Levels Of Soil Disturbance Research Articles

Reducing initial cotton yield penalties in a transition to conservation agriculture through legume cover crop cultivation – evidence from Northern Benin

Much effort has been spent on promoting conservation agriculture (CA) in Northern Benin to sustain the transition of cotton (Gossypium hirsutum L.) cropping systems toward agroecology. However, its limited adoption by farmers is often ascribed to initial yield penalties during the transition to CA and to trade-offs around crop biomass use. Here, we assess the effect of different CA-based cropping systems promoted in the region on water productivity and cotton yield in a three-year cotton/maize (Zea mays L.) crop rotation during the initial transition phase to CA. Three CA options were assessed combining different levels of soil disturbance and cover, and introducing cover crops to alleviate the biomass trade-offs. Direct seeding (DS), strip tillage (ST), and direct seeding mulched-based cropping systems (DMC) were compared with conventional tillage (CT) from 2017 to 2019 under a dominant soil type in the region, Haplic Lixisols. Two legume species, Stylosanthes guianensis (Aubl.) Sw. and Crotalaria retusa L. were grown as cover crops with maize under ST and DMC. The experiment followed a randomized block design comprising six replicates. After 2–3 years of DMC, the cotton yield advantage with respect to CT increased from 5 % to 7 %. Cotton yield penalties of respectively 11 % in 2018 and 26 % in 2019 were found for DS. ST treatment went from a yield advantage of 8 % in 2017 to a yield penalty of 20 % in 2019. The DMC and CT treatments gave similar and highest boll weights compared to the ST and DS treatments. The treatments had no significant difference regarding the number of bolls per plant. Soil water storage in the upper 30 cm depth and water use efficiency (WUE) were the highest in the plots with the DMC treatment compared to CT, ST, and DS. At 28 days of active vegetative stage (between 34 and 62 days after sowing), the WUE of seed cotton was 0.11 kg ha−1 mm−1 under DMC, while it was 0.08, 0.07, and 0.04 kg ha−1 mm−1 under DS, CT, and ST, respectively. The performance of DMC at increasing water productivity could be an argument to improve adoptability by farmers in northern Benin who are facing increased weather variability, given that the yield penalties often associated with early transitions to CA were not observed here with full DMC.

Roman to early medieval cereal farming in the Rhineland: weeds, tillage, and the spread of the mouldboard plough

ABSTRACT A new model for gauging levels of soil disturbance (i.e. tillage) by analysing arable weed assemblages from archaeological contexts is applied to an extensive Roman-to-early medieval archaeobotanical sequence from the region west of Cologne. It tests the hypothesis that increasing use of the mouldboard plough, especially in a three-field system, would result in increased levels of soil disturbance which would be reflected in the kinds of weeds that grew in arable fields. The results point to clear differences in tillage regimes during the Roman period, providing support for the view that military sites were not provisioned by the same networks that supplied the civilian market. They also reveal generally low disturbance levels for the fifth and sixth centuries, indicating a continuing predominance of ard cultivation in the post-Roman period. The majority of seventh- to eighth-century samples had, however, been grown in ‘high disturbance’ conditions, a pattern that continued through the eighth and ninth centuries. Although use of the mouldboard plough within a fully developed three-field system may not have become widespread until the tenth or eleventh century, our evidence suggests that a plough capable of turning over the soil was in use in the Rhineland at a much earlier date.

Vineyard floor management intensity impacts soil health indicators and plant diversity across South Australian viticultural landscapes

Throughout the last thirty years, major shifts in vineyard floor management have been observed. Challenges initially posed by intensive tillage included high rates of soil erosion and the degeneration of soil structure and soil organic matter, which lead viticulturists to depend more heavily on herbicide use as an effective weed control strategy. However, an increase in herbicide persistence and toxicity in water, soils, and grapevines, increasing resistance of common weeds; and pressure from consumers and regulators to reduce their use is directing a shift towards an overall reduction in herbicide usage. This has led to more frequent tillage to manage vegetation in vineyards, while in some instances, cultural practices including slashing and animal grazing are used solely or in conjunction. However, little is known about the holistic effects of these varying practices on vineyard soils and biodiversity across landscapes in Australia. Thus, to comparatively assess the environmental impacts of different floor management practices, soil health indicators and plant dynamics were seasonally measured in the mid- and under-vine rows at twenty-four vineyard sites and four native sites in the Barossa Valley, Eden Valley, and McLaren Vale, all located in South Australia, where different intensities of floor management were implemented. Vineyard sites were categorised based on the frequency of herbicide and/or tillage passes particularly in the under-vine area into Low (no annual management passes), Medium (one annual management pass), and High (two to four annual management passes) intensity groups. Findings revealed similarities in the vineyard mid-rows across the management intensities, yet the under-vine rows displayed many differences; in particular, there were more plant species, higher plant coverage, and greater plant biomass in the Low management intensity group. Furthermore, as management intensity decreased, the relative richness of ruderal plant species also decreased, giving way to a plant community mainly comprised of slow-growing, perennial Poaceae and Fabaceae species in the Low-intensity management group. These differences in plant dynamics drove a suite of soil responses including faster water infiltration, higher soil ammonium-N and total nitrogen, and a tendency of higher soil gravimetric water content at the time of sampling. These results suggest that after an initial period of establishing these more extensive vineyard floor management practices, low levels of soil disturbance in the under-vine rows may contribute positively to improving natural ecosystem synergy and functionality between soil and plants. Therefore, our findings lend insights into how the varying intensity of floor management practices, rather than differing management ideologies per se, across a viticultural landscape can be intrinsic supporters of agroecosystem resilience under South Australian conditions.

