Effects Of Tillage Practices Research Articles

Effect of tillage practices on structural properties and content of organic carbon in tilth soil

To further explore tillage practices for improving soil structure, the effect of different tillage practices on the structure and organic carbon of tilth soils were investigated using routine method (Wet-sieving, Potassium dichromate volumetry and Core-cutting sampling). The 7-year research was conducted at an experimental station in the semiarid Loess Plateau zone in central Gansu Province. The conservative management practices of no-tillage (NT), conventional tillage with straw incorporation (TS) and no-tillage with straw mulch (NTS) increase soil organic C and water-stable soil aggregates contents, with the highest effect under NTS tillage. Soil bulk density decreases while soil porosity increases, greatly improving soil structure under NTS in the 0~10 cm soil layer. Content of soil water-stable aggregate (1~0.5 mm) is the highest in all 3 soil layers, 0~5 cm, 5~10 cm and 10~30 cm. Soil wa- ter-stable aggregate (0.25 mm) has a significant positive correlation with soil organic C content and porosity, but is significantly negatively correlated with soil bulk density.

Effects of different soil management practices on total P and Olsen-P sediment loss: A field rainfall simulation study

Field rainfall simulations were conducted in 2002 and 2005 to study the effects of different soil management practices on the total phosphorous (TP) and Olsen-P losses by soil erosion and redistribution along a 15 m long slope in Luoyang, Henan province, China. Field plots were set up in 2001 and included the following soil management practices: subsoiling with mulch (SSM), no-till with mulch (NTM), reduced tillage (RT), and a conventional tillage control (CT). The results showed that there were no significant differences in TP and Olsen-P content in the sediment load between different plots after 6 years uniform tillage practices. The enrichment of TP and Olsen-P at the lower slope showed a clear redistribution along the slope. Effects of tillage practices on the temporal pattern of the enrichment ratio (ER) of TP and Olsen-P was not uniform. ER TP values were initially high and diminished after a short period of time and leveled to the end of the rainfall test in CT and RT plots, but remained ≥ 1. The ER of Olsen-P at the end of rainfall simulation showed a significant difference when compared to the initial stage, 0.78 to 1.60, respectively. However, the temporal loss rate of TP and Olsen-P showed a similar pattern because it was more depending on the sediment loss rate than on the concentration in the sediment. SSM resulted in 96% less TP and Olsen-P erosion loss compared to CT in 2002. Also, SSM showed the highest reduction in TP and Olsen-P loss after 4 years consistent practice. RT reduced TP and Olsen-P loss by 30%, although the runoff reduction was not significant. NTM was the best alternative with respect to TP and Olsen-P conservation, when considering its lower operational costs.

Estimation of the Runoff Curve Number via Direct Rainfall Simulator Measurements in the State of Iowa, USA

This study was the first to provide detailed methodological steps to estimate in-situ runoff curve number (CN) for selected agricultural fields in the State of Iowa via rainfall simulators. Representative fields in six counties were chosen to identify the effects of the following variables on runoff CN: rainfall intensity, soil type, soil moisture condition, tillage practice, and residue cover. The study also re-evaluated the range of the existing CN values for the different hydrologic soil groups in Iowa, and revised the equations describing the CN method to consider variables such as residue cover and soil moisture in a more detailed manner than the existing USDA method. The findings of this investigation showed that rainfall simulators are useful instruments for estimating in-situ runoff CN because rainfall intensity was adjustable during an experimental run. Further, the simulators eliminate the need of natural storm events. The range of the estimated CN values in summer agreed well (deviation less than 6%) with the reported CN values. However, the range of the estimated CN values in fall was generally less the reported CN values (deviation of about 40%) due to the high residue levels found in the fields after harvest. The effects of tillage practice and crop type were insignificant compared to residue cover and soil moisture. The study has also shown that the initial abstraction Ia is not linearly proportional to the potential maximum retention S, which agrees with the available literature.

