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1.
Summary A field trial was set up to examine the effect of green manuring, blue-green algae, and neem-cake-coated urea on a rice crop. Summer green manuring using Sesbania aculeata increased the crop yield. Inoculation of blue-green algae increased the rice grain yield when 60 kg N ha-1 was applied as prilled urea, but the increase in grain yield was greater when 60 kg N ha-1 was applied as neem-cake-coated urea. The results of the present study show that applications of green manure, neem-cake-coated urea, and blue-green algae are complementary and that the three treatments can be used together in the rice ecosystem. The green manure and the fertilizer treatments had no effect on the algal flora of the soil.  相似文献   

2.
Summary Field experiments were conducted to assess the effects of the application of P on growth and N yield of inoculated and indigenous blue-green algae (BGA). Addition of 17.4 kg P ha–1 in split applications led to the highest BGA biomass and N yield, 162 kg dry weight ha–1 and 6 kg N ha–1 per 15 days, respectively. When inoculum of Aulosira spp., Aphanothece spp., Gloeotrichia spp. were compared separately, Gloeotrichia spp. grew faster but Aulosira spp. fixed more N. The growth rate and N yield of Aulosira spp. decreased with high P applications, although growth continued until the application of 34.8 kg P ha–1. The effects of P on inoculum production by local species compared with those collected from other states showed the superiority of the local culture. Applications of P also enhanced the growth and N yield of indigenous BGA, with Wollea spp. showing the best results.  相似文献   

3.
Summary Virgin alkali (sodic) soils have a high pH and high exchangeable Na and are often barren. Blue-green algae, however, tolerate excess Na and grow extensively on the soil surface in wet seasons. Experiments using a highly degraded alkali soil (silt loam, pH 10.3, electrical conductivity 3.5 dS m-1, 90% exchangeable Na) were conducted in soil columns, with or without gypsum, in order to study the influence of waterlogging on the growth of indigenous and inoculated blue-green algae and hence, soil reclamation. The growth of indigenous blue-green algae was initially slow in alkali soil, due to the high pH and exchangeable Na, and depressed in gypsum-amended soil, due to excess Ca. Inoculation hastened the establishment of blue-green algae in both the unamended alkali soil and the gypsum-amended soil, overcoming the adverse influence of excess Na in the former and excess Ca in the latter. Gypsum was effective in amelioration (pH 9.05, electrical conductivity 1.2 dS m-1, 41% exchangeable Na after 11 weeks) but blue-green algae were ineffective even after 17 weeks. In combination with gypsum, blue-green algae had no additional effect, and the C and N increases due to the growth of indigenous or inoculated blue-green algae were insignificant.Alkali soil reclamation by biological methods requires mobilization of Ca from native soil calcite and the exchange of Ca for Na in the exchange complex. The ineffectiveness of blue-green algae was ascribed to their inability to mobilize Ca. It is argued that current theories favouring blue-green algae as a biological amendment to bring about alkali soil reclamation are untenable and are not comparable with an effective chemical amendment such as gypsum.  相似文献   

4.
Nitrogen fixing potential in terms of acetylene reducing activity (ARA) and biomass accumulation (in terms of chlorophyll) were investigated using surface and below-surface soil cores, collected from rice fields 45 and 90 days after transplanting (DAT). Treatments included different levels of urea (30, 60, 90 and 120 kg N ha–1) in combination with inoculation using blue green algae (BGA) and Azolla biofertilizers. Application of biofertilizers brought about a significant enhancement in chlorophyll accumulation and nitrogenase activity, when measured 45 DAT. Positive effects in below-surface soil cores, on both these parameters as a result of application of biofertilizers further emphasized their contribution to the N economy of rice fields. Plots treated with 30 and 60 kg N ha–1 along with biofertilizers exhibited the highest percentage increase in terms of algal biomass and ARA, both in surface and below-surface soil cores at 45 DAT. A definite need to examine critically the nature and metabolic activities of below-surface microflora is highlighted through our investigation.  相似文献   

5.
Summary The influence of surface growth of inoculated cyanobacteria (blue-green algae) on subsurface properties of a brown earth, silt loam soil was studied in reconstituted flooded soil columns. One blue-green algae species, Nostoc muscorum, become dominant within the first 7 days of inoculation. In light control columns (not inoculated) a bryophyte, Barbula recurvirostra, was dominant although significant growth of indigenous blue-green algae occurred. The blue-green algae counts were in the range of 1×106 g-1 dry soil in the surface layer (0–0.7 cm) in both columns. Any effect of surface phototrophic growth on soil properties was restricted to the surface layer. In inoculated columns there was a twofold increase in microbial biomass and an eightfold increase in bacterial numbers by week 13. However, bacterial numbers declined so that there was only a 2.8-fold increase by week 21. Dehydrogenase (x2.1), urease (x2.8) and phosphatase (x3.1) activities and polysaccharides (+69%) increased by week 21 as a result of the blue-green algae inoculation along with a significant improvement in soil aggregation. However, similar increases occurred in the light control columns, indicating that given appropriate conditions of light and moisture indigenous species may be ultimately as effective as introduced species in bringing about biochemical and microbiological changes to soil.  相似文献   

