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1.
《Field Crops Research》2006,98(1):12-19
It is reported that stimulating effect of elevated atmospheric [CO2] on photosynthesis of rice (Oryza sativa L.) is likely to be reduced during the plant growth period. However, there is little information on seasonal changes in dry matter (DM) production and distribution of rice under elevated atmospheric [CO2]. A free-air CO2 enrichment (FACE) experiment was conducted at Wuxi, Jiangsu, China, in 2001–2003, using Wuxiangging 14, a japonica cultivar. The rice was grown at ambient or elevated (ca. 200 μmol mol−1 above ambient) [CO2] and supplied with 25 g N m2, which is the normal N application rate for local farmers. DM accumulation of rice in FACE plots was significantly increased by 40, 30, 22, 26 and 16% on average at tillering, panicle initiation (PI), heading, mid-ripening and grain maturity, respectively. Rice DM production under FACE was significantly enhanced by 41, 27, 15 and 38% on average during the growth periods from transplanting to tillering (Period 1), tillering to PI (Period 2), PI to heading (Period 3) and heading to mid-ripening (Period 4), respectively, but significantly decreased by 25% in the period from mid-ripening to grain maturity (Period 5). In general, seasonal changes in crop response to FACE in both green leaf area index (GLAI) and net assimilation rate (NAR) followed a similar pattern to that of the DM production. Under FACE the leaves decreased significantly in proportion to the total above-ground DM over the season, the stems showed an opposite trend, while the spikes depended on crop development stage: showing no change at heading, significant increase (+4%) at mid-ripening and significant decrease (−3%) at grain maturity. Grain yield was stimulated by an average of 13% by FACE, due to increased total DM production rather than any changes in partitioning to the grain. We conclude that the gradual acclimation of rice growth to elevated [CO2] do not occur inevitably, and it could also be altered by environmental conditions (e.g., cultivation technique).  相似文献   

2.
《Field Crops Research》2006,96(1):98-105
This study determined whether the field level concentration of root zone CO2 affects transpiration rate and root water transport in soybean (Glycine max L. Merr.). In an upland field converted from a paddy field, topsoil CO2 during the cropping season rose to 8 kPa of partial pressure after rainfall, whereas O2 dropped only to a minimum of 7 kPa. An elevated root zone CO2 pressure of 6 kPa significantly reduced transpiration rate. Although the transpiration rate of soybean plants exposed to hypoxia of 1.5 kPa O2 alone was reduced by 52% of the aerated plant, the rate was more decreased by 33 by adding CO2 gas to low root zone O2. Similarly, the elevated root zone CO2 significantly reduced hydraulic conductance of roots. The low transpiration rate with a high leaf water potential and low leaf greenness in the elevated root zone CO2 indicated that stomatal closure in high root zone CO2 may also occur irrespective of leaf water status and be involved in depressed nitrogen supply to a shoot. The results indicate that root zone CO2 at the field level is a growth inhibitor of waterlogged soybean through decreasing water uptake and/or stomatal aperture.  相似文献   

3.
《Field Crops Research》1999,62(1):53-62
Maize was grown in the high-radiation arid summer environment of Davis, California, and its leaf photosynthetic rate was measured over diurnal courses on cloudless days with the leaf held perpendicular to the sunlight. On days of high atmospheric vapor pressure deficit (VPD), leaf photosynthesis reached a maximum in the late morning and then decreased gradually as the day progressed, though the soil was well irrigated. When CO2 concentration in the measurement chamber was raised to about 1000 μmol mol−1, photosynthesis was enhanced, but more in the afternoon than in the morning. As a result, rates measured at high CO2 in the morning and afternoon were essentially the same. There was also no difference in the curves of photosynthetic rate (A) versus intercellular CO2 concentration (Ci) for the morning and afternoon. Hence, photosynthetic capacity was similar for the two periods and there was no evidence of photoinhibition by the high photosynthetic photon flux density at noon. Further, Ci and photosynthetic rates A measured over a range of photon flux density were lower in the afternoon than in the morning. These results indicate that A at noon and early afternoon was more limited than in the morning by epidermal conductance (mostly stomatal). On a day of low VPD, however, midday depression in A and epidermal conductance were not evident for the well-irrigated plants. Without irrigation and with leaves at a lower midday water potential, midday reduction in conductance and A was much more marked, beginning late in the morning. Epidermal conductance of maize grown in the field in Davis is are not sensitive to VPD. Therefore, the midday reduction in conductance and A was more likely the result of low leaf water potential caused by high transpiration rates.  相似文献   

