Harrow Treatment Research Articles

Effect of Land Ploughing Methods and Leveling Techniques on Wheat Production in the Upper Terraces of the Northern State - Sudan

Precision land leveling must be treated as a precursor technology for improving crop yield, enhancing input-use efficiency and ensuring long-term sustainability of the resources. A field experiment was conducted in Dongola Agricultural Research Farm, Northern State, for two successive seasons to investigate the effect of three type of ploughing; heavy disc harrow (H1), disc plough (H2) and no-ploughing (H3), and three land leveling techniques, Laser (L), Scraper (S) and traditional (T),on wheat production. The experiment was arranged in a strip split plot design and the treatments were replicated three times.
 The results indicated that effective field capacity, fuel consumption, and slippage were significantly affected by ploughing method. Laser land leveling recorded the highest fuel consumption (16.3 L/hr), and the lowest field efficiency (55%). while the heavy disc harrow recorded the highest effective field capacity (0.98 ha/hr), field efficiency (71.2%) and wheel slippage (8.1%). The soil moisture content (db %) was increased with time and depth. The highest mean soil moisture content was obtained with the laser land leveling and heavy disc harrow treatment at 75-100cm soil depth as 24.82%. The results revealed that the highest average grain yield (4.63 ton/ha) and infiltration rate (31cm/hr) were also recorded by the laser land leveling and heavy disc harrow. The treatments showed significant differences at the 5% level between the treatments for the parameters measured. Multiple regression analysis showed a highly significant effect (P≤ 0.001) of laser leveling with disc harrow ploughing on grain yield, compared to the other treatments used in the study (R2 = 0.40). The relation between the grain yield (Y) and the treatments: X1 ploughing, X2 leveling is summarized in the following equation: 
 Y = 2.875 + 0.552X1 + 0.254X2
 The study concluded that, although Laser leveling has increased the grain yield with high cost, yet it is not an expensive technique when the cost is distributed over the period of Laser leveling. The highest grain yield was obtained by the heavy disc harrow with laser land leveling.

Identification of Soil Properties and Their Effects on Crop Production under the Influence of Tillage and Residue Treatment in Western Canada

Soil provides crucial nutrients and water for the growth of canola, which is one of the most essential economic crops for prairie province in Canada. Therefore, effective and efficient methods are required to modify soil properties to improve crop development. This study systematically analyzed the combined effects of tillage operation and crop residue management on soil features. Thus, the relationship between soil properties and crop yield was also evaluated. More specifically, Aftermarket chopper treatment could cause rela tively higher soil moisture and temperature, while the Original Equipment Manufacturer (OEM) treatment could also result in dramatically higher soil organic matter (SOM) loss than Aftermarket treatment. The significantly more soil water and slightly higher soil temperature created by Aftermarket treatment was beneficial for crop yield. Although OEM treatment could cause more SOM loss, the final crop yield through this method was still lower than that using Aftermarket treatment, implying that the influence of SOM loss on crop growth remained contestable. Meanwhile, Fourier-transform infrared (FTIR) spectra showed the peaks of amides and carboxylic acids was declined during the growth of canola, which indicated that these organic contents played an essential role in the crop development. Finally, the Aftermarket * Harrow treatment was more suitable for canola cultivation, with largest amount of crop harvest and short loss of soil organic contents in the meantime.

Characterization of canola growth and in-vivo element fate in Canadian prairie under the interferences of tillage and residue treatment

Canola is one of the main crops produced in Canadian Prairie. It is important to provide an effective approach for improving the growth and yield of canola. The effects of tillage and residue management on the growth of canola have been analyzed in this study through evaluating physicochemical features of canola plants under the interferences of tillage and residue treatment. Synchrotron-based FTIR and X-ray Fluorescence Mapping technologies are used to examine the variation of different organisms and important metal elements in the canola plants at different stages. The effects of interactions among tillage and residue treatments on the growth state of canola plants at different growing stages are various. Content of lipid and protein in mature root are improved with the application of harrow treatment. The application of tillage management is beneficial for the content of some elements, while negatively influences the content of other metal elements.

