Bingzi Zhao

Nitrate leaching in an Andisol treated with different types of fertilizers.

Nitrate (NO3) leaching was studied in an Andisol treated with four N fertilizers (SC: swine compost, CU: coated urea, AN: ammonium N, or NF: no fertilizer) for 7 years. Sweet corn (Zea mays L.) was grown in summer, followed by Chinese cabbage (Brassica rapa L. var. amplexicaulis) or cabbage (Brassica oleracea L. var. capitata) in autumn each year. In chemical fertilizer plots treated with AN or CU, NO(3)-N concentrations in soil water at 1-m depth increased markedly in the summer of the second year and fluctuated between 30 and 60 mg l(-1). In the SC plot, NO(3)-N concentration started increasing in the fourth year, reaching the same level as in the AN and CU plots in the late period of the experiment. In the NF plot, NO(3)-N concentration was about 10 mg l(-1) for the first 4 years and decreased to 5 mg l(-1). The potential NO(3)-N concentrations by an N and water balance equation satisfactorily predicted NO(3)-N concentration in the AN and CU plots, but substantially overestimated that in the SC plot, presumably because a large portion of N from SC first accumulated in soil in the organic form. Our results indicate that, under the Japanese climate (Asian monsoon), excessive N from chemical fertilizers applied to Andisols can cause substantial NO3 leaching, while compost application is promising to establish high yields and low N leaching during a few years but would cause the same level of NO3 leaching as in chemically fertilized plots over longer periods.

Water-use efficiency and carbon isotope discrimination in two cultivars of upland rice during different developmental stages under three water regimes

AbstractA pot experiment was conducted in a glasshouse to clarify and quantify the effect of plant part, water regime, growth period, and cultivar on carbon isotope discrimination (CID), and to analyze the relationship between CID, stomatal behavior and water-use efficiency (WUE). The experiment was comprised of two upland rice (Oryza sativa L.) cultivars and three water regimes (100, 70, and 40% of saturation moisture) in a completely randomized design. Plants were harvested at tillering, flowering, and maturity. No significant cultivar differences in above-ground dry matter-based WUE (WUEA) and total dry matter-based WUE (WUET) were observed. WUEA (and WUET) increased with water stress up to tillering, but decreased with water stress after tillering. Significant cultivar differences in CID in all the analyzed plant parts were observed at all harvest times. Reduction in CID with water stress was greatest at tillering, and the effect was less pronounced at flowering and at maturity. At each harvest, the effect was most pronounced in newly developed plant parts. Root and grain tended to have the lowest CID values, and stem the highest, at all harvest times. A negative relationship was observed between CID measured at tillering and WUEA (and WUET) measured over the period from seedling to tillering, whereas a reverse relationship was obtained between CID measured at flowering and WUEA (and WUET) measured over the period from tillering to flowering, and an unclear relationship between CID measured at maturity and WUEA (and WUET) measured over the period from flowering to maturity. The ratio of the intercellular and atmospheric concentration of CO2 (Ci/Ca) were closely associated with CID throughout the water regimes when one cultivar was considered, however, cultivar differences in CID were not related to variations in Ci/Ca. The results indicate that significant cultivar difference existed in CID in all the analyzed plant parts at all harvest times, while corresponding difference in WUEA (and WUET) between the cultivars was not necessarily consistent. Abbreviations: WUE – water-use efficiency; WUEi – instantaneous WUE (or leaf transpiration efficiency); ADM – above-ground dry matter; TDM – total dry matter; WUEA– ADM-based WUE; WUET– TDM-based WUE} CID – carbon isotope discrimination; NL – the newest leaves; FEL – recently fully expanded leaves; FL – flag leaves; P – photosynthesis rate; g – leaf stomatal conductance to water vapor; Ci– intercellular CO2 concentration; Ca– atmospheric CO2 concentration; T – transpiration rate; gs – total conductance of CO2

Carbon Mineralization and Microbial Attributes in Straw-Amended Soils as Affected by Moisture Levels

