Effects of Different Nitrogen Applications on Soil Physical, Chemical Properties and Yield in Maize (<i>Zea mays</i>L.)

Application of nitrogen (N) fertilizer is one of the most important approaches on improving maize grain yield. However, as is known to all, overuse N fertilizer not only leads to decline of N use efficiency and maize yield, but also leads to potential risk to environment pollution. This experiment was conducted to determine the effects of N fertilizer applications with nine different treatments on soil physical-chemical characters and maize grain yield using hybrid variety Zhengdan 958 in 2011 and 2012. Results indicated that the soil bulk densities of T2 (CK) and T1 were the lowest compared to other treatments in 2011 and 2012, respectively, whereas the soil bulk density of T5 in 2011 and T3 in 2012 were higher than other treatments. The soil porosity and field capacity of T5 in 2011 and T3 in 2012 were lower than other treatments, but those of CK in 2011 and T1 in 2012 were higher than other treatments. The pH values of T3 to T7 were lower than other treatments. These results indicated that the soil bulk densities were increased, whereas the soil porosity, field capacity and values pH were decreased by N application at different stages. N application could increase the N contents of leaf and stem, whereas less or excess N application should not significant improve maize yield. Although the soil organic matter and total N contents of T3 were the highest in both 2011 and 2012, the yield of T4 is the highest in both 2011 and 2012. The application amount, period and times of N fertilizer were important to maize yield.

Effect of Potassium Deficiency on Root Growth and Nutrient Uptake in Maize (Zea mays L.)

Potassium (K) is an essential nutrient on the growth and development for maize (Zea Mays L.). And the developed root morphology and root activity have great significance to nutrient absorption and play an important role in the growth and development of plants. To explore the response to K-deficiency on root growth and nutrient absorption of maize, two inbred lines, 90-21-3 (Tolerance to K deficiency) and D937 (Sensitive to K deficiency) were carried out to investigate the root morphology, root activity, nutrient uptake and related traits. The results showed that K-deficiency inhibited the root growth of 90-21-3 and D937, but increased the ratio of root to shoot (R/S). The total length, root surface area, the root diameter and root volume of root system of 90-21-3 and D937 were significantly decreased by K deficiency, especially the fine root (0 - 0.4 mm) in root length and root surface area. In addition, the K concentration of root in the two lines was significantly decreased, but root activity was significantly improved, which promoted the absorption of the root system to Na+. Compared with D937, 90-21-3 was able to distribute more carbohydrates from shoot to the root system under K deficiency, alleviating the inhibition of root growth. The fine root system was the main part for absorption nutrient. The length and surface area of 90-12-3 were no difference, and significantly decreased by 12.90% and 17.65% in D937 after 5 d of K deficiency. As well, the root activity of 90-21-3 was significantly increased when encountered to K deficiency, which promoted the accumulation of Na+ and Ca2+ and regulated the osmotic stress. Therefore, it could be a responding mechanism for tolerance crop by maintaining large root system, increasing root activity and adjusting nutrient absorption to adapt to K deficiency.

Multi-functional polyethersulfone nanofibrous membranes with ultra-high adsorption capacity and ultra-fast removal rates for dyes and bacteria

The adsorption technology has been widely applied in water remediation for contamination removal of dyes and bacteria,by virtue of the advantages of adsorption technology including high efficiency,energy conservation and ease of operation.Simultaneous removal of dyes and bacteria has been realized by some reported materials,but to achieve satisfactory adsorption amounts and rates remain an unmet goal for decades.Herein,a poly(methacrylatoethyl trimethyl ammonium chloride-co-methyl methacrylate)copolymer was synthesized,and then blended with polyethersulfone for the fabrication of nanofibrous membranes via electrospinning for the use of fast and massive removal of dyes and bacteria.Owing to the introduction of abundant quaternary ammonium groups,the maximum adsorption amount for methyl orange was up to 909.8 mg g^(-1).In addition,the modified nanofibrous membranes showed good recyclability,broad applications in severe environments,selective adsorption ability,and excellent dynamic removal performance.Especially,thanks to the abundant functional groups,the membranes showed fast adsorption ability for bacteria through electrostatic interaction.It should be noted that the clearance ratio for Staphylococcus aureus or Escherichia coli by 6 min of static adsorption could reach 93%or 90%for each.Additionally,dynamic removal ratio via filtration with the nanofibrous membranes could reach 99.7%for Staphylococcus aureus or 98.7%for Escherichia coli in 90 s.Therefore,the proposed approach towards the quaternary ammonium modified polyethersulfone nanofibrous membranes creates a new route for ultra-high adsorption capacity and ultra-fast removal rates for dyes and bacteria in water remediation.