Effects of Different Types of Soil Management on Organic Carbon and Nitrogen Contents and the Stability Index of a Durum Wheat–Faba Bean Rotation under a Mediterranean Climate

Soil quality, nitrogen, and organic matter content are increasingly being researched due to their impact on the environment. We assessed the effects of different soil management practices on the distribution and accumulation of soil organic carbon (SOC) in a durum wheat–faba bean rotation system cultivated in a Mediterranean-type area of Southern Italy, over six years. The effects of three levels of soil disturbance—conventional tillage (CT), minimum tillage (RT), and no tillage—(NT) on the SOC and nitrogen (N) content at soil depths of 0–15, 15–30, 30–60, and 60–90 cm were compared in a long-term experiment starting in the 2009–2010 growing season. The three soil management systems showed significant differences (p < 0.05) in the surface layer (0–15 cm depth) in SOC content and total nitrogen, with the largest accumulation occurring in the conservation system (NT). In the deep layers (30–60 and 60–90 cm), however, no significant differences were found between the three tillage systems. The ascending order of the tendency to accumulate SOC and N in the soil in the 0–15 cm layer was NT > CT > RT. In addition, the C/N ratio showed a more equilibrated rate in the NT system. The conservation tillage (NT) gave the best results in terms of the physical characteristics of the soil, showing a higher stability index compared to CT and RT. Conservation tillage is therefore recommended for wheat cultivation in the dry areas of Southern Italy, due to its benefits in terms of both crop yield improvements and environmental protection.

Grassland management intensification affects the soil fauna in a subtropical highland

AbstractThe conversion of natural grasslands to cultivated pastures can have a significant impact on the composition and structure of soil macro‐ and mesofauna groups, compromising the resilience of these organisms and the ecosystem services they provide. We studied the responses of these groups to increasing levels of soil disturbance across a gradient of four land management practices: Natural grassland (NG), Improved‐natural grassland (IG), Perennial‐cultivated pasture (PP), and Annual‐cultivated pasture (AP). The NG area had a higher abundance of macrofauna, greater dominance of certain groups, particularly Isoptera, and a lower abundance of mesofauna. On the other hand, the IG area had a higher abundance and diversity of macro‐ and mesofauna, with a lower dominance of specific groups. The PP area had a higher abundance of Coleoptera, Oligochaeta, and Hemiptera, whereas the AP area, despite soil disturbance, showed a higher abundance of mesofauna, particularly mites, Collembola, and Enchytraeidae, but lower diversity. Different grassland management practices have significantly altered the composition and structure of macro‐ and mesofauna groups, resulting in high dissimilarity between communities. We recommend IG as a more productive and sustainable alternative to the total replacement of natural vegetation (NG) with intensified converted pastures (PP and AP), as it maintains soil fauna diversity and ecosystem services.

Impacts of thinning activities on boreal peatland forests

Boreal peatland forests are an important source of timber. Recently, timber harvesting has been extended to warmer months, resulting in machinery traffic over unfrozen soils, and leading to higher levels of soil disturbance, such as deeper ruts. Despite this, our knowledge of the impact of soil disturbance on peat physical properties and soil biochemistry is still limited. To address this gap, I conducted a study to examine the effects of soil disturbance caused by harvesting machinery during thinning operations on the soil physical, chemical, and biological properties and vegetation of drained boreal peatland forests. To assess the rate of recovery, I sampled six sites that formed a chronosequence covering 15 years since thinning. The results showed that soil disturbance caused an increase in the bulk density and field capacity of peat, along with a decrease in total porosity. In the vegetation, moss biomass and root production were reduced, but sedge cover increased. Furthermore, recently disturbed areas exhibited greater soil CO2 production potential, as well as higher soil CO2 and CH4 concentrations compared to control areas. However, CO2 and CH4 emissions, microbial communities, and cellulose decomposition rate were not impacted. Although the rate of recovery varied, all studied properties impacted by disturbance were fully recovered within 15 years. As the water retention characteristic (WRC) describes soil structure and its alterations, it a useful for disturbance assessment. Thus, I propose how WRC can be predicted using artificial neural networks. Overall, the study demonstrated that while drained boreal peatlands are sensitive to disturbance, they are also resilient to mechanical soil disturbance caused by thinnings.

