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1.
《Field Crops Research》2004,86(1):67-80
Mungbean (Vigna radiata L.), as a dryland grain legume, is exposed to varying timing and severity of water deficit, which results in variability in grain yield, nitrogen accumulation and grain quality. In this field study, mungbean crops were exposed to varying timing and severity of water deficit in order to examine: (1) contribution of the second flush of pods to final grain yield with variable timing of relief from water deficit, (2) the sensitivity to water deficit of the accumulation of biomass and nitrogen (N) and its partitioning to grain, and (3) how the timing of water deficit affects the pattern of harvest index (HI) increase through pod filling. The results showed that the contribution of the second flush to final yield is highly variable (1–56%) and can be considerable, especially where mid-season stress is relieved at early pod filling. The capacity to produce a second flush of pods did not compensate fully for yield reduction due to water stress. Relief from mid-season stress also resulted in continued leaf production, N2 fixation and vegetative biomass accumulation during pod filling. Despite the wide variation in the degree of change in vegetative biomass and N during pod filling, there were strong relationships between grain yield and net-above-ground biomass at maturity, and grain N and above-ground N at maturity. Only in the extreme situations were HI and nitrogen HI affected noticeably. In those treatments where there was a large second flush of pods, there was a pronounced biphasic pattern to pod number production, with HI also progressing through two distinct phases of increase separated by a plateau. The proportion of grain yield contributed to by biomass produced before pod filling varied from 0 to 61% with the contribution greatest under terminal water deficit. There was a larger effect of water deficit on N accumulation, and hence N2 fixation, than on biomass accumulation. The study confirmed the applicability of a number of long-standing physiological concepts to the analysis of the effect of water deficit on mungbean, but also highlighted the difficulty of accounting for timing effects of water deficit where second flushes of pods alter canopy development, biomass and yield accumulation, and N dynamics.  相似文献   

2.
Drought is a major factor limiting yield improvement of mung bean (Vigna radiata (L.) Wilczek) in the sub-humid, dry and intermediate zones of Sri Lanka. Therefore, the objective of this study was to analyze the yield response of mung bean to irrigation at various phenological stages in terms of radiation interception, radiation-use efficiency and harvest index. Four field experiments were carried out at two sites (Maha-Illuppallama and Kundasale) during the short, dry yala season over two years (1995 and 1996). The life cycle of mung bean was divided into three stages: vegetative (from germination to appearance of first flower); flowering (from appearance of first flower to 75% pod initiation); and pod-filling (from 75% pod initiation to maturity). Eight irrigation treatments were defined as all possible combinations of irrigation during the three stages. Maximum potential soil water deficits (PSWD) ranging from 127 to 376 mm developed as a result of keeping different combinations of stages unirrigated. Maximum LAI (Lm) and the fraction of incoming radiation intercepted (F) increased significantly with the number of stages irrigated. Specifically, treatments which included irrigation during the vegetative stage achieved large Lm and F. Radiation-use efficiency (RUE), maximum total biomass (Wm), harvest index (HI) and seed yield (Y) also showed a significant positive response to the number of stages irrigated. However, all the above parameters were significantly greater in treatments which included irrigation during the pod-filling and flowering stages. The treatment which received irrigation only during the vegetative stage had significantly lower RUE, Wm, HI and Y despite having higher Lm and F. Therefore, irrigation is critical during pod-filling and flowering stages mainly because of the higher LAI during these periods and, consequently, the greater demand for water. Lack of irrigation during these critical stages resulted in the development of significant PSWD with adverse effects on photosynthesis and consequently decreased RUE. Moreover, water stress during flowering and pod-filling stages significantly reduced pod initiation and pod growth rates and thereby reduced HI. It is concluded that to maximize mung bean yields in the dry season of the sub-humid zones of Sri Lanka, irrigation should extend across all phenological stages, specially the pod-filling stage.  相似文献   

