ISSN:
1573-5036
Keywords:
Grain legumes
;
Granite soil
;
Nitrogen
;
Pasture legumes
;
Soil N
;
Tropics
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Summary Soybean (Glycine max) and Siratro (Macroptillium atropurpureaum) were grown in a low N status granite soil for a total of six crop cycles under glasshouse conditions. Plant material was returned to the pots after each crop (total plant minus beans in soybean and 50% of top yield in siratro). Plant yields and N contents were recorded for each crop as well as changes in soil total N levels. From these data an estimate was made of N fixation by the crops. Mineral N levels were also monitored before and after the addition of crop residues. Under the conditions of this experiment, cumulative total N recovered in whole soybean was 6.76 g. From this total a cumulative amount of 5.09 g N/plot or 75.3% was removed from the soil-plant system in grain, leaving 1.67 g N/plot or 24.7% returned to the soil over the two year period. Over the same period, a cumulative amount of 5.18 g N/plot was recovered from siratro tops and of this, 2.59 g N/plot or 50% was returned to the soil to simulate a grazing situation. Under these glasshouse conditions, soybean added 6.80 g N/plot (843.2 kg/ha) and siratro 9.80 g N/plot (1215.2 kg/ha) over their original levels to the top 15 cm soil; no significant changes in the soil N were detected in soil below 15 cm depth. The mineral N levels increased over the six crop cycles from 5.8 to 32.3 ppm for soybean and from 18.7 to 166.0 ppm for siratro following the drying and wetting treatments imposed after the addition of crop residues. The large difference in the total and mineral N levels in soil under each legume crop species was due to difference in N fixation and the amount of plant N returned to the respective soils. Over the whole period of two years (six crops), the amount of N fixed was 11.91 g N/plot (1476.8 kg/ha) for soybean and 11.40 g N/plot (1413.6 kg/ha) for siratro, giving an average per crop of 1.99 and 1.90 g N/plot (246.1 and 235.6 kg/ha), respectively.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02197735
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