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1.
Salt sensitivity of wheat at various growth stages   总被引：14，自引：0，他引：14  
Summary The relative salt tolerance of two wheat species (Triticum aestivum L., cv. Probred and Triticum turgidum L., Durum Group, cv. Aldura) at different stages of growth was determined in a greenhouse experiment. Plants were grown in sand cultures that were irrigated four times daily with modified Hoagland's solution. Salinization with NaCl and CaCl2 (2:1 molar ratio) provided seven treatment solutions with osmotic potentials ( s ) ranging from –0.05 to –1.25 MPa (electrical conductivities of 1.4 to 28 dS/m). Salt stress was imposed for 45 days beginning at either 10, 56, or 101 days after planting. The three 45-day stages are referred to here as the vegetative, reproductive, and maturation stages although the first stage included spikelet differentiation. In a separate experiment, seedling growth was measured after 21 days of salt stress ( s = –0.05 to –0.85 MPa) initiated at 0, 7, 11, and 16 days after planting. Salt stress ( s = –0.65 MPa) delayed germination by 4 days for both wheats but full emergence occurred. Relative growth response curves of the seedlings were alike regardless of whether salt stress was imposed at planting or at the 1st, 2nd, or 3rd-leaf stage of growth. Salt stress also retarded leaf development and tillering but hastened plant maturity. Grain yields from plants stressed during either the vegetative, reproductive, or maturation stages indicated that both species became less sensitive to salinity the later plants were stressed. Grain yield was reduced 50% at s = –0.76, –1.53, and –1.58 MPa for Probred and –0.65, –1.08, and –1.34 MPa for Aldura when salinized during stages 1, 2, and 3, respectively. Salinity reduced grain yield by reducing seed number more than seed weight indicating that salt stress during stage 1 affected spikelet differentiation. Straw yield was significantly reduced by salt stress only during stage 1. Leaf mineral analyses revealed that Aldura readily accumulated Na whereas Probred did not. Both species accumulated Cl but the concentrations were much higher in Aldura. K uptake was severely inhibited by salt stress imposed during the first stage but not when imposed the second stage.  相似文献   

2.
Summary The relative salt tolerance of cowpea (Vigna unguiculata (L.) Walp. cv. California Buckeye No. 5) at different stages of growth was determined in a greenhouse. Plants were grown in sand cultures that were irrigated four times daily with modified half-strength Hoagland's solution. Salination with NaCl and CaCl2 (2:1 molar ratio) provided seven treatment solutions with osmotic potentials (s) ranging from –0.05 to –1.05 MPa (electrical conductivities of 1.4 to 28 dS/m). Salt stress was imposed for 20 days beginning at either 7, 27, or 52 days after planting. The three 20-day stages are referred to here as vegetative, flowering, and pod filling stages. Pod and seed yields from plants stressed during either the vegetative, flowering, or pod-filling stages indicated that cowpea was the most sensitive to salinity during the vegetative stage and became less sensitive the later plants were stressed. Seed yield was reduced 50% at s =–0.45, –0.76, and –0.88 MPa for plants salinized during the vegetative, flowering, and pod-filling stages, respectively. Salinity reduced seed yield by reducing seed number; it had little, if any, effect on the weight of individual seeds. Vegetative growth was significantly reduced by salt stress during all three stages but the effect was much less when stress was imposed during the last two stages than during the first stage.  相似文献   

