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Surface mulch is regarded as an effective manner to reducing soil water evaporation, but limited with the adverse influence of plastic film mulch on agro-ecosystems. In this paper, liquid films were prepared with the foundation of kelp as a bio-material. The results showed that the films prepared with the mixture of kelp and polyvinyl alcohol (PA) had superimposed layering structure with tiny pores and gaps, and were stable as well as degradable under field water conditions. The results of the simulative experiments with both of aquic sand-loamy soil and yellow silt-loamy soil that mulching with the film of the mixture of kelp and polyvinyl alcohol (PA) could significantly (P<0.01) reduce water evaporation from soil. It was also found that mulching with the liquid films could increase the water retention capacity of the tested soils. As the initial material – kelp is available, the application of the developed liquid film based on kelp for efficient soil moisture management in agricultural production should be recommended.

A greenhouse experiment was conducted with a specially designed apparatus consisting of an upper and lower chamber where the treatment with rice was carried out (treatment 1). The apparatus also had a single chamber where treatment 2, without rice plants, was carried out. The scope of this study was to elucidate the influence of rice plant growth on gaseous N losses as N 2 and N 2O produced by nitrification-denitrification in a flooded soil fertilized with (NH 4) 2SO 4 (with 56.50 atom% 15N). Gas samples were withdrawn weekly and analyzed for (N 2 + N 2O)- 15N losses by mass spectrometer and for N 2O by gas chromatograph. The gaseous (N 2 + N 2O)- 15N losses of the treatment with rice plants were significantly ( P =0.01) higher than those of the treatment without rice plants, as were the amounts of N 2O emitted. Rice plants facilitate the efflux of N 2 and N 2O from soil to atmosphere, as about half of the total gaseous 15N loss as N 2 and N 2O was found in the upper chamber. The proportion of N 2O- 15N to (N 2 + N 2O)- 15N in the upper chamber was 10.56%, much higher than that of the lower chamber in treatment 1 and the headspace of treatment 2.

Lead concentrations in roots, stems and leaves of accumulating and non-accumulating ecotypes ofSedum alfredii(Hance) were studied through a hydroponic experiment with different Pb concentrations supplied as Pb(NO3)2. Lead concentrations in leaves and stems of the accumulating ecotype were 4–9 times and 3–5 times those of the non-accumulating ecotype, and Pb-accumulated amounts in stems and leaves of the accumulating ecotype were 4–9 times and 8–11 times higher than those of the non-accumulating ecotype, respectively. The results indicated that the accumulating ecotype had better ability to transport Pb from roots to shoots. The subcellular distributions of Pb in the root, stem and leaf tissues were studied using sucrose differential centrifugation. Approximately 50% of Pb contents was found to be associated with the cell wall fraction in stems of the accumulating ecotype and the percentage increased to 80% both in roots and leaves, no matter when plants were grown with different levels of Pb. The results indicated that the distribution of Pb on cell walls of the accumulating ecotype could mainly account for the high tolerance to Pb.