Moisture stress in navy beans

Summary The effect of plant water stress imposed at all combinations of the three main phenological stages (preflower, flowering and pod development) on the yield and growth of Navy beans was studied in field experiments at the Inglewood irrigation area of Queensland during the summers of 1971 and 1972. In 1971, a short, mild growing season with early frosts, yields varied with treatment, from 0.55 to 1.52 t ha^–1, in 1972 a hotter growing season especially during the preflower stage but one of normal duration, yields varied from 1.12 to 2.27 t ha^–1. Moisture stress imposed in the preflower and flowering stages in 1971 reduced yields by 28% and 24% respectively. In 1972 moisture stress during the preflower stage reduced yield by 37% only if irrigation was also withheld during the flowering stage. Moisture stress imposed during the flowering stage in 1972 reduced yields by 40%. Evaluation of the effects of moisture stress during the pod development stage was not possible due to early frosts in 1971 and rainfall in 1972. Yields were almost equally highly correlated with leaf area index (r=0.82) and leaf area duration (r=0.84). Crop growth rate was similarly correlated with leaf area index (r=0.85).     

苗期不同土壤水分状况的秋黄瓜生理反应

对苗期不同土壤水分状况下秋黄瓜的生理反应和前期产量进行了研究。结果表明 ,苗期不同土壤水分状况显著影响了秋黄瓜的生长动态。土壤含水量为 60 %～ 75 %田间持水量 (θF)的植株叶片蒸腾和光合速率均居于较高水平 ,前期产量最高 ;5 0 %～ 60 % (θF)的植株与前者差异不显著 ,但均显著高于 75 %～ 85 % (θF)和 85 %～ 95 % (θF)的处理 ,其离体叶片在 1 .5～ 2 .0 h之间的失水速率最低。 75 %～ 85 % (θF)植株生长迅速 ,前期产量较低 ;85 %～ 95 % (θF)植株生长受限。     

Effects of tillage and fallow period management on soil physical behaviour and maize development

Effects of two tillage treatments and two fallow period managements under continuous maize cropping on soil temperature, soil water dynamics and maize development were evaluated over a 4-year period (2005–2008). Tillage treatments were conventional tillage with mouldboard ploughing and conservation tillage with disk harrowing. The fallow period managements were bare soil or soil sown with a cover crop after maize harvest. For each year, topsoil temperature (0–20 cm-depth) was lower under conservation tillage systems at sowing, from 0.8 to 2.8 °C. This difference persisted several weeks after sowing, and disappeared afterwards. Under conservation tillage, higher soil water content was generally measured at sowing and during the growing season strong fluctuations were observed at 40 cm-depth. Under conventional tillage, soil water content varied mainly in the tilled layer (20 cm-depth). Tillage and fallow period management affected water flow rate at 40 cm-depth. During the maize growing season, the lowest drainage volumes were measured in 2006 and 2008 under conservation tillage in cover cropped plots. No effect of fallow period management on maize development and yield was observed but significantly higher yields were measured under conservation tillage in 2005 and 2007. From this 4-year experiment under continuous maize cropping, using cover crop and reducing tillage intensity enhanced water use efficiency while maintaining or increasing maize yields.     

DRAINMOD-S: Water management model for irrigated arid lands,crop yield and applications

