Increasing Tillage Intensity Research Articles

Long‐term conservation and conventional tillage systems impact physical and biochemical soil health indicators in a corn–soybean rotation

AbstractAgricultural management practices tend to influence soil structure stabilization, mediating many physical, chemical, and biological processes in soils. Therefore, understanding the long‐term effects of management practices on various soil health indicators is crucial to develop sustainable agricultural practices. This study aimed to assess the long‐term conventional and conservation tillage effects on soil physical (aggregates) and biochemical (soil organic carbon [SOC], enzymes, and microbial biomass) parameters under a range of tillage practices in a corn–soybean rotation in Nebraska. The experiment was conducted at two locations as follows: (1) Concord site (36 years) with the three treatments: no‐till (NT), disk, and moldboard plow; and (2) Lincoln site (40 years) with four tillage treatments: NT, double disk, chisel, and moldboard plow. Results showed that NT at both sites significantly increased SOC concentration by 24%–66% compared to moldboard plow. Similarly, double disk tillage increased SOC by 54% compared to the moldboard plow at the Lincoln site. Arylsulfatase, β‐glucosidase, hot‐ and cold‐water extractable carbon, microbial biomass carbon, and nitrogen concentrations significantly decreased with the increased tillage intensity at both sites. This implies that the NT increased these parameters compared to the disk and moldboard plow. However, aggregate size fraction 0.053–0.25 mm was the only parameter higher under moldboard plow (20.8%) than NT. Overall, the results from these long‐term studies indicate that NT, and to a lesser extent the reduced tillage practice of disk till, can improve soil health more than conventional tillage practices under a corn–soybean cropping system, suggesting the adoption of sustainable agricultural practices to improve soil health.

Extracted samples and in situ soil investigations to assess the effects of different land use and tillage management practices on soil organic matter composition

AbstractThe effects of land use change on soil organic carbon (SOC) content have been investigated extensively. However, little research has been conducted on how soil organic matter (SOM) chemistry changes under different land use management practices, particularly with different soil cultivation methods. Thus, in this study, we compared the effects of various land use management practices, including six medium‐term tillage practices, namely no‐tillage (zero‐tillage), disking, shallow cultivation, deep cultivation, ploughing, and loosening, and a natural ecosystem, namely tree line, on SOM composition. The present study examined Chernozem soils during spring and autumn under varying land uses in randomised complete block designs, with four replicates at depth increments of 0–10 cm. The SOM composition was characterised using diffuse reflectance infrared Fourier transformat spectroscopy (DRIFTS) and ultraviolet–visible spectroscopy (UV‐VIS). More intensive tillage operations resulted in larger SOM composition changes. Overall, conservation tillage, namely no‐tillage, disking, shallow cultivation, and deep cultivation, SOM was more like the tree line soil than the soil under conventional tillage. Both DRIFTS and UV‐VIS revealed that tree line soil had the lowest aromaticity (15%) and, therefore, a lower decomposition rate and higher SOM recalcitrance compared with the cropland soil (27%). After observing the relationship between tillage operation and aromaticity, aromaticity increased with increasing tillage intensity. This study demonstrates that land use can alter the structure and stability of SOM compounds. We observed that afforestation is similar to conservation tillage, and results are obtained quickly (<40 years). Hence, regeneration agriculture and conservation tillage may be the superior solutions for increasing SOM, sustainable agriculture, and food security in current soil and climate conditions. In addition, DRIFTS measurements of bulk soil provided more detailed information on the quality and stability of SOM than UV‐VIS measurements.

Soil Organic Carbon Pools in Rice Growing Inceptisols of Northeast India

ABSTRACT Estimation of soil organic carbon (SOC) stock and its pools is important for understanding C budgeting and ecosystems services of any land use. The present study was conducted to quantify SOC stock and its pools of different oxidizability (very labile, labile, less labile and non-labile C), microbial biomass C and mineralizable C at different depths (0–0.15, 0.15–0.30 and 0.30–0.50 m) of selected 26 rice growing Inceptisols located in the subtropical Manipur valley, India. Results of this study showed that organic C stock in 0–0.50 m depth of the rice growing Inceptisols varied from 55.7 to 133.5 Mg ha−1 and there was a decrease in SOC stock along depth. The rice growing Inceptisols under subtropical climate of northeast India are characterized by cooler climatic conditions and soil acidity, which are favorable for SOC accumulation. The study also showed that more than two-third (72.0%) of SOC is present in active pools with rapid turnover. Therefore, much of the SOC in these soils is very susceptible to changes in management practices such as increased tillage intensity, inappropriate cropping without legume and inadequate fertilization and in weather conditions such as increased temperature.

Reduced Risk of Oat Grain Contamination with Fusarium langsethiae and HT-2 and T-2 Toxins with Increasing Tillage Intensity.

Frequent occurrences of high levels of Fusarium mycotoxins have been recorded in Norwegian oat grain. To elucidate the influence of tillage operations on the development of Fusarium and mycotoxins in oat grain, we conducted tillage trials with continuous oats at two locations in southeast Norway. We have previously presented the content of Fusarium DNA detected in straw residues and air samples from these fields. Grain harvested from ploughed plots had lower levels of Fusarium langsethiae DNA and HT-2 and T-2 toxins (HT2 + T2) compared to grain from harrowed plots. Our results indicate that the risk of F. langsethiae and HT2 + T2 contamination of oats is reduced with increasing tillage intensity. No distinct influence of tillage on the DNA concentration of Fusarium graminearum and Fusarium avenaceum in the harvested grain was observed. In contrast to F. graminearum and F. avenaceum, only limited contents of F. langsethiae DNA were observed in straw residues and air samples. Still, considerable concentrations of F. langsethiae DNA and HT2 + T2 were recorded in oat grain harvested from these fields. We speculate that the life cycle of F. langsethiae differs from those of F. graminearum and F. avenaceum with regard to survival, inoculum production and dispersal.

