Potential long-term, global effects of enhancing the domestic terrestrial carbon sink in the United States through no-till and cover cropping.

BACKGROUND: Achieving a net zero greenhouse gas United States (US) economy is likely to require both deep sectoral mitigation and additional carbon dioxide removals to offset hard-to-abate emissions. Enhancing the terrestrial carbon sink, through practices such as the adoption of no-till and cover cropping agricultural management, could provide a portion of these required offsets. Changing domestic agricultural practices to optimize carbon content, however, might reduce or shift US agricultural commodity outputs and exports, with potential implications on respective global markets and land use patterns. Here, we use an integrated energy-economy-land-climate model to comprehensively assess the global land, trade, and emissions impacts of an adoption of domestic no-till farming and cover cropping practices based on carbon pricing. RESULTS: We find that the adoption of these practices varies depending on which aspects of terrestrial carbon are valued. Valuation of all terrestrial carbon resulted in afforestation at the expense of domestic agricultural production. In contrast, a policy valuing soil carbon in agricultural systems specifically indicates strong adoption of no-till and cover cropping for key crops. CONCLUSIONS: We conclude that under targeted terrestrial carbon incentives, adoption of no-till and cover cropping practices in the US could increase the terrestrial carbon sink with limited effects on crop availability for food and fodder markets. Future work should consider integrated assessment modeling of non-CO2 greenhouse gas impacts, above ground carbon storage changes, and capital and operating cost considerations.

Effects of gravel-sand and plastic film mulching on soil water and temperature retention in cold and arid regions without irrigation.

Gravel-sand mulch (GSM) and plastic film mulch (PFM) are important ways of farming in cold and arid regions without irrigation. Nevertheless, there has been a lack of studies of the system response to live weather conditions. To quantify the effects of GSM and PFM on soil moisture and temperature retention, in-situ monitoring experiments were carried out in the arid belt of central Ningxia, China, using continuous monitoring of the field soil water and meteorological conditions at a 30-mimute time-step under three treatments: a bare soil (CK), soil covered by a layer of GSM, and soil covered by GSM and a layer of plastic film (i.e., GSM + PFM). Results show that: (1) With a limited precipitation of 221 mm during the growing season, the average volumetric soil water content (SWC) in the top 30-cm soil layer was lowest for CK, medium high for GSM, and highest for GSM + PFM. Compared to CK, the soil water storage increased by 54 % under GSM and 75.2 % under GSM + PFM; (2) The most frequently occurring low-intensity rainfalls are more efficiently stored in soil under GSM + PFM; (3) Similarly, the soil temperature was significantly increased under GSM and GSM + PFM conditions. Compared to CK, the average soil temperature in the top 5-cm layer increased by 2.5 °C under GSM and 4.8 °C under GSM + PFM during the germination period, which had effectively extended the growing season for about 30 and 50 days, respectively; (4) Although dewfall is only 4 % of rainfall, the total number of dew day was more than twice that of rain day. Thus, dewfall is a more frequent and dependable source of water for native plants and animals. Our results demonstrate that the benefits of GSM and PFM can be applied globally where either insufficient rainfall or low temperatures are limiting factors.

Modelling pesticide degradation and leaching in conservation agriculture: Effect of no-till and mulching.

No-till and mulching are typical management operations in conservation agriculture (CA). To model pesticide degradation and leaching under a CA scenario, as compared to a conventional-tillage scenario (CT), the mulch module of the agro-hydrological model Daisy was extended. A Daisy soil column was parameterized with measurements of topsoil, mulch, and a realistic subsoil, and tested against published experimental data of pesticide fate in laboratory soil columns covered by mulch. Uncertainty and sensitivity analyses of the new Daisy version were conducted for a series of weather, soil, pesticide, and mulch parameters, using 4939 Monte Carlo simulations under each scenario. Results showed that there was no systematic difference in pesticide leaching from the topsoil (to the subsoil and directly to drains via drain-connected biopores) between CA and CT, but pesticide degradation and sorption were significantly different; degradation in the mulch and uppermost soil surface layer (0-3.5 cm) was larger in CA while degradation was larger in CT when considering the whole topsoil (0-30 cm). This difference for the whole topsoil could be explained by pesticide interception in CA in the part of the mulch not in direct contact with the soil where degradation is assumed not to occur. The sensitivity analysis highlighted non-influential parameters and seven parameters out of twenty-five to be better estimated to improve the accuracy of the predictions.

