Tillage effects on microbial biomass and nutrient distribution in soils under rain-fed corn production in central-western Mexico

Quantifying how tillage systems affect soil microbial biomass and nutrient cycling by manipulating crop residue placement is important for understanding how production systems can be managed to sustain long-term soil productivity. Our objective was to characterize soil microbial biomass, potential N mineralization and nutrient distribution in soils (Vertisols, Andisols, and Alfisols) under rain-fed corn (Zea mays L.) production from four mid-term (6 years) tillage experiments located in central-western, Mexico. Treatments were three tillage systems: conventional tillage (CT), minimum tillage (MT) and no tillage (NT). Soil was collected at four locations (Casas Blancas, Morelia, Apatzingán and Tepatitlán) before corn planting, at depths of 0–50, 50–100 and 100–150 mm. Conservation tillage treatments (MT and NT) significantly increased crop residue accumulation on the soil surface. Soil organic C, microbial biomass C and N, potential N mineralization, total N, and extractable P were highest in the surface layer of NT and decreased with depth. Soil organic C, microbial biomass C and N, total N and extractable P of plowed soil were generally more evenly distributed throughout the 0–150 mm depth. Potential N mineralization was closely associated with organic C and microbial biomass. Higher levels of soil organic C, microbial biomass C and N, potential N mineralization, total N, and extractable P were directly related to surface accumulation of crop residues promoted by conservation tillage management. Quality and productivity of soils could be maintained or improved with the use of conservation tillage.     

Long-term tillage and crop rotation effects on microbial biomass and C and N mineralization in a Brazilian Oxisol

Crop rotation and tillage impact microbial C dynamics, which are important for sequestering C to offset global climate change and to promote sustainable crop production. Little information is available for these processes in tropical/subtropical agroecosystems, which cover vast areas of terrestrial ecosystems. Consequently, a study of crop rotation in combination with no tillage (NT) and conventional tillage (CT) systems was conducted on an Oxisol (Typic Haplorthox) in an experiment established in 1976 at Londrina, Brazil. Soil samples were taken at 0–50, 50–100 and 100–200 mm depths in August 1997 and 1998 and evaluated for microbial biomass carbon (MBC) and mineralizable C and N. There were few differences due to crop rotation, however there were significant differences due to tillage. No tillage systems increased total C by 45%, microbial biomass by 83% and MBC:total C ratio by 23% at 0–50 mm depth over CT. C and N mineralization increased 74% with NT compared to CT systems for the 0–200 mm depth. Under NT, the metabolic quotient (CO₂ evolved per unit of MBC) decreased by 32% averaged across soil depths, which suggests CT produced a microbial pool that was more metabolically active than under NT systems. These soil microbial properties were shown to be sensitive indicators of long-term tillage management under tropical conditions.     

Hydraulic conductivity, residue cover and soil surface roughness under different tillage systems in semiarid conditions

The objective of this study was to investigate the effect of tillage and cropping system on near-saturated hydraulic conductivity, residue cover and surface roughness to improve soil management for moisture conservation under semiarid Mediterranean conditions. Three tillage systems were compared (subsoil tillage, minimum tillage and no-tillage) under three field situations (continuous crop, fallow and crop after fallow) on two soils (Fluventic Xerochrept and Lithic Xeric Torriorthent). Soil under no-tillage had lower hydraulic conductivity (5.0 cm day⁻¹) than under subsoil tillage (15.5 cm day⁻¹) or minimum tillage (14.3 cm day⁻¹) during 1 of 2 years in continuous crop due to a reduction of soil porosity. Residue cover at sowing was greater under no-tillage (60%) than under subsoil or minimum tillage (<10%) in continuous crop. Under fallow, residue cover was low (10%) at sowing of the following crop for all tillage systems in both soils. Surface roughness increased with tillage, with a high value of 16% and decreasing following rainfall. Under no-tillage, surface roughness was relatively low (3–4%). Greater surface residue cover under no-tillage helped conserve water, despite indications of lower hydraulic conductivity. To overcome the condition of low infiltration and high evaporation when no-till fallow is expected in a cropping sequence, either greater residue production should be planed prior to fallow (e.g. no residue harvest) or surface tillage may be needed during fallow.     

