Effects of N fertilizer reduction combined with straw biochar application on the yield, Si, and N nutrition of double-cropping rice.

Nitrogen (N) and silicon (Si) are important nutritional elements for rice. However, excessive N fertili-zer application and the ignorance of Si fertilizer are common in practice. Straw biochar is rich in Si, which can be used as a potential Si fertilizer. In this study, we conducted a consecutive 3-year field experiment to explore the effects of N fertilizer reduction combined with straw biochar application on rice yield, Si and N nutrition. There were five treatments: conventional N application (180 kg·hm-2, N100), 20% N reduction (N80), 20% N reduction with 15 t·hm-2 biochar (N80+BC), 40% N reduction (N60), and 40% N reduction with 15 t·hm-2 biochar (N60+BC). The results showed that compared with N100, 20% N reduction did not affect the accumulation of Si and N in rice; 40% N reduction reduced foliar N absorption, but significantly increased foliar Si concentration by 14.0%-18.8%; while combined application of biochar significantly increased foliar Si accumulation, with an increase of Si concentration by 38.0%-63.3% and Si absorption by 32.3%-49.9%, but further reduced foliar N concentration. There was a significant negative correlation between Si and N concentration in mature rice leaves, but no correlation between Si and N absorption. Compared with N100, N reduction or combined application of biochar did not affect soil ammonium N and nitrate N, but increased soil pH. Nitrogen reduction combined application of biochar significantly increased soil organic matter by 28.8%-41.9% and available Si content by 21.1%-26.9%, with a significant positive correlation between them. Compared with N100, 40% N reduction reduced rice yield and grain setting rate, while 20% N reduction and combined application of biochar did not influence rice yield and yield components. In summary, appropriate N reduction and combined with straw biochar can not only reduce N fertilizer input, but also improve soil fertility and Si supply, which is a promising fertilization method in double-cropping rice fields.

[Impacts of biochar and phosphorus application on soil phosphorus availability and soybean phosphorus uptake]. / ä¸åŒç£·æ°´å¹³é æ–½ç”Ÿç‰©ç‚­å¯¹åœŸå£¤ç£·æœ‰æ•ˆæ€§.

Biochar is beneficial to soil phosphorus (P) availability and crop growth, but the effects vary greatly across different soil types. We investigated the effects of rice straw biochar (4% of total mass) and P application (0, 30, and 90 kg P·hm-2) on soil P availability, phosphomonoesterase activity, and soybean P uptake by using lateritic red soil (pH 4.91) and cinnamon soil (pH 7.24) as test materials. The results showed that biochar application at different P levels significantly increased available P and total P in both soils. Biochar application with 30 kg P·hm-2 increased soil available P with maxima at 192.6% and 237.1% in lateritic red soil and cinnamon soil, respectively. Biochar application with 30 kg P·hm-2 in lateritic red soil significantly increased the activity of alkaline phosphomonoesterase by 78.9%, decreased the content of active organic P by 39.3%, and subsequently stimulated soybean P absorption and growth. Biochar amendment significantly reduced active organic P content in cinnamon soil, but did not affect soil phosphomonoesterase activity and plant growth. The content of active organic P was significantly negatively correlated with soil available P content. In summary, the effect of biochar on soil P availability varied across different soil types (lateritic red soil > cinnamon soil) and P levels (better at 30 kg P·hm-2). Our results could provide scientific basis for a promising application of biochar in reducing the amount of P fertilizer and increasing soybean P uptake, especially in lateritic red soil.

Regulating effects of silicon on Cd-accumulation and stress-resistant responding in rice seedling.

Silicon (Si) application could significantly alleviate the toxic effects of cadmium (Cd) on the growth and development of rice. Here, we examined the regulatory effects of Si on Cd accumulation and stress response in rice seedlings through a hydroponic root separation test. The results showed that the biomass of rice seedlings decreased significantly under Cd stress, while the addition of Si could alleviate such negative effect. The uptake, transfer, and accumulation of Cd in rice seedling were significantly affected by Si addition under Cd stress. Si application under the unilateral Cd stress (Si-Cd+Si, Si-Cd) increased Cd-retention coefficient of root by 83.3%-83.6%, which restricted the transfer of Cd from root to aboveground. However, the treatment with Si added to the non-stressed side (Si-Cd) elevated the uptake and accumulation of Cd in rice seedling, with the accumulation in root being increased by 48.2% when compared to the treatment under the unilateral Cd stress without the addition of Si (CK-Cd). The treatment with Si added in two sides (Si-Cd+Si) decreased the uptake of Cd both in root and aboveground parts by 36.7% and 54.9%, respectively. The addition of Si under bilateral Cd stress (Cd-Cd+Si) significantly reduced the Cd uptake of both the root and aboveground parts by 57.8% and 46.5%, respectively, compared to the treatment of bilateral Cd stress (Cd-Cd). Higher Si concentration in rice seedling was found under the Cd stress. More Si was accumulated in rice seedling to resist the Cd stress when Si was added. The addition of Si affected the absorption of other metal elements in rice seedlings, including calcium (Ca), magnesium (Mg) and manganese (Mn). The concentrations of Ca and Mg in root and aboveground parts were significantly increased by Si addition under bilateral Cd-stress (Cd-Cd+Si), but Mn concentration was changed with the stress degree of Cd. The activities of superoxide dismutase (SOD) and peroxidase (POD) in root were affected by Si under Cd stress, especially for the Si-Cd treatment. The activity of POD in the root of the Cd-stress side and that of SOD in non-stress side were significantly increased, which benefit to scavenging the free radicals induced by Cd stress. In conclusion, Si could regulate the growth of rice seedlings, the uptake of elements such as Cd and Si, and the antioxidant reaction of the root system under the Cd stress. High Si concentration in plant is conducive to enhancing Cd tolerance.

