Plow Tillage Research Articles

Effects of crop residue managements and tillage practices on variations of soil penetration resistance in sloping farmland of Mollisols

Soil penetration resistance (SPR) is one of the major indicators of soil physical properties. Crop residue managements, tillage practices and their interactions exert significant effects on the SPR. However, rare information is available in the sloping farmland of Mollisols. Field experiments were conducted to investigate the variations of the SPR as affected by crop residue managements and tillage practices on the sloping land in Northeast China from 2015 to 2019. The split-plot experiment was arranged with two crop residue managements (removed, REM and retained, RET), and three tillage practices (no tillage, NT; rotary tillage, RT; plow tillage, PT). SPR data in 0-80 cm soil depth was measured at the end of harvest of maize monoculture. Results showed that the two crop residue managements induced significant variations in the SPR at 0-15 cm, 15-30 cm and 0-80 cm soil depths under NT, RT, and PT treatments, respectively. In comparison with RET treatment, the average values of the SPR under REM treatment were 10.9% and 8.9% higher in 45-60 cm and 60-80 cm soil depths, respectively. The average values of the SPR under PT treatment were 12.4% and 14.1% lower in 0-15 cm soil depth, and 23.9% and 10.4% lower in 15-30 cm soil depth than those under NT and RT treatments. However, the average value of the SPR under PT treatment was 11.2% and 22.0% higher in 60-80 cm soil depth than those under NT and RT treatments, respectively. The SPR generally decreased with the slope position declined in the deeper soil depth (except for the NT+RET treatment). The findings from this research can provide a scientific reference for the establishment of rational cultivation and the sustainable development of productivity on the sloping land of Mollisols in cold regions. Keywords: soil penetration resistance, crop residue management, tillage practice, slope position, soil depth, Mollisols DOI: 10.25165/j.ijabe.20221501.6526 Citation: Wang Y J, Qiao J Y, Ji W Y, Sun J, Huo D X, Liu Y P, et al. Effects of crop residue managements and tillage practices on variations of soil penetration resistance in sloping farmland of Mollisols. Int J Agric & Biol Eng, 2022; 15(1): 164–171.

EFFECTS OF DIFFERENT TILLAGE PRACTICES ON SOIL FERTILITY PROPERTIES: A REVIEW

Soil tillage is an important factor affecting soil fertility properties and crop yield. Tillage impact certain soil physical and chemical properties such as bulk density, soil porosity and water-holding capacity, infiltration rates, hydraulic conductivity, soil temperature, soil organic carbon, pH, CEC, available nitrogen, phosphorus and exchangeable potassium amongst others. The main objective of the present work was to compare the effect of no-tillage systems and the conventional tillage systems. Tillage systems can be generally categorized into plow tillage (conventional tillage), reduced tillage using chisel plow, disc plow, harrow disc or cultivators and no-till systems. Conservation tillage and its various types generally improve the soil quality indicators including soil organic carbon (SOC) storage. Whereas, conventional tillage practices give birth to a finer and loose-setting soil structure with a modified soil bulk density and soil moisture content, hence, causing loss of soil organic carbon and deterioration in other soil properties. Generally, soil fertility properties are more favourable with no-till than tillage-based systems. However, some researchers observed no significant effect of tillage methods (no-tillage and plow till) on bulk density (BD), pH and total porosity, while others found otherwise. The magnitude of these discrepancies could be due to the differences in crop species, soil properties, climatic characteristics and their complex interactions as well as tillage system adopted.

Plough Tillage Maintains High Rice Yield and Lower Greenhouse Gas Emissions Under Crop Straw Incorporation

Plough Tillage Maintains High Rice Yield and Lower Greenhouse Gas Emissions Under Crop Straw Incorporation

Immediate and long-term effects of tillage practices with crop residue on soil water and organic carbon storage changes under a wheat-maize cropping system

