Soil respiration under different N fertilization and irrigation regimes in Bengaluru, S-India

Nutr Cycl Agroecosyst https://doi.org/10.1007/s10705-023-10311-y ORIGINAL ARTICLE Soil respiration under different N fertilization and irrigation regimes in Bengaluru, S‑India Suman Kumar Sourav · C. T. Subbarayappa · D C. Hanumanthappa · Mudalagiriyappa · Prem Jose Vazhacharickal · Andrea Mock · Mariko Ingold · Andreas Buerkert Received: 15 April 2023 / Accepted: 19 August 2023 © The Author(s) 2023 Abstract Rapid urbanization in many countries of the Global South has led to intensification of urban and peri-urban agriculture (UPA) whose effects on the soils’ physical, chemical, and microbial properties have been hardly studied. We therefore investigated the effects of different intensity levels, exemplified by three rates of mineral nitrogen (N) addition and irrigation on CO2 emissions in typical crops during the wet (Kharif) and dry (Rabi) season on a Nitisol in Bengaluru, S-India. Respiration data were collected from 2017 to 2021 in two two-factorial split-plot experiments conducted under rainfed and irrigated conditions. Test crops were maize (Zea mays L.), finger millet (Eleusine S. K. Sourav · A. Mock · M. Ingold · A. Buerkert (*) Organic Plant Production and Agroecosystems Research in the Tropics and Subtropics (OPATS), University of Kassel, Kassel, Germany e-mail: C. T. Subbarayappa Soil Science and Agricultural Chemistry, University of Agricultural Sciences, GKVK, Bengaluru, India D. C. Hanumanthappa AICRP On Agroforestry, University of Agricultural Sciences, GKVK, Bengaluru, India Mudalagiriyappa AICRP for Dryland Agriculture, University of Agricultural Sciences, GKVK, Bengaluru, India P. J. Vazhacharickal Rural‑Urban Center, University of Agricultural Sciences, GKVK, Bengaluru, India coracana Gaertn.), and lablab (Lablab purpureus L. Sweet) under rainfed and irrigated conditions, as well as the vegetables cabbage (Brassica oleracea var. capitata), eggplant (Solanum melongena L.), and tomato (Solanum lycopersicum L.) or chili (Capsicum annuum L.). Carbon dioxide (CO2) emissions were determined using a Los Gatos Research (LGR) multi-gas analyzer whereby under our study conditions C H4, NH3 and N2O were negligible. Measurements were conducted from 7:00 am to 11:30 am and repeated from 12:30 pm to 6:00 pm. Irrespective of irrigation, season, crops and N fertilizer level, C O2 emission rates during afternoon hours were significantly higher (2–128%) than during morning hours. In the irrigated field diurnal emission differences between afternoon and morning hours ranged from 0.04 to 1.61 kg C O2-C ha−1 h−1 while in the rainfed field they averaged 0.20–1.78 kg C O2-C ha−1 h−1. Irrespective of crops, in the rainfed field CO2 emissions in high N plots were 56.4% larger than in low N plots whereas in the irrigated field they were only 12.1% larger. The results of a linear mixed model analysis indicated that N fertilization enhanced CO2 emissions whereby these effects were highest in rainfed crops. Soil moisture enhanced emissions in rainfed crops but decreased them under irrigation where cropspecific CO2 emissions within a season were independent of N application. Soil temperature at 5 cm depth enhanced CO2 emissions in both fields. Overall, higher N and soil temperature enhanced CO2 fluxes whereas effects of soil moisture depended on irrigation. Vol.: (0123456789) 13 Nutr Cycl Agroecosyst Keywords CO2 emission · Intensification · Linear mixed model · Seasonal soil respiration Introduction Worldwide agroecosystems around rapidly growing cities are greatly affected by rural–urban transformation as farmers continuously adapt their crop choices and management intensities in response to the growing competition for land, labour, and water as well as the opportunities of large and close-by urban markets (Swain and Teufel 2017). This leads to intensified crop cultivation which may affect the soils’ physical, chemical, and biological properties whose response to the regime-shifts imposed remains poorly studied (Elmqvist et al. 2013; Steinhübel and von Cramon-Taubadel 2020). This is particularly the case for poorly buffered tropical soils of the Global South. Jain et al. (2019) reported that farmers in many peri-urban areas of India have changed their cropping patterns focusing on high-priced horticultural or local specialty crops such as grape (Vitis vinifera L.) and finger millet (Eleusine coracana Gaertn.). Such crops yield higher revenue per unit of water consumed and are often cultivated year round under drip irrigation. Short duration crops are intensely rotated whereby a major knowledge gap exists on the effects of irrigation and fertilization on C O2 emissions (Buerkert et al. 2021). Agriculture is a significant contributor to greenhouse gas (GHG) emissions (Heimsch et al. 2021; Lynch et al. 2021). Thereby the majority of studies agree that C O2 contributes the largest proportion of GHG emissions from soils and its flux rates are more than hundred times larger than those of N2O, CH4, and other gases which is, however, partly compensated for by higher GHG effects of the latter (Ruser et al. 2006; Chen et al. 2010; Abalos et al. 2014; Negassa et al. 2015). CO2 emissions from soils heavily depend on its water content and N status (Darwish et al. 2006; Abalos et al. 2014) and it is also known that crop rotation in combination with irrigation and fertilizer application lead to changes in soil C and N dynamics by altering plant primary production, nutrient uptake, and recycled plant residues (Snyder et al. 2009; Weiler et al. 2018; Oldfield et al. 2019; Araya et al. 2021). From a subtropical Pinus plantation in southeastern China Iqbal et al. (2008) reported that CO2 emissions depended on soil temperature and water-filled pore space (WFPS). Tang et al. (2005) and Gaumont-Guay et al. (2006) determined that 70% of the diurnal variation Vol:. (1234567890) 13 of soil C O2 fluxes was determined by soil temperature, which was similar to results of Manka’abusi et al. (2020) for CO2, N2O, and N H3 in Quagadougou (Burkina Faso) and Tamale (northern Ghana). In the same study, cropping cycles and seasons also affected C O2 emissions whereby CO2 emissions under amaranth (Amaranthus L.) were significantly higher (20–83%) than those of other crops in the cycle (lettuce—Lactuca sativa L., jute mallow—Corchorus olitorius L. and carrot—Daucus carota subsp. sativus) across all treatments. It was also observed that mean CO2 emissions for lettuce and carrot were significantly lower (11–66%) during the cold and dry season compared with the rainy period. In Bengaluru rural–urban transition has led to altered cropping patterns (Patil et al. 2019), depletion of ground water sources (Kulkarni et al. 2021), intensification of N fertilizer application (Prasad et al. 2019), and a shift from rainfed agriculture to irrigated systems (Prasad et al. 2016). Under the monsoonal climate conditions of S-India with frequent drought spells irrigation plays an important role in enhancing cro (...truncated)