[Effects of nitrogen fertilizer reduction and biochar application on paddy soil nutrient and nitrogen uptake of rice]. / å‡æ°®é æ–½ç¨»ç§†ç”Ÿç‰©ç‚­å¯¹ç¨»ç”°åœŸå£¤å »åˆ†åŠæ¤æ ªæ°®ç´ å¸æ”¶çš„å½±å“.

We explored the impacts of nitrogen (N) reduction and biochar application on soil fertility and nutrient uptake of rice in early and late seasons of 2018 with a field experiment. There were six treatments, including control (no N application, CK), conventional N application (N100), 20% N reduction (N80), 20% N reduction plus biochar application (N80+BC), 40% N reduction (N60), 40% N reduction plus biochar application (N60+BC). Our results showed that 20% and 40% N reduction and/or with biochar application did not affect soil pH, organic matter, total N, total phosphorous (P), total potassium (K), ammonium N, available P and K in comparison with N100 treatment. N80+BC and N60+BC substantially increased soil cation exchange capacity (CEC) at tillering stage and electrical conductivity (EC) at heading stage in late season, respectively. Compared with the treatment with single N reduction, N80+BC significantly increased soil available K in early and late seasons and soil pH and total N in late season, while N60+BC increased soil total K at mature stage in early season. Soil nitrate content was decreased along with the growth stages for all treatments in early season. Compared with tillering stage, soil nitrate N content in conventional N application at heading stage and mature stage was decreased by 50.0% and 71.6%, respectively. Soil nitrate content in biochar treatment only was decreased by 6.3%-45.5%. N application along with biochar application had no significant effects on plant N uptake and utilization in early season. However, N reduction with biochar application significantly increased plant N uptake and N utilization rate by 34.8%-52.4% in late season, compared to conventional N application and single N reduction. Our findings suggest that adequate N reduction along with biochar application could maintain soil health and improve plant N uptake and utilization efficiency.

Cryobacterium ruanii sp. nov. and Cryobacterium breve sp. nov., isolated from glaciers.

Strains Sr36T and TMT4-23T were isolated from No. 1 glacier in Xinjiang Uygur Autonomous Region and Toumingmengke glacier in Gansu Province, PR China, respectively. They were Gram-stain-positive and rod-shaped micro-organisms. The optimum growth temperature of the two strains was 10-14 °C. Phylogenetic analysis showed that the two strains were related to members of the genus Cryobacterium. The average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between strain Sr36T and its close relatives Cryobacterium luteum Hh15T, Cryobacterium aureum Hh31T, Cryobacterium levicorallinum Hh34T and Cryobacterium flavum Hh8T were 81.16-87.24 and 28.0-32.5 %, respectively. The ANI and dDDH values between strain TMT4-23T and its close relative Cryobacterium psychrotolerans 0549T were 81.16 and 22.3 %. The polar lipids of strain Sr36T were diphosphatidylglycerol, phosphatidylglycerol, one unidentified glycolipid and three unidentified lipids. The polar lipids of strain TMT4-23T were diphosphatidylglycerol, phosphatidylglycerol, one unidentified glycolipid, one unidentified phospholipid and six unidentified lipids. The major fatty acids of strain Sr36T were anteiso-C15 : 0, iso-C16 : 0, anteiso-C17 : 0 and anteiso-C15 : 1. The major fatty acids of strain TMT4-23T were anteiso-C15 : 0, anteiso-C17 : 0, iso-C16 : 0, anteiso-C15 : 1 and iso-C15 : 1. Both strains contained 2,4-diaminobutyric acid and their predominant menaquinone was MK-10. On the basis of the phenotypic, phylogenetic and genotypic data, two novel species Cryobacterium ruanii sp. nov. (type strain = Sr36T=CGMCC 1.9275T=NBRC 113797T) and Cryobacterium breve sp. nov. (type strain =TMT4-23T=CGMCC 1.9556T=NBRC 113800T) are proposed.