An 80-d incubation experiment was conducted to investigate straw decomposition, the priming effect and microbial characteristics in a non-fertilized soil (soil 1) and a long-term organic manure-fertilized soil (soil 2) with and without 13C-labeled maize straw amendment under different moisture levels. The soil 2 showed a markedly higher priming effect, microbial biomass C (Cmic), and β-glucosidase activity, and more abundant populations of bacteria and fungi than the soil 1. Also, soil CO2 emission, Cmic, β-glucosidase activity, and bacterial and fungal population sizes were substantially enhanced by straw amendment. In the presence of straw, the amount of straw mineralization and assimilation by microbes in the soil at 55% of water holding capacity (WHC) were significantly higher by 31% and 17%, respectively, compared to those at 25% of WHC. In contrast, β-glucosidase activity and fungal population size were both enhanced as the moisture content decreased. Cmic decreased as straw availability decreased, which was mainly attributed to the reduction of straw-derived Cmic. Amended soils, except the amended soil 2 at 25% of WHC, had a more abundant fungal population as straw availability decreased, indicating that fungal decomposability of added straw was independent of straw availability. Non-metric multidimensional scaling analysis based on fungal denatured gradient gel electrophoresis band patterns showed that shifts in the fungal community structure occurred as water and straw availability varied. The results indirectly suggest that soil fungi are able to adjust their degradation activity to water and straw availability by regulating their community structure.

Chemical nature of humic substances in two typical Chinese soils (upland vs paddy soil): A comparative advanced solid state NMR study

Knowledge of the structural features of humic substances (HSs) is essential for elucidating the mechanisms of humification in different soil environments and realizing their profound roles in environmental issues. The aim of this work was to investigate the chemical structures of fulvic acid (FA), humic acid (HA) and humin (HM) fractions isolated from an upland soil (Fluvisol) and a paddy soil (Anthrosol) typical in China using advanced solid-state 13C nuclear magnetic resonance (NMR) techniques. The results revealed that there were great structural differences of HSs between the two soils. The two FAs showed distinct quantitative differences in aliphatics with more polysaccharides in the FA from the upland soil than from the paddy soil. The HM from the upland soil differed from the paddy soil HM in having more proteins/peptides (23% vs 20%), total aromatics (21% vs 12%) as well as fewer lipids (24% vs 35%) and polysaccharides (27% vs 31%). The HM fractions represented the most different components of organic matter between the two soils. The degree of difference between the two HAs fell in between that of FAs and HM fractions. In particular, the HA from the upland soil had relatively greater degree of aromaticity. Our study indicated that the upland soil exhibited a higher degree of humification compared with the paddy soil. Among the three humic fractions, the FAs featured COO/N-CO groups, and the HAs were more enriched in protonated aromatic C for both soils. In contrast, the two HM fractions contained more O-alkyl C and fewer aromatics than did the other humic fractions, being closer to the original organic materials in soils. We speculate that the evolutionary route of HSs is likely to be the transformation of original organic materials into HM, followed by increased degradation, further oxidization and conversion into HA, and then into FA.

Removal of bacteriophages MS2 and phiX174 from aqueous solutions using a red soil

Adsorption and desorption of viruses onto and from an adsorbent may have a dominant role in evaluating removal efficiency of a material. This study evaluated the effectiveness of a red soil from south part of China to remove two viruses, MS2 and phiX174, by adsorption from dilute aqueous solutions using a set of equilibrium and kinetic batch experiments. The effect of presence/absence of autochthonous microorganisms was also investigated. The results showed that when the autochthonous microorganisms were present, the red soil adsorbed more than 99.95% of MS2 and 98.23% of phiX174, in which most of them were inactivated and/or irreversibly adsorbed. Sterilization led to an increase in MS2 adsorption, while decreased the adsorption of phiX174, indicating that sterilization-induced virus adsorption is virus type dependent. Fewer viruses could be desorbed from the sterilized soil as compared to the nonsterilized soil, probably because sterilization led to an increase in the strength of adsorption force between the soil and viruses. Though the overall virus removal efficiency by the red soil was less than the USPEA required value of 99.99%, we suggest the potential of the red soil as a starting material in removing water heavily polluted with viruses.

