Tillage Operations Research Articles

Autumn Tillage Reduces the Effect of Plant Cover on Topsoil Nitrogen Leaching

Keeping cover crops to reduce nitrogen leaching often conflicts with timing tillage operations before the soil becomes un-trafficable during winter, while leaving cover crops in the field until spring raises concerns over pre-emptive competition with the following crop. Therefore, farmers may resort to tilling their fields in autumn after letting cover crops remain in the fields for only a short period of time. We explore the effects of this practice in a laboratory lysimeter setting by analyzing the leaching of nitrate from intact topsoil cores. Cores were extracted from no-till (NT) plots and plots tilled in autumn (AuT), in areas kept bare (B) and with volunteer winter rye plant cover (V) after harvest. Nitrate breakthrough curves show that V significantly reduced N leaching by 61% relative to B in NT, but did not have a significant effect in AuT. Dissection of leached cores and undisturbed reference cores indicated a significant removal of mineral N from the soil during the lysimeter experiment for all treatments except V in NT. This indicates that volunteer cover removed a crucial amount of leachable N and suggests that tillage counteracted the effect of V in AuT, likely due to a combination of reduced uptake and re-mineralization of N in cover crop residue.

Horizontal and vertical fluxes of particulate matter during wind erosion on arable land in the province La Pampa, Argentina

A detailed analysis of horizontal and vertical particulate matter (PM) fluxes during wind erosion has been done, based on measurements of PM smaller than 10, 2.5, and 1.0 μm, at windward and leeward positions on a measuring field. The three fractions of PM measurement are differently influenced by the increasing wind and shear velocities of the wind. The measured concentrations of the coarser fractions of the fine dust, PM10, and PM2.5, increase with wind and shear velocity, whereas the PM1.0 concentrations show no clear correlation to the shear velocity. The share of PM2.5 on PM10 depends on the measurement height and wind speed and varies between 4 and 12 m/s at the 1 m height ranging from 25% to 7% (average 10%), and at the 4 m height from 39% to 23% (average 30%). Although general relationships between wind speed, PM concentration, and horizontal and vertical fluxes could be found, the contribution of the measuring field was very low, as balances of incoming and outgoing fluxes show. Consequently, the measured PM concentrations are determined from a variety of sources, such as traffic on unpaved roads, cattle drives, tillage operations, and wind erosion, and thus, represent all components of land use and landscape structure in the near and far surroundings of the measuring field. The current results may reflect factors from the landscape scale rather than the influence of field-related variables. The measuring devices used to monitor PM concentrations showed differences of up to 20%, which led to considerable deviations when determining total balances. Differences up to 67% between the calculated fluxes prove the necessity of a previous calibration of the devices used.

The Effects of Different Tillage Techniques on the Production Costs in Fallow-Wheat Rotation System

The adoption and applicability of the technologies developed in agriculture by farmers are very important for agronomic studies. There are a limited number of economic studies comparing different tillage methods with each other. This study was conducted in the land of Polatlı Agricultural Enterprise between 2011 and 2017 to determine the amounts of physical production inputs and unit production costs of three different tillage operations in the fallow-wheat rotation system. The data consist of the production inputs in the Conventional Tillage, Minimum Tillage, and Direct Seeding practices. For the economic analysis, Single Product Budget Analysis was used. All the farmers’ production costs in the fallow-wheat rotation system were considered in the analysis. Among the practices, Gross Production Value (GPV) was obtained the most from the (509.63$ ha-1) practice. This practice was followed by Direct Seeding (486.13$ ha-1) and Minimum Tillage (421.92$ ha-1) practices, respectively. The profit threshold was exceeded in all practices, and production activities’ variable and total costs were fulfilled. The highest relative profit rate was obtained in Direct Seeding (1.77) practice, and it was followed by Conventional Tillage (1.30) and Minimum Tillage (1.08) practices, respectively. In order to obtain an income of $1 in wheat production, the lowest production cost was obtained in the Direct Seeding practice. With the Direct Seeding application, it can be ensured that economic wheat production, preservation of soil structure, reduction of input costs, and less economic damage to the farmer in changing climate conditions can be achieved.