The primary objective of an agriculture water management system is to provide crop needs to sustain high yields. Another objective of equal or greater importance in some regions is to reduce agriculture impacts on surface and groundwater quality. Kandil et al. (1992) modified the water management model DRAINMOD to predict soil salinity as affected by irrigation water quality and drainage system design. The objectives of this study are to incorporate an algorithm to quantify the effects of stresses due to soil salinity on crop yields and to demonstrate the applications of the model. DRAINMOD-S, is capable of predicting the long-term effects of different irrigation and drainage practices on crop yields. The overall crop function in the model includes the effects of stresses caused by excessive soil water conditions (waterlogging), soil water-deficits, salinity, and planting delays. Three irrigation strategies and six drain spacings were considered for all crops. In the first irrigation strategy, the irrigation amounts were equal to evapotranspiration requirements by the crops, with the addition of a 10 cm depth of water for leaching applied during each growing season. In the second strategy, the leaching depth (10 cm) was applied before the growing season. In the third strategy, a leaching depth of 15 cm was applied before the growing season for each crop. Another strategy (4th) with more leaching was considered for bean which is the crop most sensitive to salinity. In the fourth strategy, 14 days intervals were used instead of 7 and leaching irrigations were applied: 15 cm before the growing season and 10 cm at the middle of the growing season for bean. The objective function for these simulations was crop yield. Soil water conditions and soil salinity were continuously simulated for a crop rotation of bean, cotton, maize, soybean, and wheat over a 19 years period. Yields of individual crops were predicted for each growing season. Results showed that the third irrigation strategy resulted in the highest yields for cotton, maize, soybean and wheat. Highest yields for bean were obtained by the fourth irrigation strategy. Results are also presented on the effects of drain depth and spacing on yields. DRAINMOD-S is written in Fortran and requires a PC with math-coprocessor. It was concluded that DRAINMOD-S is a useful tool for design and evaluation of irrigation and drainage systems in irrigated arid lands.     

Tensiometer-based irrigation scheduling in perennial strawberry cultivation

Tensiometers are ideal for soil moisture monitoring in strawberry cultivation because they operate effectively at less than −1,000 hPa soil water tension, which includes the soil moisture range for strawberries. For this study, four different drip irrigation thresholds, at −150, −300, −600 hPa, and, depending on the development stage of the plants, −300 or −600 hPa, were applied in a trial carried out in southwest Finland in 2001–2003 with June-bearing cultivar ‘Bounty’. Higher soil moisture increased yield and fruit soluble solids content, but decreased fruit firmness. In healthy plants, no remarkable soil moisture effects on plant growth were observed, but in the years 2002–2003 it was observed that increased soil moisture in the previous growing season and the subsequent winter injuries decreased the following year’s growth. Water consumption of plants varied considerably depending on growth stage, yield potential and environmental factors. The volumes of irrigation water ranged from 5 to 22 l/plant per growing season.     

Deficit irrigation in maize for reducing agricultural water use in a Mediterranean environment

Research on crop response to deficit irrigation is important to reduce agricultural water use in areas where water is a limited resource. Two field experiments were conducted on a loam soil in northeast Spain to characterize the response of maize (Zea mays L.) to deficit irrigation under surface irrigation. The growing season was divided into three phases: vegetative, flowering and grain filling. The irrigation treatments consisted of all possible combinations of full irrigation or limited irrigation in the three phases. Limited irrigation was applied by increasing the interval between irrigations. Soil water status, crop growth, above-ground biomass, yield and its components were measured. Results showed that flowering was the most sensitive stage to water deficit, with reductions in biomass, yield and harvest index. Average grain yield of treatments with deficit irrigation around flowering (691 g m⁻²) was significantly lower than that of the well-irrigated treatments (1069 g m⁽²). Yield reduction was mainly due to a lower number of grains per square metre. Deficit irrigation or higher interval between irrigations during the grain filling phase did not significantly affect crop growth and yield. It was possible to maintain relatively high yields in maize if small water deficits caused by increasing the interval between irrigations were limited to periods other than the flowering stage. Irrigation water use efficiency (IWUE) was higher in treatments fully irrigated around flowering.     

