摘要:

In a laboratory study, ammonia (NH3) was trapped from 10 g soil units treated with 10 mg urea‐N, 10 mg urea‐N plus 50 ug N‐(n‐butyl) thiophosphoric triamide (NBPT), or 10 mg urea‐N plus 50 ug phenyl‐phosphorodiamidate (PPD). The soil was a Dothan loamy sand with pH levels adjusted to 6.0, 6.5, and 6.9 prior to N application. After 12 days, NBPT reduced NH3volatilization 95 to 97%, while PPD reduced it 19 to 30%. Although NH3loss was positively related to initial soil pH, there was no interaction between pH and urease inhibitor. In a field study, NH3was trapped in semi‐closed chambers from 134 kg N/ha surface applied to corn (Zea maysL.) 6 weeks after planting. Nine days after N application, NH3losses were 20.5, 1.5, 1.5, and 0.2 kg N/ha from urea, urea plus 0.25% NBPT, urea plus 0.50% NBPT, and ammonium nitrate, respectively. Covariance analysis showed that percent organic matter was negatively related to NHL losses. The soil properties, initial pH, CEC, and percent sand, did not vary enough to affect NH3volatilization. In conclusion, in both the laboratory and the field, NBPT exhibited strong control of NH3volatilization, and could thereby prevent significant loss of surface‐applied urea‐N to crops.

ISSN:0010-3624    

DOI:10.1080/00103628909368160

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

摘要:

Differences were studied in humic (HA) and fulvic acid (FA) extracted from soils and streams in South Georgia by the Amberlite XAD‐8 resin and conventional NaOH method. Characterization analysis was performed by liquid13C NMR, infrared (IR) spectroscopy, scanning electron microscopy (SEM), and chemical analysis. The NMR spectra indicated that the resin method yielded black water HA and FA with spectroscopic, chemical and elemental characteristics different from those isolated by the conventional NaOH method. Humic acids from both the resin and conventional NaOH methods were composed of aliphatic, aromatics and carboxyl groups, but the “resin”; HA contained more aliphatic groups. These differences were also noticed between the FA fractions obtained by the two methods. The differences corresponded to differences in IR spectra. The IR spectrum of “resin”; FA exhibited only a weak shoulder at 1625/cm for the COO”; stretching vibration, in contrast to that of FA isolated by the conventional NaOH procedure. Apparently, the high aliphatic‐CH3group content has blocked the vibration above, as evidenced by methylation of HA. Fulvic acid extracted by the resin method was also higher in total acidity, but considerably lower in N content than FA obtained by the conventional NaOH method. Both methods yielded black water FA which was less aromatic in nature than black water HA, or soil FA.

ISSN:0010-3624    

DOI:10.1080/00103628909368161

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628909368149

出版商:Taylor & Francis Group    

年代:1989

数据来源: Taylor