Straw-Soil-Rotary Blade Interaction: Interactive Effects of Multiple Operation Parameters on the Straw Movement

Conventional soil-tool interaction has been upgraded to straw-soil-tool interaction due to plenty of straw remains in the field after harvesting. Understanding the straw-soil-tool interaction relationship and quantifying the straw movement and distribution characteristics at various tillage operation parameters is critical for straw management and the design of tillage tools. Here, in order to investigate the interactive effects of key operation parameters on the displacement and burial of straw, a specific field test rig was developed to perform straw movement test. According to the singe-factor test and multifactor interactive experiment, we investigated the effect of straw length, tillage depth and rotary speed on straw movement, and established a mathematical model between operation parameters and straw movement. The results showed that the significant order of the influence on the displacement and burial of straw was as follows: the tillage depth, the straw length, the rotary speed. As determined by response surface analysis, the optimal combination of parameters for straw incorporation was straw length of 5 cm, tillage depth of 13 cm, and rotary speed of 320 rpm, and the corresponding straw burial rate and straw displacement were 95.5% and 27.6 cm, respectively. The relative errors of the optimization results are less than 5%. These results indicated that the mathematical model can be used to predict and evaluate straw movement. Therefore, it is feasible to enhance the straw incorporation performance by a reasonable setting of operation parameters, which may provide a comprehensive strategy to improve the working quality of tillage tools.

Higher Profitability of WheatMungbean-Rice System Through Conservation Agriculture Practice in Sub-Tropical Climate of Bangladesh

Two-Wheel Tractor (2WT) operated plow tillage and crop residue exclusion practices in the rice-wheat system are costly, labor-intensive, soil destructive, and non-ecofriendly. In recent years, pursuits of healthy food production through sustaining the productive capacity of soils, and environmental quality, have raised concerns to adopt Conservation Agriculture (CA) worldwide. Single-Pass Tillage (SPT) combined with herbicides and crop residue retention principles of CA is being developed in Bangladesh. Between 2014 and 2016, we conducted a two-year on-farm experiment under the wheat-mungbean-rice system in Bangladesh. These crops were grown under two crop establishment methods; T1: Plow Tillage (PT) + three times manual weeding by hand, and T2: Pre-plant knockdown herbicide (PRE) + SPT + Pre-emergence herbicide (PE) + Post-emergence herbicide (PO). Treatments were combined with two levels of crop residues, R0: zero residues and R50: 50% anchored residue. The PT was accomplished with two primary tillage operations performed by a 2WT, whereas SPT was completed by a single-pass process using a Versatile Multi-crop Planter machine. The PRE: glyphosate, PE: pendimethalin for all crops, and PO: carfentrazone-ethyl+isoproturon, fenoxaprop-p-ethyl, and ethoxysulfuron-ethyl for wheat, mungbean, and rice, respectively, were applied at the prescribed dosage and time. Data reveal that, relative to traditional practice (PT+3HW without residue), the CA practice (PRE + SPT + PE + PO with 50% residue) resulted in 30, 39, and 15% higher yield and 37, 29, and 22% higher economic returns in wheat, mungbean, and rice, respectively. The productivity of the wheat-mungbean-rice system was 41% higher than that of the wheat-rice system.

Carbon sequestration of hazelnut orchards in central Italy

The cultivation of European hazelnut (Corylus avellana L.) is showing a rapid increase due to the high global demand for hazelnuts from the confectionery industry also affecting Italy, which is the second largest hazelnut producing country after Turkey. Like most tree crops, hazelnut tree planting includes land preparation and frequent tillage operations during the first years of growing seasons to avoid weed competition, whereas after 3 years the soils are usually permanently grass covered. The aim of this work is to develop a model of carbon sequestration based on the age of hazelnut orchards, using permanent grasslands as reference for previous land use. The results demonstrate that soil carbon stock (sCS30) tends to decrease between 23% and 58% during the first 3–5 years after cultivation. This carbon depletion is only partially compensated by the carbon sequestration of the hazelnut trees, variable from about 0.6–3.3 Mg C ha−1. Adult hazelnut orchards showed high levels of sCS30, as well as higher carbon stock (CS) from tree biomass, resulting in similar, or even higher carbon sequestration potential of the grassland. In some cases, excessive nitrogen fertilization seems to decrease the carbon sequestration potential of the soil. In conclusion, the land use change from grassland to hazelnut cultivation has a short-term negative impact in terms of soil carbon sequestration. In orchards with optimal fertilization and management, sCS30 is recovered and exponentially increased, highlighting the high carbon sequestration potential offered by this kind of perennial nut crop.

