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Evaluation of commercial soil health tests using a medium-term cover crop experiment in a humid, temperate climate

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  • University of Guelph Ridgetown Campus
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Abstract and Figures

Background and aims Various tests have been developed for quantifying soil health, such as Haney soil health test (HSHT), Solvita, and Solvita labile amino N (SLAN). Although commercially available, their applicability in temperate agroecosystems are largely unknown. Therefore, these tests were evaluated using a medium-term cover crop (CC) experiment established in 2007 (repeated 2008). Methods Treatments of four different summer-planted CCs and a no CC control (no-CC), with a split-plot of cereal straw removal were used to assess soil health treatment differences and correlations with crop yield, soil organic C (SOC), and 2 day cumulative C mineralization (Cmin2d). Results Average crop yield with CC was 7.9 to 22% greater than no-CC depending on the year. Similarly, compared to no-CC, plots with CC had 8.4 to 9.3% greater average SOC concentrations and 5.6 to 6.5% greater Cmin2d, suggesting the suitability of this trial to evaluate soil health tests. Inconsistencies between years with HSHT, Solvita and SLAN in (i) detecting CC treatment differences and (ii) correlations with crop yield or soil indicators (SOC, Cmin2d) suggests limited the applicability of these soil health tests. Conclusions This research furthers our understanding of CC systems on soil quality, C storage and by extension agroecosystem sustainability.
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REGULAR ARTICLE
Evaluation of commercial soil health tests
using a medium-term cover crop experiment in a humid,
temperate climate
I. Chahal &L. L. Van Eerd
Received: 9 December 2017 /Accepted: 13 April 2018 /Published online: 23 April 2018
#Springer International Publishing AG, part of Springer Nature 2018
Abstract
Background and aims Various tests have been devel-
oped for quantifying soil health, such as Haney soil
health test (HSHT), Solvita, and Solvita labile amino
N (SLAN). Although commercially available, their ap-
plicability in temperate agroecosystems are largely un-
known. Therefore, these tests were evaluated using a
medium-term cover crop (CC) experiment established
in 2007 (repeated 2008).
Methods Treatments of four different summer-planted
CCs and a no CC control (no-CC), with a split-plot of
cereal straw removal were used to assess soil health
treatment differences and correlations with crop yield,
soil organic C (SOC), and 2 day cumulative C mineral-
ization (Cmin
2d
).
Results Average crop yield with CC was 7.9 to 22%
greater than no-CC depending on the year. Similarly,
compared to no-CC, plots with CC had 8.4 to 9.3%
greater average SOC concentrations and 5.6 to 6.5%
greater Cmin
2d
, suggesting the suitability of this trial
to evaluate soil health tests. Inconsistencies between
years with HSHT, Solvita and SLAN in (i) detecting
CC treatment differences and (ii) correlations with crop
yield or soil indicators (SOC, Cmin
2d
)suggestslimited
the applicability of these soil health tests.
Conclusions This research furthers our understanding
of CC systems on soil quality, C storage and by exten-
sion agroecosystem sustainability.
Keywords Catch crop .Service crops .Haney soil health
test .Soil organic carbon .Soil respiration .Carbon
dioxide .Toma to Solanum lycopersicum .Biomass
removal .Soil quality .Solvita
Abbreviations
CC Cover crop
HSHT Haney soil health test
no-CC No cover crop control
OSR Oilseed radish
OSR&Rye Mixture of oilseed radish and winter ce-
real rye
Cmin
2d
Cumulative 2 day soil C mineralization
SOC Soil organic C
SLAN Solvita labile amino N
+S Straw retained
-S Straw removed
WEOC Water extractable organic C
WEON Water extractable organic N
Introduction
Tom at o (Solanum lycopersicum L.) is an important hor-
ticultural crop in Ontario with 451,000 t produced and a
farm value of CAD $91 million in 2016 (Mailvaganam
2017). Numerous studies have been conducted
Plant Soil (2018) 427:351367
https://doi.org/10.1007/s11104-018-3653-2
Responsible Editor: Zucong Cai
I. Chahal :L. L. Van Eerd (*)
School of Environmental Sciences, University of Guelph,
Ridgetown Campus, Ridgetown, Ontario N0P2C0, Canada
e-mail: lvaneerd@uoguelph.ca
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Cover crops can shape the soil microbiome by providing different C and nutrient sources via rhizodeposits and litter, via signaling or allelopathic compounds in root exudates (directly or via other organisms), or by modifying the soil abiotic environment 13,30 . In this study, CCs affected some aspects of soil microbial structure, consistently with other soil biological, chemical and physical properties 27 . Still, short-and mid-term microbial responses were relatively minor considering CCs had been applied for 7 successive years and were also present at sampling. ...