Residue management and tillage effects on soil-water storage and grain yield of dryland wheat and sorghum for a clay loam in Texas

Dryland wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor (L.) Moench) are often grown using a wheat–sorghum-fallow (WSF) crop rotation on the semiarid North American Great Plains. Precipitation stored during fallow as soil water is crucial to the success of the WSF rotation. Stubble mulch-tillage (SM) and no-tillage (NT) residue management practices reduce evaporation, but the sparse residue cover produced by dryland crops, particularly sorghum, is insufficient to reduce soil crusting and runoff. Subsoil tillage practices, e.g., paratill (PT) or sweep (ST), fracture infiltration limiting soil layers and, when used with residue management practices, may increase soil-water storage and crop growth. Our objectives were to compare the effects of PT to 0.35 m or ST to 0.10 m treatments on soil cone penetration resistance, soil-water storage, and dryland crop yield with NT and SM residue management. Six contour-farmed level-terraced watersheds with a Pullman clay loam (US soil taxonomy: fine, mixed, superactive, thermic Torrertic Paleustoll; FAO: Kastanozems) at the USDA—Agricultural Research Service, Conservation and Production Research Laboratory, Bushland, TX, USA (35°11′N, 102°5′W) were cropped as pairs using a WSF rotation so that each phase of the sequence appeared each year. In 1988, residue management plots received PT or ST every 3 years during fallow after sorghum resulting in five treatments: (i) NT–PT, (ii) NT–NOPT, (iii) NT–ST, (iv) SM–PT, and (v) SM–NOPT. Cone penetration resistance was the greatest in NT plots and reduced with PT after 12, 23, and 31 months. Mean 1990–1995 soil-water storage during fallow after wheat was greater with NT than with SM, but unaffected by PT or ST. Dryland wheat and sorghum grain yields, total water use, and water use efficiency (WUE) were not consistently increased with NT, however, and unaffected by PT or ST tillage. We conclude, for a dryland WSF rotation, that: (1) NT increased mean soil-water storage during fallow after wheat compared to SM, and (2) ST and PT “subsoil” tillage of a Pullman did not increase water storage or yield. Therefore, NT residue management was more beneficial for dryland crop production than subsoil tillage.     

Total, particulate organic matter and structural stability of a Calcixeroll soil under different wheat rotations and tillage systems in a semiarid area of Morocco

Wheat production in Morocco is constrained by both scarce climate and degraded soil quality. There is an urgent need to revert production decline while restoring country’s soils. Among conservation tillage systems known for their improvement in yield, no-till technology was found to influence soil quality as well. Soil quality indices are also affected by wheat rotations at medium and long-terms. This paper discusses changes in selected properties of a Calcixeroll soil, including total and particulate soil organic matter (SOM), pH, total N and aggregation, subjected, for 11 consecutive years, to various conservation and conventional agricultural systems. Tillage systems included no-tillage (NT) and conventional tillage (CT). Crop rotations were continuous wheat, fallow–wheat, fallow–wheat–corn, fallow–wheat–forage and fallow–wheat–lentils. Higher aggregation, carbon sequestration, pH decline and particulate organic matter (POM) buildup are major changes associated with shift from conventional- to NT system. Better stability of aggregates was demonstrated by a significantly greater mean weight diameter under NT (3.8 mm) than CT system (3.2 mm) at the soil surface. There was 13.6% SOC increase in (0–200 mm) over the 11-year period under NT, while CT did not affect much this soil quality indicator. Another valuable funding is the stratification of SOC and total nitrogen in NT surface horizon (0–25 mm) without their depletion at deeper horizon compared to tillage treatments. Fallow–wheat system resulted in reduction of SOC compared to WW, but 3-year wheat rotation tended to improve overall soil quality. Benefits from crop rotation in terms of organic carbon varied between 2.6 and 11.7%, with fallow–wheat–forage exhibiting the maximum. Combined use of NT and 3-year fallow rotation helped to improve soil quality in this experiment.     

