Fertilizer In Paddy Fields Research Articles

Emissions of N2O and NH3, and nitrogen leaching from direct seeded rice under different tillage practices in central China

Tillage practices affect the fate of fertilizer nitrogen (N) through influencing transformations of N, but few studies have examined N2O and NH3 emissions, and N leaching from different rice tillage systems. Thus the objective of this study was to assess N2O emission, NH3 volatilization and N leaching from direct seeded rice in conventional tillage (CT) and no-tillage (NT) production systems in the subtropical region of China during the 2008 and 2009 rice growing seasons. Treatments were established following a split-plot design of a randomized complete block with tillage practices as the main plot and N fertilizer level as the sub-plot treatment, and there were four treatments: NT+no fertilizer (NT0), CT+no fertilizer (CT0), NT+compound fertilizer (NTC) and CT+compound fertilizer (CTC), respectively. Results showed that N fertilization significantly increased (p<0.01) N2O emissions, NH3 volatilization and N leaching from rice fields in both years. In general, there was no significant difference in N2O emissions and NH3 volatilization between NT0 and CT0 in both years, while NTC had significantly higher (p<0.05) N2O emissions and NH3 volatilization compared to CTC. Over the two rice growing seasons, NTC showed 32% and 47% higher N2O emissions, and 29% and 52% higher NH3 losses than CTC. Higher (p<0.05) N2O emissions from NTC than CTC were presumably due to higher soil organic C and greater denitrification. Total N and NO3− concentrations were higher (p<0.05) in CTC than NTC, but larger volumes of percolation water in NTC than CTC resulted in no significant difference in leakage of total N and NO3−. Hence, application of N fertilizer in combination with NT appeared to be ineffective in reducing N losses from N fertilizer in paddy fields.

Study of the Mathematical Models for Operation of Liquid Fertilizer Application

Biogas from methane fermentation is anticipated for use as an alternative energy resource to fossil fuel. However, a problem persists related to treatment of wastewater generated in methane fermenters. Consequently, the wastewater must be processed additionally to reduce environmental load when released. The most important problem is the treatment raises the total running cost of fermenters. To lower this cost, application of the wastewater as liquid fertilizer in paddy fields without the treatment has been studied. However, in rice cropping, the suitable periods for application are limited. This study is intended to produce models for estimating working hours in each paddy field to construct an effective operation plan of a slurry injector for liquid fertilizer. Working times in the paddy fields were investigated for two cases of liquid fertilizer application: Nantan and Yamaga. Two simple models can be constructed; which model should be used can be determined according to the paddy field shape.

水田における無機態窒素（ＴＩＮ）の浸透流出モデルに関する検討

A model of TIN infiltration in sandy soil paddy fields was developed in this paper. It incorporates TIN uptake of fertilizer by paddy, denitrification, plankton growth, soil adsorption and desorption of fertilizer in paddy fields, decomposition of paddy litter, plankton and organic material in soil. The results calculated from the model were in good agreement with the measured values, which demonstrated that the model was useful in predicting the infiltration and runoff of TIN in paddy fields.Runoff loading was derived from the model simulation (from Jun. 15 to Sep. 30). The infiltration loading was 3.06 g·m-2, which was about 30.5% of the total amounts of input feritilizer (10.3 g·m-2) for paddy.

DECOMPOSITION OF BLUE-GREEN ALGAE AS EFFECTED BY THE ACTION OF SOIL BACTERIA

The decomposition of the nitrogen-fixing blue-green algae, Tolypothrix tenuis, Calothrix brevissima, Nostoc muscorum and Anabaenopsis circularis, brought about by the action of various soil bacteria was examined. A certain strain of Bacillus subtilis was found to give the most active production of ammonia; about 40 per cent of the algal nitrogen being converted to ammonia within 10 days of incubation. Practically no production of nitrogenous compounds other than ammonia was observed. On the basis of these results, the varying efficacy of blue-green algae as fertilizer in paddy fields was discussed.