Effects Of Tillage Treatments Research Articles

Balancing Greenhouse Gas Emissions and Yield through Rotational Tillage in the Cold Rice-Growing Region

Tillage practices are of critical importance in maintaining soil quality on cropland and for food production, with rice cultivation representing a significant portion of the world’s food production and greenhouse gas (GHG) emissions. While numerous studies have examined the effects of reduced and no-tillage on soil GHG emissions and rice yields, the impact of adopting a rotational approach to tillage practices on the rice cultivation cycle remains uncertain. In this study, we conducted a four-year (2017–2020) field experiment in a single rice-growing area in Northeast China with the aim of investigating the effects of different tillage practices on GHG emissions from paddy fields and rice yields under full straw return conditions. We set up three experimental treatments: rotary tillage, plowing, and rotational tillage (i.e., a combination of one year of plowing and one year of rotary tillage). The results showed that averaged across all treatments, average methane (CH4, 302.6 ± 51.1 kg ha−1) and nitrous oxide (N2O, 0.86 ± 0.361 kg ha−1) emissions and rice yield (9.0 ± 0.9 t ha−1) did not exhibit significant inter-annual variability during the entire experimental period and were comparable to the average for the region. The ranking of GHG emissions during the rice-growing season was as follows: rotary tillage > plowing > rotational tillage. Across the experimental period, CH4 and N2O emissions were 9.1% and 8.5% lower in the plowing treatment and 21.2% and 13.1% lower in the rotational tillage treatment compared to the rotary tillage treatment. During the experimental period, there was no significant effect of tillage treatments on rice yield. This reduction in emissions may be attributed to changes in soil penetration resistance. In the rotational and plowing treatments, soil penetration resistance was in a range more adapted to rice growth and GHG emissions reduction compared to the rotary tillage treatment. The yield-scale GHG emission intensity was reduced by 12.7% and 26.1% in the plowing and rotational tillage treatments, respectively, in comparison to the rotary tillage treatment. This suggests that rotational tillage is a management practice that can achieve greenhouse gas emission reductions in paddy fields and stabilize or possibly increase rice yields. Consequently, the results demonstrated that a rotational alternation of multiple tillage practices is a synergistic strategy for achieving low carbon and high yield in rice in the cold rice-growing region of Northeast China.

Can a Change in Agriculture Management Practice Improve Soil Physical Properties

Soil conventional tillage has been associated with deterioration of its characteristics, while organic farming has been promoted as an approach to conserve a favorable soil environment. With the interest in nominating the tillage strategies without ploughing for maintaining long-term soil quality and subsequently increasing yields, this study set to identify if and how conservation tillage practices in organic management (OM) do improve soil physical properties compared to conventional management (CM). This study was conducted on matched field pairs in Baden-Württemberg, Germany. The conservation tillage treatment effects of OM (superficial tillage using chisel at 10 cm depth) was compared with conventional tillage practices CM (mouldboard ploughing at 30 cm depth). The field pairs were homogenous in most respects that would reflect tillage impacts. Measurements included soil infiltration capacity, saturated hydraulic conductivity, penetration resistance, and effective bulk density. Infiltration rate, measured using a hood infiltrometer at 10 parcels, was computed using Wooding’s analytical method, while Gardner’s equation was used to calculate the saturated hydraulic conductivity (Ks). The steady infiltration rate qs (h) was two times higher under OM than under CM with an average of 624 mm/h and 303 mm/h, respectively. Penetration resistances of OM were lower than under CM irrespective of the clay content. The degree of compactness (effective bulk density) was greater under CM than OM. That small change in soil compactness affects the water infiltration rate and the hydraulic properties rather than intrinsic soil matrix such as texture. Numerical model Hydrus-1D results were more representative for simulating the soil water transfer and hydraulic parameters under tillage changes.