3.
Summary In order to study the drought sensitivity of pea (Pisum sativum L. cv. Bodil) during different growth phases, a field experiment was conducted in 1985 and 1986 on coarse textured sandy soil with low water-holding capacity. Drought occurred naturally or was imposed by shelters during the vegetative, the flowering and the pod filling growth phase, respectively. Drought sensitivities were assessed as the ratio between relative yield decrease (1 – Ya/Ym) and relative evapotranspiration deficit (1 – ETa/ETm) of the individual growth phases, where Ya and ETa are the actual yield and evapotranspiration, respectively, of a drought stressed plot and Ym and ETm are the maximum yield and evapotranspiration of the fully irrigated treatment. Root growth was followed by measuring root density (L v ) in 10 cm soil layers to a depth of 50 cm. The leaf osmotic potential at full hydration ( s 100 ) was measured in the last fully developed leaf during the growing season.The available water capacity was estimated to be 42–50 mm on the basis of a plot of ETa/ETm versus soil water deficit measured by the neutron moderation method or direct measurement of the root depth. The root zone with L v >0.1 cm–2 only reached a depth of 35 cm at the end of the flowering phase and a depth of 45–50 cm at maturity. Root growth continued during the drought periods. The drought sensitivity of pea was high during the flowering phase, especially in 1986 when water stress developed rapidly, and considerably lower during the pod filling phase. The yield reduction caused by drought in the flowering phase was mainly the result of a lower number of pods per stalk. Severe drought did not occur during the vegetative phase. The leaf osmotic potential ( s 100 ) declined from c. -0.75 MPa to c. -1.30 MPa during the growing season. Osmotic adjustment was largest during drought in the early growth phases; in 1985 s 100 decreased 0.5 MPa under relatively slow drought development during the flowering phase while in 1986, when drought stress developed rapidly, s 100 only decreased 0.2 MPa. Osmotic adjustment may have caused the lower drought sensitivity in 1985 than in 1986 and mediated the continued root growth during drought.  相似文献   

4.
Summary A field trial was conducted to determine the response of rapeseed (Brassica napus cv. Marnoo) to two irrigation treatments and six nitrogen fertilizer treatments. Dry matter accumulation, leaf area development and seed yield were measured. The dry matter and seed yield response to applied nitrogen was greater under irrigated compared to rainfed conditions. Maximum seed yield (approx. 3.8 t ha–1) was obtained from the irrigated treatment receiving 100 kg N ha–1 applied at sowing. This high rate of N application at sowing led to more rapid leaf area development and higher maximum LAI compared to treatments supplied with split application of the same amount of N at sowing and rosette stages. Greater partitioning of dry matter into the leaf component and higher specific leaf areas under the higher N regime were largely responsible for this increase. Higher maximum LAI's were associated with greater numbers of pods per plant, which combined with longer leaf area duration led to higher final seed yields.  相似文献   

5.
Summary A field trial was conducted to determine the response of rapeseed (Brassica napus cv. Marnoo) to two irrigation treatments and six nitrogen fertilizer treatments. Response to nitrogen was greater with than without irrigation. Oil content was increased with irrigation but decreased under increasing nitrogen application, and was inversely related to seed nitrogen concentration. Oil yields averaged 1,168 kg ha–1 under irrigated treatments compared with 835 kg ha–1 under rainfed treatments. Maximum oil yield (approx. 1,557 kg ha–1) was obtained from the irrigated treatment fertilized with 100 kg N ha–1 applied at sowing.  相似文献   

6.
Summary The effect of irrigation on tillering and tiller mortality in varieties of wheat (Triticum aestivum and T. durum), triticale and barley was studied under field conditions. Low temperature in the early stages of growth promoted production of tillers whereas increase in temperature during extension growth phase increased tiller mortality. More than 1000 tillers m–2 were produced with five irrigations but 40% or more died. With limited water availability tiller production was reduced but so was their mortality. Grain yield in wheat and triticale was positively correlated with productive tillers and negatively correlated with the maximum number of tillers produced in wheat and barley grown under limited irrigation conditions. Varieties with a capacity to produce fewer tillers were identified. Some of them proved more stable in yield. No correlation was found between tiller number and grain yield in the frequently irrigated treatment.  相似文献   

7.
In 2006 a comprehensive sampling program was undertaken in two pre-selected peri-urban villages in Faisalabad, Pakistan to evaluate the soil and agronomic impacts of long-term (25–30 years) untreated wastewater re-use on wheat grain and straw yields and attributes of wheat straw fodder quality. Soil SAR, ESP, RSC and ECe were 63%, 37%, 31%, and 50% higher under wastewater (WW) as compared with canal water (CW) irrigated plots. Further, 2.7 and 6.65 fold increases in soil NO 3 ? + NO 2 ? - N and Olsen-P were observed in WW as compared with CW irrigated plots. However, no significant differences in grain yield, wheat straw biomass, or fodder quality attributes were observed between WW and CW irrigated plots. In addition, for both CW and WW irrigated plots wheat straw, Cd and Pb concentrations were orders of magnitude below the EC Maximum permissible levels for Pb and Cd in feed materials and thus pose no threat to the fodder-livestock food chain. Further, elevated soil N associated with WW irrigated plots has a significant (p?<?0.01) positive influence on fodder quality by increasing the N content. Factorial ANOVA with covariance indicates that effective management of the elevated soil ECe in WW irrigated plots would increase grain yield and wheat straw biomass by 853 kg ha?1 (19.5%) and 819 kg ha?1 (18.6%) respectively as compared with CW irrigated plots. In Faisalabad, if managed appropriately to address emerging salinity issues the contribution of wastewater irrigation to the achievement of MDGs 1 and 7 could be significant if adverse impacts remain as marginal as found in this study.  相似文献   