Effects of tillage practices on soil and water phosphorus and nitrogen fractions in a Chromosol at Rutherglen in Victoria, Australia

Phosphorus (P) and nitrogen (N) exports from cropping areas can be greater than those from uncropped areas. Conservation farming methods, involving minimal tillage and full stubble retention, offer significant benefits to grain cropping, but may increase nutrient concentrations in surface (i.e. 0–20 mm) soils, resulting in increased risks of nutrient mobilisation and loss. The effects of tillage and stubble management on soil nutrients that are potentially mobilised into runoff from a long-term trial site at Rutherglen (established in 1981) were investigated. On 2 different sampling dates (February and August 2006) soils from the 0–20, 20–50, and 50–150 mm depths were collected from 3 treatments: conventional cultivation with stubble burning (CCb); direct drill with stubble burning (DDb); and direct drill with stubble retained (DDr). In 2004, the trial was sown with wheat (Triticum aestivum cv. Dollarbird), followed by faba beans in 2005 (Vicia faba L.) and wheat again in 2006. In August 2006, a rainfall simulation experiment was also conducted on these sites. All nutrient concentrations decreased with depth to 150 mm in all treatments, when both sampling dates were analysed together. This indicated that soil nutrient stratification was occurring in all 3 treatments. The CCb treatment only displayed differences between the 0–20 and 20–50 mm depths for soil organic C and ammonium-N. DDr significantly increased some nutrient concentrations in the 0–20 mm soil depth compared with the CCb treatment, including CaCl2-extractable P (0.76 and 0.50 mg/kg, for DDr and CCb, respectively), total N (1.23 and 1.00 g/kg, for DDr and CCb, respectively), and nitrate-N (12.6 and 8.63 mg/kg, for DDr and CCb, respectively), while the ammonium-N concentration was greater under CCb (9.71 mg/kg) than DDr (6.46 mg/kg). Being water-soluble, CaCl2-extractable P and nitrate-N are more likely be mobilised into streams from the 0–20 mm depth, where they are highly bioavailable and may contribute to increased eutrophication. Direct drilling with stubble retention contributed a greater proportion of particulate P and N to TP (Total P) and TN (Total N) in surface runoff than either of the burnt systems. Particulate P accounted for 75%, 67%, and 83% of TP in surface runoff from the CCb, DDb, and DDr treatments, respectively. However, the highly bioavailable dissolved reactive P (DRP) was the dominant form of dissolved P, with concentrations exceeding the recommended guidelines of 0.05 mg P/L in the lowlands of south-east Australia. Total N (0.44, 0.68, and 0.73 mg N/L for DDr, DDb, and CCb, respectively) in surface runoff was dominated by nitrate-N and also exceeded current Australian guidelines of 0.5 mg N/L, except for TN from the DDr treatment. These results would indicate that P, particularly the non-dominant but highly bioavailable form of DRP, exported from these systems is more likely to adversely affect catchment water quality than N exports. The increase in surface runoff volumes and nutrient loads from the CCb treatment observed in this study indicate that DDr systems have increased soil infiltration properties and retained nutrients within the soil–plant system. Therefore, direct drilling with stubble retention in the high rainfall zone cropping areas of north-east Victoria is more likely to retain nutrients on-site and improve soil fertility than burning stubble and cultivating the soil.

Early-Season Aerial Adult Colonization and Ground Activity of Pea Leaf Weevil (Coleoptera: Curculionidae) in Pea as Influenced by Tillage System

The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), is an important pest of pea, Pisum sativum L., in northern Idaho. Previous research revealed greater relative pea leaf weevil abundance and feeding damage in peas grown using conventional-tillage compared with no-tillage practices. However, the effects of tillage practices on early season colonization and activity by the pea leaf weevil on pea are not fully understood. Aerial traps and pitfall traps were used to assess adult colonization and relative density of adult pea leaf weevil into conventional-tillage and no-tillage pea in northern Idaho during 2005 and 2006. Feeding damage to the crop also was evaluated. During both years, aerial traps captured more pea leaf weevil in May, when crop establishment and early growth occurred, than in later months. Significantly more adult pea leaf weevils were captured in aerial traps in conventional-tillage than in no-tillage plots in May of both years. Significantly more pea leaf weevil were captured in pitfall traps in conventional-tillage plots than in no-tillage plots during the period immediately after peak aerial adult colonization in late May and early June. Crop feeding damage was significantly greater in conventional-tillage than in no-tillage plots in late May and early June. The patterns suggest that more adult pea leaf weevil colonize conventional-tillage pea than no-tillage pea. Pea plants in conventional-tillage emerged earlier and were larger than those in no-tillage during the pea leaf weevil colonization period, possibly accounting for the differences in colonization rates. This leads to greater early season pea leaf weevil infestation of conventional-tillage plots at a critical period for pea development that might ultimately influence crop yield.