Spatio-temporal microbial regulation of aggregate-associated priming effects under contrasting tillage practices.

Tillage intensity significantly influences the heterogeneous distribution and dynamic changes of soil microorganisms, consequently shaping spatio-temporal patterns of SOC decomposition. However, little is known about the microbial mechanisms by which tillage intensity regulates the priming effect (PE) dynamics in heterogeneous spatial environments such as aggregates. Herein, a microcosm experiment was established by adding 13C-labeled straw residue to three distinct aggregate-size classes (i.e., mega-, macro-, and micro-aggregates) from two long-term contrasting tillage histories (no-till [NT] and conventional plow tillage [CT]) for 160 days to observe the spatio-temporal variations in PE. Metagenomic sequencing and Fourier transform mid-infrared techniques were used to assess the relative importance of C-degrading functional genes, microbial community succession, and SOC chemical composition in the aggregate-associated PE dynamics during straw decomposition. Spatially, straw addition induced a positive PE for all aggregates, with stronger PE occurring in larger aggregates, especially in CT soil compared to NT soil. Larger aggregates have more unique microbial communities enriched in genes for simple C degradation (e.g., E5.1.3.6, E2.4.1.7, pmm-pgm, and KduD in Nitrosospeera and Burkholderia), contributing to the higher short-term PE; however, CT soils harbored more genes for complex C degradation (e.g., TSTA3, fcl, pmm-pgm, and K06871 in Gammaproteobacteria and Phycicoccus), supporting a stronger long-term PE. Temporally, soil aggregates played a significant role in the early-stage PEs (i.e., < 59 days after residue addition) through co-metabolism and nitrogen (N) mining, as evidenced by the increased microbial biomass C and dissolved organic C (DOC) and reduced inorganic N with increasing aggregate-size class. At a later stage, however, the legacy effect of tillage histories controlled the PEs via microbial stoichiometry decomposition, as suggested by the higher DOC-to-inorganic N and DOC-to-available P stoichiometries in CT than NT. Our study underscores the importance of incorporating both spatial and temporal microbial dynamics for a comprehensive understanding of the mechanisms underlying SOC priming, especially in the context of long-term contrasting tillage practices.

The business case for carbon farming in the USA.

U.S. agricultural producers are increasingly able to participate in private voluntary carbon initiatives that compensate their efforts to sequester CO2, reduce GHG emissions, and provide ecosystem services through eligible conservation practices. This study examines the potential effects of alternative private payment regimes (per practice vs. per output), prices paid to farmers relative to out-of-pocket costs (low vs. high), and the availability of information on CO2 sequestration (limited vs. full), on the adoption of cover crops and no-till in the United States, the resulting CO2 sequestration, and changes in farmers' net returns. The analysis relies on a highly stylized model of heterogeneous farms calibrated with county-level agronomic data, and simulated for current estimates of GHG impacts of cover crop planting and no-till under different scenarios. Our results indicate that agricultural carbon markets can be profitable for U.S. farmers, although with substantial geographic variability, and that annual carbon sequestration could range between 17 and 75 million mtCO2e. Payments per output would incentivize higher carbon sequestration than payments per practice, but the former regime would be less favored by farmers as a unified group than the latter (due to lower aggregate net returns). However, if operators of farms with high carbon sequestration potential could decide the payment regime to be implemented, they would choose the payment per output regime (due to higher net returns per enrolled hectare). Total projected net changes in GHGs under payments per practice, based solely on county-average net GHG effects of cover crops and no-till, over-estimate actual total GHG sequestration (based on the entire distribution of net effects by county) by 2.1 and 14.2 million mtCO2e, or 18% and 21%, respectively.

Cover Crop and Crop Rotation Effects on Tissue and Soil Population Dynamics of Macrophomina phaseolina and Yield Under No-Till System.

