No-till Plots Research Articles

High-resolution morphologic characterization of conservation agriculture

In the last decade, conservation agriculture (CA) has received particular attention from both governmental and non-governmental organizations. CA aims to achieve sustainable agricultural production. The principles of CA include minimal soil disturbance, permanent soil cover derived from crop residues or cover crops, and crop rotations that benefit soil and water conservation. Agricultural practices influence the micro-topography and modify the surface roughness, altering several important processes such as infiltration, water storage depression, and soil water erosion. In this work, we explore the effectiveness of high-resolution topography in characterizing no-tillage (NT) versus conventional tillage (T) surface morphology in order to better understand the hydro-geomorphic processes associated with these crop systems. High-resolution (2 cm) Digital Elevation Models (DEMs), derived using the Structure from Motion (SfM) photogrammetric technique, were processed for six plots (3 cultivated with NT, 3 with T) in a clay loam soil. The study area is located in northeast Italy. Several morphometric terrain parameters (e.g., connectivity, curvature and relative elevation attribute), were computed for each plot. The analysis provided challenging insights: compared to T, surfaces in the NT plots were rougher, had more pronounced slopes and curvatures, sediments with a widespread connection to the plot boundaries, had more irregular flow paths, and had a higher water storage potential due to surface concavities. This can be translated into a surface morphology that can significantly affect surface runoff, sediment transport, and the off-site movement of agricultural chemicals.

Strategic tillage may sustain the benefits of long-term no-till in a Vertisol under Mediterranean climate

Long-term no-till or reduced tillage may decline functioning ability of soils due to surface/subsurface compaction and/or stratification of plant nutrients. A long-term (ten years) field experiment was established in 2006 in the Çukurova region of Turkey to evaluate the impact of tillage on the physical properties of a soil under a Mediterranean climate. The tillage systems investigated included two conventional (CT-1 and CT-2), three reduced (RT-1, RT-2 and RT-3) and two no-till (NT and ST), including strategic/occasional tillage. Nine-year old undisturbed no-till plots were divided into two categories and half of these plots were plowed by a moldboard plow in November 2015, and this practice was defined as strategic tillage (ST), while remaining half of the plots left undisturbed. Soil samples were collected from disturbed and undisturbed plots of NT as well as plots under other tillage systems from three soil depths (i.e., 0–10, 10–20 and 20–30 cm) in November 2016. The crop rotation at the experimental areas was winter wheat (Triticum aestivum L.), soybean (Glycine max. L.) – grain maize (Zea mays L.) – winter wheat. Soil samples were analyzed for aggregate stability (AS), mean weight diameter (MWD), bulk density (BD), water filled pore space (WFPS), water content at field capacity (FC), permanent wilting point (PWP), available water content (PAW), micropores (MiP), macropores (MaP), total porosity (TP), and penetration resistance (PR). The ST decreased MWD of surface soil compared to NT by 7.2%, while MWD under ST was higher than NT by 78.0% and 103.6% for 10–20 and 20–30 cm depths, respectively. The NT and RT resulted higher BD and PR, and lower MaP and TP than CT and ST in all three depths, though the values were generally not limiting for crop growth. The ST significantly (P < 0.01) decreased BD and PR within 30 cm of soil surface. However, water content at FC, PWP and also PAW in 0–10 and 10–20 cm depths were significantly reduced with ST compared to NT. The ST significantly (P < 0.01) increased the MaP and TP compared to NT which favors better aeration and water movement. The mean WFPS under NT, RT-2 and RT-3 systems in 0–10 cm and with all tillage systems (except ST in 10–20 cm) in subsurface layers were higher than 60%, which is considered a threshold for nitrogen losses as N2O fluxes. Implementation of ST into conservational practices under Mediterranean climate could be a viable management option to overcome some of the disadvantages of long-term conservation tillage and thereby to improve physical soil conditions for crop growth, air and water movement.

