The growth and nitrogen uptake of Rhodes grass grown on soils with varying histories of legume cropping |
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Authors: | Othman Yaacob Graeme J. Blair |
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Affiliation: | (1) Department of Agronomy and Soil Science, University of New England, 2351 Armidale, NSW, Australia;(2) Present address: Soil Science Department, Universiti Pertanian Malaysia, Serdang, Selangor, Malaysia |
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Abstract: | Summary Rhodes grass (Chloris gayana) was grown under glasshouse conditions on soils that had previously grown from 1 to 6 soybean (Glycine max) or Siratro (Macroptillium atropurpureum) crops. Soil mineral N contents at sowing were higher in Siratro-cropped than soybean-cropped soils and increased with cropping history.Yields of Rhodes grass at the first harvest (14 weeks) were related to soil mineral N levels at sowing by the relationship Y=138.7 (1–0.917e–0.012x). Grass grown on all soybean soils was responsive to N at both harvests (14 and 28 weeks). Grass grown on soil that had grown three or more Siratro crops was non-responsive to N at the first harvest but responses to N were recorded on all Siratro soils at the second harvest.The amount of N removed by the grass crops was small in relation to the total amount present in the soil system. This resulted in no change in soil total N levels over the two crop periods.These results highlight the need to study N dynamics in crop systems rather than continue to measure N pool sizes when evaluating the contribution of biologically fixed N to the nutrition of subsequent non-legume crops. |
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Keywords: | Legumes Nitrogen Rhodes grass |
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