Cotton growth and production under drip-irrigation restricted soil wetting

Summary Control of optimal soil water status for high productivity of cotton can be achieved more easily when the volume of the root system is restricted than with an extended root system. The restricted root system was obtained by planting on a pre-dried soil profile and by irrigation with a drip irrigation system applying small quantities of water at high frequencies. The effects of plant population, row and drip lateral densities and the amount of water per application, on soil water distribution and on cotton growth and productivity under these conditions were determined during 3 years of field trials. Cotton (Gossypium hirsutum L. cv. Acala SJ-2) was grown in a loess-brown loam soil in the northern Negev of Israel. The crop was planted on a dry soil profile between the end of May and early June and harvested during October and early November. There was no rainfall during the irrigation season. Water moved to a greater distance vertically than horizontally from the emitter, but there was no movement of water below a depth of 50 cm unless large quantities of water were applied. Maximal lint production was obtained within a narrow range of irrigation water quantities. Quantities below this range reduced production due to water stress, while quantities above this range enhanced vegetative growth and plant height and reduced lint formation. It was concluded that an optimal moisture regime can be obtained more easily by restricting the size of the root zone, but that over-irrigation may easily occur under such conditions. An increase in population over 10 plants/m2 resulted in enhanced vegetative growth associated with a reduction in lint yield with all irrigation regimes. At the optimal plant population and with maximum quantities of water applied, higher lint production and higher rates of water withdrawal were obtained at a row spacing of 50 cm as compared with 100 cm. When sub-optimal quantities of water were applied lint production was less reduced at row spacing of 100 cm. A row-to-lateral ratio of 2, and location of the laterals between alternate rows led to a greater vertical gradient in soil water content as compared with a row-to-lateral ratio of 1. Lint production was increased and vegetative growth was decreased at a row-to-lateral ratio of 2, at both row spacings of 50 and 100 cm.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel, No. 1781 E, 1986 Series     

金丝小枣蒸散和作物系数变化规律研究

采用Probe12植物茎液流计和小型蒸发器分别测定了金丝小枣生长期间的日蒸腾和棵间蒸发。蒸腾存在日变化和季节性变化,果实膨大期蒸腾的日变化呈双峰曲线,萌芽展叶期、开花坐果期、果实成熟期和落叶期的日变化呈单峰曲线;萌芽展叶期、开花坐果期、果实膨大期、果实成熟期和落叶期的蒸腾量分别占生长季总耗水量的12.2%、16.5%、48.1%、13.2%、10.1%,金丝小枣生育期总蒸腾量346.8 mm,棵间蒸发231.7 mm,总蒸散578.5mm;棵间蒸发占总蒸散量的40.1%。枣树的作物系数随生育期变化从前期的0.27,到中期0.92,后期0.71,作物系数与冠层覆盖度呈显著正相关关系,决定系数为R2=0.758 6(P<0.01)。     

Water use — Yield relations for cowpea and maize

Three cowpea varieties and one maize variety were subjected to varying irrigation treatments, ranging from water deficits to over-irrigation, on a silty loam soil classified as an Alfisol at Ile-Ife, Nigeria. There was a strong curvilinear relation between cowpea yield and evapotranspiration (R² = 0.86 for dry matter yield and R² = 0.87 for dry seed yield). The values of the correlation coefficient dropped to 0.62 and 0.66 for dry matter and seed yields, respectively, when a linear relation was used. When data for over-irrigated fields were omitted from the calculation, a linear relationship yielded R² values close to unity (R² = 0.99). Similar results were obtained on maize dry matter and grain yields in relation to evaporation.     

Cotton root growth as affected by changes in soil water distribution and their impact on plant tolerance to drought

