Tillage Regimes Research Articles

Phosphorus fractions in an agricultural chronosequence under tillage regimes in the Cerrado area in Goiás, Brazil

The increase in the amount and quantity of soil organic matter (SOM), as well as the use of phosphorus-based fertilizers in the superficial soil layer in areas under tillage regimes (TR), may affect phosphorus (P) dynamics in the soil. Therefore, the aims of the present work were as follows: to evaluate the inorganic and organic fractions of P and its lability levels (labile, moderately labile, and moderately resistant) in a Distroferric Red Latosol under tillage regimes (TR) 3, 15, and 20 years after implementation, and to compare them with those of areas of native Cerrado and pastures. We also focus on analyzing the correlations of the P fractions in these areas with other soil attributes, such as total carbon and nitrogen levels, light organic matter (LOM), chemical and physical granulometric fractions of the SOM, maximum phosphate adsorption capacity (MPAC), and the remaining phosphorus (Prem). In each of these areas, samples were collected from the 0.0-0.05 and 0.05-0.10 m soil layers. An entirely randomized experimental design was used. After TR implementation, the constant use of phosphorus-based fertilizers as well as the incremental addition of SOM resulted in an increase in the levels of labile, moderate labile, and moderately resistant organic and inorganic P, with a tendency for total P accumulation to be mostly in the inorganic, moderately labile form. The native Cerrado soil presented high levels of labile and moderately labile inorganic P. Pasture areas presented the lowest levels of labile organic and inorganic P, as well as moderately labile and moderately resistant organic P. By principal component analysis (PCA), it was possible to observe alterations in all soil attributes and P levels of the fractions analyzed.

Inoculum Potential of Fusarium spp. Relates to Tillage and Straw Management in Norwegian Fields of Spring Oats.

The increased occurrence of Fusarium-mycotoxins in Norwegian cereals over the last decade, is thought to be caused by increased inoculum resulting from more cereal residues at the soil surface as a result of reduced tillage practices. In addition, weather conditions have increasingly promoted inoculum development and infection by Fusarium species. The objective of this work was to elucidate the influence of different tillage regimes (autumn plowing; autumn harrowing; spring plowing; spring harrowing) on the inoculum potential (IP) and dispersal of Fusarium spp. in spring oats. Tillage trials were conducted at two different locations in southeast Norway from 2010 to 2012. Oat residues from the previous year’s crop were collected within a week after sowing for evaluation. IP was calculated as the percentage of residues infested with Fusarium spp. multiplied by the proportion of the soil surface covered with residues. Fusarium avenaceum and F. graminearum were the most common Fusarium species recovered from oat residues. The IP of Fusarium spp. was significantly lower in plowed plots compared to those that were harrowed. Plowing in either the autumn or spring resulted in a low IP. Harrowing in autumn was more effective in reducing IP than the spring harrowing, and IP levels for the spring harrowed treatments were generally higher than all other tillage treatments examined. Surprisingly low levels of F. langsethiae were detected in the residues, although this species is a common pathogen of oat in Norway. The percentage of the residues infested with F. avenaceum, F. graminearum, F. culmorum, and F. langsethiae generally related to the quantity of DNA of the respective Fusarium species determined using quantitative PCR (qPCR). Fusarium dispersal, quantified by qPCR analysis of spore trap samples collected at and after heading, generally corresponded to the IP. Fusarium dispersal was also observed to increase after rainy periods. Our findings are in line with the general understanding that plowing is a means to reduce the IP of Fusarium spp. in cereal fields. The main inoculum source for F. langsethiae remains unclear. Our results will be useful in the development of forecasting tools to calculate the risk of Fusarium in cereals.

