Influence of Nitrogen Fertilization Rate on Soil Respiration: A Study Using a Rapid Soil Respiration Assay

Debankur Sanyal,Anthony Bly,Johnathon Wolthuizen

doi:10.3390/nitrogen2020014

Abstract

Efficient nitrogen (N) management is one of the primary objectives of agronomic research as N is expensive and a major environmental pollutant. Soil microbes regulate N cycling and soil respiration (SR) measures soil microbial activity. The Comprehensive Assessment of Soil Health (CASH) soil respiration protocol is a rapid test, and a study was designed to approve this test as a potential tool for corn (Zea mays L.) N management. Five locations were selected around South Dakota (SD) where corn received 0, 45, 90, and 180 kg N ha−1 during summer of 2019. Soil samples were collected before planting and at the V6 corn growth stage to measure SR. We found that N fertilization increased SR and the highest SR was recorded at Ipswich (1.94 mg CO2 g−1) while SR was lowest at Bushnell (1.45 mg CO2 g−1). Higher SR was recorded at the sites where no-till farming was practiced, and soil had higher initial nitrate and organic matter content. SR was weakly correlated with corn grain yield, which indicated a potential area for future research. We concluded that split N application or an additional N application at a later growth stage might boost corn productivity in soil with higher microbial activity.

Highlights

The essentiality of nitrogen (N) in sustaining soil fertility and crop production is well defined and many agronomic research have been directed toward finding the best N management for optimal crop yield [1,2,3,4]
We found that the Comprehensive Assessment of Soil Health (CASH) and Haney methods correlate well (R2 = 0.98) in estimating soil respiration (SR) (Figure 2) and can be used as a standardized method in estimating SR; similar findings were reported by [23]
The CASH method is comparatively rapid and recent; we used this method to determine the impact of N rate on SR during corn growing season

Summary

Introduction

The essentiality of nitrogen (N) in sustaining soil fertility and crop production is well defined and many agronomic research have been directed toward finding the best N management for optimal crop yield [1,2,3,4]. Soil microbes play a major role in N cycling in soil. Fertilizer N can be lost into the atmosphere through gaseous forms of N, ammonia (NH3), nitrous oxide (N2O), and dinitrogen (N2) or can leach down through the soil profile or runoff from the soil surface as nitrates (NO3−), nitrite (NO2), and ammonium (NH4+) [12], and microbes play a crucial part in all of these transformations [13]. Microbial uptake of NO3− and ammonium (NH4+) is an integral part of N dynamics in soil and, N addition should stimulate soil respiration (SR) [14]. Additions of N in an N-limited soil was reported to stimulate an increase in SR initially, and with time created a C-limited state as N demand diminished [19]

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