ISSN:
1573-5036
Keywords:
anaerobic soil
;
flooded soils
;
intensive cropping
;
long term experiments
;
lowland rice
;
nitrogen mineralization
;
nitrogen uptake
;
on-farm research
;
organic carbon
;
organic matter
;
Oryza sativa
;
plant nitrogen
;
soil nitrogen
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Soil organic matter (SOM) has been proposed as an index of N supply in paddy soils although field validations are few. We evaluated the relationship between the indigenous N supply (N i ) of the soil-floodwater system and soil organic carbon (SOC) or total N (N t ) in surface soil of long-term fertility experiments (LTFEs) at 11 sites, in 42 farmer's fiels with similar soil type, and in the same field in ten consecutive rice (Oryza sativa L.) crops. The N i was estimated by crop N uptake from plots without applied N (N o plots) under otherwise favorable growth conditions. There was a tight linear correlation between yields and N uptake in N o plots and tremendous variation in both parameters among LTFE sites, farmer's fields, and in the same field over time. Correlation between N i and SOC or N t explained little of this variation. Factors likely to contribute to the poor correlation were: (1) inputs of N from sources other than N mineralization of SOM in surface soil, (2) degree of congruence between soil N supply and crop demand, which is sensitive to soil drying, length of fallow, crop rotation, and residue management, and (3) differences in SOM quality related to intensive cropping in submerged soil. Better understanding of the processes governing the N i of tropical lowland rice systems would contribute to the development of crop management practices that optimize utilization of indigenous N resources.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00029058
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