Single Session of Chiseling Tillage for Soil and Vegetation Restoration in Severely Degraded Shrublands

While tillage of agricultural lands has been used extensively, its utilization for restoring degraded semi-natural lands is rare. This study was conducted in the arid southern Israel in a shrubland which has faced severe degradation processes over time, including soil erosion and compaction, and negation of vegetation recovery. In 2014, research plots were established for assessing the impact of a single chiseling session on the ecosystem’s restoration capacity. The study treatments included deep chiseling (35 cm), shallow chiseling (20 cm), and control (no-tillage). Data on spontaneously-established vegetation was collected one, two, and three years after the plots’ establishment, and soil data was collected once—three years after the plots’ establishment. Assessments of the vegetation parameters revealed a general similarity between the two chiseling treatments, which were generally better than those of the no-till plots. The soil properties revealed generally greater soil quality under the two chiseling treatments than that under the control plots, and a somewhat better soil quality for the deep chiseling than that for the shallow chiseling. Overall, results of this study show that in severely degraded lands, self-restoration processes are hindered, negating the effectiveness of passive restoration practices, and necessitating active intervention practices to stimulate restoration processes.

Long-term no-tillage application increases soil organic carbon, nitrous oxide emissions and faba bean (Vicia faba L.) yields under rain-fed Mediterranean conditions

The introduction of legumes into crop sequences and the reduction of tillage intensity are both proposed as agronomic practices to mitigate the soil degradation and negative impact of agriculture on the environment. However, the joint effects of these practices on nitrous oxide (N2O) and ammonia (NH3) emissions from soil remain unclear, particularly concerning semiarid Mediterranean areas. In the frame of a long-term field experiment (23 years), a 2-year study was performed on the faba bean (Vicia faba L.) to evaluate the effects of the long-term use of no tillage (NT) compared to conventional tillage (CT) on yield and N2O and NH3 emissions from a Vertisol in a semiarid Mediterranean environment. Changes induced by the tillage system in soil bulk density, water filled pore space (WFPS), organic carbon (TOC) and total nitrogen (TN), denitrifying enzyme activity (DEA), and bacterial gene (16S, amoA, and nosZ) abundance were measured as parameters potentially affecting N gas emissions. No tillage, compared with CT, significantly increased the faba bean grain yield by 23%. The tillage system had no significant effect on soil NH3 emissions. Total N2O emissions, averaged over two cropping seasons, were higher in NT than those in CT plots (2.58 vs 1.71 kg N2O-N ha−1, respectively; P < 0.01). In addition, DEA was higher in NT compared to that in CT (74.6 vs 18.6 μg N2O-N kg−1 h−1; P < 0.01). The higher N2O emissions in NT plots were ascribed to the increase of soil bulk density and WFPS, bacteria (16S abundance was 96% higher in NT than that in CT) and N cycle genes (amoA and nosZ abundances were respectively 154% and 84% higher in NT than that in CT). The total N2O emissions in faba bean were similar to those measured in other N-fertilized crops. In conclusion, a full evaluation of NT technique, besides the benefits on soil characteristics (e.g. TOC increase) and crop yield, must take into account some criticisms related to the increase of N2O emissions compared to CT.

Abundance and depth stratification of soil arthropods as influenced by tillage regimes in a sandy loam soil

AbstractDifferent tillage regimes can change soil micro‐environmental characteristics, which may influence the distribution and abundance of soil arthropods. In this study, soil arthropods and soil properties under a winter wheat–summer maize cropping system were investigated in different tillage regimes over four seasons at two depths. The tillage treatments included conventional tillage (CT), tillage once a year (T1), tillage every two years (T2) and no‐tillage (NT). The results showed that the primary taxa of soil arthropod were Acarina (65.8%), Collembola (28.5%), Diplura (1.4%) and Coleoptera (1%) over the whole sampling period. The total arthropod density was influenced by tillage treatments and season of sampling. Values for CT plots were significantly greater than those for the NT plots in autumn and spring. In contrast, the Shannon–Wiener diversity index (H’) and the evenness index (J) were relatively higher in CT treatment. The Acarina/Collembola (A/C) ratio was significantly smaller in NT treatment for some sampling seasons as mites were more sensitive to tillage practices. The QBS‐ar index did not show a clear pattern among treatments in this study. Soil arthropods notably showed seasonal variation in depth stratification. Relative to CT, the total soil arthropods in the NT plots tended to concentrate in the upper layer due to soil compaction in the lower layer. The climate conditions and soil physical properties were the main factors affecting the soil arthropod distribution and composition, as the soil chemical and microbial properties did not differ significantly among all tillage treatments.

