Ultrahigh-pressure (UHP)metamorphism plays important roles in continental dynamics.Understanding of this process has been enhanced by the discovery of coesite and micro-diamond from supracrustal rocks [1].Such UHP min...Ultrahigh-pressure (UHP)metamorphism plays important roles in continental dynamics.Understanding of this process has been enhanced by the discovery of coesite and micro-diamond from supracrustal rocks [1].Such UHP mineral inclusions provide unequivocal evidence that the least dense part of the lithosphere can be buried to 100-150km or more,and then returned to the surface.Coesite,an ultrahigh-pressure polymorph of SiO2stable above 2.7GPa at metamorphic temperatures,is one of the most important index minerals for UHP metamomhism [1,2].展开更多
Oxamide is a potential slow-release nitrogen(N)fertilizer,especially under waterlogged conditions,due to its low solubility in water and the slow-release of ammonium by soil amidases.To investigate the effects of oxam...Oxamide is a potential slow-release nitrogen(N)fertilizer,especially under waterlogged conditions,due to its low solubility in water and the slow-release of ammonium by soil amidases.To investigate the effects of oxamide granules(2.00-2.38 mm in diameter)as a single basal fertilizer(180 or 144 kg N ha^(-1))on rice growth,soil properties,and N use efficiency in terms of N recovery efficiency(NRE),we conducted field experiments on two different types of paddy soils over two rice-growing seasons.Results showed that the fertilization effects of oxamide granules varied between the two types of paddy soils.In the red clayey paddy soil,the grain yields for both rice-growing seasons were high with a significantly higher NRE in the oxamide treatment than in the urea treatment.However,in the alluvial sandy paddy soil,the grain yields in the oxamide treatment were slightly lower than those in the urea treatment.Furthermore,oxamide produced little improvement in NRE in the alluvial sandy paddy soil.Soil incubation experiments over 98 d were also carried out to evaluate the factors affecting the N release behavior of oxamide granules in the two types of paddy soils.We found that the amidase activity was higher and,therefore,the oxamide hydrolysis rate was faster in the alluvial sandy paddy soil,which had a higher soil pH value and organic matter content,compared to the red clayey paddy soil.The faster N release and the longer growth period resulted in a mismatch between N supply by oxamide and rice demand,which,in turn,led to little improvement in NRE and a decreased grain yield in the alluvial sandy paddy soil,especially in the reduced oxamide treatment.These results could help select the appropriate size of oxamide granules for use as a slow-release N fertilizer depending on the soil properties and growth period of rice.展开更多
基金supported by the National Natural Science Foundation of China (41572040)the Major State Basic Research Development Program of China (2015CB856105)
文摘Ultrahigh-pressure (UHP)metamorphism plays important roles in continental dynamics.Understanding of this process has been enhanced by the discovery of coesite and micro-diamond from supracrustal rocks [1].Such UHP mineral inclusions provide unequivocal evidence that the least dense part of the lithosphere can be buried to 100-150km or more,and then returned to the surface.Coesite,an ultrahigh-pressure polymorph of SiO2stable above 2.7GPa at metamorphic temperatures,is one of the most important index minerals for UHP metamomhism [1,2].
基金the National Key Research and Development Program of China(No.2017YFD0800103)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA23020401)。
文摘Oxamide is a potential slow-release nitrogen(N)fertilizer,especially under waterlogged conditions,due to its low solubility in water and the slow-release of ammonium by soil amidases.To investigate the effects of oxamide granules(2.00-2.38 mm in diameter)as a single basal fertilizer(180 or 144 kg N ha^(-1))on rice growth,soil properties,and N use efficiency in terms of N recovery efficiency(NRE),we conducted field experiments on two different types of paddy soils over two rice-growing seasons.Results showed that the fertilization effects of oxamide granules varied between the two types of paddy soils.In the red clayey paddy soil,the grain yields for both rice-growing seasons were high with a significantly higher NRE in the oxamide treatment than in the urea treatment.However,in the alluvial sandy paddy soil,the grain yields in the oxamide treatment were slightly lower than those in the urea treatment.Furthermore,oxamide produced little improvement in NRE in the alluvial sandy paddy soil.Soil incubation experiments over 98 d were also carried out to evaluate the factors affecting the N release behavior of oxamide granules in the two types of paddy soils.We found that the amidase activity was higher and,therefore,the oxamide hydrolysis rate was faster in the alluvial sandy paddy soil,which had a higher soil pH value and organic matter content,compared to the red clayey paddy soil.The faster N release and the longer growth period resulted in a mismatch between N supply by oxamide and rice demand,which,in turn,led to little improvement in NRE and a decreased grain yield in the alluvial sandy paddy soil,especially in the reduced oxamide treatment.These results could help select the appropriate size of oxamide granules for use as a slow-release N fertilizer depending on the soil properties and growth period of rice.