Design and test of a positioning system for a greenhouse electric micro-tiller based on ultra-wideband

Abstract. A positioning system for ultra-wideband (UWB) electric micro-tillers suitable for complex greenhouse environments was designed as the basis for realizing unmanned micro-tillers to address the problem of the frequent safety accidents of existing micro-tillers. First, the positioning base station and tag were designed on the basis of the STM32 and DW1000 chip hardware. The real-time coordinate display of the micro-tiller in the greenhouse could also be realized with the design of the upper computer software. Then, the realization method of the positioning function, including the analysis of time difference of arrival (TDOA) and two-way ranging (TWR) positioning methods, and the selection of the best Taylor positioning algorithm through a MATLAB simulation were studied to reduce the influence of noise and measurement errors on measurement accuracy. Finally, a positioning system accuracy test was conducted. Test results revealed that the maximum positioning error of the micro-tiller positioning system is no more than 6 cm, and the average error is 4.4 cm. The optimized positioning error is reduced by 10.2 %, considering that the influence of the base station location on the accuracy. The positioning system of the greenhouse electric micro-tiller designed in this paper demonstrates a stable performance and positioning accuracy to meet the needs of greenhouse rotary tillage operations. This system has certain theoretical importance and reference value for the development of precise positioning technology for working tools in the greenhouse and the further realization of unmanned rotary tillage operations.

Innovative Living Mulch Management Strategies for Organic Conservation Field Vegetables: Evaluation of Continuous Mowing, Flaming, and Tillage Performances

Organic vegetable production is particularly affected by weed pressure and mechanical weeding is the major tactic implemented by growers to keep weeds under economic thresholds. Living mulch (LM) has been shown to provide several environmental services; however, LM management is required to avoid competition between service crops and cash crops. The aim of this trial was to evaluate two innovative LM-based management systems: a system that provided LM growth regulation by means of flaming (LM-FL) and a system where the LM was regularly mowed by an autonomous mower (LM-AM), both compared with a control without LM and based on standard tillage operations (TILL). The three management systems were evaluated in terms of crop production, weed control, and energy consumption on a 2 yr organic crop rotation of cauliflower (Brassica oleracea L. var botrytis) and eggplant (Solanum melongena L.). LM-AM produced an acceptable fresh marketable yield for both vegetable crops. Moreover, the weed dry biomass obtained in LM-AM-managed plots was lower compared to the LM-FL plots and ranged approximately from 200 to 300 kg ha−1. Furthermore, LM-AM management resulted in lower energy consumption (−2330 kWh ha−1 with respect to the TILL system and −7225 kWh ha−1 with respect to the LM-FL system). The results of this trial suggest that autonomous mowers have a great potential to improve LM management and help with implementing sustainable organic vegetable systems.

Effect of Straw Length, Stubble Height and Rotary Speed on Residue Incorporation by Rotary Tillage in Intensive Rice–Wheat Rotation System

High-yielding agriculture in an intensive rice–wheat rotation system leads to plenty of residues left in the field after harvest, which is detrimental to seeding operation, seed germination, and early plant growth. Some residue thus needs to be incorporated into the soil. Providing the relationship between tillage operations and residue incorporation and establishing a mathematical model play important roles in residue management and the design of tillage machinery. In order to obtain detailed data on the interaction between residue incorporation and tillage operations, a multifunctional field-testing bench with precise parameter control was developed to assess residue incorporation characteristics of rotary tillage, and we investigated the effects of straw length, stubble height and rotary speed on residue incorporation. Three experimental factors affecting residue incorporation performance were studied, i.e., six lengths of straw (30–150 mm), four heights of stubble (50–200 mm), and three rotary speeds (240–320 rpm). Chopped straw and stubble with certain sizes were prepared for the test, and we measured the burying rate and distribution uniformity of residue after rotary tillage. The results indicated that straw length, stubble height, and rotary speed all impact residue incorporation quality. The burying rate and distribution uniformity of residue decreased with the increase in straw length and stubble height; a lower rotary speed parameter buried less residue and distributed it with worse uniformity than a higher one. It is suggested that farmers determine the straw length and stubble height at the stage of harvest according to the required burying rate and distribution uniformity of residue.

