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.

Feasibility and Prospect about the Cultivation of Apocynum venetum L. in Coastal Salt-affected Soils

[Objective]The aim of this paper was to analyze the feasibility and prospect of Apocynum venetum L.cultivation in coastal salt-affected soils.[Method]The habitat and distribution of Apocynum venetum L.in coastal area of north China were studied.A method to integrate the charicteristics of Apocynum venetum L.（Luobuma） with the utilization of salt-affected soils in this region was proposed.[Result]The introduction,domestication and growth of plants on coastal salt-affected soils can realize the protection of endangered wild species,and achieve the purpose of improving soil.The characteristics of Apocynum venetum L.can produce optimum economic and ecological benefits.[Conclusion]The implementation will provide references for the protection and exploitation of wild plant,and it is of positive significance for the integration of soil and plant resources.

Microbial diversity in the saline-alkali soil of a coastal Tamarix chinensis woodland at Bohai Bay, China

Soil salinization or alkalization is a form of soil desertification. Coastal saline-alkali soil represents a type of desert and a key system in the network of ecosystems at the continent-ocean interface. Tamarix chinensis is a drought-tolerant plant that is widely distributed in the coastal saline-alkali soil of Bohai Bay, China. In this study, we used 454 pyrosequencing techniques to investigate the characteristics and distribution of the microbial diversity in coastal saline-alkali soil of the T. chinensis woodland at Bohai Bay. A total of 20,315 sequences were obtained, representing 19 known bacterial phyla and a large proportion of unclassified bacteria at the phylum level. Proteobacteria, Acidobacteria and Actinobacteria were the predominant phyla. The coverage of T. chinensis affected the microbial composition. At the phylum level, the relative abundance of y-Proteobacteria and Bacteroidetes decreased whereas Actinobacteria increased with the increasing coverage of T. chinensis. At the genus level, the proportions of Steroidobacter, Lechevalieria, Gp3 and Gp4 decreased with the increase of the vegetation coverage whereas the proportion of Nocardioides increased. A cluster analysis showed that the existing T. chinensis changed the niches for the microorganisms in the coastal saline-alkali soil, which caused changes in the microbial community. The analysis also distinguished the microbial community structure of the marginal area from those of the dense area and sparse area. Furthermore, the results also indicated that the distance to the seashore line could also affect certain groups of soil bacteria in this coastal saline-alkali soil, such as the family Cryomorphaceae and class Flavobacteria, whose population decreased as the distance increased. In addition, the seawater and temperature could be the driving factors that affected the changes.

Sufficiency and Deficiency Indices of Soil Available Zinc for Rice in the Alluvial Soil of the Coastal Yellow Sea

To determine the sufficiency and deficiency indices of soil available Zn by the Agro Services International （ASI） method （ASI-Zn） for Zn fertilizer recommendation in rice production in the alluvial soil of the coastal Yellow Sea, the relationship between relative rice yield and soil available ASI-Zn concentration was analyzed from a ten-field experiment with various soil test classes ranging from low to high fertility in 2005 and 2006, and nine Zn fertilizer application rates （0, 7.5 15, 22.5, 30, 37.5, 45, 52.5 and 60 kg Zn/ha） arranged at random with three replications in each field. There was a significant quadratic relationship between soil available ASI-Zn and rice yield, and a significant linear relationship between soil available ASI-Zn concentration and Zn fertilization rate. For rice variety Wuyujing 3, soil available ASI-Zn was deficient when the value was at lower than 1 mg Zn/L, low at 1 to 2 mg Zn/L, sufficient at 1 to 2 mg Zn/L, excessive at higher than 7.5 mg Zn/L. Thus, Zn fertilizer recommendation could be done according to the sufficiency and deficiency indices of soil ASI-Zn. For most of alluvial soils of the coastal Yellow Sea in the study, the available ASI-Zn was lower than 1 mg Zn/L, and then the optimum application rate of Zn fertilizer was about 20 kg Zn/ha.

Effects of Reclamation on Soil Carbon and Nitrogen in Coastal Wetlands of Liaohe River Delta,China

To evaluate the influence of wetland reclamation on vertical distribution of carbon and nitrogen in coastal wetland soils, we measured the soil organic carbon(SOC), soil total nitrogen(STN) and selected soil properties at five sampling plots(reed marsh, paddy field, corn field, forest land and oil-polluted wetland) in the Liaohe River estuary in September 2013. The results showed that reclamation significantly changed the contents of SOC and STN in the Liaohe River estuary(P < 0.001). The SOC concentrations were in the order: oil-polluted wetland > corn field > paddy field > forest land > reed marsh, with mean values of 52.17, 13.14, 11.46, 6.44 and 6.16 g/kg, respectively. STN followed a similar order as SOC, with mean values of 1351.14, 741.04, 632.32, 496.17 and 390.90 mg/kg, respectively. Interaction of reclamation types and soil depth had significant effects on SOC and STN, while soil depth had significant effects on SOC, but not on STN. The contents of SOC and STN were negatively correlated with pH and redox potential(Eh) in reed marsh and corn field, while the SOC and STN in paddy field had positive correlations with electrical conductivity(EC). Dissolved organic carbon(DOC), ammonium nitrogen(NH_4^+-N) and nitrate nitrogen(NO_3~–-N) were also significantly changed by human activities. NH_4^+-N and NO_3~–-N increased to different degrees, and forest land had the highest NO_3~–-N concentration and lowest DOC concentration, which could have been caused by differences in soil aeration and fertilization. Overall, the results indicate that reed harvest increased soil carbon and nitrogen release in the Liaohe River Estuary, while oil pollution significantly increased the SOC and STN; however, these cannot be used as indicators of soil fertility and quality because of the serious oil pollution.