No favorable effect of reduced tillage on microbial community diversity in a silty loam soil (Belgium)

Among the soil management practices used to promote sustainable agriculture, reduced tillage and retention of residues from the previous crop are reported to enhance significantly both soil fertility and crop productivity. Here, high-throughput sequencing (454 technology) was used to see how the tillage regime (conventional vs. reduced tillage) and the fate of crop residues (retention or removal) affect microbial communities at two sampling depths (top soil: 0–5cm and deeper soil: 15–20cm) in a fertile silty loam soil in Belgium. All combinations of these three factors were studied. After 6 years of conversion from conventional to reduced tillage, depth emerged as the main factor responsible for variation in microbial diversity, tillage regime ranked second, and finally, crop residue fate had no influence on microbial diversity. For both bacteria and fungi, the diversity appeared higher in the top soil than in the deeper soil, and surprisingly, higher under conventional than under reduced tillage. These differences are explained by changes in community composition due to taxon loss rather than taxon replacement. The specific local set of environmental conditions (a loess-derived soil and an oceanic temperate climate) may explain these results. These observations raise the question: does impoverishment in indicator taxa influence soil processes, and thus crop production? To answer this question, we discuss how the presence of certain indicator taxa liable to play an ecological role might relate to crop productivity.

Occasional reduced tillage in organic farming can promote earthworm performance and resource efficiency

Reduced tillage has several advantages over conventional tillage (CT), including the promotion of earthworm communities and the reduction of input of energy and labour. However, its application in organic farming is mainly hindered through increasing weed pressure. One way to counteract this drawback might be to introduce occasional reduced tillage (ORT), which means applying methods of reduced tillage only in combination with selected crops. Against this background we hypothesized that (i) ORT rapidly promotes biomass, abundance and species richness of earthworm communities and that (ii) ORT generates a financial surplus for farmers. Therefore, a field experiment was established for triticale (x Triticosecale) cultivation on loamy soils in Northern Germany. The influence of tillage regimes on earthworms was investigated in a non-randomized design with n=3 fields for the ORT and CT treatment. Earthworm biomass, abundance and species richness were investigated in October 2012 and in April and October 2013. Yields were determined for the three fields under each tillage system, each field with four non-randomized replicates, before harvest in 2013. The ORT treatment consisted of two to three tillage operations prior to seeding with a maximal cultivation depth of 15cm and without ploughing, whereas the CT treatment consisted of a ploughing depth of 25–30cm and one to four other steps for seedbed preparation prior to seeding. In total, seven earthworm species were identified. Our data revealed that earthworm biomass was significantly reduced under CT, both four weeks and about seven months after tillage. This effect holds true for the number of earthworm individuals in autumn (four weeks after ploughing), but not for the number of earthworm individuals in spring (seven months after ploughing). Results of contribution margin analysis showed no consistent trend referring to tillage measures. Two fields, which performed well under CT, showed a financial surplus (+24% and +13%) when managed with ORT. At the same time one field, performing poorly under CT, generated financial deficits (-10%) under ORT. Overall ORT had immediate positive effects on earthworm populations. Furthermore, this management scheme might have positive effects on the economic outcomes of organic crop rotations if overall growing conditions are sufficient. Along with methods usually applied to investigate earthworm performance, we checked whether the number of surface casts could help estimate earthworm performance. It became apparent that the number of surface casts cannot be used as a general predictor of earthworm performance. The number of individuals of Lumbricus terrestris, the number of anecic individuals and the total earthworm biomass can be estimated the most reliable by counting surface casts.

Emergence dynamics of barnyardgrass and jimsonweed from two depths when switching from conventional to reduced and no-till conditions

A cylinder experiment was conducted in northern Greece during 2005 and 2006 to assess emergence dynamics of barnyardgrass (Echinochloa crus-galli (L.) Beauv.) and jimsonweed (Datura stramonium L.) in the case of a switch from conventional to conservation tillage systems (CT). Emergence was surveyed from two burial depths (5 and 10 cm) and with simulation of reduced tillage (i.e. by soil disturbance) and no-till conditions. Barnyardgrass emergence was significantly affected by burial depth, having greater emergence from 5 cm depth (96%) although even 78% of seedlings emerged from 10 cm depth after the two years of study. Emergence of barnyardgrass was stable across years from the different depths and tillage regimes. Jimsonweed seeds showed lower germination than barnyardgrass during the study period, whereas its emergence was significantly affected by soil disturbance having 41% compared to 28% without disturbance. A burial depth x soil disturbance interaction was also determined, which showed higher emergence from 10 cm depth with soil disturbance. Jimsonweed was found to have significantly higher emergence from 10 cm depth with soil disturbance in Year 2. Seasonal emergence timing of barnyardgrass did not vary between the different burial depth and soil disturbance regimes, as it started in April and lasted until end of May in both years. Jimsonweed showed a bimodal pattern, with first emergence starting end of April until mid-May and the second ranging from mid-June to mid-August from 10 cm burial depth and from mid-July to mid-August from 5 cm depth, irrespective of soil disturbance in both cases.

