[Comparison of Nitrogen and Phosphorus Uptake and Water Purification Ability of Five Submerged Macrophytes].

Uptake of nitrogen (N) and phosphorus (P) and their purification capacity for five native submerged macrophytes were investigated in laboratory simulated hydrostatic conditions,including Hydrilla verticillata,Vallisneria natans,Ceratophyllum demersum,Myriophyllum spicatum,Potamogeton maackianus.The results indicated that the moisture contents of different submerged macrophytes were almost the same before and after the test,with the range of 89.8%-92.0%.The net accumulated biomass changed from 1.52 g·m-2 to 12.92 g·m-2 among different submerged macrophytes,and the highest net accumulated biomass of Hydrilla verticillata was 8.5 times higher than the lowest plant of Potamogeton maackianus.The N and P contents of five submerged macrophytes ranged from 26.54 to 34.44g·kg-1 and from 2.54 to 4.01g·kg-1,respectively,and the N and P contents of Ceratophyllum demersum were relatively high.Total N and P removal efficiency of different submerged macrophyte treatments had ranges of 63.8%-83.1% and 49.2%-70.8%,significantly higher than those of the CK treatment (39.9% and 36.9%),respectively,and the removal efficiency decreased in the order of Hydrilla verticillata >Ceratophyllum demersum >Vallisneria natans >Myriophyllum spicatum >Potamogeton maackianus.Total N and P removal efficiencies of different submerged macrophyte treatments were significantly correlated with net accumulated biomass,with correlation coefficients of 0.994(P<0.01) and 0.996(P<0.01).The contribution of direct N and P uptake to different submerged macrophytes had the ranges of 1.5%-13.3% and 2.2%-13.2%,and the synergism contribution (deducting self-purification capacity of water) of different submerged macrophytes ranged 22.5%-29.9% and 10.1%-20.6%,indicating that the synergistic effect of submerged macrophytes purification was much more significant than the direct uptake effect in the process of water purification.

[Examining the effects of reduced nitrogen fertilization on the yield and fruit quality of greenhouse cultivated cucumber]. / 减量施氮对大棚黄瓜产量和品质的影响.

A long-term fertilizer experiment was conducted to determine the precise effects of nitrogen (N) fertilization on the yield and quality of cucumber, which were grown in greenhouse located in the coastal hilly region of East China. This work included four treatments with varying levels of chemical N application (N1, 800 kg·hm-2, N2, 600 kg·hm-2 and N3, 400 kg·hm-2, CK, no fertilization) plus ON (organic N 400 kg·hm-2). Results showed that a 50% reduction of N fertilization (N3) produced no significant effects on yield, when compared with the local conventional practice (N1). Importantly, fruit nitrate content for cucumbers with N fertilization ranged from 94.2 to 136.1 mg·kg-1, which was acceptable according to the National Food Safety Standard of China. However, when compared with no fertilization control, N fertilization increased nitrate content by 18.1%-44.5%. Chemical N fertilization resulted in a decrease of vitamin C, soluble sugar and soluble protein contents in cucumber, and caused significant temporary changes of soil pH and other chemical and physical properties of the soil. No significant correlations were found between cucumber yields, economic benefit and soil property variables under the excessive use of N fertilizer. It was concluded that N fertilization could be reduced by half with no significant reduction of fruit yield and quality for cucumbers cultivated in greenhouse located in the coastal hilly region of East China.

[Effects of sludge compost used as lawn medium on lawn growth and soil and water environment].

To address effect of the sludge compost-containing medium on the growth of Manila lawn and environment quality, a pot experiment was conducted using six treatments based on contrasting sludge compost addition volume ratios in the soil system (i. e., 0% , 10% , 25% , 50% , 75% and 100%). The results indicated that the growth potential of Manila lawn was increased with increasing sludge compost addition volume ratio. The content of Hg in Manila plant was significantly positively correlated with that in the lawn medium. Although the contents of Cr, Cd and Hg in the lawn medium were synchronously increased with increasing sludge compost addition volume ratio in the soil system, their contents were all lower than the critical levels of third-class standard in the National Soil Environmental Quality Standard. The heavy metal and nitrate concentrations detected in percolating water were significantly positively correlated with those in the lawn medium, respectively. When the sludge compost addition volume ratio was more than 50% in this study, both heavy metal and nitrate concentrations in percolating water would exceed the maximum allowable levels of the National Groundwater Environment Quality Standard.