Reasonable tillage management benefits soil structure optimization and agricultural sustainability. However, the differences of immediate (i.e. changes between post- and pre- tillage) and long-term effects (i.e. changes between treatments after certain years) under different tillage practices is often neglected. This study involved a 16-year field experiment including three tillage practices (plow tillage, PT; subsoiling tillage, ST and rotary tillage, RT) and two crop residue management practices (no residue return and all residue return). Those immediate and long-term effects on soil physical properties and soil organic carbon were investigated. For the immediate effects after tillage, the soil water storage under PT, ST, and RT decreased by 5.8%, 4.0%, and 3.2%, respectively; while those under residue return and no residue return decreased by 3.9% and 4.6%, respectively. Under the same conditions, ST was more beneficial to reduce soil penetration resistance. The soil bulk density post-tillage was significantly lower than that pre-tillage at 0–10 cm soil depth, meanwhile the soil bulk density at 10–40 cm soil depth was generally decreased after tillage practice under ST treatment. For the long-term effects, the penetration resistance at 10–50 cm soil depth and the soil bulk density at 10–30 cm soil depth were lower under the ST treatment than those under PT and RT treatments. Additionally, residue return was beneficial for soil water storage, soil bulk density, and soil organic carbon storage. Overall, both for the immediate and long-term effects, subsoiling tillage with residue return significantly increased soil water storage, total porosity, soil organic carbon storage and crop yields, while decreased soil bulk density and penetration resistance.

Influence of basic tillage, fertilizers and herbicides on weediness of pea crops for grain in stationary crop rotation

Goal. To establish the influence of the methods of basic tillage, fertilization system and herbicides on the weediness of pea crops for grain during cultivation in a stationary steam-grain-row crop rotation of the eastern part of the Forest-Steppe of Ukraine.
 Methods. The research was carried out by route surveys of pea crops for grain in the field crop rotation.
 Results. According to the research of 2016—18, 52 types of weeds and contaminants (spring early and late were 54%; wintering, winter and biennials were 23%; perennials were 23%) were found in pea crops for grain after spring cereal crops (spring barley, spring wheat, spring triticale) as forecrop. The largest number of them was noted on the organic-mineral background (manure aftereffect, 30 t/ha + N30P30K30) for the application of fertilizers for plowing (33 species) and chisel tillage (35 species). The weeds found in the pea crops for grain belonged to 20 families, of which the aster family (17 species) was the most represented. The main weeds in the crops were Setaria glauсa (L.) Beauv., Echinochloa crus-galli (L.) Roem. et Schult., Chenopodium album L., Amaranthus retroflexus L., Solanum nigrum L., Ambrosia artemisiifolia L., Stachys annua L., Xanthium strumarium L., Galium aparine L., Viola arvensis Murr., Cirsium arvense (L.) Scop., Sonchus arvensis L. and Convolvulus arvensis L. The use of herbicides and their compositions in the cultivation of peas for grain has significantly influenced the dominance and subdominance of certain weed species in the years of research. The fertilization system and the methods of basic tillage in crop rotation had a significant impact on the type and level of weediness of crops. The type of weed control crops (without fertilizers) differed significantly from organic and organo-mineral fertilizer backgrounds. For the most part, the version with chisel tillage had a higher level of weeding compared to plowing.
 Conclusions. Methods of basic tillage, fertilizer system and herbicides significantly affect the weediness of pea crops for grain in steam-grain-row crop rotation, which should be taken into account by farmers when developing methods of its control in the eastern part of the Forest-Steppe of Ukraine.

Influence of tillage and fertilizer systems on productive moisture reserves under agrophytocenosis in crop rotation

