scholarly journals Mixing crop residues induces a synergistic effect on microbial biomass and an additive effect on soil organic matter priming

2021 ◽  
Author(s):  
Xin Shu ◽  
Yiran Zou ◽  
Liz J Shaw ◽  
Lindsay Todman ◽  
Mark Tibbett ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Synergistic Effect ◽  
Cover Crop ◽  
Crop Residues ◽  
Plant Residue ◽  
Arable Soils ◽  
Soil Microbial ◽  
Quaternary Mixture ◽  
Individual Residue ◽  
The Individual

Applying crop residues is a widely used strategy to increase soil organic matter (SOM) in arable soils because of its recorded effects on increasing microbial biomass and consequently necromass. However, fresh residue inputs could also prime the decomposition of native SOM, resulting in accelerated SOM depletion and greenhouse gas (GHG) emission. Increasing the botanical diversity of the crops grown in arable systems has been promoted to increase the delivery of multiple ecological functions, including increasing soil microbial biomass and SOM. Whether mixtures of fresh residues from different crops grown in polyculture contribute to soil carbon (C) pools to a greater extent than would be expected from applying individual residues (i.e., the mixture produces a non-additive synergistic effect) has not been systematically tested and is currently unknown. In this study, we used 13C isotope labelled cover crop residues (i.e., buckwheat, clover, radish, and sunflower) to track the fate of plant residue-derived C and C derived from the priming of SOM in treatments comprising a quaternary mixture of the residues and the average effect of the four individual residues one day after residue incorporation in a laboratory microcosm experiment. Our results indicate that, despite all treatments receiving the same amount of plant residue-derived C (1 mg C g-1 soil), the total microbial biomass in the treatment receiving the residue mixture was significantly greater, by 26% (3.69 μg C g-1), than the average microbial biomass observed in treatments receiving the four individual components of the mixture one day after applying crop residues. The greater microbial biomass C in the quaternary mixture, compared to average of the individual residue treatments, that can be attributed directly to the plant residue applied was also significantly greater, by 132% (3.61 μg C g-1). However, there was no evidence that the mixture resulted in any more priming of native SOM than average priming observed in the individual residue treatments. The soil microbial community structure, assessed using phospholipid fatty acid (PLFA) analysis, was significantly (P < 0.001) different in the soil receiving the residue mixture, compared to the average structures of the communities in soil receiving four individual residues. Differences in the biomass of fungi, general bacteria, and Gram-positive bacteria were responsible for the observed synergistic effect of crop residue mixtures on total microbial biomass and residue-derived microbial biomass, especially biomarkers 16:0, 18:2ω6 and 18:3ω3. Our study demonstrates that applying a mixture of crop residues increases soil microbial biomass to a greater extent than would be expected from applying individual residues and that this occurs either due to faster decomposition of the crop residues or greater carbon use efficiency (CUE), rather than priming the decomposition of native SOM. Therefore, growing crop polycultures (e.g., cover crop mixtures) and incorporating mixtures of the resulting crop residues into the soil could be an effective method to increase microbial biomass and ultimately C stocks in arable soils.

The mixture of cover crop residues induced a synergistic effect on microbial communities and an additive effect on soil organic matter priming

2021 ◽  
Author(s):  
Xin Shu ◽  
Yiran Zou ◽  
Liz Shaw ◽  
Lindsay Todman ◽  
Mark Tibbett ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Cover Crop ◽  
Crop Residue ◽  
Soil Microbial Biomass ◽  
Crop Residues ◽  
Soil Microbial ◽  
Quaternary Mixture ◽  
Individual Residue ◽  
The Individual ◽  
Som Decomposition