4.
Applications of ultrahigh CO2 treatments accelerated cuphea (Cuphea viscosissima × C. lanceolata ‘PSR23’) growth and development and aided in seedling establishment. The growth (fresh weight) and morphogenesis (number of leaves and roots and seedling length) were determined in cuphea seedlings exposed to 350, 1500, 3000, 10,000, or 30,000 μmol mol−1 CO2 for 30 days under greenhouse conditions. Greater CO2 levels, especially the ultrahigh levels (i.e. ≥3000 μmol mol−1 CO2) resulted in significantly higher (P ≤ 0.05) fresh weights, leaf numbers, root numbers, and seedling lengths compared to seedlings grown under ambient air (350 μmol mol−1 CO2). For example, cuphea ‘PSR23’ Morris heavy seedlings showed the greatest seedling fresh weight, leaf number, root number, and seedling length when supplemented with 10,000 μmol mol−1 CO2 increasing 607%, 184%, 784%, and 175%, respectively, when compared to seedlings grown without CO2 enrichment.  相似文献   

5.
《Field Crops Research》2002,76(1):55-69
The simulation of seed reserve mobilization and seedling growth of rice in the model DSRICE1 was analyzed using published data. Early plant DM patterns are characterized by a decline in total (kernel+seedling) DM during heterotrophy, and then an increase into exponential growth after CO2 assimilation (autotrophy) begins. Data for a tropical japonica variety were used for qualitative comparisons of observed and predicted kernel and total DM. The published version of DSRICE1 was sequentially modified to (1) subtract respiration costs from mobilized reserves, (2) use a constant mobilization rate, (3) use the same partitioning fractions (PF) for both reserves and assimilates, and (4) assess the effects of leaching losses. After the first modification, the model reproduced observed DM patterns, and setting a constant mobilization rate allowed complete use of reserves. Using consistent PF values for both assimilates and reserves was justified because it simplified the model and had only slight effects on predictions. Predicted mobilization efficiencies (ME; g seedling g−1 seed) were greater than measured values, but were improved by accounting for leaching losses. In sensitivity analyses, six seed-related parameters had significant effects on seedling DM at 14 days after seeding (DAS), but none significantly affected mature DM or yields. In other tests, the effects of four traits on seedling growth were assessed over their likely empirical ranges. The start of CO2 assimilation (DAS) had the greatest effect, followed by the start of mobilization and seed mass. Mobilization rate had the smallest effect over its likely range. Finally, simulated and measured early PF values were significantly different, particularly for root partitioning. Predicted DM to 18 DAS using three sets of PF values also differed, although more for total DM per plant than for some plant parts. Using the measured PF values will likely improve the model. It was also demonstrated that simulating reserve mobilization allows dynamic responses to variation in environmental and cultural inputs that may have critical effects on later growth. Thus, the calibration of parameters such as initial DM and leaf area required in other models may be avoided. Most important, using a more process-based approach in DSRICE1 facilitates (or forces) realistic linkages between seedling growth and environment by management interactions, which can improve analyses of crop and weed establishment and management strategies.  相似文献   