The paper reveals the results of research on the impact of tillage and fertilizer systems using by-products on moisture reserves in the soil and crop yields in a four-course short-term crop rotation (winter rape – winter wheat – corn for grain – spring barley) on dark gray podzolized soil on the stationary experimental plot of the Institute of Agriculture of Western Polissia NAAS of Ukraine in 2016–2020. Three variants of tillage systems were studied: 1) 20– 22 cm depth moldboard ploughing – control; 2) 10–12 cm depth shallow ploughing; 3) 6–8 cm depth surface ploughing. The system of fertilization involved application of mineral fertilizers N128P90K120 kg/ha of crop rotation area, including the following options for straw: 1) without straw; 2) straw + destructor + N10 kg (ammonium nitrate) per 1 ton of precrop straw; 3) straw + N10 (ammonium nitrate) per 1 ton of pre-crop straw. It has been found out that the reserves of productive moisture in the meter layer of soil on average over the years of research within the period of germination and harvesting (corn, spring barley, winter wheat) in non-moldboard cultivation systems increased by 177.8, 147.1, 99.4 and 74.7, 65.9, 85.4 mm respectively compared with the moldboard ploughing system where moisture reserves were 150.8, 132.8, 73.5 and 55.5, 48.6, 52.6 mm. Under the system of fertilization which provided for the application of straw + N10 and straw + destructor + N10 kg, the reserves of productive moisture in the meter layer were 3.6 and 9.0 mm in the germination period and 10.2 and 14.4 mm in the harvesting period bigger than in the experiment without using straw. The 20–22 cm moldboard ploughing and the 10–12 cm shallow ploughing tillage systems provided higher crop yields compared to the 6–8 cm surface tillage system, which made it possible to obtain 6.91 and 6.50 of winter wheat yields, respectively, 5.37 and 5.13 of spring barley, 11.47 and 11.74 of corn and 3.08 and 3.19 t/ha of winter rape. Resulting from the application of surface tillage system by depth of 6–8 cm, the yield of winter wheat decreased by 1.45, that of spring barley by 1.69, corn by 3.66 and winter rape by 0.31 t/ha. Fertilizer systems based on the use of straw and straw + destructor provided an increase in grain yield respectively: winter wheat by 0.45–0.36 t/ha; corn by 0.60–0.46 t/ha; spring barley by 0.32–0.22 t/ha compared to the option without straw. Key words: productive moisture, crop, straw, tillage, crop rotation, yield.

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.

Determination of the effects of tillage on the productivity of a sandy loam soil using soil productivity models

Based on the hypothesis that soil properties and productivity components should be affected by different tillage methods, field and laboratory experiments were conducted to study the effects of zero tillage (ZT), one pass of disc plough tillage (P), one pass of disc plough plus one pass of disc harrow tillage (PH) and one pass of disc plough plus two passes of disc harrow tillage (PHH) on the distribution of the bulk density, available water capacity, pH, organic matter, available phosphorus, iron oxide and aluminium oxide at different soil depths, and their effects on the soil productivity. The available water capacity, pH, organic matter and available phosphorus were found to increase with the degree of tillage, while the bulk density, iron oxide and aluminium oxide were found to decrease with the degree of tillage. The results show that the soil productivity index was significantly (P ≤ 0.05) affected by the tillage methods and found to increase with the degree of tillage.

Organic Corn Production Practices and Profitability in the Eastern U.S. Corn Belt

Efforts to assess and improve the sustainability performance of the growing organic farming sector depend on an accurate understanding of farm structure and management practices. To contribute to the dearth of literature in this area, we conducted a survey of over 850 certified organic corn growers in four states (Indiana, Michigan, Ohio, and Pennsylvania) in the spring of 2018. Findings show that most organic corn growers in this region had diversified livestock operations (mostly dairy) on relatively small farms (10–100 ha), which contrasts with trends of specialization and growth in farm size. More than half were dairy farmers, and nearly two-thirds farmed with horses (likely Amish). Soil fertility and health were managed by the use of manure, cover crops, forages, and a variety of other soil amendments. Organic corn growers relied heavily on moldboard plow tillage. All producers had positive net returns to labor and management in 2017, though net returns varied widely across operations. The results have implications for assessing the sustainability of organic farming systems, and for designing scientific research and extension/outreach programs to ensure they address the needs of the diverse organic farming population in this region.

Degradation of transgenic Bacillus thuringiensis proteins in corn tissue in response to post-harvest management practices.

Knowledge of the persistence of Cry proteins in transgenic corn residue after harvest is necessary to assess the ecological risk to nontarget organisms. The amount of protein remaining in crop residue declines over time by a combination of microbial decomposition and leaching, both influenced by temperature, precipitation, and the amount of residue-soil contact. Here, we investigated how long biologically active Cry proteins persist in SmartStax corn residue expressing Cry1A.105, Cry1F, Cry2Ab2, Cry3Bb1, and Cry34/35Ab1, when subjected to four post-harvest practices (chisel plow tillage, flail mowing, cover crop planting, and undisturbed residue). Protein activity in residue samples collected up to 25weeks after harvest was measured by Ostrinia nubilalis feeding bioassays and cross validated with detection frequencies determined by ELISA. All corn residue remained above ground in the flail-mowed and undisturbed treatments, while the cover crop and chisel plow treatments left 88.3 and 39.6% of the residue remaining above ground, respectively. Cry proteins retained biological activity for as long as 24weeks after harvest when residue was left above ground with less soil contact, typical of no-till corn systems. ELISA detections were positively correlated with results of the feeding bioassays, which revealed the presence of active proteins beyond the point of ELISA detection.