Greenhouse Gases Emission from Rice Paddy under Different Tillage Intensity during Fallow Season

Reduced tillage is a useful practice to increase soil organic carbon (SOC) stock and decrease methane (CH4) emission in a rice paddy. However, the impacts of reduced tillage on the global warming potential (GWP) are generally analyzed for CH4 fluxes only during rice cultivation season. This study was conducted to investigate the effects of tillage on greenhouse gas (GHG) emission including both CH4 and nitrous oxide (N2O) and SOC stock changes were evaluated during the fallow season under two different tillage systems (conventional tillage and reduced tillage practice). The emission rate of GHG emissions was monitored using the closed chamber method. The SOC stock changes were estimated by the net ecosystem C budget (NECB), which is defined as the difference between total organic C input and output. Finally, the net global warming potential (net GWP), which was calculated as CO2 equivalents was compared between the different tillage system in rice paddy during fallow season. The net GWP of tillage and reduced tillage treatment were 4.09 and 4.96 Mg CO2 eq. ha-1, respectively during fallow season. However, the net GWP was not significantly different tillage systems. The decrease of SOC stock as CO2 emission was the most influential part on increasing the net GWP. Our study suggest that regardless of tillage conditions, it is necessary to establish a greenhouse gas reduction strategy focusing on increasing SOC accumulation during the fallow season. However, as this study was conducted for only single fallow season, long-term study is required to estimate the cumulative effects of tillage treatment on GHG emissions during fallow seasons in paddy.Net global warming potential (net GWP) under different tillage systems during fallow season in rice paddy (CT, conventional tillage; RT, reduced tillage).

Agricultural management affects active carbon and nitrogen mineralisation potential in soils

AbstractBackgroundSoil organic matter (SOM) is important for soil fertility and climate change mitigation. Agricultural management can improve soil fertility and contribute to climate change mitigation by stabilising carbon in soils. This calls for cost‐effective parameters to assess the influence of management practices on SOM contents.AimsThe current study aimed at understanding how sensitively the parameters active carbon (AC) and nitrogen mineralisation potential (NMP) react to different agricultural management practices compared to total organic carbon (TOC) and total nitrogen (Nt). We aimed to gain a better understanding of SOM processes, mainly regarding depth distribution and seasonality of SOM dynamics using AC and NMP.MethodsWe looked mainly at four parameters, namely permanganate oxidisable carbon (AC), nitrogen minerlaisation potential (NMP), total organic carbon (TOC) and total nitrogen (Nt). Data were obtained in five long‐term field experiments (LTEs) testing four management practices: (1) tillage, (2) compost application, (3) crop residue management, and (4) mineral fertilization.ResultsAC was specifically sensitive in detecting the effect of tillage treatment at different soil depths. NMP differentiated between all different tillage treatments in the upper soil layer, it showed the temporal dynamics between the years in the compost LTE, and it was identified as an early detection property in the crop residue LTE. Both AC and NMP detected short‐term fluctuations better than TOC and Nt over the course of two years in the crop residue LTE.ConclusionWe suggest that AC and NMP are two valuable soil biochemical parameters providing more detailed information on C and N dynamics regarding depth distribution and seasonal dynamics and react more sensitively to different agricultural management practices compared to TOC and Nt. They should be integrated in monitoring agricultural long‐term experiments (LTEs) and in field analyses conducted by farmers. However, when evaluating results towards long‐term carbon storage, their sensitivity toward annual fluctuations should be taken into account.

Sustainable Intensification of a Rice-Maize System through Conservation Agriculture to Enhance System Productivity in Southern India.

