Dynamics of soil total C and N, microbial biomass and water soluble C in tropical agroecosystems
In order to understand the effects of long-term organic residue additions on the active pool of soil organic matter, microbial biomass C and N, water soluble C and total C and N were studied in four 9-year old cropping systems planted to a year-long corn (Zea mays L., cv. Tuxpeno C-7) -bean (Phaseolus vulgaris L., cv. Turrialba) rotation in the humid tropics of Costa Rica: two alley cropping systems including leguminous trees (Erythrina poeppigiana (Walpers) O.F. Cook and Gliricidia sepium (Jacq.) Steud.), and two cropping systems without trees and either fertilized or not with N. Higher total and microbial C and N, water soluble C, and soil moisture were found in the alley cropping treatments than in the treatments without trees. Total C and N values were high (40-45 g kg-1 and 2.4-2.8 g kg-1, respectively), but microbial biomass C and N values (without conversion factors) were relatively low (50-62 mg kg-1 and 7-11 mg kg-1, respectively), probably due to the volcanic nature of the soils. Water soluble C values were high, ranging from 200 to 284 mg kg-1. Seasonal changes of microbial biomass appeared to depend more on crop phenology, management practices (pesticides and fertilizer applications) and soil misture than on pruning additions. During the year microbial C:N ratios varied from 4.5-5.5 in the wet period (corn crop) to 13.5-16.5 in the dry period (bean crop). Apparently, interaction among crop stovers and tree prunings results in a system which oscillates between N immobilization and mineralization.
| Main Authors: | , , , |
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| Format: | biblioteca |
| Published: |
Turrialba (Costa Rica)
[199
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| Subjects: | SUELOS, FERTILIDAD DEL SUELO, CULTIVO EN FAJAS, ARBOLES Y CULTIVOS ANUALES, RESIDUOS ORGANICOS, BIOMASA, ZEA MAYS, PHASEOLUS, ERYTHRINA POEPPIGIANA, GLIRICIDIA SEPIUM, |
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| Summary: | In order to understand the effects of long-term organic residue additions on the active pool of soil organic matter, microbial biomass C and N, water soluble C and total C and N were studied in four 9-year old cropping systems planted to a year-long corn (Zea mays L., cv. Tuxpeno C-7) -bean (Phaseolus vulgaris L., cv. Turrialba) rotation in the humid tropics of Costa Rica: two alley cropping systems including leguminous trees (Erythrina poeppigiana (Walpers) O.F. Cook and Gliricidia sepium (Jacq.) Steud.), and two cropping systems without trees and either fertilized or not with N. Higher total and microbial C and N, water soluble C, and soil moisture were found in the alley cropping treatments than in the treatments without trees. Total C and N values were high (40-45 g kg-1 and 2.4-2.8 g kg-1, respectively), but microbial biomass C and N values (without conversion factors) were relatively low (50-62 mg kg-1 and 7-11 mg kg-1, respectively), probably due to the volcanic nature of the soils. Water soluble C values were high, ranging from 200 to 284 mg kg-1. Seasonal changes of microbial biomass appeared to depend more on crop phenology, management practices (pesticides and fertilizer applications) and soil misture than on pruning additions. During the year microbial C:N ratios varied from 4.5-5.5 in the wet period (corn crop) to 13.5-16.5 in the dry period (bean crop). Apparently, interaction among crop stovers and tree prunings results in a system which oscillates between N immobilization and mineralization. |
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