Biochar and Chlorella increase rice yield by improving saline-alkali soil physicochemical properties and regulating bacteria under aquaculture wastewater irrigation.

The combined effects of biochar and Chlorella under aquaculture wastewater irrigation in improving saline-alkali soil physicochemical properties, microbial communities, and rice yield, is not yet clear. This study utilized soil physicochemical indicators and gene sequencing to examine the effect of salinity stress, biochar and Chlorella under aquaculture wastewater irrigation on soil properties, bacterial community compositions, and rice production. Treatments included three factors in a randomized complete block design with three replications: (i) Biochar - 40 tons ha -1 (BW) versus no-biochar (BN); (ii) Salinity - 3‰ salinity (SH) versus 1‰ salinity (SL); and (iii) Chlorella - with 107 cells mL -1 Chlorella (CW) versus no-Chlorella (CN). The results revealed that increased salinity adversely affected the soil nutrients (TOC, NO3⁻-N, NH4+-N, Olsen-P), and enzyme activity (urease, sucrase, catalase), resulting in a 9.67% reduction in rice yield compared to SL treatment. However, the close correlation between alterations in soil bacterial communities, functions, and soil physicochemical properties, as well as rice yield, indicated that biochar and Chlorella promoted rice yield by enhancing the physicochemical properties of saline-alkali soil and bacterial community when irrigated with aquaculture wastewater: (1) addition of biochar increased the146.05% rice yield by increasing TOC content, the complexity of bacterial co-occurrence patterns, nitrogen fixation potential, and nitrification potential, (2) addition of Chlorella increased TOC, NO3⁻-N, NH4+-N, enhanced urease, sucrase, catalase activity, and nitrification potential to increased rice yield by 60.29%, and (3) compared with the treatment T3 (SHBNCN), the treatments with biochar (BW) and Chlorella (CW) increased the yield by 561.30% and 445.03% under 1‰ and 3‰ salinity, respectively. These findings provide novel perspectives on the capacity of biochar and Chlorella to improve saline-alkali soil properties and increase rice yield irrigated with aquaculture wastewater.

Relationships between stable isotope natural abundances (δ13C and δ15N) and water use efficiency in rice under alternate wetting and drying irrigation in soils with high clay contents.

Natural abundance of the stable isotope (δ13C and δ15N) in plants is widely used to indicate water use efficiency (WUE). However, soil water and texture properties may affect this relationship, which remains largely elusive. Therefore, the purpose of this study was to evaluate δ13C as affected by different combinations of alternate wetting and drying irrigation (AWD) with varied soil clay contents in different organs and whole plant and assess the feasibility of using δ13C and δ15N as a physiological indicator of whole-plant water use efficiency (WUEwhole-plant). Three AWD regimes, I100 (30 mm flooded when soil reached 100% saturation), I90 (30 mm flooded when reached 90% saturation) and I70 (30 mm flooded when reached 70% saturation) and three soil clay contents, 40% (S40), 50% (S50), and 60% (S60), were included. Observed variations in WUEwhole-plant did not conform to theoretical expectations of the organs δ13C (δ13Corgans) of plant biomass based on pooled data from all treatments. However, a positive relationship between δ13Cleaf and WUEET (dry biomass/evapotranspiration) was observed under I90 regime, whereas there were no significant relationships between δ13Corgans and WUEET under I100 or I70 regimes. Under I100, weak relationships between δ13Corgans and WUEET could be explained by (i) variation in C allocation patterns under different clay content, and (ii) relatively higher rate of panicle water loss, which was independent of stomatal regulation and photosynthesis. Under I70, weak relationships between δ13Corgans and WUEET could be ascribed to (i) bigger cracks induced by water-limited irrigation regime and high clay content soil, and (ii) damage caused by severe drought. In addition, a negative relationship was observed between WUEwhole-plant and shoot δ15N (δ15Nshoot) across the three irrigation treatments, indicating that WUEwhole-plant is tightly associated with N metabolism and N isotope discrimination in rice. Therefore, δ13C should be used cautiously as an indicator of rice WUEwhole-plant at different AWD regimes with high clay content, whereas δ15N could be considered an effective indicator of WUEwhole-plant.