6.
In 1991, field experiments on loess (with winter wheat) and sandy soils (with summer barley) were conducted to study N dynamics in the microbial biomass and non-exchangeable NH inf4 sup+ . The measurements showed a mass change in microbial N, with a maximum increase of 100 kg N ha-1 30 cm-1 from March to July in the loess soil, and a change for only 1 month (May) in the sandy soil. Plots treated with conventional levels of N fertilizer (213 kg N ha-1 on a loess soil to winter wheat and 130 kg ha-1 on the sandy soil to summer barley), reduced levels of N (83% and 62% of the conventional N application), or no N showed no consistent fertilizer N effect on microbial biomass N. From March to July, non-exchangeable NH inf4 sup+ in loess soils under winter wheat decreased by 110 kg N ha-1 30 cm-1 in conventionally fertilized plots and by 200 kg N ha-1 30 cm-1 in a plot with no N fertilizer. After harvest, the pool of non-exchangeable NH inf4 sup+ increased due to increasing mineral N concentrations in the soil.  相似文献   

7.
Summary Azolla spp. and Sesbania spp. can be used as green manure crops for wetland rice. A long-term experiment was started in 1985 to determine the effects of organic and urea fertilizers on wetland rice yields and soil fertility. Results of 10 rice croppings are reported. Azolla sp. was grown for 1 month and then incorporated before transplanting the rice and 3–4 weeks after transplanting the rice. Sesbania rostrata was grown for 7–9 weeks and incorporated only before transplanting the rice. Sesbania sp. grew more poorly before dry season rice than before wet season rice. Aeschynomene afraspera, which was used in one dry season rice trial, produced a larger biomass than the Sesbania sp. The quantity of N produced by the Azolla sp. ranged from 70 to 110 kg N ha-1. The Sesbania sp. produced 55–90 kg N ha-1 in 46–62 days. Rice grain yield increases in response to the green manure were 1.8–3.9 t ha-1, similar to or higher than that obtained in response to the application of 60 kg N ha-1 as urea. Grain production per unit weight of absorbed N was lower in the green manure treatments than in the urea treatment. Without N fertilizer, N uptake by rice decreased as the number of rice crops increased. For similar N recoveries, Sesbania sp. required a lower N concentration than the Azolla sp. did. Continuous application of the green manure increased the organic N content in soil on a dry weight basis, but not on a area basis, because the application of green manure decreased soil bulk density. Residual effects in the grain yield and N uptake of rice after nine rice crops were found with a continuous application of green manure but not urea.  相似文献   

8.
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.  相似文献   

9.
Pot experiments were conducted with two soils, from Rottenhaus and Seibersdorf in Austria, to ascertain whether the rate of fertilizer N application and the test crop would influence the amount of N available in the soil as assessed by the A-value method. 15N-labelled fertilizer was applied at rates of 10, 25, 40, 60, and 100 mg N kg-1 soil, corresponding approximately to 20, 50, 80, 120 and 200 kg N ha-1 respectively, and two crop species, barley (Hordeum vulgareL.) and non-nodulating soybean (Glycine max L.) were used to determine the soil A N value under the various fertilizer regimes. The results showed that the Rottenhaus soil had a higher A N value than the Seibersdorf soil, suggesting that the former was more fertile than the latter. The A N values of both soils were significantly affected by the level of N application. When grown in the same soil, the two test crops showed significantly different fertilizer use efficiency and per cent N derived from fertilizer when the rate of N application exceeded 20 kg ha-1. Thus, the A N value as determined by the two test crops differed significantly for the same soil when the rate of N application was greater than 20 kg/ha. The difference was greater when the soil fertility level was high. The dependence of the A N value on the level of N application and the species of crop seriously compromises the suitability of this method for determining plant-associated N2 fixation. Hence, considerable caution is required when using this method to estimate plant-associated N2 fixation.  相似文献   

10.
Freshly-harvested blue-green algae (20 t ha?1) or Azolla (20 t ha?1) were incorporated into a waterlogged rice soil and changes of redox-potential and the availability of nitrogen and phosphorus were measured periodically. The soil progressively became reduced where blue-green algae or Azolla had been incorporated. The rate of N release from Azolla was more rapid than from blue-green algae and the amounts released after 7–35 days of flooding were between 41 and 76% and 12 and 35% respectively. Increased P availability was also recorded in soil following the incorporation of blue-green algae or Azolla and reached highest values after 21 days incubation.  相似文献   