6.
Urban and peri-urban agriculture (UPA) contributes significantly to meet increasing food demands of the rapidly growing urban population in West Africa. The intensive vegetable cultivation in UPA gardens with its high nutrient inputs is often reported to operate at large surpluses of nutrients and presumably high turnover rates of organic matter (OM) and nitrogen (N) losses via emanation and leaching. Many of these claims are lacking solid data which would allow suggesting mitigation strategies. Therefore, this study aimed at quantifying gaseous emissions of ammonia (NH3), nitrous oxide (N2O), and carbon dioxide (CO2) in three representative urban gardens of Niamey, Niger using a closed chamber gas monitoring system. Mean annual N emissions (NH3-N and N2O-N) in two gardens using river water for irrigation reached 53 and 48 kg N ha?1 yr?1, respectively, while 25 and 20 Mg C ha?1 yr?1 was lost as CO2-C. In the garden irrigated with sewage water from the city's main wadi, N2O was the main contributor to N losses (68%) which together with NH3 reached 92 kg N ha?1 yr?1, while CO2-C emissions amounted to 26 Mg ha?1 yr?1. Our data indicate that 28% of the total gaseous C emissions and 30–40% of the N emissions occur during the hot dry season from March to May and another 20–25% and 10–20% during the early rainy season from June to July. Especially during these periods more effective nutrient management strategies in UPA vegetable gardens should be applied to increase the nutrient use efficiency in UPA vegetable gardens.  相似文献   

7.
The effects of elevated atmospheric carbon dioxide (CO2) concentration (700 μmol mol?1) on defoliated (three clippings at 3‐week intervals) and undefoliated plants were determined for the C4 grass Themeda triandra, Forsk. The elevated CO2 concentration significantly increased leaf regrowth following defoliation, and total leaf production was greatest in this treatment. Shoot biomass of undefoliated plants was also increased under the elevated CO2 concentration treatment. The primary effect of the elevated CO2 concentration in both defoliated and undefoliated plants was an increase in individual leaf length and mass of dry matter, linked to a higher leaf water content and increased photosynthetic rates at the canopy level. Photosynthetic down‐regulation at the leaf level occurred, but this was compensated for by increased assimilation rates and greater canopy leaf area at the elevated CO2 concentration. Increases in leaf and sheath growth of defoliated plants in the elevated CO2 concentration treatment were lost following a final 3‐week reversion to ambient CO2 concentration, but occurred in plants exposed to the elevated CO2 concentration for the final 3‐week period only. In conclusion, elevated atmospheric CO2 concentration increases shoot growth via increased leaf extension, which is directly dependent on stimulation of concurrent photosynthesis. CO2 responsiveness is sustained following moderate defoliation but is reduced when plants experience reduced vigour as a result of maturation or high frequency of defoliation.  相似文献   

8.
Reduced plant biomass and increased plant-to-plant variability are expected responses to crowding in monocultures, but the underlying processes that control the onset of interplant interference and the establishment of hierarchies among plants within a stand are poorly understood. We tested the hypothesis that early determined plant types (i.e. dominant and dominated individuals) are the cause of the large variability in final kernel number per plant (KNP) usually observed at low values of plant growth rate (PGR) around silking in maize (Zea mays L.). Two hybrids (DK696 and Exp980) of contrasting response to crowding were cropped at different stand densities (6, 9 and 12 plants m−2), row spacings (0.35 and 0.70 m), and water regimes (rainfed and irrigated) during 1999/2000 and 2001/2002 in Argentina. The onset of interplant competition started very early during the cycle, and significant differences (P<0.05) in estimated plant biomass between stand densities were detected as soon as V4–6 (DK696) and V6–7 (Exp980). Plant population and row spacing treatments did not modify the onset of the hierarchical growth among plants, but did affect (P<0.02–0.08) the dynamic of the process. For both hybrids, the rate of change in relative growth between plant types was larger at 9 and 12 plants m−2 (ca. 0.12 g/g per 100 °C day) than at 6 plants m−2 (ca. 0.07 g/g per 100 °C day). For all treatments, the largest difference in estimated shoot biomass between plant types took place between 350 (V7) and 750 °C day (V13) from sowing, and remained constant from V13 onwards. Dominant plants always had more kernels per plant (P<0.05) than the dominated ones, but differences between plant types in PGR around silking were significant (P<0.05) only at 12 plants m−2. Our research confirmed the significant (P<0.01) curvilinear response of KNP to PGR around silking, but also determined a differential response between plant types: the mean of residual values were significantly (P<0.01) larger for dominant than for dominated individuals. Estimated ear biomass at the onset of active kernel growth (R3) reflected the variation in KNP (r2≥0.62), and was significantly (P<0.01) related to estimated plant biomass at the start of active ear growth (ca. V13). This response suggested that the physiological state of each plant at the beginning of the critical period had conditioned its reproductive fate. This early effect of plant type on final KNP seemed to be exerted through current assimilate partitioning during the critical period.  相似文献   

