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Chemical Characterization of Selected Benchmark Spots for C Sequestration in the Semi-Arid Tropics, India. Global Theme on Agroecosystems Report no. 32

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Title Chemical Characterization of Selected Benchmark Spots for C Sequestration in the Semi-Arid Tropics, India. Global Theme on Agroecosystems Report no. 32
 
Creator Ramesh, V
Wani, S P
Rego, T J
Sharma, K L
Bhattacharyya, T
Sahrawat, K L
Padmaja, K V
Gangadhar Rao, D
Venkateswarlu, B
Vanaja, M
Manna, M C
Srinivas, K
Maruthi, V
 
Subject Agriculture-Farming, Production, Technology, Economics
 
Description Soil organic carbon (SOC) plays an important role as a source of plant nutrients and in maintaining the soil integrity.
Any land use management that increases SOC by removing CO2 from the atmosphere by storing it in the soil, is
termed as carbon sequestration. This study was conducted to learn about the role of various agricultural practices on
soil nutrient dynamics and its relationship with SOC in various land use systems of semi-arid tropics (SAT). The
study area covered 28 SAT benchmark spots, 21 out of which were on black soils and 7 on red soils, covering areas of
15.29 m ha and 6.34 m ha, respectively. Soils were sampled from the benchmark sites/pedons during
2000–03 and processed for chemical analysis. It was observed that irrespective of bioclimatic zones, land use
under horticultural and agricultural systems in general, and paddy systems in particular, had maximum content of
organic carbon and total N. The soil parameter viz. clay fraction also influenced the total N and total P, and hence
organic carbon in black and red soils showed significant positive correlation with total N and P. Results indicated that
perennials could sequester carbon better when compared to annual crops. The nutrient stocks and soil organic C and
N ratio (carbon/nitrogen C:N), and carbon/phosphorus (C:P) were computed in addition to SOC for the purpose of
identifying the maintained soil quality. It was observed that the C:N ratio varied from 16:1 to 22:1 under different
zones and it was highest under semi-arid (moist) zones in black soils. Similarly C:P ratio of soils under various
bioclimatic zones revealed that it was highest under sub-humid (moist), followed by arid zone and lowest under semiarid
zones. The C:N ratio of studied soils under various systems was wider than commonly accepted values reported
for other tropical soils. The mean total N content of black soils was 0.042% and in case of red soils it was 0.052%,
which corresponds to a minimum threshold level of 0.063% and 0.078% for black and red soils, respectively. Thus
within the defined range of C:N ratios, those soils having SOC content of above values was considered along with
minimum threshold values of total nitrogen stocks (Mg ha-1) to arrive at the better systems. The minimum values of
TN stocks was calculated with the established equation and the values for the corresponding levels of SOC was found
to be 1.95 Mg ha-1 for black soils and 2.30 Mg ha-1 for red soils (both the soils types having an average bulk density of
1.5 Mg m-3). Thus the soil total N stocks of systems that were found above the minimum threshold values are
considered as better production systems.
The nutrient stocks and nutrient ratio in addition to soil organic carbon was used as the main criteria to develop
the soil C:N index. The index varied between 0.27 and 0.87 with an average of 0.57 under the various systems spread
over different bioclimatic zones and soil types. The variation of soil C:N index in different soil types showed that, the
fertility status of red soils in terms of SOC and soil nutrient stocks in majority of the pedons was higher as compared
to black soils. The variation in the soil C: N index due to bioclimatic zones in black and red soils, showed that semiarid
(moist) zone in black soils had the highest soil C: N index while the lowest was observed in sub-humid (moist)
zone. As the MAR decreased from 1200 mm to 850 mm, the index increased from 0.30 to 0.38. Thus among the
zones, the semi-arid moist was found to sequester more carbon. The variation in soil C:N index in different land use
based systems such as horticultural (0.50) and forest systems (0.40) had better C:N index as compared to agricultural
system in black soils. In red soils, forest system (0.76) had better C:N index as compared to agricultural system
dominated by annual crops. Another significant observation was that permanent fallow land also had the potential to
sequester carbon based on the magnitude of soil C:N index. The variation in the soil C:N index with the three major
crop based systems studied showed that cereal based cropping systems sequester more carbon as compared to cotton
and soybean based systems and can be promoted.
 
Publisher International Crops Research Institute for the Semi-Arid Tropics
 
Date 2006
 
Type Monograph
NonPeerReviewed
 
Format application/pdf
 
Language en
 
Rights —
 
Identifier http://oar.icrisat.org/2374/1/Chemical_characterization_of.pdf
Ramesh, V and Wani, S P and Rego, T J and Sharma, K L and Bhattacharyya, T and Sahrawat, K L and Padmaja, K V and Gangadhar Rao, D and Venkateswarlu, B and Vanaja, M and Manna, M C and Srinivas, K and Maruthi, V (2006) Chemical Characterization of Selected Benchmark Spots for C Sequestration in the Semi-Arid Tropics, India. Global Theme on Agroecosystems Report no. 32. Monograph. International Crops Research Institute for the Semi-Arid Tropics.