Aung Zaw Oo

Growth and 137Cs uptake of four Brassica species influenced by inoculation with a plant growth-promoting rhizobacterium Bacillus pumilus in three contaminated farmlands in Fukushima prefecture, Japan

The effectiveness of the plant growth-promoting rhizobacterium Bacillus pumilus regarding growth promotion and radiocesium ((137)Cs) uptake was evaluated in four Brassica species grown on different (137)Cs contaminated farmlands at Fukushima prefecture in Japan from June to August 2012. B. pumilus inoculation did not enhance growth in any of the plants, although it resulted in a significant increase of (137)Cs concentration and higher (137)Cs transfer from the soil to plants. The Brassica species exhibited different (137)Cs uptake abilities in the order Komatsuna>turnip>mustard>radish. TF values of (137)Cs ranged from 0.018 to 0.069 for all vegetables. Komatsuna possessed the largest root surface area and root volume, and showed a higher (137)Cs concentration in plant tissue and higher (137)Cs TF values (0.060) than the other vegetables. Higher (137)Cs transfer to plants was prominent in soil with a high amount of organic matter and an Al-vermiculite clay mineral type.

Effect of dolomite and biochar addition on N2O and CO2 emissions from acidic tea field soil

A laboratory study was conducted to study the effects of liming and different biochar amendments on N2O and CO2 emissions from acidic tea field soil. The first experiment was done with three different rates of N treatment; N 300 (300 kg N ha-1), N 600 (600 kg N ha-1) and N 900 (900 kg N ha-1) and four different rates of bamboo biochar amendment; 0%, 0.5%, 1% and 2% biochar. The second experiment was done with three different biochars at a rate of 2% (rice husk, sawdust, and bamboo) and a control and lime treatment (dolomite) and control at two moisture levels (50% and 90% water filled pore space (WFPS)). The results showed that dolomite and biochar amendment significantly increased soil pH. However, only biochar amendment showed a significant increase in total carbon (C), C/N (the ratio of total carbon and total nitrogen), and C/IN ratio (the ratio of total carbon and inorganic nitrogen) at the end of incubation. Reduction in soil NO3--N concentration was observed under different biochar amendments. Bamboo biochar with the rates of 0.5, 1 and 2% reduced cumulative N2O emission by 38%, 48% and 61%, respectively, compare to the control soil in experiment 1. Dolomite and biochar, either alone or combined significantly reduced cumulative N2O emission by 4.6% to 32.7% in experiment 2. Reduction in N2O production under biochar amendment was due to increases in soil pH and decreases in the magnitude of mineral-N in soil. Although, both dolomite and biochar increased cumulative CO2 emission, only biochar amendment had a significant effect. The present study suggests that application of dolomite and biochar to acidic tea field soil can mitigate N2O emissions.

Within field spatial variation in methane emissions from lowland rice in Myanmar

An assessment of within field spatial variations in grain yield and methane (CH4) emission was conducted in lowland rice fields of Myanmar. Two successive rice fields (1st field and 2nd field) were divided into fertilized and non-fertilized parts and CH4 measurements were conducted at the inlet, middle and outlet positions of each field. The results showed that CH4 emissions at non-fertilized parts were higher than those at fertilized part in both rice fields. The average CH4 emissions ranged from 8.7 to 26.6 mg m-2 h-1 in all positions in both rice fields. The spatial variation in CH4 emission among the positions was high in both rice fields with the highest emissions in the outlet of the 1st field and the inlet of the 2nd field. The CH4 emissions at these two positions showed 2 - 2.5 times higher than those at other positions in both rice fields. Stepwise regression analysis indicates that soil total carbon content is the primary factor for CH4 emission. The average CH4 emissions during rice growing season were 13.5 mg m-2 h-1 for the 1st field and 15.7 mg m-2 h-1 for the 2nd field. Spearman rank order correlation analysis showed that CH4 emission was significantly and positively correlated with soil temperature, surface water depth and negatively correlated with soil redox potential. The result indicated that high within field spatial variation in CH4 emissions required different site specific management practices to mitigate CH4 emissions in lowland paddy rice soil.

Influence of Gypsum Amendment on Methane Emission from Paddy Soil Affected by Saline Irrigation Water

To investigate the influence of gypsum application on methane (CH4) emission from paddy rice soil affected by saline irrigation water, two pot experiments with the rice cultivation were conducted. In pot experiment (I), salinity levels 30 mMNaCl (S30) and 90 mMNaCl (S90), that showed maximum and minimum CH4 production in an incubation experiment, respectively, were selected and studied without and with application of 1 Mg gypsum ha-1(G1). In pot experiment (II), CH4 emission was investigated under different rates of gypsum application: 1 (G1), 2.5 (G2.5) and 5 (G5) Mg gypsum ha-1 under a non-saline and saline condition of 25 mMNaCl (S25). In experiment (I), the smallest CH4 emission was observed in S90. Methane emission in S30 was not significantly different with the non-saline control. The addition of gypsum showed significant lower CH4 emission in saline and non-saline treatments compared with non-saline control. In experiment (II), the CH4 emissions in the saline treatments were not significantly different to the non-saline treatments except S25-G5. However, our work has shown that gypsum can lower CH4 emissions under saline and non-saline conditions. Thus, gypsum can be used as a CH4 mitigation option in non-saline as well as in saline conditions.