The capability of mature cotton plants (Gossypium hirsutum L.) to adjust to progressive drying of their root zone by promoting root growth to adjacent wetted zones, and the implications of this process on irrigation design were investigated. Field grown plants that developed shallow root systems in response to a drip irrigation management of daily, surface soil wettings were exposed 85 days after emergence (DAE), while in the flowering stage, to a sudden change in water distribution in the form of deep soil wetting (DSW) followed by termination of irrigation. The shallow rooted plants (SRP) failed to respond to further surface soil wetting and the progressive drying of the profile by rapid root growth to the deeper-wetted zones; consequently, the SRP suffered from water deficiency for at least two weeks, evidenced by a gradual decrease in their leaf water potential (L_w). Potted plants responded similarly. Daily irrigations of the pot surface with water amounts similar to those lost by evapotranspiration led to the development of a system in which most of the roots and available water became concentrated at the pot's upper section. A transition to irrigation from the bottom of the pot led to a reversed soil-water content gradient and failed to promote rapid root spreading to the deeper-wetted layers, in spite of the accelerated drying of the upper zone. The slow deepening of the root system was accompanied by water-stress symptoms as indicated by a considerable reduction in dry matter production. The root shoot ratio in these plants was not much greater than in non-stressed plants in which the surface wetting was continued. This indicated that preferential root growth relative to the shoot did not occur in response to the progressive drying of the shallow root zone. Rewetting of the root zone after a long period of soil water deficiency failed to promote rapid recovery of the root system in the form of root regrowth in this zone. It was concluded that the capability of mature cotton plant roots to adjust their growth to large changes in water distribution in the soil, is slow and that this should be taken into account when determining an irrigation regime in which the depth at which water is applied is changed during the growing season.Contribution from the Agricultural Research Organization, Volcani Center, Bet Dagan, Israel; No. 343-E, 1992 series     

Soil water recharge in a semi-arid temperate climate of the Central U.S. Great Plains

The amount of soil water at the beginning of the growing season has a large impact on crop yields in rainfed agriculture, especially in semi-arid regions and in years with below-average rainfall in more humid climates. Robust algorithms are needed to estimate soil water storage before planting to aid crop management decisions. The main objectives of this paper are to investigate soil water recharge during the non-growing season (October 20 to May 1) in a semi-arid, temperate ecosystem in south-central Nebraska (USA) and to evaluate empirical models to estimate soil water content at the beginning of the summer-crop growing season. A database of soil water content measurements collected over 5 years at nine locations in south-central Nebraska was used to estimate available water-holding limits in the soil profile and to determine the change in available soil water during the non-growing season. Regression analysis was performed to analyze the relationship among soil water recharge, residual soil water (i.e., soil water content at the end of the previous growing season), total precipitation, and available water-holding capacity (AWHC) in the root zone to 1.5 m. Precipitation storage efficiency (PSE) was calculated as the quotient of soil water recharge and total non-growing season precipitation. Predictive models to estimate soil water content at the beginning of summer-crop growing season were derived from these analyses. A large portion of the variation in soil water recharge was explained by residual soil water and precipitation. PSE averaged 28% across site-years; low PSE values were associated with high residual soil water and/or low AWHC. Two predictive models (linear and linear-plateau) that used residual soil water, total precipitation, and AWHC as independent variables explained 75-80% of the variation in the measured soil water content at the beginning of the summer-crop growing season. These empirical models represent a new tool to estimate soil water content by planting date of summer crops. Site-management conditions such as residue amount and its architecture, tillage system, soil texture, and terrain slope are not currently accounted for in these models and would likely improve predictive capacity.     

The relative sensitivity to plant water stress during the reproductive phase of upland cotton (Gossypium hirsutum L.)

Summary The relative sensitivity of the cotton plant to water stress throughout the growing season was determined to identify when irrigation will have the greatest beneficial effect. Daily plant water stress for 72 different data sets of water applications was correlated to corresponding yield criteria. The magnitude of significant correlation was interpreted as the degree of sensitivity. Plant water stress during square formation and early flowering resulted in fewer bolls to reach maturity, but this detrimental effect was cancelled by the development of bigger bolls due to greater lint growth. This resulted in better seedcotton and lint yields. Flower and boll senescence which resulted from water stress during flowering peak, however, inhibited seedcotton and lint yields. The most pronounced inhibiting effect stress had on yields, was during boll development well after the end of effective flowering, when it inhibited boll development. Stress during ripening of the bolls increased lint and boll development and consequently enhanced yields. When limited quantities of water is available, preference should be given to irrigation during boll development, then by irrigation when the first flowers appear, followed by irrigation during peak flowering. Water should be withheld from opening of the first bolls.     

