Temporal-spatial distribution and variability of cadmium contamination in soils in Shenyang Zhangshi irrigation area,China

Heavy metal contamination in soils has been of wide concern in China in the last several decades. The heavy metal contamination was caused by sewage irrigation, mining and inappropriate utilization of various agrochemicals and pesticides and so on. The Shenyang Zhangshi irrigation area （SZIA） in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years duration. This study investigated the spatial distribution and temporal variation of soil cadmium contamination in the SZIA. The soil samples were collected from the SZIA in 1990 and 2004; Cd of soils was analyzed and then the spatial distribution and temporal variation of Cd in soils was modelled using kriging methods. The kriging map showed that long-term sewage irrigation had caused serious Cd contamination in topsoil and subsoil. In 2004, the Cd mean concentrations were 1.698 and 0.741 mg/kg, and the maxima 10.150 and 7.567 mg/kg in topsoils （0-20 cm） and subsoils （20-40 cm） respectively. These values are markedly more than the Cd levels in the second grade soil standard in China. In 1990, the Cd means were 1.023 and 0.331 mg/kg, and the maxima 9.400 and 3.156 mg/kg, in topsoils and subsoils respectively. The soil area in 1990 with Cd more than 1.5 mg/kg was 2701 and 206.4 hnl2 in topsoils and subsoils respectively; and in 2004, it was 7592 and 1583 hm^2, respectively. Compared with that in 1990, the mean and maximum concentration of Cd, as well as the soil area with Cd more than 1.5 mg/kg had all increased in 2004, both in topsoils and subsoils.

Geostatistical analysis of variations in soil salinity in a typical irrigation area in Xinjiang, northwest China

Characterizing spatial and temporal variability of soil salinity is tremendously important for a variety of agronomic and environmental concerns in arid irrigation areas. This paper reviews the characteristics and spatial and temporal variations of soil salinization in the Ili River Irrigation Area by applying a geostatistical approach. Results showed that: (1) the soil salinity varied widely, with maximum value of 28.10 g/kg and minimum value of 0.10 g/kg, and was distributed mainly at the surface soil layer. Anions were mainly SO42- and Cl-, while cations were mainly Na+ and Ca2+; (2) the abundance of salinity of the root zone soil layer for different land use types was in the following order: grassland > cropland > forestland. The abundance of salinity of root zone soil layers for different periods was in the following order: March > June > September; (3) the spherical model was the most suitable variogram model to describe the salinity of the 0-3 cm and 3-20 cm soil layers in March and June, and the 3-20 cm soil layer in September, while the exponential model was the most suitable variogram model to describe the salinity of the 0-3 cm soil layer in September. Relatively strong spatial and temporal structure existed for soil salinity due to lower nugget effects; and (4) the maps of kriged soil salinity showed that higher soil salinity was distributed in the central parts of the study area and lower soil salinity was distributed in the marginal parts. Soil salinity tended to increase from the marginal parts to the central parts across the study area. Applying the kriging method is very helpful in detecting the problematic areas and is a good tool for soil resources management. Managing efforts on the appropriate use of soil and water resources in such areas is very important for sustainable agriculture, and more attention should be paid to these areas to prevent future problems.

Modelling Irrigation and Salinity Management Strategies in the Ord Irrigation Area