Influence of Long-Term Fertilization on Selenium Accumulation in Soil and Uptake by Crops

Continuous applications of organic and inorganic fertilizers can affect soil and food quality with respect to selenium (Se) concentrations. A long-term (over 20 years) experimental field study, started in 1989, was conducted to investigate the changes in soil Se fractions and its uptake by crops, as affected by different fertilizer practices, in the North China Plain with an annual crop rotation of winter wheat and summer maize. The long-term experiment was arranged in a complete randomized block design consisting of 4 replications with 7 fertilizer treatments: 1) organic compost (OC), 2) half organic compost plus half N-P-K chemical fertilizers (OC + NPK), 3) N-P-K fertilizers (NPK), 4) N-P fertilizers (NP), 5) P-K fertilizers (PK), 6) N-K fertilizers (NK), and 7) an un-amended control. Soil samples from the surface (20 cm) were collected in 1989, 1994, 1999, 2004 and 2009 to characterize Se and other soil properties. In 2009, the average soil Se concentrations in the treatments (149 ± 8 pg kg−1) were higher than those in the soil samples collected in 1989 at the beginning of the experiment (112 ± 4 pg kg−1), and decreased in the order of OC > OC + NPK > NPK ≈ NP > PK ≈ NK > control. Sequential extraction showed the oxidizable fraction (50.06% ± 3.94%) was the dominant form of Se in the soil, followed by the residual fraction (24.12% ± 2.89%), exchangeable fraction (15.09% ± 4.34%) and Fe-Mn oxides fraction (10.73% ± 4.04%). With an increase of soil K, the exchangeable Se concentrations in the soil increased. The Se concentrations in the soil tillage layer (0–20 cm) were mainly related to soil organic carbon (SOC), although different contributions came from atmospheric deposition, irrigation and fertilizers. With the accumulation of SOC, the uptakes of soil Se by two crops were inhibited. For the OC and OC + NPK treatments, Se concentrations in wheat grains were lower than the critical standard of Se in stable food (100 µg kg−1). Additionally, Se concentrations in grains were also decreased by the deficiencies of major soil nutrients, especially P.

Natural ^15N and ^13C Abundance in Andisols Influenced by Long-Term Fertilization Management in Japan

Abstract Two field experiments were conducted on Andisols in Japan to evaluate the changes in the natural 15N and 13C abundance in the soil profile and to determine whether the values of δ15N could be used as an indicator of fertilizer sources or fertilizer fate. The 6-year experiment conducted at the National Agricultural Research Center (NARC) consisted of the following treatments: application of swine compost (COMPOST), slow-release nitrogen fertilizer (SRNF), readily available nitrogen fertilizer (RANF), and absence of fertilization (CONTROL). Experimental plots located at the Nippon Agricultural Research Institute (NARI) received cattle compost at different rates for 12 years; a forest soil at this site was sampled for comparison. Swine compost application led to a considerable change in the δ15N distribution pattern in the soil profile, with the highest δ15N values recorded in the top 20 cm layers of the COMPOST plot, decreasing in the sequence of CONTROL >- RANF > SRNF, mainly due to the relatively high δ15N value of swine compost and its subsequent decomposition. In contrast, SRNF application resulted in the lowest δ15N values in soil, indicating the presence of negligible nitrogen losses relative to input and low nitrogen cycling rates. Values of δ15N increased with compost application rates at NARI. In the leachate collected at 1-m depth, the δ15N values decreased in the sequence of COMPOST > RANF ≥ CONTROL > SRNF. The δ13C values in soil peaked in the 40–60 cm layers for all the fertilizers. The δ13C value was lowest in forest soil due to the presence of plant residues in soil organic matter. These results indicated that the δ15N values in the upper soil layers or leachate may enable to detect pollution sources of organic or inorganic nitrogen qualitatively in Andisols.

Comparative analysis of potassium deficiency-responsive transcriptomes in low potassium susceptible and tolerant wheat ( Triticum aestivum L.)

