Approach of water-salt regulation using micro-sprinkler irrigation in two coastal saline soils

This study aimed to investigate whether saline silt and sandy loam coastal soils could be reclaimed by micro-sprinkler irrigation.The experiments were run using moderately salt-tolerant tall fescue grass.Micro-sprinkler irrigation in three stages was used to regulate soil matric potential at a 20-cm soil depth.Continued regulation of soil water and salt through micro-sprinkler irrigation consistently resulted in an increasingly large low-salinity region.The application of the three stages of soil wateresalt regulation resulted in an absence of salt accumulation throughout the soil profile and the conversion of highly saline soils into moderately saline soils.There were increases in the plant height,leaf width,leaf length,and tiller numbers of tall fescue throughout the leaching process.The results showed that micro-sprinkler irrigation in three soil water and salt regulation stages can be used to successfully cultivate tall festuca in highly saline coastal soil.This approach achieved better effects in sandy loam soil than in silt soil.Tall fescue showed greater survival rates in sandy loam soil due to the rapid reclamation process,whereas plant growth was higher in silt soil because of effective water conservation.In sandy loam,soil moisture should be maintained during soil reclamation,and in silt soil,soil root-zone environments optimal for the emergence of plants should be quickly established.Micro-sprinkler irrigation can be successfully applied to the cultivation of tall fescue in coastal heavy saline soils under a three-stage soil wateresalt regulation regime.

Effects of water application intensity of microsprinkler irrigation on water and salt environment and crop growth in coastal saline soils

Laboratory and field experiments were conducted to investigate the effects of water application intensity（WAI） on soil salinity management and the growth of Festuca arundinacea（festuca） under three stages of water and salt management strategies using microsprinkler irrigation in Hebei Province, North China. The soil water content（è） and salinity of homogeneous coastal saline soils were evaluated under different water application intensities in the laboratory experiment. The results indicated that the WAI of microsprinkler irrigation influenced the è, electrical conductivity（ECe） and p H of saline soils. As the WAI increased, the average values of è and ECe in the 0–40 cm profile also increased, while their average values in the 40–60 cm profile decreased. The p H value also slightly decreased as depth increased, but no significant differences were observed between the different treatments. The time periods of the water redistribution treatments had no obvious effects. Based on the results for è, ECe and p H, a smaller WAI was more desirable. The field experiment was conducted after being considered the results of the technical parameter experiment and evaporation, wind and leaching duration. The field experiment included three stages of water and salt regulation, based on three soil matric potentials（SMP）, in which the SMP at a 20-cm depth below the surface was used to trigger irrigation. The results showed that the microsprinkler irrigation created an appropriate environment for festuca growth through the three stages of water and salt regulation. The low-salinity conditions that occurred at 0–10 cm depth during the first stage（-5 k Pa） continued to expand through the next two stages. The average p H value was less than 8.5. The tiller number of festuca increased as SMP decreased from the first stage to the third stage. After the three stages of water and salt regulation, the highly saline soil gradually changed to a low-saline soil. Overall, based on the salt desalinization, the microsprinkler irrigation and three stages of water and salt regulation could be successfully used to cultivate plants for the reclamation of coastal saline land in North China.

Reclamation of Coastal Saline Soils by Bnilding Dykes for Freshwater Fish－Farming

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Effect of different water application intensity and irrigation amount treatments of microirrigation on soil-leaching coastal saline soils of North China

In coastal regions, Bohai Gulf is one of the most affected areas by salinization. To study the effects of mocrosprinkler irrigation on the characteristics of highly saline sandy loam soil（ECe（saturated paste extract）=22.3 d S m^–1; SAR（sodium adsorption ratio）=49.0） of North China, a laboratory experiment was conducted. Five water application intensity（WAI） treatments（1.7, 3.1, 5.3, 8.8, and 10.1 mm h^–1）, five irrigation amount（IA） treatments（148, 168, 184, 201, and 223 mm） and three time periods of water redistribution（0, 24 and 48 h） were employed in the study. A compounding microsprinkler system was used for the WAI treatments, and a single microsprinkler was used for the IA treatments. The results indicated that, as soil depth increased, soil water content（θ） increased and then slightly decreased; with WAI and IA consistently increasing, the relatively moist region expanded and the average θ increased. Meanwhile, soil ECe increased as soil depth increased, and the zone with low soil salinity expanded as WAI and IA increased. Although the reduction of the average SAR was smaller than that of the average electrical conductivity of the ECe, these variables decreased in similar fashion as WAI and IA increased under microsprinkler irrigation. The average p H decreased as soil depth increased. Longer time periods of water redistribution led to lower salinity and slight expansion of the SAR zone. Considering the effects of leached salts in coastal saline soils, greater WAI and IA values are more advantageous under unsaturated flow conditions, as they cause better water movement in the soil. After leaching due to microsprinkler irrigation, highly saline soil gradually changes to moderately saline soil. The results provide theoretical and technological guidance for the salt leaching and landscaping of highly saline coastal environments.