The Ord River Irrigation Area (ORIA) is located within northern Western Australia near the Northern Territory border. Since the beginning of irrigated agriculture in the ORIA the groundwater levels have been continuously rising and are now close to the soil surface in some parts of ORIA in northern Western Australia. The groundwater is now saline throughout most of the ORIA and soil salinity risks are high where the watertables are shallow. This research evaluated irrigation and salinity management strategies for sugarcane and maize crops grown over deep and shallow, non-saline and saline watertables in the ORIA. The LEACHC model, calibrated using field data, was used to predict the impacts of various irrigation management strategies on water use and salt accumulation in the root zone. This study concluded that irrigation application equal to 100% of total fortnightly pan evaporation applied at 14 day intervals was a good irrigation strategy for the maize grown over a deep watertable area. This strategy would require around 11 ML/ha of irrigation water per growing season. Irrigation application equal to 75% of total fortnightly pan evaporation, applied every fortnight during first half of the growing season, and 75% of total weekly pan evaporation, applied on a weekly basis during second half of the growing season, would be the best irrigation strategy if it is feasible to change the irrigation interval from 14 to seven days. This irrigation strategy is predicted to have minimal salinity risks and save around 40% irrigation water. The best irrigation strategy for sugarcane grown on Cununurra clay over a deep watertable area would be irrigation application equal to 50% of the total fortnightly pan evaporation, applied every fortnight during first quarter of the growing season, and irrigation application amounts equal to 100% of total weekly pan evaporation, applied every week during rest of the season. The model predicted no soil salinity risks from this irrigation strategy. The best irrigation strategy for sugarcane over a non-saline, shallow watertable of one or two m depth would be irrigation application amounts equal to 50% of total fortnightly pan evaporation applied every fortnight. In the case of a saline watertable the same irrigation strategy was predicted to the best with respect to water use efficiency but will have high salinity risks without any drainage management.

AN APPROACH TO THE FORESTRY PROBLEMS AND TACTS IN THE NEW IRRIGATION AREA OF YANGHUANG IN NINGXIA

This article exponded the importance of forestry construction in Ningxia, Yang HuangNew Irrigation Area economy development. It analysed the problems that may exist in theforestry constructions of New Irrigation Area, (such as the monostructure of trees,struction simplicity, monoculture of stand and lack of functions) And put forward the cont-er actions and construtioes advices.

CAS-based Water Resources Optimal Allocation and Dynamic Simulation for Sewage Irrigation Area

Based on the theory of complex adaptive system(CAS),the optimal allocation model of water resources in sewage irrigation areas was established,which provided new ideas and application value for the rational utilization of agricultural production and waste water resources.The results demonstrated that the difference of crop energy capture mainly depended on the development stage.Waste water with a certain concentration was able to promote crop growth,while excessive concentration inhibited crop growth.The correlation between water absorption rate and leaf area index was close(R=0.9498,p<0.01).The amount of bad seeds increased at a speed of 34.7·d^-1,when system irrigated randomly in the seedling stage,while it tended to remain stable at a speed of 0.3·d^-1 after plants entering the mature stage which impacted the total yields of crops.

Spatial distribution of Cd and Cu in soils in Shenyang Zhangshi Irrigation Area(SZIA),China

Heavy metal contamination of soils,derived from sewage irrigation,mining and inappropriate utilization of various agrochemicals and pesticides,and so on,has been of wide concern in the last several decades.The Shenyang Zhangshi Irrigation Area(SZIA) in China is a representative area of heavy metal contamination of soils resulting from sewage irrigation for about 30 years.This study investigated the spatial distribution and temporal variation of soil cadmium(Cd) and copper(Cu) contamination in the SZIA.The soil samples were collected from the SZIA in 1990 and 2004;Cd and Cu in soils was analyzed and then the spatial distribution and temporal variation of Cd and Cu in soils were modeled using Kriging methods.The results show that long-term sewage irrigation had caused serious Cd and Cu contamination in soils.The mean and the maximum of soil Cd are markedly higher than the levels in second grade standard soil(LSGSS) in China,and the maximum of soil Cu is close to the LSGSS in China in 2004 and is more than the LSGSS in China in 1990.The contamination magnitude of soil Cd and the soil extent of Cd contamination had evidently increased since sewage irrigation ceased in 1992.The contamination magnitude of soil Cu and the soil extent of Cu contamination had evidently increased in topsoil,but obviously decresed in subsoil.The soil contamination of Cd and Cu was mainly related to Cd and Cu reactivation of contaminated sediments in Shenyang Xi River and the import of Cd and Cu during irrigation.The eluviation of Cd and Cu in contaminated topsoil with rainfall and irrigation water was another factor of temporal-spatial variability of Cd and Cu contamination in soils.

