Long-term No-till Systems Research Articles

Influence of long-term (36 years) tillage practices on soil physical properties in a grain sorghum experiment in Southeast Texas

ABSTRACT Experiments were conducted to evaluate the impact of 36 years of no-tillage (NT), compared to conventional-tillage (CT), on soil physical properties in a continuous grain sorghum experiment. Results revealed that long-term tillage treatments had minimal impact on bulk density (BD), total porosity (TP), air-filled porosity (AFP), water-filled pore space (WFPS), and volumetric water content (Θv). However, water-holding capacity (WHC) was 26% greater in NT, compared to CT. Irrespective of the tillage system, soil physical properties differed across soil depth. The BD was greater at the 0 to 5, and 10 to 20 cm soil depths, compared to the 5 to 10 cm depth; further, BD was positively correlated with Θv (r = 0.47) and WFPS (r = 0.49). However, the TP and AFP values were greater (52.4% and 52.2%, respectively) at the 5 to 10 cm depth. Penetration resistance (MI) was maximum (≥ 48.11 J cm–1) at the greatest depth tested (60 cm) in both tillage systems. Overall, results indicated that NT had a positive impact on WHC. High WHC associated with long-term NT systems is expected to increase available soil water content, thereby improve productivity, especially under limited moisture environments.

A high-diversity/IPM cropping system fosters beneficial arthropod populations, limits invertebrate pests, and produces competitive maize yields

In the United States, current crop production often favors simplified rotations of maize and soybeans in conjunction with a heavy reliance on synthetic inputs that consequently degrade environmental health and increase production costs, without necessarily improving yields. While often stigmatized as underperforming compared to conventional systems, “sustainable intensification” of cropping systems offers an alternative that relies on crop rotation diversity, continuous crop cover, and integrated pest management to combat pests. Within a long-term no-till systems experiment, our main goal was to determine if a high diversity-IPM system (HiDiv-IPM) could compete with a low diversity-preemptive pest management system (LoDiv-PP) in terms of invertebrate pest management, biological control, and maize establishment and yield. Our results suggest that early-season pests, particularly caterpillars, reduced maize establishment by 10 % in the HiDiv-IPM system compared to the LoDiv-PP system. Both our simple and more diverse rotations suffered from slug damage that reduced crop establishment, however, overall slug abundance and damage tended to be equal. Despite lower seedling establishment and greater caterpillar damage, maize in the HiDiv-IPM rotation yielded similarly to the LoDiv-PP rotation, suggesting that other factors, such as higher levels of predation evident in the more diverse rotation or possible nutrient- and soil quality-related issues, contributed to productivity. These results support the notion that a HiDiv-IPM system can compete with a LoDiv-PP system and, contrary to the most common approach for controlling insects in maize production in the U.S., aggressive, preemptive pest management was not necessary to achieve competitive yields.

Nine-year impact of grazing management on soil acidity and aluminum speciation and fractionation in a long-term no-till integrated crop-livestock system in the subtropics

Integrated crop-livestock systems (ICLS) can be an option for agricultural sustainability in subtropics. Despite numerous studies evaluating ICLS, there have been limited investigations of aluminum (Al) dynamics in such systems. In this context, this study was conducted in 2001–2010 on Rhodic Hapludox soil with the objective of assessing the impacts of time and grazing on soil acidity and Al fractions (solid phase) and species (liquid phase) in ICLS (soybean-beef cattle) managed with a long-term no-till system. The crop succession consisted of soybean cultivation during summer and a mix of black oat + Italian ryegrass during winter. Treatments consisted of different grazing managements during the winter season: intensive grazing, moderate grazing, and no-grazing. For this study, sampling was performed prior to the first and after nine grazing seasons. Lime was applied to the surface of the entire study area immediately after the first grazing season. We demonstrated differences in the Al forms in the soil solid and liquid phases over time and with different managements. The ICLS with intensive grazing or moderate grazing during the winter season led to a lower availability of total Al in the soil solution and a higher base saturation and lower Al saturation in the soil solid phase compared to non-grazed areas. However, the soil pH is similar between grazed and non-grazed. Despite such differentiated dynamics, the carbon accumulated in the soil with a long-term no-till management guarantees that the preponderant Al form is linked to organic compounds, maintaining the content of phytotoxic species and the Al3+ activity below the critical limit for plant growth.