Calibration of Soil Electromagnetic Conductivity in Inverted Salinity Profiles with an Integration Method

Various calibration methods have been propounded to determine profiles of apparent bulk soil electrical conductivity (ECa) and soil electrical conductivity of a saturated soil paste extract (ECe) or a 1:5 soil water extract (EC1:5) using an electromagnetic induction instrument (EM38). The modeled coefficients, one of the successful and classical methods hitherto, were chosen to calibrate the EM38 measurements of the inverted salinity profiles of characteristic coastal saline soils at selected sites of Xincao Farm, Jiangsu Province, China. However, this method required three parameters for each depth layer. An integration approach, based on an exponential decay profile model, was proposed and the model was fitted to all the calibration sites. The obtained model can then be used to predict EC1:5 at a certain depth from electromagnetic measurements made using the EM38 device positioned in horizontal and vertical positions at the soil surface. This exponential decay model predicted the EC1:5 well according to the results of a one-way analysis of variance, and the further comparison indicated that the modeled coefficients appeared to be slightly superior to, but not statistically different from, this exponential decay model. Nevertheless, this exponential decay model was more significant and practical because it depended on less empirical parameters and could be used to perform point predictions of EC1:5 continuously with depth.

Effects of Inoculation of Arbuscular Mycorrhizal Fungus and Apophysomyces spartina on P-uptake of Castor Oil Plant(Ricinus communis L.) and Rhizosphere Soil Enzyme Activities under Salt Stress

[Objective] In order to explore the mechanism of combined inoculation mi- croorganisms in improving coastal saline soil property and plant growth. [Method] The pot experiment was used to assess the effects of different inoculated proportion of arbuscular mycorrhizal fungi （AMF） and Phosphate-sotubilizing fungus. Apophysomyces spartina, on growth, chlorophyll contents, P-uptake of castor bean （Ricinus communis L.） and rhizosphere soil pH values, available P concentrations, enzyme activities. [Result] The mixed inoculation of AMF and A. spartina significantly reduced soil pH value, increased soil available phosphorous contents, improved the activities of soil invertase, urease, neutral phosphatase, and alkaline phosphatase. Chlorophyll contents, P-uptake, and plant dry weight of castor bean were also in- creased. The optimal proportion of the number of AMF spores to A. spartina colonies was 28.56：11.5×10^5, which had positive effects on saline soil and could stimulate plant growth under greenhouse condition. [Conclusion] Appropriate propor- tion of AMF and A. spartina had the potential to enhance coastal saline soil prop- erty and promote castor bean growth.

Introduction and Selection of Salt-tolerant Wheat in Yellow River Delta

[Objective] This study was to screen a salt-tolerant wheat variety in Dongying, a city in the center of the Yellow River Delta with a large area of coastal saline soil. [Method] Total 9 salt-tolerant, stress-resistant and high-yielding wheat varieties （lines） were introduced, and they were cultivated in the saline soil with total salt content of 3-4 g/kg with Dekang 961 as the control. [Result] The yields of Jinan 18, Yanjian 14 and Shanrong 3 were all significantly higher than that of Dekang 961 （P〈0.05）. These three varieties （lines） all ripen before June 13 with moderate growth period that does not affect the seeding of next-season crop. [Conclusion] Jinan 18, Yanjian 14 and Shanrong 3 are suitable for planting in light and median saline soil in the Yellow River Delta.

Soil texture affects the conversion factor of electrical conductivity from 1:5 soil-water to saturated paste extracts

Electrical conductivity(EC)of soil-water extracts is commonly used to assess soil salinity.However,its conversion to the EC of saturated soil paste extracts(ECe),the standard measure of soil salinity,is currently required for practical applications.Although many regression models can be used to obtain ECe from the EC of soil-water extracts,the application of a site-specific model to different sites is not straightforward due to confounding soil factors such as soil texture.This study was conducted to develop a universal regression model to estimate a conversion factor(CF)for predicting EC_(e) from EC of soil-water extracts at a 1:5 ratio(EC_(1:5)),by employing a site-specific soil texture(i.e.,sand content).A regression model,CF=8.9105e^(0.0106sand)/1.2984(r^(2)=0.97,P<0.001),was developed based on the results of coastal saline soil surveys(n=173)and laboratory experiments using artificial saline soils with different textures(n=6,sand content=10%-65%)and salinity levels(n=7,salinity=1-24 dS m^(-1)).Model performance was validated using an independent dataset and demonstrated that EC_(e) prediction using the developed model is more suitable for highly saline soils than for low saline soils.The feasibility of the regression model should be tested at other sites.Other soil factors affecting EC conversion factor also need to be explored to revise and improve the model through further studies.