Spore Abundance and Morphology of Arbuscular Mycorrhizal Fungal under Conservation Agriculture

Soil is full of microbial diversity and microbes present in soil interact diversely with other living form present in soil e.g., soil microbes and plants. These interactions range from symbiosis to parasitic. Among these, the most predominating mutualistic symbiotic relation is mycorrhiza (associated with ∼80% of terrestrial plant species), formed between arbuscular mycorrhizal (AM) fungi and vascular plants. An experiment was conducted under three cropping system rice-maize-cowpea (RMCp), rice-wheat-green gram (RWGg) and rice-cauliflower-bororice cropping (RCfBr) to study influence of three different tillage intensities i.e., CT (conventional tillage), RT (reduced tillage), and ZT (zero tillage) with five different levels of fertilizer and residue application, R1 (0%Residue & 100%RDF), R2(100%Residue & 50%RDF), R3 (100%Residue & 75%RDF), R4 (50%Residue & 100%RDF), R5 (50%Residue & 75%RDF), on AMF spore load and diversity.The experimental design followed was split plot with tillage was main plot treatment and residue as sub plot treatment. Result showed that AMF spores and diversity are significantly influenced of degree of soil disturbance under different tillage practices and cropping system in practice, however residue application imparted non-significant influence on AMF spore load and diversity. A significant lower spore count was observed under CT as degree of soil disturbance is excessive high under CT compared to RT and ZT. With respect to spore diversity, round (shape), brown (color) and free spores were predominating spore type. In reference to spore shape abundance sequence was round>spherical> oval while for spore color it was brown>yellow>hyaline and >90 % spore was free while attached spores were <5%. In case of AMF spore count influence of cropping system was more prominent compared to other factors (i.e., tillage and residue). In RMCp and RWGg, significant increase inspore count was observed compared to RCfBr cropping system. On second year of experimentation, in RCfBr cropping system a significant decline in spore number was detected due to inclusion of cauliflower which act as non-host of AMF. Hence to attain benefits associated with AMF to arable crop we must reduce level of soil disturbance and avoid crucifer crops in cropping system.

Long-term conservation agriculture increases nitrogen use efficiency by crops, land equivalent ratio and soil carbon stock in a subtropical rice-based cropping system

Conservation Agriculture (CA) is still a relatively new approach for intensively cultivated (3 crops yr -1 ) rice-based cropping systems that produce high crop yield and amounts of residues annually. With the recent development of transplanting of rice into tilled strips on non-puddled soil, CA could become feasible for rice-based cropping patterns. However, the effect of increased retention of crop residues on crop response to nitrogen (N) fertilization rate in strip tilled systems with the transplanted rice and other crops grown in the annual rotation is yet to be determined. For nine years, we have examined the effects of soil disturbance levels - strip tillage (ST) and conventional tillage (CT), two residue retention levels –15% residue by height (low residue, LR) and 30% residue (high residue, HR) and five N rates (60%, 80%, 100%, 120%, and 140% of the recommended N fertilizer doses (RFD)) for a rice-wheat-mungbean cropping sequence. The 100% RFD was 75, 100 and 20 kg N ha -1 for rice, wheat, and mungbean, respectively. Rice yields were comparable between the two tillage systems for up to year-6, wheat for up to year-3 but mungbean yield markedly increased in ST from year-1; however, the land equivalent ratio increased from year-1, principally because of higher mungbean yield. Introduction of ST increased land equivalent ratio by 26% relative to CT, N use efficiency and partial factor productivity. Nitrogen fertilizer demand for maximum yield in ST was increased by about 10% for rice and 5% for mungbean but decreased by 5% for wheat. Although fertilizer N demand had increased in ST system due to higher yield than CT, the N requirement declined by50–90% when the same yield goal is considered for ST as for CT. The soil organic carbon stock (0–15 cm) after 8 years increased from 21.5 to 30.5 t ha -1 due to the effect of ST plus high crop residue retention. Annual gross margin increased by 57% in ST over CT practice and 26% in HR over LR retention. In conclusion, after 9 years practicing CA with increased residue retention under strip tillage, the crops had higher N use efficiency, grain yield, land equivalent ratio and annual gross margin in the rice-wheat-mungbean cropping system while the N fertilizer requirement increased minimally. • Strip tillage (ST) with residue retention increased crop profitability. • Adoption of ST practice increased N use efficiency. • The ST practice required about 10% more N but produced higher rice crop yield. • Strip tillage plus residue retention increased SOC stock by 9 t ha -1 over 8 years.

