Search

Compost application can enhance soil fertility and is consequently presumed to increase crop production in Japan's paddy-upland rotation fields. This study aimed to evaluate the effects of rice straw compost (RSC) application on available soil nitrogen (Av-N) levels and rice and soybean plants in a paddy-upland rotation field using data obtained from a long-term field experiment. Data collected between 2005 and 2020 were analyzed from a long-term paddy rice – upland soybean rotation field. The experimental design employed a split-plot arrangement, with RSC application (with and without RSC) representing the whole plot, N fertilizer application (no nitrogen vs. standard fertilizer) representing the split-plot, and years representing the replication factor. The datasets included eight years of rice and soybean cultivation, and the chemical properties of postharvest soil spanned 16 years. The data was analyzed via analysis of variance. Applying RSC increased the Av-N concentration significantly by 63%–67%. The RSC application significantly increased the N concentration in rice shoots at the mature stage by 8%–12% but decreased it in soybean shoots after the seed emergence stage by 4%–8%. Consequently, the rice yield displayed clear responses to RSC application, whereas the soybean yield did not. The lack of soybean yield response might be due to an inhibitory effect of the Av-N gain attributable to the RSC application on biological nitrogen fixation. While applying compost can enhance Av-N content as well as rice productivity in paddy-upland rotation fields, its impact on soybean productivity requires careful evaluation. [ABSTRACT FROM AUTHOR]

To investigate how the long-term application of inorganic fertilizer and organic amendments affects the turnover rates of organic matter in physico-chemically fractionated components in paddy soils and how their rates are related to their amounts, we studied the effect of variable management of inorganic fertilizer and organic amendments for > 50 years on the ∆14C values of accumulated soil organic carbon (SOC) in fractionated components of 5 soil samples from three paddy fields. SOC was fractionated into four components based on their physico-chemical properties: (1) light fraction (LF) derived from plant residues, (2) heavy fraction (HF) containing stable aggregates, (3) oxidizable fraction (OxF) and (4) non-oxidizable fraction (NOxF) forming organo-mineral complexes with fine-textured minerals. The ∆14C values were determined by accelerator mass spectrometry using graphitized samples. The ∆14C values of SOC in NOxF (from −305‰ to − 90.5‰) were much lower than those of HF (from −123‰ to − 3.7‰) and OxF (from −215‰ to 21.0‰). Lowest values for NOxF suggested slowest turnover rates as expected, and higher and comparable values for OxF and HF implied much faster turnover rates of SOC in OxF compared with upland soils. This could be one of the characteristics of SOC dynamics in paddy soils, probably reflecting repeated puddling of plow layer soils. ∆14C values in all the fractions increased in response to the application of inorganic fertilizer and organic amendments, suggesting faster turnover rate. Soils with clayey and weathered characteristics had the lowest ∆14C values, or slowest turnover rates among the study fields. The relationship between the ∆14C value and the amount of accumulated C for HF, OxF and NOxF indicated that the more the SOC accumulated, the faster the turnover rate of the SOC was, regardless of the fractions, and the relationship of the HF was considerably different from those of OxF and NOxF. In conclusion, these results can be the basis for understanding the C dynamics and for improving soil fertility status and soil C sequestration in paddy soils. [ABSTRACT FROM AUTHOR]

To reduce the availability of soil cadmium (Cd) to soybeans (Glycine max(L.) Merr.), we employed a liming by partial mixing (PM) technique in two drained paddy fields on Gray Lowland soils, which had 0.1 mol L–1hydrochloric acid-extractable Cd concentrations as high as 1.08 and 1.40 mg kg–1. Among the different application methods tested, PM application (PM2) using a width of 20 cm and a depth of 20 cm was found to be most appropriate for reducing the seed Cd concentration and to obtain the optimum yield at Site A. Under PM2, a liming rate of 38% of that for broadcast incorporated into the surface 15 cm layer (Bc) was suitable to reduce the seed Cd concentration at Site A, whereas the lime rate with PM2 was set at 50% of that for Bc (PM2-50) at Site B due to the higher availability of soil Cd. The root system was limited within the range of lime and fertilizer application for PM2 as well as PM2-50; thus, the lime and fertilizer were supplied successfully to the rooting zone. The soil pH value was lower under PM2 at Site A and PM2-50 at Site B compared with Bc, whereas the seed Cd concentration was lower for PM2 and PM2-50. This may be explained by the intensive uptake of calcium and magnesium with PM2 as well as PM2-50. The seed Cd concentration in the cultivar “Ryuhou” at the target pH of 6.5 was approximately 30% lower with PM2-50 than Bc at Site B. In addition, the average seed Cd concentrations in one cultivar and two lines, characterized by the lower Cd uptake with higher retention in roots and higher accumulation in leaves, were approximately 40% lower compared with “Ryuhou.” Thus, the combination of liming with PM2-50 at the target pH of 6.5 and a low-Cd cultivar (or lines) minimized the seed Cd concentration. The highest seed Cd concentration was found in the first year of soybean cultivation, which was considered to be caused by the release of Cd from organic nitrogen compounds during the nitrogen mineralization process. [ABSTRACT FROM PUBLISHER]

Abstract: In order to get a better understanding regarding the structure of charged film of membranes, two kinds of the composite Collodion membrane (C), and Nafion one (N) were prepared and characterized by systematic and comparative studies. The Nafion (fluorocarbon polymer) and Collodion blended with Nafion in the ratio of (CN5:5) composite solutions were used to produce thin membrane films on Au electrodes. The present study indicated that better diffusion coefficient of redox substances can be achieved by blending the Nafion solution with ionic group to Collodion solution compared Nafion only. Diffusion coefficient of MV2+ and FcDM in the blended Nafion/Collodion showed higher values compared to that Nafion. The uptake of neutral species of ferrocenedimethanol (FcDM), positively charged species of methyl viologen (MV2+) and negatively charged of potassiumferrocyanide, [Fe(CN)6]4- ions were studied by cyclic voltammetry (CV), chronopotentiometry (CP) and chronocoulometry (CC). The diffusion coefficient values of MV2+ of the blended composite, CN5:5 membranes are about twice (0.43×10-6cm2/s) that of Nafion based membrane (0.27×10-6cm2/s). While the diffusion coefficients of FcDM of the blended, CN5:5 and Nafion based membranes are in the order of 2.4 and 1.8×10-6cm2/s, respectively. This means that the diffusion of positively charged species, MV2+ was decreased in the membrane matrix compared to neutral species, FcDM. It also indicates that the concentrations of the MV2+ are higher than that of the neutral species, FcDM, in both blended (CN5:5) and Nafion membranes. This may attributed to the existence of interaction between SO3- functional groups of fluorocarbon polymer and MV2+ that led to mobility restriction of MV2+compared to neutral FcDM one, i.e. diffusion of MV2+ was decreased. It was found that the negatively species, [Fe(CN)6]4- exist in surface of the blended membrane (CN5:5) slightly, but not in Nafion one due to the electrostatic repulsion effect between SO3- functional groups of flourocarbon polymer and negatively species, [Fe(CN)6]4-. This means that diffusion of [Fe(CN)6]4- species was not clearly observed. As a whole, the blended membranes indicated membrane performance comparable to the commercial ion-exchange membranes. [Copyright &y& Elsevier]