摘要:

Under continuous no‐till management, acid‐forming fertilizers tend to reduce surface soil pH. Low pH is known to deactivate the triazine herbicides. It is questionable whether soil samples from the traditional 0–20 cm depth accurately reflect pH at the surface (0–2.5 cm). Soil samples were taken from an established no‐till corn test which had received up to 270 kg N/ha annually. Soil pH was determined from variable depths. Where ammonium nitrate was applied at 135 or 270 kg N/ha, soil pH increased with sampling depth. Soil samples taken at either the 0–5 cm or 0–7.5 cm depth accurately reflected the surface pH within ± 0.2 pH units. Variation in samples taken from deeper depths exceeded these limits. Soil samples at variable depths were also obtained from continuous no‐till corn tests which had received up to 78 kg P/ha and 149 kg K/ha annually. Soil samples taken from 0–5 cm accurately reflected surface pH, but contained higher available P and K than samples taken from 0–20 cm. Present soil test P and K ranges for soil samples from the 0–20 cm depth should be adjusted to account for increased P and K observed at 0–5 cm under continuous no‐tillage.

ISSN:0010-3624    

DOI:10.1080/00103628409367449

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Twenty soils were extracted in duplicate with 1 M KC1 and analysed for Al by AAS, ICPES, double titration and an eriochrome cyanine R colorimetric method. Exchange acidity was also measured and compared with Al values. Differences between the four Al methods were small. The only statistically significant difference was that Al by ICPES exceeded Al by AAS and titration. Results by the colorimetric method did not differ from those by the other three. Exchange acidity values were higher than Al by titration, with differences ranging from 0.07 to 1.01 m. equiv. 100 g‐1.

ISSN:0010-3624    

DOI:10.1080/00103628409367450

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Recent simulation models of soil organic matter and N transformations postulate several pools of soil N with differing stabilities. A nonlinear regression procedure was used with published data (Stanford and Smith for 34 soil samples to estimate the size of a pool (N1) which mineralized within four weeks, and the pool size (N1) and first order mineralization rate constant (k2) of a pool which mineralizes more slowly and which is similar to the “active”; N fraction described by Parton et al. Regression equations including all 34 samples based on total soil nitrogen, organic carbon, pH, and dummy variables for soil order, temperature and moisture regimes, texture, and presence of free calcium carbonate accounted for 55%, 86%, and 53% of the variation in N1, N2, and k2, respectively.

ISSN:0010-3624    

DOI:10.1080/00103628409367451

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In order to increase the utilization of annual clovers in pastures, information is needed on seasonalRhizobium trifolii‐crimson clover (Trifolium incarnatumL.) interactions relating to factors affecting dinitrogen fixation rates. Five double‐antibiotic labelled strains ofR. trifoliiwere evaluated for symbiotic effectiveness when in competition with indigenous rhizobia in nodulating ‘Tibbee’ crimson clover. Experiments were conducted in two soil environments, an ultisol and a vertisol, over two consecutive growing seasons. Successful nodulation of crimson clover by the introduced strains varied significantly within and between locations over both growing seasons. Strain 162K10, though highly competitive at the ultisol location, was dominated by the indigenous rhizobia over both seasons at the vertisol site. Strain RP113–14 occupied more than 90% of the nodules during the first growing season although this declined to only 60% in the subsequent season at the ultisol site. On the vertisol site, the results with RP113–14 were reversed. Strain RP111–51 was the only strain to predominantly nodulate crimson clover over both seasons at both locations. Indigenous populations ofR. trifoliiat the vertisol site dominated strains 162K10, RP113–14, LM207, and TA1 throughout the establishment year, although 162K10 and RP113–14 survived for the following year and increased their nodule occupancies to 71 and 86%, respectively. A local isolate selection, LM207, and an ineffective mutant of strain TA1 were both over‐whelmed by the indigenous populations. Higher forage production and more robust clover stands were associated with the most competitive amended strains. It was apparent that crimson clover production can be enhanced by the introduction of more effectiveR. trifoliistrains.

ISSN:0010-3624    

DOI:10.1080/00103628409367452

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A greenhouse experiment was conducted to compare the P requirements for early growth of red clover (Trifolium pratenseL.), birdsfoot trefoil (Lotus corniculatusL.) and flatpea (Lathyrus sylvestrisL.). Phosphorus sorption isotherms were used to predict P fertilizer additions required to adjust two Appalachian soils to eight equilibrium solution P levels (0.005 to 0.50 ug P/m1).

ISSN:0010-3624    

DOI:10.1080/00103628409367453

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The contents of various forms of manganese in 10 profiles from S. W. Nigeria was determined by selective extraction methods: dithionite (total), oxalate (amorphous), hydroquinone (easily reducible) and pyrophosphate (origanic).

ISSN:0010-3624    

DOI:10.1080/00103628409367454

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

A nondigestion method described earlier for K determination in plant tissue was tested for measuring K in grain samples of chickpea, pigeonpea, sorghum and pearl millet crops. The method involves shaking 0.5 g of finely ground (< 0.4 mm) seed sample with 40 ml of 0.5 N HC1 for 5 minutes at room temperature ( ? 25°C). The values of K obtained by this method with grain samples of the four crops were in close agreement (r ? 0.997) with those obtained using the conventional triacid digestion technique. These results suggest that this method may also be used for routine rapid and precise K analysis is seed materials of different crops.

ISSN:0010-3624    

DOI:10.1080/00103628409367455

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0010-3624    

DOI:10.1080/00103628409367448

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor