No-till Practices Research Articles

Making use of the ecosystem services concept in regional planning—trade-offs from reducing water erosion

In this article we demonstrate how to integrate the ecosystem services concept into regional planning using the example of a case study in Saxony, Germany. We analysed how the reduction of water erosion as a regulating service impacts six other ecosystem services. Ecological integrity, provisioning services (provision of food and fibre, provision of biomass), regulating services (soil erosion protection, drought-risk regulation, flood regulation), and the cultural service landscape aesthetics are taken into account. Using a decision support software, we found that the greening of preferential discharge paths can reduce water erosion by 2–7 %. The introduction of hedgerows and the change in the soil management system from tillage to no-till practices revealed a reduction in the total soil loss by 33 and 89 %, respectively. A combination of the three erosion control measures—greening, hedgerows, and no-till management—reduced the soil loss most efficiently by 92 %. We found synergies between the measures for reducing erosion and the provision of ecological integrity, of regulating and cultural ecosystem services. In contrast, the impact on provisioning services was slightly negative. For the land use planning in the case study region we recommend therefore a combination of greening, hedges, and management change. We found that the applied integrated ecosystem services assessment approach, in combination with stakeholder involvement in the scenario development, helped communicating cross-sectoral effects of different management strategies in a comprehensive way and therefore supports regional planning.

Tillage effects on certain physical and hydraulic properties of a loamy soil under a crop rotation in a semi-arid region with a cool climate

The purpose of this study was to research the influence of four different tillage practices [T1: Conventional tillage (moldboard plow+disk harrow+combined harrows+precision seeder); T2: Reduced tillage-I (cultivator+combined harrows+precision seeder); T3: Reduced tillage-II (rotary power harrow+precision seeder) and T4: No-till (no-till seeder)] on bulk density, total porosity, penetration resistance, field capacity, field water content and the infiltration rate of a loamy soil in a semi-arid region with a cool climate and an annual mean temperature of 5.6°C. In particular, the effectiveness of the no-till practice was investigated. Since 1999, the experimental field has been tilled by the above-mentioned tillage practices and also applied a crop rotation (vetch–winter wheat–fallow) in dry conditions. We made assessments of selected soil properties according to the data during the sowing–germination period of winter wheat only in 2012 autumn. Therefore, the number of germinated seedlings of winter wheat was also evaluated. The data of this study carried out in three replications were statistically analyzed using the ANOVA and the regression technique.The results indicated that the tillage treatments affected soil properties and wheat germination. The highest values in all examined parameters except for total porosity were obtained under the no-till practice for top soil layer of 30cm. As was expected, the no-till treatment had the highest bulk density and provided the lowest total porosity. Generally, the plots tilled by conventional practice had the lowest values. Similar results were obtained for the top soil layer of 0–10cm, which is seedbed. The penetration resistance measured to a depth of 30cm in 5cm increments increased as polynomial with increasing the soil depth in all treatments. The infiltration rate decreases as a function of elapsed time could be described by the Kostiakov equation. Also, significant linear relationships were obtained for penetration resistance–bulk density, field capacity–bulk density and field capacity–penetration resistance.Although no-till treatment improved the hydraulic properties of soil, it had no positive effect on the soil physical properties. However, the linear relations with high correlation coefficients between penetration resistance and bulk density with field capacity at the no-till showed that soil physical and hydraulic properties revealed that they are connected to each other. According to the results of our study it could be concluded that the no-till practice increased winter wheat germination due to higher water content.

How much soil organic carbon sequestration is due to conservation agriculture reducing soil erosion?

Soil organic carbon (SOC) redistribution by soil erosion is fundamental to the C cycle and is a key component of global soil C accounting. Widespread conversion of cropland to forest and grassland and the adoption of conservation agriculture (minimum-till and no-till practices) worldwide and particularly in China since 2000, may have reduced wind erosion and increased SOC storage and ‘avoided’ CO2 emission. However, few SOC sequestration studies have separated changes in SOC stock caused by changes in land-use and management activity from net SOC redistribution due to reduced SOC erosion and SOC dust accumulation, particularly from individual or short-term (months) wind erosion events. We used measurements of SOC and the short-lived natural radionuclide beryllium-7 (7Be, half-life 53.3 days) to estimate net SOC redistribution for changes in several land-use and management practices in Fengning County in North China. Compared with conventional tillage (CT), conservation grassland (CG) and minimum tillage (CL) showed enhanced SOC stocks (0–245 mm depth) of ~0.8 ± 0.03 and 2.0 ± 0.06 t C ha–1 year–1 as a consequence of their land-use conversion for 5 and 3 years, respectively. However, SOC erosion on CG (0.46 ± 0.04 t C ha–1 year–1) and CL (0.52 ± 0.04 t C ha–1 year–1) plots was 54% and 47%, respectively, less than on CT (0.99 ± 0.11 t C ha–1 year–1). Net C sequestration (0–245 mm), considering SOC redistribution for CG (0.27 ± 0.12 t C ha–1 year–1; 5 years) and CL (1.53 ± 0.13 t C ha–1 year–1; 3 years), revealed an overestimate of 196% and 31% without considering SOC redistribution (CG, 0.8 ± 0.03 t C ha–1 year–1; CL, 2.0 ± 0.06 t C ha–1 year–1), respectively, relative to CT. Reduced SOC erosion and/or SOC dust accumulation by vegetation–crop cover must be included when considering SOC sequestration induced by changes in land use and management.

Soil Microbial Biomass and Diversity Amended with Bagasse Mulch in Tillage and No-tillage Practices in the Sugarcane Plantation

Biomass residues in plantation farms and process industries still have valuable materials and can be recycled as other materials. Gunung Madu Plantation (GMP) in Lampung Province, Indonesia where this study was observed had used bagasse as mulch 80 tons (wet weight) per hectare. This study observed the effect of tillage and bagasse much on soil microbes in sugarcane plantation. Each treatment was used in conjunction with or without bagasse mulch in a split-plot experimental design. Previous study showed bagasse mulch had increased litter fungal biomass and communities in the soil. However soil microbial community structure has not been comprehensively investigated. Quinone profile method was used to analyze the community structure amended with bagasse mulch in the sugarcane plantation. Quinone profile method reflectively estimated the microbial biomass and the diversity. The no-tillage with bagasse mulch had the highest microbial biomass (1.026μmol kg-1 dry soil) compare to the no-tillage without bagasse mulch, the conventional tillage with bagasse mulch and the conventional tillage without bagasse mulch. The Diversity index (DQ) and Shannon-Wiener diversity index (H) was also the highest in the no-tillage amended with bagasse mulch. Therefore mulch treatment in combination with no-tillage is an effective residue management of biomass residue to improve soil quality.

Tolerance of Winter Wheat (<i>Triticum aestivum</i> L.) and Under Seeded Red Clover (<i>Trifolium pretense</i> L.) to Fall Applied Post-Emergent Broadleaf Herbicides

The fall application of post-emergent (POST) herbicides on winter wheat provided effective control of emerged winter annual, biennial, and perennial broadleaf weeds. In recent years, wheat producers have seen a shift to these weeds, due in part, to the adoption of reduced-and no-tillage practices and the use of non-residual herbicides such as glyphosate in the preceding soybean and corn crops. The tolerance of winter wheat to ten herbicides, applied POST in the fall, was evaluated between 2008 and 2011 at Exeter and Ridgetown, Ontario. Winter wheat yield was not reduced by applications of MCPA ester, dicamba/ MCPA/ mecoprop, clopyralid, bromoxynil/ MCPA, thifensulfuron /tribenuron +MCPA ester, fluroxypyr +MCPA ester, and pyrasulfotole/ bromoxynil. In contrast, 2,4-D ester and dichlorprop/2,4-D, caused visible injury in June and July of the following year and consistently decreased winter wheat yield by at least 10%. Applications of 100 g a.i. ha-1 saflufenacil also decreased winter wheat yield in two of the four harvest years examined. None of the herbicide options examined were safe on red clover when it was under seeded the spring following winter wheat planting. All herbicides significantly decreased red clover dry biomass one month after wheat harvest.

Long-term tillage and drainage influences on greenhouse gas fluxes from a poorly drained soil of central Ohio

Intensive tillage practices and poorly drained soils of the Midwestern United States are one of the prime reasons for increased greenhouse gas (GHG) fluxes from agriculture. The naturally poorly drained soils prevalent in this region require subsurface drainage for improving aeration and reducing GHG fluxes from soils. However, very little research has been conducted on the combination of tillage and drainage impacts on GHG fluxes from poorly drained soils. Thus, the present study was conducted in central Ohio with specific objective to assess the influences of long-term (18-year) no-tillage (NT) and chisel-till (CT) impacts on carbon dioxide (CO₂), nitrous oxide (N₂O), and methane (CH₄) fluxes from the soils in plots managed under drained (D) or nondrained (ND) conditions. The experimental site was established on a poorly drained Crosby silt loam soil in 1994 under corn (<i>Zea mays</i> L.)-corn rotation. Measurements of soil CO₂, N₂O, and CH₄ fluxes were conducted biweekly during 2011 and 2012 using the static chamber technique. In 2011, the annual CO₂-C and N₂O-N from NT were 18% and 83%, respectively, lower compared to CT. Similar trends were observed for 2012. Methane fluxes were highly variable in both years. Tillage and drainage influenced seasonal soil GHG emissions; however, differences were not always significant. In general, plots under NT with subsurface drainage produced lower emissions compared to those under CT. Subsurface drainage lowered the emissions compared to those under ND. Results from this study concluded that subsurface drainage in poorly drained soils with long-term NT practice can be beneficial for the environment by emitting lower GHG fluxes compared to tilled soils with no drainage. However, long-term monitoring of these fluxes under diverse cropping systems under poorly drained soils is needed.

Evaluating soil quality under a long-term integrated tillage–water–nutrient experiment with intensive rice–wheat rotation in a semi-arid Inceptisol, India

Long-term sustainability and a declining trend in productivity of rice-wheat rotation in the Indo-Gangetic plain, often direct towards the changes in soil quality parameters. Soil quality is decided through few sensitive soil physical, chemical and biological indicators as it cannot be measured directly. The present investigation was carried out to develop a valid soil quality index through some chosen indicators under long-term influences of tillage, water and nutrient-management practices in a rice-wheat cropping system. The experiment consisted of two tillage treatments, three irrigation treatments, and nine nutrient management treatments for both rice and wheat, was continued for 8 years. The index was developed using expert-opinion based conceptual framework model. After harvest of rice, the CFSQI-P (productivity) was higher under puddled situation, whereas CFSQI-EP (environmental protection) was more under non-puddled condition and 3-days of drainage was found promising for all the indices. No-tillage practice always showed higher soil quality index. The treatments either receiving full organics (100% N) or 25% substitution of fertilizer N with organics showed higher soil quality indices. Puddling, irrigation after 3 days of drainage and substitution of 25% recommended fertilizer N dose with FYM in rice could be practiced for maintaining or enhancing soil quality. No-tillage, two irrigations, and domestic sewage sludge in wheat can safely be recommended for achieving higher soil quality.

