, while subplots received fertilizer N at various rates. Significant (p < 0.001) grain and DM yield responses to applied N up to 160 kg ha^?1 were observed. At higher rates little or no crop responses were observed and fertilizer use efficiency declined. Partitioning of amounts of total N and ¹⁵N in plants was in the order of seed = tassel > leaf> cob = earleaf> stem. Fertilizer N rates showed a highly significant (p < 0.001) effect on plant uptake of labelled N. Lime and its interaction with N rates had no effect on all measured parameters. Leaching of NO₃-N fertilizer to lower soil depths was in proportion to the rate of N applied, with highly significant (p < 0.001) differences among soil depths. Although higher concentrations of fertilizer-¹⁵N were recovered in the 0–20 cm depth the recovered portion at lower soil depths was still significant. Total recovery of labelled N by plant and by soil after crop harvest averaged 75, 55 and 54% of originally applied fertilizer-¹⁵N at 40, 80 and 120 kg N ha^?1, respectively. Corresponding unaccounted for ¹⁵N was 25, 45 and 46%. The most probable loss mechanism could have been by leaching to depths greater than 60 cm, gaseous losses to the atmosphere and root assimilation.     

Biological nitrogen fixation in Azospirillum strain-maize genotype associations as evaluated by the 15N isotope dilution technique

Few studies of the inoculation of cereal crops with N₂-fixing bacteria have included more than one or two plant genotypes. In a recent study performed in Argentina using 12 different maize genotypes, it was found in 2 consecutive field experiments that several of them responded consistently, either negatively or positively, to inoculation with a mixture of strains of Azospirillum spp. The present study in post was performed to investigate the effect of inoculation of individual strains (and a mixture) of Azospirillum spp., and their nitrate reductase negative (NR-) mutants, on the growth of four of these maize genotypes. Two of these genotypes were grown in ¹⁵N-labelled soil with the aim of quantifying any contributions of biological N₂ fixation. Two genotypes (Morgan 318 and Dekalb 4D-70) produced similar increases in grain yield when they were inoculated with a mixture of Azospirillum spp. strains or fertilized with the equivalent of 100 kg N ha^-1. The other genotypes (Dekalb 2F-11 and CMS 22) showed little response to inoculation or N fertilization. The Morgan 318 and Dekalb 4D-70 genotypes showed a large increase in total N accumulation, suggesting that the response was due to increased N acquisition, but not due to bacterial nitrate reductase as the NR- mutants generally caused plant responses similar to those of the parent strains. Despite problems with the stabilization of the ¹⁵N enrichment in the soil, the ¹⁵N isotope dilution results indicated that there were very significant biological nitrogen fixation (BNF) contributions to the Dekalb 4D-70 and CMS 22 maize genotypes.Dedicated to Professor J.C.G. Ottow on the occasion of his 60th birthday     

Field-level comparison of nitrogen rates and application methods on maize yield,grain quality and nitrogen use efficiency in a humid environment

Appropriate nitrogen (N) management practices are of critical importance in improving N use efficiency (NUE), maize (Zea mays) yield and environmental quality. A six-year (2005–2010) on-farm trial was conducted in Ottawa, Canada to assess the effects of N rates and application methods on grain yield and NUE. In four out of the six-year study, grain yield increased by 60–77 kg ha^?1 by sidedress, compared to 49–66 kg ha^?1 for each kg N ha^?1 applied at preplant. Grain yield response to N between the two strategies was similar in the other growing seasons. Sidedress strategy required 15 kg N ha^?1 less of the maximum economic rate of N (MERN) than preplant application. Our results indicate that sidedress application of 90–120 kg N ha^?1 with a starter of 30 kg N ha^?1 resulted in greater yield, grain quality and NUE than preplant N application in this cool, humid and short growing-season region.     

Combined application of inoculant,phosphorus and organic manure improves grain yield of cowpea

ABSTRACT

Low concentrations of P and organic manure in savanna soils limit cowpea response to rhizobia. The study was conducted to determine the combined effect of P and organic manure on cowpea response to rhizobia in a factorial experiment arranged in randomized complete block design with three replications on smallholder farmers’ fields in northern Ghana in 2015. The factors were two levels of Bradyrhizobium inoculant, two levels of P fertilizer, three treatments of manure (fertisoil, cattle manure, and no manure). Addition of Bradyrhizobium inoculant to P and fertisoil significantly increased shoot biomass yield from 1677 kg ha^?1 in the plots without Bradyrhizobium inoculation to 1913 kg ha^?1. Likewise, the addition of Bradyrhizobium inoculant to P and cattle manure significantly increased shoot biomass from 1437 kg ha^?1 to 1813 kg ha^?1. Grain yield increases of 1427 and 1278 kg ha^?1 were obtained over the control when either fertisoil or cattle manure and P, respectively, were added to Bradyrhizobium inoculant. The value cost ratio for adding Bradyrhizobium inoculant to phosphorus and fertisoil was two indicating that it could be attractive to risk-averse smallholder farmers. The study demonstrated the potential of the combined application of organic matter and P to improve cowpea response to Bradyrhizobium inoculation.     

