Optimization of reduced chemical fertilizer use in tea gardens based on the assessment of related environmental and economic benefits.

Chemical fertilizer application is the primary method used to maintain tea yield and quality, but has a negative environmental impact owing to its excessive use. This study sought to assess the environmental and economic benefits of three different chemical fertilizer reduction modes: Single reduction of chemical fertilizer (SRCF), combined application of organic and chemical fertilizer (CAOF), and controlled-release fertilizer substitute (CRFS). Differences in soil nutrient content, NP (NH4+-N, NO3-N and total P) runoff loss, tea yield and quality, and the revenue of tea planting across different fertilizer reduction treatments were then discussed. We also analyzed the coupling effects of these different fertilization modes, fertilization rate and time on soil NP runoff loss, which allowed us to determine the optimum fertilization method based on differences in their respective environmental and economic benefits. Our results revealed differences in soil nutrient content, tea yield and quality, NP runoff loss, and revenue owing to tea planting across the different fertilization treatments. Soil pH after fertilization was significantly lower than before fertilization. CAOF was beneficial and improved soil nutrients as well as tea yield and quality. Of the tested methods, 50% combined application of organic and chemical fertilizer (CAOF2) was the best, as it resulted in the best tea quality and yield. CAOF2 also had the highest revenue. In addition, it was beneficial in reducing NP runoff loss. CRFS was advantageous in its persistent fertilizer efficiency and reduction in NP runoff loss. With CAOF, NP runoff loss was primarily caused by quick-acting chemical fertilizer. With extended time, NP runoff loss caused by fertilization was gradually decreased. Given our analysis of the environmental and economic benefits of different fertilizer reduction methods, CAOF2 emerged in this study as the best fertilizer reduction treatment option.

China's cement demand and CO2 emissions toward 2030: from the perspective of socioeconomic, technology and population.

China is the largest cement producer and carbon dioxide (CO2) emitter in the world. The country has attracted too much attention in calculating and comparing its CO2 emissions. However, as the second largest CO2 emitter after the fire power industry, China's long-term cement demand and cement-related CO2 emission projections were not fully studied. The Chinese government, however, committed that by 2020 and 2030, China's per capita GDP of CO2 emissions would be lower than that in 2005 by 40-45% and 60-65%, respectively. In this paper, China's cement demand in 2030 was projected based on the population size, urbanization rate, fixed assets investment, and per capita GDP. Furthermore, decoupling study in China's cement industry was also involved based on the GDP and CO2 emissions during 2001-2015. We also used the diffusion rate of 12 types of CO2 reduction measures and two changed scenarios of clinker-to-cement ratio, to project the cement CO2 emission factors toward 2030 after determining the accounting scope. Meanwhile, the CO2 emissions of China's cement industry through 2030 were projected naturally. The results showed that China's cement output in 2030 will be approximately 2000, 1650, and 937 Mt. based on the fixed assets investment, urbanization rate, and per capita GDP respectively. The projected two scenarios cement CO2 emission factors were resp. 407.83 and 390.02 kg CO2/t of cement which were 42.6 and 45.1% lower than that in 2005. The cement CO2 emissions were projected to be in the range of 366 to 818 Mt. in 2030. Additionally, China's total cement output value has been decoupling from cement CO2 emissions from 2012, which is mainly attributed to eliminating backward capacity, reducing excess capacity or the declining cement output. And decoupling economic from China's cement CO2 emissions may change to be strong or weak decoupling in the near future. As cement production is one of the factors effecting cement CO2 emissions, the most important measure for controlling cement CO2 emissions is a reasonable capacity utilization rate. It is therefore important to control the growth of cement CO2 emissions by regulating the capacity utilization rate within a reasonable range. Eliminating backward capacity, removing excess capacity, controlling new capacity, staggered production, and the "going global" of cement equipment can have great impacts in controlling the total amount of cement output and CO2 emissions.

Does dual reduction in chemical fertilizer and pesticides improve nutrient loss and tea yield and quality? A pilot study in a green tea garden in Shaoxing, Zhejiang Province, China.

