Heavy Disc Harrow Research Articles

Effect of Cultivation Methods on Structural Elements and Grain Yield of Winter Wheat

The main part of human food is wheat, and the main task facing agriculture is to obtain high-quality grain from a single field in the current conditions. Yield varies depending on the variety, soil and climatic conditions and the cultivation used. Taking these into account, our research studied the structural elements and yield of winter wheat against the background of predecessors, soil cultivation and nutritional conditions in dry rainfed conditions, and the 3-year average result is also given in the article. For the first time in the region, optimal nutritional conditions and soil cultivation were studied by minimizing soil cultivation based on its predecessor and replacing some mineral fertilizers with organic fertilizers in order to obtain both high and quality grain products through efficient use of land. The studies were conducted in a 3-factor (2×3×3) field experiment in a short-rotation cropping turnover (peas, wheat, wheat) located in the Jalilabad Regional Experimental Station in the dry rainfed conditions of South Mugan. The object of research is the fertile 95 durum wheat varieties. Structural analysis of the yields was carried out on samples of sheaves taken from 1 m2(4×0.83×2×0.15 m) in two rows of 83 cm in 4 different replicate locations. After the shave samples were taken, the yield of the grain was determined according to the cultivation options by harvesting directly in each field with a combine. From the 3-year average results of the study for 2019-2021, it was found that the structural indicators of the variety and grain yield were dynamic depending on the cultivation option. However, the highest results were obtained after the pea predecessor against the background of N60P60+10 tons of manure applied with a heavy disc harrow at a depth of 10-12 cm in the twice disc option.

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.

Effect of main cultivation methods in dry rainfed conditions on the amount of weed under winter wheat

Relevance. Against the background of predecessors, soil cultivation and nutritional conditions, weeding of the area under Barakatli 95 durum wheat variety was studied and the results obtained are given in the article. Thus, high weeds in the field reduce the quantity and quality of crops. One of the main factors preventing this is the application of proper cultivation methods appropriate to the region. This is one of the most important and urgent issues in agriculture.Methodology. The research was conducted in a 3-factor (2×3×3) field experiment in a short-rotation crop rotation (pea-wheat-wheat) located at the Jalilabad Regional Experimental Station in the rainfed conditions of South Mugan. The amount of weeds in the field was studied in the first decade of March and April by counting weeds per 1 m2 from different parts of the field according to the options.Results. The results of the 3-year study (average for 2019–2021) showed that the effect of predecessors, soil cultivation and nutritional conditions on the amount of weeds under winter wheat was different. Among the cultivation options, relatively high weeding soil was obtained with a heavy disc harrow at a depth of 10–12 cm in the form of 1 disc, and against the background of feeding conditions, N60P60 + 10 tons of manure on all three cultivations, and the least weeding was observed in the variant where N90P60K45 fertilizer norm was applied in 2 discs at a depth of 10–12 cm with a heavy disk trowel after the pea predecessor.

Mudanças no estoque de carbono orgânico e produtividade de culturas em solo arenoso tropical sob sistemas de produção de grãos-algodão em sequeiro na Bahia, Brasil

ABSTRACT Most studies about soil organic carbon stock changes in the Cerrado (Brazilian Savanna) biome are either related to field data collected in clayey Ferralsols or different land uses, as if they were in equilibrium. This study aimed to evaluate the effect of tillage systems and crop sequences on the soil organic carbon stock and crop yield, in a sandy Ferralsol from Bahia, Brazil. The experimental design was randomized blocks, with four replicates. Soil samples were collected after fve years of cotton, soybean and maize monocropping under heavy disk harrow and leveling harrow (conventional tillage), and of crop rotation of cotton, soybean and maize with green manure or cover crop (no-tillage). Additional samples were collected from a non-cultivated site (Neotropical Savanna, Cerrado sensu stricto). Soil conservation practices such as no-tillage and crop rotation with cover crop and green manure favored the soil organic carbon stock at the 0-40 cm layer, with the highest values reaching 36.03 Mg ha−1. The accrued soil carbon stock under conventional tillage and monoculture of cotton, maize and soybean was lower than under no-tillage, which ranged from 30.9 to 54.9 %, with the soil organic carbon stock increasing at the annual rate of 2.36 Mg ha−1 during fve years. The no-tillage, with the soybean-maize-cotton rotation, in combination with cover crop and green manure, increased the cotton and soybean yields, with a simultaneous organic carbon accumulation in the sandy soil.