&lt;p&gt;Applying cover crop residues to increase soil organic matter (SOM) is a widely used strategy to sustainably intensify agricultural systems.&amp;#160; However, fresh residue inputs create &amp;#8220;hot spots&amp;#8221; of microbial activity during decomposition which could also &amp;#8220;prime&amp;#8221; the decomposition of native SOM, resulting in accelerated SOM depletion and greenhouse gas emissions. Microbes exert control over SOM decomposition and stabilisation as a consequence of their carbon use efficiency (CUE), the balance between microbial catabolism and anabolism. The CUE during residue decomposition and the extent to which native SOM decomposition is primed by residue addition may depend on residue biochemical quality.&amp;#160; Given that cover crops may be grown in monoculture, or in species mixes with the aim of providing multiple benefits to agricultural ecosystem services, it is important to understand whether applying cover crop residues as a mixture results in a different CUE and soil carbon stock, than would be expected by observations made on the application of individual residues. We used &lt;sup&gt;13&lt;/sup&gt;C labelled cover crop residues (buckwheat, clover, radish, and sunflower) to track the fate of cover crop residue-derived carbon and SOM derived carbon in treatments comprising a quaternary mixture of the residues and the average effect of the four individual residues (non-mixture) one day after residue incorporation in a laboratory microcosm experiment. The soil microbial community composition was measured by phospholipid-derived fatty acids (PLFA) fingerprint. Our results indicate that, despite all treatments receiving the same amount of plant-added carbon (1 mg C g&lt;sup&gt;-1&lt;/sup&gt; soil), the total microbial biomass (&lt;sup&gt;12&lt;/sup&gt;C + &lt;sup&gt;13&lt;/sup&gt;C) in the treatment receiving the residue mixture was significantly greater, by 3.69 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt;, than the average microbial biomass observed in the four treatments receiving individual components of the mixture. The microbial biomass in the quaternary mixture, compared to the average of the individual residue treatments, that can be attributed directly to the plant matter applied, was also significantly greater by 3.61 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt;. However, there was no evidence that the mixture resulted in any more priming of native SOM than average priming observed in the individual residue treatments. The soil microbial community structure measured by analysis of similarities (ANOSM) was significantly different in the soil receiving the residue mixture, compared to the average structure of the four communities in soils receiving individual residues. Differences in the biomass of fungi and Gram-positive bacteria were responsible for the observed synergistic effect of cover crop residue mixtures on total microbial biomass and plant-derived microbial biomass; especially biomarkers 16:0, 18:1&amp;#969;9, 18:2&amp;#969;6 and 18:3&amp;#969;3. Our study demonstrates that applying a mixture of cover crop residues initially increases soil microbial biomass to a greater extent than would be expected from applying individual components of the mixture and that this increase may occur either due to faster decomposition of the cover crop residues or greater CUE, but not due to greater priming of native SOM decomposition. Therefore, applying cover crop residue mixtures could be an effective method to increase soil microbial biomass, and ultimately soil carbon stocks in arable soils.&lt;/p&gt;

Do diverse mixtures of cover crop residues alter the soil microbial community and increase soil function?

2020 ◽  
Author(s):  
Xin Shu ◽  
Yiran Zou ◽  
Liz Shaw ◽  
Lindsay Todman ◽  
Mark Tibbett ◽  
...  
Keyword(s):  
Microbial Community ◽  
Soil Respiration ◽  
Cover Crops ◽  
Soil Microbial Community ◽  
Cover Crop ◽  
Crop Residues ◽  
Soil Health ◽  
Soil Function ◽  
Soil Microbial ◽  
Quaternary Mixture