8.
Summary Empirical functions to predict the nitrogen uptake, increase in LAI and minimum leaf water potential (LWP) of cotton were incorporated into a water balance model for the Namoi Valley, N.S.W. A function was then developed to describe the lint yield of irrigated cotton as a function of water stress days at 4 stages of development, total nitrogen uptake and days of waterlogging. A water stress day was defined as predicted minimum leaf water potential less than -1.8 MPa up to 90 days after sowing and -2.4 MPa there-after; stress reduced yield by up to 40 kg lint ha–1 d–1 with greatest sensitivity at 81–140 days after sowing and when N uptake was highest. Nitrogen uptake was reduced by 0.98 kg per ha and yield reduced by 33.2 kg lint ha–1 for each day of waterlogging. The model was used to evaluate various irrigation strategies by simulating production of cotton from historical rainfall data. With a water supply from off farm storage, net returns ($ M1–1) were maximized by allocating 7 Ml ha–1 of crop. The optimum practice was not to irrigate until 60 days from sowing and until the deficit in the root zone reached 50%. When the supply of water was less than 7 Ml ha–1 there was no advantage in either delaying the start of irrigation or irrigating at a greater deficit; it was economically more rational to reduce the area shown or, if already sown, to irrigate part with 6 Ml ha–1 and leave the rest as a raingrown crop. Irrigation decisions are compromises between reducing the risk of water stress and increasing the risk of waterlogging. The simulation showed that there is no single set of practices that is always best in every season; in a number of seasons practices other than those which on average are best, give better results.  相似文献   

9.
Summary Irrigated cultivation of pecans (Carya illinoensis K.) has increased dramatically in the Southwestern USA, yet their tolerance to salinity remains largely unknown. The first part of this study was conducted to assess if stunted tree growth reported in clayey soils is related to salinity, and the second part was to evaluate changes in soil salinity and the performance of 11 year old Western trees irrigated with water of 1.1 dSm–1 and 4.3 dSm–1 for 4 years. The first study, conducted at a commercial orchard (49 ha) in the El Paso valley (TX), showed a highly significant correlation between tree trunk size and salinity of the saturation extract (ECe) with r=–0.89. Soil salinity above which trunk size decreased in excess of the standard error was 2.0 dSm–1 in ECe from 0–30 cm depth, and 3.0 dSm–1 in 0 to 60 cm depth with corresponding Na concentrations of 14 and 21 mmol l–1. Excessive accumulation of salts and Na was found only in silty clay and silty clay loam soils. The second study, conducted at a small experimental field (1 ha), indicated that irrigation with waters of 1.1 and 4.3 dSm–1 increased ECe of the top 60 cm profile from 1.5 to 2.2 and 4.2 dSm–1 and Na concentration in the saturation extract to 17 and 33 mmol l–1, respectively. The leaching fractions were estimated at 13 and 37% when irrigated with waters of 1.1 and 4.3 dSm–1, respectively. Tree growth progressively slowed in the saline plots irrigated with water of 4.3 dSm–1, and became minimal during the 4th year. The cumulative shoot length over the 4 year period was reduced by 24% and trunk diameter by 18% in the saline plots relative to nonsaline plots. Irrigation with the saline water also reduced nut yields by 32%, nut size by 15% and leaflet area by 26% on the 4 year average, indicating that pecans are only moderately tolerant to salinity. The concentration of Na, Cl and Zn in the middle leaflet pair did not differ significantly between the two treatments. Soil salinity provided a more reliable measure for assessing salinity hazard than leaf analysis. However, soil salinity was found to be highly spatially variable following a normal distribution within a soil type. This high variability needs to be recognized in soil sampling as well as managing irrigation.Contribution from Texas Agricultural Experimental Station, Texas A & M University System. This program was supported in part by a grant from the Binational Agricultural Research and Development (BARD) fund  相似文献   