Uzun Süreli Korumalı ve Geleneksel Toprak İşleme Sistemlerinin Beta Glikosidaz Enzim Aktivitesi ve Potansiyel Mineralize Olabilir Azot Üzerine Etkisi

Bu çalışmada, dokuz yıl süre ile uygulanan iki geleneksel, üç azaltılmış ve sıfır toprak işleme yöntemlerinin GEA ve PMN üzerine etkileri belirlenmiş ve karşılaştırılmıştır. Tesadüf blokları şeklinde 2006 yılında başlatılan çalışmada, 6 farklı toprak işleme sistemi için 3 tekerrürlü ve toplam 18 adet parsel yer almaktadır. Bunlara ilaveten, Araştırma alanında, anızlı geleneksel toprak işleme (Gİ–1), anızları yakılmış geleneksel toprak işleme (Gİ–2), ağır diskli tırmıklı azaltılmış toprak işleme (ATİ–1), rototillerli azaltılmış toprak işleme (ATİ–2), ağır diskli tırmıklı azaltılmış sıfır toprak işleme (ASTİ) ve doğrudan ekimli sıfır toprak işleme (STİ) şeklinde altı farklı toprak işleme yöntemi uygulanmaktadır. Ürün rotasyonu olarak bugüne kadar kışlık bitki olarak her yıl buğday ve yazlık olarak (ikinci ürün) buğday hasadını takiben sırasıyla bir yıl mısır ve bir yıl soya yetiştirilmiştir. Toprak işleme sistemlerinin farklılaşması GEA ve PMN konsantrasyonunun önemli düzeyde farklılaşmasına neden olmuştur. Toprak işleme yoğunluğunun azalması ile birlikte önemli düzeyde artış gösteren GEA konsantrasyonu 44,68 mg PNP kg-1 sa-1 (Gİ-2) ile 207,66 mg PNP kg-1 sa-1 (STİ) arasında değişmiştir. Ancak GEA‘da belirlenen trend PMN‘de tespit edilememiştir. Sıfır toprak işleme altındaki topraklarda PMN konsantrasyonu önemli düzeyde yüksek olmakla birlikte ATİ-1 ile PMN konsantrasyonu bakımından aynı grupta yer almıştır. İşlenmemiş topraklarda PMN konsantrasyonunun daha yüksek olmasının muhtemelen toprak strüktürünün parçalanmaması ile ilişkili olduğu düşünülmektedir. Araştırma sonuçları, azaltılmış ve sıfır toprak işleme sistemlerinin bölgede toprağın kalitesinin arttırılması adına son derece gerekli olduğunu ortaya koymaktadır.

Soil compaction on traffic lane due to soil tillage and sugarcane mechanical harvesting operations