How diversity of crop residues in long-term no-tillage systems affect chemical and microbiological soil properties

Integrated systems of agriculture lead to better food and environmental quality, but these systems are complex and should be evaluated in long-term experiments. The objective of this study is to evaluate long-term NT systems with different histories, management and different quantity and quality of plant residues on chemical and microbiological soil properties. The NT systems are located in three experimental fields of Embrapa Cerrados, in the Cerrado region, with 26, 21 and 12 years of establishment. The NT systems were characterized for soil chemical and microbiological properties and for quantity and quality of crop residues. Soil properties studied were basal respiration (BR), microbial biomass carbon (MBC), total organic carbon (TOC), total nitrogen (TN) and microbial quotient (qMIC) in three depths from 0–30 cm layer. The systems with annual succession of soybean with maize intercropped with U. brizantha grazed or not in the off-season increased the quantity of crop residues (around 10.70 ton ha−1) and contributed more to the quality of the vegetal residues, in addition to increasing MBC (up to 716 mg kg-1 soil), TN (between 4 and 5 g kg-1 soil), TOC (35 to 40 g kg-1 soil) and qMIC (up to 1.83%), which indicates that this system promoted improvement in the quality of chemical and biological soil properties and contributed to carbon accumulation in the soil over a period of 26 years.

Effects of long-term no-tillage systems with different succession cropping strategies on the variation of soil CO2 emission

The optimization of conservationist production systems, whose goal is to increase carbon stocks and reduce greenhouse gas emissions, is considered one of the greatest challenges faced by agriculture nowadays. Therefore, this study aimed to assess the variation of soil CO2 emission (FCO2) and its relationship with soil attributes under long-term no-tillage systems with different successions of summer and winter crop sequences. Treatments consisted of combinations of three summer and two winter crop sequences. Summer sequences were maize monocrop (MM), soybean monocrop (SS), and soybean-maize intercrop (SM), while winter crops were crotalaria and maize. FCO2 showed no difference among summer sequences (p > 0.05). For winter crops, however, the soil under crotalaria crop residues presented higher FCO2 values (1.03 ± 0.027 μmol m−2 s−1) when compared to that under maize crop residues (0.94 ± 0.027 μmol m−2 s−1). Soil moisture presented the greatest influence on the temporal variation of FCO2, being correlated in the summer sequences MM (r = 0.79; p < 0.0001) and SS (r = 0.70; p = 0.002), as well as in the winter crops crotalaria (r = 0.78; p < 0.0001) and maize (r = 0.66; p = 0.005). In the Oxisol under no-tillage for >14 years, the spatial variation of FCO2 was explained by the soil physical attributes total porosity, macroporosity, microporosity, and soil temperature. The soil under crotalaria crop residues as a winter crop had an improvement in soil physical attributes, leading to a more aerated environment and hence a higher CO2 production process. However, the winter crops crotalaria (38.65 ± 0.08 Mg ha−1) and maize (38.14 ± 0.09 Mg ha−1) also provided a higher carbon stock on this tropical soil. Maize monocrop (41.13 ± 0.11 Mg ha−1) as a summer crop under no-tillage system also promoted higher carbon stocks on this tropical soil. A strategy to optimize no-tillage systems in terms of FCO2 reduction and increase in soil carbon stock is related to the adoption of crop cultivation that includes legumes and grasses under intercropping and succession. Therefore, our results suggested that the summer sequences used in this study might contribute to reducing FCO2 and that both winter crops influenced the increased soil carbon stock.