Evaluating the Impact of Different Tillage Regimes and Nitrogen Levels on Yield and Yield Components of Maize (<i>Zea mays</i> L.)

A field study to evaluate the impact of different tillage regimes and nitrogen levels on yield and yield components of maize (Zea mays L.), was conducted during autumn 2014 at Students Farm, Department of Agronomy, University of Agriculture, Faisalabad. The experiment was laid out in RCBD (Randomized Complete Block Design), with split plot arrangement having three replications. The experiment was comprised of three tillage regimes (Minimum, Conventional and Deep) and three nitrogen levels viz: 100, 200 and 300 kg•ha-1. Urea was used as a source of nitrogen, sulphate of potash as a source of potassium and triple super phosphate as a source of phosphorous. The amount of phosphorous and potash was constant in all the treatments i.e. 125 kg•ha-1 and 100 kg•ha-1 respectively. Results of present study are summarized as yield parameters are significantly affected by different nitrogen levels and tillage regimes. Maximum number of plants at harvest (7.93), number of grain rows per cob (17.70), number of grains per row (34.31), number of grains per cob (678.58), and cob weight (187.50 g) were observed in deep tillage at 200 kg•ha-1 nitrogen application. 1000-grain weight (275.52 g), biological yield (15.66 t•ha-1), grain yield (6.16 t•ha-1) and dried stalk yield (9.91 t•ha-1) were observed maximum in deep tillage at 200 kg•ha-1 nitrogen application. Harvest index significantly affected by tillage regimes and maximum harvest index (39.58%) were recorded in deep tillage which was statistically at par with conventional tillage (38.83%). It was concluded that higher grain yield of maize can be obtained by deep tillage with the application of 200 kg•ha-1 nitrogen application under the prevailing conditions of Faisalabad.

Postdispersal Weed Seed Predation and Invertebrate Activity Density in Three Tillage Regimes

Field experiments were conducted near Boone, IA, to quantify postdispersal seed predation of common lambsquarters and common waterhemp in corn (2003) and soybean (2004) managed with conventional, reduced, and zero-tillage systems. Seed predation in each tillage regime was quantified using selective exclusion treatments during July through September 2003 and June through October 2004. In addition, the activity density of ground-dwelling invertebrates was estimated with pitfall traps. Choice and no-choice feeding trials were conducted in the laboratory using the most abundant weed seed predators found in the field to determine seed preferences of the potential predator organisms. The greatest seed loss occurred during July and August. In 2003, seed predation was lower in zero tillage than in conventional and reduced tillages, but no differences in seed predation between tillage regimes were observed in 2004. Maximum seed predation for common lambsquarters was 53% in 2003 and 64% in 2004. Common waterhemp seed predation reached 80% in 2003 and 85% in 2004. The majority of seed predation was by invertebrate organisms. The most common invertebrate species captured with pitfall traps were field crickets (Gryllus pennsylvanicusDe Geer [Gryllidae, Orthoptera]) and ground beetles (Harpalus pensylvanicusBurmeister [Coleoptera, Carabidae]). In 2003, field crickets were relatively more abundant in conventional and reduced tillage than in zero-tillage plots. In 2004, field crickets were more abundant in the reduced tillage than in the other two tillage regimes. No differences were detected for ground beetles among tillage regimes (P = 0.57). Choice and no-choice feeding experiments confirmed the preferences of field crickets and ground beetles for common lambsquarters and common waterhemp seeds over the larger seeds of giant foxtail and velvetleaf. Under field conditions, the activity density of field crickets was a significant predictor of common lambsquarters (r2= 0.47) and common waterhemp (r2= 0.53) seed predation. Positive relationships were also detected between the activity density of ground beetles and common lambsquarters (r2= 0.30) and common waterhemp (r2= 0.30) seed predation. This research demonstrated that weed seed predation is an important component affecting weed seedbanks and that crop management practices that favor the activity of predators such as field crickets or ground beetles could influence weed populations. Also, the results suggested that tillage is more important in determining the number of weed seeds available on the soil surface to predators than directly affecting predator activity density.