9.
《Field Crops Research》2005,93(1):64-73
Leaf area growth and nitrogen concentration per unit leaf area, Na (g m−2 N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain Na and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84–6.0 g N pot−1) and five rates (0.5–6.0 g pot−1) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, Pmax, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (Na or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between Pmax and Na. The results confirm the ‘maize strategy’: leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the ‘potato strategy’ can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the ‘maize strategy’ for adaptation to N limitation.  相似文献   

10.
《Field Crops Research》2001,71(3):183-193
Light attenuation within a row crop such as maize is influenced by canopy architecture, which has to be defined in terms of the size, shape and orientation of shoot components. Cultural practices that improve the efficiency of light interception affect canopy architecture by modifying such components. Our objectives were to: (i) determine the nature and timing of leaf growth responses to plant population and row spacing; (ii) analyze light attenuation within fully developed maize canopies. Field experiments were conducted at Pergamino (33°56′S, 60°34′W) and Salto (34°33′S, 60°33′W), Argentina, during 1996/1997 and 1997/1998 on silty clay loam soils (Typic Argiudoll) that were well watered and fertilized. Four maize hybrids of contrasting plant type were grown at three plant populations (3, 9 and 12 plants m−2) and two row spacings (0.35 and 0.70 m). Plant population promoted larger changes in shoot organs than did row spacing. As from early stages of crop growth, leaf growth (V6–V8) and azimuthal orientation (V10–V11) were markedly affected by treatments. Modifications in shoot size and leaf orientation suggest shade avoidance reactions, probably triggered by a reduction in the red:far-red ratio of light within the canopy. An interaction between hybrid and plant rectangularity on leaf azimuthal distribution was determined, with one hybrid displaying a random azimuthal leaf distribution under most conditions. This type of hybrid was defined as rigid. The other hybrids showed modified azimuthal distribution of leaves in response to plant rectangularity, even at very low plant populations. These hybrids were defined as plastic. Once maximum leaf area index (LAI) was attained light attenuation did not vary among hybrids and row spacing for plant populations ≥9 plants m−2 (k coefficient: 0.55 and 0.65 for 9 and 12 plants m−2, respectively). A more uniform plant distribution increased light attenuation (k coefficient: 0.37–0.49) only when crop canopies did not reach the critical LAI.  相似文献   

11.
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12.
《Field Crops Research》1998,59(1):63-72
Literature reports show little effect of nitrogen supply on radiation use efficiency in potato and in other dicotyledonous C3 species. This paper tests the hypothesis that potato reduces leaf size rather than leaf nitrogen concentration and photosynthetic capacity when nitrogen is in short supply. Four pot experiments with different rates of nitrogen supply were conducted in glasshouses. For two leaf numbers measurements were made of leaf area, Pmax (rate of photosynthesis for saturating irradiance), specific leaf weight, and concentrations of total nitrogen and nitrate, all as a function of leaf age.Area per leaf was sensitive to nitrogen supply (about a factor 3 between extreme N treatments). Pmax declined with leaf age. There were no systematic effects of nitrogen supply on Pmax and on its change with leaf age, except that in some cases Pmax of leaves of high N treatments was lower than Pmax of low N treatments during part of the life span (leaf age of ca. 20–50 days). The dominant effect of nitrogen supply was on leaf size and not on Pmax or leaf N content. Pmax versus areal organic nitrogen concentration (g N m−2 leaf area) showed considerable scatter and, for a given nitrogen concentration, a slightly lower Pmax for high N treatments than for low N treatments. Comparison with other species showed a comparatively low value of Pmax in potato.  相似文献   