Reducing CO2 Flux by Decreasing Tillage in Ohio: Overcoming Conjecture with Data

While the literature is clear about excessive tillage decreasing soil carbon (C) content, there are few experimental studies that document the comparative effects of soil and crop management on C sequestration. Using micrometeorology we measured CO2 flux from a maize crop grown on both no-till and tilled soils in north-central Ohio. We used Bowen Ratio Energy Balance (BREB) systems to quantify the flux between the atmosphere and either the soil surface (at crop planting) or 0.2 m above the canopy once the crop was established and growing. The no-till plot sequestered 263 g CO2 m-2 (90% confidence interval -432.1 to -99.9) while the tilled plot emitted 146 g CO2 m-2 (90% confidence interval -53.3 to 332.2) during 104 days of the 2015 growing season; a net difference of 410 g CO2 m-2. The difference is statistically significant at the 90% confidence level (based on a bootstrap analysis). The results indicate that no-tillage practices can sequester C, maintain soil productivity, and ensure landscape sustainability.

Salmonella and Fecal Indicator Bacteria Survival in Soils Amended with Poultry Manure

Minimizing the risks associated with manure-borne pathogenic microorganisms requires an understanding of microbial survival under realistic field conditions. The objective of this 3-year study was to assess the fate of Salmonella (SALM) and fecal indicator bacteria (FIB), E. coli (EC) and enterococci (ENT), in glacial till-derived soils, after application of poultry manure (PM) to cornfields under chisel-plowed (CP) or no-till (NT) management. From 2010 to 2012, soil samples were obtained each spring at 0–15- and 15–30-cm depths, to determine whether over-wintering of target bacteria had occurred. Sampling was followed by application of PM at low (PM1) and high (PM2) rates, based on nitrogen application goals. In 2012, soil samples were collected 21, 42, and 158 days after manure application (DAM), to assess the effects of time, application rates, and tillage on frequency of detection and concentrations of target bacteria. Despite dry conditions, all three target organisms were detected 158 DAM in 2012, and detection of these organisms in spring soil samples from manured plots in 2011 and 2012, nearly a full year after PM application, suggests that these organisms can persist in the soil environment long after application. The highest SALM concentration (790 cfu/g dry weight) and detection rate (25%) was found in PM2 plots 42 DAM. SALM were detected more frequently in CP plots (20%) compared to NT plots (5%). In contrast, tillage practices had no apparent effect on EC or ENT survival, as indicated by both soil, and decay rates estimated from tile-water bacteria concentrations. Decay rate constants (μ) ranged from 0.044 to 0.065 day−1 for EC and 0.010 to 0.054 day−1 for ENT.

Fertilizer placement and tillage effects on phosphorus concentration in leachate from fine-textured soils

Adoption of no-tillage in agricultural watersheds has resulted in substantial reductions in sediment and particulate phosphorus (P) transport in surface runoff. No-tillage, however, may result in increased losses of dissolved P in tile-drained landscapes due to the accumulation of P in surface soil layers and prevalence of preferential flow pathways. The objective of this study was to examine the effect of fertilizer placement and tillage on P leaching in fine-textured soils following fertilizer application. Rainfall simulations (90 min; 3.8 cm rainfall depth) immediately following application of monoammonium phosphate fertilizer (75 kg P ha−1) were conducted on 9 m2 plots with pan lysimeters (0.6 m depth) in four agricultural fields located in northwestern Ohio, USA. Three fertilizer placement treatments that covered a range of soil disturbance and soil-fertilizer mixing (broadcasted, injected, and tilled) were replicated on each field. Stable water isotopes were used to separate leachate into preferential and matrix flow components. Results showed that leachate dissolved P concentration was significantly greater when fertilizer was surface broadcast on no-tilled plots (43.7 mg L−1) compared to when the fertilizer was either injected (14.9 mg L−1) or tilled (11.0 mg L−1) into the soil. Event water comprised between 6 and 46% (mean = 22%) of lysimeter leachate and did not vary among treatments. Similar event water contributions among treatments suggest that the disruption of the macropore network was not likely the main mechanism responsible for decreased P concentration in leachate, but rather increased soil-fertilizer contact and decreased interaction between the highly soluble fertilizer and ponded surface water were likely responsible for decreased P concentrations observed for the injected and tilled treatments compared to the broadcasted treatment. Findings indicate that subsurface injection of fertilizer has the potential to limit dissolved P leaching compared to surface broadcast applications and also minimize soil disturbance relative to tillage; thus, it should be considered a promising conservation practice to help meet water quality goals in tile-drained landscapes.

