Hideto Ueno

Nitrogen dynamics in paddy soil applied with various 15N-labelled green manures

The effects of 15N-labelled green manure (GM) application on rice yield and N uptake were investigated and compared with those of inorganic fertilizer (IF) and no fertilizer (NF) application. Nine GMs (white clover, Chinese milk vetch, hairy vetch, crimson clover, oats, rye, Italian ryegrass, white mustard, lacy phacelia) were either incorporated into or surface-applied on paddy soil. Among the nine GM treatments, the rice yield and N uptake tended to be higher in the white clover and hairy vetch treatments. The rice N uptake efficiency from the applied N source was highest in the incorporated hairy vetch (56%), followed by IF (52%), and incorporated white clover (44%), whereas for the other treatments there were no significant differences. The mineral fertilizer equivalent values of hairy vetch and white clover in case of the incorporation were 108% and 84%, respectively. Therefore, hairy vetch and white clover seem to be the most efficient organic N source as alternatives to inorganic N fertilizers. The N uptake efficiency of rice and residual N in soil derived from GM were higher in the incorporation treatments than that in the surface-applied treatments, indicating that N losses from the soil-plant system were lower with the incorporation.

Nucleotide sequence and expression of a gene (chiB) for a chitinase from Streptomyces lividans

Abstract Streptomyces lividans 66 has three distinct chitinase genes. The nucleotide sequence of one gene for chitinase ( chiB ) from S. lividans was determined, and the structure and expression of the gene were analyzed. The structural gene consisted of 1,830 bp encoding 610 amino acid residues. Comparison of the deduced amino acid sequence of chitinase B with those of chitinases of other bacteria revealed a domain structure from N-terminal to C-terminal of the following order: signal peptide, substrate-binding domain, type III repeating unit, and catalytic domain. When the three chitinase genes from S. lividans ( chiA, chiB, chiC ) were compared with one another, the overall similarities between the nucleotide sequences of chiA and chiB and between the amino acid sequences deduced from them were found to be 49% and 59%, respectively, whereas chiC showed no relatedness to either chiA or chiB . It is, therefore, suggested that chiA and chiB diverged relatively recently. chiB of S. lividans was found to be more than 90% similar to chi01 of Streptomyces olivaceoviridis in both nucleotide and amino acid sequences, and chiC of S. lividans was found to be almost identical to chtA of S. plicatus . Southern hybridization studies conducted using chiA, chiB , and chiC of S. lividans as probes against genomic DNA from several Streptomyces strains revealed that these genes of S. lividans are distributed and highly conserved among the genus Streptomyces . Although a pair of direct repeat sequences similar to those found in the promoter region of other chitinase genes of Streptomyces are present in chiB , the motif is least conserved in chiB . The level of expression of chiB was shown to be lower than that of either chiA or chiC . It is assumed that chitinases A and C play a major role in chitin degradation in S. lividans .

Uptake of carbon and nitrogen through roots of rice and corn plants, grown in soils treated with 13C and 15N dual-labeled cattle manure compost

Abstract Nitrogen and carbon dynamics in paddy and upland soils for rice cultivation and in upland soil for corn cultivation was investigated by using 13C and 15N dual-labeled cattle manure compost (CMC). In a soil with low fertility, paddy and upland rice took up carbon and nitrogen from the CMC at rates ranging from 0.685 to 1.051% of C and 17.6–34.6% of N applied. The 13C concentration was much higher in the roots than in the plant top, whereas the 15N concentration differed slightly between them, indicating that organic carbon taken up preferentially accumulated in roots. The 13C recovery in the plant top tended to be higher in upland soil than in paddy soil, whereas 15N applied was recovered at the same level in both paddy and upland soils. In the experiment with organic farming soil, paddy rice took up C and N from the CMC along with plant growth and the final recovery rates of 13C and 15N were 2.16 and 17.2% of C and N applied. In the corn experiment, a very large amount of carbon from the CMC was absorbed, accounting for at least 7 times value for rice. The final uptake rates of 13C and 15N reached about 13 and 10% of C and N applied, respectively. Carbon emission from the CMC sharply increased by 2 weeks after transplanting and the nitrogen emission was very low. It is concluded that rice and corn can take up an appreciable level of carbon and nitrogen from the CMC through roots.

