[Nitrogen mineralization rate in different soil layers and its influence factors under plastic film mulched in Danjiangkou Reservoir area, China]. / ä¸¹æ±Ÿå£åº“åŒºè¦†è†œåœŸå£¤ä¸åŒåœŸå±‚æ°®ç´ çŸ¿åŒ–é€ŸçŽ‡åŠå ¶å½±å“å› ç´ .

The objective of this study was to investigate the rate of nitrogen mineralization in various soil layers (0-10, 10-20, and 20-30 cm) and its influencing factors under plastic film mulching ridge-furrow in a corn field of Wulongchi small watershed, Danjiangkou Reservoir Area. Results showed that the rate of soil ammonification decreased with soil depth during the entire maize growth period. The rate of nitrification in seedling, jointing, and heading stages decreased in the following order: 10-20 cm > 0-10 cm > 20-30 cm, while it increased with soil depth in maturation stage. The rate of soil nitrogen mineralization decreased with the increases in soil depth in the seedling, jointing and heading stages, whereas an opposite pattern was observed in maturation stage. Compared with non-filming, film mulching promoted the soil ammonification process in 0-10 cm and the soil nitrification and nitrogen mineralization processes in jointing, heading, and maturation stages in both 0-10 and 10-20 cm. However, the rates of soil nitrification and nitrogen mineralization under film mulching were much lower than those under non-filming in seedling stage. The stepwise regression analysis indicated that the main factors influencing soil nitrogen mineralization rate varied with soil depth. Soil moisture and total N content were the dominant controller for variation of soil nitrogen mineralization in 0-10 cm layer. Soil temperature, moisture, and total N content were dominant controller for that in 10-20 cm layer. Soil temperature drove the variation of soil nitrogen mineralization in 20-30 cm layer.

[Temporal variation of soil net nitrogen mineralization in summer maize growing period under plastic film mulched cultivation in Danjiangkou Reservoir Area, China.] / 丹江口库区覆膜耕作土壤净氮矿化随夏玉米生长期的变化.

Soil net nitrogen mineralization in cropland has a great influence on both agricultural non-point source pollution and soil nitrogen loss. A field plot experiment was conducted to explore the temporal variation of soil net nitrogen mineralization under plastic film mulching ridge-furrow in Wulongchi small watershed during summer maize growing period. Results showed that the soil net ammonification, nitrification, and nitrogen mineralization were significantly greater than those of non-mulched treatment, and the differences were 6.63, 12.96 and 19.59 mg·kg-1, respectively. During the summer maize growth period, the rate of soil net ammonification was high at seedling stage, low at heading stage, and high at maturation stage. Both the rates of soil net nitrification and nitrogen mineralization were high at jointing stage, low at heading stage, and high at maturation stage. The rate of soil net nitrogen mineralization under plastic film mulched had significant linear relation with the contents of soil total nitrogen, nitrate nitrogen, and soil water. In conclusion, the improved condition of soil water and temperature under plastic film mulched cultivation of summer maize in the growing period promoted soil net nitrogen mineralization.

[Effect of terracing project on temporal-spatial variation of non-point source pollution load in Hujiashan watershed, China]. / 坡改梯工程对胡家山小流域非点源污染负荷时空变化的影响.

Taking Hujiashan small watershed as the study area, based on the classified result of Landsat TM/ETM images of 2005, 2010 and 2015, combined with long-term field observation data, and used the export coefficient model, our study explored the effect of small watershed management project on temporal and spatial variation of total nitrogen (TN) load of non-point source pollution under the support of GIS technology. The results indicated that, due to the implementation of slope modification project, the area of cultivated land was significantly increased, while forest and bareland were decreased. The load of non-point source TN increased from 63208 kg in 2005 to 72778 kg in 2010, but reduced to 46876 kg in 2015. The contribution rate from residential areas was higher, the average contribution rate of the three periods was 53.5%, but it showed a decreasing trend year by year. The contribution rate of land use types was 45%, which showed an increasing trend year by year. The contribution rate of livestock was always low. From the spatial distribution, TN loading intensity was changed obviously after the terracing project. High load intensity zone was mainly concentrated on the slope of 5°-15° before terracing project. Nevertheless, high load intensity zone was concentrated on the slope of 15°-35° after terracing project, and 5°-8° had become a low load strength area. The TN load intensity changed little with time on the slope of 0°-8°, and it increased first and then decreased on the slope above 8°. With the treatment of sewage, garbage and livestock manure in rural areas, the output of nitrogen in the living and livestock breeding were significantly reduced. Due to the implementation of the project, the cultivated land area increased by 31%.

[Change of Soil Nitrogen Leaching with Summer Maize Growing Periods Under Plastic Film Mulched Cultivation in Danjiangkou Reservoir Area, China].

