首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Three bunches of unripe ‘Williams’ banana fruit of different maturity, 173, 156 and 71 days from bunch emergence, were harvested. Fruit from the top, bottom and middle hands from each bunch were fumigated for 24 h with 1-methylcyclopropene (1-MCP) at 0, 5, 50 or 500 nl l−1 at 20oC. All fruit were then stored at 20oC in air containing 0.1 μl l−1 ethylene and the time taken for each fruit to ripen (green life) was noted. The green life of fruit treated with 500 nl l−1 1-MCP varied with fruit maturity. In the two most mature bunches it was 27.9±2.3 days, 4-fold longer than fruit fumigated with 0 nl l−1 1-MCP (6.7±0.6 days). In the least mature bunch, green life was 39.7±3.0 days, 1.5-fold longer than fruit fumigated with 0 nl l−1 1-MCP (25.7±2.5 days). Most fruit treated with 500 nl l−1 1-MCP showed an unacceptable uneven skin colouration when ripe. There was no significant effect on green life of 1-MCP at 50 nl l−1 and 5 nl l−1. Other fruit from these bunches were not exposed to 1-MCP and were held in ethylene-free air until ripe. In the two most mature bunches, these fruit had a significantly shorter green life (11.2±5.6 days in hand 1; 18.9±4.1 days in hands 4 and 6) than fruit that were fumigated with 500 nl l−1 1-MCP. In the least mature bunch, however, these fruit had a significantly longer green life (56.0±5.9 days) than 1-MCP treated fruit. Since the effectiveness of 1-MCP varied with fruit maturity and in any commercial consignment there is a mixture of fruit maturity, it is concluded that 1-MCP has limited commercial potential for the storage of unripe ‘Williams’ bananas.  相似文献   

2.
Central to the CHanging climate and potential Impacts on Potato yield and quality project (CHIP) was the consideration of the potential impacts of ozone and CO2 on growth and yield of future European Potato crops. Potato crops, cv. Bintje, were exposed to ambient or elevated ozone; targeted daily average, 60 nl l−1 for 8 h, and ambient or elevated CO2; targeted 680 μl l−1 averaged over the full growing season, in open top chambers (OTCs) at six European sites in 1998 and 1999, or to elevated CO2 (550 μl l−1) in Free Air Carbon dioxide Enrichment facilities (FACE) at two sites in both years. Some OTC experiments included 550 μl l−1. Above and below ground biomass were measured at two destructive harvests; at maximum leaf area (MLA) and at final-harvest. Final-harvest fresh weight yields of marketable-size tubers, >35 mm diameter, from ambient conditions ranged from 1 to 12 kg m−2. There was no consistent (P>0.1) CO2×O3 interaction for growth or yield variables at either harvest. No consistent effects of ozone were detected at the maximum-leaf-area harvest. However, at final harvest, ozone had reduced both above-ground biomass and tuber dry weight (P<0.05), particularly of the largest (>50 mm) size class. These yield losses showed linear relationships both with accumulated ozone exposure; AOT40 expressed as nl l−1 h over 40 nl l−1, and with yields from chambered ambient-ozone treatments (P<0.05) but, because of partial confounding between the treatment AOT40s and the ambient-ozone yields in the data, the two relationships were not completely independent. Yields from ambient-ozone treatments, however, explained a significant (P<0.01) amount of the residual variation in ozone effects unexplained by AOT40. When averaged over all experiments, mean dry weights and tuber numbers from both harvests were increased by elevated CO2. Only green leaf number at the MLA harvest was reduced. The CO2 responses varied between sites and years. For marketable-size tubers, this variation was unrelated to variation in ambient-CO2 treatment yields. Yield increases resulting from the 680 μl l−1 and 550 μl l−1 treatments were similar. Thus elevating [CO2] from 550 to 680 μl l−1 was less effective than elevating [CO2] from ambient to 550 μl l−1. On average, CO2 elevation to 680 μl l−1 increased the dry weight of marketable-size tubers by about 17%, which far exceeded the average ozone-induced yield loss of about 5%. The net effect of raising CO2 and O3 concentrations on the European potato crop would be an increase marketable yield.  相似文献   

