Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were...
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Rice-paddies are regarded as one of the main agricultural sources of N 2O and NO emissions. To date, however, specific N2O and NO production pathways are poorly understood in paddy soils. ^15N-tracing experiments were carded out to investigate the processes responsible for N2O and NO production in two paddy soils with substantially different soil properties. Laboratory incubation experiments were carried out under aerobic conditions at moisture contents corresponding to 60% of water holding capacity. The relative importance of nitrification and denitrification to the flux of NaO was quantified by periodically measuring and comparing the enrichments of the N2O, NH^-N and NO3-N pools. The results showed that both N2O and NO emission rates in an alkaline paddy soil with clayey texture were substantially higher than those in a neutral paddy soil with silty loamy texture. In accordance with most published results, the ammonium N pool was the main source of N2O emission across the soil profiles of the two paddy soils, being responsible for 59.7% to 97.7% of total N2O emissions. The NO3-N pool of N2O emission was relatively less important under the given aerobic conditions. The rates of N2O emission from nitrification (N2On) among different soil layers were significantly different, which could be attributed to both the differences in gross N nitrification rates and to the ratios of nitrified N emitted as NzO among soil layers. Furthermore, NO fluxes were positively correlated with the changes in gross nitrification rates and the ratios of NO/N2O in the two paddy soils were always greater than one (from 1.26 to 6.47). We therefore deduce that, similar to N2O, nitrification was also the dominant source of NO in the tested paddy soils at water contents below 60% water holding capacity.
The Sino-German research collaboration project,"Recycling of organic residues from agricultural and municipal origin in China"(2008–2012),comprising different interdisciplinary research groups,and also German small a...
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The Sino-German research collaboration project,"Recycling of organic residues from agricultural and municipal origin in China"(2008–2012),comprising different interdisciplinary research groups,and also German small and medium-sized enterprises,aimed at developing integrated strategies and solutions for the recycling of organic residues in *** an intensive crop-livestock agricultural region in the Shunyi District of Beijing,five typical cropping systems were *** research was conducted in the form of analyses of phosphorus(P)in soil,plants,animal feed,animal products,manures,mineral and organic fertilizers and the derivation of the corresponding nutrient balances and P *** mean annual P balance surplus was492 kg·ha–1·yr–1 P for the vegetable production system,significantly higher(P30 mg·kg–1)that can lead to increased risk of P loss was exceeded in all five cropping *** feed additives,the"natural background value"(Chinese Environmental Quality Standard for Soils)of copper and zinc in topsoils was exceeded at several *** for several substances in the veterinary antibiotic classes of sulfonamides,tetracyclines,and fluoroquinolones revealed widespread topsoil *** livestock densities were 10.6 livestock units per ha arable land in *** husbandry is increasingly conducted in large operations,making traditional ways of reuse difficult to *** three management systems for treatment of organic
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