Conventional Intensive Tillage Research Articles

Areas of Agrochemical Deepening Resulting from Long-Term Experiments with Fertilizers—Synthesis Following 20 Years of Annual and Stationary Fertilization

The paper hereby focuses on the essential field of soil evolution in relation to the effect of long-term fertilization on plant yields and the essential, evolutionary, and impactful changes in their fertility. NP fertilization (by application of ammonium nitrate and concentrated superphosphate) causes a change in soil reaction over time through acidification with increasing N doses, while phosphorus is able to partially mitigate this process. Acidic soil—the typical preluvosol—as a result of adsorbed acidity activation, solubilizes Al ions and may become interested in calcic amendment. Acidification tendencies are also maintained in the amended variants, but to a lesser extent due to the neutralizing capacity of the amendment and the presence of calcium ions. Complex NP fertilization in acid soil (preluvosol) cultivated with wheat can maintain a relatively constant humus content (%), but calcium amendment can cause a reduction of this indicator. In contrast, under maize, due to the effects of conventional tillage and intensive tillage, fertilization contributes to a reduction in this indicator, which is more active against the background of limestone amendment. The phenomenon can be explained by potentiation through the mineralization of the organic component of the soil. This effect is diminished in alluvial mollisol with a higher humus content, saturated in bases, and a buffering capacity. Organic and organo-mineral fertilization can control the modeling of soil humus content and its agrochemical status. The regime of essential elements (N, P, and K) becomes active in mobile forms, and the precarious supply conditions of the initial stage tend to improve. Applied superphosphate evolves, differentiated from the applied dose and pH, into non-occluded mineral forms (P-Al, P-Fe, and P-Ca), which supply the mobile forms in the soil solution for the plants, with the importance of maintaining, more of these forms at the level required by plants. In the case of potassium, the dynamics of its forms in the soil (unchangeable and exchangeable) control the soil supply state of this element and the effect of its application to plants. The data presented show that long-term experiments can effectively support the study of soil fertility through the soil-plant relationship.

Long-term experiments with fertilizers-essential fertility changes

The paper presents soil analytical data and their interpretation from samples in long-term experiments as a result of NP, NPK and organo-mineral fertiliser applications in a stationary system for 20 years and wheat-maize-soybean rotation system. The results show that NP fertilisation (from ammonium nitrate and superphosphate) leads to acidification of soils (regardless of soil type) depending on increasing N a.i./ha. The acidification phenomenon is higher in typical preluvosol (taxonomically acidic soil) due to activation of adsorbed (potential) acidity and solubilisation of Al ions, with devolatilisation of adsorbent complex, which updates for this soil the need for correction of the reaction (pH) by means of calcium amendments. In contrast, for the alluvial mollisol, with neutral - weakly alkaline pH and higher humus % and high buffering capacity, the multiannual acidification due to N is reduced. NP, NPK mineral fertilisation, in balanced doses, can maintain the organic-C and humus content constant, balanced, within the specific limits of the soil type over a period of 20 years, with wheat-maize-soybean crop rotation. In contrast, amendment and processing conventional intensive tillage (on maize) decrease the content of these indicators, a phenomenon that can be attributed to the enhanced mineralisation of the soil organic component. Organic and organo-mineral fertilisation can lead to a favourable modelling of humus content. The mobile forms of the essential elements of nutrition and fertilisation (N, P, K) are improved in terms of their bioavailability with the objective that these forms will maintain their quantity and quality at the level required by crops and their supply by fertilisation technologies is ensured rationally and preventively for the soil-plant system. In summary, the analytical results from long-term experiments with fertilisers are of direct benefit to soils, their productivity and fertility, with the implementation of sustainability principles.