Early-season aerial adult colonization and ground activity of pea leaf weevil (Coleoptera: Curculionidae) in pea as influenced by tillage system.

The pea leaf weevil, Sitona lineatus (L.) (Coleoptera: Curculionidae), is an important pest of pea, Pisum sativum L., in northern Idaho. Previous research revealed greater relative pea leaf weevil abundance and feeding damage in peas grown using conventional-tillage compared with no-tillage practices. However, the effects of tillage practices on early season colonization and activity by the pea leaf weevil on pea are not fully understood. Aerial traps and pitfall traps were used to assess adult colonization and relative density of adult pea leaf weevil into conventional-tillage and no-tillage pea in northern Idaho during 2005 and 2006. Feeding damage to the crop also was evaluated. During both years, aerial traps captured more pea leaf weevil in May, when crop establishment and early growth occurred, than in later months. Significantly more adult pea leaf weevils were captured in aerial traps in conventional-tillage than in no-tillage plots in May of both years. Significantly more pea leaf weevil were captured in pitfall traps in conventional-tillage plots than in no-tillage plots during the period immediately after peak aerial adult colonization in late May and early June. Crop feeding damage was significantly greater in conventional-tillage than in no-tillage plots in late May and early June. The patterns suggest that more adult pea leaf weevil colonize conventional-tillage pea than no-tillage pea. Pea plants in conventional-tillage emerged earlier and were larger than those in no-tillage during the pea leaf weevil colonization period, possibly accounting for the differences in colonization rates. This leads to greater early season pea leaf weevil infestation of conventional-tillage plots at a critical period for pea development that might ultimately influence crop yield.

Dissolved and Soil Organic Carbon after Long‐Term Conventional and No‐Tillage Sorghum Cropping

Distribution of dissolved (DOC) and soil organic carbon (SOC) with depth may indicate soil and crop‐management effects on subsurface soil C sequestration. The objectives of this study were to investigate impacts of conventional tillage (CT), no tillage (NT), and cropping sequence on the depth distribution of DOC, SOC, and total nitrogen (N) for a silty clay loam soil after 20 years of continuous sorghum cropping. Conventional tillage consisted of disking, chiseling, ridging, and residue incorporation into soil, while residues remained on the soil surface for NT. Soil was sampled from six depth intervals ranging from 0 to 105 cm. Tillage effects on DOC and total N were primarily observed at 0–5 cm, whereas cropping sequence effects were observed to 55 cm. Soil organic carbon (C) was higher under NT than CT at 0–5 cm but higher under CT for subsurface soils. Dissolved organic C, SOC, and total N were 37, 36, and 66%, respectively, greater under NT than CT at 0–5 cm, and 171, 659, and 837% greater at 0–5 than 80–105 cm. The DOC decreased with each depth increment and averaged 18% higher under a sorghum–wheat–soybean rotation than a continuous sorghum monoculture. Both SOC and total N were higher for sorghum–wheat–soybean than continuous sorghum from 0–55 cm. Conventional tillage increased SOC and DOC in subsurface soils for intensive crop rotations, indicating that assessment of C in subsurface soils may be important for determining effects of tillage practices and crop rotations on soil C sequestration.

Effects of Tillage Practices on Dissemination and Spatial Patterns of Heterodera glycines and Soybean Yield.