Nonconventional Weed Management Strategies for Modern Agriculture

Weeds are a significant problem in crop production and their management in modern agriculture is crucial to avoid yield losses and ensure food security. Intensive agricultural practices, changing climate, and natural disasters affect weed dynamics and that requires a change in weed management protocols. The existing manual control options are no longer viable because of labor shortages; chemical control options are limited by ecodegradation, health hazards, and development of herbicide resistance in weeds. We are therefore reviewing some potential nonconventional weed management strategies for modern agriculture that are viable, feasible, and efficient. Improvement in tillage regimes has long been identified as an impressive weed-control measure. Harvest weed seed control and seed predation have been shown as potential tools for reducing weed emergence and seed bank reserves. Development in the field of allelopathy for weed management has led to new techniques for weed control. The remarkable role of biotechnological advancements in developing herbicide-resistant crops, bioherbicides, and harnessing the allelopathic potential of crops is also worth mentioning in a modern weed management program. Thermal weed management has also been observed as a useful technique, especially under conservation agriculture systems. Last, precision weed management has been elaborated with sufficient details. The role of remote sensing, modeling, and robotics as an integral part of precision weed management has been highlighted in a realistic manner. All these strategies are viable for today's agriculture; however, site-specific selection and the use of right combinations will be the key to success. No single strategy is perfect, and therefore an integrated approach may provide better results. Future research is needed to explore the potential of these strategies and to optimize them on technological and cultural bases. The adoption of such methods may improve the efficiency of cropping systems under sustainable and conservation practices.

Phospholipid 13C stable isotopic probing during decomposition of wheat residues

Disentangling the kinetics of the soil microbial community succession, which is simultaneously driven by newly added plant materials and extant soil organic matter (SOM), can enrich our knowledge on microbial carbon (C) utilization patterns under residue amendment. This understanding might be useful to predict the rapid responses of specific microbial functional groups and develop strategies for balancing the terrestrial C budget. Therefore, our objective was to characterize and estimate the parameters of the microbial community dynamics profiled by phospholipid fatty acids (PLFA) from 13C-labeled wheat residues and SOM. We conducted a 21-day microcosm study using two different arable systems (conventional tillage, CT; no-till, NT) amended with three types of 13C-labeled wheat residues (grains, leaves and roots). The abundances and isotopic fractions of 13CO2 flux and 13C-labeled PLFA were measured via gas trace isotope ratio mass spectrometry (IRMS) and gas chromatography-combustion-isotope ratio mass spectrometry (GC-c-IRMS), respectively. A double exponential model was used to describe the synthesis-degradation kinetics of PLFA from different microbial origins. We found that the PLFA formation generally reaches its maximal abundance within 7 days (except for PLFA from actinomycetes). The SOM- and wheat residue-derived C fluxes, as well as their PLFA profiles, were inconsistently impacted by the residue quality or the tillage regime over the incubation period. Specifically, the abundances of residue-derived CO2 and PLFAs significantly decreased in the following order: grains>leaves>roots. However, those abundances derived from SOM were the lowest with the leaf residue treatments. Residue-derived PLFA patterns were highly influenced by fungi and G− bacteria, while G+ bacterial and actinomycete PLFAs were preferentially linked to extant SOM mineralization. Compared to the residue-derived counterparts, the SOM-derived microbes were characterized by higher G+/G− bacteria and cy17:0/C16:1ω7c ratios, as well as lower fungi/bacteria PLFA ratios. Such distinction between residue and SOM was also evidenced by the contrasting tillage effects on C mineralization and the ratios of cy17:0/C16:1ω7c and fungal/G− bacterial PLFA. Our study provides evidence with important implications for adapting the microbial-mediated processes of soil C management through residue quality control.

