Tillage Regimes Research Articles

Recent yield results and trends over time with conservation tillage on clay loam and silt loam soils in southeast Norway

Yields are reported from four long-term (16–30 years) tillage trials, comparing results since 1998, under relatively wet conditions, with earlier experience. In trial 1, on clay loam, mean grain yield with spring harrowing only, has since 1998 been 87% of that obtained with autumn ploughing, whereas it was 94% for the whole period since 1991. The inclusion of autumn harrowing increased these figures to 94 and 98%, respectively. Over the last six years, spring ploughing gave 5% lower yield than did autumn ploughing. Relative yields of unploughed versus ploughed treatments were negatively correlated with summer rainfall. Grain protein was lowest with spring harrowing only. In trial 2, on clay loam, direct drilling has since 1998, as in previous years, given around 10% lower yield than has autumn ploughing. Autumn harrowing gave 4% lower yield in winter wheat and 6% higher yield in spring oats than did autumn ploughing, whilst yields of spring turnip rape were not significantly affected by tillage. In trial 3, also on clay loam, six alternative straw treatments were compared under four unploughed tillage regimes. Relative to straw removal, retaining large residue amounts depressed yields hardly at all with autumn and spring harrowing, but by 7% with spring harrowing only and by 13% with direct drilling. Overall, direct drilling gave 18% lower yields in this trial than did autumn and spring harrowing, whilst the yield reduction with spring harrowing only was 7%. In trial 4, on silt loam, both spring harrowing only and direct drilling have since 1998 given 6% lower yield than has autumn ploughing, whereas autumn and spring harrowing has given 6% higher yield. Under drier conditions during 1991–1997, autumn ploughing gave up to 11% lower yield than did unploughed treatments. Straw retention was beneficial in the absence of ploughing during that period, but has had little effect in more recent years.

Transitioning from standard to minimum tillage: Trade-offs between soil organic matter stabilization, nitrous oxide emissions, and N availability in irrigated cropping systems

Few studies address nutrient cycling during the transition period (e.g., 1–4 years following conversion) from standard to some form of conservation tillage. This study compares the influence of minimum versus standard tillage on changes in soil nitrogen (N) stabilization, nitrous oxide (N 2O) emissions, short-term N cycling, and crop N use efficiency 1 year after tillage conversion in conventional (i.e., synthetic fertilizer-N only), low-input (i.e., alternating annual synthetic fertilizer- and cover crop-N), and organic (i.e., manure- and cover crop-N) irrigated, maize–tomato systems in California. To understand the mechanisms governing N cycling in these systems, we traced 15N-labeled fertilizer/cover crop into the maize grain, whole soil, and three soil fractions: macroaggregates (>250 μm), microaggregates (53–250 μm) and silt-and-clay (<53 μm). We found a cropping system effect on soil N new (i.e., N derived from 15N-fertilizer or - 15N-cover crop), with 173 kg N new ha −1 in the conventional system compared to 71.6 and 69.2 kg N new ha −1 in the low-input and organic systems, respectively. In the conventional system, more N new was found in the microaggregate and silt-and-clay fractions, whereas, the N new of the organic and low-input systems resided mainly in the macroaggregates. Even though no effect of tillage was found on soil aggregation, the minimum tillage systems showed greater soil fraction-N new than the standard tillage systems, suggesting greater potential for N stabilization under minimum tillage. Grain-N new was also higher in the minimum versus standard tillage systems. Nevertheless, minimum tillage led to the greatest N 2O emissions (39.5 g N 2O–N ha −1 day −1) from the conventional cropping system, where N turnover was already the fastest among the cropping systems. In contrast, minimum tillage combined with the low-input system (which received the least N ha −1) produced intermediate N 2O emissions, soil N stabilization, and crop N use efficiency. Although total soil N did not change after 1 year of conversion from standard to minimum tillage, our use of stable isotopes permitted the early detection of interactive effects between tillage regimes and cropping systems that determine the trade-offs among N stabilization, N 2O emissions, and N availability.

Calculating the Effect of Soil Organic Matter Concentration on Soil Bulk Density

Soil bulk density (ρb) is required to estimate, evaluate, and calculate many physical soil properties and processes and is essential to convert data from weight‐based to volume‐ and area‐related data. One of the dominating factors changing ρb is the soil's organic matter (SOM) concentration that alters the soil's compressibility; ρb is an important soil structure attribute. Currently, no parameter for characterizing soil compactness giving directly comparable values for all soils is available. Therefore, our aim was to develop a general approach to calculate the effect of SOM concentration on ρb that would be universally valid for soils different in their genesis, compaction, and type of land use. To describe the effect of SOM on ρb mathematically, we used a nonlinear regression model that was parameterized and validated using published data from experiments where SOM concentration was the main ρb–affecting factor (long‐term fertilization and proctor experiments, wetlands, reclaimed soils, and volcanic soils). To obtain a standardized parameter describing the present compaction status of a site, we introduced the standardized bulk density sρb Mathematically, sρb is the intercept parameter of the used nonlinear regression model, and ranged between 0.7 and 2.1 Mg m−3 and was very simple to estimate. Another distinct advantage of this novel concept is that only one representative pair of ρb and SOM has to be known to calculate sρb as well as the bulk densities corresponding to other SOM concentrations measured on the site. This concept might also be helpful for identifying similar universal approaches to standardize the effect of other ρb affecting parameters (e.g., texture, soil depth, tillage regime), however, reassessed from the SOM effect.

Effect of the number of tractor passes on soil rut depth and compaction in two tillage regimes

The initially high level of soil compaction in some direct sowing systems might suggest that the impact of subsequent traffic would be minimal, but data have not been consistent. In the other hand on freshly tilled soils, traffic causes significant increments in soil compaction. The aim of this paper was to quantify the interaction of the soil cone index and rut depth induced by traffic of two different weight tractors in two tillage regimes: (a) soil with 10 years under direct sowing system and (b) soil historically worked in conventional tillage system. Treatments included five different traffic frequencies (0, 1, 3, 5 and 10 passes repeatedly on the same track). The work was performed in the South of the Rolling Pampa region, Buenos Aires State, Argentina at 34°55′S, 57°57′W. Variables measured were (1) cone index in the 0–600 mm depth profile and (2) rut depth. Tyre sizes and rut depth/tyre width ratio are particularly important respect to compaction produced in the soil for different number of passes. Until five passes of tractor (2WD), ground pressure is responsible of the topsoil compaction. Until five passes the tyre with low rut depth/tyre width ratio reduced topsoil compaction. Finally, the farmer should pay attention to the axle load, the tyre size and the soil water content at the traffic moment.

Re‐Examining the Relationship between Tillage Regime and Global Climate Change

It is known that anthropogenic greenhouse gas emissions are a major contributor to global climate change and that reducing our emissions will stem its acceleration (Baker et al., 2007). Aside from emission reductions, another method for stemming global climate change is to reduce the levels of greenhouse gases already in the atmosphere by storing them elsewhere. As the largest carbon pool within terrestrial ecosystems, the soil is thought to have considerable potential to sequester carbon. Changes in land‐use and management have been proposed to sequester atmospheric CO2, particularly converting conventional plowing to conservation tillage, especially no‐tillage (Lal, 2004). Businesses are currently allowed to purchase carbon credits for emission reductions through agricultural activities, such as soil carbon sequestration from switching to no‐tillage. However, emerging research calls into question the validity of these carbon credits. This paper focuses on the potential role of no‐till management in relation to global climate change by specifically examining the use of no‐till as a way to sequester atmospheric CO2 in the world's soils and to combat the predicted effects of global climate change on the agricultural sector.

Tillage and Nitrogen Application Methodology Impacts on Corn Grain Yield

ABSTRACT Increased fuels costs have prompted many producers to consider conservation tillage techniques and single pass applications of nitrogen (N) fertilizer and herbicide to reduce fuel expenses. The objective of this study was to determine the impacts of tillage and nitrogen application methodology on corn grain yield. The experiment was conducted from 2002–2005 at the Northwest Research Station of the Ohio Agricultural Research and Development Center (OARDC) near Hoytville, OH. Six different tillage regimes were established as main plots: no-till, fall disc-field cultivator, Aerway tool tillage, early planted strip-till, late planted strip-till, and zone deep-till. Subplots consisted of either a single-pass application of broadcast, surface applied urea-ammonoium nitrate (UAN) representing a weed ‘n’ feed application, a split application of nitrogen between planter applied and sidedress N (subsurface injected N), or an unfertilized control. The rate of N for the different application methodologies was 168 kg ha−1. Dry conditions during the 2002 growing season resulted in very poor corn yield and thus little response to tillage or N application. In 2003, the split treatment maximized corn yield likely due to minimized ammonia volatilization independent of tillage regime. Surface broadcast applications of UAN resulted in lower grain yields in conservation tillage treatments compared to split nitrogen applications in 2004. No statistical differences were noted between the two application methods in the conventional tillage treatments. In 2005, no yield differences could be attributed to N application methodology across tillage treatments. From this study it was concluded that surface broadcast application of UAN can result in yield loss, especially in conservation tillage systems.

Soil compaction produced by tractor with radial and cross-ply tyres in two tillage regimes

The aim of this paper was to quantify soil compaction induced by tractor traffic on two tillage regimes: conventional tillage and direct drilling. Traffic was simulated with one pass of a conventional 2WD tractor, using four configurations of cross-ply rear tyres: 18.4–34, 23.1–30, 18.4–38 and 24.5–32, and four configurations of radial tyres 18.4R34, 23.1R 30, 18.4R 38 and 24.5R 32, with two ballast conditions used in each configuration. The experiment was conducted in the east of the Rolling Pampa region, Buenos Aires State, Argentina at 34°25′S, 59°15′W; altitude 22 m above sea level. Rut depth after traffic and soil bulk density and cone index in a 0–450-mm profile were measured before and after traffic. Considering topsoil level, in two tillage regimes, all treatments induced significant values of soil compaction as compared to the control plot without traffic. Subsoil compaction increased as total axle load increased and was independent of ground pressure. For the same tyre configuration, radial tyre caused less soil compaction than the cross-ply.

Influence of irrigated agriculture on soil microbial diversity

Organic carbon (C), bacterial biomass and structural community diversity were measured in Southern Idaho soils with long term cropping histories. The soils tested were native sagebrush vegetation (NSB), irrigated moldboard plowed crops (IMP), irrigated conservation – chisel – tilled crops (ICT) and irrigated pasture systems (IP). Organic C concentration in soils decreased in the order NSB 0–5 cm > IP 0–30 cm = ICT 0–15 cm > IMP 0–30 cm > NSB 5–15 cm = NSB 15–30 cm. Active bacterial, fungal and microbial biomass correlated with soil C as measured by the Walkely Black method in positive curvilinear relationships ( r 2 = 0.93, 0.80 and 0.76, respectively). Amplicon length heterogeneity (LH-PCR) DNA profiling was used to access the eubacterial diversity in all soils and at all depths. The Shannon–Weaver diversity index was used to measure the differences using the combined data from three hypervariable domains of the eubacterial 16S rRNA genes. Diversity was greatest in NSB 15–30 cm soil and lowest in the IMP soil. With the exception of IMP with the lowest diversity index, the samples highest in C (NSB 0–5 cm, IP 0–30 cm, ICT 0–15 cm) reflected lower diversity indices. However, these indices were not significantly different from each other. ICT and IP increase soil C and to some extent increase diversity relative to IMP. Since soil bacteria respond quickly to environmental changes, monitoring microbial communities may be one way to assess the impact of agricultural practices such as irrigation and tillage regimes.

Satellite mapping of conservation tillage adoption in the Little River experimental watershed, Georgia

Conservation tillage is a commonly adopted best management practice for improving soil quality and reducing erosion. However, there are currently no methods in place to monitor conservation tillage adoption at the watershed scale. The primary objective of this study was to evaluate the usefulness of Landsat TM data as a tool to depict conservation tillage in a small Coastal Plain watershed. Satellite imagery was used to calculate four commonly used indices: Normalized Difference Vegetation Index, Crop Residue Cover Index, Normalized Difference Tillage Index, and the Simple Tillage Index. Ground truth data consisted of a windshield survey, assigning each site a tillage regime (conventional or conservation tillage) at 138 locations throughout the watershed and surrounding areas. A logistical regression approach was used on two subsets of the data set (<i>n</i> = 20 or <i>n</i> = 44) to determine the influence of the number of ground control points on the success of modeling the occurrence of conservation tillage. The most accurate model was re-applied to the satellite image and evaluated using an independent sample of 94 survey sites. Results indicate that the normalized difference tillage and simple tillage indices performed best, with an overall accuracy of 71% and 78% for models developed using <i>n</i> = 20 and <i>n</i> = 44 sample locations, respectively. Errors were typically in the form of commission. Results are encouraging and suggest that currently available satellite imagery can be used for rapid assessment of conservation tillage adoption using minimal a priori information.

Soil phosphorus pools for Histosols under sugarcane and pasture in the Everglades, USA

Land use changes in the Everglades Agricultural Area (EAA) in southern Florida may influence the distribution and availability of P. Cultivated soils in the EAA are being converted back to their historic use as seasonally-flooded prairies as part of Everglades restoration projects. The objectives of this study were to determine the distribution of P in soil chemical fractions in relation to long-term land management to predict P cycling and transformations for future land uses. Soil under pasture (100 yr) and planted to sugarcane ( Saccharum sp.) for 50 yr were amended with P (0, 10, 50, 150 kg P ha − 1 ), and its distribution in labile, Fe–Al bound P, Ca-bound P, humic–fulvic acid P, and residual P pools determined for surface soil (0–15 cm). Most P fertilizer entered Fe–Al and Ca-bound fractions. Cultivation contributed to higher pH and increased the Ca content in soil compared to pasture due to incorporation of bedrock limestone into soil by tillage. The land uses were differentiated by P storage in different pools. Subsequently, long-term fertilization increased soil total P for cultivated soil relative to pasture, but plant-available P constituted less than 1% of the total P. Labile P increased with increasing P application rate, ranging from 1.3 to 7.2 mg kg − 1 for cultivated soil and 1.4 to 10.7 mg kg − 1 for pasture. Most of the applied P was recovered in the Fe–Al fraction for pasture and the Ca-bound P fraction for cultivated soil. The Ca-bound P fraction represented the greatest proportion of total P for sugarcane (41%), but only 12% for pasture. The majority of P in the pasture was present in the humic–fulvic acid fraction (45%), compared to only 23% for sugarcane. The higher pH of the cultivated soil (6.8) favored retention in Ca fractions while the lower pH of pasture (5.3) favored P retention in the humic–fulvic acid fraction. The proportion of total P as organic P was greater for pasture (78%) than cultivated soil (52%). Higher P levels in more recalcitrant fractions for cultivated soils indicated that more of the applied fertilizer P was sequestered in stable fractions, which decreased P availability to crops and may subsequently increase P fertilizer requirements necessary to maintain optimal plant-available nutrient levels. Subsequently, continuation of current farming practices and tillage regimes promotes the redistribution of Ca from subsurface to surface soil, which leads to greater P sequestration in the Ca-bound fraction. However, P in inorganic fractions may be released upon onset of changes in land use. Thus, conversion to seasonally-flooded prairies may have a more dramatic effect on P release from cultivated than pasture soils since cultivated soils have more P in inorganic pools.