Diversity of the bacterial community in the rice rhizosphere managed under conventional and no-tillage practices

Bacterial diversity in the rice rhizosphere at different rice growth stages, managed under conventional and no-tillage practices, was explored using a culture-based approach. Actinobacteria are among the bacterial phyla abundant in the rice rhizosphere. Their diversity was further examined by constructing metagenomic libraries based on the 16S rRNA gene, using actinobacterial- and streptomycete-specific polymerase chain reaction (PCR) primers. The study included 132 culturable strains and 125 clones from the 16S rRNA gene libraries. In conventional tillage, there were 38% Proteobacteria, 22% Actinobacteria, 33% Firmicutes, 5% Bacteroidetes, and 2% Acidobacteria, whereas with no-tillage management there were 63% Proteobacteria, 24% Actinobacteria, 6% Firmicutes, and 8% Bacteroidetes as estimated using the culture-dependent method during the four stages of rice cultivation. Principal coordinates analysis was used to cluster the bacterial communities along axes of maximal variance. The different growth stages of rice appeared to influence the rhizosphere bacterial profile for both cultivation practices. Novel clones with low similarities (89-97%) to Actinobacteria and Streptomyces were retrieved from both rice fields by screening the 16S rRNA gene libraries using actinobacterial- and streptomycete-specific primers. By comparing the actinobacterial community retrieved by culture-dependent and molecular methods, it was clear that a more comprehensive assessment of microbial diversity in the rice rhizosphere can be obtained using a combination of both techniques than by using either method alone. We also succeeded in culturing a number of bacteria that were previously described as unculturable. These were in a phylogenetically deep lineage when compared with related cultivable genera.

Challenging conservation agriculture on marginal slopes in Sehoul, Morocco

AbstractIn Sehoul, Morocco, the use of marginal land for agriculture became a necessity for the local population due to increased poverty and the occupation of the best land by new owners. Desertification poses an additional threat to agricultural production on marginal slopes, which are often stony and degraded. In a participatory process embedded in the EU DESIRE research project, potential sustainable land management measures were selected to address land degradation and desertification. Promising experiences with no-tillage practices elsewhere in Morocco had motivated the Moroccan government to promote conservation agriculture throughout the country. This combination of crop rotation, minimal soil disturbance and soil cover maintenance, however, had not yet been tested on sloping degraded land. Field trials of grazing enclosure combined with no or minimum tillage were conducted on the plots of two farmers, and trial results were analyzed based on stakeholders’ criteria. Results suggest that increased soil cover with barley residues improved rainwater use efficiency and yields only slightly, although soil water was generally enhanced. Soil moisture measurements revealed that no-tillage was favorable mainly at soil depths of 5 cm and in connection with low-rainfall events (&lt;20 mm); under these circumstances, moisture content was generally higher under no-tillage than under conventional tillage. Moreover, stakeholder discussion confirmed that farmers in Sehoul remain primarily interested in animal husbandry and are reluctant to change the current grazing system. Implementation of conservation agriculture is thus challenged both by the degraded, sloping and stony nature of the land, and by the socio-economic circumstances in Sehoul.

Modeling Water Quality Impacts of Cellulosic Biofuel Production from Corn Silage

The growing interest in the use of alternative biomass products for fuel production requires a thorough understanding of the environmental impacts associated with the production of these bioenergy crops. Corn silage is a potential bioenergy feedstock; however, water quality implications for its utilization as a biofeedstock are not understood. The objective of this work was to evaluate water quality impacts associated with corn silage production. The GLEAMS-NAPRA model was used to quantify runoff, percolation, erosion, nitrate-nitrogen, total phosphorus, and pesticide losses attributed to the production of corn silage with and without winter cover crops for two tillage options (conventional tillage and no till) on three Indiana soils. Results revealed that corn silage would generate greater annual surface runoff (1 to 6 mm) and percolation (1 to 20 mm) compared with corn grain and grain plus stover cropping systems. Silage/winter cereal rye cover crop reduced annual surface runoff and percolation and was strongly influenced by increases in evapotranspiration, when compared with continuous silage production. Silage managed with winter cereal rye cover crop influenced water quality by reducing annual nitrate losses with runoff from a low of 14 % to a high of 27 %, with relatively no effect because of tillage management. No-till practice on silage system produced significantly greater phosphorus losses (7.46 to 18.07 kg/ha) in comparison to silage/cereal rye, corn grain, and grain plus stover harvest (p < 0.05). For every 1,000 l of ethanol produced from corn silage, erosion losses ranged from 0.07 to 0.95 t/ha for conventional tillage practices and from 0.06 to 0.83 t/ha for no-till practices. The feasibility of cropping systems such as corn silage/cereal rye could contribute to large-scale biomass production but should be further investigated.