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.     

Nitrogen fixation in six forage legumes in Mediterranean central Chile

Abstract

The contribution of biological nitrogen fixation (BNF) to the N nutrition of six annual forage legumes, subterranean clover (Trifolium subterraneum), burr medic (Medicago polymorpha), balansa clover (Trifolium michelianum), Persian clover (Trifolium resupinatum), yellow serradela (Ornithopus compressus), and pink serradela (Ornithopus sativus) was evaluated by the ¹⁵N natural abundance technique, using four grass species (Briza máxima, Bromus mollis, Hordeum berteroanum, Avena barbata) and two composite species (Leontodon leysseri and Hedipnois cretica) as reference plants. An additional objective was to determine whether alternative legume species to those in common use (T. subterraneum and M. polymorpha) in the area, could improve BNF. The field studies were conducted in two edaphic conditions, granitic (Entisol) and clay (Vertisol) soil, located in Cauquenes, VII Region, in the sub-humid Mediterranean zone of Chile. In the granitic soil the percentages of N derived from fixation were high in all species (74 to 94%); yellow serradela cv. Tauro presented the greatest N content in dry matter and N fixation, equivalent to 91 kg N ha^?1. In contrast, pink serradela cv. Cádiz and subterranean clover cv. Gosse presented the lowest N fixation. In the clay soil, under periodically waterlogged conditions, balansa clover cv. Paradana and persian clover cv. Prolific had high percentage values of BNF (>95%) and fixed more N (100.2 and 82.5 kg N ha^?1, respectively) than burr medic and subterranean clover cv. Gosse. The present study allowed the identification of new germplasm of high capacity of N fixation which is an additional criterion for selecting species for infertile and waterlogged soil conditions in the Mediterranean area of Chile.     

Reintroduction of a native Glomus to a tropical Ultisol promoted grain yield in maize after fallow and restored the density of arbuscular mycorrhizal fungal spores

Maize (Zea mays L.) is an important crop in central Thailand where fallow is widely practiced and farmers are interested in crop rotation and beneficial soil biota. A pot experiment using a Typic Paleustult (topsoil + subsoil) from the National Corn and Sorghum Research Centre, Nakhonratchasima Province, Thailand was undertaken over three successive crops to evaluate effects of agronomic practices on populations of arbuscular mycorrhizal (AM) fungi and to determine whether reintroduction of a local Glomus was beneficial to maintain maize yield. The three crops and their treatments were: (1) preceding crop: maize grown in all pots; (2) subexperiment 1: agronomic practices [maize, fallow ± soil disturbance, fallow with solarization, non–AM host (cabbage)]; and (3) subexperiment 2: maize ± Glomus sp. 3 at three rates of P fertilization (0, 33, 92 kg P ha^–1). The AM‐fungal community was established under the preceding crop. In subexperiment 1, the three fallow treatments decreased (30%–40%) the total AM spore number in the topsoil whereas there was no change under maize or cabbage. Glomus, the dominant genus, showed sensitivity to fallow. In subexperiment 2, inoculation with Glomus sp. 3 enhanced total AM spore number and root colonization when applied following the three fallow treatments. Furthermore, inoculation promoted grain yield; at nil P following fallow ± soil disturbance, at 33 kg P ha^–1 following fallow without soil disturbance, and following solarization. Two treatments, maize following maize and maize following cabbage, did not respond to inoculation with Glomus sp. 3. Overall, the results suggest that reintroduction of Glomus sp. 3, a local AM fungus in this soil, may overcome negative effects of fallow and promote effectiveness of P fertilizer. Further work is needed to evaluate the benefits of other indigenous AM species that persist under modern fertilization practices.     

Performance of chickpea (Cicer arietinum L.) to bio-fertilizer and nitrogen application in arid condition

Abstract

Field experiments were conducted during 2013–2014 at Tashkent, Uzbekistan to evaluate the performance of chickpea variety “Jakhongir” with the variable proportion of nitrogen (N) and bio-fertilizer inoculation in the moderate saline (5.6?±?0.6?dSm^?1) soil condition. The studied treatments were No control (non-fertilized), N1 mineral-N (50?kg?N?ha^?1), N2, mineral-N (75?kg?N?ha^?1), N3, mineral-N (100?kg?N?ha^?1) equivalent 0%, 50%, 75%, and 100% from recommended rate for chickpea, Rhizobium inoculation (Bio)?+?No control, Rhizobium inoculation (Bio)?+?N1, Rhizobium inoculation (Bio)?+?N2, and Rhizobium inoculation (Bio)?+?N3. Seed inoculation with Rhizobium was significantly superior over no inoculation treatments at all rate of N fertilization. The middle rate of N fertilization 75?kg?N?ha^?1 combined with biofertilizer inoculation had of superior effect on chickpea, producing 73.2% more yield (1.68?Mg ha^?1), oil, protein, and sugar content performed 16.4%; 15.0%, and 17.9% higher value, respectively, in comparison to control.