Effects of moisture content and tillage methods on creep properties of paddy soil.

The rheological properties parameters of paddy soil affect the interaction between the tillage tools and soil, thus influencing the operation quality and power consumption. In order to study the effects of tillage methods and moisture content on the rheological properties parameters of paddy soil in the middle and lower reaches of the Yangtze River, uniaxial compression creep tests of paddy soils with four moisture contents under no tillage (moisture contents: 26.71%, 24.52%, 23.26%, 21.28%) and plough tillage (moisture contents: 26.77%, 25.55%, 23.40%, 20.56%) were carried out using a TMS-PRO texture analyzer. The creep properties curves obtained from the tests, and the rheological constitutive equation of paddy soil under compression was established by Burgers viscoelastic model. Respectively, the quantitative change rules of creep properties of paddy soil with different moisture contents under different tillage methods and the correlation between these parameters were explored. The results showed that the moisture content under the three-year plough tillage and no tillage methods had significant influence on the rheological properties parameters of paddy soil (P < 0.05). The instantaneous elastic modulus, delay elastic modulus, and viscosity coefficient of the two paddy soils (no tillage and plough tillage soils) decreased with the increase of moisture content. However, the variation rules of relaxation time and delay viscosity coefficient with moisture content differed between these two paddy soils. Specifically, the strain rate of the two paddy soils decreased as moisture content decreased, where the total strain combines elastic strain, viscous strain, and viscoelastic strain. The initial strain rate and steady strain rate of the plough tillage paddy soils were lower than that of the no tillage paddy soils. The established creep model equation could be used to obtain viscoelastic rheological parameters of paddy soil in a wide range. The fitting equations between rheological parameters and moisture content were introduced into Burgers model, and the coupling equations between creep deformation and moisture content and time were derived, which could be used to predict the creep properties and deformation behavior of paddy soil in a certain range of no tillage and ploughed field. Overall, this study has a certain theoretical significance for the development and improvement of paddy soil rheology theory, and can also provide theoretical basis and technical support for the research of agricultural machinery design optimization, field water, soil conservation, soil tillage and compaction related simulation analysis in the middle and lower reaches of the Yangtze River.

Conventional and conservation tillage practices affect soil microbial co-occurrence patterns and are associated with crop yields

A comprehensive understanding of the effects of tillage practices on soil microbial communities is fundamental to a better understanding of their roles in maintaining or improving the stability of agroecosystems. However, little is known regarding soil microbial co-occurrence patterns and their function in ecosystems shaped by long-term tillage practices. The goal of the present study was to investigate the impact of no-tillage (NT), reduced tillage (RT) and moldboard plow tillage (MP) practices on soil microbial interactions, central species and functional taxa as well as to investigate their associations with crop yields. The results showed that the average node degree was lower in the RT network than in the NT and MP networks of bulk and rhizosphere soils, indicating inefficient mutual effects among taxa and a more stable network structure induced by RT. Moldboard plow tillage resulted in the most fungal-fungal interactions (17.6%), while RT yielded the most bacterial-fungal interactions (32.3%) in the rhizosphere soils. The potential plant pathogens Fusarium were identified as hub node with most connections, and pathogen Sphingomonas and Clonostachys were found as central speices with those simultaneously termed as hub node and generalist in the MP network of rhizosphere soils. Intriguingly, these potential plant pathogens had negative correlations with crop yields in both bulk and rhizosphere soils, as determined by structural equation modeling (SEM). In contrast, RT might help to alleviate the ecological risks of the potential plant pathogens and increased the availability of soil nutrients mediated by central species, such as Nitrospira. These findings suggested RT as an optimal practice that could stabilize microbial network structure, alleviated the potential transmission of pathogens and finally enhance crop yields, providing a new perspective for tillage application in agroecosystems.