The effect of polyacrylamide on runoff,erosion, and cotton yield from fields irrigated with moving sprinkler systems

Summary Irrigation with self-propelled moving sprinkler irrigation system (MSIS) enhances seal formation at the soil surface and results in large amounts of runoff and erosion which are aggravated by the MSIS high water application rate and reflected in lower yields. The effect of polyacrylamide (PAM) application (at the equivalent rate of 20 kg ha^-1), prior to the irrigation season, on runoff and erosion from bare soil and soil covered with a crop, as well as on cotton yield was studied in a clay loam vertisol (Typic Chromoxert) and a silt loam loess (Calcic Haploxeralf). A center pivot and a lateral MSIS were used in the vertisol and loess, respectively. Vegetative growth of cotton plants in the vertisol was inversely related to water application intensity, which in turn affects runoff. PAM significantly reduced runoff in both the bare and crop-covered soils. The runoff level from the PAM treatments was 50–70% of that of the control. PAM also reduced erosion especially in the vertisol soil. However, the amount of eroded material carried by a unit runoff was similar in both treatments for both soils, indicating that PAM influences erosion by reducing runoff levels. A trend whereby PAM increased yield of cotton (Gossypium hirsutum L., cv. Pima S5) compared with the control was observed. Our results suggest that, under irrigation with a MSIS, reducing runoff is essential for obtaining higher yields. PAM is suggested as an effective tool to attain this target.Contribution from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No. 2866-E, 1989 series     

Evaluation of post-rainy season crops with residual soil moisture and different tillage methods in rice fallow of eastern India

In eastern India, farmers grow rice during rainy season (June-September) and land remains fallow after rice harvest in the post-rainy season (November-May) due to lack of sufficient rainfall or irrigation facilities. But in lowland areas of eastern India, sufficient carry-over residual soil moistures are available in rice fallow in the post-rainy season (November-March), which can be utilized for growing second crops in the region. During the post-rainy season when irrigation facilities are not available and rainfall is meager, effective utilization of carry-over residual soil moisture and conservation agriculture become imperative for second crop production after rice. Implementation of suitable tillage/seeding methods and other agro-techniques are thus very much important to achieve this objective. In this study four pulse crops (lathyrus, blackgram, pea, and greengram) were sown utilizing carry-over residual soil moisture and with different tillage/seeding methods viz. relay cropping (RC)/farmers’ practice, reduced tillage (only two ploughing) (RT), conventional tillage (CT) and zero tillage (ZT). Study revealed that the highest grain yields of 580, 630, 605 and 525 kg ha⁻¹ were obtained from lathyrus, blackgram, pea and green gram, respectively, with RT treatment. On the other hand, with conventional tillage, 34-44% lower yields were obtained than that of RT. Crops with reduced tillage performed better than that with zero tillage or relay cropping also. Impacts of different tillage methods on important soil physical properties like infiltration, bulk density were also studied after harvesting first crop (rice) and before growing second crops (pulses) in rice fallow. The lowest mean bulk density (1.42) was recorded in the surface soils of CT treatment while the corresponding value under ZT treatment was 1.54 Mg m⁻³.     