Effects of tillage systems in dryland farming on near-surface water content during the late winter period

Tillage systems modify, at least temporarily, some of the physical properties of soil, such as soil porosity. Tillage also has an indirect effect on soil water content throughout the growth cycle, particularly in areas with a Mediterranean climate. This paper presents the results of monitoring the water content in the topsoil (0–0.20 m) of three adjacent plots during February to May cycles starting in 1994–1995 and ending in 1998–1999. Each of the plots had a surface area of 2700 m², an 8% slope and Calcic Cambisol soil. Starting in 1994, three different tillage systems were applied: conventional tillage, which is typical of the area (CT); minimum tillage (MT); and no-tillage (NT). Two vertical 200 mm TDR probes were permanently installed in each plot and measurements were taken every week. The results show that, under an NT system, the soil had significantly higher water content than the other two soil plots. However, this increased quantity of water did not denote increased crop production; on the contrary, these preliminary data point to a decrease in crop production.     

Tillage and cropping effects on soil quality indicators in the northern Great Plains

The extreme climate of the northern Great Plains of North America requires cropping systems to possess a resilient soil resource in order to be sustainable. This paper summarizes the interactive effects of tillage, crop sequence, and cropping intensity on soil quality indicators for two long-term cropping system experiments in the northern Great Plains. The experiments, located in central North Dakota, were established in 1984 and 1993 on a Wilton silt loam (FAO: Calcic Siltic Chernozem; USDA¹: fine-silty, mixed, superactive frigid Pachic Haplustoll). Soil physical, chemical, and biological properties considered as indicators of soil quality were evaluated in spring 2001 in both experiments at depths of 0–7.5, 7.5–15, and 15–30 cm. Management effects on soil properties were largely limited to the surface 7.5 cm in both experiments. For the experiment established in 1984, differences in soil condition between a continuous crop, no-till system and a crop–fallow, conventional tillage system were substantial. Within the surface 7.5 cm, the continuous crop, no-till system possessed significantly more soil organic C (by 7.28 Mg ha⁻¹), particulate organic matter C (POM-C) (by 4.98 Mg ha⁻¹), potentially mineralizable N (PMN) (by 32.4 kg ha⁻¹), and microbial biomass C (by 586 kg ha⁻¹), as well as greater aggregate stability (by 33.4%) and faster infiltration rates (by 55.6 cm h⁻¹) relative to the crop–fallow, conventional tillage system. Thus, soil from the continuous crop, no-till system was improved with respect to its ability to provide a source for plant nutrients, withstand erosion, and facilitate water transfer. Soil properties were affected less by management practices in the experiment established in 1993, although organic matter related properties tended to be greater under continuous cropping or minimum tillage than crop sequences with fallow or no-till. In particular, PMN and microbial biomass C were greatest in continuous spring wheat (with residue removed) (22.5 kg ha⁻¹ for PMN; 792 kg ha⁻¹ for microbial biomass C) as compared with sequences with fallow (SW–S–F and SW–F) (Average=15.9 kg ha⁻¹ for PMN; 577 kg ha⁻¹ for microbial biomass C). Results from both experiments confirm that farmers in the northern Great Plains of North America can improve soil quality and agricultural sustainability by adopting production systems that employ intensive cropping practices with reduced tillage management.     

Soil fertility distributions in long-term no-till, chisel/disk and moldboard plow/disk systems

