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The overapplication of nitrogen to wheat reduces profits and has adverse environmental consequences. Machine learning techniques are employed to identify the factors that hold the most potential in improving nitrogen recommendations. The database used in our analysis consisted of a formula fertilization project, the second soil census of China, and cultivated land fertility evaluation. The results showed that the wheat nitrogen yield response was mainly concentrated around 1300–2400 kg/ha in Henan Province, with the highest values observed in the southern and eastern regions and the lowest in the northern region. The soil nitrogen content, nitrogen fertilizer, wet nitrogen deposition, dry nitrogen deposition, and soil nitrogen supply capacity were mainly concentrated around 0.65–1.30 g/kg, 173–203 kg N/ha, 15–39 kg N/(ha yr), 7–49 kg N/(ha yr), and 105–150 kg N/ha, respectively. When comparing the spatial distribution of the soil nitrogen content, nitrogen fertilizer, and nitrogen deposition, we found that the soil nitrogen supply capacity emerged as the predominant factor controlling wheat grain production. Soil types, precipitation, and temperature demonstrated a notable positive correlation with the soil nitrogen supply capacity. Given this background, it would be unreasonable to rely solely on the soil nitrogen content as the standard for fertilizer management. Particularly in high-yield fields, our focus should be on preserving optimal soil fertility by placing greater emphasis on the soil nitrogen supply capacity rather than simply reducing fertilizer application during wheat growth. [ABSTRACT FROM AUTHOR]

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This paper aims at assessing the effect of land use on nitrogen flows from a significant land-use area in the Chi River basin (Maha Sarakham region) in Thailand. The Chi River is one of the main rivers, and many land use categories affect the quality of the river. Statistical data and referred data was collected as the secondary data from credible sources to identify the flows. The data show a strong effect of land use on nitrogen with the highest load dominated by paddy field (66,597.51 tonne/year), and the lowest value in the community (1,005.71 tonne/year). Nitrogen flow increased with the fertilizer application in paddy field and farm plants (34,834.07 tonne/year). Paddy field discharged nitrogen to the Chi River 47 tonne/year in form of surface runoff. Also, the community without wastewater collection system takes part in a non-point source (NPS) of nitrogen to the Chi River at 299 tonne/year. The management's suggestion is to control fertilizer application, burning of agricultural residue such as rice straw, and wastewater treatment before disposal. [ABSTRACT FROM AUTHOR]

【Objective】Analysis of nitrogen fertilizer efficiency and yield of six high-quality conventional rice varieties at different nitrogen applications was conducted. It provides theoretical basis for the production selection of nitrogen-efficient varieties of high-quality rice and reasonable reduction of nitrogen fertilizer application.【Method】The test varieties are Guixiang 18,Guiyu 12,Guiyu 9,Guiyu 11,Guiyu 18 and Guiyu 8.The control variety is Liushayouzhan 202. Set four nitrogen fertilizer application levels:0（no nitrogen）,112.5（low-medium nitrogen）,150（conventional nitrogen） and 187.5（high nitrogen） kg/hm2(The treatment sequences are N0,N7.5,N10.0 and N12.5).Determination and analysis on the nitrogen utilization of each varieties by measuring physiological efficiency（PE）,agronomic efficiency（AE）,recovery efficiency（RE）,partial factor productivity（PFP）, and yield difference was compared and nitrogen efficiency was evaluated.【Result】The physiological efficiency and agronomic efficiency of nitrogen fertilizer of six high quality conventional rice varieties were the highest under N7.5 and all of them were significantly higher than N12.5（P<0.05,the same as below）.There was no significant difference in the recovery efficiency of nitrogen fertilizer of Guiyu 12,Guiyu 11,and Guiyu 18 among various nitrogen applications（P>0.05,the same as below）.The recovery efficiency of nitrogen fertilizer of Guixiang 18,Guiyu 9 and Guiyu8 were the highest at N10.0,N7.5 and N12.5.The partial factor productivity of nitrogen fertilizer of tested varieties decreased significantly with the increase of nitrogen application. There was no significant difference in yield at N7.5,N10.0 and N12.5 of Guixiang 18,Guiyu 12,Guiyu 9 and Guiyu 11. The yield of Guiyu 18 and Guiyu 8 were significantly higher than that when N7.5 compared to N12.5.The yield of six high-quality conventional rice varieties at N7.5 were significantly higher than that of CK.It is higher than that of CK under treatment of N10.0 and N12.5. It showed that the yield of these 6 varieties could be maintained under the condition of 25 % reduction of nitrogen application.Grains per spike,filled-grain percentage and 1000-grain weight of six high-quality conventional rice varieties are no significantly different at N7.5,N10.0 and N12.5.There was no significant difference in the effective spike of Guixiang 18,Guiyu 12,Guiyu 11 and Guiyu 8 at N7.5,N10.0 and N12.5.The effective spike of Guiyu 9 was not significantly different between N7.5 and N10.0.The effective spike number of Guiyu 18 was not significantly different between N7.5 and N12.5.The effective spike of CK increased significantly with the increase of nitrogen application.The effective spike of these six varieties remained high at low nitrogen level(N7.5),which was the main reason for the high yield at reduced nitrogen application.【Conclusion】The yield of six varieties of high quality conventional rice in Guangxi at low nitrogen level（nitrogen application 112.5 kg/hm2） can reach or exceed the yield at the level of normal nitrogen（nitrogen application 150 kg/hm2） and high nitrogen（nitrogen application 187.5 kg/hm2）,and it is significantly higher than the yield of the control varieties in the Guangxi regional test with the same ripening group under normal nitrogen application. These varieties are nitrogen-efficient varieties that meet the yield requirements of nitrogen-efficient varieties in production promotion. [ABSTRACT FROM AUTHOR]

