ISSN:
1573-5036
Keywords:
cowpea
;
green manure
;
growth stage
;
N mineralization
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract Cowpea [Vigna unguiculata (L). Walp.] has great potential as green manure due to its rapid N accumulation and efficient N2 fixation. The objective of this study was to measure the rate of N mineralization from cowpea plant parts harvested at onset of flowering (5 weeks) and mid pod-fill (7 weeks) under near optimum conditions. Cowpeas were grown in a greenhouse and supplied with 15NH4 15NO3 to isotopically label tissue. Cowpea leaves, stems, and roots were incorporated into a sandy soil (Psammentic Paleustalf) and net N mineralized was measured several times during a 10 week incubation. The amount of N accumulated in 7-week old cowpeas was more than double that in 5-week old cowpeas. The portion of N mineralized after 10 weeks was 24% for 5-week old cowpeas and 27% for 7-week old cowpeas. The rate of N mineralization from leaves and stems increased with plant age, but decreased for roots. The amount of N mineralized from 7-week old cowpeas was more than double (235%) that from 5-week old cowpeas due to greater N accumulation and a more rapid rate of N mineralization of the more mature cowpeas. The greatest amount of N was released from leaves, which amounted to 74 and 65% of total N mineralization from 5- and 7-week old cowpeas, respectively. The percentage of N mineralized by 10 weeks was linearly related to the tissue N concentration of the plant parts and to their C/N ratio. These relationships allow a quick estimation of the amount of N that would mineralize from cowpea residues incorporated into soil based on their N concentration or C/N ratio.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00010151