11.
Summary Two annual species of Sesbania, S. aculeata and Sesbania sp. PL Se-17, were field evaluated as green manure for wetland rice in an alkaline soil. The two species were raised as a catch crop during summer in a wheat-rice rotation, and added as 24.7 and 20.8 t ha–1 of green matter, 116 and 98 kg N ha–1, respectively, after 45 days of growth. For the optimum green manuring effect on rice grain yield and N uptake, S. aculeata required 5 days of decomposition (after turning in and before rice transplantation), whereas no decomposition period was necessary for Sesbania sp. PL Se-17. The effect on grain yield and N uptake of rice was equivalent to an application of 122 and 78 kg ha–1 of chemical N, for the two species, respectively. There was no residual effect of the green manuring on the soil N status after rice harvest.  相似文献   

12.
Some of the measures suggested for amelioration of drought effects include application of N fertilizer and plant growth regulators (PGRs). Since N2-fixing bacteria produce plant growth substances (PGRs), the effect of foliar application of an active strain of Klebsiella sp. (KUPOS) on IR-50 rice was examined using three foliar sprays applied at 10-day intervals. Irrigation once every 3 days was essential for plant growth. Application of KUPOS and 40 kg N ha-1 improved grain yield of acutely water stressed plants from 330 kg ha-1 to more than 1300 kg ha-1 along with an improvement in several growth variables and yield determinants. Indole acetic acid, kinetin and GA3, in a mixture of 10-4 M of each, were less effective than KUPOS in alleviating stress effects. The adverse effects of water stress on respiration and photosynthesis as indicated by CO2 exchange were also alleviated by these treatments. While uptake of K, Mg, Ca, Fe and Mo was increased, Na content decreased, accompanied by an increase in proline content. The order of effectiveness of the treatments was 40 kg N ha-1 >KUPOS>PGRs.  相似文献   

13.
The Old Rotation cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha-1 year-1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 as NH4NO3; and III, 3-year cotton-corn- alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134 g N as NH4NO3 ha-1 year-1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha-1 year-1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r 2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r 2=0.87 and 0.98, respectively). After 99 years of management the Old Rotation cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.  相似文献   

14.
Sustainable cropping systems rely on a minimum of external inputs. In these systems N is largely acquired in animal manures and leguminous green manures. Little is known of how these organic forms of N fertilizer influence the presence and activity of free-living N2-fixing bacteria. High concentrations of inorganic N in soil inhibit N2-fixation in cyanobacteria and Azotobacter spp. It is likely that manure and fertilizer applications would result in concentrations of inorganic N capable of inhibiting N2 fixation and, ultimately, the presence of these organisms. We investigated the effect of synthetic and organic N fertilizer sources on the populations and N2-fixation potential of free-living N2-fixing bacteria in the Farming Systems Trial at the Rodale Research Institute. Field plots received the following N treatments prior to corn (Zea mays L.) production: (1) Legume rotations and green manures supplying about 165 kg N ha-1; (2) beef cattle manure applied at a rate of 220 kg N ha-1 (plus 60 kg N ha-1 from 1994 hay plow-down); or (3) fertilizer N (urea and NH4NO3) applied at a rate of 145 kg N ha-1. Soil samples were collected at two depths from corn plots four times during the growing season, and analyzed for soil moisture, soil pH, numbers of N2-fixing cyanobacteria and Azotobacter spp., extractable NH inf4 sup+ and NO inf3 sup- , and potentially mineralizable N. Soil samples collected in mid-July were analyzed for nitrogenase activity (by C2H2 reduction) and total C and N. Populations of Azotobacter spp. and cyanobacteria were influenced only slightly by treatment; however, cyanobacteria species composition was notably influenced by treatment. Nitrogenase activity in surface soils was greatest in legume-N plots and in subsurface plots levels were greatest in fertilizer-N plots. Populations and activity of free-living N-fixing bacteria appeared to be somewhat reduced in all plots as a result of low soil pH levels and high concentrations of inorganic N across all treatments. Annual applications of N to all plots resulted in high levels of potentially mineralizable N that in turn may have reduced non-symbiotic N2-fixation in all plots.  相似文献   