Effects of Tamarisk shrub on physicochemical properties of soil in coastal wetland of the Bohai Sea

There are many different and even controversial results concerning the effects of Tamarisk on the physicochemical properties of soil. A year-round monitoring of soil salinity, p H and moisture is conducted beneath the Tamarisk shrub in a coastal wetland in the Bohai Sea in China, to ascertain the effects of Tamarisk on the physicochemical properties of soil in coastal wetland. Compared with the control area, the soil moisture content is lower around the area of the taproot when there is less precipitation in the growing season because of water consumption by Tamarisk shrub. However, the soil moisture content is higher around the taproot when there is more precipitation in the growing season or in the non-growing period because of water conservation by the rhizosphere. The absorption of salt by the Tamarisk shrub reduces the soil salinity temporarily, but eventually salt returns to the soil by the leaching of salt on leaves by rainfall or by fallen leaves. The annual average soil moisture content beneath the Tamarisk shrub is lower than the control area by only 6.4%, indicating that the Tamarisk shrub has little effect on drought or water conservation in soils in the temperate coastal wetland with moderate annual precipitation. The annual average salinity beneath the Tamarisk shrub is 18% greater than that of the control area, indicating that Tamarisk does have an effect of rising soil salinity around Tamarisk shrubs. The soil p H value is as low as 7.3 in summer and as high as 10.2 in winter. The p H of soil near the taproot of the Tamarisk shrubs is one p H unit lower than that in the control area during the growing season. The difference in p H is less different from the control area in the non-growing season, indicating that the Tamarisk shrub does have the effect of reducing the alkalinity of soil in coastal wetland.

Soil Salinity and Soil Water Content Estimation Using Digital Images in Coastal Field:A Case Study in Yancheng City of Jiangsu Province,China

Soil is the essential part for agricultural and environmental sciences,and soil salinity and soil water content are both the important influence factors for sustainable development of agriculture and ecological environment.Digital camera,as one of the most popular and convenient proximal sensing instruments,has its irreplaceable position for soil properties assessment.In this study,we collected 52 soil samples and photographs at the same time along the coast in Yancheng City of Jiangsu Province.We carefully analyzed the relationship between soil properties and image brightness,and found that soil salt content had higher correlation with average image brightness value than soil water content.From the brightness levels,the high correlation coefficients between soil salt content and brightness levels concentrated on the high brightness values,and the high correlation coefficients between soil water content and brightness levels focused on the low brightness values.Different significance levels(P)determined different brightness levels related to soil properties,hence P value setting can be an optional way to select brightness levels as the input variables for modeling soil properties.Given these information,random forest algorithm was applied to develop soil salt content and soil water content inversion models using randomly 70%of the dataset,and the rest data for testing models.The results showed that soil salt content model had high accuracy(R_(v)^(2)=0.79,RMSE_(v)=12 g/kg,and RPD_(v)=2.18),and soil water content inversion model was barely satisfied(R_(v)^(2)=0.47,RMSE_(v)=3.04%,and RPD_(v)=1.38).This study proposes a method of modeling soil properties with a digital camera.Combining unmanned aerial vehicle(UAV),it has potential popularization and application value for precise agriculture and land management.

Land Suitability Evaluation for Oil Palm (<i>Elaeis guineensis</i>Jacq.) in Coastal Plains of Southwest Cameroon

Declining yields in oil palm fresh fruit bunch (FFB) have been recorded over the past years in the coastal lowlands of southwest Cameroon and current actual yields are very low (<12 t FFB ha−1•yr−1) compared to the potential yields (25 t FFB ha−1•yr−1). One of the problems limiting optimum oil palm production is lack of detailed pedological information to guide plantation establishment and management. A land suitability evaluation was carried out for some major oil palm producing areas of southwest Cameroon to identify land qualities limiting optimal production. Thirteen sites (9 with sedimentary parent materials and 4 with volcanic parent material) were evaluated using a parametric method. Results indicate that climate was not a major limiting factor for oil palm production in coastal plains of southwest Cameroon. However, soil physical characteristics (mainly clayey texture and poor drainage) and soil fertility constitute limitations to oil palm production. Specifically, limitations in cation exchange capacity (CEC), base saturation (BS), organic carbon (OC) and pH were slight to moderate while K mole fraction was the most severe and the most limiting in all the sites. The fertility limitations were more pronounced in soils derived from sedimentary parent materials where 33% had limitations caused by soil pH and OC compared to none for volcanic soils. In addition, 77.8% of sedimentary soils had limitations caused by CEC compared to 25% for volcanic soils. Considering the overall suitability, soils derived from volcanic parent materials were potentially more suitable for oil palm cultivation ((S3)—50%, (S2)—50%) compared to sedimentary soils ((N)—11%, (S3)—78% and (S2)—11%). Based on the suitability classes of the different soils derived from dissimilar parent materials, appropriate site-specific soil management is needed to improve oil palm yields, especially with emphasis on K fertilization and improved soil water management. Plantation management in coastal plains of South West Cameroon therefore should factor in differences in soil parent material.

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.

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.

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.