10.
The ability of cotton roots to grow downwards through a partially-wetted soil (Calcic Haploxeralf) profile toward a water source located beneath them was investigated. Plants were grown in 60-cm-high soil columms (diameter 10 cm), the bottom 15 cm of which was kept wet by frequent drip irrigation, while the upper 45 cm was wetted three times per week up to 20, 40, 60, 80 or 100% of pot capacity. Pot capacity was defined as the water content which gave uniform distribution within the pot and was at a soil matric potential ( m ) of –0.01 MPa. Plants were harvested 42 and 70 days after emergence (DAE). Root length density was reduced by decreased soil moisture content. At 42 DAE, density was reduced in the soil profile down to 36 cm. The density in the middle segment of the cylinder (24–36 cm) increased at the second harvest, from 0.1 to 0.35 cm · cm–3 at 40% and from 0.2 to 0.5 cm · cm–1 at 60% of pot capacity, respectively. A significant rise in root length density was found at all moisture contents above 20% in the two deepest soil segments. It was most marked at 40% where the rise was from 0.2 to 0.8 cm · cm–3, due to the development of secondary roots at the wetted bottom of the column. When only 20% of pot capacity was maintained in the top 45 cm of the profile, almost no roots reached the wetted soil volume, and root length density was very low. Hydrotropism, namely root growth through dry soil layers toward a wet soil layer was thus not apparent. Root dry weight per unit length decreased with increasing depth in the column at all moisture levels. However, the only significant decrease was, found between the top and the second soil segments and was due to thicker primary roots in the top segment. There was no clear relationship between length and dry weight of roots. Total plant dry weight and transpiration were reduced significantly only at 20% of pot capacity. Dry matter production by roots was less severely inhibited than that by shoots, under decreased moisture content in the soil profile. Leaf water potential decreased when the soil moisture content of the top 45 cm of the profile was reduced below 60% of pot capacity. It was concluded that even at soil moisture content equivalent to a m of 0.1 MPa, the rate of root growth was sufficient to reach a wetted soil layer at the bottom of the soil column, where the plant roots then proliferated. This implies that as long as the soil above the subsurface dripper is not very dry there is no real need for early surface irrigation.  相似文献   

11.
Summary An irrigation experiment was conducted on wheat in the northern Negev, Israel. The growing season rainfall was 198 mm; six irrigation treatments, ranging from 0 to 320 mm were applied at different stages of growth. The grain yields ranged from 1.20 to 5.84 t/ha. Stomatal aperture was evaluated by leaf permeability, as measured with a fast-reading viscous flow porometer. Other indices of soil-plant water status measured were: soil moisture with a neutron probe; leaf water potential with a pressure chamber; CO2 uptake with a 14CO2-pulse apparatus; and leaf water saturation deficit.For the penultimate and flag leaves, midday leaf permeability was highly correlated with the soil moisture in the upper 60-cm layer. CO2-uptake, however, remained constantly high (ca. 0.8 mg m–2s–1 = 29 mg dm–2h–1) throughout a wide range of leaf permeability, from 10 down to 2 porometer units (p. u.); below this value, it decreased linearly with leaf permeability. Therefore, the value of 2 p. u. was tentatively regarded as a critical value for judging the critical values of the other indices studied; these were estimated to be: leaf water potential, –1.57 MPa = –15.7 bars; leaf saturation deficit, 18,8% and soilmoisture, 12.6% representing a 83% depletion of the available moisture in the Gilat soil. The grain yield was highly negatively correlated with the duration of period when the soil moisture was below these critical values. The use of the porometer method for evaluating water stress is discussed.  相似文献   