The effects of crop rotation and winter cover crops on soybean yield and colony-forming (CFU) units of Macrophomina phaseolina, the causal agent of charcoal rot (CR), are poorly understood. A field trial was conducted from 2011 to 2015 to evaluate (i) the impact of crop rotation consisting of soybean (Glycine max [L.] Merr.) following cotton (Gossypium hirsutum L.), soybean following corn (Zea mays L.), and soybean following soybean over a 2-year rotation and its interaction with cover crop and (ii) the impact of different cover crops on a continuous soybean crop over a 5-year period. This trial was conducted in a field with 10 subsequent years of cover crop and rotation treatments. Cover crops consisted of winter wheat (Triticum aestivum L.) and Austrian winter pea (Pisum sativum L. subsp. sativum var. arvense), hairy vetch (Vicia villosa Roth), and a fallow treatment was evaluated with and without poultry litter application (bio-cover). Tissue CFU of M. phaseolina varied significantly between crop rotation treatments: plots where soybean was grown following cotton had significantly greater tissue CFU than plots following soybean. Poultry litter and hairy vetch cover cropping caused increased tissue CFU, though this effect differed by year and crop rotation treatment. Soil CFU in 2015 was substantially lower compared with 2011. However, under some crop rotation sequences, plots in the fallow treatment had significantly greater soil CFU than plots where hairy vetch and wheat was grown as a cover crop. Yield was greater in 2015 compared with 2011. There was a significant interaction of the previous crop in the rotation with year, and greater yield was observed in plots planted following cotton in the rotation in 2015 but not in 2011. The result from the continuous soybean planted over 5 years showed that there were no significant overall effects of any of the cover crop treatments nor was there interaction between cover crop treatment and year on yield. The lack of significant interaction between crop rotation and cover crop and the absence of significant differences between cover crop treatments in continuous soybean planting suggest that cover crop recommendations for midsouthern soybean growers may need to be independent of crop rotation and be based on long-term crop needs.

Residual effects of composted sewage sludge on nitrogen cycling and plant metabolism in a no-till common bean-palisade grass-soybean rotation.

Introduction and aims: In the context of increasing population and decreasing soil fertility, food security is one of humanity's greatest challenges. Large amounts of waste, such as sewage sludge, are produced annually, with their final disposal causing environmental pollution and hazards to human health. Sludge has high amounts of nitrogen (N), and, when safely recycled by applying it into the soil as composted sewage sludge (CSS), its residual effect may provide gradual N release to crops. A field study was conducted in the Brazilian Cerrado. The aims were to investigate the residual effect of successive applications of CSS as a source of N in the common bean (Phaseolus vulgaris L. cv. BRS Estilo)-palisade grass (Urochloa brizantha (A.Rich.) R.D. Webster)-soybean (Glycine max L.) rotation under no-tillage. Additionally, N cycling was monitored through changes in N metabolism; the efficiency of biological N2 fixation (BNF) and its implications for plant nutrition, development, and productivity, was also assessed. Methods: The experiment consisted of a randomized complete block design comparing four CSS rates (10, 15, 20, and 25 Mg ha-1, wet basis) to a control treatment (without adding mineral or organic fertilizer) over two crop years. Multiple plant and soil analyses (plant development and crop yield, Falker chlorophyll index (FCI), enzymatic, biochemical, 15N natural abundance, was evaluated, root and shoot N accumulation, etc.) were evaluated. Results and discussion: Results showed that CSS: i) maintained adequate N levels for all crops, increasing their productivity; ii) promoted efficient BNF, due to the stability of ureide metabolism in plants and increased protein content; iii) increased the nitrate content and the nitrate reductase activity in soybean; iv) affected urease activity and ammonium content due to changes in the plant's urea metabolism; v) increased N accumulation in the aerial part of palisade grass. Composted sewage sludge can be used as an alternative source to meet crops' N requirements, promoting productivity gains and N cycling through forage and improving N metabolism.

Changes in the mycobiome structure in response to reduced nitrogen fertilization in two cropping systems of maize.