Lumbricus terrestris abundance is not enhanced after three years of compost amendments on a reduced tillage wheat cultivation conversion

This study compared the abundance of Lumbricus terrestris middens under wheat cultivations treated with 3.5tCha−1 compost (n=15) or farmyard manure (n=15) amendments. The abundance of L. terrestris middens was significantly (p<0.01) greater on the farmyard manure amended plots than the compost or control plots, with a ca. 38% higher midden abundance. These data suggest that compost is a not a good alternative to farmyard manure to improve L. terrestris populations when converting from conventional (plough) to reduced tillage (stubble cultivated) regimes.

Effect of conservation practices on soil carbon and nitrogen accretion and crop yield in a corn production system in the southeastern coastal plain, United States

Although conservation tillage is widely believed to be an agricultural management practice effective for increasing soil carbon (C) accretion and associated soil quality, there is limited research to determine whether conservation tillage increases net C accretion versus simply altering the distribution of C content by soil depth. We implemented conservation farming practices (winter cover cropping plus strip tillage) for a nonirrigated corn (<i>Zea mays</i> L.) production system in the southeastern coastal plain of Georgia, United States, that had been previously managed under a conventional plow and harrow tillage regime. Total soil C and nitrogen (N) were measured on samples collected from 0 to 65 cm (0 to 25.6 in) at 57 sites before and after five years under conservation farming practices. Crop yield, winter and summer aboveground crop biomass production, and biomass C and N content were also measured annually at each site. Soil C increased an average of 20 Mg ha⁻¹ (8.9 tn ac⁻¹; 6 to 62 Mg C ha⁻¹ [2.6 to 27.6 tn C ac⁻¹], depending upon slope position) and was associated with a N increase of 2 Mg ha⁻¹ (0.89 tn ac⁻¹). Although 72% to 80% of the C accretion was in the top 35 cm (13.8 in), 3 to 6 Mg C ha⁻¹ (1.3 to 2.6 tn C ac⁻¹) was accreted from 35 to 65 cm (13.8 to 25.6 in). The soil C accreted during the study amounted to 36% of the net biomass C produced. Corn yield increased 2,200 kg ha⁻¹ (1,964 lb ac⁻¹) depending upon slope position (1,200 to 2,500 kg ha⁻¹ [1,071 to 2,232 lb ac⁻¹]) during the same time. Analysis indicated that soil C content from 15 to 35 cm (5.9 to 13.8 in) was the soil parameter primarily associated with corn yield. Season rainfall from planting to corn silking stage for both corn production years was the lowest in the past 45 years (20 to 25 cm [7.8 to 9.8 in] below the net crop demand) suggesting that soil C-mediated increase in plant-available soil water was a mechanism contributing to improved corn yield. Calculated estimates (from soil clay, sand, and C content) of increased soil water holding capacity suggest that C accretion in the top 35 cm (13.8 in) of soil potentially increased water storage enough to supply up to four days9 worth of additional crop water demand. These results indicated that conservation farming practices can increase soil C and N accretion in degraded sandy soils of the humid southeastern United States coastal plain, and that increased soil C may potentially mitigate the deleterious effects of short-term rainfall deficits in nonirrigated production systems.

Tillage Management and Seasonal Effects on Denitrifier Community Abundance, Gene Expression and Structure over Winter.

Tillage effects on denitrifier communities and nitrous oxide (N2O) emissions were mainly studied during the growing season. There is limited information for the non-growing season, especially in northern countries where winter has prolonged periods with sub-zero temperatures. The abundance and structure of the denitrifier community, denitrification gene expression and N2O emissions in fields under long-term tillage regimes [no-tillage (NT) vs conventional tillage (CT)] were assessed during two consecutive winters. NT exerted a positive effect on nirK and nosZ denitrifier abundance in both winters compared to CT. Moreover, the two contrasting managements had an opposite influence on nirK and nirS RNA/DNA ratios. Tillage management resulted in different denitrifier community structures during both winters. Seasonal changes were observed in the abundance and the structure of denitrifiers. Interestingly, the RNA/DNA ratios were greater in the coldest months for nirK, nirS and nosZ. N2O emissions were not influenced by management but changed over time with two orders of magnitude increase in the coldest month of both winters. In winter of 2009-2010, emissions were mainly as N2O, whereas in 2010-2011, when soil temperatures were milder due to persistent snow cover, most emissions were as dinitrogen. Results indicated that tillage management during the growing season induced differences in denitrifier community structure that persisted during winter. However, management did not affect the active cold-adapted community structure.