The Effect of the Manner in Which Montane and Submontane Areas Are Utilized on the Quality of Leachate Water

This study aimed at assessing the effect of how submontane soils are managed on the quantity and quality of leachate water, as well as on the load of nutrients leached with it. The quality of leachate water moving through the soil profile at the depth of 0–30 cm was investigated. The quality of leachate water from six research variants was analyzed in three periods: intensive growing, inhibited growing, and the non-growing season. It was established that the type of flora had a significant effect on the amount and chemical composition of water flowing through the soil profile. The highest loads of minerals were leached with leachate waters from arable land. Contrary to the common opinion, unused meadow had the best quality of leachate waters. On account of the quality of leachate waters in submontane and montane areas, it is recommended to reduce plow tillage in these areas. It is also recommended to use these areas as meadows and pastures, with moderate fertilization and rational use, i.e., two mowings or three grazings during the growing season. The study emphasizes how important the management of the use of submontane and montane areas is for the quality and quantity of leachate waters.

Neoteinic and dwarf weeds: distribution, biology, control

Goal. To determine the features of the distribution, occurrence, biology, harmfulness and methods of control of neoteinic and dwarf weeds in the conditions of the Left Bank Steppе.&#x0D; Methods. The studies were carried out during 2017—2020 by route and expeditionary surveys. Weeds were counted 6—12 times.&#x0D; Results. Neoteinic forms and dwarf plants were found in agricultural crops throughout the growing season. The number of weeds prone to neotenia made up 43 species. The duration of the period from germination to seed ripening varied in them within 14—34 days. Plant height was 2.8—12.4 cm. Their average seed productivity did not exceed 19—21 pcs. from the plant. The mass of 1000 seeds was 12—19% higher, and the germination rate was 21—34% higher than in conventional forms. At an average density of plants, up to 3.43—3.84 thousand pieces/m2 of seeds entered the soil. Stubble ploughing and subsequent basic tillage provided 100% control of them. Late autumn application of herbicides to control neoteinic and other annual weeds was impractical. Dwarf plant species in agrophytocenoses were represented by 27 species. The number of their seedlings in winter crops ranged from 11—16 to 237—334 pieces/ m2, for spring and row crops — from 37—53 to 365—489 pieces/m2. The height of the plants was 10.8—17.5 cm, and the seed productivity was from 6 to 609 pcs. With the density of these weeds at the level of 145—160 pcs/m2, they were consumed in crops of winter wheat 18.9 kg/hectare of nitrogen, 31.0 kg/hectare of phosphorus and 27.8 kg/hectare of potassium. Average water consumption was 141 m3/hectare. The loss of wheat grain was 0.48 t/h. In the fields for grain, cereals and row spring crops, high efficiency of control in all forms and types of weeds was achieved in a system of combination of soil cultivation, which included harrowing, seed bed preparation of autumn plows, as well as the use of herbicides. In the crops of winter wheat and barley, the maximum destruction of weeds was achieved from the use of leaf herbicides in autumn 10—12 days before the end of the growing season or at the beginning of the spring growing season.&#x0D; Conclusions. The main attention in the control system of neotenic and dwarf weeds belongs to the summer-autumn technological method by 1—2-fold stubble plowing. Additionally, in sowing of spring crops, they are destroyed in the system of pre-sowing soil cultivation in combination with herbicides, and in winter crops by the use of leaf herbicides in autumn or early spring.

The Influence of Soil Tillage System on Changes in Gas Exchange Parameters of Pisum sativum L.

A field experiment was carried out in 2017–2019 as a split-plot design with four replicates at the Agricultural Experimental Station in Grabów, Poland. The aim of the study was to compare the gas exchange parameters of the pea depending on the use of different soil tillage systems. Physiological plant parameters as: net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci) and relative chlorophyll content were measured in three developmental stages. The study have showed that all the measured parameters were affected by the tillage system of the soil. Net photosynthetic rate and transpiration rate were significantly lower in the treatments, where simplified-tillage was applied. Pea grown in the plough tillage (CT) showed a generally higher rate of net photosynthesis and transpiration rate compared to that of peas grown in the reduced tillage and no-tillage systems, but this was dependent on the plant development stage and the weather conditions prevailing in a given year. The highest intercellular CO2 concentration (Ci) under different cultivation methods were found in the no-tillage system, regardless of the developmental stage of legumes. The values of determination coefficients showed a positive relationship between the photosynthetic rate and seed yield of the peas tested in all the years of the research. The study also showed that a significantly higher SPAD index was found in the CT tillage system, irrespectively on the developmental stage.