The Liaohe Delta region, one of the main commodity grain production bases in northeast China, has better temperature and light conditions for paddy rice with higher yields and good taste. However, it is common for local farmers to use up to 270~300 kg N·hm-2 to increase rice grain yield. In the present study, the optimal nitrogen fertilizer application rate（ONR）in this area was determined based on a long-term field experiment with treatments comprising different nitrogen application rates（pure nitrogen 0~420 kg·hm-2）in 2012, 2014, 2016, and 2018. Both yield-response curve and rice-soil nitrogen balance analysis methods were adopted to obtain the ONR. The results showed that ONR for rice planting in Liaohe Delta was determined to be 217 kg·hm-2 via the yield-response curve method and 221~235 kg·hm-2 based on the rice-soil nitrogen balance method. Moreover, the maximal nitrogen use efficiency varied from 36% to 43% with nitrogen application rates ranging from 210 kg·hm-2 to 260 kg·hm-2. Based on a combination of the factors affecting the nitrogen use efficiency of rice, rice target yield and rice-soil nitrogen balance, the ONR for rice planting in Liaohe Delta was finally determined to be 217~235 kg· hm-2,which was 13%~28% lower than the amount conventionally used by local farmers. This study provides a practical theoretical basis for reducing nitrogen surplus for rice planting in Liaohe Delta on the premise of guaranteeing grain yield of rice and is also helpful for reducing the risk of nitrogen leaching to both local soil and underground water. [ABSTRACT FROM AUTHOR]

The garlic (Allium sativum L.) planting in Guanzhong plain of Shaanxi Province has a common problem of excessive application of nitrogen fertilizers. Establishing model of critical nitrogen concentration dilution curve is an effective approach to assess nitrogen status and optimize nitrogen management in garlic production. Based on 2-year field experiments, the model of critical nitrogen concentration dilution curve was constructed for 2 representative garlic varieties‘Cangshan’and‘Gailiangsuan’in local area. In 2015-2016, the experiment was carried out in the Institute of Water Saving Agriculture in Arid Areas of China, Northwest A&F University, Yangling, Shaanxi province, Northwest China (108°5 ′ E、34°19 ′ N); In 2016-2017, the experiment was carried out in Jintiezhai village of Wugong county, Shaanxi province, Northwest China, (108°16 ′ E、34°15 ′N). The experiment was conducted with 6 nitrogen levels: 0 (N0), 60 (N60), 120 (N120), 180 (N180), 240 (N240), 300 (N300) kg/hm². In 2017-2018, the experiment was also conducted in the Institute of Water Saving Agriculture in Arid Areas for model validation. The plant samples of different treatments were collected 5 times during the study periods, i.e., 15, 30, 40, 50, 70 (or 73) d respectively after garlic returning green in spring. Aboveground dry matter, nitrogen concentration and yield of garlic were determined. With the analysis of critical nitrogen concentration and maximum dry matter in each sample date, the results showed that there existed a negative power function between aboveground maximum dry matter and critical nitrogen concentration of garlic. Using the observed maximum and minimum nitrogen concentration at each sampling date, 2 boundary curves were also determined. With the validation of independent test, the normalized root mean square error of‘Cangshan’and ‘Gailiangsuan’were 9.37% and 7.75%, respectively. It indicated that the simulation performance of these models were proven to be excellent. The nitrogen nutrition index (NNI) calculated based on critical nitrogen concentration dilution curve could directly reflect the real- time nitrogen nutrition status of garlic. The NNI values of N240 treatment varied around 1 in 2-year experiment for 2 garlic varieties, meanwhile this treatment can also obtain the maximum relative yields of garlic scape and bulb. Moreover, the NNI values of N300 treatment were greater than 1, which suggested that the nitrogen concentration in N300 treatment was excessive, resulting in the waste of nitrogen fertilizer. The NNI of 2 garlic varieties were both increased gradually with the raise of nitrogen application level in this study. With the nitrogen level lower than or equal to N240, the significant correlations between the NNI and aboveground dry matters, relative yields of garlic scape and bulb were found. According to the change of NNI value under different nitrogen levels, we suggested the appropriate nitrogen application rate of 240 kg/hm² for 2 local garlic varieties in this area. [ABSTRACT FROM AUTHOR]