Real-Time, Variable-Depth Tillage for Managing Soil Compaction in Cotton Production

Cotton root growth is often hindered in the Southeastern U.S. due to the presence of root-restricting soil layers. Tillage must be used to temporarily remove this compacted soil layer to allow root growth to depths needed to sustain plants during periods of drought. However, the use of a uniform depth of tillage may be an inefficient use of energy due to the varying depth of this root-restricting layer. Therefore, the objective of this project was to develop and test equipment for controlling tillage depth “on-the-go” to match the soil physical parameters, and to determine the effects of site-specific tillage on soil physical properties, energy requirements, and plant responses in cotton production. Site-specific tillage operations reduced fuel consumption by 45% compared to conventional constant-depth tillage. Only 20% of the test field required tillage at recommended depth of 38-cm deep for Coastal Plain soils. Cotton taproot length in the variable-depth tillage plots was 96% longer than those in the no-till plots (39 vs. 19.8 cm). Statistically, there was no difference in cotton lint yield between conventional and the variable-depth tillage. Deep tillage (conventional or variable-rate) increased cotton lint yields by 20% compared to no-till.

Long‐Term Tillage on Yield and Water Use of Grain Sorghum and Winter Wheat

Core Ideas Average sorghum yield advantage was 120% for no tillage over conventional tillage and 55% for reduced tillage over conventional tillage.Average wheat yield advantage was 31% for no tillage over conventional tillage and 12% for reduced tillage over conventional tillage.Available soil water at planting in soil profile was less for conventional tillage than both no tillage and reduced tillage for both crops.There was a decline in wheat yield over time due to increased seasonal temperature. Tillage is among crop management factors that affect yield, profitability, and environmental quality. The objective of our study was to evaluate the effect of three long‐term tillage intensities; conventional tillage (CT), reduced tillage (RT), and no‐till (NT), on winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor L.) yield, available soil water (ASW), and water productivity. The study was conducted near Tribune, KS, from 1991 through 2015 in a wheat–sorghum–fallow (WSF) rotation. The CT plots were tilled (primarily with a sweep plow), on average, four to five times per fallow season; NT plots used herbicides for weed control during fallow. The RT plots used a combination of herbicides and tillage for weed control during fallow prior to both crops for years 1991 to 2000; and, for the years 2001 to 2015, the RT system was NT before sorghum planting (short‐term NT) and CT before wheat planting. On average, there was a 31% wheat yield advantage for NT over CT, 16% NT over RT, and 12% RT over CT. On average, there was a 120% sorghum yield advantage for NT over CT, 41% NT over RT, and 55% RT over CT. Sorghum yields were 80% greater for continuous NT compared with short‐term NT (2001–2015 RT). The average of profile ASW at planting was less for CT compared with NT and RT. There was a significant yield and water productivity benefit in the order NT &gt; RT &gt; CT for both crops, but greater for sorghum than wheat.

Decimetric‐Scale Two‐Dimensional Distribution of Soil Phosphorus after 20 Years of Tillage Management and Maintenance Phosphorus Fertilization

Core Ideas 2‐D distribution of Mehlich‐3 P across seeding row had no spatial pattern in no‐till and moldboard plow. Horizontal distribution of Mehlich‐3 P was less sensitive to extrinsic factors. Soil‐surface P accumulation in no‐till is due in part to P recycled by corn and soybean. Surface P accumulation in no‐till is also due to the replenishment of solution P by residual P. Improving soil test P assessment at plot scale is essential for productivity in conservation agriculture systems. We characterized the distribution of Mehlich‐3 P (PM3) concentrations at the decimetric scale with depth on either side of the sowing row in no‐till (NT) and moldboard plow (MP) plots fertilized with 35 kg P ha–1 every 2‐yr in a corn–soybean rotation (20‐yr). A total of 996 soil samples (83 samples × 2 depths [0–5 and 5–20 cm] × 6 plots [3 blocks each MP and NT]) were collected at corn harvest in 2012. The average PM3 concentrations in the 0‐ to 5‐cm layer were 35.7 and 63.4 mg kg–1 in MP and NT, respectively. The PM3 concentration in the 5‐ to 20‐cm depth was similar between MP and NT and averaged 32.0 mg kg–1. The horizontal distribution of PM3 concentrations in these plots was less sensitive to extrinsic factors including tillage, P fertilization and soil depth. High coefficients of variation were associated with PM3 data in both MP (77 and 63% at 0–5 and 5–20 cm, respectively) and NT plots (46 and 66% at 0–5 and 5–20 cm, respectively). It is possible that this strong overall variability overshadowed any PM3 pattern that could have been introduced by NT management. Geostatistical semivariance analysis indicated a predominance of random spatial dependence in most plots, except two plots (one MP and one NT) with moderate spatial structures. The 2‐D geospatial model related to tillage was not detected by the sampling grid used at this experimental site. Therefore, a similar sampling strategy would be appropriate and could be recommended for these two tillage systems in this long‐term corn–soybean rotation.