3.
Potato (Solanum tuberosum L cv. Bintje) was exposed to ambient and elevated carbon dioxide (CO2), to ambient and elevated ozone (O3) and to elevated levels of both gases during two growing seasons, 1998 and 1999. Experiments in open-top chambers (OTC) were carried out in Finland, Sweden, Ireland, United Kingdom, Germany and Belgium and a FACE (Free Air Carbon dioxide Enrichment) experiment was carried out in Italy. In OTCs the plants were grown under ambient CO2 concentrations or with 550 and 680 μl l−1 CO2 alone or in combination with ambient or elevated O3 concentrations (target seasonal mean of 60 nl l−1 8 h per day). In the FACE systems the plants were exposed to ambient or 550 μl l−1 CO2. In the OTC experiments the reducing sugar content of potato tubers decreased significantly with increased concentration of O3. The starch content of potato tubers decreased, with negative impact on tuber quality, but the ascorbic acid concentration increased as a function of the AOT40 (The sum of the differences between hourly ozone concentration and 40 nl l−1 for each hour when the concentration exceeds 40 nl l−1 during a relevant growing season). However, simultaneous exposure to elevated CO2 counteracted the ozone effect. With increase in the CO2 exposure, glycoalkaloid and nitrate concentrations decreased yielding improved quality, while the citric acid concentration decreased causing a higher risk for discoloration after cooking. The amount of dry matter and starch increased significantly in the FACE experiment.  相似文献   

4.
The physiological effects of elevated CO2 and/or O3 on Solanum tuberosum cv. Bintje were examined in Open-Top Chambers during 1998 and 1999 at experimental sites across Europe as part of the EU ‘Changing Climate and Potential Impacts on Potato Yield and Quality’ programme (CHIP). At tuber initiation (≈20 days after emergence, DAE) elevated CO2 (680 μl l−1) induced a 40% increase in the light saturated photosynthetic rate (Asat) of fully expanded leaves in the upper canopy. This was 16% less than expected from short-term exposures of plants grown under ambient CO2 (360 μl l−1) to elevated CO2, indicating that photosynthetic acclimation began at an early stage of crop growth. This effect resulted from a combination of a 12% reduction in stomatal conductance (gs) and a decline in photosynthetic capacity, as indicated by the significant reductions in the maximum carboxylation rate of Rubisco (Vcmax) and light-saturated rate of electron transport (Jmax) under elevated CO2. The seasonal decline in the promotion of photosynthesis by elevated CO2 reflected the concurrent decrease in gs. Vcmax and Jmax were both reduced in plants grown under elevated CO2 until shortly after maximum leaf area (MLA) was attained. Although non-photorespiratory mitochondrial respiration in the light (Rd) increased during the later stages of the season, net photosynthesis was consistently increased by elevated CO2 during the main part of the season. Photosynthetic rate declined more rapidly in response to elevated O3 under ambient CO2, and the detrimental impact of O3 was most obvious after MLA was attained (DAE 40–50). Several exposure indices were compared, with the objective of determining the critical ozone level required to induce physiological effects. The critical O3 exposure above which a 5% reduction in light saturated photosynthetic rate may be expected (expressed in terms of cumulative exposure above 0 nl l−1 O3 between emergence and specific dates during the season (AOT0-cum)) was 11 μl l−1 h; however this value should only be extrapolated beyond the CHIP dataset with caution. The interaction between O3 and stomatal behaviour was more complex, as it was influenced by both long-term and daily exposure levels. Elevated CO2 counteracted the adverse effect of O3 on photosynthesis, perhaps because the observed reduction in stomatal conductance decreased O3 fluxes into the leaves. The results are discussed in the context of nitrogen deficiency, carbohydrate accumulation and yield.  相似文献   