Water uptake patterns of pea and barley responded to drought but not to cropping systems

Abstract. Agricultural production is under threat of water scarcity due to increasingly frequent and severe drought events under climate change. Whether a change in cropping systems can be used as an effective adaptation strategy against drought is still unclear. We investigated how plant water uptake patterns of a field-grown pea–barley (Pisum sativum L. and Hordeum vulgare L.) mixture, an important fodder intercrop, responded to experimental drought under four cropping systems, i.e. organic intensive tillage, conventional intensive tillage, conventional no tillage, and organic reduced tillage. Drought was simulated after crop establishment using rain shelters. Proportional contributions to plant water uptake from different soil layers were estimated based on stable water isotopes using Bayesian mixing models. Pea plants always took up proportionally more water from shallower depths than barley plants. Water uptake patterns of neither species were affected by cropping systems. Both species showed similar responses to the drought simulation and increased their proportional water uptake from the shallow soil layer (0–20 cm) in all cropping systems. Our results highlight the impact of drought on plant water uptake patterns for two important crop species and suggest that cropping systems might not be as successful as adaptation strategies against drought as previously thought.

Conservation Agriculture as a System to Enhance Ecosystem Services

Conservation agriculture (CA) is considered a sustainable practice with the potential to maintain or increase crop productivity and improve environmental quality and ecosystem services. It typically improves soil quality and water conservation; however, its effect on crop productivity is highly variable and dependent on local conditions/management. Crop residue retention plays a crucial role in CA and can help to improve overall soil health and ultimately crop productivity and sustainability. However, weed control, herbicide resistance, and weed shift under residue retained fields is a major challenge. Moreover, CA can increase water infiltration and reduce soil loss and runoff. This reduces the surface transport of nitrate and phosphorus from agricultural fields and the eutrophication of water bodies, although leaching of nitrate to groundwater can potentially increase. In addition, CA has been proposed as one of the components in climate-smart agriculture, owing to its reduced period to seed/plant next crop, reduced soil disturbance and low consumption of fossil fuels. Therefore, compared to the conventional intensive tillage, CA has a greater potential for soil C sequestration, favors higher soil biodiversity, lowers greenhouse gas emission, and can assist in mitigating climate change. However, not all experiments report a positive impact. The understanding and decoding the site-specific complexities of CA system is important and requires a multidisciplinary approach.

How sources of agriculture information shape the adoption of reduced tillage practices?

Abstract Public and private agricultural information sources are fundamental components that could overcome the barriers to adopting sustainable reduced tillage practices. This study aims to identify the information sources frequently used by farmers and their role in changing from conventional intensive tillage to reduced tillage practices. The study is focused on the Altai Krai region in southwestern Siberia, which faces severe soil degradation problems, pointing to an urgent need for sustainable reduced tillage practices in the area. It relied upon both quantitative and qualitative data that included a quantitative survey with 110 farm managers and qualitative, in-depth interviews with five farm managers. Descriptive statistics were used to explore farm characteristics and farmers’ actual usage of information sources. A logit model was used to estimate the role of agricultural information sources in the adoption of reduced tillage practices. Results show that the participation frequency of farm managers in trainings and workshops influences the adoption of sustainable reduced tillage practices in a statistically significant and positive way. However, the estimation results give that the frequency of expert consultations (from both private and public sources) does not influence the probability of adopting sustainable reduced tillage practices. This may be explained by the fact that farm managers received limited information about sustainable reduced tillage practices from these sources.

Comparable bacterial-mediated nitrogen supply and losses under organic reduced tillage and conventional intensive tillage

The impact of organic and conventional crop management together with two variations of conservation tillage was evaluated on N supply and losses at the end of a 4-year Swiss crop rotation. Soil samples were taken from four cropping systems: conventional intensive tillage (C-IT), conventional no tillage (C-NT), organic intensive tillage (O-IT) and organic reduced tillage (O-RT). Laboratory incubations were used to estimate rates of net mineralization, gross nitrification and potential denitrification, while quantitative PCR was used to determine copy numbers of genes of relevant enzymes in these processes. N supply via mineralization and nitrification was unaffected by cropping system. Significant decrease in bacterial ammonia oxidizer (AOB) abundance at the end of the gross nitrification incubation indicated greater responsiveness of this group for activity, in particular under conventional management. C-NT produced the highest potential denitrification, although only significantly different than C-IT. O-RT was similar to C-IT and C-NT in terms of soil N supply and N gaseous losses, meaning that added benefits through its use does not compromise plant N availability or increase N2O losses compared to conventional practices.