Unearthing Shifts in Microbial Communities Across a Soil Disturbance Gradient.

Permafrost, an important source of soil disturbance, is particularly vulnerable to climate change in Alaska where 85% of the land is underlained with discontinuous permafrost. Boreal forests, home to plants integral to subsistence diets of many Alaska Native communities, are not immune to the effects of climate change. Soil disturbance events, such as permafrost thaw, wildfires, and land use change can influence abiotic conditions, which can then affect active layer soil microbial communities. In a previous study, we found negative effects on boreal plants inoculated with microbes impacted by soil disturbance compared to plants inoculated with microbes from undisturbed soils. Here, we identify key shifts in microbial communities altered by soil disturbance using 16S rRNA gene sequencing and make connections between microbial community changes and previously observed plant growth. Additionally, we identify further community shifts in potential functional mechanisms using long read metagenomics. Across a soil disturbance gradient, microbial communities differ significantly based on the level of soil disturbance. Consistent with the earlier study, the family Acidobacteriaceae, which consists of known plant growth promoters, was abundant in undisturbed soil, but practically absent in most disturbed soil. In contrast, Comamonadaceae, a family with known agricultural pathogens, was overrepresented in most disturbed soil communities compared to undisturbed. Within our metagenomic data, we found that soil disturbance level is associated with differences in microbial community function, including mechanisms potentially involved in plant pathogenicity. These results indicate that a decrease in plant growth can be linked to changes in the microbial community and functional composition driven by soil disturbance and climate change. Together, these results build a genomic understanding of how shifting soil microbiomes may affect plant productivity and ecosystem health as the Arctic warms.

Variations of Soil Physico-Chemical and Biological Features after Logging Using Two Different Ground-Based Extraction Methods in a Beech High Forest—A Case Study

Considering that forests are crucial in the ecosystem of our planet and that forests provide timber products as well as several ecosystem services, it is evident that the application of sustainable forest operations (SFOs) is of substantial importance to achieve sustainable forest management (SFM). One of the most important issues to be evaluated when dealing with SFOs is limiting the disturbance and impacts related to logging. Harvesting activities can indeed alter the conditions of soil through compaction and litter removal which can also lead to modifications from the biological point of view, for example, diminishing the presence of soil microarthropods. While keeping these objectives in focus, the aim of the present study was to evaluate physico-chemical and biological impacts on forest soil in Mediterranean beech forests after forest logging with two different extraction systems, which are forestry-fitted farm tractors equipped with winch and forwarder. Specifically, authors aimed to investigate: (i) soil disturbance levels of ground-based extraction methods; (ii) soil disturbance levels of the applied forestry intervention; (iii) soil disturbance levels between winching-skidding and forwarding. Findings showed that the physical, chemical, and biological soil features were slightly disturbed by the forestry itself. In addition, forest operations and machine traffic showed clear soil disturbance, resulting in a substantial alteration of the characteristics. Between the two extraction techniques tested, winching caused less disturbance while forwarding had stronger impacts. However, it should be noted that these impact levels are found only on approximately 28% of the surface where operations were carried out. From the evidence gathered in this study, winching seems a less impactful extraction method in the studied context. On the other hand, to decrease the impact of forwarding, some technical adjustments such as bogie-tracks, as well as improved operator training, should be applied.

The impact of reduced tillage and distance to field margin on predator functional diversity

IntroductionAgricultural intensification results in biodiversity loss through land conversion and management practices which negatively impact arthropods. The abundance and diversity of ground-dwelling predators, e.g. ground beetles (Coleoptera: Carabidae) and spiders (Araneae), are negatively affected by soil disturbances such as tillage. Reducing soil disturbances can potentially conserve arthropod populations in the field and reduce the use of chemical pest controls. The present study investigated the ground-dwelling predatory community using pitfall traps in cereal fields with three different levels of soil disturbance: conventional tillage, reduced tillage and no tillage under Conservation Agriculture management, in 2018 and 2019. Pitfall traps were placed in transects from the field margins. Overall, the activity-density of ground-dwelling predators was higher in fields with minimum soil disturbance and generally declined with increased distance to semi-natural habitats. Functional diversity, expressed by the body size of ground beetles, was also affected by soil disturbances; large ground beetles more consistently occurred in CA, while few or none of the largest ground beetles were found in RT and CT. A higher sample-heterogeneity in less disturbed fields was indicated by a more variable median and higher skewness in the number of predators in those fields. In 2019 only, species diversity was higher along field edges bordering semi-natural habitats when compared to the cropped area. Our results show that reduced tillage supports predator arthropod communities at a local scale: It also bolsters agro-ecosystem resilience by promoting a higher activity-density and by increasing the heterogeneity and functional diversity of ground-dwelling predators.Implications for insect conservationThe results obtained in the present study show that soil disturbances significantly influence arthropod abundance and diversity. Conservation of epigeic natural enemies in the agricultural landscape is improved by reducing soil-disturbing events such as tillage.