Satellite mapping of conservation tillage adoption in the Little River experimental watershed, Georgia

Conservation tillage is a commonly adopted best management practice for improving soil quality and reducing erosion. However, there are currently no methods in place to monitor conservation tillage adoption at the watershed scale. The primary objective of this study was to evaluate the usefulness of Landsat TM data as a tool to depict conservation tillage in a small Coastal Plain watershed. Satellite imagery was used to calculate four commonly used indices: Normalized Difference Vegetation Index, Crop Residue Cover Index, Normalized Difference Tillage Index, and the Simple Tillage Index. Ground truth data consisted of a windshield survey, assigning each site a tillage regime (conventional or conservation tillage) at 138 locations throughout the watershed and surrounding areas. A logistical regression approach was used on two subsets of the data set (<i>n</i> = 20 or <i>n</i> = 44) to determine the influence of the number of ground control points on the success of modeling the occurrence of conservation tillage. The most accurate model was re-applied to the satellite image and evaluated using an independent sample of 94 survey sites. Results indicate that the normalized difference tillage and simple tillage indices performed best, with an overall accuracy of 71% and 78% for models developed using <i>n</i> = 20 and <i>n</i> = 44 sample locations, respectively. Errors were typically in the form of commission. Results are encouraging and suggest that currently available satellite imagery can be used for rapid assessment of conservation tillage adoption using minimal a priori information.

Evaluating a crop residue cover index for determining tillage regime in a cotton-corn-peanut rotation

Conservation tillage is a well known best management practice that improves soil quality, reduces runoff and erosion, and increases infiltration. However, a rapid assessment strategy for quantifying the rate and spatial distribution of conservation tillage practices is lacking. This study was designed to evaluate the sensitivity of a remotely derived crop residue cover index for depicting conventional tillage (CT), strip tillage (ST), and no-tillage (NT) systems in a cotton-corn-peanut rotation in the southeastern Coastal Plain. Treatments consisted of CT (rip and bed operation), NT, NT with subsoiling, and ST. Remotely sensed data were acquired three times prior to canopy closure, using a handheld multispectral radiometer (485 to 1,650 nm) and thermal imager (7,000 to 14,000 nm). Using a combination of visible and near-infrared spectra, a crop residue cover index was calculated and evaluated. Results showed that crop residue cover is greatest in years planted with peanut or cotton—likely due to the later winter cover crop termination date compared to years when corn is planted. The crop residue cover index outperformed the thermal infrared, accurately separating conventional from conservation tillage treatments in four out of six data acquisitions in 2004 and 2006. Differentiation among conservation tillage treatments was inconsistent. Regression analyses showed that a strong linear relationship existed between the crop residue cover index and measured crop residue cover (<i>r</i>² = 0.51 to 0.86, alpha = 0.10). These data suggest that remotely sensed data may be used as a rapid, field-scale indicator of conservation tillage adoption. Rapid assessment methodologies are necessary to quantify the impact of conservation practice adoption on water quality/quantity, assess adoption rates, and improve the placement of conservation tillage practices at local, watershed and regional scales.

Evaluating a crop residue cover index for determining tillage regime in a cotton-corn-peanut rotation

Conservation tillage is a well known best management practice that improves soil quality, reduces runoff and erosion, and increases infiltration. However, a rapid assessment strategy for quantifying the rate and spatial distribution of conservation tillage practices is lacking. This study was designed to evaluate the sensitivity of a remotely derived crop residue cover index for depicting conventional tillage (CT), strip tillage (ST), and no-tillage (NT) systems in a cotton-corn-peanut rotation in the southeastern Coastal Plain. Treatments consisted of CT (rip and bed operation), NT, NT with subsoiling, and ST. Remotely sensed data were acquired three times prior to canopy closure, using a handheld multispectral radiometer (485 to 1,650 nm) and thermal imager (7,000 to 14,000 nm). Using a combination of visible and near-infrared spectra, a crop residue cover index was calculated and evaluated. Results showed that crop residue cover is greatest in years planted with peanut or cotton-likely due to the later winter cover crop termination date compared to years when corn is planted. The crop residue cover index outperformed the thermal infrared, accurately separating conventional from conservation tillage treatments in four out of six data acquisitions in 2004 and 2006. Differentiation among conservation tillage treatments was inconsistent. Regression analyses showed that a strong linear relationship existed between the crop residue cover index and measured crop residue cover (r2 = 0.51 to 0.86, alpha = 0.10). These data suggest that remotely sensed data may be used as a rapid, field-scale indicator of conservation tillage adoption. Rapid assessment methodologies are necessary to quantify the impact of conservation practice adoption on water quality/quantity, assess adoption rates, and improve the placement of conservation tillage practices at local, watershed and regional scales.