Progression of plant-parasitic nematodes and foliar and root diseases under no-tillage with different crop rotations

No-tillage is a cropping system that promotes minimal soil disturbance, full residue retention and diverse crop rotation. From a disease perspective, crop rotation is one of the best control measures in no-tillage systems, as many diseases are stubble-borne. A long-term no-tillage systems experiment was conducted from 2007 to 2016 in Western Australia to test effects of crop rotation and residue amount on soil health, crop growth and yield. The current research focusses on the progression of the main stubble-borne and root diseases and plant-parasitic nematodes in this experiment. The research compared a diverse crop rotation with a ‘typical’ farmer rotation, a cereal rotation and wheat monoculture. Three-year rotations were used and the crops and cultivars were changed periodically, within the rotations, to ensure they were relevant to farmers.Levels of root lesion nematode (Pratylenchus neglectus) and Pythium increased most in the pasture and diverse rotations, followed by the wheat monoculture and appeared to decrease slightly in the farmer and cereal rotations. The combination of canola and wheat, along with susceptible chickpea, appeared to favour root lesion nematode. In contrast, fallow and lupin in the farmer rotation appeared most effective at reducing levels. The relatively high numbers of P. neglectus in the pasture was likely due to continuous presence of a number of susceptible weeds and subterranean clover. The crop selections in the diverse rotation of this experiment have generally been a poor choice in terms of P. neglectus, the main nematode threat in Western Australia.By 2016, there was significantly greater Rhizoctonia solani in the soil following cereals compared with canola, chickpea and fallow. Nonetheless, the break crops appeared to have had a relatively short term effect on amounts of R. solani.Over the nine years, Fusarium spp. DNA in the soil increased most in the cereal rotation and wheat monoculture; it hardly changed in the farmer rotation and pasture and it declined in the diverse rotation.There was a decrease in Didymella pinodes/Phoma medicaginis var pinodella DNA (causing pea black spot) in the cereal rotation, farmer rotation and wheat monoculture. In contrast, there was a small increase in pea black spot pathogen DNA in the diverse rotation. This generally reflected the number of pea crops grown, except for the farmer rotation, which had peas grown at the same intensity as the diverse rotation. The difference between these two rotations was likely due to the lower amounts of residue in the farmer rotation, which had fallow and tillage since 2013. As expected, there were higher incidence of the stubble-borne disease in wheat and barley when following the same type of crop. Crop residue management, by windrow burning, had little effect on the level of leaf, root or crown diseases.The differences in host status between crop types and even varieties means that farmers require up-to-date information on the host status if rotations are going to be effective in reducing a broad range of plant-parasitic nematodes and pathogens in soils with no-tillage.

Investigation of short-term effects of winter cover crops on compaction and total soil carbon in a long-term no-till agricultural system

Implementation of winter cover crops (CC) is a conservation practice aimed at improving soil health and increasing water infiltration. Reduced tillage (e.g., no-till), another, more common conservation practice, shares these aims. While the literature concerning the main effects of CC and reduced tillage is rich, the additive effects of CC and reduced tillage are unclear and understudied—specifically, the adoption of reduced tillage long before (20+ years) CC implementation, which is common in the last half-century. This study assessed two of the potential short-term effects of CC when added in a long-term no-till system: reduction of soil compaction (SC) and addition of soil total carbon (STC). Four field plots in northeast Mississippi were planted with CC while two were utilized as controls having no CC. All plots were under no-till for the last 20+ years. Soil penetration resistance measurements (SC) and soil cores were collected in April of 2017, following two years of CC implementation, from 20 semirandomly selected locations in each plot. Model comparisons were used to explore variation in SC and STC between CC and control plots, and the contributions of covariates to the observed variation. Results of the selected models (model with highest Akaike9s weight) indicated there was no difference in SC between CC and control plots; however, slight variation in STC did exist between the two treatment levels (d ± 95% CI = 0.46 ± 0.39, p