Application of Self-pressure Sprinkler Irrigation Technology to Grassland Vegetation Restoration in Alpine Arid Areas

To study the application of self-pressure sprinkler irrigation technology to vegetation restoration of grassland in alpine arid areas,three treatments including fenced grassland(FG),fencedirrigated grassland(FA),and free grazing grassland(CK) were compared in respect of primary productivity.The results showed that the community coverage of FA was only 35.96% higher than that of FG and 152.69% higher than that of CK;the plant height of FA was only 76.71% higher than that of FG and 155.77% higher than that of CK;the productivity of the community in FA was only 24.10% higher than that of FG and 110.00% higher than that of CK.It indicates that the self-pressure sprinkler irrigation technology has certain demonstration and promotion potential in vegetation restoration of grassland in alpine regions and can provide a new way for the sustainable development of grassland animal husbandry in Tibet.

Study on the Suitable Water-Saving Irrigation Technology for Mining Areas in the Northwestern Arid Desert Regions in China

Water is the key factor to ensure plant survival in the process of ecological restoration in the coal base of China northwest deserts. On the premise of meeting the mine production and living water demands, we should take measures such as dirt wastewater treatment and water-saving irrigation to increase income and reduce expenditure and allocate limited water re-sources rationally, to provide mining area ecological restoration maximum usable water resources. The mining dump has large slope and thin soil layer and it is easy to produce surface runoff. So it is particularly important to study the irrigation technology needed to satisfy vegetation restoration, on the premise of guaranteeing not to produce surface runoff and the slope stability. In this paper, through field plot test, the suitable irrigation method for mine slope, slope surface soil moisture migration characteristics and slope stability analysis were studied. Results show that three slope ir-rigation technologies have their own advantages and disadvantages. On the whole, the effect of drip irrigation is the best, micro spray irrigation is the second, infiltrating irrigation is not ideal. The permeability of mine soil slope is very strong, the infiltration rate of the slope direction is the high-est, inverse slope infiltration rate is lowest. In the process of irrigation, with the increase of soil moisture content, slope safety factor is the decreased obviously, the whole slope surface soil moisture content is 14% for the slope stability safety threshold.

The Pollution Characteristic of Polycyclic Aromatic Hydrocarbons (PAHs) in Typical Sewage Irrigation Area in North of China

This research aims to investigate the pollution characteristic of PAHs in Xiaodian sewage irrigation area. The result shows that the concentrations ofPAHs range from 47.94 to 46432.85ng/g while that of the total components of the 16 kinds of PAHs are 5969.81ng/g. PAHs with for rings and more than 4 rings are the main and important pollutants in topsoils of Xiaodian District. The main input of PAHs is combustion source, and the main pollution source in this area is fired coal. The topsoils in Xiaodian District are polluted by human activity in varying degrees. 23 of all 31 topsoil samples have been heavily polluted, especially those located nearby developed industrial townships and irrigation channels.

Baseline of the Use of Solar Irrigation Pump in the Niayes Area in Senegal

Solar irrigation pumps are considered as an alternative to the use of diesel and electric pumps due to the high cost of energy. These pumps are now increasingly used in the Niayes area. Thus, a more in-depth knowledge about the components of a solar pumping system and their characteristics available on the market as well as prices can be beneficial. This study was conducted to have an idea on the baseline of the use of solar irrigation pumps in this area. To perform this study, surveys were conducted among 12 suppliers and 10 service providers located in Dakar, Thies, Louga and Saint-Louis region and among 53 users located in Potou area which is in Louga region. Results show a wide range of pump brands and characteristics. Brands found were Lorentz, LIKOU, SHIMGE, Grundfos, Solar pump, Feili, Difful, JUQIANG, Solar tech, and Asaman. The pumps’ flow rate varies between 2.5 m3/h and 45 m3/h, the pressure ranges from 15 m to 160 m and the power is between 0.072 kW and 10 kW. The price of these pumps varies depending on the brand used and their characteristics. In addition, other materials are available, such as panels with power ranging from 80 W to 330 W and electric cables. The price of these components varies according on the type used. Thus, the investment cost for implementation varies between 640 euros (420,000 CFA) and 25,087 euros (16,455,919 CFA). The cost of installation varies between 76.3 euros (50,000 CFA) and 1219.6 euros (800,000 CFA). Concerning maintenance, it is generally free during the warranty period when the equipment is supplied and installed by the same company. However, the cost of maintenance varies between 152.5 euros and 457.4 euros/year or is estimated at 45.7 euro/maintenance after the warranty years. Investigations conducted among users show that farmers in general do not perform pump maintenance due to a lack of knowledge and financial means. Thus, according to farmers, factors that impact pumps operation are the low sunshine that occurs between December and January and the iron in the water and low well discharge.