Two field experiments were conducted in central Iowa to assess the effects of tillage on Heterodera glycines dissemination and reproduction and soybean (Glycine max) yield. Plots in both experiments were artificially infested with equivalent numbers of H. glycines cysts. In one experiment, plots were left noninfested or received aggregated or uniform infestation, and a susceptible soybean cultivar was grown for 3 years. By the end of the first growing season and through the second, H. glycines population densities were consistently greater (P ≤ 0.05) in uniformly infested plots than in plots with aggregated infestations. No differences in soybean yield among the treatments were detected. In a second experiment, a 1-m2 area of each plot was infested with H. glycines cysts, susceptible soybeans were grown for four seasons, and crop residue was managed with either ridge-, conventional-, reduced-, or no-tillage. After 1 year, nematode population densities were significantly (P ≤ 0.05) greater in conventional- and reduced-tillage treatments than in no- and ridge-tillage treatments. After 2 years, H. glycines had been disseminated 6.9 m from the infestation site in conventional- and reduced-tillage treatments but only 0.5 and 1.4 m for no-tillage and ridge-tillage treatments, respectively. After 3 years, H. glycines population densities were 10 times greater in conventional- and reduced-tillage treatments than in the no-tillage treatment; conventional-tillage was the only treatment with yield significantly lower (P ≤ 0.05) than the noninfested control. Aggregation of H. glycines eggs was greater (P ≤ 0.05) in no- and ridge-tillage treatments than in conventional- and reduced-tillage treatments. Results indicate tillage can quickly disseminate H. glycines in newly infested fields, facilitating more rapid nematode reproduction and subsequent yield loss.

Dynamics of soil hydraulic properties during fallow as affected by tillage

There is limited information on the effects of tillage practices on soil hydraulic properties, especially changes with time. The objective of this study was to evaluate on a long-term field experiment the influence of conventional tillage (CT), reduced tillage (RT) and no-tillage (NT) on the dynamics of soil hydraulic properties over 3 consecutive 16–18 month fallow periods. Surface measurements of soil dry bulk density ( ρ b), soil hydraulic conductivity ( K( ψ)) at −14, −4, −1 and 0 cm pressure heads using a tension disc infiltrometer, and derived hydraulic parameters (pore size, number of pores per unit of area and water-transmission porosity) calculated using the Poiseuille's Law were taken on four different dates over the fallow period, namely, before and immediately after primary tillage, after post-tillage rains and at the end of fallow. Under consolidated structured soil conditions, NT plots presented the most compacted topsoil layer when compared with CT and RT. Soil hydraulic conductivity under NT was, for the entire range of pressure head applied, significantly lower ( P < 0.05) than that measured for CT and RT. However, NT showed the largest mean macropore size (0.99, 0.95 and 2.08 mm for CT, RT and NT, respectively; P < 0.05) but the significantly lowest number of water-conducting pores per unit area (74.1, 118.5 and 1.4 macropores per m 2 for CT, RT and NT, respectively; P < 0.05). Overall, water flow was mainly regulated by macropores even though they represented a small fraction of total soil porosity. No significant differences in hydraulic properties were found between CT and RT. In the short term, tillage operations significantly increased K ( P < 0.05) for the entire range of pressure head applied, which was likely a result of an increase in water-conducting mesopores despite a decrease in estimated mesopore diameter. Soil reconsolidation following post-tillage rains reduced K at a rate that increased with the intensity of the rainfall events.

Tillage and Crop Sequence Effects on Heterodera glycines and Soybean Yields

Conservation tillage has been increasingly used in the midwestern USA. Long‐term effects of tillage practices on the soybean [Glycine max (L.) Merr.] cyst nematode (SCN), Heterodera glycines, and soybean yields in corn–soybean rotation were studied in two fields in Minnesota (USA). The experiments were arranged in a split‐plot design with tillage treatments as main plots and crop sequences as subplots. Tillage treatments were no‐tillage (NT) and conventional tillage (CT). The crop sequences were six (Waseca) or nine (New Richland) combinations of SCN‐susceptible ‘Sturdy’, SCN‐resistant ‘Freeborn’ (‘PI 88788’ resistance source) and ‘Pioneer brand 9234’ (‘Peking’ resistance source) soybean rotated annually with corn. Tillage did not affect SCN population density at New Richland and had only minimal and inconsistent effects on SCN at Waseca. However, CT resulted in up to 370 kg ha−1 greater soybean yield than NT at Waseca. Growing SCN‐resistant cultivars was effective in the corn–soybean rotation for managing SCN and minimizing yield loss to SCN. Resistant soybean not only reduced SCN population density and increased soybean yield in the year when it was grown, but also resulted in a smaller inoculum population density and increased yield of susceptible and resistant soybean in the following soybean years. Pioneer brand 9234 was more effective than Freeborn in reducing SCN population density and increasing soybean yield in the following years. This study confirmed that use of resistant cultivars is an effective tactic for SCN management, but tillage is not an option solely for managing SCN population in the northern climate and soil conditions.