Soil Compaction from Wheel Traffic under Three Tillage Systems

Agricultural fields are usually subjected to high amounts of traffic from field operations. The influence of traffic on sandy loam soil in three tillage systems were investigated in a field experiment. The field was located in a Canadian prairie region. In the experiment, the treatments were three tillage systems: no-tillage, disc tillage, and spring-tine tillage. Following tillage operations, field plots were trafficked with one pass of a sub-compact tractor. Soil properties were measured before and after the traffic to examine the effects of tillage systems and wheel traffic. For the effects of the tillage systems on the soil bulk density, soil shear strength, soil surface resistance, and soil cone index, the no-tillage system had higher values for all the soil properties when compared with the disc and spring-tine tillage systems. The plant (canola) population density ranged from 18.2 plants/m2 to 34.9 plants/m2, with the no-tillage having the lowest plant densities. For the effects of wheel traffic, one pass of the tractor in the disc and spring-tine tillage plots resulted in a 2.7% and 17.4% reduction in soil moisture content, respectively. After wheel traffic, the average soil shear strength for the disc and spring-tine systems were still significantly lower than the no-tilled system. Sinkages of 40 and 50 mm were observed for the spring-tine and disc tillage systems, respectively. The results of this study highlight the importance of preventing the demerits of soil compaction induced by wheel traffic after tillage operations.

Evaluation of the Impact of Best Management Practices on Streamflow, Sediment and Nutrient Yield at Field and Watershed Scales

Evaluating Best Management Practices (BMPs) in watersheds using hydrologic and water quality models can help to establish an effective watershed water management. Soil and Water Assessment Tool (SWAT) was applied to Big Sunflower River Watershed (BSRW) and the Stovall Sherard Watershed (SSW) to evaluate BMP’s impact at watershed and field scale watersheds respectively. SWAT was calibrated and validated for streamflow, sediment yield, total nitrogen (TN), and total phosphorous (TP) at outlets of three sub-basins of the BSRW, and within the SSW. BMP scenarios of check-dam, tail water pond, vegetative filter strips (VFS), nutrient management, and tillage management were evaluated for their efficacy in reducing streamflow, sediment yield, and nutrient loads at field and watershed scales. The VFS was determined as the most effective BMP in decreasing sediment yield, TN, and TP at both field and watershed scales. At field scale, reduction of sediment yield, TN, and TP by VFS ranged from 8 to 12%, 71% to 98%, and 72% to 99% respectively and at watershed scale, reduction of sediment yield, TN, and TP by VFS ranged from 12 to 38%, 29% to 87%, and 42% to 99% respectively. The application of conservation and zero tillage operation showed reduction in sediment yield by 1% to 2% respectively but increased TN and TP by 2% to 25% at field and watershed scale watersheds. This study will help in managing water at field and watershed scale watersheds regarding BMPs selection and implementation.Graphical

Whole Body Vibration Exposure among the Tractor Operator during Soil Tillage Operation: An Evaluation using ISO 2631-5 Standard

This study is aimed at investigating the effect of various tractor ride conditions on the lumbar spine during rotavator operation. The lumbar spinal response was assessed by determining static compressive dose, i.e., Sed (8). Raw acceleration data were measured on the seat pan and seat backrest to varying tractor velocity, tillage depth, and pulling force. The field experiments have been designed using Taguchi’s L9 orthogonal array and the entire data analyzed in signal-to-noise ratios terms. The mean acceleration responses were dominant along the vertical axis and exposure levels were found beyond the exposure action value, i.e., 0.5 m/s2 as per Directive 2002/44/EU. Mean Sed (8) exceeded the limits of ISO 2631-5 indicating the probability of adverse health effects. Tractor velocity and pulling force have a significant impact on Sed (8) with a 64.43% and 27.73% percentage contribution. The FFT dominant peaks have been found in the 0.8 to 3.7 Hz frequency range. Moreover, the exact frequency of the peaks is found to be dependent on the experimental circumstances. The depicted dominant frequencies found in the range of low frequencies could lead to musculoskeletal disorders since they coincide with the natural frequencies of various parts of the body, especially in the lumbar region.