Dissecting the combined effects of cultivar, fertilization, and irrigation on rhizosphere bacterial communities and nitrogen productivity in rice.

Rice cultivars, fertilizer types, and irrigation modes can affect soil bacterial communities and thus influence nitrogen utilization by soil microorganisms and plants. However, the combined effects of these three factors on soil bacterial communities and nitrogen productivity in rice plants remain unknown. Here, we examined the response of rhizosphere bacteria and nitrogen productivity to different combinations of cultivar (japonica or indica), fertilization (organic plus chemical or chemical), and irrigation (controlled or shallow-frequent). The results demonstrated the interactive effects of cultivars with fertilizers and irrigation on rhizosphere bacterial communities, nitrogen accumulation, and grain yield. These significant interactive effects were related to differences in the response to soil environment (soil inorganic nitrogen concentration and moisture condition) between diverse rhizosphere bacteria recruited by indica and japonica. We found that rhizosphere bacterial communities recruited by indica were more active in soil fertilized with organic plus chemical nitrogen, while those recruited by japonica were suitable for living in soil fertilized with chemical nitrogen. Rhizosphere bacteria diversity positively correlated with soluble inorganic nitrogen in soil, suggesting that more diverse bacterial communities and greater contents of NH4+-N might favor nitrogen accumulation in rice plants under shallow-frequent irrigation. The combinations of cultivars, fertilizer types, and irrigation greatly affected rhizosphere bacterial communities, thus triggering a significant difference in soil inorganic nitrogen content, which could play an essential role in affecting nitrogen productivity.

Blue, green, and grey water footprints assessment for paddy irrigation-drainage system.

Water footprint (WF) quantifies the impact of paddy field evapotranspiration (ET) and non-point source pollution on water resources and is an evaluation index for water sustainability. However, it is difficult to measure accurately using the existing method, which is based on parameter assumption without considering the field water conditions. In this study, a generic and physically based method for blue, green, and grey water accounting in paddy rice cultivation is introduced. We conducted field experiments using the common flood irrigation (CFI) and water-saving irrigation (SWI) modes in Nanjing, East China. By tracing the sources of ET and the migration process of multiple pollutants (TN, TP, NH4+-N, and NO3--N), the characteristics of blue-green water consumption and the actual amount of water required to dilute pollutants at different growth stages of rice under CFI and SWI were analyzed. The WF of paddy rice was 1000 m3/t (49% WFgreen, 17% WFblue, 34% WFgrey) and 910 m3/t (50% WFgreen, 10% WFblue, 40% WFgrey) for CFI and SWI, respectively. The WF for paddy rice production was reduced by approximately 9% under SWI compared to CFI, with declines of 47% for WFblue and 8% for WFgreen. The SWI mode changed the ratio of blue to green water fluxes in field water by reducing irrigation during non-critical periods, and green water was used preferentially to enhance its utility. This conceptual method is the first to describe the formation mechanism of blue, green, and grey WFs in paddy systems. It can be extended to different scales and agro-ecosystems that show the influence of crop cultivation on water resources.

Variation and driving mechanism analysis of water footprint efficiency in crop cultivation in China.