Conservation agriculture had a strong impact on the sub-surface soil strength and root growth in wheat after a 7-year transition period

The study compared conservation agriculture (CA) practice (no-tillage, crop residue cover on the surface and relay mung bean) with conventional intensive tillage system, in order to evaluate their effects on soil strength and water content, total porosity and pore-size distribution, roots and above-ground plant growth in wheat under a rice-wheat rotation. The experiment was started in the kharif season of the year 2010 in the research farm of the Indian Agricultural Research Institute, New Delhi, India. Observations were taken during 6th, 7th and 8th year of the rotation. The CA practice primarily reduced the sub-surface (15–30 and 30–45 cm) soil strength by 20–25% owing to 14% higher water content at this layer, and increased the total porosity (17%) and retention pores (22%). Soil aggregation and organic C improved primarily in the surface layer (0–15 cm). The modified soil physical properties led to better root growth, plant leaf area index and solar radiation interception, and higher grain and straw yields. The CA practice significantly contributed to improving the soil physical condition, especially in reducing the sub-surface compaction and improvement on root growth in wheat. This is significant in our quest to increase and sustain the rice-wheat production system in the Indian subcontinent.

Soil sealing and soil water content under no‐tillage and conventional tillage in irrigated corn: Effects on grain yield

AbstractThe main objective of this research was to analyse the effect of soil management on soil sealing and on soil water content under contrasting tillage practices and its influence on corn yield. The experimental research was carried out in a field cultivated with irrigated corn differentiated into three zones representing a gradient of soil texture (Z1, Z2, and Z3, i.e., increasingly coarser). Two plots under different soil management practices (conventional intensive tillage, CT, and no‐tillage, NT) were selected in each zone. The susceptibility to sealing of each soil and the steady infiltration rates were evaluated in the laboratory subjecting the soils to rainfall simulation applied at an intensity of 25 mm h−1. In addition, soil porosity under each treatment was quantified. Soil water content (0–90 cm depth) was determined gravimetrically at the beginning and the end of the growing cycle and at the surface (0–5 cm) during three growing seasons and continuously at two depths (5–15 and 50–60 cm) during the last growing cycle. Soil water content was simulated using the SIMPEL model, which was calibrated for the experimental conditions. Corn yield and above‐ground biomass were also analysed. Significant differences in soil sealing among zones, with decreasing soil sealing for coarser textures, and treatments were observed with infiltration rates that were near twice in NT than in CT, being the effect of soil cover significant in the reduction of soil detachment and soil losses. NT showed higher soil water content than CT, especially in the surface layers. Above‐ground biomass production was smaller in CT than in NT, and in the areas with higher sealing susceptibility was 30% to 45% smaller than in other zones, reaching the smallest values in Z1. A similar reduction in corn yield was observed between treatments being smaller in CT than in NT. No‐tillage has been confirmed as an effective technique that benefits soil physical properties as well as crop yields in relation to CT, being its impact greater in soils susceptible to sealing.

Soil hydraulic response to conservation agriculture under irrigated intensive cereal-based cropping systems in a semiarid climate

Assessment of soil hydraulic response to conservation agriculture (CA) practices may assist in better management decisions in agriculturally sensitive and environmentally fragile agroecosystems. Although, the potential of management induced temporal changes of soil hydraulic properties (SHPs) has been studied particularly in relation to tillage, few studies have evaluated combined effects of tillage, crop residue retention and cropping sequence, which are essential components of CA, on near-saturated SHPs under field conditions. The objective of this study was thus to evaluate the long-term effect after eight years of CA practices and short-term effect of crops on near-saturated soil hydraulic conductivity, k(h), and water transmission properties under irrigated intensive cereal-based cropping systems in a semiarid climate (NW Indo-Gangetic Plains, India). There were four treatments: (1) conventionally tilled rice-wheat cropping system, (2) reduced till CA-based rice-wheat-mungbean system, (3) no-till CA-based rice-wheat-mungbean system and (4) no-till CA-based maize-wheat-mungbean system. Steady state infiltration rates were obtained at four pressure heads by hood infiltrometer consecutively over two cropping seasons, i.e., during harvest season of rice/maize (October 2017) and maximum crop growth stage of wheat (February 2018). Data were analysed in terms of k(h), flow weighted mean pore radius (r0), hydraulically active porosity (ε) and threshold pore radius (rbp), a new pore measure indicative of macropore stability derived by substituting soil’s bubble pressure in the capillary equation. Our results showed that no till-based CA enhanced k(h) as compared with conventional cultivation practice. Although the interaction effect of treatments with crop seasons were statistically non-significant (p < 0.05), considerable changes of soil hydraulic properties were observed over crop seasons under CA treatments. Transition from maize to wheat in the crop sequence reduced k(h) values by about 55, 44, 34 and 40% at pressure heads of 0, −1, −2 and −4 cm, respectively. In contrast, transition from rice to wheat in rice-based no till CA increased k(h) values by 129, 164, 124 and 24% in the same pressure head ranges. Irrespective of crop seasons, higher k(h) was observed under CA due to formation of macropores with better continuity, greater size and numbers as compared with conventional intensive tillage treatment. Reduced till-based CA showed an intermediate effect with respect to the different soil hydraulic characteristics in both crop seasons. Moreover, higher r0 values were observed for a given k(h) for CA treatments suggesting that interaggregate pores are the dominant pathways of infiltration flux in CA. A relatively smaller temporal variation of rbp was indicative of a more stable macropore system established by rice-based CA as compared with maize-based CA. CA also enhanced hydraulically active macropores as compared with intensive tillage based conventional agriculture. Overall, the results revealed that the potential impacts of CA on near-saturated SHPs are largely governed by characteristic changes in macro- and interaggregate pores.

