摘要:

Abstract.This paper reports the growth and yield of grain and the utilization of fertilizer nitrogen applied on either one or two occasions in spring to a crop of winter barley established by direct drilling on a chalk soil in southern England. Nitrogen, as ammonium nitrate, was applied at rates of 0 to 140 kg N ha−1in a range of proportions on two occasions (March and April 1981); nitrogen‐15 was used to facilitate study of the nitrogen utilization by the crop.When sampled before the second top‐dressing in April, the greatest number of tillers were found on plants treated with 70 and 100 kg N ha−1in March. The total above ground dry matter production at harvest was greatest when the split nitrogen dressing totalled more than 100 kg N ha−1, although the apparent efficiency of nitrogen usage (kg DM per kg N applied) was greatest when 60 kg N ha−1was divided equally between the two application dates. Grain yield was heaviest (6.471 ha−1) at the largest rate of nitrogen applied (140 kg N ha−1); the lightest yield from the nitrogen treated crops was recorded from 100 kg N ha−1applied as a single dressing in April that stimulated shoot production and decreased individual grain weight. The recovery in grain and straw of labelled fertilizer nitrogen applied only in March averaged 42.2% and was 49.8% when the nitrogen was applied only in April. The recovery of nitrogen applied in both March and April at the total rate of 100 kg N ha−1but split 30/70 or 70/30 was 44.5% and 42.5% respectively. Non‐fertilizer sources of nitrogen contributed 60.7–71.7% of the total nitrogen uptake

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00661.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Urea and ammonium were compared with and without nitrification inhibitors (nitrapyrin and dicyandiamide) as a possible means of reducing the nitrate concentration in winter lettuce grown in the glasshouse. Neither inhibitor had a significant effect on nitrate concentrations at the lower rate of applied nitrogen (138 kg ha−1N). At the higher rate of urea (414 kg ha−1N) dicyandiamide significantly reduced the nitrate concentration but this was accompanied by an unacceptable loss in yield and quality thought to be due to phytotoxic effects of the high level of residual ammonium. Nitrapyrin had no effect on the nitrate concentrations in lett

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00662.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00663.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.The factors influencing inorganic nitrogen inputs in wet deposition in two upland catchments in northeast Scotland are discussed. Seasonal trends in nitrate‐nitrogen concentrations in water draining from the catchments, and in monthly nitrate‐nitrogen outputs, are reported and explained. The inputs in rain exceeded the output in the rivers in the two catchments by 3.9–9.4 kg ha−1a−1. Retention by vegetation probably plays a crucial role in nitrogen cycling in th

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00664.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.The effects of ditch spacing (10, 20 and 40 m) and depth (60 and 90 cm) on watertable depth were measured in a Sitka spruce plantation before and after drainage and finally after part of the plantation had been clearfelled. No significant differences in watertable depth were recorded between drainage treatments mainly because the ditch spacings were too large but also because of inadequate calibration of the site before the drainage treatments were applied. By the time of felling, the site had been thoroughly calibrated for the behaviour of the watertable, enabling sensitive comparisons to be made, and a significant rise in the watertable was recorded after felling.

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00665.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Abstract.Lime was applied in summer 1981 at rates up to 201 ha−1prior to reseeding an unimproved peaty hill soil. A marked pH gradient with depth developed showing that 3 years after application lime had very little effect below a depth of 5 cm. Soil pH values for 0–7.5 cm samples were: nil lime‐4.2; 1 t ha−1‐pH 4.3; 2 tha−1‐pH 4.6; 4 t ha−1‐pH 5.0; 6 t ha−1‐pH 5.6. In the 0–2.5 cm layer pH values were much higher.In all years at least 80% of maximum yield was achieved from an initial application of 21 ha−1lime. Botanical analysis showed that maximum persistence of sown species, perennial ryegrass and timothy, occurred from 2 t ha−1lime; 6 t ha−1lime was necessary for maximum persistence of clover. Lime application had only small effects on the miner

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00666.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

IT IS now almost two years since the Royal Society published its authoritative study group report,The Nitrogen Cycle of the UK, the first comprehensive account of the nitrate issue. For the first time a complete picture was revealed of the nitrogen cycle in the UK and the Study Group was able to make a wide‐ranging series of recommendations for future researc

ISSN:0266-0032    

DOI:10.1111/j.1475-2743.1985.tb00667.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY