油菜因产定氮及猪厩肥中氮素利用折算率研究

在浙江中部发育于第四纪红土母质上的红壤性水稻土上设置田间试验 .提出当地油菜定氮公式 :N需 =0 0 7( y -1 1x) /E肥 .式中 ,y—足肥丰产下产量 ;x—无氮情况下产量 ;y和x之间可用y =67 2 2 58+1 2 1 98x表达 ;0 0 7是生产 1kg油菜籽 (含秸秆 )的需N量 (kg) ;E肥 为化肥利用率 ,它与x之间可用E肥 =4 9 2 3 6-0 2 3 53x表达 .此外明确在化肥和猪厩肥一起施用中 ,猪厩肥中N素利用折算率约为化肥N的一半左右 .     

Dissolved organic carbon (DOC) as a parameter of compost maturity

Despite numerous investigations of the maturation process of composts, a simple and straightforward parameter which can predict plant response upon compost application has yet to be defined. In light of results accumulated over a decade, we examined simple, chemical parameters of three composts from three types of source materials (municipal solid waste (MSW), separated cow manure (CSM), biosolids (BS)). These materials were composted using different procedures and facilities. The chemical parameters were correlated to the growth response of cucumbers or ryegrass sown in potting media amended with the composts sampled at different stages of the process. The dissolved organic carbon (DOC) concentration of all composts decreased rapidly within the first month, then, towards the end of the process, stabilized at concentration below 4 g kg⁻¹. DOC correlated highly and significantly to the absorbance at 465 nm in all composts, and also to the C/N ratio. Nitrate evolution was similar in all composts, but the final concentrations differed among them. Plant biomass increased with composting time. For CSM and BS compost maximum biomass was reached when the DOC reached levels below 4 g kg⁻¹. DOC concentration is suggested for use as a simple method of determining maturity, with 4 g kg⁻¹ recommended as a threshold level indicating maturity. Absorbance at 465 nm can be used instead of DOC concentration after appropriate calibration.     

Comparison of chemical and microbiological methods for the characterization of the maturity of composts from contrasting sources

Six composts from different sources (wheat and barley straw; coniferous bark; mixed hop rape and bark; two from household garbage; mixed paper dust and sewage sludge) were characterized by chemical methods, including various forms of N and organic matter fractionation, and by microbiological methods. The dehydrogenase activity, respiration rate, and arginine ammonification were investigated, which represent different aspects of C and N metabolism. Only a few significant correlations were found between different maturity indexes. Dehydrogenase activity was in agreement with the widely accepted humic acid C to fulvic acid C ratio and might therefore be acceptable as a maturity index. Arginine ammonification provided valuable information on the N status in composts; negative values indicated that considerable amounts of easily degradable organic compounds with wide C:N ratios were still present, which would lead to microbial immobilization of soil N after the application of these composts. A combination of dehydrogenase activity and arginine ammonification data led to an unambiguous classification of all composts, and is therefore recommended for further consideration; in contrast, chemical data were contradictory and markedly dependent on the original substrates. The respiration rate, which was closely correlated with the percentage of organic C, did not contribute to the assessment of compost maturity.