12.
Midday leaf water potential (Ψmd) was monitored for 3 years at a commercial vineyard (cv. Pinot Noir) under four irrigation strategies. Three treatments were established based on irrigating vines with 4–6 mm/day, when daily measured Ψmd was more negative than the pre-defined threshold. After the first experimental year, thresholds were adjusted for each treatment as: (1) Control (C), irrigated when Ψmd was less than −0.6 MPa at the beginning of the season and gradually fell to −0.8 MPa at about mid-June, after which the threshold was maintained at −0.8 MPa until harvest. (2) Control–Deficit (CD), irrigated as C from bud-break to mid-June (around the middle of Stage II of fruit growth), and from then until harvest when Ψmd decreased below −1.2 MPa. (3) Deficit–Deficit (DD), irrigated when Ψmd was less than −1.0 from bud break to mid-May (about the middle of fruit growth Stage I), and after that time the Ψmd threshold became −1.2 MPa until harvest. A fourth treatment was applied following a soil water budget approach (WB). All treatments were replicated five times but irrigation in the Ψmd-based treatments were independently applied to each of the replicate plots, whereas irrigation for WB was applied equally to all replications. The more site-specific information obtained from Ψmd thresholds in C provided substantial advantages for yield homogeneity and repeatability of results with respect to WB, thus demonstrating the method’s greater ability to account for spatial variability. Average applied water for the 3 years in C, CD, and DD was 374, 250, and 178 mm, respectively, while the yields were 11.8, 9.2, and 6.1 kg/vine, respectively. The CD treatment produced better juice quality than C, and was superior in other quality parameters to both C and DD. However, over the study period, an important carryover effect was observed in the yields and the grape size of CD, which tended to diminish from year to year relative to C.  相似文献   

13.
Chloride mass balance (steady state or transient state) models are used extensively in Vertisols of Queensland and New South Wales (NSW) in Australia to estimate deep drainage. The aim of this study was to compare deep drainage estimated assuming steady state and transient state conditions with chloride mass balance models in irrigated cotton (Gossypium hirsutum L.)-based farming systems in the lower Namoi Valley of North Western NSW. Drainage was estimated at seven sites, and treatments included rotation crops such as wheat (21–62 mm/year) (Triticum aestivum), sorghum (12–47 mm/year) (Sorghum bicolor) and dolichos (12–21 mm/year) (Lablab purpureus), minimum tillage (62–83 mm/year), where cotton was sown into standing wheat stubble, and conventional tillage where stubble was incorporated (35–78 mm/year). Soil water content was measured with a neutron moisture meter in the 0.2–1.2 m depth. Soil was sampled before sowing and after harvest to a depth of 1.2 m along diagonal transects. The soil chloride concentration was determined by titration with AgNO3. Irrigation water was also analysed for chloride. The deep drainage estimates were compared using regression analysis and students paired t-test. In addition, a paired t-test of the soil chloride concentration before sowing and after harvest was used to determine if the soil chloride flux was either in a steady state or transient state. In 9 out of the 13 data sets (69%), drainage estimated with the models agreed with changes between pre- and post-season soil chloride concentrations. Under frequently irrigated summer crops such as cotton and sorghum and in better structured soils chloride flux reached steady state conditions whereas under partially-irrigated crops or where soil structure was poorer, the chloride flux deviated markedly from steady-state conditions. The latter observation may be due to preferential flow via deep cracks in infrequently irrigated soil. Deep cracking would be due to the more intense shrinking and swelling in partially irrigated soil in comparison with frequently-irrigated crops. Comparison of estimated deep drainage with pre- and post-season soil chloride concentrations showed that the steady state mass balance model best estimated deep drainage under cotton crops which were irrigated more frequently or wheat crops which had better soil structure.
T. B. WeaverEmail: Phone: +61-2-67991570Fax: +61-2-67991503
  相似文献   