Integrated management of rice–maize systems is an emerging challenge in southern India due to improper rice residues and tillage management in maize crops. Conservation agriculture (CA) practices such as a reduced tillage and maintaining stubble mulch may hold the potential to increase yields, reduce crop establishment costs and increase farm incomes. A five-year trial was performed to study the effect of different CA and establishment methods in rice on system productivity, profitability, and soil carbon status in a rice–maize system. In the rainy season, the trial consisted of two main treatments: (i) normal manual transplanting and (ii) direct-wet seeding, and three sub-main treatments at different sowing dates with fifteen day intervals. In addition, in the winter season, two tillage treatments (conventional and minimum tillage) were imposed over the rainy season treatments. Both rice and maize were grown under irrigated conditions. The results showed that sowing times at 15 day intervals did not impact the yield significantly. Transplanted rice obtained a significantly higher grain yield during the first four years, but in the last year, the yield was similar in both of the establishment methods. In the winter season, conventional tilled maize recorded a higher cob yield than under the minimum tilled treatment, except for the last year, where both the tillage treatment effects were the same. System productivity of CA-based minimum tilled rice–maize was inferior during the first three years but was superior to the conventionally tilled method in the fourth and fifth year. Pooled analysis revealed that the conventionally tilled rice–maize system resulted in a similar system productivity as that of the CA during the study period. The cost–benefit analysis revealed that transplanted rice and conventionally tilled maize fetched higher net returns of INR 111,074 and INR 101,658/ha, respectively, over the direct-wet seeded rice and CA. In addition, the 15 July rice sown followed by the maize system led to an increase in irrigation water productivity by 15.7%, and the total water (irrigation + rainfall) productivity by 27.1% in the maize crop compared with the 30 July sown system. The CA-based rice–maize system resulted in a significantly higher very labile (0.194%) and labile (0.196%) carbon concentration at a 0–5 cm depth of soil compared to those under the conventional system. Thus, CA can be recommended for southern India and similar agro-ecological tropic and sub-tropic conditions. This system can be followed with appropriate location-specific modification in South-Asian countries, where crop yields and soil health are declining as a result of continuous cereal–cereal crop rotation.

Site position and tillage treatment effects on nitrous oxide emissions from furrow-irrigated rice on a silt-loam Alfisol in the Mid-south, USA

The development of drought-resistant hybrid rice (Oryza sativa) cultivars has allowed furrow-irrigated rice production systems to become an increasingly popular alternative to traditional flood-irrigation. However, potential environmental implications, such as greenhouse gas emissions, specifically nitrous oxide (N2O), have yet to be evaluated. This study evaluated the effects of site position (i.e., up-, mid-, and down-slope) and tillage treatment [i.e., conventional tillage (CT) and no-tillage (NT)] on N2O fluxes and season-long emissions from a furrow-irrigated rice field on a silt-loam soil (Typic Albaqualfs) in east-central Arkansas. Gas collection from closed-chambers occurred weekly over the 2018 and 2019 rice growing seasons. Nitrous oxide fluxes differed (P < 0.001) among site position-tillage treatment combinations in both growing seasons. In 2018, numeric flux maxima for all site position-tillage treatment combinations occurred at 33 days after planting (DAP). Nitrous oxide emissions in 2018 were greatest (P < 0.1) at the down-slope (3.34 kg N2O ha−1 season−1) compared to both the mid- (2.78 kg N2O ha−1 season−1) and up-slope (2.74 kg N2O ha−1 season−1), which did not differ. For both growing seasons, CT produced greater (P < 0.1) N2O emissions than NT, where mean annual emissions from CT were 3.15 and 2.58 kg N2O ha−1 season−1 for the 2018 and 2019 seasons, respectively. The evaluation of N2O fluxes and emissions from furrow-irrigated rice is essential to understanding the potential environmental impacts of furrow-irrigation as an alternative water management scheme for rice production.

A hybrid method for characterizing tillage-induced soil physical quality at the profile scale with fine spatial details

Robust methods are needed to assess tillage-induced changes in the physical quality of agricultural soils. Most soil physical quality (SPQ) evaluation procedures are based on the analysis of a limited number of soil cores randomly sampled in the soil profile. Such procedures likely fail to properly capture the spatial patterns in soil structure induced by tillage implements and vehicle traffic, resulting in a misleading SPQ diagnosis. We propose a hybrid method that couples high-resolution soil penetration resistance measurements with soil core sampling to derive high-resolution data grids of SPQ indicators encompassing the soil profile structural heterogeneity. The method builds on strong experimental relationships between soil penetration resistance and bulk density, and between bulk density and the soil hydraulic properties. We tested our method on a silt-loam soil with three tillage treatments (moldboard plowing, deep loosening with a tine cultivator, and minimum tillage), each including a zone impacted by the wheel traffic. The results allow visualization and analysis of the effect of tillage treatments and vehicle traffic on the soil SPQ indicators with a high level of spatial detail. The proposed methodology can be used to compare various soil management techniques or to monitor the temporal evolution of SPQ. As such, it can be a valuable tool to guide agricultural soil management. Furthermore, the generated high-resolution soil physical parameter grids could be used to parameterize numerical hydrodynamic models and estimate water and solute fluxes with distributed parameters representing the actual soil profile heterogeneity.