Measurement of soil water flux in andisols at a depth below a root zone of about 1 Meter

Abstract A method which uses the pressure head to predict unsaturated hydraulic conductivity is presented to calculate the soil water flux in a field. Hydraulic conductivities in the primary drying and wetting processes were measured with core samples in the laboratory and the hysteresis between the hydraulic conductivity and pressure head was taken into account. Hydraulic gradients were measured every hour with tensiometers installed in the field. This method was applied to analyze the water movement at 94-cm depth in Hydric Hapludands. Downward or upward flow of water by summing soil water fluxes was examined using the water balance method. Amounts of downward flow determined by our method after heavy rain in a wet soil were slightly larger in the soybean plot but smaller in the bare plot than those obtained by the water balance method due to non-uniform infiltration. Water balance equation which used values of upward flow across a 94-cm depth estimated reasonably well the evapotranspiration from the so...

Inductive production of chitinolytic enzymes in soil microcosms using chitin, other carbon-sources, and chitinase-producing Streptomyces

Abstract The inductive production of chitinolytic enzymes (chitinase and N-acetylglucosaminidase) in soil microcosms by the amendment with various carbon sources and/or inoculation of chitinase producing Streptomyces sp., was examined. Chitinase activity in soil was measured by using 4-methylumbelliferyl (4MU) derivatives of N-acetyl-n-glucosamine (GlcNAc) oligom~rs as substrates, i.e., 4MU -chitobiose and 4MU -chitotriose, and N -acetylglucosaminidase activity by using 4MU-GlcNAc. The highest chitinase activity was attained by the amendment with chitin powder. GlcNAc and yeast extract also increased the chitinase activity significantly and incubation with glucose increased the chitinase activity only for 4MU-chitobiose. In contrast, the increase of the chitinase activity by other carbon sources including cellulose, xylan, laminarin, chitosan, and xylose was negligible. The ratio of chitinase activity for 4MU -chitobiose to that for 4MU-chitotriose in the soil varied with the substrate applied, suggesting that different types of chitinases were produced depending on the carbon-source added. Inoculation of Streptomyces sp. S-84, which produces a large amount of chitinase, stimulated the synthesis of chitinolytic enzymes in soil.

Nitrogen Uptake by Radish, Spinach and Chingensai from Composted Tea Leaves, Coffee Waste and Kitchen Garbage

A pot experiment was conducted to determine the effects of the application of composted tea leaves (TC), coffee waste (CC), and kitchen garbage (KC) on the nitrogen and nitrate accumulated in radish (Raphanus sativus L. cv. ‘radicula pers’), Chingensai (Brassica campestris L. cv. ‘Choyo No. 2’), and spinach (Spinacia oleracea L. cv. ‘Ban chu paruku’) as compared with the effect of inorganic 15N labeled fertilizer (IN) application. The compost was applied at the rate of 24 g kg−1 soil, corresponding to about 250 to 300 kg N ha−1; the A value method was used to estimate nitrogen uptake. Dry matter production was significantly higher in the IN and TC treatments than in the KC and CC treatments for all the species and tissue. Of the composts used, TC was most effective in increasing N uptake and N content in the vegetables. The composts derived N recovery as a percentage of total N uptake varied with plant species, 50.8%-62.9% in radish root, 35.3%-60.4% in radish leaf, 29.9%-48.2% in spinach leaf, and 31.3%-54.8% in Chingensai leaf. The N-use efficiencies of IN, TC, CC, and KC were 6.3%, 6.3%, 5.3%, and 6.6% in radish root; 13.6%, 9.7%, 8.4%, and 6.7% in radish leaf; 22.4%, 14.4%, 3.6%, and 5.8% in spinach leaf; and 61.2%, 39.5%, 25.5%, and 21.5% in Chingensai leaf, respectively. Nitrate accumulation in edible portions was highest in plants provided with IN as compared with those grown with composts, and nitrate content in radish root was markedly higher than that in the leaf. It is observed that the fate of compost derived N differed noticeably with vegetable species, plant part, and compost source.

Determination of Application Effects of Sewage Sludge on Growth, Soil Properties, and N Uptake in Komatsuna by using the Indirect 15N Isotope Method

Abstract: By using the indirect 15nitrogen (N) method, the application effects of sewage sludge (SS) on growth indices, yield, and nutrient uptake in Komatsuna (Brassica campestris var. perviridis) grown in a low fertility soil were investigated and compared with those of chemical fertilizer (CF) and no‐fertilizer (NF) treatments. The N‐use efficiencies of CF and SS were 19.7% and 12.1%, respectively, of the applied N. Therefore, the relative efficiency of the sewage sludge to chemical fertilizer was 61.5%. In comparison to NF and CF, the application of SS apparently increased the soil microbial activity, which was evaluated by measuring hydrolysis of fluorescein diacetate. After cultivation, the electrical conductivity (EC) of CF soil (0.175 dS m−1) was significantly higher than those of NF (0.067 dS m−1) and SS soils (0.057 dS m−1). The concentrations of phosphorus (P), calcium (Ca), and magnesium (Mg) in SS leaves were significantly higher than those in CF leaves; however, the concentration of potassium (K) was significantly lower in SS than in CF.