Comparative field performance evaluation of different type of Pusa Electric Power Units

Pusa developed three walk-behind type electric power units were evaluated in 9.96 ha area for tillage in polyhouse,secondary tillage, planking and weeding-cum interculture operations at research farm of ICAR-IARI during kharif and rabi 2020 and 2021. The power of four-wheel and two-wheel electric power units was 350W while Pusa mini electric prime mover was having 450W power. The controlling-cum-guiding force for operation of four-wheel power unit, two- wheel power unit and mini electric prime mover was found 26.72, 30.9 and 22.7 N, respectively. Correspondingly, the draft force was 210, 245 and 300 N. Based on the rigorous field study, the effective field capacity with these electric power units were 2.3 times higher than manual operated four-wheel weeder for wide-row crops. The field efficiency with four-wheel, two-wheel electric power unit and mini electric prime mover was 78–83.26, 78.6–81.25 and 69.2–92.6% in weeding-cum-interculture operation, respectively. The walk-behind electric power units are also found to reduce operator’s drudgery by 80–85%. The mini electric prime mover was found 32.7% cheaper than the four-wheel and 17.2% than the two-wheel power unit. Its command area is one ha for secondary tillage and 5 ha for weeding-cum-interculture operations in wide-row crops.

Quantification of Dust Emissions during Tillage Operations in Steep Slope Vineyards in the Moselle Area

Measurements of dust emissions and the modeling of dissipation dynamics and total values are related to great uncertainties. Agricultural activity, especially soil cultivation, may be an essential component to calculate and model local and regional dust dynamics and even connect to the global dust cycle. To budget total dust and to assess the impact of tillage, measurement of mobilized and transported dust is an essential but rare basis. In this study, a simple measurement concept with Modified Wilson and Cook samplers was applied for dust measurements on a small temporal and spatial scale on steep-slope vineyards in the Moselle area. Without mechanical impact, a mean horizontal flux of 0.01 g m2 min−1 was measured, while row tillage produced a mean horizontal flux of 5.92 g m2 min−1 of mobilized material and 4.18 g m2 min−1 emitted dust from site (=soil loss). Compared on this singular-event basis, emissions during tillage operations generated 99.89% of total emitted dust from the site under low mean wind velocities. The results also indicate a differing impact of specific cultivation operations, mulching, and tillage tools as well as the additional influence of environmental conditions, with highest emissions on dry soil and with additional wind impact. The dust source function is strongly associated with cultivation operations, implying highly dynamic but also regular and thus predictable and projectable emission peaks of total suspended particles. Detailed knowledge of the effects of mechanical impulses and reliable quantification of the local dust emission inventory are a basis for analysis of risk potential and choice of adequate management options.

Long-term impact of zero-till residue management in post-rainy seasons after puddled rice and cropping intensification on weed seedbank, above-ground weed flora and crop productivity