Comparing Sensor-Based Adjustment of Weed Harrowing Intensity with Conventional Harrowing under Heterogeneous Field Conditions

Setting the right intensity is crucial for the success of post-emergence weed harrowing in cereals. The percentage of crop soil cover (CSC) correlates with the selectivity of weed harrowing. Therefore, real-time camera-based measurements of CSC offer a novel approach to automatically adjust the intensity of harrowing. The intensity of harrowing is varied by hydraulic steering of the tine angle. Five field experiments in cereals were conducted at three locations in southwestern Germany in 2019 and 2020 to measure the effect of camera-based harrowing (2020) and conventional harrowing on weed control efficacy (WCE), crop density, and grain yield. For this purpose, pair-wise comparisons of three fixed harrowing intensities (10°, 40°, and 70° tine angle) and three predefined CSC thresholds (CSC of 10%, 20%, and 60%) were realized in randomized complete block designs. Camera-based intensity adjustment resulted in more homogeneous CSC across the whole plot (6–16% less standard deviation variation) compared to conventional fixed settings of the tine angle. Crop density, WCE, crop biomass, and grain yield were significantly higher for camera-based harrowing than for conventional harrowing. WCE and yields of all automatic adjusted harrowing treatments were equal to the herbicide control plots. Camera-based harrowing provides a robust technology for effective weed management with a lower risk of crop damage than conventional harrowing.

Effect of Different Weed Management Strategies on Population Changing Pattern of Pennisetum polystachion in Coconut Plantations of Sri Lanka

Pennisetum polystachion is a major problematic monocotyledonous weed species and a perennial problem in intermediate zone of coconut plantations in Sri Lanka. This study was carried out to evaluate the impacts of different management systems on P. polystachion seedling emergence patterns.The tested treatments were application of glyphosate (T1), cover cropping with Pueraria phaseoloides (T2), tractor harrowing (T3), tractor slashing (T4) and tractor ploughing (T5). All the treatments were applied twice a year except T2. As T2 cover crop at the initiation of the experiment and over grown conditions were managed by harrowing once a year. Based on the reduction in weed biomass, cover cropping (T2) was the best to reduce the P. polystachion population and to reduce P. polystachion seedling emergence density in the field. Chemical weeding was the second-best method to control the P. polystachion population in the field. The effectiveness of slashing in reducing weed seedling emergence density was lower than cover cropping and chemical weeding methods. The weed seedling emergence densities were almost similar in ploughed and harrowed plots. The seed depth of emerged seedling was very high in harrowed and ploughed treatments when compared to other treatments. Results given by T3 and T5 indicates that loosening the soil creates more favorable environment for the germination of weed seeds buried in soil. Therefore, it can be argued that the elimination of weed seeds in the top 2cm or 4cm in the soil seed bank by any means is likely to reduce the level of weed infestation by about 60% to 95%. Results also indicated that burying rhizomes in ploughing and harrowing treatment plots at the depths below 30 - 40 cm is effective in controlling germination of this weed species. This experiment also suggested that keeping rhizomes on the soil surface without burying for durations of 5 – 15 days would produce weak plants with poor development.

Influence of Land-Use Legacies Following Shrub Reduction and Seeding of Big Sagebrush Sites

Big sagebrush (Artemisia tridentata Nutt.) plant communities often require management to reduce shrub density and rehabilitate understory vegetation. We studied vegetation responses to a two-way chain harrow treatment and broadcast seeding of 12 herbaceous species at eight Wyoming big sagebrush (A. tridentata Nutt. subsp. wyomingensis Beetle & Young) sites. These sites differed in land-use history; five were cultivated for dryland wheat production during the 1950−1980s and then seeded with introduced forage grasses (C-S), while three had not been exposed to this land-use legacy (non C-S). Our objective was to evaluate whether the C-S legacy influences the magnitude of vegetation change following contemporary treatment. Before treatment, C-S sites had lower sagebrush cover, higher dead sagebrush cover, and higher broom snakeweed (Gutierrezia sarothrae [Pursh] Britton & Rusby) cover than adjacent non C-S sites. Plant community change 3 years after treatment, determined with multivariate ordination analysis of species composition, varied between site histories, and response to treatment was most strongly correlated with reductions in sagebrush cover, increases in perennial grasses, and increases in 10 other herbaceous species—including some undesirable species and four that were seeded in 2010. Five years after treatment, mature sagebrush cover remained reduced for both land-use histories, yet density of sagebrush seedlings and broom snakeweed increased in C-S sites during the second and third years after treatment. In addition, perennial forb cover increased for C-S sites, while perennial grass biomass increased for non C-S sites. Our results emphasize that broad variability in plant community responses to sagebrush reduction and seeding is possible within the same ecological site classification and that legacy effects due to the combination of past cultivation and seeding should be considered when planning restoration projects, including the consideration that seeding may not always be necessary on C-S sites.