Perennial grass ley rotations with annual crops in tropical Africa: A review

AbstractRotation of grass ley with periods of annual crop production can be a means to increased farming system productivity, sustainability, and profitability. This research review offers interpretations of rotation research results for future African agriculture. Some rotation studies were with naturally generated and severely over‐grazed fallows consisting primarily of annual plant species but other studies were with planted and well‐managed perennial grass ley. Generally, the rotations increased annual crop yields with soil improvement. System benefits were similar or greater for ley compared with fallow with generally higher fodder yields with ley. Surface crusting of sandy soil in the Sahel is a major concern that may be worsened by fallow due to the deposition of clay and silt particles. Ley and fallow were terminated in all studies with inversion plow tillage with more tillage for subsequent crops while the rotation benefits may be greater with less tillage. Most studies did not have fertilizer use but annual crop yield response to fertilizer was greatly increased following ley in one study and with no system by fertilizer interaction effect in three studies. The profitability of ley rotations will vary with fodder demand which is rapidly increasing, especially near urban areas. Strip cropping, for example, alternate ley with annual crop strips of 5–20 m width and rotation cycles of 6–10 yr, may often be optimal for erosion control and sediment trapping, protection from uncontrolled grazing, and nearby supply of vegetative planting material for ley re‐establishment. Rotation management can be improved through experiential learning and experimentation.

Crop development has more influence on shaping rhizobacteria of wheat than tillage practice and crop rotation pattern in an arid agroecosystem

Root-associated bacteria are studied under a single agricultural measure, but the responses of rhizosphere bacterial communities toward agricultural management, in an arid agroecosystem, are unclear. Here, we evaluated the effects of tillage practice, crop rotation pattern, and crop development on rhizobacteria in a field experiment in the dryland region of northern China. Three tillage [chisel plow tillage (conservation), zero tillage (conservation), and plow tillage (conventional)] practices and two crop rotation (maize–wheat rotation and soybean–wheat rotation) patterns were been combined to assess changes in rhizosphere bacterial communities during wheat development. Our results showed that conservation tillage practices had considerable effects on soil physicochemical properties compared with conventional tillage, thus changing the rhizosphere microenvironment. Spearman's correlation analysis also indicated that soil physicochemical properties were closely related to the relationships among the rhizosphere bacterial communities and taxa. Furthermore, the composition and α-diversity of the rhizosphere bacterial communities were substantially affected by the crop growth stage and tillage practices; however, the legacy effect of the previous crop had different effects on the rhizosphere bacterial communities owing to the short period of implementing crop rotation. The phylogenetic diversity and taxonomic composition of rhizosphere bacterial communities were mainly explained by the crop growth stage and tillage practice, respectively. Additionally, conservation tillage practices and soybean–wheat rotation pattern both delayed rhizobacteria successions. Co-occurrence networks also showed that the differential modules among the rhizosphere bacterial communities decreased with wheat development, whereas the soybean–wheat rotation pattern increased their degree of co-occurrence. The differences in taxonomic compositions and phylogenetic diversities of the rhizosphere bacterial communities may affect their potential functions and alter crop growth and development.

Rhizobacterial communities and crop development in response to long-term tillage practices in maize and soybean fields on the Loess Plateau of China