... Besides constituting a source of C and nutrients, residues also modify soil temperature and moisture content 21 , therefore modifying the soil environment. Even so, consistently with previous results on other soil properties 27 , residue management effects in this study were smaller than CC effects, and negligible for most variables. Throughout the 8-year trial, crop residues were removed only twice while CCs were applied 6 times, but we expected clearer effects because it was carried out on the sampling year. ...
... We might have missed a transient response 53 or, alternatively, tillage accelerated residue mineralization and a large proportion of C was lost as CO 2 instead of being used for microbial growth 21 . The latter is supported by higher C mineralization levels one month before sampling 27 . In terms of composition and taxa, crop residue affected fungi more so than prokaryotes, possibly because fungi are more capable of breaking down plant cell wall polymers. ...
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... The use of soil health indicators as outcome or response variables has led to a circular logic in the broader arc of implementation and interpretation. Much of the current soil health literature essentially asks "does management change the values of these soil health indicators?" (Congreves et al., 2015;Chahal and Van Eerd, 2018;Dhakal and Islam, 2018;Diederich et al., 2019;Wade et al., 2019;Agomoh et al., 2020;Williams et al., 2020), and a change in indicators is interpreted as a change in soil health. These studies are valuable for understanding management effects and the sensitivity of indicators across contexts. ...
... While many studies have linked total soil organic matter content to productivity data (Lal et al., 2004;Congreves et al., 2015;Oldfield et al., 2019), other soil health indicators-many of which are presumed to represent smaller and more biologically active pools of soil organic matter (Wander, 2004)-have had less success. Overall, individual soil health indicators are moderately correlated with productivity (Culman et al., 2013;Chahal and Van Eerd, 2018; van Es and Karlen, 2019), providing inconsistent, yet often better information about productivity than total organic matter measurements. For example, a direct comparison showed that soil health indicators related more strongly to productivity than SOC in 12 out of 14 comparisons, although the specific preferred indicator varied by context (Hurisso et al., 2016). ...
... Uniqueness (u 2 ) is the proportion of variance that is not represented by the factors, where u 2 = 1-h 2 . uncertainty of the indicator (Hurisso et al., 2016;Chahal and Van Eerd, 2018;Gannett et al., 2019;Agomoh et al., 2020Agomoh et al., , 2021Adhikari et al., 2021), whereas our approach allows for better attribution of uncertainty. Specifically, we show that the indicators associated with our soil tilth and fertility trait-POXC, mineralizable C, soil protein, and WAS-represent a similar trait across all three contexts, though that trait does not have a consistent effect on corn silage yield in the New York-2 dataset. ...
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... Morrow et al. (2016) evaluated soil health associated with five field experiments using Haney's SHT and found it was necessary to increase the number of tests at sites with significant spatial heterogeneity to detect any management effects. Three commercially available soil health tests [Solvita CO 2 -burst test, Solvita labile amino nitrogen (SLAN), and Haney's SHT] were compared in Canada by Chahal and Van Eerd (2018), but the results showed no consistent relationship with crop yield or significant correlation with Haney's SHT scores. The three tests were also evaluated by Chu et al. (2019) for a cover crop experiment in USA established in 2013 on a no-till corn-soybean rotation. ...
... Morrow et al. (2016) evaluated soil health associated with five field experiments using Haney's SHT and found it was necessary to increase the number of tests at sites with significant spatial heterogeneity to detect any management effects. Three commercially available soil health tests [Solvita CO 2 -burst test, Solvita labile amino nitrogen (SLAN), and Haney's SHT] were compared in Canada by Chahal and Van Eerd (2018), but the results showed no consistent relationship with crop yield or significant correlation with Haney's SHT scores. The three tests were also evaluated by Chu et al. (2019) for a cover crop experiment in USA established in 2013 on a no-till corn-soybean rotation. ...
Chapter
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... To address our goal of evaluating soil health for the various cropping systems in Tennessee, we selected the CASH and ASHI methods because CASH is a comprehensive and popular soil health assessment approach, while ASHI originated in the southeast U.S. region. Numerous studies using CASH for soil health assessment revealed contrasting responses of management practices on soil health (Birri, 2020;Chahal & Van Eerd, 2018;Chahal & Van Eerd, 2019;Roper et al., 2017). For example, after an extensive evaluation, Chahal and Van Eerd (2019) recommended a weighted index of five soil health indicators over CASH for better soil health differentiation among management practices in Ontario, Canada. ...