Impact of conservation tillage and nitrogen on sugarbeet yield and quality

Conventional intensive tillage (CT) is widely practiced in sugarbeet (Beta vulgaris L.) growing regions. However, CT uses more labor and machinery and has negative impacts on soil and environment. Limited information exists for the performance of sugarbeet in reduced tillage compared to CT systems. A three-year field experiment was conducted to evaluate yield and quality of sugarbeet under no-till (NT), and strip-till (ST) systems compared to CT. The response of sugarbeet to the increasing rate of nitrogen (N) from 56 to 224 kg ha−1 in each tillage system was also studied. Sugarbeet plant stand, root yield, root impurities (sodium, potassium, and amino-N concentration in the root), sucrose loss to molasses (SLM) and recoverable sucrose yield were measured. Tillage had no significant effect on plant stand, root yield, and recoverable sucrose yield. The estimated cost of tillage operation showed that growing sugarbeet under NT was 111 US$ ha−1 less than that in CT, which could be translated into 111 US$ ha−1 higher net benefit for growers considering the similar yields in both systems. Sugarbeet root yield linearly increased in response to increasing rate of N, however, sucrose concentration decreased and root impurities increased with increasing N input. Overall, little increase of recoverable sucrose yield was observed with N rate increasing from 56 to 224 kg ha−1. Response to N rate occurred irrespective of tillage method.

Effects of N Fertilizer Sources and Tillage Practices on NH3 Volatilization, Grain Yield, and N Use Efficiency of Rice Fields in Central China.

Tillage practices and nitrogen (N) sources are important factors affecting rice production. Few studies, however, have examined the interactions between tillage practices and N fertilizer sources on NH3 volatilization, nitrogen use efficiency (NUE), and rice grain yield. This study aimed to investigate the effects of N fertilizer sources (no N fertilizer, inorganic N fertilizer, organic N fertilizer alone, organic N fertilizer plus inorganic N fertilizer, and slow-release N fertilizer plus inorganic N fertilizer) and tillage practices (no-tillage [NT] and conventional intensive tillage [CT]) on NH3 flux, grain yield, and NUE in the rice field of central China. N sources significantly affected NH3 volatilization, as the cumulative volatilization from the treatments of inorganic N fertilizer, organic N fertilizer, organic N fertilizer plus inorganic N fertilizer, slow-release N fertilizer plus inorganic N fertilizer was 4.19, 2.13, 3.42, and 2.23 folds in 2013, and 2.49, 1.68, 2.08, and 1.85 folds in 2014 compared with that under no N fertilizer treatment, respectively. The organic N fertilizer treatment had the lowest grain yield and NUE among all N fertilizer treatments, while slow-release N fertilizer plus inorganic N fertilizer treatment led to relatively higher grain yield and the greatest N use efficiency. Moreover, NT only markedly increased NH3 volatilization from basal fertilizer by 10–14% in average compared with CT, but had no obvious effects on total volatilization during the whole seasons. Tillage practices had no significant effects on grain yield and NUE. Our study suggested that the combination of slow-release N fertilizer plus inorganic N fertilizer and NT might be a sustainable method for mitigating greenhouse gas and NH3 emissions and improving grain yield and NUE in paddy fields of central China.