5.
The influence of ultraviolet (UV-C) light (1.4–13.7 kJ m−2 at 254 nm) on the quality and microbial populations of fresh-cut watermelon [Citrulus lanatus (Thunb.) Matsum. and Nakai] was investigated and compared to that of common sanitizing solutions used for fresh-cut produce. Dipping cubes in chlorine (40 μL L−1) and ozone (0.4 μL L−1) was not effective in reducing microbial populations and quality was lower in cubes receiving these aqueous treatments compared to UV-irradiated cubes or control. In commercial trials, exposing packaged watermelons cubes to UV-C light at 4.1 kJ m−2 produced >1 log reduction in microbial populations by the end of the product's shelf life without affecting juice leakage, color and, overall visual quality. In further experimentation, lower UV-C dose (1.4 kJ m−2) reduced microbial populations to a lower degree and only when complete surface exposure was ensured. Higher UV-C doses did not show any difference in microbial populations (6.3 kJ m−2) or result in quality deterioration (13.7 kJ m−2). Spray applications of hydrogen peroxide (2%) and chlorine (40 μL L−1), without subsequent removal of excess water, failed to further decrease microbial load of cubes exposed to UV-C light at 4.1 kJ m−2. When properly utilized, UV-C light is the only method tested in this study that could potentially be used for sanitizing fresh-cut watermelon.  相似文献   

6.
This paper describes the effects of elevated CO2 (550 and 680 μl l−1) and O3 (60 nl l−1 O3 as an 8 h mean), alone or in combination, on canopy development and senescence in potato (Solanum tuberosum L. cv Bintje) across a range of European agro-climatic conditions. The assessments were made within the European CHIP project (CHanging climate and potential Impacts on Potato yield and quality) that was conducted for two growing seasons (1998 and 1999) in free air CO2 enrichment systems (FACE) and open-top chamber facilities (OTCs) at seven European sites. A comparison of chambered and unchambered experimental plots was included to examine the effects of chamber enclosure. Phenological growth stages, plant height, leaf area index (LAI) and the number of green and yellow leaves were recorded non-destructively throughout the growing season and by a destructive intermediate harvest at maximum leaf area (MLA). In the dynamic growth analysis CO2 and O3 effects were studied over three developmental stages: canopy expansion, full canopy and canopy senescence. Chamber enclosures promoted potato crop development (taller plants, more leaves) during the initial growth stages and led to a faster decline of LAI and a higher number of yellow leaves. The growth in ambient plots varied between sites and seasons, as did the scale of the treatment responses. Despite the large background variation, some overall treatment effects could be detected across all sites. Both levels of increased CO2 reduced final plant height in comparison to ambient concentrations, which indicates a premature ending of the active plant growth. At the stage of full canopy and crop senescence the average number of green leaves was significantly (P<0.05) decreased by 680 μl l−1 CO2 (OTC experiments) and LAI showed the same tendency (P=0.07). As there was however no indication of a decreased leaf formation during initial growth and at full canopy, this must have been due to an earlier leaf fall. In the FACE experiments LAI had already began to decline at the stage of full canopy at 550 μl l−1 CO2 but not in ambient CO2 (DAE×CO2, P<0.05). These observations strongly indicated that elevated CO2 induced a premature senescence during full canopy. O3 did not have an overall detrimental effect on crop development during initial growth nor at full canopy, but did induce a faster reduction of LAI during crop senescence (DAE×O3, P<0.05). Final plant height was not affected by O3. There were few CO2×O3 interactions detected. There was a suggestion (P=0.06) that O3 counteracted the CO2-induced decrease of green leaves at full canopy, but on the other hand during crop senescence the decline of LAI due to elevated O3 was faster at ambient compared to elevated CO2 (P<0.05). These responses of canopy development to elevated CO2 and O3 help to explain the treatment responses of potato yield within the CHIP project at sites across Europe.  相似文献   