Irrigation for crops in a sub-humid environment

Summary A four year study examined the effect of irrigating at various water deficits at different times in the growing season, in combination with a range of nitrogen fertilizer rates, on the growth, yield and quality of cotton. The major effect of irrigation treatment on growth was to increase leaf area and plant size; net assimilation rate in the vegetative phase was not affected by irrigation treatment. The initial rate of boll setting was slightly faster in low nitrogen and less frequent irrigation treatments, but by day 180 (immediately prior to defoliation), all treatments had 60% of total dry weight as bolls and 7% as leaf. The best irrigation strategy varied from year to year due to the variable rainfall pattern. Irrigation when 80% of the available soil moisture had been depleted in the first half of the season only decreased total lint yield by up to 12% in two of the four seasons. During the second half of the season the 80% level of depletion decreased yield by an average of 15% but gave an earlier crop. Yield was reduced by up to 17% if irrigation at 40–60% of available moisture depletion in the first half of the season was followed by irrigation at 80% of available moisture depletion in the second half of the season. A rainfed treatment yielded from 16 to 43% less than the heaviest yielding irrigation treatment. After irrigation there was evidence of poor aeration in the soil which was most severe and lasted the longest at 30 cm depth. Heaviest yields were obtained with 100–150 kgN ha^–1, except in rainfed treatments where 0–50 kgN ha^–1 was sufficient. Irrigation at only 40% of available moisture depletion decreased nitrogen uptake in all seasons. Treatment effects on fibre quality in these experiments were small and variable. Nitrogen fertilizer generally increased length and strength but decreased micronaire. Stress during boll filling decreased micronaire and length in two of the four seasons.     

Growth stage scheduling criteria for sprinkler-irrigated soybeans

Summary Soybean [Glycine max (L.) Merr.] producers in the Great Plains region usually employ either a seasonal soil water balance approach, or a growth stage sensitivity approach, relative to scheduling sprinkler irrigation events. We conducted an empirical evaluation of the response of six soybean cultivars to three irrigation strategies. One was an irrigation scheduling (IS) system based solely on maintaining a soil water content in the root zone between 50% and 80% of the total plant available soil water capacity. The other two strategies involved the same depletion criterion for triggering irrigation events, except that the first irrigation was intentionally delayed until the flowering (FL) stage, or the mid-pod elongation (PD) stage. The total water amount applied during each season was approximately similar for the IS, FL, and PD strategies. Thus, the primary difference among the three strategies was the time frame during which irrigation events were scheduled. In the 1983 test, the yields attained in the IS, FL, and PD treatments were not significantly different from each other (i.e. 4.08, 4.08, and 4.04 Mg/ha, respectively), and were nearly double the yield obtained in the nonirrigated (NI) check treatment (2.29 Mg/ha). In the 1984 test, the yields of the IS, FL, and PD treatments were again not significantly different (2.02, 2.05, and 2.22 Mg/ha, respectively). However, the 1984 yield response to irrigation was also not significant relative to the NI check (1.90 Mg/ha), primarily because of low plant populations and a shorter growing season. Thus, this two-year experiment indicated that delaying irrigation until the FL or the PD stages of soybean reproductive development could be just as effective (i.e. 1983 data), or at least no more ineffective (i.e. 1984 data), in enhancing soybean yield compared to the IS strategy (Fig. 1). The soil water balance and soybean growth stage sensitivity approaches, when combined, could thus constitute an effective strategy of soybean sprinkler irrigation management in the Great Plains region.Contribution of the Department of Agronomy and Department of Agricultural Engineering, University of Nebraska, Lincoln, NE 68583. Published as Paper no. 8461, Journal Series, Nebraska Agric. Exp. Stn. Project no. 12-091. Research partially funded by grants received from the Nebraska Soybean Development, Utilization, and Marketing Board     

Model for assessing impact of salinity on soil water availability and crop yield

The salinity condition in the root zone hinders moisture extraction from soil by plants, because of osmotic potential development in soil water due to presence of salts, which ultimately, decreases transpiration of plants and thereby affects crop yield. Therefore, an effort was made in this study to quantify the impact of salinity on soil water availability to plants. The movement of salts under irrigation and evapotranspiration regimes in root zone of soil profile was studied throughout the growing season of wheat crop with adopting exponential pattern of root water uptake. A model was developed to analyze soil water balance to find out moisture deficit because of salinity. A non-linear relationship was formulated between moisture content and salt concentration for simultaneous prediction. The Crank–Nicolson method of Finite Differencing was used to solve the differential equations of soil water and solute transport. The effect of various salt concentrations on transpiration was analyzed to develop a relationship between relative evapotranspiration and relative yield. Relationships among salt concentration, matric potential, moisture deficit and actual transpiration were also established to provide better understanding about impact of salinization and to provide guidelines for obtaining better crop yields in saline soils.     