Soil microbial metabolism and invertase activity under crop rotation and no-tillage in North China

Soil samples were collected at both jointing and maturing stages of maize and wheat to compare the effects of 4-year no-tillage (NT) and conventional tillage (CT) on seasonal variations of microbial biomass carbon (C), metabolic quotient, and invertase activity in a sandy loam soil in North China. Soil invertase activity significantly increased (P &amp;lt; 0.05) from summer to spring of the next year and then significantly decreased (P &amp;lt; 0.05) from spring to summer. With a delay of about 3 months, soil microbial biomass C and basal respiration altered in a similar pattern, while microbial metabolic quotient changed on the contrary. Compared with CT, the NT practice significantly increased (P &amp;lt; 0.05) soil organic C content, and tended to result in higher soil microbial biomass C and invertase activity, as well as lower soil microbial metabolic quotient, especially at the jointing stage of maize. Our results indicated that NT might play an important role in the improvement of soil microbial efficiency, especially at the maize seedling season.

Cover Crops and Tillage in a Mature Merlot Vineyard Show Few Effects on Grapevines

Permanent cover crops are commonly used in vineyard floor management because of their beneficial effects to soil and vine health, but studies evaluating their competitive effects on vines have been conducted primarily in nonirrigated vineyards. Future air quality regulations could mandate the use of no-till floor management practices in California’s Central Valley. We evaluated the combined effects of cover crop type (oats alone or oats grown with legumes) and tillage on soil nutrient availability, vine nutrition, growth, and yield characteristics of Vitis vinifera cv. Merlot grown under regulated deficit irrigation in a commercial vineyard from 2008 to 2010. Five treatments were used: Resident Vegetation (RV) + Till, Oats + Till, Oats/Legumes +Till, Oats + NoTill, and Oats/Legumes + NoTill. No differences in soil nutrient availability were found among the treatments. Of the numerous nutritional constituents analyzed on leaf petioles and blades, only NO3-Npetiole was affected by floor management. At nearly all growth stages among all years, NO3-Npetiole of tilled treatments was twice the no-till treatments. At harvest, yield, mean cluster weight, cluster number per vine, and aboveground cover crop biomass differed among treatments in 2009 and/or 2010 but not in the first year (2008); however, responses were not consistent among treatments within each respective year. Importantly, yields were similar from all four cover crop treatments compared to the typical management (RV + Till), suggesting that use of cover crops and/or no-till practices may be implemented in an irrigated vineyard with little immediate effect on grape productivity in mature vineyards.

Assessing soil carbon storage rates under no-tillage: Comparing the synchronic and diachronic approaches