3.
研究结果表明,在干旱条件下出口型菜用大豆品种始花期和鼓粒初期各灌水一次,能提高籽粒鼓粒速度,延长鼓粒持续期,促进籽粒饱满,增加标准荚数,提高鲜荚产量和标准荚产量.鼓粒速度越快,百粒鲜重、单株鲜荚重、单株标准荚重越大.  相似文献   

4.
As the challenges toward increasing water for irrigation become more prevalent, knowledge of crop yield response to water can facilitate the development of irrigation strategies for improving agricultural productivity. Experiments were conducted to quantify maize yield response to soil moisture deficits, and assess the effects of deficit irrigation (DI) on water productivity (water and irrigation water use efficiency, WUE and IWUE). Five irrigation treatments were investigated: a full irrigation (I1) with a water application of 60 mm and four deficit treatments with application depths of 50 (I2), 40 (I3), 30 (I4), and 20 mm (I5). On average, the highest grain yield observed was 1008.41 g m?2 in I1, and water deficits resulted in significant (p < .05) reduction within range of 6 and 33%. This reduction was significantly correlated with a decline in grain number per ear, 1000-grain weight, ear number per plant, and number of grain per row. The highest correlation was found between grain yield and grain number per ear. The WUE and IWUE were within range of 1.52–2.25 kg m?3 and 1.64–4.53 kg m?3, respectively. High water productivity without significant reduction in yield (<13%) for I2 and I3 compared to the yield in I1 indicates that these water depths are viable practices to promote sustainable water development. Also, for assessing the benefits of irrigation practices in the region crop water production functions were established. Maize yield response to water stress was estimated as .92, suggesting the environmental conditions are conducive for implementing DI strategies.  相似文献   

5.
为了解冬小麦不同冠层叶片光合和蒸腾作用特征以及随水分条件的变化规律,通过田间试验,以冬小麦京冬22为试验材料,设置0 mm（T0）、220 mm（T1）、280 mm（T2）3种水分处理,比较分析了冬小麦不同冠层叶片净光合速率、蒸腾速率及水分利用效率对光合有效辐射和灌溉响应的差异。结果表明,三种水分处理下,冬小麦不同冠层叶片的蒸腾速率和光合速率随光合有效辐射的增加而增加,随后趋于平缓。不同冠层叶片蒸腾速率、光合速率对光合有效辐射的响应表现为上层>中层>下层;不同冠层叶片WUE对光合有效辐射的响应表现为上中层>下层。光合有效辐射相同时,灌水处理（T1和T2）的叶片光合蒸腾速率均高于不灌水处理（T0）。T1、T2处理下,叶片光合速率对光合有效辐射响应在整个生育期内表现为灌浆期>抽穗期>成熟期>拔节期,蒸腾速率对光合有效辐射响应在整个生育期内表现为抽穗期>灌浆期>拔节期>成熟期;T0处理下,叶片光合速率对光合有效辐射响应在整个生育期内表现为灌浆期>拔节期>抽穗期>成熟期,蒸腾速率对光合有效辐射响应在冬小麦整个生育期内表现不显著。因此,在进行小麦叶片到单株光合蒸腾尺度拓展估算时,应考虑冠层位置和水分条件对拓展结果的影响。  相似文献   