Potassium (K+) deficiency as a common abiotic stress can inhibit the growth of plants and thus reduce the agricultural yields. Nevertheless, scarcely any development has been promoted in wheat transcriptional changes under K+ deficiency. Here we investigated root transcriptional changes in two wheat genotypes, namely, low-K+ tolerant “Tongzhou916” and low-K+ susceptible “Shiluan02-1”. There were totally 2713 and 2485 probe sets displayed expression changes more than 1.5-fold in Tongzhou916 and Shiluan02-1, respectively. Low-K+ responsive genes mainly belonged to the categories as follows: metabolic process, cation binding, transferase activity, ion transporters and so forth. We made a comparison of gene expression differences between the two wheat genotypes. There were 1321 and 1177 up-regulated genes in Tongzhou916 and Shiluan02-1, respectively. This result indicated that more genes took part in acclimating to low-K+ stress in Tongzhou916. In addition, there were more genes associated with jasmonic acid, defense response and potassium transporter up-regulated in Tongzhou916. Moreover, totally 19 genes encoding vacuolar H+-pyrophosphatase, ethylene-related, auxin response, anatomical structure development and nutrient reservoir were uniquely up-regulated in Tongzhou916. For their important role in root architecture, K+ uptake and nutrient storage, unique genes above may make a great contribution to the strong low-K+ tolerance in Tongzhou916.

Effects of changes in straw chemical properties and alkaline soils on bacterial communities engaged in straw decomposition at different temperatures.

Differences in the composition of a bacterial community engaged in decomposing wheat straw in a fluvo-aquic soil at 15 °C, 25 °C, and 35 °C were identified using barcode pyrosequencing. Functional carbon groups in the decomposing wheat straw were evaluated by 13C-NMR (nuclear magnetic resonance). Actinobacteria and Firmicutes were more abundant, whereas Alphaproteobacteria and Bacteroidetes were less abundant, at higher temperatures during the later stages of decomposition. Differences in the chemical properties of straw accounted for 19.3% of the variation in the community composition, whereas soil properties accounted for more (24.0%) and temperature, for less (7.4%). Carbon content of the soil microbial biomass and nitrogen content of straw were significantly correlated with the abundance of Alphaproteobacteria, Actinobacteria, and Bacteroidetes. The chemical properties of straw, especially the NCH/OCH3, alkyl O-C-O, and O-alkyl functional groups, exercised a significant effect on the composition of the bacterial community at different temperatures during decomposition—results that extend our understanding of bacterial communities associated with the decomposition of straw in agro-ecosystems and of the effects of temperature and chemical properties of the decomposing straw and soil on such communities.

Differences in Chemical Composition of Soil Organic Carbon Resulting From Long-Term Fertilization Strategies

Chemical composition of soil organic carbon (SOC) is central to soil fertility. We hypothesize that change in SOC content resulting from various long-term fertilization strategies accompanies the shift in SOC chemical structure. This study examined the effect of fertilization strategies along with the time of fertilizer application on the SOC composition by 13C nuclear magnetic resonance (NMR) spectroscopy. The soils (Aquic Inceptisol) subjected to seven fertilizer treatments were collected in 1989, 1999 and 2009, representing 0, 10 and 20 years of fertilization, respectively. The seven fertilizer treatments were (1–3) balanced fertilization with application of nitrogen (N), phosphorus (P) and potassium (K) including organic compost (OM), half organic compost plus half chemical fertilizer (1/2OM), and pure chemical NPK fertilizer (NPK); (4–6) unbalanced chemical fertilization without application of one of the major elements including NP fertilizer (NP), PK fertilizer (PK), and NK fertilizer (NK); and (7) an unamended control (CK). The SOC content in the balanced fertilization treatments were 2.3–52.6% and 9.4–64.6% higher than in the unbalanced fertilization/CK treatments in 1999 and 2009, respectively, indicating significant differences in SOC content with time of fertilizer application between the two treatment groups. There was a significantly greater proportion of O-alkyl C and a lower proportion of aromatic C in the balanced fertilization than in unbalanced fertilization/CK treatments in 1999, but not in 2009, because their proportions in the former treatments approached the latter in 2009. Principal component analysis further showed that the C functional groups from various fertilization strategies tended to become compositionally similar with time. The results suggest that a shift in SOC chemical composition may be firstly dominated by fertilization strategies, followed by fertilization duration.