15.
Summary Chickpea cultivars (Cicer arietinum L.) and their symbiosis with specific strains of Rhizobium spp. were examined under salt stress. The growth of rhizobia declined with NaCl concentrations increasing from 0.01 to 2% (w : v). Two Rhizobium spp. strains (F-75 and KG 31) tolerated 1.5% NaCl. Of the 10 chickpea cultivars examined, only three (Pusa 312, Pusa 212, and Pusa 240) germinated at 1.5% NaCl. The chickpea — Rhizobium spp. symbiosis was examined in the field, with soil varying in salinity from electrical conductivity (EC) 4.5 to EC 5.2 dSm-1, to identify combinations giving satisfactory yields. Significant interactions between strains and cultivars caused differential yields of nodules, dry matter, and grain. Four chickpea — Rhizobium spp. combinations, Pusa 240 and F-75 (660 kg ha-1), Pusa 240 and IC 76 (440 kg ha-1), Pusa 240 and KG 31 (390 kg ha-1), and Pusa 312 and KG 31 (380 kg ha-1), produced significantly higher grain yields in saline soil.  相似文献   

16.
Summary A field study carried out in a sandy, relatively acid Senegalese soil with a low soluble P content (7 ppm) and low vesicular-arbuscular mycorrhizal (VAM) populations showed that soybean responded toGlomus mosseae inoculation when the soluble P level in the soil had been raised by the addition of 22 kg P ha–1. In P-fertilized plots, N2 fixation of soybean, assessed by the A value method, was 109 kg N2 fixed hat when plants were inoculated withRhizobium alone and it reached 139 kg N2 fixed ha–1 when plants were dually inoculated withRhizobium andGlomus mosseae using an alginate bead inoculum. In addition to this N2 fixation increase (+28%),Glomus mosseae inoculation significantly improved grain yield (+13%) and total N content of grains (+16%). This success was attributed mainly to the low infection potential of the native VAM populations in the experimental site. In treatments without solubleP or with rock phosphate, no effect of VAM inoculation was observed.  相似文献   

17.
华北地区采用无机氮测试和植株速测进行夏玉米氮肥推荐   总被引：2，自引：0，他引：2  
A field experiment with a split-plot design was carried out at Dongbeiwang Farm in Beijing Municipality to establish reliable N fertilizer recommendation indices for summer maize (Zea mays L.) in northern China using the soil Nmin(mineral N) test as well as the plant nitrate and SPAD (portable chlorophyll meter readings) tests. The results showed that Nrnin sollwert (NS) 60 kg N ha^-1 at the third leaf stage and N rate of 40 to 120 kg N ha^-1 at the tenth leaf stage could meet the N requirement of summer maize with a target yield of 5.5-6 t ha^-1. Sap nitrate concentrations and SPAD chlorophyll meter readings in the latest expanded maize leaves at the tenth leaf stage were positively correlated with NS levels, indicating that plant nitrate and SPAD tests reflected the N nutritional status of maize well. Considering that winter wheat subsequently utilized N after the summer maize harvest, the 0-90 cm soil Nmin (74 kg N ha^-1) and apparent N loss (12 kg N ha^-1) in the NS60＋40 treatment were controlled at environmentally acceptable levels. Therefore NS60＋40, giving a total N supply of 100 kg N ha^-1, was considered the optimal N fertilizer input for summer maize under these experimental conditions.  相似文献   

18.
Summary Nitrogen fixation in seven groundnut genotypes was measured by 15N-isotope dilution using a non-nodulating cultivar of groundnut as the nonfixing reference plant. Nitrogen fixation varied between 100 kg N ha–1 in genotype J-11 and 153 kg N ha–1 in Robut 33-1. The amount of plant-available soil N was small, so that 86%–92% of plant nitrogen was derived from N2-fixation. Thus differences in N2-fixation between genotypes closely reflected differences in their total N accumulation.ICRISAT Journal Article no. 600  相似文献   

19.
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.  相似文献   

20.
Afforestation of grasslands can increase C sequestration and provide additional economic and environmental benefits. Pine plantations, however, have often been found to deplete soil organic C and trigger detrimental effects on soils. We examined soil characteristics under a 45-year-old Pinus radiata stand and under adjacent grassland on maritime dunes in temperate Argentina. Soil under the pine plantation had greater soil organic C (+93%), total N (+55%) and available P (+100%) concentrations than under grassland. Carbon was stored under the pinestand at an estimated mean accretion rate of 0.64 Mg ha?1 y?1. At 0- to 25-cm depth, soil C amounted to 61 Mg ha?1 under pine and 27 Mg ha?1 under grassland. Soil C accumulated more on dune slopes (35 Mg ha?1 y?1) than on ridges(29 Mg ha?1 y?1) and bottoms (12 Mg ha?1 y?1). Compared with the grassland, soil acidity, cation-exchange capacity, base losses (K > Ca = Mg) and C/N ratio increased under pine. Spatial heterogeneity in soil characteristics was greater under pine than under grassland. Such variability was non-systematic and did not support the ‘single-tree influence circle’ concept. Afforestation increased C in soil, forest floor and tree biomass in dunes with ustic climate regime.  相似文献   

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