Agricultural management reduces emergence of pollen beetle parasitoids

Natural enemies such as predatory arthropods and parasitoids have the potential to suppress pest species and provide the ecosystem service biological control. When predicting the potential of biological control in agriculture it is important to give evidence on how agricultural management influence the abundance and functions of the natural enemies. In this study we examined whether managements practices as insecticide application and different tillage regimes, can influence biological control of a herbivorous pest on oilseed rape (Brassica napus L.). The endoparasitoids Phradis interstitialis Thomson and Tersilochus heterocerus Thomson were studied as they are important for the biological control of the pollen beetle (Meligethes aeneus F.) which is a common pest on oilseed rape in Europe. The number of emerging female parasitoids was quantified by capturing the parasitoids in emergence tents from fields where the oilseed rape plants were grown the previous year. The number of emerging P. interstitialis and T. heterocerus were significantly reduced in insecticide treated fields, but the tillage regimes had no effect on the number of emerging females of either parasitoid species. We conclude that when predicting the biological control potential by pollen beetle parasitoids in agricultural landscapes it is important to consider insecticide treatment of former oilseed rape fields as that can influence population densities at the landscape scale the following year.

Effects of tillage pan on soil water distribution in alfalfa-corn crop rotation systems using a dye tracer and geostatistical methods

The present study was designed to assess the potential effects of tillage pan on the distribution and the movement of soil water. Two different tillage regimes of an alfalfa-corn crop rotation system were carefully selected. Plot 1 contained alfalfa without tillage for the past 10 years. Plot 2 contained alfalfa with no tillage for the first 5 years and corn with conventional tillage for the succeeding 5 years. A dye tracer was introduced to these plots and the different types of water flow were visualized using classified dye-stained patterns. In addition, the kriging maps of gravimetric soil water content were used to indicate potential distribution characteristics. Semivariance analysis was performed to determine spatial variability on a centimeter scale. The role of macropore flow was weaker in the alfalfa plot than in the corn plot because of the difference in flow path and distribution. A belt of high soil moisture content appeared in the vertical soil profile of the alfalfa plot, indicating that the macropore flow showed a deeper stained depth. Several scattered locations in the corn plot contained high amounts of water, suggesting that macropore flow also occurred. The soil water content in the corn plot demonstrated infiltration patterns with higher degrees of fragmentation than that in the alfalfa plot. Moreover, a lateral flow with a wider stained width was triggered by the compacted tillage pan in the corn plot. Thus, the role of lateral flow was more dominant in the corn plot than in the alfalfa plot. The spatial correlation distance of the soil water content of infiltration patterns was 23.08cm in the alfalfa plot compared with 10.52cm in the corn plot. This trend indicated a high spatial variation of moisture in water infiltration patterns of the alfalfa field. In addition, strong spatial autocorrelation was observed in soil water infiltration patterns in both plots (nugget percentages of <25%). Our results highlighted a significant change of soil water behaviors in crop rotation from alfalfa to corn. In particular, downward water flow was restricted by a compacted tillage pan; thus, water was stored in the loose soil structure of the corn plot.

Soil water use, grain yield and water use efficiency of winter wheat in a long-term study of tillage practices and supplemental irrigation on the North China Plain