7.
In rape (Brassica napus L., cv. Global) seed growth mainly depends on husk CO2 assimilation. In irrigated plants, the net photosynthetic rate (Amax) was 10–13 μmol CO2 m−2 s−1 in non-maturing pods and correlated with nitrogen content. The stomatal conductance of water vapour (gH2O) was 0.3 mol m−2 s−1 in non-maturing pods. The photosynthetic nitrogen use efficiency (NUE) was 8.3 μmol CO2g−1 N s−1, about one-third of that in leaves. The photosynthetic water use efficiency (WUE; AmaxgH2O−1) was similar in pods and leaves. In severely droughted plants, the photosynthetic rate was reduced to 38%. The seed growth rate, however, was not influenced by intermittent periods of water stress, indicating translocation of assimilates to the seeds. The drought resistant character of the pods was due to low specific area, succulence, low stomatal conductance causing a small decrease of ΔΨ day−1 during soil drying and maintenance of high relative water content during severe drought. A mathematical formulation of the pod water release curve was undertaken. © (1997) Elsevier Science B.V.  相似文献   

8.
In intensive integrated crop-livestock farming systems, the surplus of N at the farm scale may be large and reflects on the N balance at the field scale. A study was conducted to assess the N fertilizer efficiency in four private farms in intensively cropped areas of NW Italy, and to monitor the effects of agricultural practices on the mineral N concentration of the soil solution, sampled every 2 weeks for 2 years and considered as an indicator of potential leaching. Two cultivation systems were compared in each farm, one involving continuous maize rotation, the other assuring a continuous soil cover (permanent meadow or winter cereal-maize double cropping system). The fertilization level in the arable crops was high (369–509 kg N ha−1 year−1) compared to the crop removals, and resulted in a low efficiency, as indicated by the four examined efficiency indexes (calculated N surplus, N removal-fertilizer ratio, N apparent recovery, N use efficiency). The soil-water-nitrate concentration showed large temporal variations in the range of 1–150 mg l−1 for five out of the eight cropping situations, while concentrations smaller than 10 mg l−1 were always recorded in the meadows and in one of the four soils (Aeric epiaquept). The fertilizer management that characterized each cropping system affected the soil-mineral-nitrate content in shallow arable soils. The longer soil cover duration in double-cropping systems did not result in a reduction of soil N compared to maize as a single crop, not even in winter (the bare-soil intercropping period in maize-based systems). However, the temporal oscillations of the concentration were buffered by the crop cover duration and by the presence of a shallow water table (1 m deep) in the soil profile. The average nitrate content of the soil could be predicted by the N uptake of the crop, the N removal–fertilizer ratio, the soil pH and sand content, however no simple explanatory relationship was found with the experimental factors. Hence, in farm conditions, in the absence of sufficient data for a deterministic model approach, the target of reducing the risk of leaching should be achieved by maximizing the fertilizer efficiency.  相似文献   

9.
Manganese deficiency symptoms are more often observed in crops at early stages of growth since Mn2+ can be easily mobilized from the surface soil. The objectives of this study were to evaluate some of the popular rotation crops grown in Hungary for tolerance to low external Mn2+ levels and to determine the critical tissue concentration for Mn2+ deficiency during early stages of growth. Indicator plants of sunflower (Helianthus annuus L.) were grown with NPKCaMg-fertilization induced of 0.0425–0.0700 g kg−1; of tobacco (Nicotiana tabacum L.) 0.0237–0.0337 g kg−1; of triticale (x Triticosecale W.) 0.0103–0.0327 g NH4-acetate + EDTA extractable soil Mn2+ kg−1; and were grown for 73, 50, and 191 days. The minimum Mn2+ concentration required in soil nutrient contents was 0.0425 g kg−1 for sunflower, 0.0243 g kg−1 for tobacco, and 0.0103 g kg−1 for triticale. Sunflower, tobacco and triticale achieved optimum growth from 0.048 to 0.065 g Mn2+ kg−1, from 0.0249 to 0.0321 g Mn2+ kg−1, and from 0.0287 to 0.0296 g Mn2+ kg−1, respectively. Critical ABP's dry weight Mn2+ concentration at early stages of growth was 0.0536 g kg−1 in sunflower, 0.458 g kg−1 in tobacco, and 0.1938 g kg−1 in triticale. Our results demonstrate that the tolerance to low external Mn2+ (triticale <0.0302 g kg−1; sunflower <0.0562 g kg−1; tobacco <0.0693 g kg−1) and the critical tissue Mn2+ levels for deficiency varied significantly among crop species tested.  相似文献   