Assessment of Groundwater Suitability for Drinking and Irrigation Purpose in the Dimbhe Command Area of River Ghod, Maharashtra, India

The management of the subsurface and surface water resources is important for various purposes. Since the quantity and quality of water available for irrigation in India is variable from place to place, groundwater quality in the Dimbhe command area was evaluated for its suitability for domestic and irrigation purposes by collecting 37 dug well samples during the post monsoon period of 2014. The suitability assessment was made by estimating pH, electrical conductivity, total dissolved solids, and alkalinity besides major cations (Na+, K+, Ca2+, and Mg2+) and anions (, Cl-, , and ). Out of 37 groundwater samples, 5.41% represents good water, 62.16% indicate poor water, 29.73% indicate very poor water and 2.7% indicate water unsuitable for domestic purposes. Based on these analyses, irrigation quality parameters like, sodium absorption ratio, permeability index, Kelley’s ratio, soluble sodium percentage, residual sodium carbonate, %Mg, %Na, and Mg hazard ratio were calculated. Assessment of groundwater samples indicated that majority of them in both the seasons are suitable for irrigation purposes.

Green Control Measures of Weeds in Wheat Fields in Hetao Irrigation Area along the Yellow River

This study was conducted to solve the problem of green weed control in wheat fields in Hetao irrigation area among the Yellow River.Based on the observation of the competition between wheat and weeds in areas where weeds occurred seriously in wheat fields in Hetao irrigation area among the Yellow River,we measured the effects of green weed control measures and wheat yield using different wheat varieties,planting densities,different organic fertilizers,different ploughing times,and different mulching methods.The results showed that the emergence of weeds in wheat fields dominated by Chenopodiaceae weeds,grain amaranth and barnyard grass was more than 10 d later than wheat.Weeds were mainly distributed between rows(holes),and the number of plants accounted for 66.6%(drill seeding)and 97.6%(hole seeding),respectively.And the growth of weeds in rows(holes)was weaker,and the fresh weight of individual plants was 39.3%-41.9%lower than that between rows(holes).The ecological weed inhibitory effect was significant in the early stage of wheat growth;and among the green weed control measures,except that different varieties and planting densities caused no significant difference in weed control effect,other measures had obvious weed control effects.Comprehensive comparison showed that the control effects of plant number in black film full-covered hole seeding,conventional film-covered hole seeding,increasing ploughing times,and applying organic fertilizer free of weed seed pollution were 82.3%,71.7%,22.0%,and 8.6%,respectively;the fresh weight control effects of black film full-covered hole seeding,conventional film-covered hole seeding,increasing ploughing times,and applying organic fertilizer free of weed seed pollution were 98.0%,97.1%,23.9%,and 9.6%,respectively;and the fresh weight control effects of black film full-covered hole seeding,conventional film-covered hole seeding and increasing ploughing times increased wheat yield by 69.4%,56.4%and 21.1%,respectively.The technologies in this study can realize the purposes of mechanized green weed control in organic wheat production and low-cost,high-yield,large-scale production.

Prevention and Management of Soil Secondary Salinization in Paddy Field Irrigation Area

By analyzing the process of soil salt accumulation in irrigation area, and discussing the change of irrigation and drainage methods for drought transformed into water, the control scheme of soil secondary salinization in Wujiazi Irrigation Area was analyzed concretely, and the experience was summarized. After in-depth discussion, the importance of irrigation and drainage methods in the prevention and control of soil secondary salinization in irrigation areas was analyzed.