Regulation in weed seed recruitment to soil and its emergence is an ecological approach of weed management for sustainable cropping intensification and land restoration. Intensive tillage operations in rice (Oryza sativa L.) - wheat (Triticum aestivum L.) system is a predominant practice in the South East Asian countries. This practice has emerged as an unsustainable crop management options. Consequently, zero tillage (ZT) in post–rainy seasons after conventional tilled (CT) puddled transplanted rice is being adopted to minimize tillage intensity in system in these regions. However, long–term impact of continuous CT in all seasons versus seasonal ZT (in post–rainy seasons) after puddled transplanted rice with crop residues in cropping system mode on above– and below– ground weed density and diversity is not adequately studied. Hence, we examined four tillage based residue management: (i) conventional tillage in each crop of rotation without residue (CT–CT), (ii) conventional tillage in each crop with incorporated residue (CT–CT + R), (iii) conventional tilled puddled transplanted rice – zero tillage in post–rainy season crops without residue (CT–ZT), (iv) conventional tilled puddled transplanted rice – zero tillage in post–rainy season crops with surface residue mulch (CT–ZT + R) each with three levels of crop rotation: (i) rice – wheat (R–W), (ii) rice – chickpea (Cicer arietinum L.) (R–C), (iii) rice – chickpea – mungbean (Vigna radiata (L.) (R–C–Mb) in split–plot design in Kanpur, India. Zero tillage in post–rainy seasons after conventional tilled rice resulted in 11%, 23%, and 13% lower (P < 0.05) weed seed density than CT–CT at 0–7.5, 7.5–15, and 0–15 cm depth, respectively. However, zero-tilled residue management had 15–19% and 10–14% (P < 0.05) higher above–ground weed density compared with CT–CT. Rice-chickpea-mungbean rotation reduced weed seed density by 6–11%, 4–11%, and 6–8% (P < 0.05) than those of rice-wheat and rice-chickpea across depth. In contrast, rice-chickpea-mungbean had 30–38% higher total above–ground weed density than rest of the crop rotations. Post–rainy seasons zero tillage with and without residues attributed higher weed diversity indices (Shannon and Simpson) compared with conventional tillage in seedbank. Importantly, CT–ZT + R with R–C–Mb (interaction) reduced 24% total viable seed density at 0–15 cm depth than CT–CT with R–W. Further, this system brought about 15% and 62% higher rice seed yield and system productivity over CT–CT with R–W, respectively. Conventional tilled puddled transplanted rice – zero tillage with added residues increased 16% and 33% seed yield of wheat and chickpea compared with CT–CT (P < 0.05), respectively. Thus, it can be concluded that zero tillage in post-rainy seasons after puddled transplanted rice and intensive pulse based cropping (rice-chickpea-mungbean) can minimize viable weed seeds in soil vis–a–vis above–ground weed density over time than conventional tillage and rice-wheat system. The reduced weed density could reduce soil fertility degradation, enhance crop/system productivity, restore soil health and provides opportunity for sustainable cropping intensification in rice ecologies of the Indo-Gangetic plains.

Zero Tillage, Residue Retention and System-Intensification with Legumes for Enhanced Pearl Millet Productivity and Mineral Biofortification

Pearl millet-based cropping systems with intensive tillage operations prior to sowing have limited sustainable productivity in the low-irrigation conditions of semi-arid farming ecologies, such as those in the north Indian plains. The adoption of improved management practices such as zero tillage with residue retention (ZTR) and diversification with the inclusion of summer pulse crops has the potential to improve cropping system sustainability. Therefore, an experiment was designed to compare two improved management practices, zero tillage (ZT) and ZTR, to conventional tillage (CT), across three pearl millet-based cropping systems: pearl millet–chickpea (PM–CP), PM–CP–mungbean (MB), and PM–CP–forage pearl millet in a two-year experiment. Experimental treatments were compared in terms of pearl millet productivity, mineral biofortification, and greenhouse gas emissions. Results showed a significant increase in pearl millet yield attributes, grain and stover productivity, nutrient uptake, and micronutrient biofortification in the PM–CP–MB cropping system under ZTR relative to other treatment combinations. On-farm evaluation at different locations also showed that the intensification of PM–CP system using summer crops enhanced pearl millet productivity across diverse tillage systems. Overall, zero tillage practices combined with diversified pearl millet-based cropping systems are likely to be management practices, which farmers can use to sustainably maintain or increase cropping system productivity in the various semi-arid areas of the world.

Seedbank persistence of four summer grass weed species in the northeast cropping region of Australia.

Summer grass weed species are a particular problem in the northeast cropping region of Australia because they are prolific seeders and favor no-till systems. Information on weed seed persistence levels can be used for the development of effective and sustainable integrated weed management programs. A field study was conducted over 42 months to evaluate the seedbank persistence of Chloris truncata, C. virgata, Dactyloctenium radulans, and Urochloa panicoides as affected by burial depth (0, 2, and 10 cm). Regardless of species, buried seeds persisted longer than surface seeds and there was no difference in seed persistence between 2 and 10 cm depths. Surface seeds of C. truncata depleted completely in 12 months and buried seeds in 24 months. Similarly, C. virgata seeds placed on the soil surface depleted in 12 months. Buried seeds of this species took 18 months to completely deplete, suggesting that C. truncata seeds persist longer than C. virgata seeds. Surface seeds of D. radulans took 36 months to completely deplete, whereas about 7% of buried seeds were still viable at 42 months. U. panicoides took 24 and 42 months to completely exhaust the surface and buried seeds, respectively. These results suggest that leaving seeds on the soil surface will result in a more rapid depletion of the seedbank. Information on seed persistence will help to manage these weeds using strategic tillage operations.