Mechanical weed control in organic winter wheat

Three field experiments were carried out in organic winter wheat in three consecutive years (exp. 1, 2005-06; exp. 2, 2006-07; exp. 3, 2007-08) in central Italy (42°57' N - 12°22' E, 165 m a.s.l.) in order to evaluate the efficacy against weeds and the effects on winter wheat of two main mechanical weed control strategies: 1) spring tine harrowing used at three different application times (1 passage at T1; 2 passages at the time T1; 1 passage at T1 followed by 1 passage at T1 + 14 days) in the crop sowed at narrow (traditional) row spacing (0.15 m) and 2) split-hoeing and finger-weeder, alone and combined at T1, in the crop sowed at wider row spacing (0.30 m). At the time T1 winter wheat was at tillering and weeds were at the cotyledons-2 true leaves growth stage. The experimental design was a split-plot with four replicates. Six weeks after mechanical treatments, weed ground cover (%) was rated visually using the Braun–Blanquet cover-abundance scale; weeds on three squares (0.6 x 0.5 m each one) per plot were collected, counted, weighed, dried in oven at 105 °C to determine weed density and weed above-ground dry biomass. At harvest, wheat ears density, grain yield, weight of 1000 seeds and hectolitre weight were recorded. Total weed flora was quite different in the three experiments. The main weed species were: <em>Polygonum aviculare</em> L. (exp. 1 and 2), <em>Fallopia convolvulus</em> (L.) Á. Löve (exp. 1 and 3), <em>Stachys annua</em> (L.) L. (exp. 1), <em>Anagallis arvensis</em> L. (exp. 2), <em>Papaver rhoeas</em> L. (exp.3), <em>Veronica hederifolia</em> L. (exp. 3). In the winter wheat sowed at narrow rows, 2 passages with spring-tine harrowing at the same time seems to be the best option in order to reconcile a good efficacy with the feasibility of treatment. In wider rows spacing the best weed control was obtained by splithoeing alone or combined with finger-weeder. The grain yield, on average 10% higher in narrow rows, the lower costs and the good selectivity of spring-tine harrowing treatments seems to suggest the adoption of narrow rows spacing in wheat in organic and low-input farming systems.

EFFECT OF SEASONAL TILLAGE ON SOME SOIL PROPERTIES, ENERGY PARAMETERS AND PRODUCTIVITY UNDER RECLAIMED SOIL

This study was focusing on energy parameters for tillage conditions of New El Salhia region, where dryland conditions were occurred. Soil texture was sandy loam. The methodology used in the calculation of consumed energy was divided into inputs and outputs to identify the energy ratio. Data from field experiment were used to determine some soil physical properties, energy indices and yield of wheat and corn as affected by tillage treatments. Tillage treatments included conventional system (chiselhing twice and harrowing), Minimum tillage (chiselling) and another minimum tillage system (harrowing). The soil bulk density and moisture content was determined for two depth until 30 cm. From the above mentioned it can be concluded that the minimum tillage using chisel plow might be necessary to conserve the moisture content and improve soil structure which consequently gave profitable yield from the energy point of view. The results showed that the conventional tillage treatments had the highest grain and biomass yield while harrowing treatments had the lowest values. The conventional tillage treatments gave the most net energy gain of (52.34 and 163.85 GJ) meanwhile the harrowing treatments gave the least ones (47.46 and 156.61 GJ) for wheat and corn respectively. The latter results mean that conventional tillage treatments were recommended for dryland farming of wheat and corn in El Salhia region. These results also will be helpful in developing a comprehensive database on the energy parameters of tillage implements for Egyptian agricultural machinery management.

Effect of physical sediments reworking on hydrocarbon degradation and bacterial community structure in marine coastal sediments.