Nitrogen (N) is an essential element for plant productivity; hence, it is abundantly applied to the soil in the form of organic or chemical fertilizers, which consequently have a negative impact on the environment. Therefore, the main objective of our study was to investigate the structure and richness of the soil mycobiome in response to reduced nitrogen fertilization under two cropping systems: plowing (P) and no-till (NT). Moreover, the scope of the study perfectly falls into the EU "From Field to Table" strategy, which recommends a 20 % reduction of nitrogen fertilization of agricultural soils by 2030. In our study, the samples were collected twice during a single growing season: before maize sowing (without fertilization) and after harvesting the crop (four different fertilization rates). The mycobiome structure was identified based on the next generation sequencing (NGS) technique. Overall, our research has proved that the cropping system is important in terms of the formation of the fungal mycobiome structure and relative abundance. In addition, we confirmed that soil properties have a significant impact on fungal communities. We determined that a 20 % lower nitrogen fertilization rate (92.0 kg N ha-1) had a positive effect on the abundance of fungal communities. Moreover, the highest biodiversity at each of the taxonomic levels tested (phylum, class, genus) in the NT system and at the class and genus levels in the P system was also evidenced at the 20 % lower N fertilization rate. We also recommended potential indicators confirming the positive impact of reduced fertilization in two cropping systems: plowing - Epicoccum, Metarhizium, Mycosphaerella, and Paraconiothyrium and no-till - Peziza, Podospora, Metarhizium, Trechispora, and Umbelopsis.

Soil carbon sequestration in global working lands as a gateway for negative emission technologies.

The ongoing climate crisis merits an urgent need to devise management approaches and new technologies to reduce atmospheric greenhouse gas concentrations (GHG) in the near term. However, each year that GHG concentrations continue to rise, pressure mounts to develop and deploy atmospheric CO2 removal pathways as a complement to, and not replacement for, emissions reductions. Soil carbon sequestration (SCS) practices in working lands provide a low-tech and cost-effective means for removing CO2 from the atmosphere while also delivering co-benefits to people and ecosystems. Our model estimates suggest that, assuming additive effects, the technical potential of combined SCS practices can provide 30%-70% of the carbon removal required by the Paris Climate Agreement if applied to 25%-50% of the available global land area, respectively. Atmospheric CO2 drawdown via SCS has the potential to last decades to centuries, although more research is needed to determine the long-term viability at scale and the durability of the carbon stored. Regardless of these research needs, we argue that SCS can at least serve as a bridging technology, reducing atmospheric CO2 in the short term while energy and transportation systems adapt to a low-C economy. Soil C sequestration in working lands holds promise as a climate change mitigation tool, but the current rate of implementation remains too slow to make significant progress toward global emissions goals by 2050. Outreach and education, methodology development for C offset registries, improved access to materials and supplies, and improved research networks are needed to accelerate the rate of SCS practice implementation. Herein, we present an argument for the immediate adoption of SCS practices in working lands and recommendations for improved implementation.

Circular agriculture increases food production and can reduce N fertilizer use of commercial farms for tropical environments.

World food production must increase in the coming years with minimal environmental impact for food and nutrition security. Circular Agriculture has emerged as an approach to minimize non-renewable resource depletion and encourage by-product reuse. The goal of this study was to evaluate Circular Agriculture as a tool to increase food production and N recovery. The assessment was conducted for two Brazilian farms (Farm 1; Farm 2) with Oxisols under no-till and a diversified cropping system, including five species of grain, three cover crop species, and sweet potato. Both farms implemented an annual two-crop rotation and an integrated crop-livestock system with beef cattle confined for 2-years. Grain and forage from the fields, leftovers from silos, and crop residues were used as cattle feed. Grain yield was 4.8 and 4.5 t ha-1 for soybean, 12.5 and 12.1 t ha-1 for maize, and 2.6 and 2.4 t ha-1 for common bean, for Farm 1 and Farm 2, respectively, which is higher than the national average. The animals gained 1.2 kg day-1 of live weight. Farm 1 exported 246 kg ha-1 year-1 of N in grains, tubers, and animals, while 216 kg ha-1 year-1 was added as fertilizer and N to cattle. Farm 2 exported 224 kg ha-1 year-1 in grain and animals, while 215 kg ha-1 year-1 was added as fertilizer and N to cattle. Circular practices, i.e., no-till, crop rotation, year-round soil covered, maize intercropped with brachiaria ruziziensis, biological N fixation, and crop-livestock integration, increased crop yield and decreased N application by 14.7 % (Farm 1) and 4.3 % (Farm 2). 85 % of the N consumed by the confined animals was excreted and converted into organic compost. Overall, circular practices associated with adequate crop management allowed recovering high rate of applied N, reducing environmental impacts, and increasing food production with lower production costs.

