Nitrogen balance in response to irrigation practice and cropping system

Authors: Sainju, Upendra

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2018
Publication Date: 11/2/2019
Citation: Sainju, U.M. 2019. Nitrogen balance in response to irrigation practice and cropping system. Journal of Soil and Water Conservation. 74(6):622-631. https://doi.org/10.2489/jswc.74.6.622.
DOI: https://doi.org/10.2489/jswc.74.6.622

Interpretive Summary: Legume-nonlegume rotation showed improved nitrogen balance and enhanced agronomic sustainability. Application of nitrogen fertilizer can enhance crop yields, but excessive applications beyond crops’ need can degrade soil and environmental quality. Accounting of all nitrogen inputs, outputs, and retention in soil in the long-term agroecosystem provides a framework of nitrogen flows and agronomic sustainability. ARS scientist in Sidney, MT reported that no-till barley-pea rotation with reduced nitrogen rate increased nitrogen surplus in the irrigated system and deficit in the non-irrigated system compared with no-till or till continuous barley with or without recommended nitrogen rate by reducing nitrogen fertilization rate and nitrogen loss to the environment while sustaining crop nitrogen uptake. No-till legume-nonlegume rotation can enhance agronomic sustainability and reduce external nitrogen inputs compared with continuous nonlegumes.

Technical Abstract: Nitrogen balance based on N inputs, outputs, and retention in the soil shows N flows that measures agroecosystem performance and environmental sustainability. Complexity of measurements of some parameters and constraints on time, labor, and cost have resulted in limited studies on N balance in agroecosystems. The objective of this study was to measure N balance based on N inputs and outputs and soil N retention in response to irrigation and cropping system from 2006 to 2011 in the northern Great Plains. Treatments were two irrigation practices (irrigated vs. non-irrigated) as the main plot and five cropping systems (conventional till barley (Hordeum vulgare L.) with N fertilizer [CTBN], conventional till barley without N fertilizer [CTBO], no-till barley-pea [Pisum sativum L.] with N fertilizer [NTB-P], no-till barley with N fertilizer [NTBN], and no-till barley without N fertilizer [NTBO]) as the split plot treatment arranged in a randomized block design with three replications. Compared with other cropping systems, total N input due to N fertilization, pea N fixation, soil N mineralization, atmospheric N deposition, crop seed N, and non-symbiotic N fixation was 15 to 64% greater with NTB-P in the irrigated practice and 32 to 69% greater in the non-irrigated practice. Compared with CTBO and NTBO, total N output due to grain N removal, denitrification, volatilization, plant senescence, N leaching, gaseous N (NOx) emissions, and surface runoff was 66 to 74% greater with NTB-P, CTBN, and NTBN in the irrigated practice and 46 to 53% greater in the non-irrigated practice. Nitrogen sequestration rate at the 0 to 10 cm depth varied from 6 kg N ha-1 yr-1 with irrigated CTBO to 37 kg N ha-1 yr-1 with irrigated NTBN and non-irrigated NTB-P. Nitrogen balance ranged from -54 kg N ha-1 yr-1 with non-irrigated NTBN to 30 kg N ha-1 yr-1 with irrigated NTB-P, with greater N surplus for irrigated NTB-P and lower N deficit for non-irrigated NTB-P. The NTB-P can sustain agronomic performance due to similar grain N removal and enhance environmental sustainability decreased N loss to the environment while reducing external N inputs, regardless of irrigation practices.