Soil mixing and redistribution by strategic deep tillage in a sandy soil

Strategic deep tillage (SDT) is proposed as a single or occasional practice to help sustain the long-term productivity of the no-till system. Soil water repellence, herbicide resistant weeds, subsoil acidity and compaction are constraints that can evolve in long-term no-till systems and SDT may provide an effective solution for these. While the effect of SDT on the lateral and vertical movement of soil is understood, soil heterogeneity and mixing caused by SDT is not. Soil mixing may be an important factor for the availability of soil nutrients after SDT or for the effectiveness of soil amendments. Soil mixing and redistribution were quantified using coloured soil tracers and digital image analysis. Trenches of synthetic coloured soil were installed at four depths at a field site and four tillage treatments were applied; offset disc harrow and deep ripping (DHDR), disc plough (DP), mouldboard plough (MP) and rotary spader (RS). Digital images were acquired for soil pit faces at 5 cm intervals to capture the location of the coloured soil after SDT, these images were segmented and the 3-dimensional distribution of the coloured soil tracers was reconstructed. The mixing indices for the tillage treatments were low level (0.04–0.12). The vertical movement of soil differed between treatments; approximately 80, 60, 60 and 10% of soil from 0 to 10 cm was redistributed to deeper soil layers by MP, DP, RS and DHDR respectively. The soil profiles after the SDT treatments were composed of layered, or rotated soil that had been translocated within the working depth of the implement; however, there was some mixing at the interface between layers, or seams of soil that originated from different depths. The impact of a change in the spatial distribution of soil nutrients created by SDT on crop growth is an important knowledge gap.

Runoff and losses of nutrients and herbicides under long-term conservation practices (no-till and crop rotation) in the U.S. Midwest: A variable intensity simulated rainfall approach

The U.S. Farm Bill includes conservation practices that benefit both the environment and the farmer. The USDA Conservation Effects Assessment Project (CEAP) is a multi-agency effort to assess the efficiency of conservation practices to minimize non-point source pollution. This is follow-up study of a 28-year experiment design to assess the influence of the conservation practices of no-till and crop rotation systems (corn [Zea mays]-soybean [Glycine max]), compared to chisel tillage and monocropping systems (continuous corn) on soil health and water quality. In this study, changes on soil C and N, soil water content, runoff, and losses of ammonium-N, nitrate-N, soluble reactive P (SRP), atrazine, metolachlor, and glyphosate were compared to determine the influence of no-till and corn-soybean rotation systems, relative to chisel tillage and continuous corn, on plots planted with corn using variable intensity rainfall simulations. The long-term no-till systems had a positive impact on soil C and N, soil water, runoff, and losses of ammonium-N and nitrate-N; however, no effect was observed on losses of SRP, atrazine, metolachlor, and glyphosate. The corn-soybean rotation negatively influenced, compared to the continuous corn, soil C and N, soil water content, and increased runoff and the losses of all nutrients and herbicides measured in this study. These results suggest that additional conservation practices, in conjunction with no-till and corn-soybean rotations are needed to reduce surface losses of nutrients and pesticides while improving soil health.

Occasional soil tillage, liming, and nitrogen fertilization on long-term no-tillage system

Abstract: The objective of this work was to evaluate the residual effects of occasional soil tillage in a 17-year-old, no-tillage system, associated with liming and nitrogen fertilization, on the crop yields and chemical properties of a very clayey Oxisol in the South of Brazil. A randomized complete block design in split-split plots was used, with two soil managements (with or without plowing), two liming treatments (with or without the required dose to raise base saturation to 70%), five N doses applied on side-dress (0, 1, 2, 4, and 6 times the recommended amounts), and four replicates. A rotation system was used with corn and soybean in the summer, and with wheat and black oats in the winter. The residual effects of occasional soil tillage in a consolidated no-tillage system do not supplant those of liming applied on soil surface, in periods of water deficit, which subsidizes the recommendation to maintain the system consolidated. Excess N fertilization in no-tillage, with liming applied only on soil surface, may harm wheat yield, acidifying the topsoil and leaching Mg2+ to the subsurface soil layers. Without liming, soil acidification is more intense with N fertilization, which, however, favors the accumulation of organic matter on soil surface in a consolidated no-tillage system.