Long-term no-till: A major driver of fungal communities in dryland wheat cropping systems.

In the dryland Pacific Northwest wheat cropping systems, no-till is becoming more prevalent as a way to reduce soil erosion and fuel inputs. Tillage can have a profound effect on microbial communities and soilborne fungal pathogens, such as Rhizoctonia. We compared the fungal communities in long-term no-till (NT) plots adjacent to conventionally tilled (CT) plots, over three years at two locations in Washington state and one location in Idaho, US. We used pyrosequencing of the fungal ITS gene and identified 422 OTUs after rarefication. Fungal richness was higher in NT compared to CT, in two of the locations. Humicola nigrescens, Cryptococcus terreus, Cadophora spp. Hydnodontaceae spp., and Exophiala spp. were more abundant in NT, while species of Glarea, Coniochaetales, Mycosphaerella tassiana, Cryptococcus bhutanensis, Chaetomium perlucidum, and Ulocladium chartarum were more abundant in CT in most locations. Other abundant groups that did not show any trends were Fusarium, Mortierella, Penicillium, Aspergillus, and Macroventuria. Plant pathogens such as Rhizoctonia (Ceratobasidiaceae) were not abundant enough to see tillage differences, but Microdochium bolleyi, a weak root pathogen, was more abundant in NT. Our results suggest that NT fungi are better adapted at utilizing intact, decaying roots as a food source and may exist as root endophytes. CT fungi can utilize mature plant residues that are turned into the soil with tillage as pioneer colonizers, and then produce large numbers of conidia. But a larger proportion of the fungal community is not affected by tillage and may be niche generalists.

Impact of tillage management on the short- and long-term soil carbon dioxide emissions in the dryland of Loess Plateau in China

Soil carbon dioxide (CO2) emission from agricultural areas is a complex phenomenon with high temporal and spatial variability. Tillage practices can affect drivers of CO2 production and therefore influence emissions by soils. However, the impact of tillage management on CO2 emissions from soil is uncertain due to specific climate and soil characteristics. A field experiment was initiated in 1992 in Shanxi, China including the no-tillage plots with straw mulching (NT) and conventional-tillage (CT) treatment. In 2012, another treatment (NT0) was conducted during which the straw was not returned to the plots when the winter wheat harvested. The CO2 emissions, soil temperatures and soil moisture content were measured during the fallow and wheat-growing periods from 2013 to 2015. Results showed that the rate of CO2 emissions was significantly higher immediately after tillage operation in the CT treatment. The annual CO2 emission rate in the NT treatment was significantly greater than that in the CT and NT0 treatments (P<0.05). For different season, the highest CO2 emissions rate occurred in summer (0.20gCO2-Cm−2h−1) while the lowest CO2 emissions rate occurred in winter (0.04gCO2-Cm−2h−1). These rates were only positively correlated with the soil temperatures (P<0.05) and not significantly correlated with the soil moisture contents. Our results indicated that NT farming practices demonstrated increases CO2 emissions from soil compared with the CT and NT0 treatments under dryland cropping system.

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.

Methanotrophic bacterial diversity in two diverse soils under varying land-use practices as determined by high-throughput sequencing of the pmoA gene

