title: Adaptive nitrogen and integrated weed management in conservation agriculture: impacts on agronomic productivity, greenhouse gas emissions, and herbicide residues.
abstract: Increasing nitrogen (N) immobilization and weed interference in the early phase of implementation of conservation agriculture (CA) affects crop yields. Yet, higher fertilizer and herbicide use to improve productivity influences greenhouse gase emissions and herbicide residues. These tradeoffs precipitated a need for adaptive N and integrated weed management in CA-based maize (Zea mays L.)-wheat [Triticum aestivum (L.) emend Fiori & Paol] cropping system in the Indo-Gangetic Plains (IGP) to optimize N availability and reduce weed proliferation. Adaptive N fertilization was based on soil test value and normalized difference vegetation index measurement (NDVM) by GreenSeeker™ technology, while integrated weed management included brown manuring (Sesbania aculeata L. co-culture, killed at 25 days after sowing), herbicide mixture, and weedy check (control, i.e., without weed management). Results indicated that the 'best-adaptive N rate' (i.e., 50% basal + 25% broadcast at 25 days after sowing + supplementary N guided by NDVM) increased maize and wheat grain yields by 20 and 14% (averaged for 2 years), respectively, compared with whole recommended N applied at sowing. Weed management by brown manuring (during maize) and herbicide mixture (during wheat) resulted in 10 and 21% higher grain yields (averaged for 2 years), respectively, over the weedy check. The NDVM in-season N fertilization and brown manuring affected N2O and CO2emissions, but resulted in improved carbon storage efficiency, while herbicide residuals in soil were significantly lower in the maize season than in wheat cropping. This study concludes that adaptive N and integrated weed management enhance synergy between agronomic productivity, fertilizer and herbicide efficiency, and greenhouse gas mitigation.
authors.affiliation: ICAR, Indian Agricultural Research Institute, New Delhi, 110012, India. anthony.oyeogbe@gmail.com.|Savannah Sugar Company Limited, Dangote Sugar Refinery, Yola, PMB 2230, Nigeria. anthony.oyeogbe@gmail.com.
authors.forename: Anthony Imoudu
authors.initials: AI
authors.lastname: Oyeogbe
authors.affiliation: ICAR, Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: T K
authors.initials: TK
authors.lastname: Das
authors.affiliation: ICAR, Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: Arti
authors.initials: A
authors.lastname: Bhatia
authors.affiliation: ICAR, Indian Agricultural Research Institute, New Delhi, 110012, India.
authors.forename: Shashi Bala
authors.initials: SB
authors.lastname: Singh
mesh_terms: D000383:Agriculture / Q000379:methods*; D002244:Carbon / Q000737:chemistry; D002523:Edible Grain / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods*; D005308:Fertilizers / Q000032:analysis; D006540:Herbicides / Q000032:analysis; D008372:Manure / Q000032:analysis; D009584:Nitrogen / Q000032:analysis*; D057685:Plant Weeds; D012987:Soil / Q000737:chemistry; D014908:Triticum; D003313:Zea mays
chemical_list: D005308:Fertilizers; D006540:Herbicides; D008372:Manure; D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: Adaptive-N rate; Global warming potential; GreenSeeker™; Herbicide residues; NDVI; Soil test