No-tillage (NT) practices with crop residue mulching are seen as an effective way to accumulate soil carbon (C). The rate of soil C accumulation can be determined by measuring soil C stocks over time (diachronic approach) or along a chronosequence that substitutes spatial history differences for time differences (synchronic approach). The objective of this communication is to compare the diachronic and synchronic approaches for determining the rates of soil C storage under NT in the Cerrado region of Brazil. In 2003 and 2007, soil C stocks (0–20cm) were determined in three NT fields with 5, 9 and 17 years of NT adoption in 2007 (NT-5, NT-9 and NT-17, respectively), one conventionally tilled field (CT, 30 years of tillage in 2007) and one native Cerrado plot (CE) in Rio Verde (Goiás state, Brazil). Soil C accumulation rates were calculated following both the synchronic and diachronic approach. Results from the synchronic approach showed that 30 years of cropping under CT depleted the soil C stock to 34.4MgCha−1, which is a decrease of about 27% of the original levels observed under the native vegetation (CE, 47.1 and 47.3MgCha−1, respectively, in 2003 and 2007). Instead, NT adoption had been accumulating soil C through the evaluated years. Soil C stocks measured under NT areas in 2003 and 2007 were 29.9 and 31.3MgCha−1 (NT-5), 33.4 and 34.4MgCha−1 (NT-9) and 45.8 and 46.4MgCha−1 (NT-17), respectively. Much more moderate rates of soil C accumulation were observed diachronically (0.12–0.28MgCha−1year−1) than with the synchronic approach (1.33 and 1.27MgCha−1year−1 in 2003 and 2007, respectively). Soil C stocks under CE between 2003 and 2007 (in the diachronic approach) did not change, indicating that diachronic measurements were accurate. Thus, it appears to be very difficult to eliminate all non-wanted sources of soil C variation (i.e. soil texture, land-use history) analysing the soil C accumulation in a chronosequence (synchronic approach). In spite of a time span of years between sampling dates, our results suggest the need for using the diachronic approach when assessing soil C changes under altering land-use or management patterns. Increasing the number of diachronic assessments may also help the parameterization of process-oriented models for exploring the effects of no-tillage systems on soil C storage rates more accurately.

Soil-Specific Inventories of Landscape Carbon and Nitrogen Stocks under No-till and Native Vegetation to Estimate Carbon Offset in a Subtropical Ecosystem

Inventories of C and N footprints on a landscape scale are essential tools for estimating C offsets from agricultural emissions. Therefore, the aims of this study conducted in the subtropical humid ecosystem in southern Brazil were to: (i) conduct a soil-specific inventory of landscape soil C and N stocks with reference to soil order, soil texture, and land use/management type; (ii) estimate accretion rates for soil organic C (SOC) and total N (TN) for areas managed under no-till (NT) practices management with reference to native vegetation (NV) based on this inventory; (iii) generate a map of C stocks for each land use system; and (iv) calculate estimated C offset for the region through the use of NT compared to conventional tillage (CT). Soil samples were collected at 324 points to a 1-m depth from the entire region. Soil texture and duration of NT had a strong influence on C and N stocks. The average soil C stock across all types of soils for depths of 0-40 and 40-100 cm was 57.0 and 43.0%, respectively. The extrapolation of C stored in the 0- to 40-cm depth based on the NT management for 11 and 20 yr for 1.52 million hectare (Mha) was 9.08 ± 0.62 Tg (1 Tg = 1012 g) representing 11.9% of the C stored in all soil orders. The long-term of C sink capacity by conversion of arable land from CT to NT in this region is 33.2 Tg of CO2, with the C offset of 22.5% of all anthropogenic emissions. (Resume d'auteur)

Long-term effects of no-tillage management practice on soil organic carbon and its fractions in the northern China

The influence of different tillage practices on soil organic carbon levels is more significant under long-term tillage compared to short-term tillage. Despite the great interest in the effect of no-tillage (NT) management practice on carbon sequestration, the long-term effect of NT practice on soil organic carbon and its fractions in northern China remain unclear. We evaluated the long-term effects (after 17years) of NT and conventional tillage (CT) practices on soil organic carbon and its fractions at different depths ranging from 0 to 60cm using a cinnamon soil in Shanxi, China. A randomised block design with three replications was used to evaluate both the tillage and its effects on the yield performance of winter wheat (Triticum aestivum L.). After 17years, the soil organic carbon (SOC) concentration in the NT soil was greater than that of the CT soil, but only in the layer that was located between 0 and 10cm. There was a significant accumulation of SOC (0–60cm) in the NT soil (50.2MgCha−1) compared to that observed in the CT soil (46.3MgCha−1). The particulate organic matter C (POM-C), dissolved organic C (DOC), and microbial biomass C (MBC) levels in the 0–5cm layer under NT treatment were 155%, 232%, and 63% greater, respectively, compared to the CT treatment. The POM-C, DOC, and MBC in the 5–10cm layer under NT treatment were 67%, 123%, and 63% greater, respectively, compared to the CT treatment. Below 10cm, the labile carbon observed in the NT treatment did not differ from that of the CT treatment. Significantly positive correlations were observed between the SOC and the labile organic C fractions. Moreover, the winter wheat (T. aestivum L.) yield increased 28.9% in the NT treatment compared to the CT treatment. The data show that NT is an effective and sustainable management practice that improves carbon sequestration and increases soil fertility, resulting in higher winter wheat yields in the rainfed dryland farming areas of northern China.