Improvement of soil structure through organic crop management, conservation tillage and grass-clover ley

Conventional intensive tillage is a widespread soil management practice that controls weeds and promotes nutrient mineralization at the expense of a degraded soil structure and soil carbon (C) loss. Alternative soil management practices such as no tillage, reduced tillage and temporary leys, however, can minimize the negative effects of intensive tillage on soil structure. To improve understanding of these management practices on soil structure, we sampled a field trial combining organic and conventional crop management with different intensity levels of tillage, resulting in four cropping systems: conventional intensive tillage (C-IT), conventional no tillage (C-NT), organic intensive tillage (O-IT) and organic reduced tillage (O-RT). A ley period was added following a 4-year arable crop rotation. We measured mean weight diameter (MWD), total C and total nitrogen (N) in whole unfractionated soil and water-stable aggregate fractions after the 4-year arable crop rotation and again after a following 2-year grass-clover ley period, to assess the impact of the cropping system and the ley, respectively. Results showed that 4 years of organic crop management including the application of cattle manure slurry combined with reduced tillage led to significantly better soil structure (i.e. aggregate MWD) at the 0–6 cm soil depth, compared to the other cropping systems tested. After the ley period, the proportion of large macroaggregates increased by 65% for C-IT and 47% for O-IT at 0–6 cm depth. Total C increased significantly for only O-IT and O-RT after the ley, both of which also showed a high C stratification between 0–6 cm and 6-20 cm depth. In conclusion, soil structure is most improved during continuous cropping when combining organic crop management with reduced tillage, while a ley period was effective in improving the soil structure in intensive tillage plots to the level of O-RT.

Conservation Agriculture Had a Poor Impact on the Soil Porosity of Veneto Low‐lying Plain Silty Soils after a 5‐year Transition Period

AbstractConservation agriculture practices have been proposed as a set of techniques for improving soil structure properties and related ecosystem services. This study compared conservation agriculture (CA) practices (no‐tillage, cover crop and residue retention) and conventional intensive tillage system in order to evaluate their effects on total porosity, pore size distribution, pore architecture and morphology. The experiment was set up in 2010 on four farms of the low‐lying Veneto Region plain characterized by silty soils. Almost hundred soil samples were collected in 2015 at four depths down to 50‐cm layer and investigated for porosity from micrometre (0·0074 μm) to macrometre (2·5 mm) by coupling mercury intrusion porosimetry and X‐ray computed microtomography (μCT). Indices of soil morphology and architecture were derived by analysing 3D images and mercury intrusion porosimetry pore size curves. Results suggested that silty soils of Veneto plain are microstructured because much (82%) of the porosity ranged between 0·0074 and 30 μm. CA practices positively influenced the ultramicroporosity class (0·1–5 μm) (1·86E‐01 vs 1·67E‐01 μm3 μm−3) that is strictly linked to soil organic carbon stabilization while no effects were observed in X‐ray μCT porosity domain (&gt; 26 μm). Silty soils of Veneto plain showed a slow reaction to CA because of the poor aggregate stability and low soil organic carbon. However, the positive response of the ultramicropore fraction indicates that a virtuous cycle was initiated between soil organic carbon and porosity, hopefully leading to well‐developed macropore systems and, in turn, enhanced soil functions and ecosystem services. Copyright © 2017 John Wiley &amp; Sons, Ltd.