6.
A field study was carried out from 1995 to 1997 in order to determine the effect of irrigation and water stress imposed at different development stages on vegetative growth, grain yield and other yield components of corn (Zea mays L.). The field trials were conducted on a silty loam Entisol soil, with Pioneer 3377 corn hybrid. A randomised complete block design with three replications was used. Four known growth stages of the plant were considered and a total of 16 (including rain fed) irrigation treatments were applied. The effect of irrigation or water stress at any stage of development on plant height, leaf area index, grain yield per hectare, as well number of ears per plant, grain yield per cob and 1000 kernels weight, were evaluated. Results of this 3-year study show that all vegetative and yield parameters were significantly affected by water shortage in the soil profile due to omitted irrigation during the sensitive tasselling and cob formation stages. Water stress occurring during vegetative and tasselling stages reduced plant height, as well as leaf area development. Short-duration water deficits during the rapid vegetative growth period caused 28–32% loss of final dry matter weight. Highest yields were observed in the fully irrigated control (VTCM) and the treatment which allowed water stress during the vegetative growth stage (TCM). Even a single irrigation omission during one of the sensitive growth stages, caused up to 40% grain yield losses during dry years such as 1996. Much greater losses of 66–93% could be expected as a result of prolonged water stress during tasselling and ear formation stages. Seasonal irrigation water amounts required for non-stressed production varied by year from 390 to 575 mm. Yield response factor (ky) values (unitless parameter) relating yield loss to water deficits) obtained for the first, second and third experimental years were determined to be 1.22, 1.36 and 0.81, respectively.  相似文献   

7.
Effect of PRD (partial rootzone drying) on yield and yield components of canola (Brassica napus L.) was investigated in greenhouse conditions. The treatments were: T1, full watering of both sides of roots; T2, alternate irrigation on both sides; T3, half of irrigation water in T1 was given to one side; T4, same as T3 but without plate; T5, same as T2 but without plate. In T1, T2, and T3 treatments, the boxes were evenly separated into two compartments with thin plates. The results showed that grain yield of T1 to T5 treatments was 18.11, 16.38, 12.44, 9.29, and 8.66 g plant−1. T2 treatment increased plant height by 46.9% and 1000-seed weight by 17.8%, but reduced lateral branches by 16.7% and number of pods by 24%, over T1 treatment. T2 treatment was the most efficient (irrigation water use efficiency = 0.679 kg m−3) and treatment T5 was the least efficient (0.359 kg m−3). The difference between irrigation water use efficiency (IWUE) of T2 and T5, and T3 and T4 treatments, was significant (p < 0.05). Therefore, halving the amount of applied irrigation water and applying this water alternatively on both sides of the root zone will produce the highest IWUE. This study showed that PRD irrigation management has high influence on rooting system of canola. This phenomenon could affect nutrients uptake and consequently all aspects of plant growth and development.  相似文献   

8.
利用长期定位试验,设置密度(D1：60 000株/hm2,D2：90 000株/hm2)、耕法(T1：少耕,T2：常规耕作)与化控(R1：喷化控剂,R2：喷清水)三因素试验,分析不同处理玉米产量及其形成过程和冠层光合特性。结果表明,D1条件下,T1R1处理子粒产量、穗粒数较T2R2处理显著增加27%～40.5%、19.6%～27.3%;D2条件下,T1R1处理子粒产量、穗粒数较T2R2处理显著增加22.9%～24.9%、14%～21.3%。少耕和化控处理显著影响植株冠层结构,降低了玉米的植株高度、穗位系数、上部叶片的叶面积,提高了植株上层和中层叶向值及上部冠层的透光率;少耕和化控处理提高了叶片单位面积光能的吸收(ABS/CS0)、捕获(TR0/CS0),在高密度条件下表现明显差异。综上,在密植条件下,少耕和化控耦合优化了玉米密植群体冠层结构,增强了对光能的截获、吸收与传递能力,最终显著增加子粒产量。  相似文献   

