Relating four‐day soil respiration to corn nitrogen fertilizer needs across 49 U.S. Midwest fields

Abstract

Soil microbes drive biological functions that mediate chemical and physical processes necessary for plants to sustain growth. Laboratory soil respiration has been proposed as one universal soil health indicator representing these functions, potentially informing crop and soil management decisions. Research is needed to test the premise that soil respiration is helpful for profitable in‐season nitrogen (N) rate management decisions in corn (Zea mays L.). The objective of this research was two‐fold: (i) determine if the amount of N applied at the time of planting effected soil respiration, and (ii) evaluate the relationship of soil respiration to corn yield response to fertilizer N application. A total of 49 N response trials were conducted across eight states over three growing seasons (2014–2016). The 4‐day Comprehensive Assessment of Soil Health (CASH) soil respiration method was used to quantify soil respiration. Averaged over all sites, N fertilization did not impact soil respiration, but at four sites soil respiration decreased as N fertilizer rate applied at‐planting increased. Across all site‐years, soil respiration was moderately related to the economical optimum N rate (EONR) (r2 = 0.21). However, when analyzed by year, soil respiration was more strongly related to EONR in 2016 (r2 = 0.50) and poorly related for the first two years (r2 < 0.20). These results illustrate the factors influencing the ability of laboratory soil respiration to estimate corn N response, including growing‐season weather, and the potential of fusing soil respiration with other soil and weather measurements for improved N fertilizer recommendations.

Carbon dioxide flush as a soil health indicator related to soil properties and crop yields

“…Our results of nonsignificant difference in 1dC and 4dC between N fertilization treatments in Sidney was also in contrast with that obtained by Sainju, Caesar-Tonthat, Lenssen, and Barsotti (2012) who reported greater flush with 80 than with 0 kg N ha −1 . Mac Bean et al (2020) found that N fertilization decreased 4dC compared with no N fertilization at four sites but did not affect it at 45 sites in U.S. Midwest. Nitrogen fertilization can variably affect CO 2 flux (Al-Kaisi et al, 2008;Sainju et al, 2010).…”

“…Several researchers (Haney et al, 2001;Franzluebbers, 2016) also reported that CO 2 flushes at 1-to 3-d incubations were related to forage N uptake. Others (Mac Bean et al, 2020;Roper et al, 2017) found that 4dC was not consistently related to crop yield, although significant relationship occurred in years with favorable weather condition. They suggested that the relationship should be examined in regions with particular soil type, climatic condition, and management practice rather than using it for the comprehensive interpretation of soil health indicator for broad regions.…”

“…Similarly, Alves de Castro Lopes et al (2013) reported that CO 2 flush at 7-d incubation was related to crop yield in Brazil. Several researchers (Mac Bean et al, 2020;Yost et al, 2018) found that 4dC was moderately related to economical optimum N rate for corn production. In contrast, Roper et al (2017) found that 4dC was not related to crop yields in North Carolina.…”

“…It may be possible that the nonsignificant effect of N fertilization on CO 2 flux, shorter duration of the experiment, and medium soil texture resulted on nonrelationship between 1dC and 4dC in Sidney compared with Froid where the relationship was significant. Several researchers (Franzluebbers, 2016;Mac Bean et al, 2020) reported that CO 2 flushes at 3-to 4-d incubations were 2.5-3 times greater than at 1-d incubation, and that these flushes were highly related. Although longer duration of the incubation may have increased 4dC compared with 1dC, and soil CO 2 flush measured by the infrared gas analyzer and alkali trap are highly correlated (Haney et al, 2008), the greater 4dC than 1dC in our study compared with those observed by several researchers (Franzluebbers, 2016;Mac Bean et al, 2020) was probably due to differences in soil and climatic conditions among regions, type of crops grown, and management practices.…”

“…Because it takes a long time to measure N mineralization potential and farmers often do not take account for soil N mineralization while applying N fertilizers to crops, excessive N fertilization can often lead to increased accumulation of soil residual N that can degrade soil and environmental quality. Measurement of CO 2 flush can estimate N mineralization potential of the soil that can be used to adjust N fertilization rates to crops, reducing the degradation of soil and environmental quality (Franzluebbers et al, 2000;Haney et al, 2001;Mac Bean et al, 2020). The CO 2 flush is also affected by soil bulk density (Franzluebbers, 1999;Torbert & Wood., 1992) and water content, as these influence microbial activity (Franzluebbers, 1999; Harris,…”