We report the results of a six-year study (2007–2013) of tillage regimes for use in producing winter wheat (Jimai 22) on the North China Plain, with supplemental irrigation. The tillage regimes include: plowing for six years (P6); rotary for six years (R6); rotary after subsoiling with an interval of two years (S1R2); subsoiling with an interval of three years (S1R3); subsoiling with an interval of four years (S1R4); and subsoiling with an interval of five years (S1R5). In comparison with the P6 and R6 treatments, the S1R2 and S1R3 treatments improved water storage capacity, maintained higher soil moisture content in the 100–160cm soil layers before sowing and significantly decreased soil moisture content in the 20–180cm soil layers at maturity, in all years. Hence, S1R2 and S1R3 led to greater utilization of water stored in the 60–180cm soil layers. Evapotranspiration (ETc), soil water consumption, and the ratio of soil water consumption to ETc for S1R2 and S1R3 were significantly higher than those for other treatments. Average grain yields for the six growth seasons were ranked as S1R2, S1R3>S1R4>S1R5>P6>R6, while water use efficiency was ranked in the order of S1R2, S1R3, S1R4>S1R5, P6>R6. Grain yields of S1R2 and S1R3 were 9.028 and 8.817kgha−2, respectively, which are higher than the yield of R6 (conventional tillage) by 27.7% and 24.7%, respectively. Hence, rotary tillage after subsoiling with an interval of two or three years (S1R2 and S1R3) can be considered as a desirable tillage practice for increasing yields, while using water efficiently in this region.

Integrative effects of soil tillage and straw management on crop yields and greenhouse gas emissions in a rice–wheat cropping system

Significant efforts have been made to assess the impact of tillage regimes on crop yields and/or greenhouse gas (GHG) emissions across single crop growing season. However, few studies have quantified the impact across a whole rotation cycle in multiple cropping systems. Utilizing on a long-term tillage experiment with the rice–wheat rotation system in East China, we examined the GHG emissions under different tillage practices with or without crop straw incorporation. Results showed that compared to the no-straw control, straw incorporation increased wheat yield by 28.3% (P<0.05), irrespective of tillage practices, but had no significant effect on rice yield. Although straw incorporation did not significantly affect CH4 emissions during the wheat season and N2O emissions during the whole rice–wheat cycle, it significantly stimulated CH4 emissions by 98.8% (P<0.01) during the rice season. Also, there were no significant differences in CH4 and N2O emissions between tillage practices during the wheat season. Compared to plowing, rotary tillage increased CH4 emissions significantly by an average of 38.8% (P<0.01) but had no significant impacts on N2O emissions during the rice season. Across the rotation cycle, annual yield-scaled global warming potential of CH4 and N2O emissions under no-tillage plus rotary tillage was 26.8% (P<0.01) greater than that of rotary tillage plus plowing with or without straw incorporation. Significant interactions between soil tillage and straw management practices were found on annual GHG emissions, but not on crop yields. Together, these results indicate that plowing in the rice season plus rotary tillage in the wheat season may reduce GHG emissions while increasing crop yield in rice–wheat cropping areas.

Effects of slash-and-burn practices on soil seed banks in secondary forest successions in Madagascar

Forest seed bank assessments are scarce in Madagascar and thus little is known about the relationships between the seed banks and vegetation dynamics on which secondary succession processes rely. The objective of this paper is to analyse the effects of slash-and-burn agriculture on soil seed banks and their dynamics along secondary forest successions. The aim of this work is to determine the effects of agricultural practices (cropping duration, tillage regime and fallow age) on seed bank density (SBD) and diversity (SBSR) during secondary succession periods (<25 years). Cropping duration was divided into three classes: (i) short (1–2 years), (ii) medium (3–5 years) and (iii) long (6–11 years). Tillage regime during crop successions was divided into three categories: (1) no tillage (only direct sowing is observed), (2) light tillage (after direct sowing, local shallow tillage is observed) and (3) heavy tillage (after direct sowing followed by light tillage practice, complete tillage practice is observed). Fifteen fallows subdivided into three regrowth age classes (2–6, 10–12 and 14–22 years) were surveyed. Fallow age is the main driver of SBD and SBSR: they increase with fallow age, regardless of cropping duration and tillage regime. SBD and SBSR recovery always occurs but is slower under long cropping duration (3–11 years) and heavy tillage regime because cropping duration helps to maintain a high level of wind-dispersed seeds during secondary succession and tillage regime contributes to reducing the proportion of viable seeds.