Vertical distribution of soil aggregates and associated organic carbon fractions under conventional vegetable- and rice-based tillage operations

Context Vegetable- and rice-based cropping systems are the dominant agricultural practices across South Asia, but the conventional tillage method associated with their cultivation is responsible for soil degradation in terms of aggregates and organic carbon in the surface layer. However, knowledge of its impact on the deeper layers is needed because the aggregate and organic carbon dynamics in deeper soils are little understood. Aims This study analysed the effects of conventional rice-based tillage (RBT) and vegetable-based tillage (VBT) operations on the vertical distribution of aggregates and aggregate-associated organic carbon fractions. Methods Soil samples were collected from 10 vegetable and rice fields, where conventional tillage systems were applied, and analysed for the vertical distribution of aggregates, soil carbon stock, aggregate-associated total organic carbon (AATOC), the relationship between mean weight diameter (MWD) and AATOC, and intra-aggregate particulate organic carbon (iPOC). Key results Soil macroaggregates, MWD, AATOC, and iPOC for the surface soils under RBT were less than for soils under VBT, indicating that soils under RBT had weaker aggregate stability compared to soils under VBT. The relationship between MWD and AATOC was significant (P &lt; 0.01) for the top layers of VBT, but this relationship was non-significant for RBT. Conclusions The study suggests that wet rice cultivation has an adverse effect on soil aggregate stability and its associated organic carbon fractions. Implications Alternative tillage operations for rice-based cultivation are necessary to avoid soil degradation in rice fields.

Biology and Management of Wild Oat in Australia

Wild oat (Avena spp.) is one of the most serious weeds in Australian winter season crops such as wheat, barley, chickpea, etc. Avena fatua and A. ludoviciana are the dominant species of wild oat in cropping regions of Australia. Propagation of wild oat can occur through seeds. Dissemination of wild oat occurs by agricultural machinery, use of the contaminated seeds and crop residues, etc. Seed recruitment of wild oat in the soil occurs through high seed production and the shattering ability of plants. Wild oat has evolved resistance to many herbicides and continuous use of same herbicide could increase the resistance build-up in many populations on a large scale in Australia. The use of herbicides with different modes of action can provide cost-effective and sustainable control of wild oat. Non-chemical weed management practices, such as sanitation, residue burning, tillage operation, crop rotations, and improved crop competition approaches could reduce the infestation of this weed. For sustainable control of wild oat, integrated strategies involving chemical and non-chemical tactics may prove useful. Knowledge regarding the understanding of wild oat ecology could aid in strengthening the integrated management of this weed.

A REVIEW ON EFFECT OF WEEDS IN WHEAT (TRITICUM AESTIVUM L.) AND THEIR MANAGEMENT PRACTICES

Wheat is the second most important cereal crop in the world. It has a vital role in the human diet globally, contributing to the daily calorie and protein intake than any other cereal crops. The productivity of wheat is low because of different biotic and abiotic factors. Weeds are one of the most important competitors of wheat crop. Understanding the nature of weeds is important to develop techniques to reduce their effects on the crops. Weeds, through competition with other crops, almost always have a deleterious effect on them and may be economically and environmentally detrimental. For world food sustainability controlling the weed-induced yield losses in the wheat is of prime importance because the weeds compete with the crop and also possess deleterious effects. There are various weed species that occur in the wheat crop field and they possess effects on the growth phases of wheat. Allelopathic effects of weeds on the germination, growth and yields on the crops are recorded. The variation in the vegetative traits such as the number of fertile tillers, spike length, grains/spike due to weeds is reflected ultimately in grain yield and quality. Both broad leaf weeds and narrow leaf weeds infest the wheat crop causing a 13.1% reduction in total grain yield globally. Although tillage operations and herbicides use have played an important role in weed control, but their indiscriminate use has resulted in unacceptable consequences on humans as well as vital ecosystems along with the evolution of herbicides resistance genotypes. Through a combination of integrated weed management approaches the crop competitiveness against the weed can be increased which results in the reduction of the weed-induced yield losses in wheat. The main purpose of this study is to review the competition of weeds in wheat crops as well as its effects on wheat growth and yield components. It also highlights the management strategies which could minimize the inhibitory effect of weeds on wheat crops.