10.
Measurements of stomatal conductance on field-grown potato (Solanum tuberosum L.) cv. Bintje from the CHIP programme were combined to study the response to environmental factors. 3274 data points were used. Data were obtained from five sites: Jokioinen in Finland, Östad in Sweden, Giessen in Germany, Tervuren in Belgium and Sutton Bonnington in UK. Measurements were made in open-top chamber treatments with ozone and carbon dioxide exposure and in the ambient air. A typical light response curve was obtained with light saturation at approximately 400 μmol m−2 s−1 photosynthetically active radiation (PAR). The leaf temperature optimum for stomatal conductance was 29 °C. The stomatal conductance declined strongly at leaf-to-air vapour pressure differences >20 hPa. An elevated carbon dioxide concentration (680 μl l−1) reduced the stomatal conductance by up to approximately 20%. Elevated ozone reduced the stomatal conductance towards the end of the growth period, in addition to the negative effect by ordinary senescence on stomatal conductance. A multiplicative model, based on the boundary line technique, was used to estimate the relationship between stomatal conductance and the environmental variables. Test with the data sets from two sites providing sufficient data, Östad and Giessen, showed that the multiplicative model had R2-values of 0.60 and 0.42, respectively, for the relationship between calculated and observed conductance. Test of the model with an independent data set from an open-top chamber experiment with the potato cultivar Kardal showed an R2 of 0.59 between calculated and observed conductance. The conductance model was used to estimate the accumulated ozone uptake (CUO3) by potato leaves from emergence to harvest. The relationship between CUO3 and relative yield loss, using a threshold for the ozone uptake rate of 7 nmol m−2 s−1, provided a higher R2-value (0.45) than CUO3 without any threshold and relationships based on the accumulated exposure over 40 nmol mol−1 (AOT40) or the sum of all hourly average ozone concentrations exceeding 60 nmol mol−1 (SUM06). All four relationships were however statistically significant.  相似文献   

11.
In order to evaluate the possibility of reducing energy input in giant reed (Arundo donax L.) as a perennial biomass crop, a field experiment was carried out from 1996 to 2001 in central Italy. Crop yield response to fertilisation (200–80–200 kg ha−1 N–P–K), harvest time (autumn and winter) and plant density (20,000 and 40,000 plants per ha) was evaluated. The energy balance was assessed considering the energy costs of production inputs and the energy output obtained by the transformation of the final product. The crop yield increased by +50% from the establishment period to the 2nd year of growth when it achieved the highest dry matter yield. The mature crop displayed on average annual production rates of 3 kg dry matter m−2, with maximum values obtained in fertilised plot and during winter harvest time.

Fertilisation mainly enhanced dry matter yield in the initial period (+0.7 kg dry matter m−2 as years 1–6 mean value). The biomass water content was affected by harvest time, decreasing by about 10% from autumn to winter. With regard to plant density, higher dry matter yields were achieved with 20,000 plants per ha (+0.3 kg dry matter m−2 as years 1–6 mean value).

The total energy input decreased from fertilised (18 GJ ha−1) to not fertilised crops (4 GJ ha−1). The higher energetic input was represented by fertilisation which involved 14 GJ ha−1 (fertilisers plus their distribution) of total energy costs. This value represents 78% of total energy inputs for fertilised crops.

Giant reed biomass calorific mean value (i.e., the calorific value obtained from combustion of biomass sample in an adiabatic system) was about 17 MJ kg−1 dry matter and it was not affected by fertilisation, or by plant density or harvest time. Fertilisation enhanced crop biomass yield from 23 to 27 dry tonnes per ha (years 1–6 mean value). This 15% increase was possible with an energy consumption of 70% of the overall energy cost. Maximum energy yield output was 496 GJ ha−1, obtained with 20,000 plants per ha and fertilisation. From the establishment period to 2nd–6th year of growth the energy production efficiency (as ratio between energy output and energy input per ha) and the net energy yield (as difference between energy output and energy input per ha) increased due to the low crop dry biomass yield and the high energy costs for crop planting. The energy production efficiency and net energy yield were also affected by fertilisation and plant density. In the mature crop the energy efficiency was highest without fertilisation both with 20,000 (131 GJ ha−1) and 40,000 plants per ha (119 GJ ha−1).  相似文献   