Mechanical sugarcane harvesting increases soil compaction due to the intense traffic of agricultural machinery, reducing longevity of sugarcane crops. In order to mitigate the harmful effects caused by agricultural traffic on the soil structure in sugarcane fields, this study evaluated impacts of mechanical sugarcane harvesting on traffic lane under two soil tillage systems based on load bearing capacity models. The experiment was carried out in the region of Piracicaba, state of Sao Paulo, Brazil, on a Rhodic Nitisol, under conventional tillage (CT) and deep strip-tillage (DST). For CT soil tillage was applied to the entire area with a heavy disk harrow, at operating depths from 0.20 to 0.30 m followed by a leveling harrow at a depth of 0.15 m. For DST, soil tillage was performed in part of the area at a depth of 0.80 m, forming strip beds for sugarcane planting, while the traffic lanes were not disturbed. Undisturbed soil samples from traffic lanes were used in the uniaxial compression test to quantify preconsolidation pressure and to model the soil load bearing capacity. The surface layer (0.00-0.10 m) was most susceptible to compaction, regardless of the tillage system (CT or DST) used. In the DST, the traffic lane maintained the previous soil stress history and presented higher load bearing capacity (LBC) than the traffic lane in the CT. As in CT the soil was tilled, the stress history was discontinued. This larger LBC in DTS minimized the impacts of the sugarcane harvest. Under CT, additional soil compaction due to mechanical sugarcane harvesting in the traffic lane was observed after the second sugarcane harvest. There was a reduction in load bearing capacity from 165 kPa to 68 kPa under CT and from 230 kPa to 108 kPa under DST, from the first to the second harvest at surface layer. Water content at mechanical harvesting was the most relevant factor to maximize impacts on the soil structure in traffic lanes, for both tillage systems.

SOIL FERTILITY AND POTATO PRODUCTIVITY UNDER DIFFERENT COMPOSTING TECHNOLOGIES

The article presents the results of studies, describing the effect of various methods of peat-and-manure compost embedding on the fertility of sod-podzolic light loamy soil. When peat-and- manure compost is smothered with a longline plow PYa-3-35 at a depth of 25-27 cm compared to embedding with an ordi-nary plow by 20-22 cm and a heavy disc harrow by 15-17 cm, soil factors for growth and development of plants, edaphobiotics vital activity: acidity of soil solution, content of exchangeable potassium, mobile phosphorus and nitrate nitrogen, sum of the absorbed bases, base absorption capacity, humus content, ratio of humic acids to fulvic acids and carbon to nitrogen in humus. At the plot of a deep compost em-bedding in the 0-30-cm layer, the decomposition of linen cloth was more intense due to the participation of aerobic and anaerobic bacteria in this process. In the profile of 0-20 cm, under aerobic conditions, mineralization of linen cloth occurred more quickly under usual and disk embedding, but in the layer of 20-30 cm under deep processing with a lack of oxygen, a slowdown in decomposition of organic matter was established. In this layer, the disintegration of linen cloth was 1.5-2 times slower than in the rest of the compost, which contributed to a longer preservation of embedded organic matter. The presence of a sufficient amount of organic matter in the lower soil layer promoted the intensive reproduction of a larg-er macrofauna of soil - earthworms. On this plot, the number of earthworms in the lower layer was great-er compared not only with the control variant, but with other fertilized plots. Owing to the more active formation of humic substance in the soil with the sealing of the peat compost at 25-27 cm with a two-tier plow, the content of waterproof aggregates was much higher, thereby significantly reducing the density of its build-up during vegetation. The most optimal soil factors, provided by long-combined processing, al-lowed obtaining a higher productivity of potato tubers and with better indicators of their quality.

Understanding the relations between soil organic matter fractions and N2O emissions in a long‐term integrated crop–livestock system