In permanent no-till (NT), soil nutrients are no longer mixed into the topsoil as with moldboard plow/disking (MD), whereas chisel/disking (CD) does limited mixing. Surface broadcast and/or banded nutrient applications may result in high and low fertility zones in permanent NT, with possible implications for soil sampling and nutrient placement. We investigated effects of 25 years of continuous NT, CD and MD with corn planted in the same row locations on organic matter (SOM), pH-H₂O and Mehlich-3 extractable phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg). Vertical distribution at 0–5, 5–10 and 10–15 cm depths was measured as well as horizontal distributions across corn rows. We observed higher SOM and P in NT and CD than in MD in the 0–15 cm layer. SOM content was greatest in the top 5 cm in NT, but declined sharply with depth. SOM content in CD was not as high at the surface as in NT, but did not decline as fast as in NT. SOM was uniform but low throughout the 0–15 cm depth of MD. In all tillage systems, SOM did not vary across rows. Soil pH was higher in the 0–5 cm layer of NT than the deeper layers but the reverse was true in the CD or MD treatments. Concentrations of P, K and Ca were higher in the surface 0–5 cm than 10–15 cm depth of all tillage systems, but most strikingly in NT and CD. Starter fertilizer injection resulted in higher P and lower pH in the injection zone of all tillage treatments, but most notably in NT. The pH was depressed under the band of side-dressed nitrogen with all tillage systems. Potassium accumulated in the rows of the previous crop, probably because it leached from crop residue that accumulated there. Tillage did not affect Mg distribution. Optimal nutrient management in NT should take account of horizontal and vertical nutrient and pH distributions. Samples in long-term NT could potentially be taken to a shallower depth if calibration curves are available. To avoid underestimating P and K availability or overestimate lime needs, high P or decreased pH bands should be avoided, as well as crop rows. Possibilities to reduce P and K applications with banding need more investigation. Results show the importance of regular liming in NT to maintain surface pH in the optimum range, but also show that lime does not have to be incorporated.     

Effects of three soil tillage systems on some biological activities in an Ultisol from southern Chile

Intensive tillage for annual crop production may be affecting soil health and quality. However, tillage intensity effects on biological activities of volcanic-derived soils have not been systematically investigated. We evaluated the effects of three different tillage practices on some biological activities of an Ultisol from southern Chile during the third year of a wheat–lupin–wheat crop sequence. Treatments were: no tillage with stubble burning (NTB), no tillage without stubble burning (NT) and conventional tillage with disk-harrowing and stubble burning (CT). Biological activities were evaluated in winter and summer at 0–200 mm and at three soil depths (0–50, 50–100 and 100–200 mm) in winter. Total organic C and N were significantly higher under no-tillage systems than CT. In general, NT increased C and N of microbial biomass in comparison with CT, especially in winter. Microbial biomass C was closely associated with microbial biomass N (r = 0.986, P < 0.05); acid phosphomonoesterase (r = 0.999, P < 0.05); β-glucosidase (r = 0.978, P < 0.05), and others. Changes in biological activities occurred mainly in the upper soil layer (0–50 mm depth) in spite of the short duration of the experiment. Biological activities could be used as practical biological indicators to apply the more appropriate management systems for increasing soil sustainability or productivity.     

The influence of 12 years of tillage and crop rotation on total and labile organic carbon in a sandy loam soil

Information on which management practices can enhance soil organic matter (SOM) content and quality can be useful for developing sustainable crop production systems. We tested the influence of 12 years of no-till (NT) versus conventional tillage (CT), and four crop sequences on the organic C pools of a Grey Luvisolic sandy loam soil in northwestern Alberta, Canada. The crop sequences were: continuous wheat (Triticum aestivum L.), field pea (Pisum sativum L.)–wheat–canola (Brassica rapa L.)–wheat, red clover (Trifolium pratense L.) green manure–wheat–canola–wheat/red clover and fallow–wheat–canola–wheat. Soil samples from 1992, when the study was initiated, and 1996, 2000 and 2004 were analyzed for total organic C (TOC), the light fraction (LF) and its C content, and water-soluble and mineralizable C. Total organic C in the top 15 cm of soil was higher in the red clover rotation than either the pea or fallow rotation by 1996. The tillage effect became significant only in 2004 with NT having a higher TOC than CT. The LF dry matter (DM) increased from 6.9 g kg⁻¹ soil in 1992 to a range of 10–13 g kg⁻¹ in 2000 and 2004. It was higher under NT than CT in 2 of 3 years and in the red clover rotation than the pea or fallow rotation in 1 of 3 years. The LF C content exhibited a similar trend as LF DM. The water-soluble and mineralizable C pools were not affected by tillage but decreased with time. Among crop rotations, the red clover rotation tended to result in higher levels of hot water-soluble and mineralizable C. It is concluded that tillage had a greater influence than crop rotation on the LF DM and LF C (as indicators of C storage), whereas the converse effect applied to mineralizable C and, to a lesser degree, hot water-soluble C (as indicators of SOM quality).     

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 m² 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.     