As an important form of agricultural non-point source pollution, soil nitrogen leaching deteriorates water quality. Compared with non-mulching cultivated land, field experiment explored the change characteristics of soil nitrogen leaching under plastic film mulching ridge-furrow in Wulongchi small watershed during summer maize growing period. The results showed that the amounts of mulching tillage soil TN and NO3--N leaching were significantly lower than those with non-mulched treatment, by 25.68% and 20.25%, respectively. With the advance of the summer maize growth period, leaching amount of mulched soil TN was highest at seedling stage, lowest at heading stage and higher in maturation period; leaching amount of mulched soil NO3--N was highest at seedling stage, lowest in maturation period; leaching amount of mulched soil NH4+-N was lower at seedling stage, increased to the peak at the jointing stage, decreased to the valley value at heading stage, and obviously increased in maturation period. Linear function relationship was found between mulched soil TN leaching and TN content, while exponential relationship was found between mulched soil NO3--N leaching and NO3--N content. In addition, there was linear function relationship of mulched soil TN and NO3--N leaching amount with soil moisture and rainfall. It was concluded that the plastic film mulched on summer maize could reduce the leaching loss of soil nitrogen, and it would have a significant effect on the reduction of reservoir area of agricultural non-point source pollution.

[Output characteristics of rainfall runoff phosphorus pollution from a typical small watershed in Yimeng mountainous area].

Relationships between phosphorus pollutant concentrations and precipitation-runoff were analyzed by monitoring pollutant losses at outlets of the Menglianggu watershed in 2010. A typical small watershed was selected to examine the runoff and quality parameters such as total phosphorus (TP), particle phosphorus (PP), dissolve phosphorus (DP) and dissolve inorganic phosphorus (DIP) in rainfall-runoff of 10 rainfall events. Precipitation was above 2 mm for all the 10 rainfall events. The results showed that the peak of phosphorus concentrations occurred before the peak of water flows, whereas change processes of the phosphorus fluxes were consistent with that of the water flows and the phosphorus flux also have a strong linear relationship with the water flows. The minimums of the phosphorus concentrations in every 10 natural rainfall events have small differences with each other, but the maximum and EMCs of the phosphorus concentrations have significant differences with each rainfall event. This was mainly influenced by the precipitation, maximum rainfall intensity and mean rainfall intensity (EMCs) and was less influenced by rainfall duration. DP and TP were mainly composed of DIP and PP, respectively. There were no significant correlations between DIP/DP dynamic changes and rainfall characteristics, whereas significant correlations between PP/TP dynamic changes and maximum rainfall intensity were detected. The production of DIP, DP, AND TP were mainly influenced by the direct runoff (DR) and base flow (BF). The EMCs of DIP, DP, TP and the variations of DIP/DP were all found to have significant polynomial relationships with DR/TR., but the dynamic changes of PP/ TP and the EMCS of PP were less influenced by the DR/TR.

[Impact of the land-use change on the non-point source nitrogen load in Yunmeng Lake watershed].

Take potable water sources in Linyi City Yunmeng Lake watershed as a case study, it obtains the nutrient export coefficient of land use by the export coefficient model and simulative rainfall experiment. On the basis of GIS and RS, it analyses the effect of the non-point source (NPS) pollution load because of the land-use change during the past 25 years. The result indicates that the TN increased from 3.77 x 10(3) t in 1986, to 4.45 x 10(3) t in 1995, to 5.5 x 10(3) t in 2010; As far as land-use type is concerned, the TN from farm-land increased year by year, the contribution rate is 80.11% in 1986, 82.60% in 1995 and 85.59% in 2010, the forestland and the grass-land load have a little change, but the contribution rate decreased gradually, the residential load increased by a large margin, however, the contribution rate is very little. As for the sub-basin, the higher the proportion of the farm-land is, the more the TN load increased. There is a significant positive correlation between the farm-land and the nitrogen (TN) load, so the farm-land is the sources of the nitrogen. Conversely, there are negative correlations between the forest-land, grass-land and the TN load; therefore, the forest-land and grass-land are the sinks of the nitrogen. Therefore, it can adjust the land-use structure to reduce and control the TN loss to water environmental pollution.

[Output characteristics of non-point phosphorus from a typical small watershed in Yimeng mountainous area under the special rainfall].

The relationships between pollutant concentrations and precipitation-runoff combined with the first and maximum intensity natural rainfall events were monitored at the outlets of the Menglianggu watershed in 2010. The results showed that dissolved organic phosphorus (DOP), dissolved inorganic phosphorus (DIP), total dissolved phosphorus (DP), total particle phosphorus (PP) and total phosphorus (TP) concentrations in the first rainfall were higher than those in the maximum intensity rainfall which was the largest average rainfall intensity, but the output of phosphorusin the first rainfall was all higher than that in the maximum intensity rainfall except dissolved organic phosphorus. The DOP, DIP, DP, PP and TP in two special rainfall events contributed 48%, 81%, 70%, 87% and 81% of the total output of rainy season. DP and TP were mainly composed by DIP and PP respectively. The two special rainfalls have the first flush effect and the maximum intensity rainfall was stronger than the first rainfall, so the analysis of M (V) curve showed that the priority should be given to the interception of corresponding phosphorus under special events. The regression analysis results showed that a linear relation existed between runoff and nutrient output, but there were some differences which the slope of the linear equation of the first rainfall was higher than that of the maximum intensity rainfall. Reducing agricultural practices such as tillage and fertilization during special rainfall period and building canals, ponds are effective ways for mitigating agricultural non-point source pollution.