Effects of tillage practices combined with mucuna fallow on soil erosion and water dynamics on Ishigaki Island, Japan

This study was conducted on a sloping field at the Japan International Research Center for Agricultural Sciences, Okinawa Subtropical Station, Ishigaki Island, Okinawa Prefecture, Japan, to evaluate the effects of zero tillage farming combined with mucuna fallow as a cover crop on soil erosion and water dynamics. Two fallow systems (natural and mucuna) in combination with two soil tillage treatments (zero tillage and conventional tillage) were imposed on three sloping fields (2.0°, 3.5° and 5.0°). A sorghum crop (Sorghum bicolor (L) moench) was planted after the soil tillage treatment. Soil loss for zero tillage farming combined with mucuna fallow was equivalent to only 3% of that for the conventional tillage farming with natural fallow. Runoff water was also reduced by between 74% and 77% when compared with the conventional tillage system with natural fallow. These results indicate that zero tillage with mucuna fallow is a very effective measure for the control of soil erosion and water runoff. Moreover, this farming system improved water infiltration during both the fallow and the sorghum cropping periods. For the zero tillage plot, water loss as deep percolation increased 1.6-fold compared with that for the conventional farming under heavy rainfall conditions. It is expected that under less rainfall areas or seasons, the effects of zero tillage farming combined with the mucuna cover crop may be more pronounced on water runoff control and, therefore, may greatly improve soil water conditions.

Effect of tillage practices on Tilletia indica Mitra (Karnal bunt disease of wheat) in a rice–wheat rotation of the Indo-Gangetic Plains

A study was conducted to evaluate the influence of tillage systems on the incidence of Tilletia indica (Karnal bunt) in a rice–wheat system that is the most popular and prevalent crop rotation in the Indo-Gangetic Plains of India. A total of 906 samples, were drawn from the farmers’ fields during the month of April during the 3 years study period. The samples collected were 365, 171, and 370 from the zero tillage (ZT), furrow irrigated raise bed system (FIRBS), and conventional till (CT) sown fields, respectively. The disease incidence, incidence index and percent-infected samples were calculated and statistically analyzed. Results showed that ZT fields had the lowest mean incidence of Karnal bunt, i.e. 9.00% infected samples in comparison to 18.10% and 16.20% under FIRBS and CT, respectively. Similarly, the average infection in infected samples was equal in FIRBS and CT, but the samples from ZT were statistically lower. KB incidence index showed a similar trend. ZT has shown a reduced incidence of KB in comparison to the raised bed (FIRBS) and CT systems. If ZT is followed for a period of a few years, it may help in reducing the effective soil inoculum and reducing the disease incidence over time.

Effects of soil type and tillage practice on atrazine transport through intact soil cores