Although nitrogen (N) has the highest requirement for plant growth, N use efficiency (NUE) seldom exceeds 40%. NUE may be improved by integrated application of fertilizer N and enriched organic amendments. The present experiment aimed to test the extent of increase in NUE by integrated application of fertilizer N farmyard manure (FYM) and rock phosphate enriched compost (RPEC). Mineralization kinetics and N release from FYM and RPEC were studied by an incubation experiment. Results revealed that maximum potentially mineralizable N as well as N release (283.9, 186.7 mg kg−1 soil, respectively) were from RPEC + fertilizer N treated soils, followed by FYM + fertilizer N. Maximum yield, N uptake, and N recovery were obtained from RPEC + fertilizer N treated soils followed by FYM + fertilizer N. Soils treated with RPEC had shown significantly higher dehydrogenase activity than FYM treated soils. Thus, RPEC might increase yield as well as NUE over FYM. N uptake by plant at maximum tillering stage and flowering stage of wheat correlated positively (R2 > 0.85) with the decay rate (k and kN0) parameter of incubation experiment suggesting their relevance as indicators of plant available N. [ABSTRACT FROM AUTHOR]

We investigated how the initial age structure of a managed, middle boreal (62°N), Norway spruce-dominated ( Picea abies L. Karst.) forest area affects the net climate impact of using forest biomass for energy. The model-based analysis used a gap-type forest ecosystem model linked to a life cycle assessment (LCA) tool. The net climate impact of energy biomass refers to the difference in annual net CO exchange between the biosystem using forest biomass (logging residues from final felling) and the fossil (reference) system using coal. In the simulations over the 80-year period, the alternative initial age structures of the forest areas were (i) skewed to the right (dominated by young stands), (ii) normally distributed (dominated by middle-aged stands), (iii) skewed to the left (dominated by mature stands), and (iv) evenly distributed (same share of different age classes). The effects of management on net climate impacts were studied using current recommendations as a baseline with a fixed rotation period of 80 years. In alternative management scenarios, the volume of the growing stock was maintained 20% higher over the rotation compared to the baseline, and/or nitrogen fertilization was used to enhance carbon sequestration. According to the results, the initial age structure of the forest area affected largely the net climate impact of using energy biomass over time. An initially right-skewed age structure produced the highest climate benefits over the 80-year simulation period, in contrast to the left-skewed age structure. Furthermore, management that enhanced carbon sequestration increased the potential of energy biomass to replace coal, reducing CO emissions and enhancing climate change mitigation. [ABSTRACT FROM AUTHOR]