The present study aimed to examine whether the physical reworking of sediments by harrowing would be suitable for favouring the hydrocarbon degradation in coastal marine sediments. Mudflat sediments were maintained in mesocosms under conditions as closer as possible to those prevailing in natural environments with tidal cycles. Sediments were contaminated with Ural blend crude oil, and in half of them, harrowing treatment was applied in order to mimic physical reworking of surface sediments. Hydrocarbon distribution within the sediment and its removal was followed during 286 days. The harrowing treatment allowed hydrocarbon compounds to penetrate the first 6 cm of the sediments, and biodegradation indexes (such as n-C18/phytane) indicated that biodegradation started 90 days before that observed in untreated control mesocosms. However, the harrowing treatment had a severe impact on benthic organisms reducing drastically the macrofaunal abundance and diversity. In the harrowing-treated mesocosms, the bacterial abundance, determined by 16S rRNA gene Q-PCR, was slightly increased; and terminal restriction fragment length polymorphism (T-RFLP) analyses of 16S rRNA genes showed distinct and specific bacterial community structure. Co-occurrence network and canonical correspondence analyses (CCA) based on T-RFLP data indicated the main correlations between bacterial operational taxonomic units (OTUs) as well as the associations between OTUs and hydrocarbon compound contents further supported by clustered correlation (ClusCor) analysis. The analyses highlighted the OTUs constituting the network structural bases involved in hydrocarbon degradation. Negative correlations indicated the possible shifts in bacterial communities that occurred during the ecological succession.

Effects of Mechanical Weed Control in Barley–Pea Mixture on Colonization of Barley Grain by Fungi, Part 1

The study aimed at being a mycological evaluation of spring barley grain harvested from the barley-pea intercrop, on which different methods of weed control had been used. The field experiment was carried out during 2010-12 and it was conducted using randomized block design in four replicates. Weed control was mechanical (spring-tine harrow treatment of variable intensity) and chemical (herbicide Chwastox Extra 300 SL – 3L per ha). Fungal colonization tests were carried out on disinfected and non-disinfected grains. The research has shown statistically significant differences in the total number of fungi isolated from disinfected and non-disinfected grains in particular years of study, between the objects, and in some cases between the study years. The fungus most frequently isolated from all variants of the experiment was Alternaria alternata. Penicillium chrysogenum was isolated only from non-disinfected grains. Presented results show that mechanical weed control treatments of appropriately adjusted intensity do not increase fungal colonization of barley grains in mixed culture with peas, as compared to the herbicidal control. The best variant of mechanical weed control for the cereal-legume mixture in terms of mycological quality of barley grain was one passage of spring-tine harrow at full tillering stage of barley. Mechanical weed control may be an alternative to herbicides in weed control in cereal-legume mixtures and may be particularly important for organic and integrated farming.

Effect of mechanical soil management through subsoiling and preparatory tillage on growth and nutrients uptake of sugarcane (Saccharum complex hybrid) plant and ratoon crop

A field experiment was conducted during 2008-2010 at G B Pant University of Agriculture and Technology, Pantnagar to study the response of sugarcane plant and ratoon crops to subsoiling and preparatory tillage. The experiment consisting of five subsoiling treatments in plant crop (No subsoiling, subsoiling at 1.0 m, subsoiling at 1.5 m, cross- subsoiling at 1.0 m and cross-subsoiling at 1.5 m distance) and three preparatory tillage practices (two harrowing, four harrowing and one rotavator) was laid out in strip plot design with three replications. The ratoon crop was managed mechanically with a newly developed Sugarcane Ratoon Manager in all the subsoiling treatments. The root and shoot growth, nutrients uptake, and yield of plant and ratoon crops increased with the intensity of subsoiling. The most intense subsoiling, i.e. cross-subsoiling at 1.0 m in plant crop resulted significantly more root biomass (70.1 g/ m3), shoot dry matter (40.9 tonnes/ha), nutrient uptake (220.9 kg N, 26.6 kg P and 307.6 kg K/ha), cane weight (883.8 g), millable canes (100.2 thousand/ha) and cane yield (75.8 tonnes/ha). Subsoiling practices coupled with mechanized management of ratoon exhibited significant improvement in root biomass (73.6 %), shoot dry matter (31.7 %), NPK uptake (29.3, 34.9 and 34.3 %, respectively), cane weight (13.6%), millable canes (21.9%) and cane yield (26.6%) over manual operations (control). All the preparatory tillage practices were at par with respect to the parameters studied, however, root biomass increased significantly with increase in number of tillage practices being maximum in four harrowing treatment.