9.
Appropriate benchmarks for water productivity (WP), defined here as the amount of grain yield produced per unit of water supply, are needed to help identify and diagnose inefficiencies in crop production and water management in irrigated systems. Such analysis is lacking for maize in the Western U.S. Corn Belt where irrigated production represents 58% of total maize output. The objective of this paper was to quantify WP and identify opportunities to increase it in irrigated maize systems of central Nebraska. In the present study, a benchmark for maize WP was (i) developed from relationships between simulated yield and seasonal water supply (stored soil water and sowing-to-maturity rainfall plus irrigation) documented in a previous study; (ii) validated against actual data from crops grown with good management over a wide range of environments and water supply regimes (n = 123); and (iii) used to evaluate WP of farmer's fields in central Nebraska using a 3-y database (2005–2007) that included field-specific values for yield and applied irrigation (n = 777). The database was also used to quantify applied irrigation, irrigation water-use efficiency (IWUE; amount of yield produced per unit of applied irrigation), and the impact of agronomic practices on both parameters. Opportunities to improve irrigation management were evaluated using a maize simulation model in combination with actual weather records and detailed data on soil properties and crop management collected from a subset of fields (n = 123). The linear function derived from the relationship between simulated grain yield and seasonal water supply, namely the mean WP function (slope = 19.3 kg ha−1 mm−1; x-intercept = 100 mm), proved to be a robust benchmark for maize WP when compared with actual yield and water supply data. Average farmer's WP in central Nebraska was ∼73% of the WP derived from the slope of the mean WP function. A substantial number of fields (55% of total) had water supply in excess of that required to achieve yield potential (900 mm). Pivot irrigation (instead of surface irrigation) and conservation tillage in fields under soybean–maize rotation had the greatest IWUE and yield. Applied irrigation was 41 and 20% less under pivot and conservation tillage than under surface irrigation and conventional tillage, respectively. Simulation analysis showed that up to 32% of the annual water volume allocated to irrigated maize in the region could be saved with little yield penalty, by switching current surface systems to pivot, improving irrigation schedules to be more synchronous with crop water requirements and, as a fine-tune option, adopting limited irrigation.  相似文献   

10.
Lesquerella fendleri (Gray) Wats. is a potential new oilseed crop for the arid southwestern United States. Lesquerella seed oil with similar properties as castor oil is being considered as a domestic replacement for the imported castor oil. Development of new crops with low irrigation needs is of high priority. Because the most critical stage of sensitivity to moisture deficits has not been determined in Lesquerella species, the objectives of this study were: (i) to identify the most critical stage or stages for moisture deficit and, (ii) to determine the effect of moisture deficit on yield, yield components, oil and fatty acid composition. Two-year field studies were conducted at the New Mexico State University, Leyendecker Plant Science Research Center. The experimental design was a randomized complete block. The treatments consisted of (a) T1: Continuous favorable soil moisture [irrigated at 50% soil water depletion (SWD)]. (b) T2: Moisture stress (75% SWD) from establishment to initial flowering with no stress from flowering to final harvest (50% SWD). (c) T3: No stress imposed from establishment to initial flowering (50% SWD) followed by stress to final harvest (75% SWD). (d) T4: Moisture stress (75% SWD) from establishment to final harvest. The amount of water applied ranged from 810 to 729 mm for the first year, and 810 to 625 mm for the second year. Seed weight per plant and number of pods per plant were generally higher when water availability was maintained at or above 50% SWD throughout the growing season. Neither seed number per pod nor seed size was influenced by irrigation treatments. Lesquerella was more sensitive to water availability during flowering and seed development as a greater loss in seed yield occurred when irrigation was delayed to 75% SWD during that stage of development. Seed yield and dry matter production from the 2 year field studies were closely related to the seasonal cumulative evapotranspiration. For each millimeter of evapotranspiration, seed yield increased from 1.8 kg ha−1 mm in 1994–1995 to 1.3 kg ha−1 mm for 1995–1996. The dry matter production increased 13.4 kg ha−1 for each mm increase in seasonal evapotranspiration during 1994–1995. This relationship was a second order polynomial with an R2 of 0.86 during 1995–1996. The WUEgr and WUEdm were highest under the most favorable water availability conditions for growth and seed development. Delaying irrigation to 75% SWD throughout the crop growth period resulted in the lowest oil content. Lesquerolic acid content was not affected by irrigation during both the growing seasons.  相似文献   