Effects of Irrigation Method and Tillage Regime on Peanut (Arachis hypogaea L.) Reproductive Processes

The ability of peanut gynophores to peg through cover crop residue in reduced tillage systems is a primary concern of many growers and may be hindering adoption of the practice in peanut production. The interaction between tillage and irrigation could also play a major role in final yield. Experiments were conducted during 2004 and 2005 to determine what effects tillage (conventional tillage – CT and strip tillage – ST) and irrigation method (overhead – OH and subsurface drip – SDI) had on peanut reproductive processes and if climatic conditions were correlated with the formation of reproductive structures. Counts of flowers, pegs, and pods were conducted on two time scales: every 3–4 days for six weeks during peak flowering and peg production; and season long starting at 30 days after planting and continuing until harvest. In 2004, flowers were permanently tagged and the percent and time elapsed for peg production was measured. Overall, few differences in peanut reproduction between tillage treatments were found in either 2004 or 2005. The primary difference in reproduction was a greater production of flowers in ST than CT plants in 2004, but there were no subsequent differences in pod production due to the tillage system in that same year. The peak flowering time period in 2004 for both tillage and irrigation treatments was between 19 and 23 June, while in 2005, flower production peaked around 6 July. Maximum peg and pod counts in the OH and SDI irrigation treatments in both tillage treatments occurred between 4 July and 6 July 2005. There was a significant interaction for pod production between tillage and irrigation method in 2005 and showed, on average, the SDI-CT treatment produced 2.4 pods per plant in comparison to 1.5 pods per plant in the SDI-ST treatment, indicating that the use of the two management systems together be avoided. Limited effects of climatic conditions on formation of flowers, pegs and pods were found across all tillage and irrigation treatments in both years.

Vertical distribution, size and composition of the weed seedbank under various tillage and herbicide treatments in a sequence of industrial crops

SummaryInvestigations were conducted during the 2003, 2004 and 2005 growing seasons in northern Greece to evaluate effects of tillage regime (mouldboard plough, chisel plough and rotary tiller), cropping sequence (continuous cotton, cotton–sugar beet rotation and continuous tobacco) and herbicide treatment on weed seedbank dynamics. Amaranthus spp. and Portulaca oleracea were the most abundant species, ranging from 76% to 89% of total weed seeds found in 0–15 and 15–30 cm soil depths during the 3 years. With the mouldboard plough, 48% and 52% of the weed seedbank was found in the 0–15 and 15–30 cm soil horizons, while approximately 60% was concentrated in the upper 15 cm soil horizon for chisel plough and rotary tillage. Mouldboard ploughing significantly buried more Echinochloa crus‐galli seeds in the 15–30 cm soil horizon compared with the other tillage regimes. Total seedbank (0–30 cm) of P. oleracea was significantly reduced in cotton–sugar beet rotation compared with cotton and tobacco monocultures, while the opposite occurred for E. crus‐galli. Total seed densities of most annual broad‐leaved weed species (Amaranthus spp., P. oleracea, Solanum nigrum) and E. crus‐galli were lower in herbicide treated than in untreated plots. The results suggest that in light textured soils, conventional tillage with herbicide use gradually reduces seed density of small seeded weed species in the top 15 cm over several years. In contrast, crop rotation with the early established sugar beet favours spring‐germinating grass weed species, but also prevents establishment of summer‐germinating weed species by the early developing crop canopy.