Soil preparation and forage sowing time for crop-livestock integration in corn culture

This work was carried out during the 2008/2009 crop season, in an Oxisol. It was used a split-plot arrangement design, with each plot corresponding to a different soil preparation system and each split-plot corresponding to a different sowing time of the forage Brachiaria brizantha Stapf. The soil preparation systems were: heavy harrowing (HH), disk plough (DP), chisel plough (CP) and no-till (NT), and the forage sowing times were: 0, 8, 16 and 25 days after sowing (DAS) of corn, arranged in 16 treatments with 3 replicates. The productive and vegetative characteristics of the corn were evaluated. Soil preparations have influenced plant height and the first ear height, with the highest value found for the heavy harrow treatment. Forage sowing time had no influence on vegetative characteristics of the corn and productive characteristics were not influenced by the soil preparations. The forage sowing time had influence on corn productivity, causing decrease in competition with corn forage from 5 DAS. The productivity was highly correlated with the number of grains per ear.

The impact of different tillage systems and nutrient levels on the biomass and Brix values of sweet sorghum (Sorghum bicolor L. Moench)

The biomass and Brix content of sweet sorghum was investigated in 2009 and 2010 to determine the most suitable tillage and fertilization treatments. The experiment was carried out at the Biomass Utilization and Crop Production Demonstration Centre of Szent Istvan University. Both humus content and nitrogen (N) supply of the topsoil was insufficient. In 2009, which was a typical drought year, the yields ranged from 12.14 t/ha (direct drilling) to 56.11 t/ha (ploughing). There were significant differences between the tilled and non-tilled plots. In 2010 as in 2009, the highest yield of 63.52 t/ha was measured in case of ploughing, however cultivating and disk harrowing treatments showed similar biomass results. This study indicates that fertilizers had a significant effect on yields, as in both years highest biomass was obtained at 100 kg ha-1nitrogen rate. The highest Brix values were measured in 2009 (18.21%) and in 2010 (9.01%) in case of cultivation treatments. In the examination years, direct drilling showed the lowest results for biomass and also regarding Brix values. The results demonstrate that the fertilisation and suitable tillage is very important in the cultivation of sweet sorghum. Key words: Sweet sorghum (Sorghum bicolor), tillage, biomass, Brix.

Solute Diffusivity in Undisturbed Soil: Effects of Soil Water Content and Matric Potential

Solute diffusivity in soil plays a major role in many important processes with relation to plant growth and environmental issues. Soil solute diffusivity is affected by the volumetric water content as well as the morphological characteristics of water‐filled pores. The solute diffusivity in intact soil samples from two different tillage treatments (soil from below the depth of a harrow treatment and soil from within a moldboard plowed plow layer) was estimated based on concentration profiles using a newly developed method. The method makes use of multiple tracers (two sets of counterdiffusing tracers) for a better determination of the diffusivity. The diffusivity was higher in the below‐till soil than the plowed soil at the same soil water matric potential due to higher water content but also due to higher continuity and lower tortuosity of the soil pores. We measured identical solute diffusivities independent of the tracer set used. We analyzed the whole data set using Archie's law and found a linear relation between Archie's exponent and the logarithm of the soil water matric suction in centimeters of water (pF). An analysis of seven data sets from the literature showed that this was a general trend for soils with moderate to low clay contents.