Effect of Tillage Treatments of Hairy Vetch Residues on Soil Inorganic-N Distributions and Corn Growth in a Subtropical Region

Conservation tillage has many advantages in crop production and weed control management. N-residue of hairy vetch as a green manure cover crop through tillage and no-tillage practices may increase inorganic-N level in soils and contribute to sustainable agriculture. Prior to corn cultivation, hairy vetch was cut after growing in the pots for 103 days. Six treated soils were prepared for no-tillage treatments (SRN, RN, and CN) and for tillage treatments (SRT, RT, and CT), where the soils were treated by shoot and root of hairy vetch residues, only root residues, and without application of hairy vetch as a control, respectively. Seeds of corn (Zea mays L.) were sown and grown for 56 days after sowing. The shoot and root biomasses of corn under no-tillage were higher than those of tillage. Furthermore, the shoot biomass of corn in both SRN and SRT were higher than that in other treatments. The root biomass of corn was higher in upper layers (0–5 cm depth) and deeper layers (&gt;10 cm depth) than in middle layers (5–10 cm depth) of soils. In the upper layer, the NH4-N contents of no-tillage were higher at 9 and 23 DAT than those of tillage. The NH4-N content of the soils for no-tillage in the middle layer and the deeper layer was lower than that of the CT treatment. The NO3-N content of no-tillage in the middle and deeper layers was lower than that of CT at 23 and 65 DAT. N-uptake of corn in both no-tillage and tillage treatments with hairy vetch addition was higher than that of the control.

Effects of long-term no-tillage with different straw mulching frequencies on soil microbial community and the abundances of two soil-borne pathogens

In the present study, we evaluated whether long-term no-tillage with different straw mulching frequencies (zero, once, twice and three times every three years) would affect soil microbial community composition, co-occurrence patterns, and the abundances of two pathogenic fungi (Fusarium graminearum and Fusarium moniliforme). Soil samples were collected in April, June, August and October of 2017 from a long-term tillage experimental field (initiated in 2007) in northeast China. Soil microbial community composition and pathogenic fungi abundances were determined using high-throughput sequencing and quantitative PCR, respectively. The results indicated that no-tillage and straw mulching caused significant changes in bacterial and fungal relative abundances at phylum and genus level compared with conventional tillage, and more significantly changed bacterial and fungal genera were found in the mulching treatments of twice and three times every three years, respectively. Permutational multivariate analysis of variance (PERMANOVA) showed that sampling time had a very significant effect on both bacterial and fungal communities (P < 0.01), and the effects of tillage treatment on fungal and bacterial communities were very significant (P < 0.01) and significant (P < 0.05), respectively. Moreover, no-tillage and straw mulching significantly increased fungal richness compared with conventional tillage, but the effect on bacterial diversity was not significant. The results of diversity and PERMANOVA suggested that fungi are more susceptible to tillage practices than bacteria. Furthermore, molecular ecological network analysis revealed that straw mulching reduced the complexity of both bacterial and fungal networks, but increased their ratios between positive and negative links. In addition, no-tillage and straw mulching increased the abundances of F. graminearum and F. moniliforme, especially in the mulching treatments of zero and three times every three years, which might increase the risk of maize root rot. Some soil properties and microbial genera were found to be related to the abundance changes of these two pathogenic fungi. Our research will provide some guidance for no-tillage and residue management of maize cropping in northeast China.

Effect of Tillage Treatment on the Diversity of Soil Arbuscular Mycorrhizal Fungal and Soil Aggregate-Associated Carbon Content.

