ISSN:
1573-5036
Keywords:
15N
;
microbial biomass
;
nitrogen uptake efficiency
;
Oryza sativa
;
soil nitrogen
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Recent field studies on irrigated rice at the IRRI research farm indicate efficient use of fertilizer-N based on plant uptake of applied N, (estimated by N difference), and utilization of acquired N for increased grain yield. These findings contrast with 15N uptake in microplot studies which underestimate the actual increase in plant N from added fertiliser. Constraints other than uptake efficiency, however, may govern fertiliser-N efficiency in farmers fields. In a study of 44 farmers' fields in Central Luzon, rice yields ranged from 2.5 to 6.2 t ha-1 and N uptake from 35 to 95 kg N ha-1 in plots without fertiliser-N addition. Farmers applied from 35 to 240 kg N ha-1, but there was no relationship between the N rate used by each farmer and the effective soil N supply. Mean N uptake efficiency from fertiliser by N difference was only 36%. We conclude that improved fertiliser-N efficiency by farmers will require a more information-intensive management strategy that makes N fertiliser inputs better fitted to the seasonal pattern of crop N demand and soil N supply.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00025057
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