&lt;p&gt;Cover crops are a contemporary tool to sustainably manage agricultural soils by boosting fertility, suppressing weeds and disease, and benefiting cash crop yields, thus securing future food supply. Due to the different chemical composition of crop residues from different plant families, we hypothesised that a mixture of cover crop residues may have a greater potential to improve soil health than the sum of the parts. Our experiment focused on the impact of four cover crops (clover, sunflower, radish and buckwheat) and their quaternary mixture on soil respiration and the soil microbial community in an 84-day microcosm experiment. On average adding cover crop residues significantly (P &lt; 0.001) increased soil respiration from 29 to 343 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt; h&lt;sup&gt;-1&lt;/sup&gt; and microbial biomass from 18 to 60 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt;, compared to the unamended control during 84 days&amp;#8217; incubation. Cover crop addition resulted in a significant (P &lt; 0.001) alteration of the soil microbial community structure compared to that of the control. The quaternary mixture of cover crop residues significantly (P = 0.011) increased soil respiration rate by 23.79 &amp;#181;g C g&lt;sup&gt;-1&lt;/sup&gt; h&lt;sup&gt;-1&lt;/sup&gt; during the period 30 to 84 days after residue incorporation, compared to the average of the four individual residues. However, no significant difference in the size of the microbial biomass was found between the mixture and the average of the four individuals, indicating the mixture may invest resources which transit dormant microbial species into a metabolically active state and thus boost microbial respiration. Analysis of similarity of microbial community composition (ANOSIM) demonstrated the mixture significantly (P = 0.001) shifted microbial community structure away from buckwheat (R = 0.847), clover (R = 0.688), radish (R = 0.285) and sunflower (R = 0.785), respectively. This implies cover crop residues provide a niche specialization and differentiation on a selection of microbial communities that favour certain plant compounds. While applying cover crop residues has positive impacts on soil function, we found that applying a mixture of cover crop residues may provide greater potential to select for microorganisms or activate dormant microbial species which result in higher soil function. The outcome of this study will help seed suppliers to design, and farmers to select, novel cover crop mixtures which enhance soil function synergistically, leading to a greater potential to sustainably improve soil health.&lt;/p&gt;

scholarly journals Cover crop residue diversity enhances microbial activity and biomass with additive effects on microbial structure

2021 ◽  
Author(s):  
Xin Shu ◽  
Yiran Zou ◽  
Liz J. Shaw ◽  
Lindsay Todman ◽  
Mark Tibbett ◽  
...  
Keyword(s):  
Microbial Community ◽  
Microbial Biomass ◽  
Soil Respiration ◽  
Microbial Activity ◽  
Cover Crop ◽  
Crop Residue ◽  
Soil Microbial Biomass ◽  
Crop Residues ◽  
Soil Functions ◽  
Soil Microbial

AbstractCover crops have been widely used in agroecosystems to improve soil fertility and environmental sustainability. The decomposition of cover crop residues can have further effects on belowground communities and their activity, which is important for a series of soil functions (e.g., nutrient cycling and organic matter decomposition). We tested the effect of plant residues from a range of cover crop species on soil microbial activity and community assemblage. We predicted that cover crop residues would alter the soil microbial community and that a greater diversity of residues would enhance microbial decomposition. In an incubation study, we assessed the effect of crop residue diversity on microbial activity (soil respiration) and its consequent effects on microbial community composition (PLFA). We used either a biodiverse mixture of four cover crop residues (buckwheat, clover, sunflower and radish) or an equal mass of the residues of each of the individual species. The diverse mixture of cover crop residues had a significantly (P < 0.05) greater soil respiration rate, by 57.61 µg C g−1 h−1, than the average of the four individual residues, but did not have a significantly different soil microbial biomass or microbial community structure. This finding could be attributed to a greater diversity of organic resources increasing the number biochemical niches, and hence activating dormant microbial communities to increase microbial activity without affecting microbial biomass or community composition. Greater respiration from similar microbial biomasses suggests that microbial activity might be more efficient after a more diverse substrate input. This study confirms the positive impact of cover crop residues on soil microbial biomass and activity and highlights that mixtures of cover crop residues may deliver enhanced soil functions beyond the sum of individual cover crop residues.

Distribution of carbon and nitrogen in a long-term cropping system and permanent pasture system

1993 ◽  
Vol 44 (6) ◽  
pp. 1323 ◽  
Author(s):  
FA Robertson ◽  
RJK Myers ◽  
PG Saffigna
Keyword(s):  
Microbial Biomass ◽  
Crop Residues ◽  
Perennial Grass ◽  
Cropping System ◽  
N Availability ◽  
Continuous Cropping ◽  
Organic C ◽  
Soil Microbial ◽  
Permanent Pasture ◽  
Standing Dead

