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.

Effects of irrigation water salinity on soil salt content distribution,soil physical properties and water use efficiency of maize for seed production in arid Northwest China

In order to explore the use of groundwater resources,field experiments were conducted for three consecutive years during 2012-2014 in the Shiyang River basin of Northwest China.Irrigation was conducted using four different water salinity levels that were arranged in a split plot design.These four water salinity levels were s0,s3,s6 and s9(0.71,3,6 and 9 g/L,respectively).The soil salt content,soil bulk density,soil porosity,saturated hydraulic conductivity,plant height,leaf area index and yield of maize for seed production were measured for studying the effects of saline water irrigation on soil salt content distribution,soil physical properties and water use efficiency.It was observed that higher salinity level of irrigation water and long duration of saline water irrigation resulted in more salt accumulation.Compared to initial values,the soil salt accumulation in 0-100 cm soil layer after three years of experiments for s0,s3,s6 and s9 was 0.189 mg/cm3,0.654 mg/cm3,0.717 mg/cm3 and 1.135 mg/cm3,respectively.Both greater salt levels in the irrigation water and frequent saline water irrigation led to greater soil bulk density,but poorer soil porosity and less saturated hydraulic conductivity.The saturated hydraulic conductivity decreased with increase in soil bulk density,but increased with improvement in soil porosity.It was noted that the maize height,leaf area index and maize yield gradually decreased with increase in water salinity.The maize yield decreased over 25%and the water use efficiency also gradually declined when irrigated with water containing 6 g/L and 9 g/L salinity levels.However,maize yield following saline water irrigation with 3 g/L decreased less than 20%and the decline in water use efficiency was not significant during the three-year experiment period.The results demonstrate that irrigation with saline water at the level of 6 g/L and 9 g/L in the study area is not suitable,while saline water irrigation with 3 g/L would be acceptable for a short duration together with salt leaching through spring irrigation before sowing.

Cadmium removal mechanistic comparison of three Fe-based nanomaterials: Water-chemistry and roles of Fe dissolution

Cadmium(Cd)is a common toxic heavy metal in the environment.Taking Cd(II)as a target contaminant,we systematically compared the performances of three Fe-based nanomaterials(nano zero valent iron,nZVI;sulfidated nZVI,S-nZVI;and nano FeS,nFeS)for Cd immobilization under anaerobic conditions.Effects of nanomaterials doses,initial pH,co-existing ions,and humic acid(HA)were examined.Under identical conditions,at varied doses or initial pH,Cd(II)removal by three materials followed the order of S-nZVI>nFeS>nZVI.At pH 6,the Cd(II)removal within 24 hours for S-nZVI,nFeS,and nZVI(dose of 20 mg/L)were 93.50%,89.12%and 4.10%,respectively.The fast initial reaction rate of nZVI did not lead to a high removal capacity.The Cd removal was slightly impacted or even improved with co-existing ions(at 50 mg/L or 200 mg/L)or HA(at 2 mg/L or 20 mg/L).Characterization results revealed that nZVI immobilized Cd through coprecipitation,surface complexation,and reduction,whereas the mechanisms for sulfidated materials involved replacement,coprecipitation,and surface complexation,with replacement as the predominant reaction.A strong linear correlation between Cd(II)removal and Fe(II)dissolution was observed,and we proposed a novel pseudo-second-order kinetic model to simulate Fe(II)dissolution.