Human drivers are often proposed to be stronger than biophysical drivers in influencing ecosystem structure and function in highly urbanized areas. In residential land cover, private yards are influenced by individual homeowner preferences and actions while also experiencing large-scale human and biophysical drivers. We studied plant nitrogen (%N) and N stable isotopic composition (δN) in residential yards and paired native ecosystems in seven cities across the US that span major ecological biomes and climatic regions: Baltimore, Boston, Los Angeles, Miami, Minneapolis-St. Paul, Phoenix, and Salt Lake City. We found that residential lawns in three cities had enriched plant δN ( P < 0.03) and in six cities higher plant N (%) relative to the associated native ecosystems ( P < 0.05). Plant δN was progressively depleted across a gradient of urban density classes in Baltimore and Boston ( P < 0.05). Lawn fertilization was associated with depleted plant δN in Boston and Los Angeles ( P < 0.05), and organic fertilizer additions were associated with enriched plant δN in Los Angeles and Salt Lake City ( P < 0.04). Plant δN was significantly enriched as a function of housing age in Baltimore ( r = 0.27, P < 0.02), Boston ( r = 0.27, P < 0.01), and Los Angeles ( r = 0.34, P < 0.01). These patterns in plant δN and plant N (%) across these cities suggests that N sources to lawns, as well as greater rates of N cycling combined with subsequent N losses, may be important drivers of plant N dynamics in lawn ecosystems at the national scale. [ABSTRACT FROM AUTHOR]

Environmental changes are expected to shift the distribution of functional trait values in plant communities through a combination of species turnover and intraspecific variation. The strength of these shifts may depend on the availability of individuals with trait values adapted to new environmental conditions, represented by the functional diversity (FD) of existing community residents or dispersal from the regional species pool. We conducted a 3-year nutrient- and seed-addition experiment in old-field plant communities to examine the contributions of species turnover and intraspecific variation to community trait shifts, focusing on four key plant functional traits: vegetative height, leaf area, specific leaf area (SLA), and leaf dry matter content (LDMC). We further examined the influence of initial FD and seed availability on the strength of these shifts. Community mean height, leaf area, and SLA increased in response to fertilization, and these shifts were driven almost entirely by intraspecific variation. The strength of intraspecific shifts in height and leaf area was positively related to initial intraspecific FD in these traits. Intraspecific trait responses to fertilization varied among species, with species of short stature displaying stronger shifts in SLA and LDMC but weaker shifts in leaf area. Trait shifts due to species turnover were generally weak and opposed intraspecific responses. Seed addition altered community taxonomic composition but had little effect on community trait shifts. These results highlight the importance of intraspecific variation for short-term community functional responses and demonstrate that the strength of these responses may be mediated by community FD. [ABSTRACT FROM AUTHOR]

Rapid socio-economic development in suburban areas of developing countries has induced changes in agricultural waste and nutrient management, resulting in water pollution. The study aimed at estimating agricultural nutrient cycles and their contribution to the water environment. A material flow model of nitrogen (N) and phosphorus (P) was developed focusing on agricultural activities from 1980 to 2010 in Trai hamlet, an agricultural watershed in Nhue-Day River basin, Vietnam. The model focused on the change in household management of human excreta and livestock excreta, and chemical fertilizer consumption. The results showed that the proportion of nutrients from compost/ manure applied to paddy fields decreased from 85 to 41% for both N and P between 1980 and 2010. The nutrient inputs derived from chemical fertilizer decreased 6% between 1980 and 2000 for both N and P. Then, these nutrients increased 1.4 times for N and 1.2 times for P from 2000 to 2010. As of 2010, the total inputs to paddy fields have amounted to 435 kg-N/ha/year and 90 kg-P/ha/year. Of these nutrient inputs, 40% of N and 65% of P were derived from chemical fertilizer. Thirty per cent (30%) of total N input was discharged to the water bodies through agricultural runoff and 47% of total P input accumulated in soil. [ABSTRACT FROM AUTHOR]

Macro- and micro nutrients were managed in soil and mulberry foliage through application of urea and diammonium phosphate (DAP). Urea at the rate of 608 kg/ha and DAP at the rate of 260 kg/ha was applied on six mulberry varieties. The results showed a deficiency in nitrogen, phosphorus, zinc and manganese in soil before the fertilizer application. Contrarily, high copper and potassium contents were found. After three weeks of fertilizer application, concentration of N, P, K and Fe in the soil almost doubled. Zinc and Cu contents decreased significantly (p<0.01). The highest N, P and K were found in mulberry variety PFI-1, M. latifolia and Karyansuban, respectively. The highest Cu and Mn were found in Kanmasi. The highest Zn and Fe were found in Husang and Karyansuban, respectively. A significant variation in uptake and retention of macro- and micro nutrients was found in the mulberry varieties after fertilizer application. The highest N was taken up by Kanmasi, while the highest P and K were taken up by Husang. Iron and Cu increased, and Zn and Mn decreased after week 3 of fertilizer application. Nitrogen was 1.5 to 2.6 times greater after week 6 of fertilizer application compared to before fertilizer application. Similarly, P and K were 4.7 to 6.6 times and 2.6 to 3.9 times greater, respectively. Based on these findings, it is concluded that urea in split doses and diammonium phosphate in single dose should be applied 3-4 weeks before the commencement of rearing of Mulberry Silkworm Moth for nutritionally rich mulberry foliage. Ghulam Ali Bajwa*, Muhammad Arshad Khan [ABSTRACT FROM AUTHOR]