Residue cover in wheat systems following dry pea and lentil in the Palouse region of Idaho

Crop management practices are needed that increase crop residue groundcover and reduce soil erosion after winter wheat (Triticum aestivum L.) planting in the Palouse region of northern Idaho and eastern Washington. Trials were conducted in 1997 and 1998 at the University of Idaho Kambitsch Research Farm near Genesee, Idaho, using farm scale equipment to evaluate dry pea (Pisum sativum L. subsp. sativum) and lentil (Lens culinaris Medik) residue production and groundcover across cultivars and tillage intensity. After harvest, legume plot areas were prepared for winter wheat seeding using four main plot tillage systems designed to give progressive levels of tillage intensity: no-till (NT), Ripper–Shooter™ (RS), RS plus one cultivation, and RS plus two cultivations. In 1997, the two dry pea cultivars produced significantly greater residue than the lentil cultivars. In 1998, ‘Pro 2100’ dry pea had significantly higher residue production than ‘Columbian’ pea and ‘Crimson’ lentil cultivars. In 1997, initial residue cover was highest with NT, averaging 74% groundcover across legume cultivars. After winter wheat seeding, residue cover declined for all tillage treatments, but was still highest at 40% residue cover under NT. In 1998, residue cover was lower for all tillage treatments across all cultivars than in 1997, but NT still had the highest initial residue cover. Wheat yield was not affected by tillage or previous crop treatments in either year. This study showed that NT and reduced tillage systems can maintain previous crop residue on the surface for soil conservation and subsequent crop yields.     

Soil organic carbon and fractions of a Rhodic Ferralsol under the influence of tillage and crop rotation systems in southern Brazil

Soil organic matter (SOM) and its different pools have key importance in optimizing crop production, minimizing negative environmental impacts, and thus improving soil quality. The objective of this study was to evaluate the soil C and N contents in bulk soil and in different SOM pools (light and heavy fractions) of a clayey Rhodic Ferralsol after 13 years of different tillage and crop rotations in Passo Fundo, State of Rio Grande do Sul, Brazil. Soil samples were collected from no-tillage (no soil disturbance except for sowing; NT) and conventional tillage (disc plough followed by light disc harrowings; CT) applied to wheat/soybean (W/S) and wheat/soybean–vetch/maize (W/S–V/M) rotations. As reference, soil was sampled from a non-cultivated area adjacent to the field experiment. The greatest soil C and N contents were found in non-cultivated soils in the 0–5 cm depth (45 g C kg⁻¹ soil and 3.6 g N kg⁻¹ soil). Crop cultivation led to a decrease in SOM content which was higher for CT soils (approx. 60% decrease in C and N contents) than NT soils (approx. 43% decrease in C and N contents) at 0–5 cm. Tillage had the greatest impact on soil C and N storage. Soils under NT did not contain higher C and N storage than CT soils below 5 cm depth. Significantly, higher amounts of organic carbon of FLF in CT (0.5–0.7 g C kg⁻¹ soil) than in NT soils (0.2 g C kg⁻¹ soil) at 10–20 cm depth were also observed and the differences in C and N storage between CT and NT soils in the 0–30 cm layer were not significant. Silt and clay fractions contained the largest amount of organic carbon (60–95% of total organic carbon), and free light fraction was the most sensitive pool of organic carbon to detect changes in SOM due to soil tillage and crop rotations.     