AbstractThe nitrous oxide (N2O) emissions in agricultural systems are influenced by edaphoclimatic conditions, and the availability of soil organic matter (SOM) is a key factor. The objective of this study was to evaluate the accumulation of labile and stable SOM fractions and possible relations with N2O emissions using a multivariate approach in a 24‐year integrated crop–livestock experiment in the Cerrado region. The management systems consisted of: continuous cropping under no tillage (CC‐NT), continuous cropping under annual heavy disc harrow (CC‐CT), an integrated crop–livestock system under no tillage (CLS‐NT) and an adjacent area of native Cerrado as reference. The cumulative N2O emissions were quantified over a period of 146 days throughout the cultivation of sorghum (Sorghum bicolor (L.) Moench). Labile and stable soil carbon (C) fractions and C contents in classes of aggregates (macroaggregates >0.250 mm and microaggregates <0.250 mm) were determined. The cumulative N2O emissions were larger in the CC‐CT system, intermediate in the CC‐NT and CLS‐NT systems, and smaller in the Cerrado. The decomposition of crop residues during the crop succession (first and second crop seasons) and the presence of a grass forage (with grazing and not grazed) in both systems (CLS‐NT and CC‐NT, respectively) explain the differences in N2O fluxes between the land uses. Smaller cumulative N2O emissions were observed in the integrated system (CLS‐NT), which could be attributed to the greatest increase in soil C in its most stable SOM fractions (fulvic acid) and occlusion in microaggregates. This confirms the hypothesis that the accumulation of C in the most stable SOM fractions of the soil, unavailable to the microbiota, results in smaller N2O emissions. Principal component analysis also revealed that aggregation is a key attribute that correlates with soil N2O emissions. Thus, conservation systems such as CLS‐NT had larger average diameter of aggregates and the smallest N2O emissions among the agroecosystems.Highlights Relations between SOM fractions and N2O emissions were studied in integrated systems The accumulation of stabilized C fractions reduces N2O emissions Soil structure (aggregation) and SOM stability partially explain N2O fluxes Integrated crop–livestock promotes better soil conditions, reducing N2O emissions

Combined tillage machine for protective afforestation

The main preparation of the soil for protective forest plantations on agricultural fields and tractor pass of gully slopes with the steepness up to 12° in the regions of insufficient and unstable moistening is characterized by a low degree of crumbling of the soil layer, when using plows , high energy and material intensity, multi-operation (plowing, deep loosening, destruction of soil blocks). Plowing across slopes with a steepness of more than 4-6° is made only under a slope, i.e. each working stroke is idle, and this reduces the productivity. The design of a combined tillage machine is offered, it is the hinged ripper plow PRN-40, replacing plows of general purpose PLN-4-35 and the plant PPN-40, the hinged ripper RN-80, the cultivator KRT-3 or the heavy disc harrow BDNT-3, which produces a deep layered cultivation of the soil (plowing to a depth of 25...27 cm and loosening the subsoil layer by 25...40 cm) and active circulation of the soil layer both downward and upward along the slope to 12...15 °; excluding additional treatment for the purpose of destroying soil blocks. In the plow-ripper PRN-40, the working parts of the passive (the body with the shortened blade and the deep cutter) and the active (rotary ripper) operation are used. They use power of the tractor engine through its propulsors and PTO separating the plowing process into separate operations performed at different rates of impact and subject to a layer of various non-energy-intensive types of deformation.

Tillage Effects on Some Soil Physical Properties in a Semi- Arid Mediterranean Region of Turkey

Throughout the world, degradation of soil has become an environmental problem which limits the sustainability of agriculture and decreases soil productivity. The main reason of degradation is either over cultivation or the utilization of improper tillage methods. Therefore, tillage practices play a crucial role in chemical, biological and physical properties of agricultural soils. This role was determined often by using indicators of soil quality such as bulk density, aggregate stability, plant available water, organic carbon content, soil compaction and other properties. The aim of this field study was to examine the effects of different tillage systems on some soil characteristics in the semi-arid Mediterranean coastal plain of Turkey. In the research, the following six different tillage systems were tested: conventional tillage with residue incorporated (CTR), conventional tillage with residue burned (CTB), minimum tillage with heavy tandem disc harrow (MTD), minimum tillage with rotary tiller (MTR), minimum tillage with heavy tandem disc harrow for the first crop + no-tillage for the second crop (MNT), and no tillage (NT). The experiment was initiated with summer soybean, followed by winter wheat and summer corn and ended with winter wheat production. Bulk density, aggregate stability, organic matter content and soil penetration resistance were evaluated as indicators of soil quality in this study. Conservation tillage systems (MT and NT) improved organic carbon content and aggregate stability of the soil. The different tillage systems showed a significant effect with respect to the amount of organic matter and aggregate stability in the soil. Organic matter values were lower (49-60%) under CT practices and residue burning accelerated the loss of organic carbon content. The highest aggregate stability values were found for NT (over 38%). Penetration resistance and bulk density of the tilled soils (CT and MT) were lower than in no-tillage plots (MNT and NT), bulk density was 1.26-1.32 g/cm3 in CT at all soil depths. The trials showed that, conservation tillage practices (MT and NT) can provide better soil characteristic values than conventional practices in the semi-arid soils of the Mediterranean coastal plain.