14.
Summary An irrigation experiment with water of different salinities (2.8, 7.6 and 12.7 mol Cl m–3) was carried out from 1982 to 1988 in a mature Shamouti orange grove in the coastal plain of Israel. Seasonal accumulation of salts in the soil solution of the root zone (EC of more than 4.0 dS m–1 at the end of the irrigation season) was almost totally leached during the winter. The average annual rainfall of 550 mm reduced EC values below 1.0 dS m–1. Tree growth, as measured by the increase in cross sectional area of main branches, was retarded by saline irrigation water (123, 107 and 99 cm2 growth per tree during six years for the 2.8, 7.6 and 12.7 mol Cl m–3 treatments, respectively). Potassium fertilization (360 kg K2O ha–1) increased yield at all salinity levels during the last three years of the experiment, mainly by increasing fruit size. Saline irrigation water slightly increased sucrose and C1 concentrations in the fruit juice. Salinity decreased transpiration, increased soil water potential before irrigation and decreased leaf water potential. However, the changes in leaf water potential were small. Leaf Cl and Na concentrations increased gradually during the experimental period, but did not reach toxic levels up to the end of the experiment (4.4 g Cl kg–1 dry matter in the high salt treatment vs. 1.7 in the control). Relatively more leaf shedding occurred in the salinized trees as compared to the control. The sour orange root-stock apparently provided an effective barrier to NaCl uptake; therefore, the main effect of salinity was probably osmotic in nature. No interactions were found between N or K fertilization and salinity. Additional N fertilization (160 kg N ha–1 over and above the 200 kg in the control) did not reduce Cl absorption nor did it affect yield or fruit quality. Additional K had no effect on Na absorption but yield and fruit size were increased at all salinity levels. No significant differences were obtained between partial and complete soil surface wetting (30% and 90% of the total soil area resp.) with the same amounts of irrigation water. The effect of salinity on yield over the six years of the experiment was relatively small and occurred only after some years. But, in the last three years salinity significantly reduced average yields to 74.6, 67.1, and 64.2 Mg ha–1 for the three levels of salinity, respectively.These results suggest that saline waters of up to 13 mol Cl m–3 primarily influence the tree water uptake and growth response of Shamouti orange trees, whereas yield was only slightly reduced during six years.  相似文献   

15.
In sub-mountain tract of Punjab state of India, maize (Zea mays, L.) and wheat (Triticum aestivum L.) crops are grown as rainfed having low crop and water productivity. To enhance that, proper understanding of the factors (soil type, climate, management practices and their interactions) affecting it is a pre-requisite. The present study aims to assess the effects of tillage, date of sowing, and irrigation practices on the rainfed maize–wheat cropping system involving combined approach of field study and simulation. Field experiments comprising 18 treatments (three dates of sowing as main, three tillage systems as subplot and two irrigation regimes as the sub-subplot) were conducted for two years (2004–2006) and simulations were made for 15 years using CropSyst model. Field and simulated results showed that grain yields of maize and wheat crops were more in early July planted maize and early November planted wheat on silt loam soil. Different statistical parameters (root mean square error, coefficient of residual mass, model efficiency, coefficient of correlation and paired t-test) indicated that CropSyst model did fair job to simulate biomass production and grain yield for maize–wheat cropping system under varying soil texture, date of planting and irrigation regimes.  相似文献   

16.
Summary Because of the strategic and industrial importance of natural rubber, there has been renewed interest in cultivating guayule (Parthenium argentatum). This study was performed for assessing feasibility of guayule cultivation with waters high in dissolved salts. The test materials included six USDA selections (11591, 11605, 11619, 11646, 12229 and N576), one cultivar (593) and one hybrid (4265XF). Seedlings were grown for l0 weeks in a greenhouse and transplanted in the spring and in the summer into lysimeters (unit surface dimension of 6 x 7 m) containing loamy sand or silt loam. They were grown with simulated irrigation waters having four levels of salinity (0.8, 2.4, 4.6 and 7.2 dSm–1 with SAR < 13) and an additional water containing 5 mmol L–1 of Mg at 2.4 dSm–1. In the spring planting, over 90% of the transplants survived when furrow irrigated weekly with waters of 4.6 dSm–1 or less. However, transplant growth for the first several months was reduced by half at irrigation water salinity of 4.6 dSm–1. In the summer planting, several fold increases in mortality and growth reduction occurred. Dry top Shrub yields after the two growing seasons following the spring planting averaged 10 Mg ha–1 at 0.8 dSm–1 and declined on the average 15 and 51 % when irrigated with waters of 4.6 and 7.2 dSm–1 respectively. The amount of water used to produce one ton of dry shrub was 1,600 m3 with waters of 0.8 and 4.6 dSm–1, and 1,900 m3 with water of 7.2 dSm–1. The contents of rubber in the shrubs averaged 61 g kg–1 at 0.8 dSm–1 and increased to 70 g kg–1 at 7.2 dSm–1. whereas resin contents were not affected by the salt treatments. Resulting rubber yields were reduced on the average by 8.5 and 44% at 4.6 and 7.2 dSm–1. respectively, because of the reduction in shrub yields. Selection N576 produced the largest rubber yields with the highest rubber content at all levels of salinity. Increasing Mg concentrations from 0.5 to 5 mmol L–1 in the irrigation waters reduced neither yields nor transplant survival. Yield reductions observed here appeared to be related to Na, but not Mg.Contribution from Texas Agricultural Experiment Station. Supported in part by a grant from the Latex Commission, USDA and by the US-Israel Binational Agricultural Research and Development (BARD) fund  相似文献   

