Effect of Traditional Cultivation Management on CO2 Flux in the Dry Tropical Cropland of South India

Abstract

Soils in tropical croplands are becoming degraded because of soil carbon (C) depletion. Local farmers in South India use a specific management of traditional cultivation, i.e., broadcast seeding. However, for sustainable C management, there is no quantitative data on the CO2 flux under this management. Our objectives were to (1) estimate the annual CO2 flux, and (2) evaluate the effect of traditional cultivation management (seeding rate) on the CO2 flux. Our field experiment was conducted in South India, from 2015 to 2017, including two cultivation periods with four cultivation management treatments (traditional cultivation management plot (T), fixed density plot (FD), no thinning plot (NT), and bare plot (B)). The seeding rate in the FD plot was ca. 50% of the T plot. We applied 1.1 Mg C ha−1 farmyard manure just before the experiment as a C input. We found that broadcasting, thinning, and cultivation increased soil moisture, while the CO2 efflux rate showed no significant difference between treatments throughout the experimental period. This indicates that cultivation management did not affect the CO2 flux. The total CO2 fluxes for two years were estimated at 2.2–2.7 Mg C ha−1. Our results indicate that it is necessary to apply larger or more frequent C inputs to prevent C depletion.

Impact of biochar and manure application on in-situ carbon dioxide flux, microbial activity, and carbon budget in degraded cropland soil of southern India

“…The average CO 2 efflux rate in the C treatment was 15.2 mg CO 2 -C m -2 h -1 , and this value was in line with our previous study conducted in the same field (20.5 mg CO 2 -C m -2 h -1 ; Seki et al, 2019). These values were relatively small when compared with those in the other studies in similar tropical ecosystems, such as 46.0 mg CO 2 -C m -2 h -1 in cropland of Tanzania with 13.8 g C kg-1 of soil (Sugihara et al, 2012), and 63.1 mg CO 2 -C m -2 h -1 in bare land of Brazil with 12.2 g C kg -1 of soil (La Scala et al, 2000).…”

“…A field experiment was conducted from September 2017 to December 2019 (27 months total) in a farmer's field in Madurai,Tamil Nadu state,India (9deg43'22.37" N 77deg46'51.61" E; 175 m asl) (Seki et al, 2019). The mean annual air temperature was 24.7 degC and the annual rainfall was 820 mm (692-857 mm; 2017-2019).…”

“…This area has 40-75% of annual rainfall during the rainy season (South-West monsoon: June-September, and North-East monsoon: October-December). Due to the low SOC content (Seki et al, 2019), the experimental field should be representative of the degraded cropland soils in this area (Lal, 2004b). Soil was classified into Typic Haplustepts (Soil Survey Staff, 2014).…”

“…The CO 2 efflux rate was measured by a closed-chamber system (Seki et al, 2019) at a frequency of approximately every 2 week in the rainy season and every month in the dry season for a total of 40 times throughout the experimental period. Polyvinyl chloride (PVC) columns (diameter 13 cm, height 30 cm) were inserted randomly in each plot at the end of each September or August, i.e., after FYM application.…”

“…Columns were re-installed within a plot every year, as mentioned above. Since soil respiration is composed of microbial respiration and plant-root respiration, plant-root respiration was excluded by the trenching method (Shinjo et al, 2006), following the detailed in Seki et al (2019). Gases were sampled at 0 min and again 40 min after the top of the column was covered with a plastic sheet, and analyzed with an infrared CO 2 analyzer (ZFP9-AA11; Fuji Electric, Japan) equipped with a voltage capture detector (C-R8A; Shimadzu, Japan) and N 2 carrier gas (Shinjo et al, 2006).…”