Nitrous oxide fluxes in a Brazilian clayey oxisol after 24 years of integrated crop-livestock management

Integrated crop-livestock systems have been recently adopted in several agricultural regions of Brazil. Studies involving the effect of adopting integrated systems on greenhouse gas mitigation are essential for choosing sustainable agricultural systems. In this study, the emissions of nitrous oxide in a crop-livestock system (4-year crop/pasture rotation) compared with two continuous crop (CC) areas under conventional and no-tillage management were investigated. The treatments consisted of continuous cropping under no-tillage (CC-NT), continuous cropping with annual heavy disc harrow (CC-CT), an integrated crop-livestock system under no-tillage (CLS-NT) and native Cerrado as a reference. Considering the cumulative N2O emissions in a year, the CC-CT emitted 2.55 kg N-N2O ha−1, higher than the Cerrado, which emitted 0.55 kg N-N2O ha−1. All the agricultural systems emitted more N2O than the Cerrado, however, the two conservation systems CC-NT and CLS-NT had lower emissions than the CC-CT, and were responsible for 1.90 and 1.52 kg N-N2O ha−1, respectively. In the agroecosystems, the highest N2O fluxes were observed after fertilization and rainfall events. In the CC systems, N2O emissions were greater than in the integrated system during the sorghum/off-season period, but in the CC-CT emissions were greater than in CC-NT. During the soybean cycle no differences in emissions were observed between both CC systems, which surpassed that in CLS-NT that was occupied by Brachiaria pasture. The annual cumulative N2O emissions in CLS-NT were close to that observed in the Cerrado indicating this system to be an agricultural practice with potential to mitigate N2O emissions.

Long-term tillage and residue management effect on soil compaction and nitrate leaching in a Typic Haploxerert soil

A field experiment was conducted to compare the effects of long-term tillage and cropresidue management on some physical properties and nitrate leaching of a Typic Haploxerertsoil under winter wheat (Triticum vulgare L.)-soybean (Glycine max L.) double-croppingsystem. The tillage systems consisted of conventional tillage with stubble (CT1), conventionaltillage with stubbles burned (CT2), heavy disc harrow reduced tillage (RT1), rototiller reducedtillage (RT2), reduced tillage with heavy tandem disc harrow fallowed by no-tillage (RNT) andno-till (NT). Each tillage method applied at 480 m2 plot and replicated three times in randomlydistributed plots. In the experiment, organic matter content (OM), aggregate stability (AS),penetration resistance (PR), porosity, bulk density (BD) in 0-15 cm and 15-30 cm depth andnitrate concentrations at 90 cm depth were determined. Tillage practices significantly affectedthe measured properties at both soil depths. The BD and PR within the conservational managedplots were higher than under conventional managed plot. Whereas, OM content and AS weresignificantly greater under conservational managed plots, indicating improved soil quality.Soybean yield was not affected by tillage practices. The concentrations of NO3-N leached hadstrong variation within sampling dates and significantly different among treatments after thefirst and the third irrigation (P˂0.01). The highest average NO3-N (1440.8b±74.9 mg L-1) inleachate was measured in the CT2 plot while the lowest value (774.8a±56.5 mg L-1) wasobtained in the RT1 plot. The results of this study revealed that reduced tillage and no-tilltreatments could significantly improve soil physical quality and reduce NO3-N leaching ofTypic Haploxerert soil in the Cukurova Region