Methanotrophic bacteria in soil serve as the only known biological sink of atmospheric methane, and impact net methane emission from soils. Most members of methanotrophs use particulate methane monooxygenase enzyme, encoded by the pmoA gene, to oxidize methane. Here, Illumina sequencing (iTAG) of pmoA gene was carried out to examine methanotrophic bacterial diversity in soils under different land use. Additionally, the effect of soil-type on pmoA amplicon sequence abundance was analyzed. Two sites in Ohio, each comprising of long-term no-tillage plots, plow-tillage plots, grassland, and forest were sampled. The tillage plots also included continuous-corn and corn-soybean crop rotations. By referencing a curated database of the pmoA gene, we were able to identify eight genera of methanotrophs with varying relative abundances in the samples. Additionally, four genera were differentially abundant across samples (alpha=0.005) and included Methylocystis, Methylocococcus, Methylosoma, and USCa. About 30% of processed sequences were unclassified. Nonmetric multidimensional scaling (NMDS) of unweighted UniFrac and Bray-Curtis metrics showed clear community distinction based on sites. Soil type had the most significant effect (p<0.005) on community (dis)similarity, despite the lack of clear diversity patterns with respect to land use. Although community composition of samples from agricultural fields appeared to cluster closer to each other as compared to forested areas and grass areas, nominal variable modeling showed soil type (which were specific to the sites sampled) as the strongest driver of methanotrophic community structure. This study was the first to employ high-throughput paired-end iTAG sequencing of a functional gene to understand microbial community dynamics. Our findings also indicate that functional gene sequencing on advanced sequencing platforms may be used to infer community dynamics of microbes belonging to unique functional guilds. This study also highlights the need to develop functional genes' reference databases that are compatible with the current iTAG sequence analyses software.

Yield, Weed Infestation and Seed Quality of Soybean Glycine max L. Merr. under Different Tillage Systems

Soybean is a very valuable crop plant and the soybean crop area is continually increasing in the world and in Poland. The effectiveness of soybean cultivation depends on soil and climatic conditions as well as on appropriate tillage. An alternative for plough tillage in the cultivation of soybean is to grow this crop using no-tillage, the popularity of which is constantly growing. The aim of this study was to compare the effect of conventional tillage (CT) and no-tillage (NT) on yield, weed infestation and qualitative seed composition of soybean grown under the conditions of the Lublin Upland. A field study was carried out over the period 2009-2012 at the Czeslawice Experimental Farm (51° 18′ 23″ N, 22° 16′ 2″ E). The experiment was set up on loess-derived grey-brown podzolic soil as a split-block design in four replicates. The experimental factors were the following tillage systems: conventional tillage (CT) and no-tillage (NT). The soybean cultivar Nawiko was grown in the experiment. The present study showed that the soybean seed yield obtained under CT was higher by 24.3% than under NT. The main reason of the seeds yield decrease in the NT was less soybean plant density. The significant higher number and weight of weeds were recorded in NT, relative to CT. The oil content in seed harvested from the NT plots was found to be higher by 0.3%.

Bacterial Communities on Wheat Grown Under Long-Term Conventional Tillage and No-Till in the Pacific Northwest of the United States

Cultural practices, such as tillage, often have widespread impacts on phytobiomes. No-till has been increasingly adopted by wheat growers in the dryland cropping areas of the inland Pacific Northwest in the United States to reduce soil erosion and decrease fuel and labor inputs, yet there are limited data on how conversion to no-till impacts plant-associated bacteria in this highly productive system. To address this knowledge gap, we evaluated bacterial communities in bulk and rhizosphere soil of wheat in two locations (Idaho and Washington) for 2 years, comparing long-term no-till plots and adjacent plots under conventional tillage. In this study, members of phylum Proteobacteria were relatively more abundant in rhizosphere soil, while Acidobacteria and Gemmatimonadetes were more abundant in bulk soil than in the rhizosphere. Bacteroidetes were more frequent under conventional than conservation tillage. In general, bacterial families were more affected by the position of the sample (rhizosphere versus bulk soil) than by tillage practices. Families generally regarded as copiotrophic (Oxalobacteriaceae, Pseudomonadaceae, and Cytophagaceae) were more abundant in rhizosphere soil than bulk in both years. On the contrary, oligotrophic families such as Gaiellaceae and those within Gemmatimonadetes were more abundant in bulk soil than in the rhizosphere. Families affected by tillage varied between the 2 years. These results suggest that bacterial communities in soil were more influenced by plant proximity (rhizosphere versus bulk soil) than by tillage practices, but that specific differences were not consistent and may vary among locations and years.