Cover crops improve some, but not all, soil health indicators in horticultural rotations

Production of fruits and vegetables provides nutrient dense and high value crops. However, horticulture production is often very intensive and degrading to soil, with high levels of soil disturbance, high use of fertilizer inputs, and with prolonged periods of exposed soil. This can lead to increased soil degradation when compared to other types of cropping. We used a subset of the Atlantic Soil Health Laboratory’s database of on-farm soil samples collected between 2016 and 2018 to assess the impact of cover crop (CC) use in horticulture production in Nova Scotia on soil health. We analyzed 21 soil health parameters on soil collected from 14 fields, seven of which incorporated CCs in their crop rotation and seven of which used no CCs. The inclusion of CCs significantly increased permanganate oxidizable carbon (POX), soil respiration, autoclaved-citrate extractable (ACE) protein, residual soil nitrogen (N), and biologically available N. However, we also found that the variation in these parameters was greater when CCs were part of the rotation. This is likely attributable to the wide range of CC species used and differences in their management, such as the chosen termination method. While cover cropping is seen as a best management practice to improve soil health, simply using a CC in a horticulture rotation does not necessarily lead to improved soil health. Research trials on specific CC species and management to target soil degradation are needed to tailor recommendations to ensure the desired soil health outcomes can be achieved with CC use.

Solid-phase microextraction (SPME) for determination of geosmin and 2-methylisoborneol in volatile emissions from soil disturbance

A method is described here for the concentration and determination of geosmin and 2-methylisoborneol (2-MIB) from the gaseous phase, with translation to field collection and quantification from soil disturbances in situ. The method is based on the use of solid-phase microextraction (SPME) fibers for adsorption of volatile chemicals from the vapor phase, followed by desorption into a gas chromatograph-mass spectrometer (GC-MS) for analysis. The use of a SPME fiber allows simple introduction to the GC-MS without further sample preparation. Several fiber sorbent types were studied and the 50/30 μm DVB/CAR/PDMS was the best performer to maximize the detected peak areas of both analytes combined. Factors such as extraction temperature and time along with desorption temperature and time were explored with respect to analyte recovery. An extraction temperature of 30 °C for 10 min, with a desorption temperature of 230 °C for 4 min was best for the simultaneous analysis of both geosmin and 2-MIB without complete loss of either one. The developed method was used successfully to measure geosmin and 2-MIB emission from just above disturbed and undisturbed soils, indicating that this method detects both compounds readily from atmospheric samples. Both geosmin and 2-MIB were present as background concentrations in the open air, while disturbed soils emitted much higher concentrations of both compounds. Surprisingly, 2-MIB was always detected at higher concentrations than geosmin, indicating that a focus on its detection may be more useful for soil emission monitoring and more sensitive to low levels of soil disturbance.

Temporal fluctuations of microbial communities within the crop growing season

Soil microbial communities maintain many ecosystem functions including decomposition and symbiotic nutrient uptake. Prior field studies have focused on either geospatial or relatively large-time scale trends in these communities. Whereas, their small-time scale (e.g., weekly) dynamics in agricultural fields have largely been overlooked. Our objective was to determine the effects and characteristics of short-time scales on five phospholipid fatty acid (PLFA) microbial groups throughout the whole growing season, while under two soil disturbance levels. The microbial community groups included total microbial abundance (TMA), arbuscular mycorrhizal fungi (AMF), total fungi, actinomycetes, and total bacteria. The fungal to bacterial ratio (F:B) was also determined. Soils were sampled twice per week from planting to harvest during two consecutive growing seasons (N = 62) and analyzed for microbial abundances and chemical and physical properties. The study was conducted at an on-farm site with a corn [Zea mays] – soybean [Glycine max] – wheat [Triticum aestivum] rotation and two soil disturbance levels [high (chisel plow) and low (shallow vertical till)] using a randomized complete block design. Data analysis included 1) spatial and temporal coefficients of variations, 2) a mixed linear model to test for time and disturbance level effects, and 3) a Fourier analysis to detect and characterize cyclical patterns via autocorrelation spectral densities. The Fourier analysis also included cross spectral densities and phase lags with a large suite of soil chemical, soil physical, and weather states. Temporal variations of microbial communities were one to threefold greater than their spatial variations. Significant time effects were observed for TMA, AMF, and bacteria, where these communities behaved as sine and consine functions over time. However, strong cyclical patterns were above white noise levels at the experimental plots level for all microbial groups during each growing season. Cross spectral densities indicated that bacteria and actinomycetes tended to cycle at short and long periods (biweekly to whole season) associated with soil physical and weather states, whereas TMA, AMF, fungi, and F:B cycles at long periods (bimonthly to whole season) associated with soil chemical states. These microbial communities in a field setting clearly undergo cyclical patterns over small periods with some modulations from soil disturbance levels, fertilization, and microtopography. Further research on these cyclical and cross-correlated dynamics is warranted to determine the magnitude of influence on ecosystem services and crop productivity.