13.
The compositions of essential oils of 19 accessions belonging to six different Achillea species, transferred from the natural habitats in 10 provinces of Iran to the field conditions, were assessed. The relationship between the leaf areas of selected accessions with their essential oil content was also investigated. Essential oil yield of dried plants obtained by hydro-distillation ranged from 0.1 to 2.7% in leaves. Results indicated a significant variation in oil composition among and within species. Total of 94 compounds were identified in 19 accessions belonging to the six species of A. millefolium, A. filipendulina, A. tenuifolia, A. santolina, A. biebersteinii and A. eriophora. The major constituents of the leaves in the tested genotypes were determined as germacrene-D, bicyclogermacrene, camphor, borneol, 1,8-cineole, spathulenol and bornyl acetate. According to the major compounds, four chemotypes were defined as: (I) spathulenol (1.64–34.31%) + camphor (0.2–15.61%) (7 accessions); (II1) germacrene-D (18.78–23.93%) + borneol (7.93–8.26%) + bornyl acetate (11.56–14.66%) (5 accessions); (II2) germacrene-D (13.28–36.28%) + bicyclogermacrene (5.93–8.4%) + 1,8-cineole (15.26–19.41%) + camphor (14.95–23.32%) (2 accessions); (III) borneol + camphor (52.04–63.27) (2 accessions); (IV) germacrene-D (45.86–69.64%) (3 accessions). The relationships of chemotypes with soil type and climatic conditions of collected regions were assessed, as probable reasons of high variations in essential oil components, and discussed.  相似文献   

14.
Safflower (Carthamus tinctorius L.) is a deep-rooted crop which can tolerate water stress and can be grown in rotation with other crop species. Nitrogen is very important for the growth and yield of safflower, however, the effect of N level on chlorophyll content, assimilation rate, transpiration rate, stomatal conductance, substomatal CO2 concentration, and water use efficiency (WUE) have not been determined. A 2-year field study was conducted with the objective to determine the effect of N fertilization on yield, yield components, chlorophyll content, photosynthetic characteristics, and WUE of safflower grown under rainfed conditions. Three rates of N were used (0, 100, and 200 kg N ha−1) and two hybrids (CW9048 and CW9050). N fertilization increased seed yield by an average of 19%, the seed weight per plant by 60%, the seed weight per head by 18%, the number of heads per plant by 32%, and the number of seeds per plant by 41% compared with the control. N level also affected chlorophyll content, N concentration at anthesis, protein, and oil yield. N application increased assimilation rate by an average of 51%, stomatal conductance of water vapour by an average of 27%, and WUE by an average of 60% over the 2 years of the study when compared to the control. The present study indicates that N fertilization can affect yield, yield components, photosynthetic efficiency, and physiology of safflower under rainfed conditions.  相似文献   