Use of a Surrogate to Evaluate the Impact of Tillage on the Transport of Steroid Hormones from Manure-Amended Agricultural Fields

<abstract><title><italic>Abstract.</italic></title> Beef feedlot manure distributed to row crop production areas is a potential surface water contaminant source of the steroid hormones commonly used in beef cattle production. This article reports on research conducted at the University of Nebraska Haskell Agricultural Laboratory near Concord, Nebraska, in July 2009. Manure, collected from beef feedlot pens, was stockpiled for ten months prior to application to a row crop field. Previous research identified that the detection frequency of steroid hormones in beef manure varies greatly. Thus, a surrogate (17α-ethynylestradiol, EE2) was applied at a rate of 75 g ha^-1 to ensure detectable concentrations in surface runoff samples. EE2 was applied directly to beef cattle manure and to bare soil. The EE2 and manure were either incorporated using a single disk treatment (T) or left on the soil surface in a no-till practice (NT). A rainfall simulation experiment was conducted 24 h after manure and EE2 incorporation using a factorial design consisting of tillage, manure, and EE2 treatments. Runoff samples were collected at 5 min intervals during a 30 min runoff period for each plot. Results indicated 96% less EE2 mass transport from disk-tilled plots compared to no-till. The greatest loss of EE2 was 156 and 6 mg ha^-1 from no-till and disked plots, respectively. Results of this study showed that a single-pass disk tillage treatment can limit the overland transport of steroid hormones from crop production areas.

A wide view of no-tillage practices and soil organic carbon sequestration

Many believe that conservation tillage practices could increase the sequestration of atmospheric carbon dioxide into agricultural soils and this sequestered carbon may partially offset the greenhouse gas effect and thus reduce the impact of global warming. Recent advances in soil carbon (C) and greenhouse gas analysis have made it possible to evaluate the impacts of conservation tillage on C sequestration from various perspectives. Although conservation tillage favors soil and water conservation, there are biased estimates of C sequestration associated with conservation tillage, and it is particularly an issue for a “pure” no-tillage (NT) system. Accordingly, this paper presents an overview of the progress achieved in evaluating C sequestration in no-till (the extreme type of conservation tillage) and conventional tillage production systems. In addition to extended discussion of how soil sampling and calculations could influence the estimates of C gains or losses in no-till versus conventional tilled soil, this review will also focus on following aspects, including (1) the impact of NT on crop yields which governs organic C inputs to soil from crop residue, (2) the impact of NT on soil organic C mineralization which is a major pathway of soil C output, and (3) the roles of the initial levels of C stocks and soil erosion rates which are crucial for estimating soil C sequestration under different tillage systems. Many soil C studies have indicated that the impacts of NT on soil C sequestration are compounded by many factors and should not be generalized.