EFFECT OF SOIL TILLAGE AND PLANT RESIDUE ON SURFACE ROUGHNESS OF AN OXISOL UNDER SIMULATED RAIN

Surface roughness of the soil is formed by mechanical tillage and is also influenced by the kind and amount of plant residue, among other factors. Its persistence over time mainly depends on the fundamental characteristics of rain and soil type. However, few studies have been developed to evaluate these factors in Latossolos (Oxisols). In this study, we evaluated the effect of soil tillage and of amounts of plant residue on surface roughness of an Oxisol under simulated rain. Treatments consisted of the combination of the tillage systems of no-tillage (NT), conventional tillage (CT), and minimum tillage (MT) with rates of plant residue of 0, 1, and 2 Mg ha-1 of oats (Avena strigosa Schreb) and 0, 3, and 6 Mg ha-1 of maize (Zea mays L.). Seven simulated rains were applied on each experimental plot, with intensity of 60±2 mm h-1 and duration of 1 h at weekly intervals. The values of the random roughness index ranged from 2.94 to 17.71 mm in oats, and from 5.91 to 20.37 mm in maize, showing that CT and MT are effective in increasing soil surface roughness. It was seen that soil tillage operations carried out with the chisel plow and the leveling disk harrow are more effective in increasing soil roughness than those carried out with the heavy disk harrow and leveling disk harrow. The roughness index of the soil surface decreases exponentially with the increase in the rainfall volume applied under conditions of no tillage without soil cover, conventional tillage, and minimum tillage. The oat and maize crop residue present on the soil surface is effective in maintaining the roughness of the soil surface under no-tillage.

Bacterial Diversity Under Different Tillage and Crop Rotation Systems in an Oxisol of Southern Brazil

Microbial diversity can be used to assess the impact of agricultural practices on the long-term sustainability of cropping systems. The aim of this study was to investigate changes in soil bacterial diversity as a result of the impact of different soil tillage and crop rotation systems in an oxisol of southern Brazil. Bacterial diversity was examined in the 0- 10 cm layer in two field experiments by analyzing soil DNA using 16S rDNA-DGGE profiles. Experiment one consisted of a long-term 26-year trial with four soil tillage management systems: (1) no-tillage (NT), (2) disc plow (DP), (3) field cultivator (FC), and (4) heavy-disc harrow (DH), all under soybean (summer)/wheat (winter) crop succession. Experiment two consisted of a short-term 10-year trial with DP and NT and three crop rotations (CR) including grasses, legumes and green manures. Cluster analysis of the 16S rDNA sequences revealed that the main effect on clustering was attributed to differences in soil tillage management systems. The Shannon index confirmed greater bacterial diversity under NT, fol- lowed by the FC, DH and DP. Therefore, diversity decreased as tillage practices intensified. The evenness index demon- strated uniformity of the profiles of the bacterial communities, with dominance of a few communities, regardless of soil tillage and crop rotation. Different crop rotations had only minor effects on bacterial diversity, what could be related to a previous fallow period. The results suggest that bacterial diversity analyzed by DGGE may be useful as bioindicator of the changes caused by soil tillage.

Tillage Effect on Penetration Resistance, Bulk Density and Saturated Hydraulic Conductivity in a Clayey Soil

Effects of six tillage practices on saturated hydraulic conductivity (HC), soil bulk density (BD), and penetration resistance (PR) were evaluated for a clayey soil ( Typic Haploxererts) under semi-arid Mediterranean conditions in a three year study (2006-2009). The experiment was conducted on a randomized complete block design with three replicates. Treatments were : conventional tillage with residue incorporated (CTS), conventional tillage with residue burned (CTB), reduced tillage with heavy tandem disc harrow (RTD), reduced tillage with rotary tiller (RTR), reduced tillage with heavy tandem disc harrow for the first crop + no-tillage for the second crop (RNT), and no tillage (NT). The study was conducted in wheat- corn, wheat-soybean and wheat crop rotations. The tillage effects on HC, BD and PR were significant at soil depth of 0-30 cm. The hydraulic conductivity was higher in CTS, and followed by CTB, RTR, RTD, RNT and NT practices, respectively. The hydraulic conductivity values under NT in 2007 and 2008 were 20% and 30% lower at 0-30 cm depth compared with CTS, respectively. The conventional tillage treatments in the semi-arid conditions improved the HC by decreasing BD and PR of the clayey soil. The BD and PR values were higher under NT treatment than the tilled plots and increased with depth. The values of soil compaction indicators were significantly greater under no-tillage and reduced tillage as compared to those under conventional tillage in all soil depths studied.

