Soil N2O emission from organic and conventional cotton farming in Northern Tanzania

Thomas N Bwana; Nyambilila A Amuri; Ernest Semu; Lars Elsgaard; Klaus Butterbach-Bahl; David E Pelster; Jørgen Eivind Olesen

doi:10.1016/j.scitotenv.2021.147301

Soil N₂O emission from organic and conventional cotton farming in Northern Tanzania

Sci Total Environ. 2021 Sep 1:785:147301. doi: 10.1016/j.scitotenv.2021.147301. Epub 2021 Apr 24.

Authors

Thomas N Bwana¹, Nyambilila A Amuri², Ernest Semu³, Lars Elsgaard⁴, Klaus Butterbach-Bahl⁵, David E Pelster⁶, Jørgen Eivind Olesen⁴

Affiliations

¹ Department of Soil and Geological Science, Sokoine University of Agriculture (SUA), P. O. Box 3008, Morogoro, Tanzania; Department of Environment, Vice President's Office, Dodoma, Tanzania.
² Department of Soil and Geological Science, Sokoine University of Agriculture (SUA), P. O. Box 3008, Morogoro, Tanzania. Electronic address: namuri@sua.ac.tz.
³ Department of Soil and Geological Science, Sokoine University of Agriculture (SUA), P. O. Box 3008, Morogoro, Tanzania.
⁴ Department of Agroecology, Aarhus University, Blichers Alle 20, 8830 Tjele, Denmark.
⁵ Karlsruhe Institute of Technology, Institute for Meteorology and Climate Research, Atmospheric Environmental Research (IMK-IFU), Kreuzeckbahnstrasse 19, Garmisch-Partenkirchen 82467, Germany; Mazingira Centre, International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi 00100, Kenya.
⁶ Agriculture and Agri-Food Canada, 2560 Hochelaga Boulevard, Quebec G1V 2J, Canada.

PMID: 33933767
DOI: 10.1016/j.scitotenv.2021.147301

Abstract

The effort to increase the sustainable supply of food and fibre is challenged by the potential for increased greenhouse gas (GHG) emissions from farming systems with intensified production systems. This study aimed at quantifying soil N₂O emissions from smallholder organic and conventional cotton production practices in a semi-arid area, Meatu, Northern Tanzania. Field experiments were conducted to quantify N₂O emissions under (i) current practices with organic (3 Mg ha^-1 farmyard manure (FYM)) and conventional (30 kg mineral N ha^-1) cultivation; (ii) a high input practice with organic (5 Mg ha^-1 FYM) and conventional (60 kg mineral N ha^-1) cultivation; and (iii) an integrated practice with organic (3 Mg FYM + legume intercropping) and conventional (30 kg N + 3 Mg ha^-1 FYM) cultivation. In both organic and conventional farming, control treatments with no fertilizer application were included. The study was performed over two growing seasons, where season 1 was rather wet and season 2 was rather dry. Static chambers were used for in-situ measurement of N₂O emission from soil. The current organic and conventional cotton farming practices did not differ (P > 0.05) in cumulative area-scaled and yield-scaled N₂O emissions. High input conventional cotton showed higher area scaled N₂O emissions than organic cotton during the wetter season, but not during the drier season. The inorganic fertilizer + FYM combination did not differ (P > 0.05) in area- and yield-scaled N₂O emissions from conventional practice. Intercropping cotton and legumes did not affect (P > 0.05) N₂O emission compared to 3 Mg FYM ha^-1. The emission factors for both conventional and organic systems were generally above 1% in the dry season 2, but below 1% in the wetter season 1. The use of organic and inorganic fertilizers at rates up to 60 kg N ha^-1, FYM-inorganic fertilizer combination, and cotton-legume intercropping increased yields, while N₂O emissions stayed low, in particular with use of mineral fertilizers.

Keywords: Cotton; Fertilizer; Greenhouse gas; Intercropping; Manure; Nitrous oxide.