11.
《Field Crops Research》2002,78(1):65-74
Alfalfa (Medicago sativa L.) is widely grown as a forage crop due to its good quality characteristics and high adaptability. However, seed yield is generally considered to be of secondary importance and is characterized by fluctuating yields with often poor seed quality. A field experiment using five alfalfa cultivars (Equipe, Iside, Lodi, Robot, Romagnola) was carried out in 1995, 1996 and 1997 at Foggia (southern Italy) to evaluate the effects of four defoliation practices (H1: crop mown during early plant growth; H2: plant desiccation by chemical agent at the end of February; H3: crop mown at early flowering; H4: never cut) and two irrigation treatments (I: irrigation applied from April to beginning of seed filling; NI: non-irrigated control) on seed yield, seed yield components and seed quality (as determined by seed germination with and without accelerated ageing (AA)). The relationships between yield components (stems per m2, pods per stem, seeds per pod, 1000-seed weight) were determined by path-coefficient analysis. Irrigation significantly increased seed yield; on average doubling the control yield over the three seasons. However, the potential seed yield (calculated from seed yield components) was, on average, five times the actual seed yield. The two mowing treatments produced consistently higher seed yields than either desiccated or untreated swards. Cultivar differences were evident for seed yield, with Equipe having the highest value (40% higher than the mean of the other cultivars). Irrigation improved the yield primarily because it led on average a greater than four fold increase in the density of stems (the most influential yield component). By contrast, seeds per pod and 1000-seed weight increased in the absence of irrigation. Defoliation treatments had little effect on stems per m2, seeds per pod and seed weight, whereas pods per stem were reduced by desiccation. Path analyses calculated across irrigation treatments and years revealed that stems per m2 had the largest positive direct effect on alfalfa seed yield under each harvest management (path-coefficient values ≥0.89), and its indirect effects on seed yield via other traits were negligible. Seed quality, as measured by germination percentage both before and after AA, remained relatively consistent across both defoliation and irrigation treatments and cultivars, but was anomalously low in the 1997 irrigated crops. Overall, the highest seed yields were obtained under irrigated conditions when crops were mown during early growth or at early flowering. The potential seed yield of alfalfa varieties is sufficient to guarantee a profitable seed harvest. However, the harvest efficiency of the combine-harvester was low (20% of the potential seed yield); thus, more appropriate harvest techniques should be used.  相似文献   

12.
《Field Crops Research》1995,40(2):87-94
Maize (Zea mays L.) grain yield is particularly sensitive to water deficits that coincide with the tasseling-silking period, causing marked reductions in grain number. More knowledge about crop responses to water supply is required, however, to explain the causes of kernel number reductions under the mild stresses characteristic of humid regions. The objectives of this study were to: (i) quantify crop evapotranspiration, Ec, and its relationship with shoot biomass production, grain yield, and kernel number; and (ii) determine the impact on final kernel number of supplying fresh pollen to silks whose appearance is delayed by water deficits at silking. Field experiments were conducted at Balcarce (37°45′S, 130 m) during 1988/89 and 1989/90 with two sowing dates (6 weeks apart) to provide differences in evaporative demand. Plastic covers were placed on the ground of water-deficit plots to generate a 40-day period of lowered water supply bracketing silking. Control plots received rain plus additional furrow irrigation in order to keep the ratio between crop (c) and potential (Ep) Penman evapotranspiration greater than 0.9. Plant water status indicators revealed differences between treatments, but failed to reflect soil water status. Water deficit reduced plant height, maximum leaf area index, and shoot biomass. Shoot biomass accumulation was correlated with Ec, but higher water-use efficiencies (WUE) were found for the water-stress treatments. Grain yield was correlated to kernels m−2 (r = 0.88; 6 d.f.), and both grain yield and kernels m−2 were related to Ec during the treatment period, resulting in reductions of 4.7 grains m−2 and 17.7 kg ha−1 for each mm reduction in Ec. The number of kernels per ear did not improve when fresh pollen was applied to late appearing silks, suggesting that ovaries which failed to expose their silks synchronously with pollen shedding were deleteriously affected by water stress.  相似文献   