Soil bacterial community dynamics in plots managed with cover crops and no-till farming in the Lower Mississippi Alluvial Valley, USA.

AIMS: Assess bacterial community changes over time in soybean (Glycine max) crop fields following cover crop (CC) and no-till (NT) implementation under natural abiotic stressors. METHOD AND RESULTS: Soil bacterial community composition was obtained by amplifying, sequencing, and analysing the V4 region of the 16S rRNA gene. Generalized linear mixed models were used to assess the effects of tillage, CC, and time on bacterial community response. The most abundant phyla present were Acidobacteria, Actinobacteria, Bacteroidetes, and Verrucomicrobia. Bacterial diversity increased in periods with abundant water. Reduced tillage (RT) increased overall bacterial diversity, but NT with a CC was not significantly different than RT treatments under drought conditions. CCs shifted abundances of Firmicutes and Bacteroidetes depending on abiotic conditions. CONCLUSIONS: In the Lower Mississippi Alluvial Valley (LMAV), USA, NT practices lower diversity and influence long-term community changes while cover crops enact a seasonal response to environmental conditions. NT and RT management affect soil bacterial communities differently than found in other regions of the country.

Soil physicochemical and biological properties in soybean areas under no-till Systems in the Brazilian Cerrado.

No-till (NT) as a conservation practice aims to minimize soil disturbance and enhance soil sustainability. However, how NT practice affects soil physicochemical and biological properties in soybean areas remains unclear. This study selected 65 high-yielding soybean farms under a long-term NT system in the Brazilian Cerrado and collected soil samples at 0.0-0.10 m (L1), 0.10-0.20 m (L2) and 0.20-0.40 m (L3) depths. The effect of NT on soil properties and interactions with soybean productivities were assessed. Results showed that the average soybean yield of the study areas in the last three years was 4.13 Mg ha-1, with 26 areas presenting yields over 4.20 Mg ha-1. Most studied soil properties showed a depth stratification and were strongly concentrated in L1, except for S, Al3+ and aluminum saturation, which displayed lower surface and higher subsurface concentrations. Moreover, a high proportion of SOM is composed of light SOM fraction in areas of high soybean yield, with the average SOM values of 39.9, 27.8 and 19.6 g kg-1 in L1, L2 and L3, respectively. Soils under long-term NT present moderate values of enzyme activity compared with the relatively low values under conventional tillage system, especially 94 % of the plots have moderate values of activity of arylsulfatase enzymes. The data presented support the conclusion that NT system can enhance soil fertility and biological quality in soybean cultivation. Our results suggest that it is necessary to adopt NT practice because it allows increasing soybean productivity in Brazil without the need to increase the sown area, in addition to increasing productivity associated with an improvement in the agroecosystem quality, thus moving toward a more sustainable agriculture.

The effect of resource-saving tillage technologies on the mobility, distribution and migration of trace elements in soil.