Effects of combined drip irrigation and sub-surface pipe drainage on water and salt transport of saline-alkali soil in Xinjiang, China

Developing effective irrigation and drainage strategies to improve the quality of saline-alkali soil is vital for enhancing agricultural production and increasing economic returns. In this study, we explored how irrigation and drainage modes (flood irrigation, drip irrigation, and sub-surface pipe drainage under drip irrigation) improve the saline-alkali soil in Xinjiang, China. We aimed to study the transport characteristics of soil water and salt under different irrigation and drainage modes, and analyze the effects of the combination of irrigation and drainage on soil salt leaching, as well as its impacts on the growth of oil sunflower. Our results show that sub-surface pipe drainage under drip irrigation significantly reduced the soil salt content and soil water content at the 0–200 cm soil depth. Under sub-surface pipe drainage combined with drip irrigation, the mean soil salt content was reduced to below 10 g/kg after the second irrigation, and the soil salt content decreased as sub-surface pipe distance decreased. The mean soil salt content of flood irrigation exceeded 25 g/kg, and the mean soil desalination efficiency was 3.28%, which was lower than that of drip irrigation. The mean soil desalination rate under drip irrigation and sub-surface pipe drainage under drip irrigation was 19.30% and 58.12%, respectively. After sub-surface drainage regulation under drip irrigation, the germination percentage of oil sunflower seedlings was increased to more than 50%, which further confirmed that combined drip irrigation and sub-surface pipe drainage is very effective in improving the quality of saline-alkali soil and increasing the productivity of agricultural crops.

Effects of deficit irrigation with saline water on spring wheat growth and yield in arid Northwest China

Field experiments were conducted in 2008 and 2009 to study the effects of deficit irrigation with saline water on spring wheat growth and yield in an arid region of Northwest China. Nine treatments included three salinity levels sl, s2 and s3 （0.65, 3.2, and 6.1 dS/m） in combination with three water levels wl, w2 and w3 （375, 300, and 225 mm）. In 2008, for most treatments, deficit irrigation showed adverse effects on wheat growth; meanwhile, the effect of saline irrigation was not apparent. In 2009, growth parameters of wl treatments were not always optimal under saline irrigation. At 3.2 and 6.1 dS/m in 2008, the highest yield was obtained by wl treatments, however, in 2009, the weight of 1,000 grains and wheat yield both followed the order w2 〉 wl 〉 w3. In this study, spring wheat was sensitive to water deficit, especially at the booting to grain-filling stages, but was not significantly affected by saline irrigation and the combination of the two factors. The results demonstrated that 300-mm irrigation water with a salinity of less than 3.2 dS/m is suitable for wheat fields in the study area.

Low soil temperature reducing the yield of drip irrigated rice in arid area by influencing anther development and pollination

Drip irrigation can produce high rice yields with significant water savings;therefore,it is widely used in arid area water-scarce northern China.However,high-frequency irrigation of drip irrigation with low temperature well water leads to low root zone temperature and significantly reduce the rice yield compared to normal temperature water irrigated rice,for example,reservoir water.The main purpose of this paper is to investigate the effects of low soil temperature on the yield reduction of drip irrigated rice in the spike differentiation stage.The experiment set the soil temperatures at 18℃,24℃and 30℃under two irrigation methods(flood and drip irrigation),respectively.The results showed that,at the 30℃soil temperature,drip irrigation increased total root length by 53%but reduced root water conductivity by 9%compared with flood irrigation.Drip irrigation also increased leaf abscisic acid and proline concentrations by 13%and 5%,respectively.These results indicated that drip irrigated rice was under mild water stress.In the 18℃soil temperature,drip irrigation reduced hydraulic conductivity by 58%,leaf water potential by 40%and leaf net photosynthesis by 25%compared with flood irrigation.The starch concentration in male gametes was also 30%less in the drip irrigation treatment than in the flood irrigation treatment at soil temperature 18℃.Therefore,the main reason for the yield reduction of drip irrigated rice was that the low temperature aggravates the physiological drought of rice and leads to the decrease of starch content in male gametes and low pollination fertilization rate.Low temperature aggravates physiological water deficit in drip irrigated rice and leads to lower starch content in male gametes and low pollination fertilization rate,which is the main reason for the reduced yield of drip irrigated rice.Overall,the results indicated that the low soil temperatures aggravated the water stress that rice was under in the drip irrigated environment,causing declines both in the starch content of male gametes and in pollination rate.Low temperature will ultimately affect the rice yield under drip irrigation.