Soil disturbance levels, soil water content and the establishment of rainfed chickpea: Mechanised seeding options for smallholder farms in north‐west Bangladesh

AbstractOptimum soil physical conditions for crop establishment are more likely to occur with mechanised row‐sowing using metered seeding and controlled depth placement of seeds than with broadcast sowing, that is common in many traditional South Asian cropping practices. Establishment success is a limitation for post‐rice crops in medium to heavy textured soils in the Eastern Gangetic Plain because sowing coincides with rapid topsoil drying and increases in soil strength. In addition, due to lack of rainfall in the post‐rice season the crop relies on access to stored soil water during vegetative and reproductive growth to achieve adequate yields. Our aim was to determine whether decreased soil disturbance (from full tillage to zero tillage (ZT) to undisturbed soil (Fallow)) and direct seeding (using small‐scale seeders) could 1) enhance chickpea crop establishment by conserving seedbed soil water and 2) alter crop water use of the water stored in the soil profile. The silt loam soil has an estimated volumetric soil water content (θv) of 34% at field capacity. At sowing, θv in the seedbed was between 25% to 29%. This was adequate for successful chickpea crop establishment, but slightly wetter than optimum for tillage. In the wet soil at sowing, there was evidence of smeared furrow walls and poor soil covering of the seed in the seedbed in strip planting (SP; rotating blades in front of tine) and ZT. Uncovered furrows (in ZT; using a tine opener) and the fallow soil lost more surface soil water (9%, 23 days after sowing) than the seedbeds created with greater levels of soil disturbance. In 2008, grain yield of single‐pass shallow tillage (SPST) was greater than SP but in 2009, grain yields of all one‐pass tillage techniques (ZT, SP, SPST) were greater than in the broadcast seeding in fully tilled soils. The improvement in chickpea yields was attributed to greater plant numbers, early plant vigour and root growth. Chickpea roots were found to 60 cm depth in the soil profile, and soil water content was less than the θv of wilting point to this depth at podding. There is evidence that root growth and plant water uptake occur deeper in these soil profiles to achieve the grain yields > 1,000 kg/ha recorded in this study. Mechanised sowing in rows with small‐scale seeders has the capability to overcome establishment and yield limitations for chickpea on medium to heavy soils in the post‐rice season.

Reduced tillage with residue retention and nitrogen application rate increase N2O fluxes from irrigated wheat in a subtropical floodplain soil

Nitrous oxide (N2O) emissions were measured in irrigated wheat (Triticum aestivum) in an annual wheat- mungbean (Vigna radiata)-rice (Oryza sativa L) rotation that had been running for seven consecutive years. Effect of two soil disturbance levels (strip vs. conventional tillage; ST vs. CT both with 30 % residue retention) and three nitrogen (N) fertilizer rates (60, 100 and 140 % of the recommended N fertilizer dose, RD; called hereafter 60RD, 100RD and 140RD, respectively) were assessed. Mean N2O fluxes were about 110 % higher in ST than in CT. The rate of N fertilizer application influenced the mean and cumulative N2O fluxes with significantly higher fluxes in ST than in CT. Based on the respective maximum grain yields (CT: 140RD, 3.52 t ha−1; ST: 60RD, 3.19 t ha−1) yield-scaled N2O emissions were higher in ST than those in CT. However, tillage vs. N rate interactions showed both the highest and lowest yield-scaled N2O fluxes in ST with 140RD and 60RD, respectively. Soil microbial biomass carbon (MBC), organic carbon (SOC), total N (TN), nitrate (NO3- -N), aggregate mean weight diameter (MWD) and larger aggregate size classes (2.0‒0.85 and >2.0 mm) were significantly higher in ST and positively correlated with N2O fluxes. Our results highlight that, despite increased N2O emissions, ST with residue can trade-off emissions to improve soil macro aggregation, C sequestration and retention of N and crop yield with the lower N fertilizer and other energy inputs. Reduction of the recommended N fertilization rate could be considered if ST is adopted.