No-tillage agriculture can sustain productivity and protect the environment. A comprehensive understanding of soil arbuscular mycorrhizal (AM) fungal diversity and soil carbon distribution within aggregate fractions is essential to the evaluation of no-tillage agriculture. The long-term field experiment included two tillage treatments (1) no tillage with straw returned to the soil (NTS), and (2) conventional mouldboard-plowing tillage without straw (CT), and was conducted on the Loess Plateau, north-western China, from October 2009. The soil samples were collected from the surface layer (0–20 cm depth) at the maturation stage of the summer maize (Zea mays L.) for analyzing aggregates separated by the dry-sieving method. The organic carbon content in the bulk soil and different particle size aggregates were measured using the dichromate oxidization method. The species compositions of soil AM fungi were compared by applying high-throughput sequencing of 18S rRNA. The results showed that the NTS had 9.1–12.2% higher percentage of soil macro-aggregates, resulting in 9.8% increase in mean weight diameter and 10.0% increase in bulk soil organic carbon content as compared with CT treatment. In addition, the NTS treatment had significantly higher percentages of Septoglomus and Glomus than the CT treatment. We also found some significant differences in the fungal communities of the soils of the two treatments. There was a strong positive relationship between bulk soil organic carbon and the percentages of Septoglomus and Glomus. Our results suggested that the NTS treatment had a protective effect on AM fungal community structures, which might play a key role in the development of agricultural sustainability in the Loess Plateau of China.

Assessment of long-term tillage practices on physical properties of two Ohio soils

Management practices influence soil properties in both the seasonal short-term and multi-year long-term. Seasonal changes in soil compaction were assessed at the Ohio Triplett-Van Doren No-Tillage Experimental Plots, which have been operational for more than 55 years. Soil penetration resistance (PR), carbon, and nitrogen were measured from plots under plow tillage (PT), minimum tillage (MT), and no-tillage (NT) management in Hoytville and Wooster, Ohio. Water retention curves (WRC) and pore size distribution (PSD) were evaluated at the Wooster site only. Significant tillage treatment effects on PR were observed at both sites throughout the soil profile, but varied by sampling time. In the silt loam, NT systems showed higher PR than plow treatments until below the plow depth of 20 cm, where the presence of a plow pan was seen under the PT treatment. During the summer and fall these subsurface treatment effects were no longer present. The tillage effects were more pronounced in the silty clay loam soil, where NT plots were more compacted than MT and PT treatments throughout the profile. This was observed in all the spring, summer and fall sampling surveys. There were significant tillage treatment effects (p < 0.05) on PSD at Wooster at the 0–10 and 10–20 cm soil depths. The majority of the pores for all tillage systems occurred in the 0.2–30 μm range, where the largest differences in pore distribution among tillage systems occurred. This allows the no-till treatment at Wooster to retain higher water content at most of the tensions compared with PT and MT. No-till practices increased C and N stock in the top 20 cm in Hoytville, but no differences were observed in Wooster. An historical analysis of organic carbon of the NT Wooster plots showed no significant increase in the top 10 cm from 1993-2013. However, OC did increase in the 10–30 cm depth over that 20 year period.

Effects of Subsoiling Tillage on Soil Properties, Maize Root Distribution, and Grain Yield on Mollisols of Northeastern China

Core Ideas Subsoil tillage (∼30 cm) reduced compaction and increased moisture and N availability on Mollisols. Subsoiling increased the vertical and horizontal distribution of maize roots between rows rather than in row. Grain and dry matter yield were 6.3 and 3.7% greater under subsoiling than conventional tillage. Subsoiling increased maize yield due to improved soil conditions and roots distribution. Soil compaction creates unfavorable soil physical and nutrient conditions, restrains root penetration and distribution, and reduces crop yield. A field experiment was established to assess the effects of tillage treatments on soil properties, root distribution, and grain yield of maize (Zea mays L.) on some Mollisols of Northeastern China. The two treatments included in rotary tillage (RT) and subsoiling tillage (ST). The results showed that soil bulk density, penetration resistance, soil moisture, available nitrogen content, root distribution of maize, and grain yield were significantly affected by tillage systems. Compared with RT, ST had lower soil bulk density and penetration resistance, but greater soil moisture and available nitrogen contents, especially in subsoil layer (i.e., 15‐ to 45‐ cm). The ST practice significantly increased the average root length density by 13.0% than that of RT mainly due to better vertical and horizontal distribution between the rows. Average grain yield and dry matter weight of maize increased by 693 kg ha−1 (6.3%) and 933 kg ha−1 (3.7%), respectively, under ST compared with those under RT. These data show that subsoiling tillage can loosen the soil, fracture the plow pan, increase the availability and infiltration of soil moisture and nitrogen in subsoil layers, improve the vertical and horizontal extension of maize root system in the soil, and increase grain yield on Mollisols of Northeastern China.