The impact of tillage and residual nitrogen on wheat

Wheat (Triticum aestivum L.) yield and quality is influenced by management of the previous crop but is highly dependent on current year management. The objective of this study was to evaluate the response of winter wheat seeded in two tillage systems [conventional tillage (CT) and no-till (NT)] to four N rates applied to a previous cotton (Gossypium hirsutum L.) crop (0, 67, 134, and 202 kg ha⁻¹). The experiment with wheat was conducted on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida North Florida Research and Education Center near Quincy, FL from 1995 to 1997. For most plant characteristics, there was a tillage x N x year interaction. Greater plant emergence (79.4 vs. 65.3%) and grain N (23.5 vs. 21.5 g kg⁻¹), and lower grain moisture (139 vs. 142 g kg⁻¹) were obtained under NT than CT, respectively, in one out of two years. Nitrogen applied to a previous cotton crop increased wheat grain yields, plant height and seed number under NT in 1995–1996 and CT in 1996–1997, head density under NT in both years, harvest index under CT in 1996–1997, and grain N concentration in 1995–1996 and 1996–1997 due to residual plant and soil N. With every 1 kg N applied to a previous cotton crop, wheat grain yields increased by 5.38 kg ha⁻¹ under NT, whereas grain yield under CT was not influenced by N application to cotton in 1995–1996. In 1996–1997, grain yields increased by 4.96 and 4.23 kg ha⁻¹ for wheat grown in NT and CT, respectively. Generally, wheat seeded in NT following cotton did not decrease stand or yields compared to CT and wheat grain yields and grain N content increased with N fertilization of the previous crop. However, we would have to apply about 134 kg N ha⁻¹ to a previous cotton crop to maximize wheat production under NT and CT.     

Tillage effects on maize yield in a Colombian savanna oxisol: Soil organic matter and P fractions

Soil organic matter (SOM) and phosphorus (P) fractions play a key role in sustaining the productivity of acid-savanna oxisols and are greatly influenced by tillage practices. In 1993, a long-term experiment on sustainable crop rotation and ley farming systems was initiated on a Colombian acid-savanna oxisol to test the effects of grain legumes, green manures, intercrops and leys as possible components that could increase the stability of systems involving annual cereal crops. Five agropastoral treatments (maize monoculture—MMO, maize–soybean rotation—MRT, maize–soybean green manure rotation—MGM, native savanna control—NSC and maize-agropastoral rotation—MAP) under two tillage systems (no till-NT and minimum tillage-MT) were investigated. The effects of NT and MT on SOM and P fractions as well as maize grain yield under the five agropastoral treatments were evaluated. Results showed that soil total C, N and P were generally better under no-till as compared to minimum-tilled soils. While P fractions were also generally higher under no-till treatments, SOM fractions did not show any specific trend. Seven years after establishment of the long-term ley farming experiment (5 years of conventional tillage followed by 2 years alternative tillage systems), MT resulted into moderately higher maize grain yields as compared to NT. The MGM rotation treatment had significantly higher values of maize yield under both tillage systems (4.2 Mg) compared to the NSC (2.3 Mg ha⁻¹). Results from this study indicate that the rotational systems (maize–soybean green manure and maize-pastures) improved the soil conditions to implement the no-till or minimum tillage systems on Colombian savanna oxisol.     

Soil management alters seedling emergence and subsequent autumn growth and yield in dryland winter wheat–fallow systems in the Central Great Plains on a clay loam soil

Stand establishment and subsequent autumn development and growth are important determinants of winter wheat (Triticum aestivum L.) yield. Soil management practices change soil properties and conditions, which alter seedling emergence, crop development and growth. Pre-plant soil management practices were studied for 6 years in a wheat–fallow rotation in eastern Colorado, USA, to isolate the impacts of pre-plant tillage (PT) and residue level on winter wheat seedling emergence and autumn development and growth. A split plot design was used with PT, using a moldboard plow that incorporated surface residue, and with no-tillage (NT). The tillage systems represented the main plots and three residue levels within each tillage treatment as subplots: no residue (0R), normal residue (1R) and twice-normal residue (2R). Residue amount had little effect on emergence or autumn growth and development. PT resulted in soil water loss from the plow zone. NT plots had more favorable soil water levels in the seeding zone which resulted in faster, more uniform and greater seedling emergence in 4 out of the 6 years. This is especially critical for stand establishment in years with low rainfall after planting. Soil or air temperature did not account for differences among treatments. Earlier and greater seedling emergence in NT treatments resulted in greater autumn development and growth. Shoot biomass, tiller density and leaf numbers were greater in NT, and again residue amount had little effect. At spring green-up, NT treatments had greater soil water in the profile. Grain yield was always equal or greater in NT than in PT, and positively correlated with earlier/greater seedling emergence and autumn growth. NT will enhance soil protection and likely increase snow catch, reduce evaporation and benefit yield in semiarid eastern Colorado.     