Nitrogen (N) limitation to productivity of sown perennial grass pastures on the brigalow lands of S.E. Queensland contrasts with adequate N supply to annual crops grown on the same soil. In order to understand this anomaly, the distribution of N and carbon (C) under permanent green panic pasture and under continuous cropping with grain sorghum was compared in an 18 month field study. Total soil N and organic C (0-10 cm) were, respectively, 0.37 and 3.20% under green panic and 0.23 and 2.31% under sorghum. Soil microbial biomass (0-28 cm) contained 246 kg N and 1490 kg C ha-1 under green panic and 147 kg N and 744 kg C ha-1 under sorghum. Enhanced microbial growth under pasture was attributed to the continuous input of available C from surface litter and roots. The C/N ratio of pasture residues was high (greater than 50) and conducive to immobilization of N. Availability of N under pasture was further reduced by approximately 50% of plant N being immobilized in standing dead tissue. Under sorghum, the microbial biomass was well supplied with N, but was limited by C availability. The soil under sorghum received a single large C input when crop residues were returned after harvest. The differences in N availability, and hence productivity, of these soils under cropping and permanent pasture were due primarily to differences in the timing and quality of C inputs.

An integrated mechanical and chemical method for managing prostrate cover crops on permanent beds

2011 ◽  
Vol 27 (2) ◽  
pp. 148-156 ◽  
Author(s):  
N.R. Hulugalle ◽  
L.A. Finlay ◽  
T.B. Weaver
Keyword(s):  
Carbon Footprint ◽  
Cover Crops ◽  
Cover Crop ◽  
Management System ◽  
Chemical Method ◽  
Crop Residues ◽  
Maximum Depth ◽  
Average Increase ◽  
The Individual

AbstractCover crops in minimum or no-tilled systems are usually killed by applying one or more herbicides, thus significantly increasing costs. Applying herbicides at lower rates with mechanical interventions that do not disturb or bury cover crop residues can, however, reduce costs. Our objective was to develop a management system with the above-mentioned features for prostrate cover crops on permanent beds in an irrigated Vertisol. The implement developed consisted of a toolbar to which were attached spring-loaded pairs of parallel coulter discs, one set of nozzles between the individual coulter discs that directed a contact herbicide to the bed surfaces to kill the cover crop and a second set of nozzles located to direct the cheaper glyphosate to the furrow to kill weeds. The management system killed a prostrate cover crop with less trafficking, reduced the use of more toxic herbicides, carbon footprint, labor and risk to operators. Maximum depth of compaction was more but average increase was less than that with the boom sprayer control.

scholarly journals Production and Decomposition of Cover Crop Residues and Associations With Soil Organic Fractions

2019 ◽  
Vol 11 (5) ◽  
pp. 58
Author(s):  
José Carlos Mazetto Júnior ◽  
José Luiz Rodrigues Torres ◽  
Danyllo Denner de Almeida Costa ◽  
Venâncio Rodrigues e Silva ◽  
Zigomar Menezes de Souza ◽  
...  
Keyword(s):  
Cover Crops ◽  
Cover Crop ◽  
Crop Residues ◽  
Soil Layer ◽  
Additional Treatment ◽  
Plant Residue ◽  
Plant Residues ◽  
Vegetable Crops ◽  
Residue Decomposition ◽  
Sunn Hemp

The decomposition of plant residues, the changes in the total organic carbon (TOC) and the fractions of soil organic matter (SOM) occur differently in irrigated areas. The objective of this study was to quantify the biomass production, the decomposition of cover crops residues and relate them with the changes n the content and fractions of SOM in an irrigated area of vegetable crops. Six types of cover crop treatments were evaluated: brachiaria (B); sunn hemp (S); millet (M); B + S; B + M; S + M, plus an additional treatment (native area), with 4 repetitions. The production of fresh (FB) and dry biomass (DB), the rate of plant residue decomposition, TOC, SOM fractions and the coefficient of SOM (QSOM) were quantified. It was observed that the greatest and the lowest volume of crop residues were from the B and S cover crop, respectively. The cover crops in monoculture presented great decomposition rates and short half-life when compared to mixtures of cover crop. The TOC and QSOM were great in the 0 to 0.05 m soil layer, and in the M + S cover crop mixture, when compared to the 0.05 to 0.1 m soil layer and to other cover crops. Among the SOM fractions, the humin predominated in the most superficial soil layer (0 to 0.05 m).