12.
The aim of this study was to determine the effects of 1-methylcyclopropene, 1-MCP (1 μL L−1 for 24 h at 5 °C) on quality attributes and shelf life of fresh-cut strawberries. The 1-MCP was applied before (whole product) and/or after cutting (wedges), followed by storage in a continuous flow of air or air +1 μL L−1 C2H4. The combined effects of 1-MCP and CaCl2 dips (1% for 2 min) and/or CA (3 kPa O2 + 10 kPa CO2) were also examined. The application of only 1-MCP before and/or after cutting did not have a significant effect on firmness and appearance quality during storage for up to 12 days at 5 °C. The exposure to a continuous flow of 1 μL L−1 C2H4 in air during storage did not increase the softening rate. 1-MCP applied before cutting or both before and after cutting of the strawberries increased respiration rates but reduced C2H4 production rates. Exposure to 1-MCP had a synergistic effect when combined with CaCl2 plus CA. The combined treatment of 1-MCP + CaCl2 + CA slowed down softening, deterioration rates, TA and microbial growth. Compared to the control, which had a 6-day shelf life, the shelf life of fresh-cut strawberries subjected to the combination treatment was extended to 9 days at 5 °C.  相似文献   

13.
Information about the effect of the cropping history on the seed yield of oil-seed rape is extremely scarce. In 1992/93 and 1994/95, the effects of different preceding crop combinations (winter barley and winter wheat as preceding crops, oil-seed rape and wheat as pre-preceding crops) on the yield of six double low oil-seed rape cultivars were examined in a field trial at Hohenschulen Experimental Farm, north-west Germany. In addition, eight nitrogen treatments (different amounts and distribution patterns) were tested for their potential to reduce negative effects of the preceding crops. Following the cropping sequence of oil-seed rape then wheat, oil-seed rape yielded only 3.12 t ha−1; after oil-seed rape then barley, the yield was 3.43 t ha−1 compared with 3.77 t ha−1 following wheat then barley and 3.71 t ha−1 following wheat then wheat. The number of seeds per m2 showed a similar pattern, whereas the thousand-seed weight partly compensated for the reduced seed number. It was highest if oil-seed rape was grown 2 years previously. The cultivars differed significantly in their yield potential. Express (3.79 t ha−1) yielded 0.6 t ha−1 more than Falcon (3.18 t ha−1). Increasing amounts of fertilizer-N (80–200 kg N ha−1) increased the seed yield from 3.21 t ha−1 to 3.84 t ha−1. Changes in the distribution pattern within one fertilizer amount had no effect on seed yield. In addition, no interactions between preceding crop combination and the different cultivars or N treatments occurred. It is concluded that crop management cannot totally eliminate the negative effects of an unfavourable cropping history on the seed yield of oil-seed rape.  相似文献   

14.
The influence of aqueous 1-methylcyclopropene (1-MCP) concentration, immersion duration, and solution longevity on the ripening of early ripening-stage tomato (Solanum lycopersicum L.) has been investigated. Tomato fruit at the breaker-turning stage were fully immersed in aqueous 1-MCP at 50, 200, 400 and 600 μg L−1 for 1 min, quickly dried, and then stored at 20 °C. Ethylene production, respiration, surface color development, and rate of accumulation of lycopene and polygalacturonase (PG) activity were suppressed and/or delayed in fruit exposed to aqueous 1-MCP. Suppression of ripening was concentration dependent, with maximum inhibition in response to 1 min immersion occurring at concentrations of 400 and 600 μg L−1. Climacteric ethylene peaks were delayed approximately 6, 7, and 9 d and respiration was strongly suppressed in fruit treated with aqueous 1-MCP at 200, 400, and 600 μg L−1, respectively, compared with control fruit. Fruit firmness, lycopene content, PG activity, and surface hue of fruit treated at the three higher levels remained strongly suppressed compared with control. Skin hue values and pericarp lycopene content in response to treatment at the subthreshold 50 μg L−1 provided evidence for differential ripening suppression in external versus internal tissues. Maximum delay of softening and surface color development in response to 50 μg L−1 aqueous 1-MCP occurred following immersion periods of between 6 and 12 min. Factors affecting fruit penetration by aqueous 1-MCP and mechanisms contributing to recovery from 1-MCP-induced ripening inhibition are discussed.  相似文献   