13.
《Field Crops Research》1998,59(2):121-127
Oilseed rape seedlings (Brassica napus L.) treated with uniconazole were transplanted at the five-leaf stage into specially designed experimental containers, and then exposed to waterlogging for 3 weeks. Pre-treatment of rape seedlings with uniconazole significantly increased seedling height, shoot width, number of green leaves and leaf area per plant, and consequently the shoot, root, and total dry weight after waterlogging. Following waterlogging stress, the uniconazole treated plants had a significantly improved growth including plant height, length and width of leaves, number of green leaves, leaf area per plant, and canopy width at the stem elongation stage, and plant height, stem width, and root, shoot and total dry weight at the flowering stage. At harvest, uniconazole treatment increased the number of primary and secondary branches, seeds per pod, and number of effective pods in branches and in terminal raceme after waterlogging treatment. The uniconazole-induced increase in the number of pods per plant and number of seeds per pod were the two yield components responsible for the significantly greater seed and oil yields obtained from the uniconazole plus waterlogging treated plants, over either the control or waterlogged plants. Uniconazole also reduced waterlogging-induced rise in the erucic acid content of the seeds. The modification of GA3, zeatin, ABA and ethylene levels due to pre-treatment of rape seedlings with uniconazole might have helped to delay the chlorosis and senescence induced by waterlogging. Uniconazole treatment also increased the leaf photosynthetic rates of waterlogged plants, in part, due to the changes in leaf conductance and hormone levels which ultimately affected various physiological processes.  相似文献   

14.
Intensive cultivation of rice and wheat in north-west India has resulted in air pollution from rice straw burning, soil degradation and declining groundwater resources. The retention of rice residues as a surface mulch could be beneficial for moisture conservation and yield, and for hence water productivity, in addition to reducing air pollution and loss of soil organic matter. Two field experiments were conducted in Punjab, India, to study the effects of rice straw mulch and irrigation scheduling on wheat growth, yield, water use and water productivity during 2006-2008. Mulching increased soil water content and this led to significant improvement in crop growth and yield determining attributes where water was limiting, but this only resulted in significant grain yield increase in two instances. There was no effect of irrigation treatment in the first year because of well-distributed rains. In the second year, yield decreased with decrease and delay in the number of irrigations between crown root initiation and grain filling. With soil matric potential (SMP)-based irrigation scheduling, the irrigation amount was reduced by 75 mm each year with mulch in comparison with no mulch, while maintaining grain yield. Total crop water use (ET) was not significantly affected by mulch in either year, but was significantly affected by irrigation treatment in the second year. Mulch had a positive or neutral effect on grain water productivity with respect to ET (WPET) and irrigation (WPI). Maximum WPI occurred in the treatment which received the least irrigation, but this was also the lowest yielding treatment. The current irrigation scheduling guidelines based on cumulative pan evaporation (CPE) resulted in sub-optimal irrigation (loss of yield) in one of the two years, and higher irrigation input and lower WPI of the mulched treatment in comparison with SMP-based irrigation scheduling. The results from this and other studies suggest that farmers in Punjab greatly over-irrigate wheat. Further field and modelling studies are needed to extrapolate the findings to a wider range of seasonal and site conditions, and to develop simple tools and guidelines to assist farmers to better schedule irrigation to wheat.  相似文献   

15.
The response of established perennial ryegrass swards to irrigation was compared over 2 years. The swards received 250 (N1) or 500 kg N/ha (N2) and were cut 4 times each year. Water was applied in 5 irrigation treatments according to the potential soil water deficit: the soil was partially, or fully returned to field capacity after cutting; returned to field capacity after cutting and then whenever a 25 mm deficit arose; irrigated with 25 mm water whenever a 25 mm deficit arose independently of cutting; or irrigated at minimum intervals of 14 days, provided that the deficit was then at least 50 mm. There was little effect of irrigation on yield from the first cut in late May. Frequent irrigation gave the greatest increase in total annual yield (3.1 t/ha), hut partial irrigation after cutting was most efficient in use of water and equipment, provided that drought conditions were avoided. High concentrations of N in the herbage were associated with low DM yields, hut more N (percentage N DM yield) was recovered from the irrigated than from the unirrigated swards. More N was recovered than was applied in the N1 treatment; less was recovered than was applied in N2. In the N1 treatment the nitrate concentration was <500 ppm hut it was 1000–4000 ppm in N2. There was no consistent effect of irrigation on nitrate or K concentration.  相似文献   