The influence of agricultural tillage technologies on the accumulation and distribution of trace elements in the soil is poorly studied. At the same time, intensive agriculture requires large amounts of fertilizers, growth stimulators, pesticides, and other substances, which can effect the ecological safety of the plant products and soil. This paper represents studying the effect of various agricultural techniques (including resource-saving technologies) on the mobility and profile distribution of Pb, Zn, and Cu in Haplic Chernozem. No significant influence of resource-saving tillage technologies was found on the total Pb content. Contrary, the resource-saving tillage technologies was observed to promote the growth of the total Zn and Cu content depending on the cultivation method (by 26% Zn, 34% Cu at minimal tillage, and 28% for both elements using No-till in Ap horizon). Amongst different applied agrotechnologies, there was no influence found on the profile distribution of total elements content. Only two horizons showed the total Pb content accumulation: biogenic (Ap-A) and carbonate (BC-C) horizon. In contrast, the only biogenic accumulation for Zn was determined. Copper characterizes by even distribution over the soil profile. The use of resource-saving agricultural technologies increases exchangeable fraction of Zn, Pb and Cu in soil almost by 1.5-2.0 times in the Ap horizon compared to moldboard ploughing. Despite the increase in the exchangeable fraction of Zn and Cu, this amount of micronutrients is not enough for adequate plant nutrition. The use of various agricultural technologies at Haplic Chernozem led to changes in the distribution of studied elements' exchangeable fraction over the soil profile. The study results suggested a need to increase the amount of Cu and Zn fertilizers applied to the soil with resource-saving cultivation technologies.

Dynamics and weed control effectiveness of dicamba herbicide when applied directly on the soil and corn straw in Brazil.

Dicamba is a post-emergence herbicide commonly used to control broadleaves in cereal crops. However, a portion of the herbicide might reach soil surface, and many factors could affect its dynamics and effects. The objective of this research was to evaluate the dynamics of dicamba applied to the soil, to the soil and covered with straw and over the straw, in addition, to evaluate the weed control in pre-emergence. Two field experiments at different locations were conducted with dicamba. To quantify dicamba in the soil a LC-MS/MS system was used. In both experiments, rainfall and straw played a key role in dicamba soil dynamics and weed control. Dicamba in the soil was affected by presence of straw and accumulated rainfall after the application. Higher concentrations (254-432 ng g soil-1) in the soil 0-10 cm layers and greater leaching potential were found for the application in the soil compared to over the straw. The maximum concentration of dicamba (101.6-226 ng g soil-1) was found after 10 mm of rainfall for dicamba application over the straw. Around 60-70% of weeds were controlled with concentrations greater than 20 ng/g soil-1, in the presence or absence of straw.

Restoring soil carbon in marginal land of Indian Himalayas: Impact of crop intensification and conservation tillage.

Soil carbon (C) loss is the prime sign of land degradation, and C pools have a great impact on soil quality and climate change mitigation. Hence, a field experiment was conducted for three consecutive years to assess the impact of crop intensification and conservation tillage practices on changes in the C pool at different soil depths of marginal land of the Indian Himalayas. The experiment consisted of two intensified cropping systems viz., CS1-Summer maize (Zea mays L.) -rainy season maize-lentil (Lens esculenta L.) and CS2-Summer maize-rainy season maize-mustard (Brassica juncea (L.) Czern) and five tillage practices viz., No-till (NT); NT + live mulch of cowpea (NT + LMC); reduced tillage (RT); RT + LMC and conventional tillage (CT). Results revealed that CS2 produced significantly higher biomass, C retention efficiency (9.85%), and sequestrated greater C (0.42 Mg ha-1 yr-1) in the soil system than CS1. Of the various tillage practices, RT + LMC registered higher biomass and recycled greater biomass and C than those under other tillage practices. However, the highest soil organic carbon (SOC) content (7.03 g kg-1) and pool (9.62 Mg ha-1) in 0-10 cm depth were observed under NT + LMC. The non-labile C pool size under NT in 0-10 cm and 10-20 cm depths was significantly greater than those under CT. The NT + LMC sequestrated significantly higher SOC (0.57 Mg ha-1 yr-1) than other tillage practices. Thus, the study indicated that the adoption of an intensified maize-based system under RT + LMC or NT + LMC would increase SOC storage and C sequestration in marginal lands of the Indian Himalayas.