Effects of bamboo biochar application on global warming in paddy fields in Ehime prefecture, Southern Japan

ABSTRACT Biochar application can reduce global warming via carbon (C) sequestration in soils. However, there are few studies investigating its effects on greenhouse gases in rice (Oryza sativa L.) paddy fields throughout the year. In this study, a year-round field experiment was performed in rice paddy fields to investigate the effects of biochar application on methane (CH4) and nitrous oxide (N2O) emissions and C budget. The study was conducted on three rice paddy fields in Ehime prefecture, Japan, for 2 years. Control (Co) and biochar (B) treatments, in which 2-cm size bamboo biochar (2 Mg ha−1) was applied, were set up in the first year. CH4 and N2O emissions and heterotrophic respiration (Rh) were measured using a closed-chamber method. In the fallow season, the mean N2O emission during the experimental period was significantly lower in B (67 g N ha−1) than Co (147 g N ha−1). However, the mean CH4 emission was slightly higher in B (2.3 kg C ha−1) than Co (1.2 kg C ha−1) in fallow season. The water-filled pore space increased more during the fallow season in B than Co. In B, soil was reduced more than in Co due to increasing soil moisture, which decreased N2O and increased CH4 emissions in the fallow season. In the rice-growing season, the mean N2O emission tended to be lower in B (−104 g N ha−1) than Co (−13 g N ha−1), while mean CH4 emission was similar between B (183 kg C ha−1) and Co (173 kg C ha−1). Due to the C release from applied biochar and soil organic C in the first year, Rh in B was higher than that in Co. The net greenhouse gas emission for 2 years considering biochar C, plant residue C, CH4 and N2O emissions, and Rh was lower in B (5.53 Mg CO2eq ha−1) than Co (11.1 Mg CO2eq ha−1). Biochar application worked for C accumulation, increasing plant residue C input, and mitigating N2O emission by improving soil environmental conditions. This suggests that bamboo biochar application in paddy fields could aid in mitigating global warming.

Establishment of Rice Seedlings by Direct Sowing of Multiple Seed Pellets on Paddy Soil Covered with Legume Living Mulch

Received 29 October 2007. Accepted 16 November 2007. Corresponding author: N. Asagi (asagimao@agr.ehime-u.ac.jp, fax +81-89-993-3173). This work was supported by the Grant-in-Aid for Scientifi c Research by the Ministry of Education, Science, and Culture, Sports, Science and Technology of Japan (No. 14360041). Abbreviations : DAS, days after sowing; MSP, multiple seed pellet. Establishment of Rice Seedlings by Direct Sowing of Multiple Seed Pellets on Paddy Soil Covered with Legume Living Mulch

Effect of phenolic acids on the formation and stabilization of soil aggregates

ABSTRACT To examine the effects of phenolic acids, which are generated by the decomposition of cell walls in plant residues, and other constituents on the stability of soil aggregates, phenolic acids and carbohydrates were mixed into three different types of soil. After a 1-month incubation, the plot containing soil mixed with phenolic acids showed the greatest mean weight diameter of all the soils. In the treated soils, before incubation, the decline of saturated water permeability during continuous water percolation was mitigated in the plot containing soil mixed with phenolic acids compared with that in the other plots. Soil aggregates were synthesized with the addition of phenolic acids and carbohydrates using two methods (mixing and surface brushing) and were incubated for 153 days. The aggregate stability was greatest in the plots surface-brushed with phenolic acids for Andosol and gray lowland soil, whereas the aggregate stability was most stable in the plots mixed with phenolic acids for yellow soil. This difference in the effectiveness of application methods is rationalized by the densities of the active Al and Fe contents, the carbon content, and the specific surface area of the soils. The phenolic acids also affected sandy soil. In a similar experiment using a gray lowland soil, mixing a portion of p-coumaric acid into synthetic aggregates was found to shift the molecular weight distribution of substances to larger molecular weights, as determined by size exclusion chromatography of the liquid extracted from the aggregates, which was likely accompanied by an increase in aggregate stability. The effects of fungi and bacteria on soil long-term stability were not greater than those of phenolic acids. Our findings and previous results show that microorganisms aid in soil-aggregate formation during the early stages, and phenolic acids not only aid in the formation of aggregates but also strongly stabilize them.