Improving nitrogen balance with irrigation practice and cropping system

Abstract

Nitrogen (N) balance based on N inputs, outputs, and retention in the soil shows N flows that measure 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 versus nonirrigated) 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 nonsymbiotic N fixation was 15% to 64% greater with NTB-P in the irrigated practice and 32% to 69% greater in the nonirrigated practice. Compared with CTBO and NTBO, total N output due to grain N removal, denitrification, volatilization, plant senescence, N leaching, gaseous N (NO_x) 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 nonirrigated practice. Nitrogen sequestration rate at the 0 to 10 cm depth varied from 6 kg N ha⁻¹ y⁻¹ with irrigated CTBO to 37 kg N ha⁻¹ y⁻¹ with irrigated NTBN and nonirrigated NTB-P. Nitrogen balance ranged from −54 kg N ha⁻¹ y⁻¹ with nonirrigated NTBN to 30 kg N ha⁻¹ y⁻¹ with irrigated NTB-P, with greater N surplus for irrigated NTB-P and lower N deficit for nonirrigated NTB-P. The NTB-P can sustain agronomic performance due to similar grain N removal and enhance environmental sustainability due to decreased N loss to the environment while reducing external N inputs, regardless of irrigation practices.