Nitrous oxide and methane fluxes from a rice–wheat crop rotation under wheat residue incorporation and no-tillage practices

Crop residue incorporation and no-tillage are recommended as management practices and are being increasingly adopted in the agricultural sector. However, few studies have assessed the extent to which these practices integrate annual carbon and nitrogen trace gas fluxes and grain yield. We investigated the effect of wheat straw incorporation and no-tillage on nitrous oxide (N2O) and methane (CH4) fluxes from a rice–wheat system in southeast China, using year-round field measurements. Compared to the treatment with synthetic nitrogen fertilizers alone, the wheat straw incorporation reduced the N2O emissions by 38% (P < 0.05) and increased the CH4 emissions by 74% (P < 0.05) during the annual rotation cycle. Compared to the conventional tillage, no-tillage prior to wheat sowing enhanced the N2O emissions by an average of 61% (P < 0.05), irrespective of residue incorporation. The CH4-C emissions that were induced by the wheat straw comprised 6% of the residue-carbon incorporated during the rice season. As a result of the stimulating effect of wheat straw incorporation on CH4 fluxes, the annual aggregate emissions of N2O and CH4 with straw incorporation (10.7 Mg CO2-eq ha−1 yr−1 or 725 kg CO2-eq Mg−1 grain yield) were usually higher than those with no residue incorporation (7.6 Mg CO2-eq ha−1 yr−1 or 545 kg CO2-eq Mg−1 grain yield), irrespective of the tillage practice. Nevertheless, the changes in greenhouse gas emissions are notably only the transient response of the rice–wheat system after crop residue incorporation and tillage conversion, which may not necessarily represent equilibrium conditions for this agro-ecosystem over the long term.

Greening summer fallow with legume green manures: On-farm assessment in north-central Montana

Replacing summer fallow practices with annual legumes as green manures (LGMs) may increase the sustainability of northern Great Plains wheat (Triticum aestivum L.) systems. Viability hinges on soil water use management and realizing biologically fixed nitrogen (N) benefits. Plot-scale research has shown that managing LGMs with first-flower stage termination and no-till practices conserves soil water and that rotational N benefits can increase wheat grain quality. Nonetheless, farmer adoption of LGMs has been negligible. To better understand this practice and its regional adoption potential, we conducted a participatory on-farm assessment of no-till LGM versus summer fallow–wheat rotations in north-central Montana. Soil water and nitrate (NO3) levels to 0.9 m (3 ft), potentially mineralizable N (PMN) to 0.3 m (1 ft), wheat yields, conservation potential, and producer adoption challenges were assessed at five farmer-managed, field-scale sites. Compared to fallow, LGM treatment diminished mean wheat yield by 6% (0.24 Mg ha−1 [3.7 bu ac−1]), diminished grain protein by 9 g kg−1 when wheat was fertilized with N (p = 0.01), and increased grain protein by 5 g kg−1 when wheat was unfertilized (p = 0.08). Small soil water depletions in LGM treatments below fallow at wheat seeding (17%; 30 mm [1.2 in]) and near-record high rainfall during the wheat growing season (280 to 380 mm [11 to 14 in]) suggest that LGMs likely did not limit soil water available to wheat in this study. Soil NO3 levels following LGMs were 29% to 56% less than summer fallow at wheat seeding, and conversely, greater PMN was detected in LGM treatments at 3 of 5 sites. We theorize that N mineralization from LGMs was insubstantial by wheat seeding due to dry soil conditions and low LGM biomass N contributions, consequently affecting wheat yield potential due to limited early season soil N availability. LGMs increased average use efficiency of available N by 24% during the wheat year and increased total residue carbon (C) and N returned to soils by 260 and 26 kg ha−1 (232 and 23 lb ac−1), respectively, after two years. Our results illustrated that farmers viably managed LGM soil water use with early termination and no-till practices but that LGM adoption may be hindered by a lack of immediate wheat yield or protein benefits from legume-N and seed costs for LGMs. Appropriate incentives, management strategies, and yield benefit expectations (short versus long term) should be fostered to increase the adoption potential of this N-economizing soil and water conservation strategy.

Long-term Tillage and Nitrogen Fertilization Effects on Soil Properties and Crop Yields

Long-term Tillage and Nitrogen Fertilization Effects on Soil Properties and Crop Yields