17.
Summary Water deficit (water stress — WS) and excess salt (salt stress — SS) evoke similar plant responses, yet clear differences have been observed. The effect of the two forms of stress applied consecutively to cotton (Gossypium hirsutum) and pepper (Capsicum annuum) was studied in a growth chamber (29/20°C day/night temperature, 50% RH, 12-h photoperiod) in 2.5-liter containers packed with a silt loam soil.Leaf water potential () under increasing WS [soil water potential decrease from –0.16 to –1.10 MPa] of transpiring cotton and pepper plants declined to lower levels than under equivalent SS. The decline of leaf solute potential 0 on the other hand, was less under WS than under SS, resulting in reduced turgor potential ( p ), in contrast with turgor maintenance under SS. Predawn turgor potential of WS plants was maintained at all levels of soil water potential. Transpiration, CO2 assimilation and light period leaf extension rate were higher under low soil water potential produced by salinity than an equivalent value produced by water deficit.The more severe effect of WS was attributed to incomplete osmotic adjustment — the reduction in solute potential did not keep pace with the reduction in leaf water potential, and to increased root interface resistance in the dry soil.The leaf sap of cotton under WS had a higher proportion of sugars (65%) than electrolytes, compared to SS. When WS was converted to SS and plant solute potential decreased, electrolytes were taken up at the expense of a reduction in the sugar concentration. Water stress and salt stress may have an additive effect in depressing growth. But at equivalent levels, the relative magnitude of the effect of low soil matric potential (WS) on plant growth was twice as great as that of low soil solute potential (SS).  相似文献   

18.
The DSSAT-CSM-CERES-Wheat V4.0 model was calibrated for yield and irrigation scheduling of wheat with 2004–2005 data and validated with 13 independent data sets from experiments conducted during 2002–2006 at the Punjab Agricultural University (PAU) farm, Ludhiana, and in a farmer's field near PAU at Phillaur, Punjab, India. Subsequently, the validated model was used to estimate long-term mean and variability of potential yield (Yp), drainage, runoff, evapo-transpiration (ET), crop water productivity (CWP), and irrigation water productivity (IWP) of wheat cv. PBW343 using 36 years (1970–1971 to 2005–2006) of historical weather data from Ludhiana. Seven sowing dates in fortnightly intervals, ranging from early October to early January, and three irrigation scheduling methods [soil water deficit (SWD)-based, growth stage-based, and ET-based] were evaluated. For the SWD-based scheduling, irrigation management depth was set to 75 cm with irrigation scheduled when SWD reached 50% to replace 100% of the deficit. For growth stage-based scheduling, irrigation was applied either only once at one of the key growth stages [crown root initiation (CRI), booting, flowering, and grain filling], twice (two stages in various combinations), thrice (three stages in various combinations), or four times (all four stages). For ET-driven irrigation, irrigations were scheduled based on cumulative net ETo (ETo-rain) since the previous irrigation, for a range of net ETo (25, 75, 125, 150, and 175 mm). Five main irrigation schedules (SWD-based, ET-driven with irrigation applied after accumulation of either 75 or 125 mm of ETo, i.e., ET75 or ET125, and growth stage-based with irrigation applied at CRI plus booting, or at CRI plus booting plus flowering stage) were chosen for detailed analysis of yield, water balance, and CWP and IWP. Nitrogen was non-limiting in all the simulations.Mean Yp across 36 years ranged from 5.2 t ha−1 (10 October sowing) to 6.4 t ha−1 (10 November sowing), with yield variations due to seasonal weather greater than variations across sowing dates. Yields under different irrigation scheduling, CWP and IWP were highest for 10 November sowing. Yields and CWP were higher for SWD and ET75-based irrigations on both soils, but IWP was higher for ET75-based irrigation on sandy loam and for ET150-based irrigation on loam. Simulation results suggest that yields, CWP, and IWP of PBW343 would be highest for sowing between late October and mid-November in the Indian Punjab. It is recommended that sowing be done within this planting period and that irrigation be applied based on the atmospheric demand and soil water status and not on the growth stage. Despite the potential limitations recognised with simulation results, we can conclude that DSSAT-CSM-CERES-Wheat V4.0 is a useful decision support system to help farmers to optimally schedule and manage irrigation in wheat grown in coarse-textured soils under declining groundwater table situations of the Indian Punjab. Further, the validated model and the simulation results can also be extrapolated to other areas with similar climatic and soil environments in Asia where crop, soil, weather, and management data are available.  相似文献   