The interactive effects of soil disturbance and residue quality on soil nitrogen mineralisation in a tropical sandy soil

Soil conservation practices, such as reduced and no tillage, have been found to enhance soil nitrogen (N) sequestration through decreasing the rate of N mineralisation of added organic materials. Nitrogen mineralisation is not only affected by tillage, but also by the quality (chemical composition) of the organic residues. This study evaluated the interaction of residue quality and soil disturbance on N mineralisation in a sandy soil. A 112-day incubation experiment was conducted with two levels of soil disturbance (undisturbed and disturbed conditions) and five plant residue amendments of contrasting quality. The contrasting quality (N, lignin (L), and polyphenols (Pp)) (in g kg–1) amendments follow: (i) unamended; (ii) Sesbania grandiflora (N 44, L 173, Pp 9.2); (iii) Indigofera hirsuta (N 41, L 177, Pp 30); (iv) Dipterocarpus tuberculatus (N 8.2, L 203, Pp 71); and (v) Eucalyptus camaldulensis (N 9.7, L 126, Pp 110). Residues (ii) and (iii) were fresh legume leaves, while (iv) and (v) were non-legume leaf litter. Disturbance only significantly increased N mineralisation rates in the legume-residue treated soils (increases of 18.8% for S. grandiflora and 27.1% for I. hirsuta) during the early stage of decomposition (first 14 days). In the legume treatment, disturbance significantly increased the ammonification, but decreased nitrification in soil relative to undisturbed soils. The difference in patterns of ammonification and nitrification was more pronounced in the early than in the later period of decomposition. This indicated an inhibitory effect of soil disturbance on nitrification, which was particularly pronounced in the legume-treated soils. The Pp content of residues was the major quality parameter regulating the soil ammonium-N and nitrate-N concentrations. Minimum soil disturbance should be adopted under legume soil organic amendment so that both ammonification and nitrification components of N mineralisation process can occur normally, and nitrate-loving crops can take up N in the form of nitrate-N which will enhance their yields. Moreover, undisturbed conditions under legume organic amendments reduced N mineralisation, resulting in enhancing soil N sequestration.

The synchrony of cover crop decomposition, enzyme activity, and nitrogen availability in a corn agroecosystem in the Midwest United States

Cover cropping is commonly associated with increased soil microbial activity and soil health. Cover cropping in the Upper Mississippi River Basin has increased rapidly in the last decade due to the demonstrated ability that cover crops can increase soil health and decrease nitrate losses in tile-drained fields. One reason cover cropping is not adopted in the Midwest United States is the lack of knowledge on the synchrony of cover crop residue nitrogen (N) release and corn N demand. Therefore, the overarching goal of this research was to investigate soil enzyme activity and inorganic N availability during the decomposition period of common winter cover crops. Objectives were: i) to determine if soil enzyme activity (β-glucosidase and urease) is influenced by different cover crops (cereal rye (CR), hairy vetch (HV), and HV/CR mixture) and tillage systems (reduced tillage and no-tillage residue management) during the residue decomposition period, and ii) to determine the relationship between soil enzyme activity, inorganic N availability, and critical corn growth stages during cover crop decomposition. Cover crops in this study were selected due to contrast in residue carbon (C):N ratios, their commonality among regional farmers, and their differences in physiology. Spring tillage and no-tillage were investigated because of the differing levels of soil disturbance and residue incorporation. Enzyme activities were quantified at seven sampling dates following cover crop termination from April-October during the 2016 and 2017 corn growing seasons. Results revealed significant effects of sampling date (p < 0.001) and cover crop treatment (p < 0.05) on soil β-glucosidase activity and significant interaction effects between sampling date and cover crop treatment (p < 0.05) on potential soil urease activity. Tillage had a significant impact on soil β-glucosidase (p < 0.001) and urease (p < 0.05) activities in 2017, with higher activity observed in the no-tillage soil. These findings indicate that enzyme activity fluxes can be observed in agroecosystems one year after introducing conservation practices, such as cover crops and no-tillage. Greater than 50 % of C release from cover crop residue occurred from corn emergence to tasseling, and significantly greater β-glucosidase activity for CR-based treatments during corn peak N demand did not result in more soil inorganic N. This indicates a loss of plant-available N from the agroecosystem, which could be attributed to N immobilization by the soil microbial community. This study demonstrates a need to develop adaptive N fertilization management for corn that can overcome the potential impact of N immobilization during peak corn N demand following CR.