Conservation tillage, that is, reduced or zero tillage, can change the soil ecological environment and rhizosphere bacterial communities. Here, we investigated temporal variations in rhizosphere bacterial communities during crop development and their relationships with crop growth characteristics under three tillage practices (Plow tillage (PT), chisel plough tillage (CPT), and zero tillage (ZT)) in maize and soybean fields on the Loess Plateau of China. Conservation tillage (CPT and ZT) practices significantly increased the contents of soil moisture (3.62–13.13%), soil organic carbon (29.19–39.67%), and nitrogen (38.69–60.23%) and decreased soil pH (1.15–3.76%). The overall responses of rhizosphere bacterial community composition to tillage practice and phenological period were taxonomically consistent across maize and soybean fields, and changes were predominantly observed in the relative abundances of dominant bacterial phyla. Co-occurrence network analysis indicated that the average connectivity degree among 16S operational taxonomic units was higher under PT (38.92% and 73.60%) practice than under CPT and ZT practices. CPT practice tended to increase the total biomass and nitrogen accumulation of maize and soybean compared with PT practice, whereas ZT practice significantly (P < 0.05) decreased them. Partial least squares path modeling analysis showed that temporal variations in the rhizosphere bacterial communities (explained variations in maize and soybean fields were 94.7% and 92.7%, respectively) were regulated by tillage practices and phenological periods, and partly explained the changes in growth dynamics of maize and soybean (0.161 and 0.031, respectively). Overall, CPT practice could improve the soil ecological environment and promote crop growth in the China’s Loess Plateau. Therefore, we recommend that CPT practice should be adopted in semi-arid agricultural areas to improve the potential relationships between the underground and aboveground in agroecosystems.

Simulation of Fuel Consumption Based on Engine Load Level of a 95 kW Partial Power-Shift Transmission Tractor

This study is focused on the estimation of fuel consumption of the power-shift transmission (PST) tractor based on PTO (power take-off) dynamometer test. The simulation model of PST tractor was developed using the configurations and powertrain of the real PST tractor. The PTO dynamometer was installed to measure the engine load and fuel consumption at various engine load levels (40, 50, 60, 70, 80, and 90%), and verify the simulation model. The axle load was also predicted using tractor’s specifications as an input parameter of the simulation model. The simulation and measured results were analyzed and compared statistically. It was observed that the engine load, as well as fuel consumption, were directly proportional to the engine load levels. However, it was statistically proved that there was no significant difference between the simulation and measured engine torque and fuel consumption at each load level. The regression equations show that there was an exponential relationship between the fuel consumption and engine load levels. However, the specific fuel consumptions (SFC) for both simulation and measured were linear relationships and had no significant difference between them at each engine load level. The results were statistically proved that the simulation and measured SFCs were similar trends. The plow tillage operation could be performed at the gear stage of 7.65 km/h with higher working efficiency at low fuel consumption. The drawback of this study is to use a constant axle load instead of dynamic load. This study can provide useful information for both researchers and manufacturers related to the automated transmission of an agricultural tractor, especially PST tractor for digital farming solutions. Finally, it could contribute to the manufacturers developing a new agricultural tractor with higher fuel efficiency.

Soil Physical Properties, Carbon dioxide Emissions and Their Relationships under Different Management Systems in Semi-arid Region of Eastern Tunisia

ABSTRACT In agricultural systems, soil carbon dioxide emissions and physical properties are thought to depend largely on management practices. This field study was carried out in a semi-arid region of eastern Tunisia to evaluate the effects of tillage management on soil carbon dioxide emissions and related physical properties; bulk density (BD), penetration resistance (PR), total porosity (TP) and air-filled porosity (AFP). Tillage management treatments included plowing with a moldboard plow or a disk plow to different depths, described here as shallow (10 cm), medium (15 cm) and deep (25 cm). No-tillage was also considered as a control plot. Correlation analysis was used to explore how soil carbon dioxide emissions (CO2) were related to the other studied properties. The results showed higher carbon dioxide (CO2) emissions (p < .05) from tilled soil compared to no-till (NT), regardless of the tillage management. No significant differences in carbon dioxide (CO2) emissions were found between moldboard and disk plow tillage at the same tillage depth. Soil carbon dioxide release was the highest after deep tillage (moldboard = 0.101 t ha−1 and disk plow = 0.107 t ha−1) suggesting that deeper tillage to 25 cm promoted higher carbon dioxide (CO2) emissions. Significant differences with tillage were observed in bulk density (BD) and penetration resistance (PR) compared to no-tillage. Correlations of carbon dioxide emissions to soil physical properties across all the tillage treatments indicated significant negative relationships between carbon dioxide (CO2) emissions and soil bulk density (BD) and penetration resistance (PR) and significant positive relationships between carbon dioxide (CO2) and total porosity (TP) and air-filled porosity (WFP) suggesting that these soil attributes are important controlling factors of carbon dioxide (CO2) emissions.