Effect of different cropping options on plant-available water of surface-drained vertisols in the Ethiopian highlands

The productivity of the Vertisols in the Ethiopian highlands could be raised by facilitating the removal of excess water from the fields in the main rainy season. This could be accomplished by the introduction of an animal powered broadbed maker (BBM) which shapes the soil into broadbeds and furrows. Thus with proper drainage, early sowing of crops becomes feasible. This study compared the plant-available water in the soil layer and the water use efficiency of local wheat and eight other cropping options and also assessed the grain and fodder productivities. Replacing late-sown local wheat with an early-sown improved wheat variety (ET-13) improved the utilization of the plant-available water during the rainy season and significantly increased grain and straw yields with a high rate of water use efficiency. The variations of the available moisture in the soil layer between the different cropping options tested were small during the rainy months of July and August due to the continuing replenishment of the used water. Differences of plant-available water in both upper and lower soil layers for the various cropping options became distinct at the onset of the dry season. Even though results showed that growing of a sequential crop, such as grass pea, following wheat is possible with a starter irrigation in the dry season, yields were generally depressed.     

微润灌水头压力对温室番茄生长及水分利用效率的影响

【目的】探明微润灌条件下温室番茄适宜的水头压力,提高水分利用效率。【方法】以滴灌灌溉为对照(CK),设置水头压力1 m(T_1)、1.5 m(T_2)、2 m(T_3)、2.5 m(T_4)4种试验处理,研究了微润灌条件下不同水头压力对土壤水分分布、番茄生长、耗水规律、产量及水分利用效率的影响。【结果】微润灌水头压力显著影响土壤含水率和湿润区范围,与滴灌处理相比,微润灌处理土壤含水率始终处于较高状态,形成持续稳定的水分环境;T_1、T_2、T_3、T_4处理定植100 d的土壤含水率较定植20 d的下降24.9%、21.54%、19.18%和16.93%,水头压力越高,下降幅度越小,土壤水分环境越稳定;定植初期,滴灌土壤水分环境对植株生长有利,番茄生长较好,随着生育期的延长,微润灌地埋优势充分发挥,后期微润灌番茄生长明显优于滴灌处理;在整个生育期内,番茄株高及茎粗的生长量、生长速率均随着水头压力的提高逐渐增大;番茄在开花坐果期和结果盛期耗水量较大,苗期和结果末期耗水量相对较低,全生育期T_1、T_2、T_3、T_4处理耗水量分别为192.3、216.4、235.8、262.3 mm,水头压力越高,耗水量越大;各处理水分利用效率表现为CK相似文献   

Effect of surface and subsurface drip fertigation on sweet corn rooting,uptake, dry matter production and yield

Summary Subsurface (SS) drip fertigation may increase sweet corn ear yield relative to surface (S) fertigation, because immobile nutrients are delivered at the center of the soil-root volume rather than on top of the soil. A container (1 × 1 × 1 m) experiment was conducted on a loessial soil (Haploxeralf) to test this hypothesis. Marketable and total ear yields were higher for tricklers placed 30 cm below the soil surface (3.22 and 4.90 kg m^–2, respectively) than on the surface (2.86 and 4.30 kg m^–2, respectively). Total fresh weight, dry matter production and plant height during the growing season were also greater for subsurface emitters. Deep trickler position significantly increased P and K content at the center of the root zone. The enhanced concentration apparently stimulated plant rooting which, together with the higher nutrient activity in the soil solution, increased P and K uptake rates, which in turn facilitated the higher dry matter production and commercial yield relative to surface trickler placement. The higher root activity in SS than in S fertigation was reconfirmed by soil air CO₂ concentration measurements which showed significant differences between the two treatments during the growth season.On studies in the ARO from The College of Postgraduates of Mexico, Montecillos, Mexico.