Effect of four different tillage practices on maize performance under rainfed conditions

An experiment was conducted on Ferric Acrisol under rainfed conditions during the 2010 minor crop growing season in Kumasi, Ghana to determine the effect of different tillage practices on Akposoe maize (Zea mays .L) variety performance. The experiment was arranged in a randomised complete block design with four treatments namely disc ploughing only, disc ploughing followed by disc harrowing, disc harrowing only and No Tillage. Each treatment was replicated three times. At ten weeks after planting, the disc harrowing only plots produced the tallest plant, biggest stem girth, highest number of leaves per plant, and highest leaf area index. On the other hand the No Tillage plots presented the shortest plant, smallest stem girth, lowest number of leaves per plant, and smallest leaf area index. At harvest, the longest root, highest dry matter yield and highest fresh cob weight were obtained from the disc harrowing only plots while the shortest root, lowest dry matter yield, lowest fresh cob weight, lowest dry cob weight, and smallest 1000-seed weight were located in the No Tillage plots. The disc ploughing followed by disc harrowing treatment produced the highest dry cob weight and highest 1000-seed weight. There was no significant difference in Akposoe maize plant growth, dry matter yield and yield components between the disc harrowing only and the disc ploughing followed by disc harrowing treatments. Thus, considering the soil and weather conditions of the experiment, the optimum tillage practice for producing Akposoe maize variety is disc harrowing only.

Effect of four different tillage practices on soil physical properties under cowpea

Cowpea (Vigna unguiculata [L.] Walp) is grown by resource poor farmers in Ghana using different tillage practices. Most of these farmers perform tillage operations without being aware of the effect of these operations on soil physical properties and crop responses. A field study was conducted during the 2009 and 2010 major crop growing seasons under rainfed conditions on sandy loam soil (Ferric Acrisol) to compare the effect of different tillage practices on some selected soil physical properties under Asontem cowpea variety. The experiment was arranged in a randomized complete block design with three replications. The treatments consisted of disc ploughing only, disc ploughing followed by disc harrowing, disc harrowing only and no tillage. Compared with the other treatments, the disc ploughing followed by disc harrowing treatment gave the most favourable soil conditions (i.e. lowest soil penetration resistance, lowest dry bulk density, highest soil moisture content, and highest total porosity). The no tillage plots produced the most unfavourable soil conditions (i.e. highest soil penetration resistance, highest dry bulk density, lowest soil moisture content, and lowest total porosity). Therefore, under the soil and weather conditions of the experiment, the best tillage practice identified for Asontem cowpea production is disc ploughing followed by disc harrowing.

English

In the arid and semi arid region of Iran, conventional tillage is mainly used(Moldboard plowing followed by two disc harrowing) for wheat production. Such a tillage system requires a high energy input and may also cause water loss and long-term soil physical degradation. This field study was conducted under dry conditions to determine whether or not the reduced tillage systems altered the bulk density and soil moisture content. Thus, five tillage treatments (T1-moldboard plow + disc harrow as the conventional method, T2- chisel plow + disc harrow, T3- moldboard plow without inversion page + disk harrow, T4- power harrow, and T5- sweep plow + disk harrow) were studied during the three year period (2004 to 2007) in soils with silty clay loam texture. Soil moisture in four depths (0-10, 10-20, 20-30 and 30-40 cm) was measured at the flowering and grain filling stages. Generally, the lowest soil bulk density was obtained by T1 treatment. There were significant differences among tillage methods for soil moisture at the flowering stage (P < 0.05) and T1 treatment had the highest value. There were no significant differences among soil tillage methods for soil moisture at the grain filling stage. Overall, chisel plow + disc harrow treatment was recognized as the best tillage method due to the remains of stored soils at the grain filling stage.   Key words: Bulk density, dry conditions, soil moisture, tillage.

Application of biochemical degradation indices to the microbial decomposition of maize leaves and wheat straw in soils under different tillage systems

In a long-term tillage experiment comparing mouldboard plough and rotary harrow since 1967, litterbags with green maize residues and wheat straw were buried, recovered from soil and analysed for biochemical degradation indices. Our objective was to investigate whether lignin units and neutral and amino sugars give information on microbial degradation after burial periods of 6 and 12 months at two different depths (0–5 and 15–20 cm). Tillage and burial depth had no effects on the content and composition of lignin. In contrast, the extended burial period resulted in higher acid/aldehyde ratios of vanillyl units, due to increasing microbial oxidation, and in higher ratios of cinnamyl/vanillyl units, due to the higher resistance of vanillyl units against microbial degradation. The contents of mannose, bacterial muramic acid, and fungal glucosamine were significantly higher in the plough than in the harrow treatment, due to a higher microbial colonisation. For the same reason, the extended burial period led to significant increases in the contents of mannose, glucosamine, muramic acid, and galactosamine as well as in the GM/AX ((galactose + mannose)/(arabinose + xylose)) ratio. The decline in the fungal C/bacterial C ratio indicated that bacterial colonisation of litter followed fungal colonisation with delay. A greater burial depth led to a lower microbial colonisation and consequently had contrasting effects to those of a longer burial period. Treatment effects on maize residues and wheat straw were generally similar, despite the strong differences in composition. The combination of litterbags and biochemical degradation indices gave further evidence that lower tillage intensity reduces microbial turnover and decomposition activity.