The leaching of nitrogen in farmland could lead to groundwater nitrogen pollution, while precipitation is the driving factor. Nevertheless, the influences of extreme precipitation on soil organic nitrogen leaching, such as urea, is not clear. In this study, we used soil column experimental data to construct a nitrogen migration and transformation model. The constructed model was applied to unsaturated zones in farmlands in the Dagu River Basin of China. Three rainfall scenarios, namely rainstorms, heavy rainstorms, and extreme rainstorms, were simulated to analyze the variation in urea nitrogen leaching to groundwater. As the rainfall intensity increased, the quantity of urea nitrogen leaching increased from 0.04% to 18.09%. The cumulative urea nitrogen leaching flux is related to the initial soil moisture content. The time interval between fertilization inversely influenced the urea nitrogen leaching flux. Applying urea-based fertilizers shortly before high-intensity rainfall significantly increases the soil-crop system urea leaching loss and decreases crop nitrogen utilization. These findings imply that urea leaching under extreme rainstorms should not be ignored, and based on weather forecasting, fertilizer application in farmland should be avoided before high-intensity rainfall. • Numerical model is a useful tool for evaluating accumulated nitrogen leaching flux and nitrogen balance in the unsaturated zone. • The urea nitrogen leaching flux increase with the rainfall intensity increase, and the nitrogen use efficiencydecrease. • Under extreme rainstorms, 18.5% of urea nitrogen can leach to groundwater without hydrolysis. • The urea leaching flux was affected by the initial soil moisture and the time interval between fertilization and rainfall. [ABSTRACT FROM AUTHOR]

• Nitrogen use efficiency (NUE) varies considerably in space and time in China. • Partial factor productivity of nitrogen was large in north- and south-east China. • Partial nutrient balance of nitrogen was low in south China. • Multiple linear regression explained 74 % of the NUE variation. • Crop type, soil properties and climate are major explanatory variables of NUE. Nitrogen use efficiency (NUE) is crucial to establish efficient fertilizer application guidelines that balance crop yield, economic return and environmental sustainability. Although there are quite a few researches about the spatial and temporal variation of NUE, little work has been done on modelling NUE through deriving empirical relationships with explanatory environmental variables and exploring their relative importance quantitatively. The space-time patterns of NUE indicators (i.e., the Partial Factor Productivity of nitrogen, PFP N , and the Partial Nutrient Balance of nitrogen, PNB N) at provincial scale in China were derived and related to environmental covariates using stepwise multiple linear regression. PFP N was higher in east and south China than in central and west China and was smaller than 30 kg kg−1 yr−1 in most provinces, while PNB N was moderate in most provinces (0.41–0.50 kg kg−1 yr−1) and low (< 0.40 kg kg−1 yr−1) in south China. The national PFP N declined slightly from 32 kg kg−1 in 1978 to 27 kg kg−1 in 1995 and went up gradually to reach 38 kg kg−1 in 2015. The national PNB N decreased from 0.53 to 0.36 kg kg−1 from 1978 to 2003, thereafter stabilizing at around 0.40 kg kg−1 yr−1 between 2004 and 2015. The multiple linear regression models explained 74 % of the variance of PFP N and PNB N. The main explanatory variables of PFP N were planting area index of sugar crop (32 % of the R-square), followed by Arenosols (12 %), planting area index of oil crop (8 %), planting area index of vegetables (5 %), silt content (5 %) and total potassium (5 %). For PNB N , the variation was mainly attributed to mean annual daytime surface temperature (28 % of the R-square), planting area index of crops (beans 20 %, orchards 10 % and vegetables 9 %) and wet day frequency (5 %). The results of this study indicate that crop types, temperature and soil properties are important variables that determine NUE. These should be considered by policy makers when agricultural land development decisions are made in order to balance NUE and productivity (i.e., agronomy and environment). [ABSTRACT FROM AUTHOR]