Clay Mineralogy of Subtropical Soils under Long-Term Organic Fertilization in No-Tillage Systems

ABSTRACT: Organic fertilization effect on physical-chemical properties in no-tillage systems in tropical soils has been widely investigated, but little is known about the effects of this practice on the mineralogy of the clay fraction. This study aimed to evaluate the clay-fraction mineralogy of two subtropical soils, fertilized with organic residues in long-term no-tillage systems. An Alfisol fertilized with 0, 40, and 80 m3 ha-1 yr-1 pig slurry was evaluated for eight years, and an Oxisol with 0, 8, and 16 [...]

The Influence of Tillage Frequency on Crop Productivity in Sub-Tropical to Semi-Arid Climates

Strategic tillage (ST), an occasional tillage in a continuous no-till (NT) farming system, is already being utilized by many landholders in the Northern Grains Region (NGR) of Australia to control weeds. But the impact on productivity (yield), both short- and long-term, has been largely under investigated. This study focused on yield data from 14 on-farm ST in NT experiments from 2012 to 2014 (3 years/4 seasons) and the comparison of the re-interpreted results of a long-term (27 years) tillage experiment. This study explored production impacts of tillage on long-term NT systems over the short and longer term. Results from tillage-frequency studies across the NGR demonstrated that overall grain yield was not significantly impacted. A long-term tillage trial at Biloela showed wheat (Triticum aestivum) and sorghum (Sorghum bicolor) grain yields were similar across no till, stubble mulch and reduced tillage treatments, these in turn were all significantly higher than aggressive tillage without stubble retention treatments. Dealing with increased herbicide resistance often associated with reduced tillage and no-till systems poses a real time issue with landholders in the NGR. This analysis of historical yield data together with the more recent strategic tillage data can aid in selecting the appropriate soil management option by providing tillage impacts on yield.

Simulating greenhouse gas emissions and stocks of carbon and nitrogen in soil from a long-term no-till system in the North China Plain

Accurate modeling of tillage impacts on the cycling of soil carbon (C) and nitrogen (N) and greenhouse gas (GHG) emissions is complicated due to the differences in soil organic matter decomposition, water holding capacity and soil temperature between different tillage systems. In the current study, the SPACSYS (Soil-Plant-Atmosphere Continuum System), a process-based model, was used to simulate the effects of two different tillage regimes on crop yields, the dynamics of soil organic carbon (SOC) and total nitrogen (TN) stocks from 2003 to 2009, and soil CO2 and N2O emissions from 2003 to 2007. The study was based on a long-term tillage experiment with a winter wheat (Triticum Aestivium L.) and summer maize (Zea mays L.) system in Calcaric Fluvisols (FAO) soil in the North China Plain. Farmers’ conventional tillage (CT), which is a predominant tillage method in the region, was used to compare with no-till (NT), an emerging technique for land conservation. In both treatments, chemical N fertilizer (F) was applied and crop straw (R) was incorporated in two field soils after harvest (no-till: NT-R-F; conventional tillage: CT-R-F). Statistical analyses indicated that the SPACSYS model reasonably simulated the maize yield under both NT-R-F and CT-R-F, but overestimated the wheat yield under NT-R-F by approximately 15%. In addition, the dynamics of SOC and TN stocks (0–10 cm soil depth) and soil CO2 and N2O emissions under both NT-R-F and CT-R-F were accurately simulated by the SPACSYS model. The simulations showed that NT-R-F significantly increased SOC and TN stocks at 0–10 cm soil depth, but not the wheat and maize yields compared to CT-R-F. Furthermore, NT-R-F reduced both soil CO2 and N2O emissions (P < .05) compared to CT-R-F. Our results also showed that NT-R-F led to greater C (3755 ± 942 kg C ha−1 yr−1) and N gains (179.8 ± 90.7 kg N ha−1 yr−1) in the plant and upper 20 cm depth of soil system than CT-R-F. In conclusion, the SPACSYS model can accurately simulate the processes of C and N cycles as affected by both conventional tillage and no-till systems in the North-China-Plain. Further studies need to focus on optimizing the rates of N fertilizer input and straw incorporation along with no-till to maintain the crop yield while reducing C and N losses to the environment.