Agricultural systems of Argentina have increased herbicides inputs, mostly associated with adoption of no tillage (NT). Several studies have revealed presence of pesticides in groundwater. Therefore, research on the behaviour of herbicides in soils is driven by the need to manage and prevent possible contamination of groundwater. Soil organic carbon (OC) is the main soil component responsible of sorption, and consequently the main tool to reduce the leaching. However, in dynamic systems transport of organic chemicals depends on soil structural and hydraulic properties. Sorption controls the physical and biological availability of chemicals. Physical, heterogeneous flow domain, and chemical, kinetic reactions and molecular diffusion into aggregates, which are nonequilibrium processes that affect solute transport. The main objective of this paper was to evaluate the effects of soil texture and tillage system on atrazine transport through intact soil columns. The study focused on the identification of processes; and determination of parameters that control atrazine transport in the upper layer of soils. Balcarce (BAL, silty clay loam, fine, thermic, illitic, Typic Argiudoll)), Tres Arroyos (TAR, clay loam, fine, thermic, illitic, Typic Argiudoll) and Coronel Dorrego (DOR, loam, fine, thermic, mixed illitic–montmorillonitic, Typic Argiudoll) soils from the southeast of Buenos Aires Province (Argentina) were selected. The soils represent a wide range of OC content (BAL 35.5, TAR 28.8 and DOR 17.3 g kg − 1 ). At each site NT and conventional tillage (CT) systems were sampled. Four replicates of intact soils cores (15 × 8 cm) were removed from each combination of soil × tillage (BAL-NT, BAL-CT, TAR-NT, TAR-CT, DOR-NT, DOR-CT). Displacement studies were done using atrazine as the reactive solute and bromide as the nonreactive solute. Equilibrium and nonequilibrium transport models (CXTFIT 2.1) were employed to describe the breakthrough curves (BTCs). The software tool SMART was used to simulate atrazine transport under steady-state flow conditions. Atrazine BTCs were skewed to the right; exhibiting an asymmetric shape and tailing that implied nonequilibrium conditions during transport. Since physical nonequilibrium was assumed to be nearly negligible, the observed nonequilibrium was interpreted as a sorption-related process. The two-site nonequilibrium model showed an acceptable fit with the observed data (72 < R 2 < 86). Recovery percentages of atrazine in effluents were: BAL-CT 54.51%; BAL-NT 45.10%; TAR-CT 44.28%; TAR-NT 29.70%; DOR-CT 18.60%; DOR-NT 48.95%. The intraparticle diffusion model provided by SMART showed the best fit. In conclusion, intrinsic soil properties were more relevant for atrazine transport than those associated with tillage practices. However, no tillage produced early detection of atrazine in effluents, and favoured atrazine leaching in coarser soils with the lowest OC contents. However, the maximum loss of atrazine in the percolate took place in the soils with the highest OC level; with no effects of tillage practices. These soils had fine texture, and were well structured and aggregated. Intraparticle and intraorganic matter diffusion appear to be responsible for nonequilibrium sorption. Delayed sorption in aggregated soils leads to high concentration of atrazine available for leaching.

Soil water conservation and yield of winter sorghum ( Sorghum bicolor L. Moench) as influenced by tillage, organic materials and nitrogen fertilizer in semi-arid tropical India

Soil water and nutrients play an important role in increasing sorghum ( Sorghum bicolor L. Moench) yields in the Vertisols of semi-arid tropics during post-rainy season. The effects of tillage practices, organic materials and nitrogen fertilizer on soil properties, water conservation and yield of sorghum were evaluated during winter seasons of 1994–1995 and 1995–1996 on deep Vertisols at Bijapur in the semi-arid tropics of Karnataka State (Zone 3) of south India. Conservation and availability of water and nutrients during different stages of crop growth were increased by deeper tillage resulting in increased grain yield of winter sorghum. Medium and deep tillage increased the grain yield by 23% (1509 kg ha −1) and 57% (1919 kg ha −1) during 1994–1995 and 14% (1562 kg ha −1) and 34% (1835 kg ha −1) during 1995–1996, respectively, over shallow tillage. Water use efficiency increased from shallow (4.90 kg ha −1 mm −1) to deep tillage (7.30 kg ha −1 mm −1). Greater water use efficiency during 1994–1995 as compared to 1995–1996 was attributed to lower consumptive use of water during 1994–1995. Among organic materials, application of Leucaena loppings conserved larger amounts of water and increased winter sorghum yield and water use efficiency. Application of Leucaena loppings increased the winter sorghum grain yield by 9% (mean of 1994–1995 and 1995–1996) as compared to vermicompost. Significantly ( P < 0.05) higher water use efficiency of 6.32 kg ha −1 mm −1 was observed in Leucaena loppings incorporated plots compared to 5.72 kg ha −1 mm −1 from vermicompost. Grain yield increased by 245 kg ha −1 with application of 25 kg N ha −1 in 1994–1995, and a further increase in N application to 50 kg ha −1 increased the grain yield by about 349 kg ha −1 in 1995–1996. Deep tillage with application of 25 kg N ha −1 resulted in significantly higher sorghum yield (2047 kg ha −1) than control during 1994–1995. Deep tillage with integrated nutrient management (organic and inorganic N sources) conserved higher amount of soil water and resulted in increased sorghum yields especially during drought years.