Microbial biomass under various soil- and crop-management systems in short- and long-term experiments in Brazil

Management and cropping systems varying in soil mobilization rates and plant-residue inputs may have profound effects on the biological properties of soil. Therefore, the objective of this study was to quantify soil microbial biomass carbon and nitrogen (MB-C and MB-N)—by means of the fumigation-extraction method—under varied soil-management and crop-rotation/succession systems in southern Brazil, correlating the results with yields of soybean and maize crops. The microbial biomass and grain yields were examined at the 0–10 cm layer in four short- to long-term field experiments. Experiment 1 was a 26-year trial consisting of four soil-management systems: (1) no-tillage (NT), (2) conventional tillage [(CT) with disc plough], (3) field cultivator (FC) or (4) heavy-disc harrow (DH), each with a crop succession (CS) of soybean (summer) and wheat (winter). Experiment 2 was a 21-year trial consisting of one CS, soybean/wheat every year) and seven crop rotations (CRs) comprising soybean, maize, wheat and green manures (lupine, radish and black oat), under the NT system. Experiment 3 comprised a 14-year CT trial, and 4-year and 14-year NT trials, with both one CS and two CRs. Experiment 4, a 10-year trial consisted of CT and NT and three CRs. Analyses were performed during the summer and winter croppings. Differences in microbial parameters, as a function of crop succession and rotation, were not easily detected as they varied as a function of a complex combination of plant species and time of implementation of the experiment. In contrast, MB-C and MB-N values were consistently higher—up to more than 100%—under NT in comparison to CT and were associated with higher grain yields. Our results—from this wide range of experiments—suggest that MB-C and, particularly, MB-N are sensitive indicators of the effects of soil- and crop-management regimens.

Quantifying soil respiration in response to short-term tillage practices: a case study in southern Turkey

The study aimed at quantifying the rates of soil CO2 efflux under the influence of common tillage systems of moldboard plow (PT), chisel plow (CT), rotary tiller (RT), heavy disc harrow (DT), and no-tillage (NT) for 46 days in October and November in a field left fallow after wheat harvest located in southern Turkey. The NT and DT plots produced the lowest soil CO2 effluxes of 0.3 and 0.7 g m−2 h−1, respectively, relative to the other plots (P < 0.001). Following the highest rainfall amount of 87 mm on the tenth day after the tillage, soil CO2 efflux rates of all the plots peaked on the 12th day, with less influence on soil CO2 efflux in the NT plot than in the conventional tillage plots. Soil evaporation in NT (64 mmol m−2 s−1) was significantly lower than in the PT (85 mmol m−2 s−1) and RT (89 mmol m−2 s−1) tillage treatments (P < 0.01). The best multiple-regression model selected explained 46% of variation in soil respiration rates as a function of the tillage treatments, soil temperature, and soil evaporation (P < 0.001). The tillage systems of RT, PT, and CT led, on average, to 0.23, 0.22, and 0.18 g m−2 h−1 more soil CO2 efflux than the baseline of NT, respectively (P≤0.001).

Modeling organic carbon dynamics under no-tillage and plowed systems in tropical soils of Brazil using CQESTR