[Soil and water losses and phosphorus output at the places between ridges in sloping peanut land under different planting modes in Yimeng mountainous area of Shandong Province, East China].

Taking the typical land use type, sloping Arachis hypogaea land, in Yimeng mountainous area of Shandong as study object, an in-situ fixed-point field experiment was conducted to study the characteristics of soil and water losses and phosphorus output at the places between ridges in the sloping land under different planting modes (Arachis hypogaea + Cynodon dactylon, I; A. hypogae + Melilotus officinalis, II; A. hypogaea + Lolium multiflorum, III; A. hypogaea + Trifolium repens, IV; A. hypogaea + blank control, V). Planting grasses at the places between ridges could effectively decrease the soil and water losses. The runoff was 55.1%-61.3% of the control, and decreased in the order of II > I > IV> III. The sediment loss was 3.4% -32.3% of the control, and decreased in the order of IV > II > I > 11. A. hypogaea + L. multiflorum was effective in storing water and retaining sediment. During the early period of planting L. multiflorum, the sediment loss was more affected by rainfall and presented a fluctuated variation, but in late period, the sediment loss decreased continuously and performed more stable, and accordingly, the sediment retention increased continuously. Planting grasses effectively decreased the output of phosphorus, with the decrease of total phosphorus (TP) output being 52.8%-75.3% of the control, and was in the order of I > II > IV > III. As compared with the control, planting grasses decreased 27.5% -67.0% of the output of particle phosphorus (PP), but relatively increased the output of dissolvable phosphorus (DP). A. hypogaea + L. multiflorum had the best effect in decreasing the output of phosphorus, with the outputs of TP and PP being 58.4% and 27.5% of the control, respectively. In the growth period of the vegetations, the losses of different phosphorus forms differed, and the dissolvable inorganic phosphorus was the main form of the output of DP during whole rain season. After the peanut harvested, the output of different phosphorus forms in the first rainfall was much higher than that in the maximum intensity rainfall.

[Vulnerability assessment of eco-environment in Yimeng mountainous area of Shandong Province based on SRP conceptual model].

Based on the ecological sensitivity-resilience-pressure (SRP) conceptual model, and selecting 13 indices including landscape diversity index, soil erosion, and elevation, etc. , the vulnerability of the eco-environment in Yimeng mountainous area of Shandong Province was assessed under the support of GIS and by using principal component analysis and hierarchy analytical method. According to the eco-environmental vulnerability index (EVI) values, the eco-environment vulnerability of study area was classified into 5 levels, i.e., slight (<1.8), light (1.8-2.8), moderate (2.8-3.5), heavy (3.5-4.0), and extreme vulnerability (>4.0). In the study area, moderately vulnerable area occupied 43.3% of the total, while the slightly, lightly, heavily, and extremely vulnerable areas occupied 6.1%, 33.8%, 15.9%, and 0.9%, respectively. The heavily and extremely vulnerable areas mainly located in the topographically complicated hilly area or the hill-plain ecotone with frequent human activities.

[Comparative study of N, P output and eutrophication risk in runoff water in cross ridge and longitudinal ridge].

Field in-situ rainfall simulation tests with two rainfall intensities (40 mm x h(-1) and 70 mm x h(-1)), which were conducted at typical sloping cropland in Yimeng mountainous area, were designed to analyze the output characteristics of dissolved inorganic nitrogen, Inorganic-N (NO3(-)-N, NH4(+) -N) and dissolved phosphorus (DP) in runoff water, as well as to compare the eutrophication risk in this water by calculating three ratios of Inorganic-N/DP, NO3(-) -N/DP, and NH4(+)-N/DP, respectively, in cross ridge and longitudinal ridge tillage methods. Results showed that, under the same rainfall intensity, the DP level in runoff water was higher in cross ridge than longitudinal ridge, while the change of different Inorganic-N level between the two tillage methods were not consistent. Cross ridge could effectively reduce runoff and the output rate of Inorganic-N and DP when compared to the longitudinal ridge tillage, which would be more outstanding with the increases of rainfall intensities. The losses of Inorganic-N and DP in runoff water were 43% and 5% less, respectively, in cross ridge than longitudinal ridge at the 40 mm x h(-1) rainfall intensity, and were 68% and 55%, respectively, at 70 mm x h(-1). The higher Inorganic-N/DP and NO3(-) -N/DP ratios suggest that runoff water from either cross ridge or longitudinal ridge tillage have a certain eutrophication risk, which present an increasing trend during the precipitation-runoff process. Compared with longitudinal ridge, cross ridge can not only hinder the increasing trend of eutrophication risk, but also can significantly lower it, and thus effectively reduce the effect of sloping cropland runoff on the eutrophication processes of receiving waters.