Bacterial and fungal communities respond differently to varying tillage depth in agricultural soils.

In arable cropping systems, reduced or conservation tillage practices are linked with improved soil quality, C retention and higher microbial biomass, but most long-term studies rarely focus on depths greater than 15 cm nor allow comparison of microbial community responses to agricultural practices. We investigated microbial community structure in a long-term field trial (12-years, Lincoln, New Zealand) established in a silt-loam soil over four depth ranges down to 30 cm. Our objectives were to investigate the degree of homogenisation of soil biological and chemical properties with depth, and to determine the main drivers of microbial community response to tillage. We hypothesised that soil microbiological responses would depend on tillage depth, observed by a homogenisation of microbial community composition within the tilled zone. Tillage treatments were mouldboard plough and disc harrow, impacting soil to ∼20 and ∼10 cm depth, respectively. These treatments were compared to a no-tillage treatment and two control treatments, both permanent pasture and permanent fallow. Bacterial and fungal communities collected from the site were not impacted by the spatial location of sampling across the study area but were affected by physicochemical changes associated with tillage induced soil homogenisation and plant presence. Tillage treatment effects on both species richness and composition were more evident for bacterial communities than fungal communities, and were greater at depths <15 cm. Homogenisation of soil and changing land management appears to redistribute both microbiota and nutrients deeper in the soil profile while consequences for soil biogeochemical functioning remain poorly understood.

Maize root morphology responses to soil penetration resistance related to tillage and drought in a clayey soil

SUMMARYCrops often experience combined soil stresses. Root responses to soil penetration resistance (PR) and drought stress can be an important basis for crop management. In 2013/14, a 2-year experiment was conducted to evaluate the effect of tillage treatment and drought stress (no irrigation for 4, 12 and 20 days during the V10–V16 growth stage) on the root length, diameter, cortex and cortical cell, and grain yield of maize (Zea mays L.) in a clayey red soil in southern China. Total root length and average root diameter were significantly correlated with soil PR and moisture. The cortical cell file number increased with soil PR and drought stress, while cortical cell size increased only with soil PR. Soil PR and moisture played different roles in maize root morphology modifications, but were both affected by tillage practices. Deep ploughing and conventional tillage increased soil moisture under severe drought stress conditions, whereas soil compaction and no-till significantly increased soil PR. The results indicate that high PR in clayey red soil was responsible for a decrease in maize root size and grain yield under drought conditions.

Comparing effects of tillage treatments performed with animal traction on soil physical properties and soil electrical resistivity: preliminary experimental results

AbstractSoil Compaction results from compressive forces applied to compressible soil by machinery wheels, combined with tillage operations. Draft animal‐pulled equipment may also cause soil compaction, but a huge gap exists on experimental data to adequately assess their impacts and, actually, animal traction is an option seen with increasing potential to contribute to sustainable agriculture, especially in mountain areas. This study was conducted to assess the impacts on soil compaction of tillage operations with motor tractor and draft animals. In a farm plot (Vale de Frades, NE Portugal) treatments were applied in sub‐plots (30 m × 3 m), consisting in a two way tillage with tractor (T), a pair of cows (C) and a pair of donkeys (D). Undisturbed soil samples (120) were taken before and after operations for bulk density (BD) and saturated hydraulic conductivity (Ks). The relative changes in BD observed after tillage in the 0-0.05 m soil depth increased after operations in all treatments. The increase was higher in the tractor sub-plot (15%) than in those where animal traction was used (8%). Before operation Ks class was rapid and fast in all samples, and after operation this value was reduced to 33% in T, whereas it reached 83% in C. Electrical Resistivity Tomography (ERT) was useful as a tool to identify the alterations caused by tillage operations on soil physical status. These preliminary results confirm the potential of animal traction as an option for mountain agri‐environments, yet it requires much wider research to soundly ground its assets.