Driving factors of soil carbon accumulation in Oxisols in long-term no-till systems of South Brazil

In a climate change scenario, it is important to understand the factors that lead to changes in a soil carbon (C) sink. It is recognized that such process is highly dependent on climate, soil properties, topography, and vegetation. However, few studies demonstrate how these mechanisms operate in highly weathered Oxisols. Therefore, this study evaluated the driving factors for C recovery and accumulation and its relations with fertility attributes in the soil profile (0 to 1m depth) in no-till (NT) croplands of south Brazil. The adoption of NT in the studied fields started between 1978 (pioneer areas) and 1990 and represent a range of textural and mineralogical characteristics South Brazil main croplands. Soil samples were collected in paired fields of native vegetation and NT (NV vs. long-term NT) to a depth of 1m. The studied NT areas of Rio Grande do Sul State were managed according to the principles of conservation agriculture (minimum soil disturbance, permanent soil cover and diverse crop rotation). The processes that drove SOC recovery in the studied sites were soil fertility management allied with high C input through intense crop rotation. The C recovery was were for areas with the predominance of soybean in the cropping system, higher levels of Al3+ and lower levels of Mg2+ and P. Sites with medium/high cropping intensity, lower levels of Al3+ and higher levels of P, Ca2+, Mg2+, and K+ resulted in higher C recovery.

Residual effect of surface-applied lime on soil acidity properties in a long-term experiment under no-till in a Southern Brazilian sandy Ultisol

The changes in soil chemical properties caused by surface lime application depend on the application dose, reaction time, and are limited to the top few centimeters of the soil profile. The present study aimed to monitor and to interpret the impacts of surface lime re-application at different rates and splitting rates on the amelioration of soil acidity and its distribution and migration through soil profile in a sandy Ultisol from Southern Brazil under long-term no-tillage (NT) system. The experiment was installed in an area where the conventional tillage (CT) was practiced till 1988 when the soil was limed (3.1Mgha−1) and then the area was maintained under NT. In October 1994, the soil was sampled and lime was reapplied at four rates: 0, 3.6, 5.4, and 6.0Mgha−1. The full dose to raise soil pH to 6.0 was applied in 1994 once. The rate of 5.4Mgha−1 was split in three times, applying 1.8Mglimeha−1 in 1994, 1995, and 1999, and the rate of 6.0Mgha−1 was split in five times, applying 1.2Mglimeha−1 in 1994, 1995, 1996, 1999, and 2000. The experimental design was randomized blocks with five replications. In October 2006 and 2012, i.e. after 18 and 24years of the start of NT or 12 and 18years after lime re-application (beginning of the experiment), soil samples were taken at each 1cm depth up to 10cm layer, each 2.5cm depth up to 10 to 25cm layer, and each 5cm depth from 25 to 60cm layer. Soil acidity attributes including active acidity (pH-H2O), aluminum (Al) saturation, exchangeable Al, exchangeable calcium (Ca), exchangeable magnesium (Mg) and base saturation were also evaluated. Results show that the re-acidification of the soil is extremely slow. Even after 24years without re-application of lime, the re-acidification process resulted in only 20% of the original potential acidity observed in the area under natural grassland. The surface application of lime in a re-acidified soil under NT promoted the formation of an alkalizing front by statistically modifying the soil acidity attributes up to 60cm. However, it was much less deeper (<35cm) when considering the agronomic interpretation of the soil acidity properties. Nevertheless, for both interpretations, the lime migration and its residual behavior were proportional to the lime application rate and its split application.