Nematode communities as bioindicators of antropogenic influence in agroecosystems

Nematode communities showed possibilities to be good indicators of different kind of disturbances in ecosystems. Some groups of nematodes can survive under disturbed environmental conditions, while others cannot. The objective of this investigation was to determine if the nematode communities in the soil could serve as bioindicators of anthropogenic activities in agroecosystems. Research was conducted in 2000, in Kneževo near Osijek. The nematode communities were investigated on three different soil treatments: Poplar forest, Arable land with standard tillage regimes – wheat, Arable land with standard tillage regimes – corn. Sampling was done using a corer O 2 cm, to a depth of 20 cm. There were 4 replicate plots of each treatment. Nematodes were extracted from 100 g subsamples of soil by the Seinhorst method (Seinhorst, 1956). Identification was done by using keys of Bongers (1994), Mai & Lyon (1975) and Andrassy (1984). Total number of nematodes and number of genera were determined and compared between treatments, as well as Maturity index (MI), Plant parasitic index (PPI) and PPI/MI (Bongers, 1990). Trophic structure was determined according to Yeates et al. 1993. Abundance of nematodes was higher in agricultural treatments in compare to treatment without human intervention (poplar). In opposite, number of genera in treatments was highest in poplar, while in agricultural soil, number of genera that survive was lower. Trophic structure analyses showed similar patterns in all treatments investigated. Five trophic groups occurred (bacterivorous, fungivorous, plant-feeding nematodes, omnivorous and predators). Plant - feeding nematodes were dominant in poplar treatment while in agricultural treatments dominated bacterial feeding nematodes followed by plant feeding nematodes. Although MI and PPI do not show statistically significant differences among treatments the trends in them do represent an effective tool as distinguishing parameters of anthropogenic influence in agro ecosystem. The obtained results provide us information that nematode communities in the soil could serve as reliable bioindicator of anthropogenic activities in agro ecosystems.

An integrated system of summer solarization and fallow tillage for Cyperus esculentus and nematode management in the southeastern coastal plain

Solarization is a form of pest control using clear plastic mulch that allows sunlight to heat the soil to temperatures lethal to plant pests. Fallow tillage is a proven practice to reduce baseline weed densities. Field trials were conducted at the Coastal Plain Experiment Station Ponder Farm from 2003 to 2006 to evaluate integrated systems of pest control using solarization and fallow tillage. Treatments included all possible combinations of four solarization regimes and three fallow tillage regimes. Solarization regimes began in either May, July, September, and included a non-solarized control. Plots were solarized using clear-colorless polyethylene mulch. Frequencies of fallow tillage were weekly and monthly using a power-tiller, and included a non-tilled control. All solarization materials were removed in early October each year and turnip green were direct seeded into the pre-existing plots. The following spring, sweet corn were seeded into pre-existing plots a second time. Solarization beginning in May or July provided excellent control of Cyperus esculentus in plots planted to turnip green and reduced densities of plant parasitic nematodes. Fallow tillage throughout the summer with a power-tiller at monthly or weekly intervals were equally effective. C. esculentus in spring planted sweet corn responded similarly. These results show that an integrated system of solarization and fallow tillage can effectively reduce populations of C. esculentus to manageable levels without the use of fumigants or herbicides, provided that the solarization period during the summer lasts at least 90 days.

Stratification of nutrients in soil for different tillage regimes and cotton rotations