Cryobacterium melibiosiphilum sp. nov., a psychrophilic bacterium isolated from glacier ice.

A psychrophilic, Gram-stain-positive, rod-shaped bacterium, designated Hh39T, was isolated from Xinjiang No. 1 glacier in PR China. Strain Hh39T was catalase-positive, oxidase-negative and could grow at 0-18 °C, pH 6.0-11.0 and in the presence of 0-2.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain Hh39T belonged to the genus Cryobacterium. The highest level of 16S rRNA gene sequence similarities were found to the type strains of Cryobacterium levicorallinum (99.01 %), Cryobacterium luteum (98.90 %), Cryobacterium aureum (98.90 %) and Cryobacterium roopkundense (98.75 %). However, the low average nucleotide identity (80.65-81.89 %) and digital DNA-DNA hybridization values (22.1-23.8 %) between strain Hh39T and its four closest relatives indicated that it represents a novel species of the genus Cryobacterium. The predominant fatty acids were anteiso-C15:0, anteiso-C15:1, iso-C16:0 and anteiso-C17:0. The major menaquinone was MK-10. The polar lipids were diphosphatidylglycerol, phosphatidylglycerol, one unidentified lipid and one unidentified glycolipid. On the basis of results of phenotypic, genotypic and phylogenetic analyses, a novel species, Cryobacterium melibiosiphilum sp. nov., is proposed, with Hh39T (=NBRC 107884T=CGMCC 1.11212T) as the type strain.

[Effects of carbon and nitrogen additions on soil organic C, N, P contents and their catalyzed enzyme activities in a grassland.] / ç¢³æ°®æ·»åŠ å¯¹è‰åœ°åœŸå£¤æœ‰æœºç¢³æ°®ç£·å«é‡åŠç›¸å ³é ¶æ´»æ€§çš„å½±å“.

Soil organic C, N, P contents and their catalyzed enzyme activities play an important role in maintaining and supplying energy and nutrient in grasslands. There is no consensus on the effects of N deposition on soil organic nutrients and enzyme activities in grassland ecosystems. It remains unclear whether C addition will retard the negative effects of N deposition. We carried out an experiment in Hulun Buir grassland of Inner Mongolia to examine the effects of C and N additions on soil organic C, N, P and relative enzyme activities after three years treatments. The experiment was conducted with N treatments at five levels (0, 25, 50, 100 and 200 kg·hm-2·a-1) and with C treatments at three levels (0, 250 and 500 kg·hm-2·a-1). The results showed that higher levels of N addition significantly decreased dehydrogenase (DHA) and ß-1,4-N-acetylglucosaminidase (NAG) activities by 22.3% and 12.5%, respectively. Nitrogen addition had no significant effect on soil organic N and decreased the organic C and P contents by 6.6% and 14.5%, respectively. High C addition significantly increased DHA, ß-glucosidase (BG) activities and increased soil organic N and organic P by 15.1%, 12.2%, 1.9%, 2.6%, respectively. The results suggested that continuous N inputs inhibited microbial activities and caused losses of soil organic C and organic P. Carbon addition could enhance microbial activities and promote the secretion of enzymes and increase soil organic N and P. The combined C and N addition could play an important role in maintaining the balance and supply of soil C, N, and P in grassland ecosystem.

Heavy metal bioaccumulation and cation release by growing Bacillus cereus RC-1 under culture conditions.

In an effort to explore the detoxifying mechanisms of B. cereus RC-1 under heavy metal stress, the bioaccumulation by growing cells under varying range of pH, culture time and initial metal concentration were investigated from a perspective of cation release. The maximum removal efficiencies were 16.7%, 38.3%, 81.4% and 40.3% for Cu2+, Zn2+, Cd2+ and Pb2+, respectively, with initial concentrations of 10 mg/L at pH 7.0. In presence of Cu2+ or Zn2+, large quantities of cations were released into the medium in descending order of Na+>K+>Ca2+>Mg2+, while bioremoval of the two essential metals Cd2+ and Pb2+ was accompanied with cellular Na+ and Mg2+ uptake from the medium, respectively. The relative mean contributions of intracellular accumulation to the total removal were approximately 19.6% for Cu2+, 12.8% for Zn2+, 51.1% for Cd2+, and only 4.6% for Pb2+. Following exposure at high concentration, B. cereus RC-1 could keep intracellular Cd2+ concentrations constant, possibly by means of a Cd-efflux system whose activity coincided with uptake of Na+, and reduce intracellular Pb2+ concentration due to the effect of Mg2+ on limiting Pb2+ access to the cells. Cellular morphology, surface functional groups and intracellular trace elements were further investigated by SEM-EDX, TEM-EDX, FTIR and ICP-MS analysis. The phenomena that removal of Cd2+ and Pb2+ coincided with uptake of Na+ and Mg2+, respectively, inspires a novel research perspective towards the study of protective mechanism of bacterial cells against the toxicity of heavy metals.