Tea tree (Camellia sinensis) is a valuable and popular cash crop widely planted in tropical and subtropical areas of China. To increase tea yield and quality, high rates of chemical fertilizer and pesticide application have generally been used; however, increasing usage of fertilizers and pesticides does not always proportionally increase tea yield. Indeed, excessive nutrient inputs may cause serious agricultural non-point source pollution. A pilot study on dual reduction in fertilizers and pesticides was conducted in a green tea plantation in Shaoxing, Zhejiang Province, to explore the environmental effects of different fertilizer and pesticide managements (e.g., changes in soil properties and nutrient accumulation, nutrient inputs in runoff water) and to reveal the potential effects of the interaction of these two managements on tea yield and quality. Traditional formulas and rates of chemical fertilizers and pesticides were used as the baselines (100% usage); replacement with different proportions of organic fertilizer (i.e., 20%, 50% and 80%) and direct pesticide reductions of 30%, 50%, and 80% were tested. The results showed that proper management with organic fertilizer replacement can effectively mitigate soil acidification and nutrient deficiency in tea plantations, increase soil organic matter (OM) and ammonium nitrogen (NH4-N) contents, and promote tea yield and quality. Moreover, managements with organic fertilizer replacement can markedly reduce the inputs of ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N), total phosphorus (TP), and total potassium (TK) in runoff water. Soil nutrient accumulation was the highest while the runoff nutrient input was the lowest at 20% organic fertilizer replacement. Experimental spraying of bifenthrin and chlorfenapyr revealed that these pesticides were mainly trapped by the tea leaves and rarely entered the soil or water bodies. Although pesticide reduction treatments can effectively decrease pesticide residues in tea leaves, differences in pesticide residue between various treatments were not obvious due to the rapid degradation of pesticides. Multivariate analysis of variance showed that 50% of the variation in tea yield, bud density, polyphenols, and caffeine can be explained by interactions between fertilizers and pesticides. Combinations of 20% or 50% organic fertilizer replacement and 30% or 50% pesticide application reduction are appropriate for both mitigating nutrient loss and balancing tea yield and quality, especially the combination of 50% organic fertilizer replacement and 50% pesticide reduction, which produced the best results. This study demonstrates the feasibility of dual reductions in fertilizers and pesticides for mitigating environmental hazards while maintaining the yield and quality of tea.

[Study on the distinguishing of root respiration from soil microbial respiration in a Leymus chinensis steppe in Inner Mongolia, China].

Root biomass exponential regression method was used to distinguish root respiration from soil microbial respiration in a Leymus Chinensis steppe in the Xilin River Basin of Inner Mongolia, China. The contribution of root respiration to soil respiration averaged (24 +/- 3)%, ranging from 13%-52%; while the contribution of microbial respiration to soil respiration averaged (76 +/- 3)%, ranging from 48%-87%. Correlation between soil respiration and root biomass was relatively unstable. Root respiration vitality decreased exponentially with the ratio of root to shoot biomass (R2 = 0.661, P = 0.20), while it increased exponentially with soil water content at 0-10 cm, 10-20 cm, 20-30 cm and 30-40 cm (P < 0.0001). CO2 released by root respiration and the contribution of root respiration to soil respiration increased exponentially with root respiration vitality (R = 0.848, P = 0.01; R2 = 0.818, P = 0.01, respectively).

[Analysis of difference between ecosystem respirations of Leymus chinensis steppe and Stipa baicalensis steppe].

Static opaque chamber-chromatographic technique was applied to measure the ecosystem respirations of Leymus chinensis steppe and Stipa baicalensis steppe. The affecting factors of ecosystem respiration were analyzed. The difference between ecosystem respirations of the two grasslands was compared and the reasons resulting in the difference were analyzed. Ecosystem respiration of Leymus chinensis steppe [averaged (12.03 +/- 2.10) mg x (m2 x min)(-1)] was significantly smaller than that of Stipa baicalensis steppe [averaged (20.09 +/- 4.41) mg x (m2 x min)(-1)], while aboveground biomass of Leymus chinensis steppe was significantly larger than that of Stipa baicalensis steppe (p < 0.001). CO2 fluxes of Leymus chinensis steppe and Stipa baicalensis steppe were significantly correlated with air temperature in chamber, soil temperature at 5 cm and 15 cm depth. The results of partial correlation analysis showed that there were no significantly correlation between CO2 flux and Eh, pH, biomass of litter when soil temperature was unchanged, while it shows some correlation with biomass of living plant. The apparent liner relationship between CO2 flux and Eh, pH may be caused by the change of soil temperature. The CO2 fluxes of the two grasslands can be well explained by exponential models based on temperatures. Soil temperature can explain more variations of ecosystem respirations (R2 0.568-0.639) than air temperature in chamber (R2 0.323-0.426). Soil temperature was the most important affecting factor of ecosystem respiration and it may had concealed the effect of aboveground biomass on CO2 flux. The contribution of soil respiration to ecosystem respiration was large in this region and its higher soil organic matter content led to higher CO2 flux of Stipa baicalensis steppe.

