Crop growth and nitrogen transformations in wheat (Triticum aestivum L.) planted after wetland rice (Oryza sativa L.)     

Bacon  P. E.  Hoult  E. H.  McGarity  J. W.  Alter  D. 《Biology and Fertility of Soils》1989,7(3):263-268

Summary A field study was undertaken to examine the effects of various management strategies on wheat (Triticum aestivum L.) performance and N cycling in an intensively cropped soil. Microplots receiving 100 kg N ha^–1 as¹⁵NH₄ ^{+ 15}NO₃ ^– at sowing, tillering or stem elongation were compared with unfertilized microplots. Stubble from the previous rice crop was either incorporated, burnt without tillage, burnt then tilled or retained on the surface of untilled soil. Wheat grain yield ranged from 1.5 to 5.1 t ha^– and was closely related to N uptake. Plant accumulation of soil N averaged 36 kg N ha^–1 (LSD 5% = 10) on stubble-incorporation plots and 54 kg N ha^–1 on stubble-retention plots. Fertilizer N accumulation averaged 18 kg N ha^–1 (LSD 51% = 6) on stubble-incorporation plots and 50 kg N ha^–1 on stubble-retention plots. Tillage had little effect on burnt plots. Delaying N application from sowing until stem elongation increased average fertilizer N uptake from 26 to 39 kg N ha^–1 (LSD 5% = 6), but reduced soil N uptake from 50 to 37 kg N ha^– (LSD 5% = 10).Immobilization and leaching did not vary greatly between treatments and approximately one-third of the fertilizer was immobilized. Less than 1% of the fertilizer was found below a depth of 300 mm. Incorporating 9 t ha^–1 of rice stubble 13 days before wheat sowing reduced net apparent mineralization of native soil N from 37 to 3 kg ha^–1 between tillering and maturity. It also increased apparent denitrification of fertilizer N from an average 34 to 53 kg N ha^–1 (LSD 5% = 6). N loss occurred over several months, suggesting that denitrification was maintained by continued release of metabolizable carbohydrate from the decaying rice stubble. The results demonstrate that no-till systems increase crop yield and use of both fertilizer and soil N in intensive rice-based rotations.  相似文献   

THE EFFECT OF BURNING OF NATIVE PASTURE ON SOIL TEMPERATURE IN NORTHERN NEW SOUTH WALES     

B. E. Norton  J. W. McGarity   《Grass and Forage Science》1965,20(2):101-105

Thermocouples were used to measure temperatures at shallow depths (top 39 mm) in soils during late winter burning of hayed-off native pasture. Different intensities of burning were investigated. The maximum temperature recorded for any treatment was 75–5°C, at 1 mm below the soil surface, and marked temperature rises were recorded only in the upper 10 mm of the soil. The results suggest that the temperature rise induced by burning would have little direct effect on soil organic matter, the microbial populations, or buried seeds. The possible significance of these results in practice is discussed.  相似文献   

THE PLANT COMPONENT AS A FACTOR IN AMMONIA VOLATILIZATION FROM PASTURE SWARDS     

J. W. McGarity  E. H. Hoult 《Grass and Forage Science》1971,26(1):31-34

The volatilization of ammonia which followed the application of urea to a pasture sod was determined over a period of 14 days. Significant ammonia losses were measured after foliar application of urea to sods in which the soil component had been previously isolated from the plant components by sealing the sods with an impermeable membrane. Losses of ammonia by volatilization over the experimental period were less from plant surfaces than from unsealed sods in which the soil contributed to losses. It is concluded that in addition to soil ureolytic activity, the plant and litter components of pastures may provide major pathways of loss in the N economy of grasslands.  相似文献