15.
The residual effect of 2-year-old swards of clover-ryegrass mixture and ryegrass in monoculture on yield and N uptake in a subsequent winter wheat crop was investigated by use of the 15N dilution method and by mathematical modelling. The amount of N in the wheat crop, derived from clover-ryegrass residues was 25–43% greater than that derived from residues of ryegrass which had been growing in monoculture. Expressed in absolute values, the N uptake in the subsequent winter wheat crop was 23–28 kg N ha −1 greater after clover-ryegrass mixture than after ryegrass in monoculture. Up to about 54 kg N ha−1 of the N mineralised from the clover-ryegrass crop was calculated to be leached, whereas only 11 kg N ha−1 was leached following ryegrass in monoculture.  相似文献   

16.
Potato cv. Bintje was grown in open-top-chambers and free-air-CO2-enrichment systems at 7 sites across Europe for 2 years (1998–99). The effect of different treatments (CO2 enrichment and O3 fumigation) on the chlorophyll content of fully expanded upper and lower canopy leaves was investigated collecting Minolta SPAD-502 meter readings. In both CO2 treated and O3 fumigated plants, leaves had lower chlorophyll content than those in ambient air controls; season-long chlorophyll averages were 9.3% lower in the ‘CO2’ treatments, 9.1% lower in ‘O3’ treatments and 12.3% lower in ‘CO2+O3’ treatments. The analysis of chlorophyll content in three different growth phases (Emergence–Tuber Initiation; Tuber Initiation–Maximum Leaf Area; Maximum Leaf Area–Harvest) showed that in the early growth period, i.e. before tuber initiation there was a slight indication for an higher chlorophyll content at elevated CO2 (+3.8%) or O3 (+1.7%). However, from tuber initiation onwards the leaves of plants grown under elevated CO2 or O3 showed a progressively lower chlorophyll content (−4.8% for CO2 treatments and −2.6% for O3 treatments) indicating a faster senescence of leaves that increased during the late growth period (−12.8% for CO2 treatments and −12.7% for O3 treatments) and that was enhanced by CO2–O3 interaction (−17.8%).  相似文献   

17.
New high yielding early maturing cultivars of lupins have been introduced in north-west Europe as grain protein crops in crop rotations. This paper reports on a comparative study of lupins with peas and oats, and of their effect on yield of subsequent winter barley crops. These crops were given five levels of N under irrigated and non-irrigated conditions on sand and loam. Under rain fed conditions the grain yield of pea, oat and lupin varied between 24–36, 34–53 and 18–37 hkg DM ha−1, respectively. Supplemental irrigation raised grain yield of oat to 50–60 hkg DM ha−1, while grain yield in pea was not affected and grain yield in lupin in most cases decreased due to gray mould attack and excessive vegetative growth in the indeterminate lupin variety. Under rain fed conditions, the grain nitrogen content of pea, oat and lupin varied between 137–172, 61–80 and 189–226 kg N ha−1, respectively, and was significantly higher in lupin as compared with pea. On sandy soil, similar low-root densities were found for pea, oat and lupin below 30 cm depth. On sand, at final harvest the residual soil-N of lupin and pea, as measured in a subsequent winter barley crop not supplied with N fertilizer, was 15 and 8–10 kg N ha−1 higher than in winter barley following oat, respectively. The nature of the probably more N-root residues of lupin is discussed. On loam, the residual N of lupin and pea was similar, 18–27 kg N ha−1. On sand, under rain fed conditions preceding lupin and pea as compared with oat, increased the barley grain yield at zero N-application 77 and 49%, respectively; the effect of lupin was significantly higher than that of pea until the highest N-level 120 kg N-application ha−1. On loam under rain fed conditions preceding lupin and pea increased the barley grain yield at zero N-application by 36 and 62%, respectively, as compared with oat; at N-application>60 kg N ha−1 the grain yield was similar after all three crops. For both soil types the same level of effect was found under irrigated conditions. Conclusions: Supplemental irrigation might result in lower grain yield in lupin due to gray mould attack and excessive growth if indeterminate lupin varieties are used. Grain nitrogen yield of lupin is significantly higher than that of pea. On sand, the effect of lupin on the subsequent winter barley grain yield is significantly higher than that of pea, probably due to greater N-root nitrogen residues. On loam, lupin and pea have similar effects on the subsequent winter barley crop.  相似文献   