Challenges of conservation agriculture practices on silty soils. Effects on soil pore and gas transport characteristics in North-eastern Italy

Soil air exchange is one of the most important soil functions that directly impacts on crop productivity and environment. Generally, conservation agriculture (CA) practices are expected to provide improved soil aeration but contrasting texture-related effects were found in the literature. The aim of this study was to evaluate the effect of CA practices on gas transport characteristics in the silty soils of the Veneto Region (North-Eastern Italy). In 2010, a field experiment comparing CA practices (no-tillage, cover crop and residues retention) to conventional intensive tillage (IT) system was established in four farms located in the Veneto low plain. In fall 2015, 144 undisturbed 100cm3 soil cores where collected at two different layers (3–6.5cm and 20–23.5cm) and analysed for air-filled porosity, air permeability, gas diffusivity and soil structure indices derived.Gas transport measurements highlighted low transmission properties of the silty soils independently from agronomic management. Both air permeability and relative gas diffusivity showed poor aerated conditions being generally <20μm2 and <0.005, respectively.CA treatments affected the transmission properties only in the coarsest soil studied causing a reduction of air permeability in the deeper layer and relative gas diffusivity in both layers. The CA-induced reduction was related to the tillage effect on soil bulk density and suggested that CA not only affected the air-filled porosity but also continuity and tortuosity characteristics.The poor structural stability of Veneto soils, particularly the poor soil organic carbon content, could prevent the exploitation of CA practices firstly on soil structure and in turn on gas exchanges. For these reasons further studies elucidating the mechanisms improving soil structural conditions for silty soils as those examined in this study are required.

Tillage practices and straw-returning methods affect topsoil bacterial community and organic C under a rice-wheat cropping system in central China.

The objective of this study was to investigate how the relationships between bacterial communities and organic C (SOC) in topsoil (0–5 cm) are affected by tillage practices [conventional intensive tillage (CT) or no-tillage (NT)] and straw-returning methods [crop straw returning (S) or removal (NS)] under a rice-wheat rotation in central China. Soil bacterial communities were determined by high-throughput sequencing technology. After two cycles of annual rice-wheat rotation, compared with CT treatments, NT treatments generally had significantly more bacterial genera and monounsaturated fatty acids/saturated fatty acids (MUFA/STFA), but a decreased gram-positive bacteria/gram-negative bacteria ratio (G+/G−). S treatments had significantly more bacterial genera and MUFA/STFA, but had decreased G+/G− compared with NS treatments. Multivariate analysis revealed that Gemmatimonas, Rudaea, Spingomonas, Pseudomonas, Dyella, Burkholderia, Clostridium, Pseudolabrys, Arcicella and Bacillus were correlated with SOC, and cellulolytic bacteria (Burkholderia, Pseudomonas, Clostridium, Rudaea and Bacillus) and Gemmationas explained 55.3% and 12.4% of the variance in SOC, respectively. Structural equation modeling further indicated that tillage and residue managements affected SOC directly and indirectly through these cellulolytic bacteria and Gemmationas. Our results suggest that Burkholderia, Pseudomonas, Clostridium, Rudaea, Bacillus and Gemmationas help to regulate SOC sequestration in topsoil under tillage and residue systems.

Effects of nitrogen fertilizer sources and tillage practices on greenhouse gas emissions in paddy fields of central China

The effects of nitrogen (N) fertilizer sources and tillage practices on greenhouse gas (GHG) emission have been well elucidated separately. However, it is still remained unclear regarding the combined effects of N fertilization and tillage practices on the global warming potential (GWP) and net ecosystem economic budget (NEEB) in paddy fields. In this paper, a 2-year field experiment was performed to investigate the effects of N fertilizer sources (N0, no N; IF, 100% N from chemical fertilizer; SRIF, 50% N from slow-release fertilizer and 50% N from chemical fertilizer; OF, 100% N from organic fertilizer; OFIF, 50% N from organic fertilizer and 50% N from chemical fertilizer) and tillage practices (CT, conventional intensive tillage; NT, no-tillage) on the emissions of methane (CH4) and nitrous oxide (N2O), GWP, greenhouse gas intensity (GHGI), and NEEB in paddy fields of central China. Compared with N0 treatment, IF, SRIF, OF and OFIF treatments greatly enhanced the cumulative seasonal CH4 emissions (by 54.7%, 41.7%, 51.1% and 66.0%, respectively) and N2O emissions (by 164.5%, 93.4%, 130.2% and 251.3%, respectively). NT treatment significantly decreased the GWP and GHGI compared with CT treatment. On the other hand, NT treatment significantly decreased CH4 emissions by 8.5–13.7%, but did not affect N2O emissions relative to CT treatment. Application of N fertilizers significantly increased GWP and GHGI. It was worth noting that the combined treatment of OFIF and NT resulted in the second-highest GWP and GHGI and the largest NEEB among all treatments. Therefore, our results suggest that OFIF combined with NT is an eco-friendly strategy to optimize the economic and environmental benefits of paddy fields in central China. Although the treatment of SRIF plus NT showed the lowest GWP and GHGI and the highest grain yield among all treatments, it led to the lowest NEEB due to its highest fertilizer cost. These results indicate that the government should provide appropriate ecological compensation for this practice, which has low GHG emissions and high rice yield.