Measurement of soil aggregate stability using low intensity ultrasonic vibration

The objective of this study was to analyse the influence of tillage on soil aggregate stability using the ultrasonic dispersion method with different levels of energy. Experiments are performed with self-developed equipment at low vibration amplitudes of 0.5 μm, 2 μm and 5 μm. Ultrasonic power is 0.7 W, 8.9 W and 22.3 W for the three amplitudes. Samples of aggregates 2 000 - 250 μm of a degraded loamy silt Chernozem, a loamy clay Cambisol and a loamy sand Cambisol from eastern Austria were collected under different tillage regimes: conventional tillage (CT) with mechanical weed control and no tillage (NT) with inter cropping in winter. Measuring Soil Aggregate Stability (SAS) according to DIN norm showed that the stability decreased in the sequence loamy clay Cambisol &amp;gt; loamy sand Cambisol &amp;gt; loamy silt Chernozem. Influences of tillage could be observed with SAS for the last two samples mentioned. Ultrasonic dispersion tests at vibration amplitude 0.5 μm and 2 μm show higher stability of the Cambisol soils. Significant influences of soil tillage on aggregate stability for the loamy clay Cambisol and the degraded Chernozem were observed after short ultrasonic dispersion times and absorbed energies of 1 - 1.7 J ml&lt;sup&gt;-1&lt;/sup&gt;. The measured aggregate stability decreased in the following order: Cambisol NT &amp;gt; Cambisol CT &amp;gt; Chernozem NT &amp;gt; Chernozem CT. Differences in loamy sand Cambisol could not be detected with the ultrasonic method due to a low aggregation level of the macro aggregates. This study highlights the importance of quantifying the energy output of the ultrasonic equipment when analysing changes in soil aggregate stability, for the evaluation of tillage treatments. A more comprehensive analysis of aggregate stability can be obtained when using both, the wet-sieving SAS method and ultrasonic dispersion at low energy levels.

Anhydrous Ammonia Injection Depth Does Not Affect Nitrous Oxide Emissions in a Silt Loam over Two Growing Seasons.

Anhydrous ammonia (AA) is a major fertilizer source in North America that can promote greater emissions of nitrous oxide (NO) than other nitrogen (N) fertilizers. Previous studies found that injection of AA at a shallow depth (0.1 m) decreased NO in a rainfed clay loam but increased NO in an irrigated loamy sand compared with the standard injection depth of 0.2 m. The objective of this study was to evaluate the effects of AA injection depth in a silt loam soil used for corn ( L.) production and managed under two contrasting tillage regimes over two consecutive growing seasons (2010 and 2011) in Minnesota. In contrast with previous studies, AA placement depth did not affect NO emissions in either tillage system or in either growing season. Tillage by itself affected NO emissions only in the drier of two seasons, during which NO emissions under no tillage (NT) exceeded those under conventional tillage (CT) by 55%. Soil moisture content under NT was also greater than under CT only in the drier of the two seasons. Effects of AA placement depth and long-term tillage regime on NO emissions exhibit intersite as well as interannual variation, which should be considered when developing NO mitigation strategies. Further study is needed to identify specific soil, climate, or other factors that mediate the contrasting responses to management practices across sites.

Soil organic matter degradation in an agricultural chronosequence under different tillage regimes evaluated by organic matter pools, enzymatic activities and CPMAS ¹³C NMR

Conservation agriculture (CA) is an important strategy to improve the quality of surface soils under Mediterranean conditions and its primary intent is to minimize the mineralization of soil organic matter (SOM). The focus of this manuscript is to evaluate how soil quality indices (e.g., enzymatic activity, total organic carbon (TOC), and labile carbon pools) are inter-connected and how tillage could affect cycles of storage and degradation of SOM. To achieve this objective, five different enzymatic activities, TOC, water soluble carbon and microbial biomass carbon were measured on soil samples collected at an experimental farm situated in the southwest region of Spain. Furthermore, the relative abundance of organic compound classes was measured, using CPMAS 13C NMR on bulk soil samples, humic acids (HA), and particulate organic matter (POM) fractions separated by density. Our results show that conservation tillage enhances soil quality at the surface for mid- and long-term experiments. The NMR analyses demonstrate that conservation tillage led to a preservation of less degraded SOM and revealed a high amount of proteinaceous material preserved from degradation. It is clear that TOC, β-glucosidase and alkaline phosphatase activities are reliable soil quality indices and we further propose that the CPMAS 13C NMR analyses of the particulate organic matter (POM) fraction of soil is an excellent evaluator for changes that occur in soil status.