Efecto de los cultivos de cobertura invernales sobre el microbioma del suelo: revisión sistemática de la literatura / Effect of winter cover crops on the soil microbiome: a systematic literature review

Resumen La inclusión de cultivos de cobertura invernales (CCI) en un sistema de siembra directa (SD) en reemplazo del barbecho constituye una alternativa promisoria para mejorar la salud del suelo y contribuir a la sustentabilidad ambiental de los sistemas agrícolas. Esta revisión ofrece un panorama integral de los efectos sobre el microbioma del suelo que tiene la introducción de CCI en rotación con cultivos de verano en sistemas de SD vs. el barbecho desnudo. Se realizó una búsqueda sistemática de la literatura que reporta los efectos de los CCI sobre los parámetros de abundancia, actividad y diversidad microbiana del suelo. Combinando 7 criterios de búsqueda se seleccionaron y analizaron 22 trabajos. El conjunto de resultados de esos trabajos muestra que la actividad enzimática del suelo se ve favorecida con la inclusión de CCI en la rotación, principalmente si estos se componen de leguminosas y mezclas de especies. Más de la mitad de esos trabajos reportan una mayor biomasa microbiana con CCI que con barbecho. Además, se advierte que los efectos de los CCI sobre los parámetros microbianos son independientes de la duración de los ensayos. Sin embargo, aún se necesitan más investigaciones básicas que permitan reducir la heterogeneidad entre estudios y comprender las complejas interacciones que ocurren entre los CCI y el microbioma del suelo.

Abstract The inclusion of winter cover crops (WCC) in no-till (NT) systems in replacement of bare fallow is a promising alternative to improve soil health and consequently, contribute to environmental sustainability of agricultural systems. This review provides a comprehensive evaluation of the effects of the use of WCC in rotation with summer cash crops under NT systems on the soil microbiome versus bare fallows. A systematic literature search was conducted to evaluate the impact of WCC on microbial parameters indicative of abundance, activity and diversity. Twenty-two papers were selected based on seven combined criteria. The results of this review show that enzyme activities in soil are enhanced with the inclusion of WCC in the rotation, particularly those that include legumes and mix of species. ln general, more than half of the analyzed papers report higher microbial biomass in soils with WCC than in bare fallow. Interestingly, the effects of WCC on microbial parameters are independent of the duration of the experiments. However, more basic research is necessary to reduce the heterogeneity of the studies and to better understand the complexity of the interactions between WCC and the soil microbiome.

Sieving soil before incubation experiments overestimates carbon mineralization but underestimates temperature sensitivity.

The sensitivity of soil organic carbon (SOC) mineralization to temperature could affect the future atmospheric CO2 levels under global warming. Sieved soils are widely used to assess SOC mineralization and its temperature sensitivity (Q10) via laboratory incubation. However, sieved soils cause a temporary increase in mineralization due to the destruction of soil structure, which can affect estimates of SOC mineralization, especially in soils managed with no-till (NT). To identify the effects of soil sieving on SOC mineralization and Q10, soil was collected from an 11-year field experiment under a wheat-maize cropping system managed with a combination of tillage [NT and plow tillage (PT)] and residue [residue returning (RR) and residue removal (R0)]. Soil was either sieved or left in an undisturbed state and incubated at 15 °C and 25 °C. SOC mineralization in sieved soils at 25 °C was 47.28 g C kg-1 SOC, 160.1% higher than SOC mineralization in undisturbed soils (P < 0.05). Interestingly, Q10 values in sieved soils were 1.29, 77.6% lower than Q10 in undisturbed soils (P < 0.05). Highly significant correlations (P < 0.01) were observed between sieved and undisturbed soils for SOC mineralization (r = 0.85-0.98) and Q10 (r = 0.78-0.87). Soil macro-aggregates had lower SOC mineralization by 6.1-21.9%, but higher Q10 values by 4.7-6.5% compared with micro-aggregates, contributing to lower mineralization and higher Q10 under NT and RR. Furthermore, structure equation and random forest modelling showed that increased SOC contents in NT and RR could not only reduce SOC mineralization, but also constrained the improvement of Q10 in NT and RR. Overall, these results indicated that although sieved soils overestimated SOC mineralization and underestimated Q10 due to the destruction of macro-aggregates, the patterns between treatments were similar and sieving soil for incubation is considered as a suitable approach to evaluate the relative impacts of NT and RR on SOC mineralization and Q10.

Responses of soil pH to no-till and the factors affecting it: A global meta-analysis.