Evaluating the use of permanent beds for growing vegetables in North Queensland

Systems for vegetable production in the dry tropics of North Queensland, Australia, have been dominated by intensive tillage and extensive use of nonrenewable polyethylene inputs. A field trial was established to investigate agronomic practices and soil health changes in capsicum and zucchini crops grown with intensive tillage and permanent bed systems. In 2011, conventional intensive tillage with 'plasticulture' was compared to a permanent bed system with subsurface drip irrigation, no soil disturbance and organic mulch produced from a summer sorghum crop. Soil compaction was a major production constraint in the permanent beds in 2011, along with water and nutrient management. Compared to intensive tillage, marketable yield in permanent beds had reductions of 70 and 30%, respectively in capsicum and zucchini. In 2012, the same intensive tillage system was compared to a permanent bed system where minimal soil disturbance had been produced by zone tillage in 10% of the cropped area. It was also compared to a modified system which had permanent beds and zone till but, in addition, had a polyethylene film mulch over the planting beds. The zone tillage and improved fertigation management in 2012 led to marketable yields that were not significantly different among the three tillage systems. In 2013, crops in permanent beds covered with a biodegradable film instead of polyethylene film, had marketable yields that were comparable to the intensive tillage system. Results from the first three years of this study gave indication that minimum tillage has the potential to provide acceptable marketable yields with less dependence on polyethylene use.

Effects of Conservation Tillage on Topsoil Microbial Metabolic Characteristics and Organic Carbon within Aggregates under a Rice (Oryza sativa L.)-Wheat (Triticum aestivum L.) Cropping System in Central China.

Investigating microbial metabolic characteristics and soil organic carbon (SOC) within aggregates and their relationships under conservation tillage may be useful in revealing the mechanism of SOC sequestration in conservation tillage systems. However, limited studies have been conducted to investigate the relationship between SOC and microbial metabolic characteristics within aggregate fractions under conservation tillage. We hypothesized that close relationships can exist between SOC and microbial metabolic characteristics within aggregates under conservation tillage. In this study, a field experiment was conducted from June 2011 to June 2013 following a split-plot design of a randomized complete block with tillage practices [conventional intensive tillage (CT) and no tillage (NT)] as main plots and straw returning methods [preceding crop residue returning (S, 2100−2500 kg C ha−1) and removal (NS, 0 kg C ha-1)] as subplots with three replications. The objective of this study was to reveal the effects of tillage practices and residue-returning methods on topsoil microbial metabolic characteristics and organic carbon (SOC) fractions within aggregates and their relationships under a rice–wheat cropping system in central China. Microbial metabolic characteristics investigated using the Biolog system was examined within two aggregate fractions (>0.25 and <0.25 mm). NT treatments significantly increased SOC concentration of bulk soil, >0.25 aggregate, and <0.25 mm aggregate in the 0−5 cm soil layer by 5.8%, 6.8% and 7.9% relative to CT treatments, respectively. S treatments had higher SOC concentration of bulk soil (12.9%), >0.25 mm aggregate (11.3%), and <0.25 mm aggregate (14.1%) than NS treatments. Compared with CT treatments, NT treatments increased MBC by 11.2%, 11.5%, and 20%, and dissolved organic carbon (DOC) concentration by 15.5%, 29.5%, and 14.1% of bulk soil, >0.25 mm aggregate, and <0.25 mm aggregate in the 0−5 cm soil layer, respectively. Compared with NS treatments, S treatments significantly increased MBC by 29.8%, 30.2%, and 24.1%, and DOC concentration by 23.2%, 25.0%, and 37.5% of bulk soil, >0.25 mm aggregate, and <0.25 mm aggregate in the 0−5 cm soil layer, respectively. Conservation tillage (NT and S) increased microbial metabolic activities and Shannon index in >0.25 and <0.25 mm aggregates in the 0−5 cm soil layer. Redundancy analysis showed that the SOC and its fractions (DOC and MBC) were closely correlated with microbial metabolic activities. Structural equation modelling showed that the increase in microbial metabolic activities directly improved SOC by promoting DOC in >0.25 mm aggregate in the upper (0−5 cm) soil layer under conservation tillage systems, as well as directly and indirectly by promoting DOC and MBC in <0.25 mm aggregate. Our results suggested that conservation tillage increased SOC in aggregates in the topsoil by improving microbial metabolic activities.