Tillage and crop residue management affect Vertisol properties and grain sorghum growth over seven years in the semi-arid sub-tropics. 2. Changes in soil properties

Six treatments, disc (D), blade (B) or zero (Z) tillage, each with stubble (crop residue) retained (+) or removed (−), were imposed during fallow periods between annual grain sorghum crops from June 1978 to June 1985 on a grey Vertisol in the semi-arid sub-tropics of central Queensland. Plots were neither irrigated nor fertilized. Soil profiles for chemical analysis were sampled post-harvest and pre-plant after fallow. For surface soil (0–0.1 m and sometimes also 0.1–0.2 m) during the 7 years, net decreases were measured for organic and total carbon, total nitrogen, total bicarbonate extractable and calcium chloride extractable phosphorus, total sulphur, total and exchangeable potassium. Net increases were measured for exchangeable sodium, calcium and magnesium. No net changes were found for dispersion ratios and cation exchange capacity. A net decrease in nitrate at 0.6–1.6 m began after 3 years. At 0–1.6 m, changes in pH, electrical conductivity, chloride and ammonium were negligible.

General means at 0–0.1 m decreased annually from June 1978 by 3.9% for organic carbon, 3.1% for total nitrogen, 7.5% for bicarbonate extractable phosphorus and 10.0% for calcium chloride extractable phosphorus. Decreases in organic carbon and total nitrogen had similar trends for each tillage treatment, being greater with stubble removed than with stubble retained. Decreases were least for Z+. After five years the increase in exchangeable sodium was highest for Z−. The pattern for each tillage treatment was for higher exchangeable calcium and magnesium at 0−0.1 m and higer exchangeable potassium at 0–0.02 m with stubble retained than with stubble removed. After 7 years the silt + clay dispersion ratio was lower for Z+ and Z− than for the other treatments.

There was an average net gain of 30 kg ha⁻¹ of nitrate-N at 0–0.6 m during fallow periods followed by a similar loss during cropping periods. Nitrate at the end of the fallow was equally distributed at three depths: 0–0.1, 0.1–0.2 and 0.2–0.6 m. On two occasions after a crop, the pattern was less nitrate (0–0.6 m) with stubble retained than with stubble removed, the difference for each tillage treatment increasing in the order D−1) ranged from 62 kg N ha⁻¹ for Z− to 128 kg N ha⁻¹ for Z+. The decrease for all tillage treatments was greater where stubble was retained than where it was removed. Decreases where stubble was retained were in the order D相似文献   

Response of soil physical properties to tillage and residue management on two soils in a cool temperate environment

In view of their potential benefits, reduced or no tillage (NT) systems are being advocated worldwide. Concerns about impairment of some soil conditions, however, cast doubt on their unqualified acceptance. We evaluated the effects of 6 years of tillage and residue management on bulk density, penetration resistance, aggregation and infiltration rate of a Black Chernozem at Innisfail (loam, 65 g kg⁻¹ organic matter, Udic Boroll) and a Gray Luvisol at Rimbey (loam, 31 g kg⁻¹ organic matter, Boralf) cropped to monoculture spring barley (Hordeum vulgare L.) in a cool temperate climate in Alberta, Canada. Tillage systems were no tillage and tillage with rototilling (T), and two residue levels were straw removed (−S) and straw retained (+S). Bulk density (BD) of the 0–7.5 and 7.5–15 cm depths was significantly greater under NT (1.13–1.58 Mg m⁻³) than under T (0.99–1.41 Mg m⁻³) in both soils, irrespective of residue management. In both soils, penetration resistance (PR) was greater under NT than under T to 15 cm depth. Residue retention significantly reduced PR of the 0–10 cm soil in NT, but not in T. In the 0–5 cm depth of the Black Chernozem, the >2 mm fraction of dry aggregates was highest under NT + S (72%), and lowest under T − S (50%). The wind-erodible fraction (dry aggregates <1 mm size) was smallest (18%) under NT + S and largest (39%) under T − S. Soil aggregation benefited more from NT than from residue retention. Proportion of wind-erodible aggregates was generally greater in the Gray Luvisol than in the Black Chernozem. In the Black Chernozem, steady-state infiltration rate (IR) was significantly lower (33%) under NT than under T. Residue retention improved IR in both NT and T. In the Gray Luvisol, IR was not significantly affected by tillage and residue management. Despite firmer soil, NT and residue retention are recommended to improve aggregation in the cool temperate region of Western Canada.     

