[Show abstract][Hide abstract] ABSTRACT: We investigated the size distribution of water-stable aggregates and the soil carbon, nitrogen and phosphorus concentration over aggregate size fractions based on a long-term (1990-2006) fertilization experiment in a reddish paddy soil. The results showed that the largest water-stable aggregate (WSA) (>5 mm) and the smallest WSA (<0.25 mm) took up the first largest proportion (38.3%) and the second largest proportion (23.3%), respectively. Application of organic materials increased the proportion of the large WSA (>2 mm) and decreased the proportion of the small WSA (<1 mm), resulting in an increase in the mean weight diameter of WSA, whereas application of chemical fertilizer had little effect. Application of organic materials, especially combined with chemical fertilizers, increased total carbon, nitrogen and phosphorus concentrations in all sizes of WSA, and total carbon, nitrogen and phosphorus were prone to concentrate in the large WSA. Further more, application of organic materials improved the supply effectiveness of available phosphorus, whereas had little influence on the labile carbon in WSA. Application of chemical fertilizers improved concentrations of total and available phosphorus in all sizes of WSA, whereas had little influence on total carbon and nitrogen contents. Economical fertilization model maintained the soil fertility when compared with full dose of chemical fertilizers, indicating that using organic materials could reduce chemical fertilizers by about one third.
No preview · Article · Dec 2011 · Agricultural Sciences in China
[Show abstract][Hide abstract] ABSTRACT: With a reddish paddy soil as test materials, soil profile nitrogen storage in long-term different fertilization system (1990-2006) have been investigated. The result indicated that recycling of organic matter significantly increased the soil profile C storage (ranged from 57.7 to 66.2 t/hm2), and it was increased by 18.7-27.2 t/hm2 compared with the soil profile C storage of 1990. But it was increased by 5.4 t/hm2 with only application of chemical fertilizers. Saturated carbon storage of paddy soils was 84.0 t/hm2, and the C sequestration potential ranged from 17.8-43.7 t/hm2 compared with the current soil profile carbon storage. The result showed that there was a significant relationship between soil bulk density and depth changes of profile soil. The organic C storage would be greatly underestimated by 20.6% or 11.3% if we only take 20 cm or 23 cm as the standard depth in the estimating method for organic C storage, it also would be underestimated the difference of treatments. The combined application of chemical fertilizer and organic matter is optimal for agricultural field based onsoil organic C storage and the carbon sequestration potential.
No preview · Article · Jun 2009 · Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.]
[Show abstract][Hide abstract] ABSTRACT: Two representative catchments, Wuchuang catchment and Xiandu catchment, were selected from Jiulong River Watershed as study areas to trace sources of nitrate in surface water by using 15N isotope technique. In the spring of 2005, the surface water samples were twice collected from the catchments and determined for dissolved total nitrogen (DTN), nitrate nitrogen (NO3(-)-N), ammonia nitrogen (NH4+-N) and delta 15N value of nitrate. The results showed that in the samples from Xiandu catchment, the concentration ranges of DTN, NO3(-)-N and NH4+-N were 1.47-5.31 mg/L, 0.83-4.05 mg/L and 0.21-0.36 mg/L respectively, and the delta 15N values of nitrate ranged from 2.54 per thousand to 7.92 per thousand; in the samples from Wuchuang catchment, the concentration ranges of DTN, NO3(-)-N and NH4+-N were 1.14-5.56 mg/L, 0.96-1.46 mg/L and 0.12-1.28 mg/L respectively, and the delta 15N values of nitrate were between -0.19 per thousand and 5.89 per thousand. In contrast with the typical ranges of delta 15N isotopic signature of nitrate from different sources and in consideration of the information of local crop planting circumstances and application of fertilizers, the data indicated that the first, the nitrate in the surface water of Xindu catchment mainly came from inorganic fertilizers and soil organic nitrogen, and some originated from organic fertilizers; the second, the nitrate in the surface water of Wuchuang catchment mostly flowed from inorganic fertilizers and soil organic nitrogen, and few derived from organic fertilizers; the third, the sources of nitrate varied with the sampling location and time and were dependent on the kinds of local crops and their planting seasons.
No preview · Article · Jul 2008 · Huan jing ke xue= Huanjing kexue / [bian ji, Zhongguo ke xue yuan huan jing ke xue wei yuan hui "Huan jing ke xue" bian ji wei yuan hui.]