Long term tillage treatment effects on corn grain nutrient composition and yield

Corn (Zea mays L.) grain composition is important for human and livestock nutrition, when used as seed, and for ethanol production. However, few studies have evaluated the effects of common cultural practices on corn grain composition. This study was conducted to determine whether corn grain elemental composition is affected by tillage practices (tillage or no-tillage), and whether tillage affects grain, protein, and oil yield, and removal of elements from the field in grain. The concentration of protein, oil, P, K, Ca, Mg, Mn, Fe, Zn, Cu, and B, and grain yield were determined in years 20 and 22 of long-term tillage and no-tillage treatments. Tillage treatment did not affect any grain component across both years of sampling, but Cu concentrations were greater under no-tillage in one year. Grain, oil, and protein yield was not affected by tillage treatments across years, but was greater one year under tillage and one year under no-till. The removal of P and Fe was greater under tillage in 2010, and that of Ca and Mn was greater under no-till in 2012. Removal of Cu was greater one year under tillage and one year under no-tillage. Correlation and principle components analysis suggests that there are some differences in the relationships among the grain components between tillage treatments. However, results indicate that tillage is not a dominant factor affecting corn grain composition and removals of nutrients are dominated by grain yield and not the concentration in the grain.

Short-term effects of tillage practices on soil properties under Tef [Eragrostis tef (Zucc. Trotter)] crop in northern Ethiopia

Tef crop shares the largest area of production in Ethiopia. However, its productivity is lower than 0.7tonha−1 which is mainly related to low soil fertility and moisture. An experiment was conducted using tef on Chromic Cambisols for two rainy cropping seasons (2008–2009) in northern Ethiopia. The objective was to assess the short-term effects of tillage frequencies on selected soil properties under continuous tef cropping system. The layout of the experiment was randomized complete block design using three tillage treatments, namely, conventional plowing (T1), four times plowing (T2), and reduced plowing (T3). A statistically significant (P≤0.05) effect of tillage treatments on soil moisture (SM) was determined during the experimental periods. SM was higher in T2 in both years followed by T3 in 2009. Soil physical properties (bulk density, BD; total porosity, TP; soil structural stability index, SSI) and soil nutrients (total nitrogen, TN; organic carbon, OC; cation exchange capacity, CEC; potassium, K) were significantly deteriorated by the application of T1 for consecutive two-years. The Paired-Samples T-Test showed significant improvements in these soil parameters due to T2 and T3 in 2009 as compared to the corresponded values in 2008. For example, there were significant increments in SM (11%), TP (18%), SSI (12%), TN (1.2 times), phosphorous (5%), OC (13%), and CEC (15%); but significantly decreased in OC: TN (48%) and BD (4%). Generally, despite the non-significant differences between the effects of T2 and T3, higher TP, SSI, OC, CEC; and lower BD were observed by T3 in 2009. Based on such short-term results of T3 it is possible to forecast its significant long-term effects on soil properties. Thus, for sustainable use of soil systems in the long-term due attention should be given to practice T3 as soil and water management practice in the study area conditions.

A seven-year study on the effects of fall soil tillage on yield-scaled greenhouse gas emission from flood irrigated rice in a humid subtropical climate

In southern Brazil, flood irrigated rice is grown during the summer, while a self-reseeding ryegrass is grown during the winter months without irrigation. Soil tillage operations that incorporate the rice and ryegrass residues into the soil are performed only in the spring season, which may increase methanogenesis due to higher substrate availability in reduced subsurface soil layers. It was hypothesized that anticipating the soil tillage from spring to the fall season reduces yield-scaled greenhouse gas emissions during the summer rice season due to lower availability of C compounds to methanogenic bacteria in subsurface soil layers. A seven-year study was conducted to determine soil methane (CH4) and nitrous oxide (N2O) emissions, partial global warming potential [pGWP=(CH4*25)+(N2O*298)], rice yields, and yield-scaled pGWP emissions (yield-scaled pGWP=pGWP/yield) from flood irrigated rice under spring and fall tillage treatments. No significant effect of tillage treatments on soil N2O emissions and rice yields was detected. When averaged across treatments and growing seasons (GSs), rice yield was 7.9 Mgha−1 GS−1, whereas cumulative N2O emissions were 3.65kg N2Oha−1 GS−1. Soil CH4 emissions were responsible for 91.5% of pGWP. The spring tillage treatment resulted in an earlier and larger first peak of CH4 efflux, likely due to higher labile C availability originated from the rice and ryegrass biomass decomposition in subsurface soil layers. In contrast, in the fall tillage treatment the easily decomposable compounds of the rice residue was utilized during the winter months, which combined with the ryegrass biomass kept on the soil surface resulted in lower labile C availability in subsurface soil layers. The fall tillage treatment significantly reduced cumulative CH4, pGWP and yield-scaled pGWP emissions by 24, 21, and 25%, respectively. Averaged across GSs, CH4, pGWP and yield-scaled pGWP emissions for the fall and spring tillage treatments were 316 and 417kg CH4ha−1 GS−1, 8.6 and 10.9Mg CO2eqha−1 GS−1, and 1.06 and 1.41kg CO2eqkg−1 grain, respectively. Our results indicate that shifting soil tillage operations from spring to fall can successfully mitigate yield-scaled pGWP emissions from regional flooded rice fields.