Long‐Term Effects of Tillage on Soil Chemical Properties and Grain Yields of a Dryland Winter Wheat–Sorghum/Corn–Fallow Rotation in the Great Plains

Tillage systems and nutrient management influence soil chemical properties that can impact the long‐term sustainability of dryland production systems. This study was conducted to compare the effects of no‐till (NT) and conventional till (CT) on the soil chemical properties and grain yield of a dryland winter wheat (Triticum aestivum L.)–grain sorghum [Sorghum bicolor (L.) Moench]/corn (Zea mays L.)–fallow rotation. The effects of tillage practice over a 27‐yr period (1962–1989) and the effect of the conversion of CT to NT over a 14‐yr period (1989–2003) on selected soil chemical properties [pH, cation exchange capacity (CEC), base saturation (BS), soil organic C (SOC), K, Ca, Mg, and Bray‐P] at different soil depths was determined. The acidification rate of the NT treatment from 1962 to 2003 was also determined. The study was conducted at North Platte, NE on a Holdrege silt loam (fine‐silty, mixed, mesic Typic Argiustolls). In 1989, there were differences in soil chemical properties between CT and NT at some depths after 27 yr. However, in 2003, 14 yr after converting from CT to NT, there were no differences in the soil chemical properties compared with continuous NT. In 1989 and 2003, the soil chemical properties varied with soil depth. The acidification rate from 1962 to 2003 for the NT treatment in the 0‐ to 15‐cm depth was 1.3 kmol H+ ha−1 yr−1. This rate of acidification represents 38% of the total potential acidity from N fertilizer applications over 41 yr. Acidification was attributed to nitrification of ammonium‐based fertilizers and leaching of NO3− Long‐term winter wheat (1966–1983) and grain sorghum (1964–1988) grain yields were higher for NT (2718 and 4125 kg ha−1) than CT (2421 and 3062 kg ha−1). Retention of soil moisture as a result of increased residue cover under NT likely contributed to higher NT yields. Soil chemical properties in the wheat–sorghum/corn–fallow rotation will likely continue to change as a result of current management practices. Lime additions may become necessary in the future to ensure the sustainability of crop production in this system.

Tillage effects on sediment enrichment, soil quality, and crop productivity in Ethiopian Highlands

The promotion and adoption of new tillage practices requires that their potential on-site, off-site, and economic effects are acceptable. Consequently, a field experiment was conducted at Caffee Doonsa (2400 m a.s.l.; 08°57′N, 39°06′E) in the Central Highlands of Ethiopia for 6 years (1998–2003) to evaluate the effects of tillage practices on sustainable productivity and quality of the soil. Four tillage methods [broad bed and furrows (BBF), green manure (GM), ridge and furrows (RF), and reduced tillage (RT)] were arranged in a randomised complete block design with 3 replications on permanent plots (22 m by 6 m). Three crops comprising durum wheat (Triticum durum Desf.), lentil (Lens culinaries Medik), and tef (Eragrostis tef), were sown in rotation. Relative crop productivity index (RPI), financial profitability, the nutrient enrichment ratio (ER) of the eroded sediment, and soil quality index (SQI) were used as performance indicators. With its highest RPI, the use of BBF significantly increased the grain yield of lentils by 59% compared with the control, and RT resulted in the highest grain yield of wheat and tef. Economically, BBF was the most profitable option for lentils with 65% increase in gross margin, whereas RT resulted in 11% and 8% increase in that of wheat and tef, respectively. The ER indicated that the nutrient and organic matter content of the eroded sediment was always greater than that of surface soil, but there were no consistent effects associated with the treatments. The SQI showed a positive trend for GM, BBF, and RT, but differences were not statistically different at P ≤ 0.05. Overall, none of the tillage treatments was superior, but we encourage use of BBF and RT because of their positive productivity and economic trends. Further research is needed to tap the potential soil quality improvements anticipated for the GM treatment. To optimise the overall benefits, a complete system has to be developed, perhaps using BBF for lentils followed by RT for wheat and tef.

A short-term investigation of trace gas emissions following tillage and no-tillage of agroforestry residues in western Kenya

