[Characterization of soil calcium carbonate using mid-infrared photoacoustic spectroscopy].

The mid-infrared photoacoustic spectra of CaCO3 was determined and characterized, and multi-calibration methods of principal component regression (PCA), partial least squares regression (PLSR), and GRNN artificial neural network were applied to quantitative analysis of soil carbonate. The results showed that abundant absorptions were found in the mid-infrared photoacoustic spectra of CaCO3, especially the very strong band at the wavenumber of 1450 cm(-1), in which there was few interferences, and could be used as spectral indicator of soil carbonate; the calibration results were good or excellent with the three chemometric methods, in which PLSR and GRNN modeling were excellent with a R2 more than 0.9, and PCA modeling was good with a R2 of 0.847; the validation results showed that PLSR and PCA modeling were excellent with higher R2 values ( > 0.9), and GRNN was also very satisfied with a R2 of 0. 882. Totally, PLSR modeling was the best with RPD values more than 3.0, indicating its strong potential in the prediction of soil carbonate.

[Evaluation of nutrient release profiles from polymer coated fertilizers using Fourier transform mid-infrared photoacoustic spectroscopy].

The acrylate-like materials were used to develop the polymer coated controlled release fertilizer, the nutrients release profiles were determined, meanwhile the Fourier transform mid-infrared photoacoustic spectra of the coatings were recorded and characterized; GRNN model was used to predict the nutrients release profiles using the principal components of the mid-infrared photoacoustic spectra as input. Results showed that the GRNN model could fast and effectively predict the nutrient release profiles, and the predicted calibration coefficients were more than 0.93; on the whole, the prediction errors (RMSE) were influenced by the profiling depth of the spectra, the average prediction error was 10.28%, and the spectra from the surface depth resulted in a lowest prediction error with 7.14%. Therefore, coupled with GRNN modeling, Fourier transform mid-infrared photoacoustic spectroscopy can be used as an alternative new technique in the fast and accurate prediction of nutrient release from polymer coated fertilizer.

[Study on the soil mid-infrared photoacoustic spectroscopy].

Infrared photoacoustic spectroscopy (PAS) is a new style to obtain data based on photoacoustic theory. Photoacoustic thoeory is based on the absorption of electromagnetic radiation by analyte molecules, and the absorbed energy is measured by detecting pressure fluctuations in the form of sound waves or shock pulses. In contrast to conventional absorption spectroscopy, PAS allows the determination of absorption coefficients over several orders of magnitude, even in very black and strongly scattering soil samples. Red soil, fulvic soil and paddy soil were collected from Fengqiu National Ecological Experimental Station, Yingtan Red Soil Experimental Station, and Changshu Ecological Experimental Station, respectively. These soil samples were used as experimental materials to characterize the Fourier transform mid-infrared photoacoustic spectra (FTIR-PAS). Compared with infrared transmittance spectra and reflectance spectra, the testing of FTIR-PAS spectra was very fast and convenient without any pr-treatment, and there were more abundant absorptions as well as appropriate absorption values in the spectra; The main soil components (kaolin, bentonite, sand and CaCO3) also showed several strong absorptions with specific characteristics in the spectra; Further more, the interference of water with the PAS spectra was significantly smaller than that with reflectance spectra. Therefore, the soil properties could be better characterized by FTIR-PAS. The principal components analysis based on the FTIR-PAS spectra indicated that there were two main principal components (PCA1, PCA2) which contained 98.17% variance of the spectra, and the two-dimensionol distribution was made by plotting these two principal components to classify the soil type, and the results indicated that this distribution could be applied to distinguish soil type, which provided new technique for soil identification as well as further quantitative analysis in soil science.

Response of rice (Oryza sativa) with root surface iron plaque under aluminium stress.

BACKGROUND AND AIMS: Rice (Oryza sativa) is an aquatic plant with a characteristic of forming iron plaque on its root surfaces. It is considered to be the most Al-tolerant species among the cereal crops. The objective of this study was to determine the effects of root surface iron plaque on Al translocation, accumulation and the change of physiological responses under Al stress in rice in the presence of iron plaque. METHODS: The japonica variety rice, Koshihikari, was used in this study and was grown hydroponically in a growth chamber. Iron plaque was induced by exposing the rice roots to 30 mg L(-1) ferrous iron either as Fe(II)-EDTA in nutrient solution (6 d, Method I) or as FeSO(4) in water solution (12 h, Method II). Organic acid in root exudates was retained in the anion-exchange resin and eluted with 2 m HCl, then analysed by high-performance liquid chromatography (HPLC) after proper pre-treatment. Fe and Al in iron plaque were extracted with DCB (dithionite-citrate-bicarbonate) solution. KEY RESULTS AND CONCLUSIONS: Both methods (I and II) could induce the formation of iron plaque on rice root surfaces. The amounts of DCB-extractable Fe and Al on root surfaces were much higher in the presence of iron plaque than in the absence of iron plaque. Al contents in root tips were significantly decreased with iron plaque; translocation of Al from roots to shoots was significantly reduced with iron plaque. Al-induced secretion of citrate was observed and iron plaque could greatly depress this citrate secretion. These results suggested that iron plaque on rice root surfaces can be a sink to sequester Al onto the root surfaces and Fe ions can pre-saturate Al-binding sites in root tips, which protects the rice root tips from suffering Al stress to a certain extent.

[Effect of monocalcium phosphate and potassium chloride on nitrogen leaching in paddy soil].

In this article, influence of monocalcium phosphate and potassium chloride application on nitrogen leaching in paddy soil of Taihu region was studied by soil column leaching. The results showed that nitrate nitrogen was the main component of nitrogen leaching without urea application which accounts for 93.39 percent of total nitrogen leaching (including urea, ammonium, and nitrate nitrogen). Amounts of urea, ammonium, and nitrate nitrogen in leachates increased significantly after urea application which account for 3.95, 15.25, and 80.80 percent of total nitrogen leaching respectively and for 0.26, 0.80, and 2.54 percent of applied nitrogen respectively. Amounts of urea, ammonium, and nitrate nitrogen in leachates were enhanced prominently by monocalcium phosphate or potassium chloride which are 4.54, 24.11, 71.34, and 3.45, 24.53, 72.02 percent of total nitrogen leaching respectively, and which are 0.39, 1.86, 3.34, and 0.32, 2.12, 4.06 percent of applied nitrogen separately. There is interactive influence on nitrogen leaching after application of monocalcium phosphate and potassium chloride together, and amounts of urea, ammonium, and nitrate nitrogen were 4.10, 27.35, and 68.55 percent of total nitrogen leaching, and 0.42, 2.60, and 4.26 percent of total applied nitrogen respectively. The leaching order of different form nitrogen followed as urea N > ammonium N > nitrate N, and leaching amounts of different form nitrogen followed as urea N < ammonium N < nitrate N.