Effects of strategic tillage on short-term erosion, nutrient loss in runoff and greenhouse gas emissions

Occasional strategic tillage (ST) of long-term no-tillage (NT) soil to help control weeds may increase the risk of water, erosion and nutrient losses in runoff and of greenhouse gas (GHG) emissions compared with NT soil. The present study examined the short-term effect of ST on runoff and GHG emissions in NT soils under controlled-traffic farming regimes. A rainfall simulator was used to generate runoff from heavy rainfall (70mmh–1) on small plots of NT and ST on a Vertosol, Dermosol and Sodosol. Nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) fluxes from the Vertosol and Sodosol were measured before and after the rain using passive chambers. On the Sodosol and Dermosol there was 30% and 70% more runoff, respectively, from ST plots than from NT plots, however, volumes were similar between tillage treatments on the Vertosol. Erosion was highest after ST on the Sodosol (8.3tha–1 suspended sediment) and there were no treatment differences on the other soils. Total nitrogen (N) loads in runoff followed a similar pattern, with 10.2kgha–1 in runoff from the ST treatment on the Sodosol. Total phosphorus loads were higher after ST than NT on both the Sodosol (3.1 and 0.9kgha–1, respectively) and the Dermosol (1.0 and 0.3kgha–1, respectively). Dissolved nutrient forms comprised less than 13% of total losses. Nitrous oxide emissions were low from both NT and ST in these low-input systems. However, ST decreased CH4 absorption from both soils and almost doubled CO2 emissions from the Sodosol. Strategic tillage may increase the susceptibility of Sodosols and Dermosols to water, sediment and nutrient losses in runoff after heavy rainfall. The trade-offs between weed control, erosion and GHG emissions should be considered as part of any tillage strategy.

Effect of No‐Till Practice on Runoff and Nonpoint Source Pollution from an Intensively Farmed Field in Korea

AbstractA 2‐year runoff plot study was conducted under simulated rainfall to explore the effects of no‐till (NT) practice on the runoff ratio and NPS pollution in an intensive farming region of Korea. Eight 5 × 30 m runoff plots, four each on 3 and 8% slopes, were prepared in existing loamy sand fields. Cultivation in two plots on each slope followed conventional practice (CT). Six rainfall simulations were conducted during the study, each of a nominal 1 h duration and 30 mm h‐1 intensity. The runoff ratio of the NT plots decreased 64.9% compared with that of the CT plots. The reduction of NPS pollution load by the NT treatment was 88.3% (SS), 79.0% (CODCr), 86.4% (CODMn), 66.4% (BOD), 67.6% (TN) and 73.6% (TP) compared to losses from the CT plots, with no reduction in average crop yield. Runoff reduction was a key factor in the reduction of pollution loads. The study demonstrated that agricultural NPS pollution loads can be significantly reduced by the application of no‐till practice without harming crop productivity. Furthermore, NPS pollution loads can be controlled better if management practices are targeted for runoff reduction rather than concentration reduction. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Corn stover harvest and tillage impacts on near-surface soil physical quality

Excessive harvest of corn (Zea mays L.) stover for ethanol production has raised concerns regarding negative consequences on soil physical quality. Our objective was to quantify the impact of two tillage practices and three levels of corn stover harvest on near-surface soil physical quality through the Least Limiting Water Range (LLWR). We evaluated no harvest, moderate and high stover harvest treatments within no-tillage and chisel plow plots following seven years of continuous corn production. Forty undisturbed soil samples were taken from the 0–7.5cm deep layer within each treatment and used to determine water retention curves, soil resistance to penetration and bulk density values (Bd). No-tillage plots had higher average soil bulk density and resistance to penetration values, and were more affected by stover harvest than chisel plow plots. The results confirmed that soil resistance to penetration determined the lower limit of the LLWR regardless of tillage or stover treatment, whereas soil aeration controlled the upper limit only at Bd>1.45 and Bd>1.55Mgm−3 for chisel plow and no-tillage, respectively. The LLWR was smallest for no-tillage with moderate or high corn stover harvest, indicating poor soil physical condition for plant growth, while the largest LLWR occurred with moderate stover harvest and chisel plowing. The introduction of alfalfa (Medicago sativa L.) into an extended rotation with no-tillage improved the LLWR by reducing the potential crop growth restriction due to resistance to penetration. Although bulk density values were only occasionally higher than the critical level (Bd=1.60Mgm−3 for chisel plow and Bd=1.64Mgm−3 for no-tillage), lower soil structure quality was evident with no-tillage under moderate or high stover harvest and with chisel plowing under high stover removal. The LLWR was more sensitive than available soil water content for detecting tillage and stover harvest effects on soil structural degradation.