19.
Summary Rapid drying of surface layers of coarse-textured soils early in the growth season increases soil strength and restricts root growth. This constraint on root growth may be countered by deep tillage and/or early irrigation. We investigated tillage and irrigation effects on root growth, water use, dry matter and grain yield of wheat on loamy sand and sandy loam soils for three years. Treatments included all combinations of two tillage systems i) conventional tillage (CT) — stirring the soil to 10 cm depth, ii) deep tillage (DT) — subsoiling with a single-tine chisel down to 35–40 cm, 40 cm apart followed by CT; and four irrigation regimes, i) I0 — no post-seeding irrigation, ii) I1 — 50 mm irrigation 30 days after seeding (DAS), iii) I2 — 50 mm irrigation 30 DAS and subsequent irrigations of 75 mm each when net evaporation from USWB class A open pan (PAN-E) since previous irrigation accumulated to 82 mm, and iv) I3 — same as in I2 but irrigation applied when PAN-E accumulated to 62 mm. The crop of wheat (Triticum aestivum L. HD 2329) was fertilized with 20kg P, 10kg K and 5kg Zn ha–1 at seeding. The rate of nitrogen fertilization was 60 kg ha–1 in the unirrigated and 120 kg ha–1 in the irrigated treatments. Tillage decreased soil strength and so did the early post-seeding irrigation. Both deep tillage and early irrigation shortened the time needed for the root system to reach a specified depth. Subsequent wetting through rain/irrigation reduced the rate of root penetration down the profile and also negated deep tillage effects on rooting depth. However, tillage/irrigation increased root length density in the rooted profile even in a wet year. Better rooting resulted in greater profile water depletion, more favourable plant water status and higher dry matter and grain yields. In a dry year, the wheat in the DT plots used 46 mm more water, remained 3.3 °C cooler at grain-fill and yielded 68% more grain than in CT when unirrigated and grown in the loamy sand. Early irrigation also increased profile water depletion, more so in CT than DT. Averaged over three years, grain yield in DT was 12 and 9% higher than in CT on loamy sand and sandy loam, respectively. Benefits of DT decreased with increase in rainfall and irrigation. Irrigation significantly increased grain yield on both soils, but the response was greatly influenced by soil type, tillage system and year. The study shows that soil related constraints on root growth may be alleviated through deep tillage and/or early irrigation.  相似文献   

20.
The physiological behavior and yield response of maize under irrigation with saline water was studied in the laboratory and in the field. In the laboratory, the germination rate decreased only when the electrical conductivity (EC) of the substrate solution was above 17 dS/m. The osmotic potential of germinating maize seedlings decreased in proportion to the decrease in osmotic potential of the substrate.In the field, two maize cultivars (a field maize and a sweet maize) were irrigated alternately with saline (11 days from sowing), fresh (21 days from emergence), and saline (from day 33 to harvest) water and compared with maize irrigated with saline water continuously throughout the season. Four levels of irrigation water salinity were used (ECi = 1.2, 4.5, 7.0 and 10.5 dS/m).In the field no osmotic adjustment by the leaf sheaths of plants in response to salinity was observed. The osmotic potential of corn leaf sheaths (π) decreased with ontogeny in all treatments. The midday leaf water potential (ψL) in maize irrigated with 10.5 dS/m water was 0.75 MPa lower than in plants irrigated with 1.2 dS/m water.In the continuous treatment grain yield was reduced significantly with each increase in salt concentration, and the relationship between relative yield (y) and ECi could be expressed as y = 100?8.7 (ECi-0.84). With alternating irrigation and 7.0 dS/m treatment the grain yield was the same as in the low EC treatment (6.98 kg/m2).  相似文献   

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