Water footprint regulation in agricultural production is of great significance to regional food, water and ecological sustainability. The spatial-temporal characteristics and driving mechanism of water footprint efficiency (WFE) in crop cultivation in China during 1996-2015 were analysed based on the quantification of the crop-water relationship. The results showed that China's total crop water footprint (TWF) was 1125.6 G m3, and the blue, green and grey components accounted for 24.4%, 57.4% and 18.2%, respectively. The national WFE was 0.681 and increased over time due to the improvement of agricultural technology. Spatial autocorrelation analysis showed that provinces with similar WFE values were clustered geographically and have gradually weakened since 2012. Provinces with a high WFE were concentrated in the southeast and northeast, and low-value provinces were distributed in the west of China. The main anthropogenic driving factors were the preliminary fertilizer application intensity (FAI) and population density (PD); however, these factors have been replaced by the irrigation efficiency (IE), agricultural water use ratio (AWR) and irrigation area proportion (IAP) in recent years. Specific regions should formulate water resource management policies according to their WFE performance, agricultural production scale and water resource endowment. The northeast should control crop cultivation and enhance the yield to solve water shortage problems, the central provinces should improve WFE, and the southern provinces should contribute to the promotion of national water use efficiency by expanding crop sowing and irrigation areas. This study provides a reference for water resource management in the context of social and environmental change.

Analysis of the characteristics and driving forces of water footprint productivity in paddy rice cultivation in China.

BACKGROUND: Water productivity improvement is fundamental to agricultural water use control, and the water footprint provides a new and comprehensive method for identifying the crop-water relationship. This study is intended to explore the spatiotemporal pattern and driving forces underlying the rice water footprint productivity (WFP) in China during the years 1996-2015 based on calculations of the provincial blue, green, gray, and white water footprints. RESULTS: The national water footprint in paddy rice cultivation was 240.97 Gm3 , and green water accounted for 43.9% of the total. The WFP was 0.795 kg m-3 and increased over time in all 30 provinces for which it was calculated. The growth rate in the northern provinces was greater than that in the southern part of the country. The WFP clustered geographically in all years observed. High-value provinces were concentrated to the south of the Yangtze River, whereas most of the provinces that showed a low WFP were distributed in the north China and northwest subregions. Precipitation and sunshine hours were the most obvious driving factors of rice WFP. The effects of agricultural input, e.g., agricultural machinery power, pesticides, and irrigation efficiency, on WFP also could not be ignored. CONCLUSION: The WFP is a comprehensive and useful index of the crop-water relationship and water-use efficiency. Improving agricultural input and irrigation technology are reliable approaches for WFP promotion. Areas in northeast China showed the most urgent need for improving the rice WFP, and the inclusion of the main grain producing areas in the Yangtze River Basin will further reduce ineffective water occupancy to improve water-use efficiency. © 2019 Society of Chemical Industry.

Hospital resources for urokinase/recombinant tissue-type plasminogen activator therapy for acute stroke in Beijing.

BACKGROUND: We focus on the current resource level for UK/rt-PA therapy in hospitals in Beijing to design strategies for improving treatment for stroke patients. METHODS: The data were collected through surveys of 124 grade II or higher hospitals in Bejing, which provide stroke treatment, from July to September 2006. RESULTS: Of the surveyed hospitals, 50% and 92.6% were capable in providing intravenous UK/rt-PA treatment and head CT service, respectively. Eight (7.4%) hospitals have specialized stroke units and 106 (98.1%) hospitals have EDs. We found significant differences between hospitals that can provide UK/rt-PA therapy and the hospitals that cannot in the levels of specialists and clinical care capacity as follows: CT (100% vs 85.2%; P = 0.01), CTA (46.3% vs 22.2%; P = .014), MRI (66.7% vs 22.2%; P = .000), MRA (57.4% vs 20.4%; P = .000), DWI (48.1% vs 9.3%; P = .000), PWI (31.5% vs 5.6%; P = .001), DSA (63.0% vs 25.9%; P = .000), neurologists (100% vs 79.6%; P = .001), neurosurgeons (75.9% vs 44.4%; P = .002), carotid stenting (33.3% vs 5.6%; P = .000), stroke unit (14.8% vs 0%; P = .01), and acute stroke care system (31.5% vs 0%; P = .000). CONCLUSION: The thrombolysis treatment facilities in Beijing are not sufficient. Hospitals in Beijing should organize stroke-related medical sources.