16.
《Field Crops Research》1987,17(1):45-53
Yield components (Yc) and their association with grain yield (GY) were studied in seventeen varieties of Triticum aestivum, T. durum and triticale grown for five years in irrigated and unirrigated environments. The varieties were categorized into four contrasting groups based on their drought susceptibility indices (S) and yield potentials (Yp). The slope (b) and intercept (a) of the linear regression between Yc and the environmental index, and S values of Yc were estimated. Their relationships with b, a and S of GY were also studied irrespective of the parameter used. Total dry matter (DM) and the number of grains per m2 (GNO) were always positively correlated with GY. GWT (1000-grain weight) was not correlated with GY.There was considerable variation among the groups in their Yc at different water-availability levels. The group of varieties having low S and moderate Yp produced more spikes per m2 (SPIKES) relative to other groups irrespective of the water availability. Simultaneously, their increased number of grains per spike (GNOSP) in drought environments relative to irrigated environments partially offset the accompanying reduction in SPIKES. The group of varieties characterized by high Yp and low S had highest yield in irrigated and moderate drought environments because they had both more SPIKES and more GNOSP. By comparison, the varietal group having high Yp and high S had higher GNOSP but lower SPIKES. Varieties which had low Yp and were susceptible to drought had the lowest SPIKES, GNOSP and DM.It was concluded that maintenance of SPIKES would provide an advantage in environments varying in soil water availability. Performance in irrigated environments would depend on the maintenance of high GNOSP also. Higher DM production would be advantageous in all environments.  相似文献   

17.
Variations in soil-water and plant-water status were examined in swards of perennial ryegrass over a period of 2 years. Unirrigatcd swards were compared with swards partially irrigated after cutting and with swards fully irrigated after cutting and then again whenever a 25 mm potential soil water deficit (SWD) arose. Two levels of N were applied to the swards (Nj= 250 kg N/ha, NT= 500 kg N/ha in each year). Frequent measurement of the water in the soil profiles beneath these swards with a neutron soil-moisture probe, enabled comparisons to be made of the actual SWD with the potential SWD on which the irrigation regimes were based. In the unirrigated swards the actual rate of water use by the swards fell below the potential rate of use at a potential SWD of approximately 50 mm. On the other hand, frequent irrigation at a potential SWD of 25 mm often failed to maintain the actual deficit within 25 mm of field capacity. Under both the unirrigated and the partially irrigated swards, greater use was made of the soil water below 30 cm depth in the N2 treatment than in the N1. The pressure-chamber technique proved particu larly suitable for measuring the variation in leaf-water potential (LWP) of grasses in the field. LWP was highest (least negative) at dawn and, provided that no dew was present on the leaves, was related to the actual SWD. There was no direct relationship between the daily minimum value of LWP and SWD, the former being determined largely by evaporative demand. However, LWP in frequently irrigated swards rarely fell below –15 atm, whereas much lower values were recorded in swards on drier soils. It is suggested that the effect of irrigation on plant-water stress may be most readily assessed from the LWP at dawn.  相似文献   

