Jian Feng Zhang’s research while affiliated with Chinese Academy of Agricultural Sciences and other places

Phosphorus is the necessary element for plant growth, and its concentration is one of the main indices for water eutrophication. Hence, it is significant to understand how woody plants purify phosphorus in eutrophic water. The purpose of this study is to reveal the P absorption and removal mechanism of Salix matsudana in eutrophic water with different P concentration. We selected new S. matsudana clone (A42) as experimental material and set three levels of P concentration (low P: 0.1, 0.2 mg·L-1; medium P: 1.0, 2.0 mg·L-1, high P: 10.0 mg·L-1), and the floating bed hydroponic experiment was conducted at the greenhouse from July to September, 2017. We found that S. matsudana efficiently removed P in water (removal rate >79% in 21 days). There was a positive correlation between the removal quantity and P concentration in the water. The removal ratio rose at first and then fell with increasing P. Owing to the purification of S. matsudana, the P concentrations ranging from 0.1 mg·L-1 to 1.0 mg·L-1 were reduced to minimum threshold concentration of eutrophication (0.016-0.032 mg·L-1) in seven days. The percentage of phosphorus input in water that assimilated by S. matsudana ranged from 29.0% to 66.9%. The quantity and ratio of assimilated P were respectively positive and negative relation with P concentration. Salix matsudana adapted to eutrophic water with different P concentrations and normally grew during experiment period, with root-shoot ratio being significantly increased with decreases of water P concentrations. The characteristic of phosphorus distribution in plant organs was: stem> leave>root, while the translocation factors (TF) of nitrogen and phosphorus were both greater than 3. When S. matsudana grew in eutrophic water with high phosphorus concentration, the TF of nitrogen and phosphorus significantly increased to 4.53±0.24 and 4.92±0.62 respectively. Our results indicated that S. matsudanais could purify the eutrophic water and it could normally grow. New clone of S. matsudana could effectively absorb phosphorus in the water and accumulated it in the stem, which could reduce secondary pollution. In conclusion, S. matsudana could be used for a short-term treatment on the eutrophic water with low P concentration, while for the long-term treatment it is adapted to eutrophic water with high phosphorus concentrations.

A field experiment was conducted with sandy fluvo-aquic soil under wheat-maize rotation system during 2012 to 2016 in Henan Province, with four treatments: Chemical fertilizer (CK), composted sewage sludge (CS) 15 t·hm-2(CS1), 30 t·hm-2(CS2), 45 t·hm-2(CS3). We investigated the effects of CS on soil active organic nitrogen and its allocation ratio. Results showed that CS significantly enhanced soil water content, decreased soil pH, increased contents of soil organic carbon and total nitrogen (TN) and available nutrients. Soil TN was increased by 93.1%-284.3%. The CS3 treatment significantly improved the content of light fraction organic nitrogen (LFON), particulate organic nitrogen (PON) and microbial biomass nitrogen (MBN). CS treatments promoted the allocation of PON/TN and MBN/TN. with an enhancement of 12.3% and 539.9% in the CS2 treatment, respectively. The distributions of LFON/TN and DON/TN were decreased by 17.3%-40.1% and 38.5%-71.3%, respectively. The contribution of soil active organic nitrogen fractions to TN was: PON>LFON>DON>MBN. Results from the principal component analysis showed that organic nitrogen and their distribution had high load value in CS2 and CS3 treatments. Results from redundancy analysis showed that positive correlations existed between the soil physicochemistry, enzymatic activity and soil active organic nitrogen as well as their distribution. In summary, CS had positive impacts on soil organic matter, soil properties, and the formation of active organic nitrogen. The rates of 30 and 45 t·hm-2 CS application had significant effects on soil fertility, which could be an effective way to improve sandy fluvo-aquic soil quality.

In this study, through setting runoff plots in Chinese chestnut (Castanea mollissima) forest, the runoff water samples were collected and tested from January to October, 2013. Combining with soil nitrogen data before and after the rainy season, we analyzed the characteristics of soil nitrogen transportation in chestnut forest around the Fushi Reservoir watershed in north Zhejiang Province, China. The results showed that among the 10 surface runoff events of Chinese chestnut forest, there exhibited a significant difference in runoff water volume of each runoff plot, and the maximum amount was 0.51 m³. Nitrogen was the major element associated with nutrient loss in the study region. The concentrations of nitrate nitrogen (NO3⁻-N), ammonium nitrogen (NH⁴⁺-N), total nitrogen (TN) and chemical oxygen demend (CODMn) in the runoff water ranged from 0.02-1.87, 0.04-3.53, 1.69- 5.33 and 5.30-14.07 mg·L⁻¹, respectively. The water quality indexes were greatly affected by the runoff volume, and the relationship between the amount of nitrogen loss and runoff could be well fitted by using a linear equation. The difference in nitrogen contents of the soil in the upper, middle and lower part of the runoff plots was evident both before and after the rainy season. Moreover, the nitrogen content increased with the increasing altitude, but this trend decreased with increasing soil depth. Comparison of the difference between the four forms of soil nitrogen (NO3⁻-N, NH4⁺-N, TN and hydrolyzable nitrogen Hydro-N of soil) before and after the rainy season showed that there existed significant differences in Hydro-N and TN, and the average difference values were 20.21 and 307.49 mg·kg⁻¹, respectively. In this area, there was a great risk of nitrogen loss with runoff, and the potential non-point source pollution in Fushi Reservoir should be concerned.

In October 2015, soil samples with different salinity were collected in a coast area in Yuyao, Zhejiang, and soil microbial community composition, soil catalase, urease activities, as well as soil physical and chemical properties were studied. The results showed that Nitrospira took absolute advantage in the bacterial community, and showed good correlations to total potassium. Cladosporium and Fusarium were predominant in the fungal community. Meanwhile, Cladosporium was related to soil urease and total nitrogen, and same correlation was found between Fusarium and soil urease. Catalase activity ranged from 3.52 to 4.56 mL·g⁻¹, 3.08 to 4.61 mL·g⁻¹ and 5.81 to 6.91 mL·g⁻¹ for soils with heavy, medium and weak salinity, respectively. Catalase activity increased with the soil layer deepening, which was directly related to soil total potassium, and indirectly related to pH, organic matter, total nitrogen and total phosphorus through total potassium. Soil urease activity ranged among 0.04 to 0.52 mg·g⁻¹, 0.08 to 1.07 mg·g⁻¹ and 0.27 to 8.21 mg·g⁻¹ for each saline soil, respectively. Urease activity decreased with soil layer deepening which was directly related to soil total nitrogen, and was indirectly related to pH, organic matter and total potassium through total nitrogen. The total phosphorus was the largest effect factor on the bacterial community CCA ordination, and the urease was on fungal community.