15.
《Field Crops Research》1999,62(1):15-21
Total number of initiated leaves and duration from sowing to silking increases when photoperiod is increased during the photoperiod-sensitive phase in maize (Zea mays L.). Little is known, however, about possible other effects of photoperiod and incident photosynthetic photon flux density (PPFD) on rate of development and duration of life cycle. A study was undertaken to quantify effects of photoperiod and incident PPFD from sowing to the 15-leaf stage on rate of leaf appearance and duration of the grain-filling period. The short-season maize hybrid Pioneer 3902 was grown in growth cabinets from sowing to the 15-leaf stage with either (i) a 10 h photoperiod at high PPFD (650 μmol m−2 s−1), (ii) a 20 h photoperiod consisting of 10 h of high PPFD followed by 10 h of low PPFD (5–50 μmol m−2 s−1), or (iii) a 20 h photoperiod of high PPFD. From the 15-leaf stage to maturity the plants were placed under a 16 h photoperiod in a growth room. Increasing photoperiod from 10 to 20 h increased final number of initiated leaves and delayed silking but did not affect rate of leaf appearance. Doubling incident PPFD to a value similar to that under Ontario field conditions during the summer resulted in a 16% increase in rate of leaf appearance and in a significant increase in total number of initiated leaves. Differences in final number of initiated leaves and in rate of leaf appearance from sowing to the 15-leaf stage among treatments resulted in a 4-day difference in silking date between the 10 h photoperiod treatment and the two 20 h photoperiod treatments. Duration of the grain-filling period did not differ among the three treatments.  相似文献   

16.
《Field Crops Research》2005,94(1):67-75
A study was conducted with the objective to determine the influence of (shallow water depth with wetting and drying) SWD on leaf photosynthesis of rice plants under field conditions. Experiments using SWD and traditional irrigations (TRI) were carried out at three transplanting densities, namely D1 (7.5 plants/m2), D2 (13.5 plants/m2) and D3 (19.5 plants/m2) with or without the addition of organic manure (0 and 15 t/ha). A significant increase in leaf net photosynthetic rate by SWD was observed with portable photosynthesis systems in two independent experiments. At both flowering and 20 DAF stages, photosynthetic rate was increased by 14.8% and 33.2% with D2 compared to control. SWD significantly increased specific leaf weight by 17.0% and 11.8% over the control at flowering and 20 DAF stages, respectively. LAI of D2 under SWD was significantly increased by 57.4% at 20 DAF. In addition, SWD with D2 significantly increased the leaf dry weight (DW) at both growing stages. At all the three densities, SWD increased the leaf N content and the increase was 18.9% at D2 density compared with the conventional control. In SWD irrigation, the leaf net photosynthetic rate was positively correlated with the leaf N content (R2 = 0.9413), and the stomatal conductance was also positively correlated with leaf N content (R2 = 0.7359). SWD enhanced sink size by increasing both panicle number and spikelet number per panicle. The increase in spikelet number per panicle was more pronounced in the 15 t ha−1 manure treatment than in the zero-manure treatment. Grain yield was also significantly increased by SWD, with an average increase of 10% across all treatments. SWD with D2 had the highest grain yield under the both cultivars with or without 15 t ha−1 manure treatment, which was 14.7% or 13.9% increase for Liangyoupeijiu and 11.3% or 11.2% for Zhongyou 6 over the control, respectively.  相似文献   

17.
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18.
Different plasticizers (P) such as glycerol, 1,2 propanediol, trimethylol propane, thiodiglycol, and formamide (30% by weight w.r.t. soy protein) were used to prepare soy protein films (coded as SP) by compression molding at 140 °C and 20 MPa. The SP films were immersed in 0.5% (w/v) benzilic acid solution for 26 h to get arylated soy protein films (SP-B) with the evolution of CO2, leading to the formation of diphenylhydroxymethane (DPHM) on the surface. Lotus leaf like structure, on the surface of SP-B film, with high hydrophobicity has been created, supported by the existence of nano/micro spheres. The SP-B and SP films were characterized by Fourier transformed infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, tensile testing, optical transmittance, contact angle, and biodegradation experiments. The mechanical properties, transmittance, and contact angle of SP-B films increased significantly, compared with SP. The SP-B films exhibited high water resistance in the range of 67–82%. These results indicated attractive interactions (often termed as π-interactions) of DPHM aromatic groups took place in the SP-B films resulting in the formation of nanospheres or microspheres. This work provided a good way for increasing the surface hydrophobicity and the mechanical properties of the protein materials through non-covalent interactions.  相似文献   