No-till (NT) is a sustainable option because of its benefits in controlling erosion, saving labor, and mitigating climate change. However, a comprehensive assessment of soil pH response to NT is still lacking. Thus, a global meta-analysis was conducted to determine the effects of NT on soil pH and to identify the influential factors and possible consequences based on the analysis of 114 publications. When comparing tillage practices, the results indicated an overall significant decrease by 1.33 ± 0.28% in soil pH under NT than that under conventional tillage (p < .05). Soil texture, NT duration, mean annual temperature (MAT), and initial soil pH are the critical factors affecting soil pH under NT. Specifically, with significant variations among subgroups, when compared to conventional tillage, the soil under NT had lower relative changes in soil pH observed on clay loam soil (-2.44%), long-term implementation (-2.11% for more than 15 years), medium MAT (-1.87% in the range of 8-16℃), neutral soil pH (-2.28% for 6.5 < initial soil pH < 7.5), mean annual precipitation (-1.95% in the range of 600-1200 mm), in topsoil layers (-2.03% for 0-20 cm), with crop rotation (-1.98%), N fertilizer input (the same for NT and conventional tillage) of 100-200 kg N ha-1 (-1.83%), or crop residue retention (-1.52%). Changes in organic matter decomposition under undisturbed soil and with crop residue retention might lead to a higher concentration of H+ and lower of basic cations (i.e., calcium, magnesium, and potassium), which decrease the soil pH, and consequently, impact nutrient dynamics (i.e., soil phosphorus) in the surface layer under NT. Furthermore, soil acidification may be aggravated by NT within site-specific conditions and improper fertilizer and crop residue management and consequently leading to adverse effects on soil nutrient availability. Thus, there is a need to identify strategies to ameliorate soil acidification under NT to minimize the adverse consequences.

[Effect of winter cover crops on the soil microbiome: a systematic literature review]. / Efecto de los cultivos de cobertura invernales sobre el microbioma del suelo: revisión sistemática de la literatura.

The inclusion of winter cover crops (WCC) in no-till (NT) systems in replacement of bare fallow is a promising alternative to improve soil health and consequently, contribute to environmental sustainability of agricultural systems. This review provides a comprehensive evaluation of the effects of the use of WCC in rotation with summer cash crops under NT systems on the soil microbiome versus bare fallows. A systematic literature search was conducted to evaluate the impact of WCC on microbial parameters indicative of abundance, activity and diversity. Twenty-two papers were selected based on seven combined criteria. The results of this review show that enzyme activities in soil are enhanced with the inclusion of WCC in the rotation, particularly those that include legumes and mix of species. In general, more than half of the analyzed papers report higher microbial biomass in soils with WCC than in bare fallow. Interestingly, the effects of WCC on microbial parameters are independent of the duration of the experiments. However, more basic research is necessary to reduce the heterogeneity of the studies and to better understand the complexity of the interactions between WCC and the soil microbiome.

Herbicide Efficacy of Spot Spraying Systems in Fallow and Postharvest in the Pacific Northwest Dryland Wheat Production Region.

Real-time spot spraying technology has the potential to reduce herbicide costs and slow herbicide resistance. However, few studies exist on the efficacy of this technology in the Pacific Northwest (PNW). This research compared the herbicide efficacy (reduction in weed density and cover) of WEED-IT and WeedSeeker spot spraying systems to uniform spraying in fallow and postharvest in 2019 and 2020. Weed community types included naturally occurring weeds, natural + Russian thistle (Salsola tragus L.), or natural + kochia (Bassia scoparia (L.) A. J. Scott). Herbicides included glyphosate or the pre-mix bromoxynil + pyrasulfotole. Additionally, herbicide efficacy was studied with short stubble (~10 cm), tall stubble (~25 cm), and normal stubble (~20 cm) with chaff and straw removed. In fallow, herbicide efficacy was 1.5 times higher for uniform applications than for WEED-IT or WeedSeeker in 2019 and 2020. Herbicide efficacy was also 1.9 times higher for uniform applications in postharvest in 2019 but no differences were found in 2020. The weed community impacted herbicide efficacy but herbicide efficacy did not differ between residue management treatments. Finally, WEED-IT and WeedSeeker used 53% less herbicide volume in comparison to uniform applications. This research demonstrated that spot spraying technology can be efficacious and economical for growers in the PNW.