Variation in the yield of sunflower (Helianthus annuus L.) due to differing tillage systems is associated with variation in solute potential of the soil solution in a salt-affected coastal region of the Ganges Delta

Intensification of crop production in the coastal zones of the mega-deltas of Asia by dry season cropping requires timely crop establishment to mitigate the adverse effects of waterlogging, drought, salinity and poor soil structure. In the salt-affected coastal zone of the Ganges Delta, the best method of mechanized cultivation for the timely establishment of non-rice dry season crops on poorly structured, wet clay soils is unknown. Two field experiments were conducted to evaluate the effects of tillage systems with different levels of soil disturbance on the establishment, growth and yield of sunflower, and on soil physical and chemical properties. In 2016-17, five tillage treatments were tested: zero tillage (ZT), narrow strip tillage (NST), bed planting (BP), single pass shallow tillage (SPST) and double pass shallow tillage (DP); in 2017-18, four tillage types were tested: NST, wide strip tillage (WST), BP and SPST. Intensive soil disturbance (BP, DP and SPST) maintained higher soil water content in the surface soil (0–15 cm depth) than less disturbance (ZT, NST and WST) in both years. Tillage treatments had no effect on soil salinity (EC1:5) in 2016-17, but in 2017-18 BP significantly reduced the soil salinity relative to NST throughout the season. Highest yields (19 % and 10 % improvements in 2016-17 and 2017-18 respectively) were associated with tillage treatments with greatest soil disturbance, the BP and DP treatments in 2016-17, and the SPST treatment in 2017-18. These effects were mostly due to increases in soil water content and solute potential in surface soil layers. We conclude that for a wet-clay soil, heavy soil disturbance, such as with BP has the potential to increase the yield of sunflower by increasing soil water supply, decreasing soil salinity and maintaining a higher solute potential in the upper soil layers.

Effects of different long-term tillage systems on the composition of organic matter by 13C CP/TOSS NMR in physical fractions in the Loess Plateau of China

The adoption of conservation tillage is promising for soil management system in the Loess Plateau of China; however, how conservation tillage influences the molecular structure contributes and long-term stabilization of soil organic matter (SOM) is still not clear in this area. In this study, experimental plots were continually cultivated with winter wheat (Triticum aestivum L.) and soil samples were collected in September 2009 and September 2015, 10 and 16 years after the experiment was initiated, respectively. Four treatments were applied: reduced tillage (RT), no tillage (NT), sub-soiling (SS) and conventional tillage (CT). Soil samples were physically fractionated into five fractions: free light fraction (FLF), occluded light fraction (OLF), coarse sand particulate organic matter (c-POM), fine sand particulate organic matter (f-POM) and mineral associated organic matter + silt + clay (m-SOM). The soil organic carbon (SOC) stocks were analysed in SOM fractions and bulk soil (BS). Solid state 13C cross polarization/total sideband suppression nuclear magnetic resonance (13C CP/TOSS NMR) spectroscopy was applied to determine the abundance of different forms of carbon (C) (carboxyl C, O/N-alkyl C, aromatic C and alkyl C) in the soil physical fractions.The SOC stocks in the 0–30 cm layer were influenced by the tillage systems. Although there were no significant differences in SOC stocks among these four treatments in the 0–10 and 10–20 cm layers in first 10 years, after 16 years, the SOC stocks were highest in the SS and NT treatments in the 0–10 cm layer. As the duration of the experiment increased from 2009 to 2015, the SOC content of m-SOM-C fraction under RT and CT also increased. As determined by 13C NMR, in the light fractions (FLF to OLF), the abundance of aromatic C increased when the abundance of O/N-alkyl C declined and there was a higher aromatic C/O/N-alkyl C ratio. A gradual increase in the abundance of alkyl C of heavy fractions was accompanied by a decrease in aromatic C, which might be due to the microbial by-products deposited on mineral surface in the soils. In addition, a higher SOM preservation were shown in conservation tillage (NT and SS) by our NMR data. Particular interesting were the results of the light and c-POM fractions, in which conservation tillage showed a higher abundance of O/N-alkyl C and a lower aromatic C/O/N-alkyl C ratio in these two fractions compared with conventional tillage (RT and CT).However, these changes were not evident in the heavy fractions. The changes in the chemical structures of the light and c-POM fractions were possibly due to the retention of crop residues and low levels of soil disturbance. In conclusion, long-term conservation tillage affected the fractions and the chemical functional groups of SOM and could be ideal to preserve SOC in the Loess Plateau.