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The leafy vegetable production is challenged by the excessive water and fertilizer input, as well as the continuous cropping obstacle caused by the soil environment change. The different combinations of irrigation methods, bedding types and film mulch would change the irrigation input and the soil environment, but the influence of these different combinations on yield and its relation to the soil microbial communities were not fully researched. Therefore, a 4-year experiment was designed. There were five treatments: flat-bed with flood irrigation (FF), flat-bed with drip irrigation (FD), flat-bed with drip irrigation under film mulch (FDM), raised-bed with drip irrigation (RD) and raised-bed with drip irrigation under film mulch (RDM). As a result, FDM had the highest celery yield and moderate crop quality when comparing the three seasons' average. It produced relatively lower yield in 2016, and the highest yield in both 2017 and 2019, which were, respectively, 13.64% and 10.69% higher than the FF did. The FDM also led to the highest soil nitrate and second-highest ammonium nitrogen concentration by the end of the whole experiment, which was 25.62% and 49.63% higher than FF did. After 4-year cultivation, the key microbes promoted by FDM related to nitrogen-fixing included norank_f_Rhodospirillaceae, norank_c_Nitrospira and Nitrosomonadaceae. Meanwhile, the quantity of Caldilineaceae, Hydrogenispora and Halocella was reduced in the soil of FDM, potentially helping maintain the soil organic carbon pool. Besides, FDM suppressed several potential pathogenic communities, including bacteria family BIrii41 and fungi genera Aspergillus and Gibellulopsis. The water flow pattern in flat-bed and film plastic residue could cause the change of soil nitrogen cycling pattern and microbial community. In a word, FDM benefitted the crop yield mainly by improving crop available nitrogen, and it potentially reduced the soil carbon loss and crop disease pathogens. [ABSTRACT FROM AUTHOR]

The drought stress created by deficit irrigation has been widely introduced into production for fruit quality improvement, whilst silicon is considered as a functional element in plant antistress process. To explore the influence of deficit irrigation and silicon application on the strawberry fruit quality and the plant's response to drought stress, a split-plot experiment was conducted. The impacts of the treatments start-time was also evaluated. The plants were subjected to two irrigation regimes, deficit irrigation (DI) or full irrigation, and two foliar sprays, 0.01 mol L− 1 Na2SiO3 (Si) or water, with two treatment start-time, as after first bloom (Fr) or after transplanting. Therefore, there were 6 different treatments (considering treatment start-time) and a control group, which were DI, FrDI, Si, FrSi, DISi, FrDISi and CK. As a result, the DI significantly increased the leaf ascorbate, leaf anthocyanins and specific leaf weight by 93.5%, 109.9% and 24.5%, but it also reduced fruit reducing sugars concentration and single fruit mass by 25.1% and 12.6%, respectively. Whilst the FrDI increased specific leaf weight by 27.9% and had no negative effect on fruit quality. The timing of starting silicate spray didn't influence leaf morphology or fruit quality, but the FrSi significantly increased the percentage of leaf sucrose to total sugars by 9.0%, and the Si didn't. The DISi and FrDISi tended to increase the concentration of fruit sugars, glutamate, polyphenols, and organic acids. Although the DISi showed more obvious effect on improving the fruit nutritive values, the FrDISi tended to have lighter negative impact on fruit size, compared to CK. We concluded that the combination of deficit irrigation and silicate spray started after the first bloom could effectively improve the fruit sugars, glutamate and polyphenols, without reducing the fruit size, due to the mitigation of plant antistress response. [ABSTRACT FROM AUTHOR]

This study investigated the effect of biochar on real domestic wastewater treatment by constructed wetlands (CWs). To evaluate the role of biochar as a substrate and electron transfer medium on nitrogen transformation, three treatments of CW microcosms were established: conventional substrate (T1), biochar substrate (T2), and biochar-mediated electron transfer (T3). Nitrogen removal increased from 74% in T1 to 77.4% in T2 and 82.1% in T3. Nitrate generation increased in T2 (up to 2 mg/L) but decreased in T3 (lower than 0.8 mg/L), and the nitrification genes (amoA, Hao, and nxrA) in T2 and T3 increased by 132–164% and 129–217%, respectively, compared with T1 (1.56 × 104– 2.34 × 107 copies/g). The nitrifying Nitrosomonas, denitrifying Dechloromonas, and denitrification genes (narL, nirK, norC, and nosZ) in the anode and cathode of T3 were significantly higher than those of the other treatments (increased by 60-fold, 35-fold, and 19–38%). The genus Geobacter, related to electron transfer, increased in T3 (by 48-fold), and stable voltage (~150 mV) and power density (~9 uW/m2) were achieved. These results highlight the biochar-mediated enhancement of nitrogen removal in constructed wetlands via nitrification, denitrification, and electron transfer, and provide a promising approach for enhanced nitrogen removal by constructed wetland technology. [ABSTRACT FROM AUTHOR]

Decoupling livestock and cropland production at regional scale have poor resource-use efficiency and detrimental effects on environment in China. It is therefore necessary to identify the decoupled livestock and cropland production system and make recommendations to recouple livestock and cropland. This study used the indexes of land carrying capacity (LCC), animal manure absorption capacity (AMAC), and risk warning value (R) to evaluate the coupling between cropland and livestock at the local scale in the Huang-Huai-Hai region. The decoupling of cropland and livestock in the case of Beijing (SY_BJ) was found assessed with lower theoretical value of LCC and higher theoretical value of AMAC compared with local actual situation, categorized as grade IV with a high R value (above 1). Contrary results were found that the livestock and cropland production systems were coupled at the local scale in the cases located in Hebei and Shandong Provinces, categorized as grade I or II. Two measures were used to optimize the decoupled case by adjusting the ratio of manure to fertilization or reducing breeding quantity. The decoupled case of SY_BJ could be optimized by adjusting the ratio of manure to fertilization (95.34% based on nitrogen and 81.97% based on phosphorus, respectively). The breeding quantity in this case should be reduced by at least 46% to recouple the livestock and cropland at the local level to manage nutrient surpluses from livestock and poultry breeding. [ABSTRACT FROM AUTHOR]

The effect of pH on available Cd in calcareous soils and culture substrate was studied by adding exogenous Cd and artificially adjusting the pH to create different pH conditions. It is expected to provide reference for the control of Cd pollution by adjusting pH. The cadmium chloride was added to the calcareous soil and culture substrate to make the total cadmium content 1.0 mg kg–1. The pH of soil and substrate was adjusted, and then the available cadmium content in soil and cultivation substrate was detected under different pH conditions. The content of available Cd in calcareous soil decreased with increasing pH in the range of pH 3.40 to 8.97, showing a significant negative correlation. At a pH range of 3.03 to 4.37, the available Cd content in the culture substrate increased significantly with increasing pH, while the available Cd content in the culture substrate at a pH range of 4.37 to 9.47 was not significantly different. [ABSTRACT FROM AUTHOR]