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Agricultural practices can influence soil microbial communities, which are the primary regulators of soil carbon and nutrient cycling processes. Differences in microbial community composition have the potential to affect the fate of carbon and nutrients during decomposition and may therefore influence the retention of C and provisioning of crop nutrients in agroecosystems. Long term management-induced shifts in microbial communities and resource availability may interact to affect the microbial utilization of fresh inputs of crop residues in the short term, with lasting impacts on soil C accrual and fertility. The objective of this study was to investigate whether long-term organic and conventional management resulted in differences in microbial residue decomposition. Soils under conventional and organic management planted with annual crops or with a mix of annual crops and three years of perennial alfalfa were collected from a long-term (19 y) field study in Saskatchewan, Canada and were incubated in the laboratory with and without 13C-labelled barley residues for 98 d. We measured extracellular enzyme activities (EEAs) and the incorporation of crop residue-derived C within major microbial groups (fungi, actinobacteria, and Gram positive and negative bacteria) during decomposition. Total PLFA biomass and EEAs were highest in soils from the conventional-annual system, similar between the conventional and organic perennial systems, and similar or lowest in the organic-annual system. Crop residue additions alleviated these differences; that is, in residue-amended soils total PLFA biomass, EEAs, and the abundance of the fungal biomarker increased in the organic systems compared to the unamended soils to become similar to the conventional systems. In contrast, residue additions induced small or no changes in biomass and EEAs in the conventional-annual soils. Using 13C-PLFA-SIP we showed that the general pattern of microbial succession during decomposition was similar among soils, but that fungi and especially actinobacteria were relatively more dominant in organic compared to conventionally managed soils during early and later stages of decomposition, respectively. Thus, shifts in the decomposer community composition were greater in soils originating from organic management, possibly as a result of larger changes in resource availability during the incubation that advanced the rate of microbial succession. This may reinforce long term differences in SOC quality and nutrient availability between management regimes. Organically-managed cropping systems are particularly reliant on biological cycling of organic nutrients to support crop growth. This work reinforces the importance of adequate crop residue returns for maintaining soil function, particularly where external organic amendments are not applied to balance nutrients exported as crop products.
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Cover crops are recommended for improving soil quality; however, the assessment of their benefits to soil is difficult and has typically involved the use of tedious, destructive methods. This study evaluated the applicability of diffuse reflectance infrared fourier transform (DRIFT) spectroscopy, a rapid nondestructive method for its potential to characterize soil organic constituents and plant residue decomposition processes. Soil from a 4-yr autumn cover cropping trial with a no cover crop control was amended with crop residues and used in a 72-d incubation study where data from DRIFT spectroscopy were compared with evolved CO2 in measuring decomposition of cover crop biomass with (+S) and without (-S) corn stover residue. Treatment differences within model parameters of polysaccharide-C (1170-950 cm-1 spectral region) decomposition curves were similar to those generated from the C decay curves. All soil amendment treatments had lower C mineralization and polysaccharide decomposition rates compared with the control, which suggests that the cover crops tested have the potential in the shortterm to replenish labile organic C pools and to reduce C losses compared with the no cover crop control. In soil amended with crop residues DRIFT spectra revealed a disappearance of bands corresponding to labile polysaccharide-C during the incubation, which related to CO2 evolution and was consistent with labile aliphatic-C bands (2930 cm-1). This is the first study to demonstrate the use of DRIFT spectroscopy to assess crop residue decomposition in a soil matrix.
Article
Monitoring soil health is an important component of any land management system that sustains soil resources. As metrics of soil health, we evaluated surface soil organic matter (SOM) properties from five field experiments ranging from 2 to 30 yr old and representing diverse agroecosystems across the inland Pacific Northwest (iPNW). The SOM properties measured included soil organic C (SOC), total N, acid nonhydrolyzable C (NHC), acid nonhydrolyzable N (NHN), acid-hydrolyzable C (HC), acid-hydrolyzable N (HN), microbial biomass C (MBC), microbial biomass N (MBN), carbon mineralization (Cmin), permanganate oxidizable C (POXC), ion exchange membrane N (IEM N), and potential N mineralization (PNM). We further evaluated these SOM metrics and the Haney soil health index (SHindex) relative to the following seven criteria as a framework to judge the effectiveness of soil health tools: (i) evidence based, (ii) sensitive to change, (iii) logistically sensitive, (iv) cost effective, (v) accurate and precise, (vi) performed in situ, and (vii) valued for management decisions. Measures of active SOM were highly variable, particularly 1-d Cmin (CV, 3-53%), IEM N (CV, 9-55%), and SHindex (CV, 4-37%) and subsequently not highly sensitive to management. Permanganate oxidizable C displayed sensitivity to more stabilized SOM, indicated by strong correlations to NHC (r = 0.84) and NHN (r = 0.80), and coupled with IEM N provided complimentary information important to soil health. Using these seven criteria to gauge soil health metrics, POXC scored the highest and should be considered as a component for soil health assessment within the iPNW. © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA. All Rights reserved.