Improved-fallow agroforestry systems are increasingly being adopted in the humid tropics for soil fertility management. However, there is little information on trace gas emissions after residue application in these systems, or on the effect of tillage practice on emissions from tropical agricultural systems. Here, we report a short-term experiment in which the effects of tillage practice (no-tillage versus tillage to 15 cm depth) and residue quality on emissions of N 2O, CO 2 and CH 4 were determined in an improved-fallow agroforestry system in western Kenya. Emissions were increased following tillage of Tephrosia candida (2.1 g N 2O-N ha −1 kg N applied −1; 759 kg CO 2-C ha −1 t C applied −1; 30 g CH 4-C ha −1 t C applied −1) and Crotalaria paulina residues (2.8 g N 2O-N ha −1 kg N applied −1; 967 kg CO 2-C ha −1 t C applied −1; 146 g CH 4-C ha −1 t C applied −1) and were higher than from tillage of natural-fallow residues (1.0 g N 2O-N ha −1 kg N applied −1; 432 kg CO 2-C ha −1 t C applied −1; 14.7 g CH 4-C ha −1 t C applied −1) or from continuous maize cropping systems. Emissions from these fallow treatments were positively correlated with residue N content ( r = 0.62–0.97; P < 0.05) and negatively correlated with residue lignin content ( r = −0.56, N 2O; r = −0.92, CH 4; P < 0.05). No-tillage of surface applied Tephrosia residues lowered the total N 2O and CO 2 emitted over 99 days by 0.33 g N 2O-N ha −1 kg N applied −1 and 124 kg CO 2-C ha −1 t C applied −1, respectively; estimated to provide a reduction in global warming potential of 41 g CO 2 equivalents. However, emissions were increased from this treatment over the first 2 weeks. The responses to tillage practice and residue quality reported here need to be verified in longer term experiments before they can be used to suggest mitigation strategies appropriate for all three greenhouse gases.

Effect of Tillage Practices and Nitrogen levels on the Physical Properties of Soil

Effect of Tillage Practices and Nitrogen levels on the Physical Properties of Soil

Short-term tillage effects on soil cone index and plant development in a poorly drained, heavy clay soil

Soil compaction is a big challenge in managing poorly drained clay soils. An on-farm field study was conducted over 2 years in a poorly drained, heavy clay soil, Red River Valley, Manitoba, Canada, where soil compaction, crop growth and root development were perceived as serious concerns. To address these concerns, no-tillage and sub-soiling tillage were proposed and compared with the traditional tillage system in which light-duty field cultivators were used at tillage depths ranging from 50 to 75 mm. Measurements of soil cone index indicated that a hardpan existed at approximately 175 mm soil depth in each fall as a result of wheel traffic during the growing season. It may not be necessary to break the hardpan with fall tillage operations in the studied region, as the hardpan was naturally removed over winter. Effects of tillage practices were evaluated using seeding performance and plant development. No-tillage resulted in the similar speed of emergence, plant population and crop yield, but more uniform seeding depth and more roots in the topsoil layer (0–75 mm), when compared with the conventional tillage. Sub-soiling promoted much faster crop emergence, higher plant populations and crop yield as well as deeper root penetration than the conventional tillage. However, the draft force required for sub-soiling was four times that of the conventional tillage.

Long‐Term Tillage, Cover Crop, and Nitrogen Rate Effects on Cotton: Plant Growth and Yield Components

Cotton (Gossypium hirsutum L.) yield is influenced by tillage, cover crop, and N fertility, but the plant growth and yield component responses related to these yield responses have not been well defined. A field study was conducted from 1991 through 2001 on Gigger silt loam (fine‐silty, mixed, thermic Typic Fragidaulf) to determine the long‐term effects of tillage practices, cover crops, and N fertilization rates on cotton growth and yield components. Cotton was grown continuously without tillage (no‐till) or with surface tillage (surface till) following annual winter cover crops of wheat (Triticum aestivum L.), hairy vetch (Vicia villosa Roth), and volunteer winter vegetation in plots receiving fertilizer N rates of 0, 39, 78, 118, or 159 kg ha−1. Tillage practice, cover crop, and N rate significantly affected cotton plant height, main‐stem node number, number of nodes above white flower (NAWF), main‐stem internode length, lint fraction, percentage first harvest, individual boll weight, and boll number per square meter. Increases in lint yields were associated with increases in plant height (r = 0.73 to 0.95), node number (r = 0.71 to 0.83), internode length (r = 0.44 to 0.91), NAWF (r = 0.65 to 0.90), boll weight (r = 0.12 to 0.86), and boll number per square meter (r = 0.91 to 0.93). Lint fraction showed no association or, in some years, a negative association with lint yield (r = −0.12 to −0.70). No‐till management and optimal N rate improved the environment for plant growth, which enhanced several growth parameters and yield components that were associated with increases in yield.