Alteration in soil fauna due to soil management and crop rotation in a long-term experiment

The evaluation of the population of meso and macrofauna organisms has been receiving attention in different studies related to soil quality. Therefore, the present study had as objective to evaluate the population of macro and mesofauna organisms, in an experimental area installed for 26 years in Parana / RS. Among the 11 existing treatments, six were selected by lot, grew in a Conventional and No-tillage system. Soil fauna organisms were captured at 10 cm depth. The method used for the extraction of edaphic organisms was Tullgren funnel. The collections were executed in blocks and repetitions that represented 312 samples. In the autumn, 60,138 m -2 individuals were estimated, and in the summer they were 28,348 m -2 individuals. The adoption of the long-term no-tillage system favors the biodiversity of the soil fauna in relation to the soil that has been undergoing two years of cultivation and four annual harrows since 1976. The native forest soil is more biodiverse than the cultivated one. The most representative edaphic taxon in the autumn were Acari, Collembola and Diptera, and in the summer they were Acari, Collembola, Hymenoptera and Larva of Lepidoptera. The phytosanitary management of the areas influence the diversity indexes of the edaphic fauna. The soil moisture abiotic factor acts severely under the edaphic fauna in the summer, being more evident in the conventional cropping system. The collection season conditioned to the abiotic factors - soil moisture and temperature - influences the density of individuals, species richness and the Shannon and Pielou indexes.

Mitigation of the Gradient of Chemical Properties in the Rooting Zone of Dystrophic Oxisols by Gypsum and Lime Inputs under a No-Till System

ABSTRACT Improvement of soil chemical properties in dystrophic Oxisols managed under long-term no-tillage system (NTS) with surface broadcast lime has been, frequently, restricted to a shallow topsoil layer. As a consequence, a sharply-defined chemical quality gradient is created, with deterioration from the surface towards deeper layers in Oxisols in southern Brazil. The aim of this study was to assess the temporal effects of gypsum, applied alone or in combination with lime, on Ca2+ content and Al3+ saturation in the rooting zone (RZ) (0.00-0.40 m). Four experiments were conducted from 2009 to 2014 in Typic Hapludox soils with distinct chemical qualities in the RZ managed under a long-term NTS (over 20 years) in Rio Grande do Sul (subtropical region). A randomized block experimental design with three replications was used. Experiments I and II were implemented in 2009, with treatments consisting of gypsum rates ranging from 0.0 to 6.5 Mg ha-1. The other two experiments were implemented in 2011. In experiment III, a split-plot design was used, with plots received gypsum rates ranging from 0.0 to 5.0 Mg ha-1, and the subplots received two lime rates (0.0 and 2.0 Mg ha-1). A split-plot design was also used in experiment IV, with plots receiving gypsum rates ranging from 0.0 to 6.0 Mg ha-1, and subplots receiving four lime rates, ranging from 0.0 to 4.8 Mg ha-1. Soil samples were stratified in layers at depth from 0.00 to 0.60 m and taken during the period of the experiment. The use of gypsum increased the Ca2+ and SO42−-S contents, proportional to the rate applied, and lowered Al3+ saturation throughout the soil profile evaluated. However, an increase in base saturation of the subsoil (0.25-0.60 m layer) was only observed at high rates of gypsum (>5.0 Mg ha-1) in the medium-term and through accumulation of a high rainfall volume. A faster and more pronounced effect of subsoil improvement was observed when the chemical quality of the topsoil layer was already high and when gypsum and lime were applied in combination. Greater improvement in subsoil chemical quality induced by gypsum, alone or in combination with lime, was found in a period exceeding 30 months (Experiments III and IV), remaining for up to 54 months (Experiments I and II). The combination of gypsum with lime was an effective strategy to increase vertical movement of bases in the RZ, mitigating the gradient of chemical quality in dystrophic Oxisol, avoiding discontinuity in the NTS.