18.
Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha−1) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha−1 than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha−1. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha−1. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha−1 than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha−1 than in rye and weeds with 0 or 60 kg N ha−1. Increased N supplied by hairy vetch or 120–130 kg N ha−1 increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha−1. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha−1. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.  相似文献   

19.
Spring wheat cv. Minaret was grown in open-top chambers at four sites across Europe. The effect of different treatments (CO2 enrichment, O3 fumigation, drought stress and temperature) on the chlorophyll content of the flag leaf was investigated using the MINOLTA SPAD-502 meter. Under optimum growth conditions the maximum chlorophyll content, which was reached at anthesis, was consistent among the sites ranging from 460 to 500 mg chlorophyll m−2. No significant effect of elevated CO2 or O3 was observed at anthesis. Leaf senescence, indicated by the chlorophyll breakdown after anthesis, was relatively constant in the control chambers. Under control conditions, thermal time until 50% chlorophyll loss was reached was 600°C day. Elevated CO2 caused a faster decline in chlorophyll content (thermal time until 50% chlorophyll loss was reduced to 500–580°C day) indicating a faster rate of plant development at two experimental sites. The effect of ozone on chlorophyll content depended on the time and dose of O3 exposure. During grain filling, high O3 concentrations induced premature senescence of the flag leaves (up to −130°C day). This deleterious effect was mitigated by elevated CO2. Drought stress led to faster chlorophyll breakdown irrespective of CO2 treatment.  相似文献   

20.
Although a high biomass yield is obtained from established Miscanthus crops, previous studies have shown that fertilizer requirements are relatively low. As little information on the role of the Miscanthus roots in nutrient acquisition is available, a study was conducted to gather data on the Miscanthus root system and root nutrient content. Therefore in 1992, the root distribution pattern of an established Miscanthus crop was measured in field trials using the trench profile and the auger methods. Also, in 1994/1995, seasonal changes in root length density (RLD) and root nutrient content were monitored three times during the vegetation period.

The trench profile method showed that roots were present to the maximum depth measured of 250 cm. The top soil (0–30 cm) contained 28% of root biomass, while nearly half of the total roots were present in soil layers deeper than 90 cm. Using the auger method, we found that RLD values in the topsoil decreased with increasing distance from the centre of the plants. Below 30 cm, RLD decreased markedly, and differences in root length in the soil between plants were less pronounced. The total root dry weight down to 180 cm tended to increase from May 1994 (10.6 t ha−1) to November 1994 (13.9 t ha−1) and then decreased again until March 1995 (11.5 t ha−1). Nutrient concentrations in the roots decreased with increasing depth. The concentrations of N (0.7–1.4%) and K (0.6–1.2%) were clearly higher than those of P (0.06–0.17%). The mean values for N, P and K contents of the roots of all three sampling dates in 1994/1995 were 109.2 kg N ha−1, 10.6 kg P ha−1 and 92.5 kg K ha−1.

Although our results showed that RLD values for Miscanthus in the topsoil are lower than for annual crops, the greater rooting depth and the higher RLD of Miscanthus in the subsoil mean that nutrient uptake from the subsoil is potentially greater. This enables Miscanthus crops to overcome periods of low nutrient (and water) availability especially during periods of rapid above-ground biomass growth.  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号