Influence of tillage on degradation kinetics using the litterbag method

A litterbag experiment was carried out in a tillage trial near Göttingen, Germany, comparing the long-term effects of mouldboard plough and rotary harrow on organic matter dynamics. The aim was to investigate the C loss and N balances in litterbags filled with N-poor, lignin-rich wheat straw and N-rich, lignin-poor maize residues, simulating the properties of green manures. The litterbags were buried at 0–5 and 15–20 cm depth and one fourth of them were removed after 3, 6, 9, and 12 months, respectively. The C loss rates, corrected for soil input into the litterbags, were significantly affected by tillage and bury depth and showed significant litter material × bury depth interactions. These were caused by generally higher C loss rates in the plough treatment, especially at 15–20 cm depth, and in the litterbags with maize residues. More soil was transferred to the litterbags in the plough treatment than in the rotary harrow treatment and more soil was found in the litterbags at 0–5 cm than at 15–20 cm depth. A smaller amount of stable aggregates in the surrounding soil is the most plausible explanation for this higher soil input. Nearly 40% of maize residue C was lost in the first three months from November to February, followed by a further exponentially decreasing loss of 40% over the next 9 months. Almost no wheat straw C was lost in the first three months, followed by a nearly linear loss of 60% over the next 9 months. The N balance showed strong N losses in the litterbags with maize residues for all exposure periods. In contrast, the N balance was always positive for wheat straw. The N balances, corrected for soil input, revealed significant bury depth effects and exposure period × bury depth interactions, but no significant tillage effects.

Influence of mouldboard plough and rotary harrow tillage on microbial biomass and nutrient stocks in two long-term experiments on loess derived Luvisols

The nutrient-specific effects of tillage on microbial activity (basal respiration), microbial biomass (C, N, P, S) indices and the fungal cell-membrane component ergosterol were examined in two long-term experiments on loess derived Luvisols. A mouldboard plough (30 cm tillage depth) treatment was compared with a rotary harrow (8 cm tillage depth) treatment over a period of approximately 40 years. The rotary harrow treatment led to a significant 8% increase in the mean stocks of soil organic C, 6% of total N and 4% of total P at 0–30 cm depth compared with the plough treatment, but had no main effect on the stocks of total S. The tillage effects were identical at both sites, but the differences between the sites of the two experiments were usually stronger than those between the two tillage treatments. The rotary harrow treatment led to a significant increase in the mean stocks of microbial biomass C (+18%), N (+25%), and P (+32%) and to a significant decrease in the stocks of ergosterol (−26%) at 0–30 cm depth, but had no main effect on the stocks of microbial biomass S or on the mean basal respiration rate. The mean microbial biomass C/N (6.4) and C/P (25) ratios were not affected by the tillage treatments. In contrast, the microbial biomass C/S ratio was significantly increased from 34 to 43 and the ergosterol-to-microbial biomass C ratio significantly decreased from 0.20% to 0.13% in the rotary harrow in comparison with the plough treatment. The microbial biomass C-to-soil organic C ratio varied around 2.1% in the plough treatment and declined from 2.6% at 0–10 cm depth to 2.0 at 20–30 cm depth in the rotary harrow treatment. The metabolic quotient qCO 2 revealed exactly the inverse relationships with depth and treatment to the microbial biomass C-to-soil organic C ratio. Rotary harrow management caused a reduction in the microbial turnover in combination with an improved microbial substrate use efficiency and a lower contribution of saprotrophic fungi to the soil microbial community. This contrasts the view reported elsewhere and points to the need for more information on tillage-induced shifts within the fungal community in arable soils.