English

Soil physical and structural degradation may influence crop productivity over time in long-term no-tillage system areas. A field study was conducted at two sites, Palmeira das Missoes and Nao-Me-Toque, in southern Brazil to quantify soil physical/hydraulic and structural changes in zones with different yield potentials. The sites have been managed under no-tillage system without soil disturbance for more than 10 years. Soils were classified as Oxisols (Hapludox). Each site was divided into three zones with low, medium and high yield potentials based on overlapping of yield maps obtained from harvesters with precision agriculture tools. Within each yielding zone soil samples were collected to determine bulk density, porosity and aggregate stability. In addition, water infiltration rate and initial time for starting surface runoff were measured using a sprinkler infiltrometer (Cornell Sprinkler infiltrometer). Our findings showed that soils under low-yielding zones presented higher bulk density, lower macro-aggregate stability and water infiltration rate as well as shorter time for starting surface runoff compared to high-yielding zones. Therefore, these results suggest that soil physical and structural degradations have induced crop yield losses under long-term no-tillage areas. Macro-aggregate stability (>4.76 mm) and water infiltration rate were efficient parameters for distinguishing yielding zones in Oxisols managed under long-term no-tillage system in southern Brazil. Key words: Soil compaction, Cornell Sprinkler Infiltrometer, soil aggregation, water infiltration.

Sampling Layer for Soil Fertility Evaluation in Long-Term No-Tillage Systems

ABSTRACT In no-tillage (NT) systems, there is no plowed layer since the soil is not tilled. Thus, the soil layer for fertility evaluation can be defined as the one in which the fertility indices are affected by the surface application of lime and fertilizers and soil properties have the closest relationship with crop yields. The objective of this study was to determine the most appropriate soil layer under long-term NT for sampling for fertility evaluation in the South-Central region of [...]

Conceptual framework for capacity and intensity physical soil properties affected by short and long-term (14 years) continuous no-tillage and controlled traffic

Recent studies have shown harmful effects of soil compaction in no-tillage system (NTS), but there are indications that soil structure improves with time of NTS adoption. We formulated the hypothesis that topsoils of NTS initially have worse soil physical conditions than those under conventional systems, but these conditions gradually improve with time also down to deeper depth, even when the soil is wheeled by farm machinery. Our objective was to evaluate the effect of a long-term no-tillage system and machine traffic on soil mechanical and hydraulic properties. The treatments and soil conditions consisted of five periods since the last conventional tillage (or age of NTS) in a Hapludox: 0.2, 1.5, 3.5, 5 and 14 years, with and without traffic; named recent tillage, and initial, intermediate, transition and stabilized NTS phases. Soil samples were collected from soil layers 0–7, 7–14 and 14–21cm depth to determine soil porosity, precompression stress, compressibility coefficient, saturated hydraulic conductivity, air permeability, water retention curve, bulk density and organic carbon. Conventional tillage of soil previously under no-tillage significantly affected soil capacity properties, resulting in high macroporosity and deformation susceptibility, low bulk density and precompression stress. Intensity properties were affected initially by an increased soil pore obstruction, negatively affecting air permeability and saturated hydraulic conductivity, from 0 to 21cm soil depth. However, after five years of no-tillage there was an increase in microporosity and, although small, in soil organic carbon, especially in the 0–7cm soil layer; thus, soil water retention and soil intensity properties (like soil water and air permeability) were also improved, regardless of farm machinery traffic. Over time, soil reconsolidation occurred, which resulted in reduction of the compressibility coefficient and degree of compactness, mainly in the upper layers (0–7 and 7–14cm). However, in the deepest layer with the least disturbance, the degree-of-compactness and bulk density increased. The evolution of physical properties and processes (from recent tillage to stabilized NTS phase) for no-tilled soil is proposed for controlled and uncontrolled traffic systems as a framework based on field data for capacity and intensity soil properties. The process of creating aggregates is represented, at first, by an increased number of contact points before they are re-loosened and strengthened at the same time by a rearrangement of particles, reducing aggregate bulk density but increasing soil strength at the same time. The framework is divided into 4 phases: initial (1.5 years), intermediary (3.5 years), transitional (5 years), and stabilized (14 years) conditions.