19.
A 20-year field experiment was employed with the aim of evaluating the effect of tillage systems on biological, chemical and physical aspects of the soil, and to establish whether there was a correlation of these parameters with the incidence of charcoal rot (Macrophomina phaseolina) of soybean and crop yield. The tillage systems evaluated were direct seeding (DS), DS + scarifier (DS + S), minimum tillage (MT) and conventional tillage (CT). DS presented higher values than CT in culturable total fungi (26.33 × 105 vs. 2.33 × 105 CFU g−1 dry soil), total bacteria (182 × 107 vs. 64 × 107 CFU g−1 dry soil), microbial respiration (0.77 mg CO2 g−1 week−1 vs. 0.45 mg CO2 g−1 week−1) and fluorescein diacetate (FDA) hydrolysis (4.17 ug fluorescein g−1 h−1 vs. 1.70 ug fluorescein g−1 h−1 in CT. Fungal and bacterial community fingerprints, by terminal restriction fragment length polymorphism (T-RFLP) analysis, of Intergenic spacer regions of rRNA and 16S rRNA genes, respectively, were influenced by the tillage system. Also FAME (fatty acid methyl ester) profiles showed that microbial community structure in DS and CT was clearly different. DS samples contained significantly higher total microbial biomass than the other tillage treatments, but there were no significant differences in fungal biomass or any consistent trend with respect to stress index. Our results showed that microbial communities were more abundant and active in DS than in CT in response to high nutrient content in soil. Indeed, DS systems presented higher soil OM, total N, K and Ca than CT. Electrical conductivity and aggregate stability (AS) were also improved by DS. Soybean grown in high-quality soil was not affected by charcoal rot, however, under CT, disease incidence in soybean was 54%. These differences were correlated to the higher microbial abundance and activity under DS, the biological component being a key factor determining soil capacity to suppress the soilborne pathogen.  相似文献   

20.
《Field Crops Research》2005,92(1):75-84
The effect of irrigation with saline water on quality of Burley tobacco (cv. C 104) was investigated in Southern Italy over four consecutive years. A rainfed control (RC) was compared with treatments irrigated with volumes equal to crop evapotranspiration of saline waters at 0.5 (NW), 2.5 (SW1), 5 (SW2) and 10 (SW3) dS m−1 electrical conductivity (ECw). In 2000 and 2001 an additional salinity treatment (15 dS m−1 ECw) was included (SW4). The amounts of Cl− added to the soil by irrigation ranged from 36.3 kg ha−1 (good quality water in 1999) to 16.2 Mg ha−1 (saline water at 15 dS m−1 ECw in 2000). Saline irrigation did not affect yield and yield components of cured leaves. In 1998 and 1999 the filling power of Burley tobacco did not change significantly with increasing salinity of the irrigation water. In 2000 and 2001 the filling power of SW2, SW3 and SW4 treatments was significantly less than that of NW. The Cl− content of tobacco grown with SW2 was significantly greater than that grown with NW and there were no differences between SW1 through SW4 treatments. The filling power and the leaf Cl− content were inversely related to the amount of Cl− applied in the range between 40.3 kg ha−1 and 5.1 Mg ha−1. The filling power decreased and Cl− increased up to the SW2 treatment; beyond that level neither Cl− nor filling power changed in response to increasing amounts of Cl− applied. The leaf alkaloid content was unaffected by salinity. Total N was unaffected by either the growing season or the saline treatments. Cigarettes obtained from saline treatments did not burn during the smoking test in 1998. In 1999 cigarettes made from SW1 and SW2 did burn, but those from SW3 did not. In 2000 and 2001 the smoking test was performed only on commercial blends containing 10 or 30% of cut tobacco from saline treatments and both blends burned similarly to cigarettes made entirely from tobacco grown under non-saline conditions. In conclusion, quality of Burley tobacco was unaffected by irrigation with saline water at 2.5 dS m−1 and the inhibitory effect of salinity on burning properties could be overcome by appropriate mixture in commercial blends.  相似文献   

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