18.
《Field Crops Research》2002,74(1):81-91
Despite the economic importance of tobacco, there is limited field study on the quantitative response of growth and yield to increasing soil salinity. The effects of irrigation with saline water on yield components of field-grown tobacco (Nicotiana tabacum L.) “Burley” type plants were studied over two growing seasons. Growth, dry matter partitioning and gas exchange were measured either in rainfed or fully irrigated plants growing in a clayey–sandy–loam soil. The four fully irrigated treatments received amounts of saline waters at 0.54, 2.5, 5.0 or 10 dS m−1 electrical conductivity (ECw) equal to crop evapotranspiration. In both years, the electrical conductivity of the saturation phase (ECe) across the 0.6 m topsoil profile increased with increasing salinity of the irrigation water. Soil moisture was markedly lower in the rainfed treatment than in fully irrigated treatments. Different saline concentrations of irrigation water had virtually no effect on soil moisture. Carbon assimilation rate, stomatal conductance and water use efficiency of the saline treatments were lower than the fully irrigated plants at 0.54 dS m−1 (NW treatment) in 1996, but not in 1997. Transpiration rates were unaffected by salinity in both years. The highest yield was produced by plants irrigated with good quality water. The number of leaves per unit land area was greater for the NW plants, whereas there were no differences between the other four treatments. Salinity decreased plant dry matter and height at harvest, increased dry matter partitioning into leaves and decreased that into stems in both years. Dry matter partitioning to leaves was also greater for the rainfed plants than for the NW plants. Tobacco plants grown under field conditions showed a maximum reduction of relative yield at the highest salinity level of only 31%. The threshold values (0.56 and 0.96 dS m−1) and the ECe at which a 10% yield reduction was obtained (3.12 and 2.55 dS m−1) calculated from the linear model of response of relative yield to increasing ECe were typical of moderately sensitive crops. The ECe values at which 50% yield was reduced (13.34 and 8.91 dS m−1) were indicative of moderate tolerance to salinity.  相似文献   

19.
以2008年国家菜用（鲜食）春播大豆区域试验参试品种（系）为材料,试验分析了在辽宁种植的参试品种（系）的农艺性状、鲜荚性状、鲜荚产量及籽粒产量。结果表明,11个品种（系）从播种到鲜荚采摘生育日数为104～149d,株高为41．3～141．9cm,主茎节数为10．3～20．8个,单株荚重32．4～55．5g,标准荚数（两粒荚）178～247个／kg,标准荚长4．3～5．7cm,荚宽1．2～1．4cm,百粒鲜重49．4—72．5g,鲜荚产量10035～14769kg,拼,百粒干重21．9—34．5g,籽粒产量2386—3333kg／hm^2,有6个品种（系）为菜用大豆类型,适合在沈阳地区种植。  相似文献   

20.
《Field Crops Research》2005,93(1):85-93
Pod and seed number are the most important yield components of soybean [Glycine max (L.) Merr.]. Leaf area index (LAI), leaf area duration (LAD) and dry matter accumulation during the reproductive period strongly influence yield components. Our objectives were: to investigate if differences in yield components exist among genotypes differing in both yield and maturity; and to examine the dynamics of dry matter accumulation, LAI, and LAD during the reproductive period for the high-yielding genotypes. Sixteen soybean genotypes within three maturity groups were grown in Hailun, China in a randomized complete block design with three replications, across 2 years. Maturity groups were selected to differ by approximately 7 days in mean days to R7 (5% of pods are mature pod color). Dry matter accumulation, LAI, and LAD were measured at R2, R4, R5, and R6 stages, respectively in each year. Yield, yield components and harvest index were determined at maturity. Late maturity genotypes had higher yield than early ones. Majority of the seed yield and components were positioned in the middle and upper part of the plant. Both pod number and seed number were higher in high-yield genotypes in each group. Seed number per pod contributed to increased yield in the high rainfall year but was not related to the variation in yield of the genotypes evaluated. Significant variations were found for LAI, LAD and dry matter within each maturity group. Higher accumulation of dry matter, higher LAI and LAD during reproductive stages were found to be closely related to high-yield genotypes in each group. No relationship was found between harvest index (HI) and seed yield.  相似文献   

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