Effects of tillage practices and straw returning methods on greenhouse gas emissions and net ecosystem economic budget in rice–wheat cropping systems in central China

Abstract Significant efforts have been devoted to assess the effects of conservation tillage (no-tillage [NT] and straw returning) on greenhouse gas (GHG) emissions, global warming potential (GWP), greenhouse gas intensity (GHGI), and net economic budget in crop growing seasons. However, only a few studies have evaluated the effects conservation tillage on the net ecosystem economic budget (NEEB) in a rice–wheat cropping system. Therefore, a split-plot field experiment was performed to comprehensively evaluate the effects of tillage practices (i.e., conventional intensive tillage [CT] and NT) and straw returning methods (i.e., straw returning or removal of preceding crop) on the soil total organic carbon (TOC), GHG emissions, GWP, GHGI, and NEEB of sandy loam soil in a rice–wheat cropping system in central China. Conservation tillage did not affect rice and wheat grain yields. Compared with CT and straw removal, NT and straw returning significantly increased the TOC of 0–5 cm soil layer by 2.9% and 7.8%, respectively. However, the TOC of 0–20 cm soil layer was not affected by tillage practices and straw returning methods. NT did not also affect the N 2 O emissions during the rice and wheat seasons; NT significantly decreased the annual CH 4 emissions by 7.5% and the annual GWP by 7.8% compared with CT. Consequently, GHGI under NT was reduced by 8.1%. Similar to NT, straw returning did not affect N 2 O emissions during the rice and wheat seasons. Compared with straw removal, straw returning significantly increased annual CH 4 emissions by 35.0%, annual GWP by 32.0%, and annual GHGI by 31.1%. Straw returning did not also affect NEEB; by contrast, NT significantly increased NEEB by 15.6%. NT without straw returning resulted in the lowest GWP, the lowest GHGI, and the highest NEEB among all treatments. This finding suggested that NT without straw returning may be applied as a sustainable technology to increase economic and environmental benefits. Nevertheless, environmentally straw returning methods should be considered in future studies.

Emissions of CH4 and CO2 from paddy fields as affected by tillage practices and crop residues in central China

A field experiment was conducted to investigate effects of tillage practices [no-tillage (NT) and conventional intensive tillage (CT)] and oilseed rape residue returning levels (0, 3000, 6000, 9000 kg dry matter ha−1) on methane (CH4) and carbon dioxide (CO2) emissions and grain yield from paddy fields during the 2011 rice growing season after 2 years oilseed rape-rice rotation in central China. The experiment was established following a split-plot design of a randomized complete block with tillage practices as the main plots and residue returning levels as the sub-plots. NT significantly decreased CO2 and CH4 emissions by 38.8 and 27.3 % compared with CT, respectively. Residue returning treatments released significantly more CO2 and CH4 by 855.5–10410 and 51.5–210.5 kg ha−1 than no residue treatments, respectively. The treatments of 3,000 and 6,000 kg ha−1 residue returning significantly increased rice grain yield by 37.9 and 32.0 % compared with the treatment of no residue returning, respectively. Compared with NT, CT increased yield-scaled emissions of CH4 and CO2 by 16.0 %. The treatments of 6,000 and 9,000 kg ha−1 residue returning significantly increased yield-scaled emissions of CH4 and CO2 by 18.1 and 61.5 %, respectively, compared with the treatment of no residue returning. Moreover, the treatment of NT in combination with 3,000 kg ha−1 residues had the lowest yield-scaled emissions of CH4 and CO2 across tillage and residue treatments. In this way, this study revealed that the combination of NT with 3,000 kg ha−1 residues was a suitable strategy for optimizing carbon emissions and rice grain yield.