Influence of tillage practices on physical properties of a sandy loam in semi-arid region

The contrasts observed in soil tillage research studies documented the need for more research in many regions of the world if the mechanics of tillage effects on soil physical properties is to be well understood. Thus, the effect of three tillage systems: no-tillage (NT), reduce tillage (RT) and conventional tillage (CT) on the physical properties of a sandy loam soil in Maiduguri, Nigeria was investigated after 9-15 years of management. During the growing season of 2010, triplicate undisturbed core samples (5.5 cm in diameter and 4 cm height) were obtained at two soil depths (0- 15 cm and 15-30 cm), for determination of volumetric (.v) moisture content, bulk density (Bd), and total porosity (TP) of the soil at selected dates, while soil penetration resistance (PR) was determined using hand held digital penetrometer. Tillage systems significantly (p = 0.05) affected Bd and TP of the soil at two of the four sampling dates. The RT treatment recorded highest Bd and lowest TP at (0-15 cm) depth across most sampling dates, while at (15-30 cm) soil depth, the CT and RT treatments maintained higher Bd. Soil PR was significantly influenced by tillage systems only at the surface (0-15 cm) soil depth. The NT treatment recorded significantly (p = 0.05) higher PR while the RT treatment recorded the least. Further, significant (p = 0.05) tillage treatment effects on the .v content of the soil was observed at both surface (0-15 cm) and sub surface (15-30 cm) soil depths. The NT and RT treatments, on average, recorded higher values of .v relative to the CT treatment. Soil organic carbon (OC) and aggregate stability in water (MAW, ASC, DR and WSI) were found to correlate (p < 0.05) well with .v content of the soil for most sampling dates particularly a surface soil layer. The study revealed that, the NT and RT treatments promotes better physical quality of the soil relative to the CT treatment. It ishowever recommended that, other reduced tillage systems such as animal traction and ridgetillage be tried to assess their efficacy of improving soil physical quality. Key words : Tillage, Tillage systems, Soil Physical properties, Moisture storage, Physical quality

Spatial variation of penetration resistance and water content as affected by tillage and crop rotation in a black soil in Northeast China

Limited information is available for understanding the spatial variation of soil penetration resistance (SPR) and water content induced by different tillage methods and crop rotations in a black soil of Northeast China. A 11-year tillage experiment in Dehui County, Jilin Province, Northeast China was conducted to evaluate the effects of tillage treatments [no tillage (NT), moldboard plow (MP), and ridge tillage (RT)] and crop rotations (corn-soybean rotation and continuous corn) on SPR and water content in relation to horizontal and vertical variations. Effect of NT, MP, and RT differed on the spatial distributions of SPR and water content among the rows, shoulders, and inter-rows. Compared with MP, NT, and RT treatments increased SPR in row and inter-row positions at the depth of 2.5–17.5 and 2.5–15 cm, respectively (p < 0.05). NT and RT led to significant decrement of soil water content than MP treatment in the rows and inter-rows of 0–15 cm layer (p < 0.05). Greater variability of SPR and water content was found in MP than NT and RT plots. Crop rotation did not have a marked impact on SPR and water content (p > 0.05). Tillage, sampling position, along with depth greatly affected SPR and water content (p < 0.05).