CQESTR simulates the effect of management practices on soil organic carbon (SOC) stocks. The beta version of the model had been calibrated and validated for temperate regions. Our objective was to evaluate the CQESTR model performance for simulating carbon dynamics as affected by tillage practices in two tropical soils (Ultisol and Oxisol) in southeastern and northeastern Brazil. In the southeast (20.75 S 42.81 W), tillage systems consisted of no tillage (NT); reduced tillage (RT) (one disc plow and one harrow leveling [RT1] or one heavy disc harrow and one harrow leveling [RT2]); and conventional tillage (CT) (two heavy disc harrows followed by one disc plow and two harrow levelings). In the northeast (7.55 S 45.23 W), tillage systems consisted of NT, RT (one chisel plow and one harrow leveling), and CT (one disk plow, two heavy disk harrowings, and two harrow levelings). CQESTR underestimated SOC at both sites, especially under NT systems, indicating that adjustments (e.g., the inclusion of clay mineralogy factor) are necessary for more accurate simulation of SOC in the tropics. In spite of this, measured and simulated values of SOC in the 0–20 cm depth were well correlated (southeast, R 2 = 0.94, p < 0.01; northeast, R 2 = 0.88, p < 0.05). With respect to initial conditions (native forest), CQESTR estimated a decrease in SOC stocks in plowed and no-tillage systems. In 2006, in the southeast, SOC stocks were 28.8, 23.7, 23.2, and 22.0 Mg ha −1 under NT, RT2, RT1, and CT, respectively; in the northeast, stocks were 36.0, 33.8, and 32.5 Mg ha −1 under NT, RT, and CT, respectively. The model estimated carbon emissions varying from 0.36 (NT) to 1.05 Mg ha −1 year −1 (CT) in the southeast and from 0.30 (NT) to 0.82 (CT) Mg ha −1 year −1 in the northeast. CQESTR prediction of SOC dynamics illustrates acceptable performance for the two tropical soils of Brazil.

Agregação de Latossolo Vermelho sob diferentes sistemas de preparo do solo, após um único cultivo com girassol

Avaliou-se, no presente trabalho, o efeito de um único cultivo de girassol na agregação de Latossolo Vermelho submetidos a diferentes sistemas de preparo, em número de quatro: grade aradora + grade niveladora (GA), grade niveladora (GN), semeadura direta na palha (SP) e plantio direto (PD), no outono-inverno; exceto no PD, foi passado o escarificador + grade niveladora na primavera-verão semeando-se, em seguida, a soja e, no outono-inverno o girassol. As avaliações dos agregados de solo foram feitas antes do plantio e após a colheita do girassol, em propriedades particulares em Cândido Mota e Pedrinhas Paulista, SP, cujo cultivo do girassol melhorou a agregação, independentemente do sistema de preparo utilizado.

Morfologia de agregados do solo avaliada por meio de análise de imagens

O uso intensivo do solo, aliado a condições inadequadas de manejo, concorre para a deterioração de suas propriedades físicas e isso se deve, principalmente, às modificações em sua estrutura. Uma vez que as mudanças estruturais influem diretamente na morfologia dos agregados, considera-se fundamental a procura de novos métodos de estudos macromorfológicos para permitir o acompanhamento das modificações dessa característica nos solos cultivados. Sendo assim, este trabalho teve por objetivo adaptar e testar um método digital de análise macromorfológica qualitativa de agregados, visando detectar modificações morfológicas causadas pela ação antrópica. Para tal estudo, foram escolhidos cinco sistemas de preparo do solo: plantio direto, escarificador, grade aradora, arado de discos e arado de aivecas. Realizou-se o estudo da forma e do tamanho das diferentes classes de agregados de um Latossolo Vermelho distrófico típico, em amostras coletadas em 1998, após a aquisição de imagens com o uso de um scanner (HP 6100C com capacidade de resolução ótica de 1.200 dpi) e o posterior processamento dessas imagens pelo programa de computador denominado UTHSCSA Image Tool. Este programa fornece índices sobre os agregados, tais como: arredondamento, compacidade e alongamento. O índice arredondamento é dependente da medida de perímetro (rugosidade externa) e os índices compacidade e alongamento são dependentes da medida do comprimento do maior eixo (arestas). De maneira geral, os sistemas de manejo utilizados por três anos consecutivos não promoveram diferenças morfológicas dos agregados do Latossolo Vermelho textura argilosa para as variáveis analisadas. A análise de imagens mostrou-se sensível à detecção de mudanças na morfologia dos agregados do solo, sendo bastante promissora como uma nova ferramenta nos estudos da estrutura do solo.