Abstract

Nitrogen balance in agroecosystems provides a quantitative framework of N inputs and outputs and retention in the soil that examines the sustainability of agricultural productivity and soil and environmental quality. Nitrogen inputs include N additions from manures and fertilizers, atmospheric depositions including wet and dry depositions, irrigation water, and biological N fixation. Nitrogen outputs include N removal in crop grain and biomass and N losses through leaching, denitrification, volatilization, surface runoff, erosion, gas emissions, and plant senescence. Nitrogen balance, which is the difference between N inputs and outputs, can be reflected in changes in soil total (organic+inorganic) N during the course of the experiment duration due to N immobilization and mineralization. While increased soil N retention and mineralization can enhance crop yields and decrease N fertilization rate, reduced N losses through N leaching and gas emissions (primarily NH4 and NOx emissions, out of which N2O is a potent greenhouse gas) can improve water and air quality.•This paper discusses measurements and estimations (for non-measurable parameters due to complexity) of all inputs and outputs of N as well as changes in soil N storage during the course of the experiment to calculate N balance.•The method shows N flows, retention in the soil, and losses to the environment from agroecosystems.•The method can be used to measure agroecosystem performance and soil and environmental quality from agricultural practices.

Highlights

  • A positive value of N balance indicates that N is gained in the system and negative value indicates loss

  • To determine soil total N, soil samples are collected from various places within a treatment, composited, air-dried, and ground to 2 mm, from which a subsample is used for N analysis

  • If samples are collected at multiple depths, samples from various places are composited by depth and prepared as above

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Summary

Nitrogen balance

Where N inputs = N fertilization from inorganic N fertilizers + N fertilization from manures and amendments + atmospheric N depositions (rain, snow, and dry deposition) + biological N fixation (symbiotic + non-symbiotic N fixation) + irrigation water + crop seed. A positive value of N balance indicates that N is gained in the system and negative value indicates loss. This, occurs rarely due to various factors, such as variations in soil and climatic conditions, N management, soil and crop management practices, and difficulty in measurement of some parameters, such as atmospheric N depositions, biological N fixation, and N losses through various processes.

Soil total nitrogen
Nitrogen inputs
Nitrogen outputs
Findings
Additional information
Full Text
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