Effects of nitrogen application rates and irrigation regimes on grain yield and water use efficiency of maize under alternate partial rootzone irrigation

Faced with the scarcity of water resources and irrational fertilizer use,it is critical to supply plants with water and fertilizer in a coordinated pattern to improve yield with high water use efficiency(WUE).One such method,alternate partial root-zone irrigation(APRI),has been practiced worldwide,but there is limited information on the performance of different irrigation regimes and nitrogen(N)rates under APRI.The objectives of this study were to investigate the effects of varying irrigation regimes and N rates on shoot growth,grain yield and WUE of maize(Zea mays L.)grown under APRI in the Hexi Corridor area of Northwest China in 2014 and 2015.The three N rates were 100,200 and 300 kg N ha–1,designated N1,N2 and N3,respectively.The three irrigation regimes of 45–50%,60–65%and 75–80%field capacity(FC)throughout the maize growing season,designated W1,W2 and W3,respectively,were applied in combination with each N rate.The results showed that W2 and W3 significantly increased the plant height,stem diameter,crop growth rate,chlorophyll SPAD value,net photosynthetic rate(Pn),biomass,grain yield,ears per ha,kernels per cob,1000-kernel weight,harvest index,evapotranspiration and leaf area index(LAI)compared to W1 at each N rate.The N2 and N3 treatments increased those parameters compared to N1 in each irrigation treatment.Increasing the N rate from the N2 to N3 resulted in increased biomass and grain yield under W3 while it had no impact on those under the W1 and W2 treatments.The W3 N3 and W2 N2 and W2 N3 treatments achieved the greatest and the second-greatest biomass and grain yield,respectively.Increasing the N rate significantly enhanced the maximum LAI(LAI at the silking stage)and Pn under W3,suggesting that the interaction of irrigation and fertilizer N management can effectively improve leaf growth and development,and consequently provide high biomass and grain yield of maize.The W2 N2,W2 N3 and W3 N3 treatments attained the greatest WUE among all the treatments.Thus,either 60–65%FC coupled with 200–300 kg N ha–1 or 75–80%FC coupled with 300 kg N ha–1 is proposed as a better pattern of irrigation and nitrogen application with positive regulative effects on grain yield and WUE of maize under APRI in the Hexi Corridor area of Northwest China and other regions with similar environments.These results can provide a basis for indepth understanding of the mechanisms of grain yield and WUE to supply levels of water and nitrogen.

Heavy Metal Contaminated Food Crops Irrigated with Wastewater in Peri Urban Areas, Zambia

Studies on peri urban farming in Zambia have not adequately tackled the issues pertaining to heavy metal contaminated wastewater irrigation farming. The study investigated heavy metal contamination of water, soils and crops at two peri urban areas in Zambia. Two study sites were New Farm Extension in Mufulira Town in the Copperbelt Province and Chilumba Gardens in Kafue Town in Lusaka Province. The heavy metals investigated were lead, copper, cobalt, nickel and chromium. These heavy metals were found to be higher than acceptable limits in wastewater used to irrigate crops and there are potential human health risks associated with consumption of heavy metal contaminated food crops which have implications on the livelihoods of people. Samples of water, soil and crops were collected and analysed for lead (Pb), copper (Cu), chromium (Cr), cobalt (Co) and nickel (Ni) using the Atomic Absorption Spectrometer (AAS). The data on heavy metals was analysed using mean, standard error and T-test. The results indicated that the levels of heavy metals in wastewater, soil and food crops were above acceptable limits at two study sites. It can be concluded that there was heavy metal contamination of wastewater, soil and food crops at the two peri-urban areas in Zambia. The study highlighted the actual levels of heavy metal contaminant uptake in food crops consumed by the peri urban population. The information from this study can be used by the relevant authorities to develop appropriate measures for monitoring and control of heavy metal contamination in wastewater irrigation farming systems in peri urban areas inZambia.