Emission characteristics of carbon dioxide in the semiarid Stipa grandis steppe in Inner Mongolia, China.

Using the static opaque chamber method, the soil respiration rates (SR) were measured through the continuous experiments in situ in semiarid Stipa grandis steppe in Xilin River Basin of Inner Mongolia, China from June 2001 to June 2003, in parallel, the difference between the SR and the ecosystem respiration rates (TER) were compared. The results indicated that the seasonal variations of the SR and TER were obvious with higher emissions in growing season and a relatively low efflux level in non-growing season, furthermore, the negative effluxes were found in the observation site in winter; the annual CO2 efflux of total ecosystem ranged from 160.5 gC/(m2 x a) to 162.8 gC/(m2 x a) and that of soil ranged from 118.7 gC/(m2 x a) to 152.3 gC/(m2 x a). The annual SR accounted for about 74.0% to 93.5% of the annual TER, but the results of Analysis of Variance (ANOVA) indicated that the difference between the annual average TER and SR did not reach the significance level of 0.05. The TER was under similar environmental controls as SR, in growing seasons of drought years, the variations of soil moisture at 0-10 cm and 10-20 cm depth could account for 79.1%-95.6% of the changes of the SR and TER, but in non-growing season, more than 75% of the variations of the SR and TER could be explained by the changes of the ground temperature of soil surface layers.

[Analyses of the correlation between the fluxes of CO2 and the distribution of C & N in grassland soils].

Using static dark enclosed chamber technique, the emissions of CO2 from typical temperate grasslands such as Stipa baicalensis, Leymus chinensis, Stipa grandis and Stipa krylovii in Xilin River Basin of Inner Mongolia were measured. And the contents of organic carbon and total nitrogen in different soil layers were also studied to analyze the correlation between the emissions of CO2 and the contents of C & N. The results showed that the emissions of CO2 from the 4 grassland communities were significantly positively correlated with soil organic carbon and total nitrogen in different layers of grassland soils, and the correlation coefficients were almost all above 0.8. That meant the flux of CO2 is severely influenced by the contents of soil organic carbon and total nitrogen when environmental factors were similar. The decreases of soil organic carbon and total nitrogen with the depth into soils (more than 70% of the contents centralizes above 0-30 cm layer) showed that most of them came from the decomposition of organic matter on the earth's surface. In the 0-100 cm layer of grassland soils, the decreases of amount of soil organic carbon and total nitrogen from Stipa baicalensis, Stipa grandis and Leymus chinensis grasslands to Stipa krylovii grassland orderly showed that the impacts of precipitation, evaporation and dryness index on the distribution of soil organic carbon and total nitrogen were important.

[Biogeochemical characteristics of nutrient elements in ungrazed grassland ecosystem in Xilin River Basin].

The biogeochemical characteristics of nutrient elements in Leymus chinensis community and Stipa grandis community, which were both scarcely disturbed by human activities, in Xilin River Basin, Inner Mongolia were studied. The results showed that the storage of N, P, K, S, Ca, Mg, and Si in the soil compartment of soil-plant system was higher than that in the plant subsystem of two communities, and their storage in the live shoots compartment was lower than that in the litter compartment. The disappearing rate of N, P, K and S from the litter compartment was higher than that of Ca, Mg, and Si in the two grassland communities. The decomposition rate of litter in Leymus chinensis community was higher than that in Stipa grandis community. In the grassland soil-plant system, the matter flowing mass kept balance in Leymus chinensis community, but lost balance in Stipa grandis community. The matter participating in biogeochemical cycling in Leymus chinensis community was more than that in Stipa grandis community.