Crop management practices, especially tillage and rotation, can impact soil nutrient stratification, crop growth, and yield. The objectives of this study were to determine the soil-profile distribution of plant-available nutrients in four depth intervals from 0 to 90 cm for different cotton ( Gossypium hirsutum L.) cropping systems, tillage regimes, and N fertilization rates in a south-central Texas silty clay loam soil after 5 years of treatment imposition. Distribution of nutrients in the soil profile varied between cropping systems (continuous cotton monoculture and cotton–corn ( Zea mays L.) rotation), conventional (CT) and reduced tillage (RT), and N fertilization rates (0, 80, and 160 kg N ha −1). Plant-available P showed the greatest stratification and was 426% higher at 0–15 cm than at 60–90 cm, while SO 4 had the greatest increase (42%) with depth. The percentage decrease from 0–15 to 60–90 cm was 47% and 147% for NO 3 and K, and 76%, 12%, 43%, and 232% for Mn, Fe, Cu, and Zn, respectively. In contrast, Ca and Mg concentrations increased 22% and 15%, respectively, from 0–15 to 60–90 cm. Increasing the N fertilization rate increased plant-available NO 3 and SO 4 but decreased K, Fe, Cu, and Zn concentrations. Inclusion of corn in rotation with cotton decreased plant-available Mn, Fe, and Cu from 15 to 90 cm relative to continuous cotton at 160 kg N ha −1. For unfertilized soil, rotation increased micronutrient concentrations at 15–60 cm compared to continuous cotton. On average, CT cotton–corn had significantly lower K, Ca, Mg, Na, and SO 4 concentrations than CT continuous cotton. Reduced tillage and diversified cropping systems altered the distribution of plant-available nutrients in soil relative to CT and continuous cotton. In fact, RT increased plant-available P and NO 3 in surface soil, which may have contributed to higher lint yields than CT continuous cotton.

Impact of tillage and crop rotation on light fraction and intra-aggregate soil organic matter in two Oxisols

It is well known that no-tillage (NT) practices can promote greater stocks of soil organic matter (SOM) in the soil surface layer compared to conventional tillage (CT) by enhancing the physical protection of aggregate-associated C in temperate soils. However, this link between tillage, aggregation and SOM is less well established for tropical soils, such as Oxisols. The objective of this study was to investigate the underlying mechanisms of SOM stabilization in Oxisols as affected by different crop rotations and tillage regimes at two sites in southern Brazil. Soils were sampled from two agricultural experiment sites (Passo Fundo and Londrina) in southern Brazil, with treatments comparing different crop rotations under NT and CT management, and a reference soil under native vegetation (NV). Free light fraction (LF) and intra-aggregate particulate organic matter (iPOM) were isolated from slaking-resistant aggregates. Of the total C associated with aggregates, 79–90% was found in the mineral fraction, but there were no differences between NT and CT. In contrast, tillage drastically decreased LF-C concentrations in the 0–5 cm depth layer at both sites. In the same depth layer of NT systems at Londrina, the concentrations of iPOM-C were greater when a legume cover crop was included in the rotation. At Londrina, the order of total iPOM-C levels was generally NV > NT > CT in the 0–5 cm depth interval, but the difference between NT and CT was much less than in Passo Fundo. At Passo Fundo, the greatest concentrations and differences in concentrations across tillage treatments were found in the fine (53–250 μm) iPOM fractions occluded within microaggregates. In conclusion, even though no aggregate hierarchy exists in these Oxisols, our results corroborate the concept of a stabilization of POM-C within microaggregates in no-tillage systems, especially when green manures are included in the rotation.

Phalaris minor seedbank studies: longevity, seedling emergence and seed production as affected by tillage regime

SummaryStudies were conducted to investigate seed longevity, seedling emergence and seed production of the weed Phalaris minor in wheat in northern India. The longevity of P. minor seeds buried in bags in the field was often limited to less than 1 year, although many seeds buried at 30 cm depth in a rice–wheat rotation remained viable for longer. The application of direct seeding in wheat reduced the seedling emergence rate of P. minor, when compared with conventional ploughing and sowing. However, a larger P. minor seedbank in the upper soil layer in plots under direct seeding partly reversed this positive effect in one of the two studies. Besides differences in relative distribution of weed seeds through the soil profile, it was likely that other factors such as reduced soil disturbance and soil characteristics associated with the application of direct seeding were also involved in regulating the emergence rate. Mature P. minor plants in wheat were found to invest a stable part (27%) of their aboveground biomass in seed, so that total seed weight was strongly linearly correlated with the aboveground biomass of the mother plant. Individual seed weight, however, was little affected by the weight of the mother plant.