Effect of tillage practices on wheat performance in a semi-arid environment

Sodosol soils are at risk of degradation under existing fallow management practices involving tillage. Topsoil erosion exposes horizons with reduced infiltration and low concentrations of plant nutrients. Conservation management systems are needed on these soils to avoid a reversion to low intensity grazing. This paper reports on a 4 year study (1986–1989) of the effects of tillage practices on profile soil water and crop yield in a Sodosol (Typic Natrustalf) in central Queensland, Australia. The tillage treatments were: zero till fallow (weed control by herbicides), reduced till fallow (chisel plough/scarifier or herbicides) and conventional till fallow (chisel plough/scarifier) in two linked experiments. In the first experiment, wheat was grown in three contour bays (approximately 1 ha), and in the second, wheat was grown in replicated plots (30 m × 6 m) to allow statistical comparisons.

Zero till provided consistent advantages in grain yield in all 4 years compared with conventional till. Zero till also outyielded reduced till as well as conventional till in the plot experiment. The average yield increase of 0.5 t ha⁻¹ in zero till compared with convention till was associated with greater water use and increased water use efficiency. Tillage practice caused only marginal differences in the available water content in the root zone (0–100 cm) at sowing; zero and reduced till contained, on average, an additional 4 and 8 mm, respectively, compared with conventional till. The tillage treatments had no effect on plant available water capacity. Some of the soil water that accumulated during the fallow drained beyond the root zone in all treatments and was not available to the following wheat crop. At the conclusion of the experiment, soil water accumulation in the 100–180 cm soil layer was 86 mm in zero till, 39 mm in reduced till and 40 mm in conventional till.

Results indicate that zero till can be a more productive wheat farming practice than conventional mechanical tillage. The increase in water storage below the root zone of the wheat crop shows that there may be benefit in using a deeper-rooting crop or pasture species in rotation with wheat, particularly after zero till fallows.     

Soil quality response to tillage and crop residue removal under subarctic conditions

Little is known about the long-term effects of tillage and crop residue management on soil quality and organic matter conservation in subarctic regions. Therefore, we quantified wet aggregate stability, bulk density, pH, total organic C and N, inorganic N, microbial biomass C and N, microbial biomass C:N ratio, microbial quotient, and potential C and N mineralization for a tillage/crop residue management study in central Alaska. Soil from no-till (NT), disked once each spring (DO), and disked twice (DT, spring and fall) treatments was sampled to 20 cm depth in spring and fall of the 16th and 17th years of the study. Crop residues were either retained or removed after harvest each year. Reducing tillage intensity had greater impact on most soil properties than removing crop residues with the most notable effects in the top 10 cm. Bulk density was the only indicator that showed significant differences for the 10–20 cm depth, with values of 0.74 Mg m⁻³ in the surface 10 cm in NT compared to 0.86 in DT and 1.22 Mg m⁻³ in NT compared to 1.31 in DT for the 10–20 cm depth. Wet aggregate stability ranged from 10% in DT to 20% in NT. Use of NT or DO conserved soil organic matter more than DT. Compared to measurements made in the 3rd and 4th years of the study, the DT treatment lost almost 20% of the soil organic matter. Retaining crop residues on the soil conserved about 650 g m⁻² greater C than removing all residues each year. Soil microbial biomass C and mineralizable C were highest in NT, but the microbial C quotient, which averaged only 0.9%, was not affected by tillage or crop residue treatment. Microbial biomass C:N ratio was 11.3 in DT and 14.4 in the NT, indicating an increasing predominance of fungi with decreasing tillage intensity. Barley grain yield, which averaged 1980 kg ha⁻¹ over the entire 17 years of the study, was highest in DO and not significantly different between NT and DT, but weeds were a serious problem in NT. Reduced tillage can improve important soil quality indicators and conserve organic matter, but long-term NT may not be feasible in the subarctic because of weed problems and build up of surface organic matter.