Soil microbiological properties during decomposition of crop residues under conventional and zero tillage

2004 ◽  
Vol 84 (4) ◽  
pp. 411-419 ◽  
Author(s):  
N. Z. Lupwayi ◽  
G. W. Clayton ◽  
J. T. O’Donovan ◽  
K. N. Harker ◽  
T. K. Turkington ◽  
...  
Keyword(s):  
Microbial Biomass ◽  
Microbial Diversity ◽  
Microbial Activity ◽  
Soil Quality ◽  
Functional Diversity ◽  
Crop Residue ◽  
Crop Residues ◽  
Zero Tillage ◽  
Microbial Functional Diversity ◽  
Soil Microbial

Field experiments were conducted to correlate decomposition of red clover (Trifolium pratense) green manure (GM), field pea (Pisum sativum), canola (Brassica rapa) and wheat (Triticum aestivum) residues, and soil organic C (SOC), under zero tillage and conventional tillage, with soil microbial biomass C (MBC), bacterial functional diversity and microbial activity (CO2 evolution). A greenhouse experiment was also conducted to relate crop residue quality to soil microbial characteristics. Zero tillage increas ed MBC only in the 0- to 5-cm soil layer. Soil MBC decreased more with soil depth than either microbial diversity or total SOC. Legume GM residues induced greater initial CO2 evolution than the other residues. This means that results that do not include the initial flush of microbial activity, e.g., by sampling only in the season(s) following residue placement, probably underestimate gas evolution from legume crop residues. Residue N, P and K contents were positively correlated with microbial functional diversity and activity, which were positively correlated with crop residue decomposition. Therefore, microbial functional diversity and activity were good indicators of microbial decomposition processes. Residue C/N and C/P ratios (i.e., high C content) were positively correlated with MBC, which was positively correlated with SOC. Therefore, soil MBC was a good indicator of soil quality (soil organic matter content). Key words: Biological soil quality, crop residues, crop rotation, microbial activity, microbial biomass, microbial diversity

scholarly journals Soil microbial biomass under different management and tillage systems of permanent intercropped cover species in an orange orchard

2011 ◽  
Vol 35 (6) ◽  
pp. 1873-1883 ◽  
Author(s):  
Elcio Liborio Balota ◽  
Pedro Antonio Martins Auler
Keyword(s):  
Microbial Biomass ◽  
Cover Crop ◽  
Soil Microbial Biomass ◽  
Ground Cover ◽  
Tree Canopy ◽  
Soil Tillage ◽  
Tillage Systems ◽  
Brachiaria Humidicola ◽  
Soil Microbial ◽  
Leguminous Species

To mitigate soil erosion and enhance soil fertility in orange plantations, the permanent protection of the inter-rows by cover species has been suggested. The objective of this study was to evaluate alterations in the microbial biomass, due to different soil tillage systems and intercropped cover species between rows of orange trees. The soil of the experimental area previously used as pasture (Brachiaria humidicola) was an Ultisol (Typic Paleudult) originating from Caiuá sandstone in the northwestern part of the State of Paraná, Brazil. Two soil tillage systems were evaluated: conventional tillage (CT) in the entire area and strip tillage (ST) (strip width 2 m), in combination with different ground cover management systems. The citrus cultivar 'Pera' orange (Citrus sinensis) grafted onto 'Rangpur' lime rootstock was used. Soil samples were collected after five years of treatment from a depth of 0-15 cm, under the tree canopy and in the inter-row, in the following treatments: (1) CT and an annual cover crop with the leguminous species Calopogonium mucunoides; (2) CT and a perennial cover crop with the leguminous peanut Arachis pintoi; (3) CT and an evergreen cover crop with Bahiagrass Paspalum notatum; (4) CT and a cover crop with spontaneous Brachiaria humidicola grass vegetation; and (5) ST and maintenance of the remaining grass (pasture) of Brachiaria humidicola. Soil tillage and the different cover species influenced the microbial biomass, both under the tree canopy and in the inter-row. The cultivation of brachiaria increased C and N in the microbial biomass, while bahiagrass increased P in the microbial biomass. The soil microbial biomass was enriched in N and P by the presence of ground cover species and according to the soil P content. The grass species increased C, N and P in the soil microbial biomass from the inter-row more than leguminous species.

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