Soil Disturbance Impact on Crop Ergothioneine Content Connects Soil and Human Health

Ergothioneine (ERGO) is a potent antioxidant and anti-inflammatory amino acid that is produced in nature mainly by non-yeast fungi, cyanobacteria, and mycobacteria. Mounting evidence suggests that ERGO can be considered a longevity vitamin that can mitigate chronic diseases of aging and thereby increase life expectancy. Humans must obtain ERGO from their diet, and it is therefore important to know which foods contain it. Although ERGO is not produced by plants it is found in plant products such as grain, apparently because detrital or symbiotic soil fungi pass on ERGO to plants through their roots. Besides differences between plant species in their ability to accumulate ERGO, how they are managed might also affect its concentration. Soil tillage has been shown to reduce soil fungal biomass, and therefore ERGO contents in maize, soybeans, and oats grown in soil managed with annual moldboard plowing (most intensive), chisel/disking (less intensive), or no-tillage (least intensive) in crop rotation were compared. ERGO concentrations declined in all three crops as tillage intensity increased, with reductions from no till to moldboard plow of approximately 30% in all three crops. Because crop yield was also negatively impacted by intensive tillage, ERGO yield per hectare was reduced even more due to increasing tillage intensity. This study is one of the first to show that soil health improving practices that minimize soil disturbance can directly enhance a key dietary factor associated with long-term human health.

Cropping system partially offsets tillage-related degradation of soil organic carbon and aggregate properties in a 30-yr rainfed agroecosystem

Soil tillage increases the susceptibility of agricultural soils to erosion and organic carbon losses, but tillage effects could be mitigated through other management practices such as crop rotation. Here, we evaluated the 30-year impacts of tillage intensity and cropping system on surface soil bulk density, nutrient availability, dry aggregate size distribution, and water-stable aggregation. This study was established in 1980 in eastern Nebraska USA, and included six tillage treatments of varying intensity (no-till, ridge till, disk till, subsoil rip, chisel plow, moldboard plow) and four crop rotation treatments (continuous soybean [Glycine max (L.) Merr.]; soybean-corn [Zea mays L.]; corn-soybean, continuous corn) in a randomized block design with six replicates. Surface soils were sampled in 2011 and soil aggregate properties assessed, including occluded particulate organic matter (oPOM) in micro/macroaggregates (0.053–0.5 mm) and mega-aggregates (>2.0 mm). Because of significant treatment differences in bulk density, soil properties were converted to an equivalent soil mass (ESM) basis to more accurately assess management effects. After 30 years, only the main effects of tillage and crop rotation were significant for most measured soil properties. Surface soil organic carbon (SOC) stocks (ESM for ∼0−30 cm soil depth) decreased with tillage intensity, and stocks were higher when corn was included in the cropping system. Dry aggregate size distributions shifted towards smaller size classes as tillage intensity increased and whenever corn was included in the cropping system. As a result, aggregate mean weight diameter (mm) followed a similar trend. Soil stocks of water-stable mega-aggregates also decreased with increasing tillage intensity. In near-surface soils (0–7.5 cm), highly-erodible aggregate oPOM was highest in no-till soils and was more sensitive to tillage disturbance (56–69% loss) than mega-aggregate oPOM (5–35% loss). Even in no-till soils, highly-erodible aggregate oPOM concentrations decreased under continuous corn compared to rotated systems likely due to greater frequency of fertility management-related soil disturbances (i.e. fertilizer injection annually vs every two years). These results suggest that cropping systems that maximize plant carbon inputs can partially mitigate soil erosion risks due to long-term tillage, but that other crop management-related soil disturbances (i.e. method of fertilizer application) could limit the mitigating effect of cropping system.

Effects of long-term conventional and conservational tillage systems on biochemical soil health indicators in the Mediterranean region

ABSTRACT Improved soil health is essential to sustain agricultural production. Therefore, understanding the effects of management on soil health is crucial to implement new agricultural practices. This study aimed to assess the effects of long-term tillage systems on biochemical indicators of a Typic Haploxerert soil under winter wheat-soybean-corn rotation in the Mediterranean region of Turkey. The experiment consisted of two conventional (CT), three reduced (RT), no-tillage (NT), and a strategic tillage practice. The biochemical indicators were total nitrogen (TN), total carbon (TC), soil organic carbon (SOC), microbial biomass carbon (MBC), potential mineralizable nitrogen (PMN), microbial quotient (qM), beta-glucosidase enzyme activity (BGA), and carbon sequestration (Cs) potential. The SOC significantly decreased with the increased tillage intensity, while the tillage had a little effect on PMN, with its highest concentration (78.2 mg kg−1) occurring in the NT. The qM was the only indicator found to be higher under CT than RT and similar to the NT. The BGA peaked in NT which was 460.2 and 536.3% higher than that of the CT. The results showed that SOC, MBC, PMN, BGA and Cs were enhanced with the NT and RT systems which favor sustainability of agricultural production.

Tillage impacts on soil aggregation and aggregate-associated carbon and nitrogen after 49 years

Intensive tillage systems that feature a moldboard plow (MP) or a chisel-disk (CD) can degrade soil structure. No-till (NT) can improve soil structure and can increase soil carbon (C) but the effect of alternating (AT; 2-yr no-till and 1-yr MP) on soil aggregation and soil C is less understood. This study evaluated the effects of four tillage practices including MP, CD, AT, and NT on soil physical and chemical properties and corn (Zea mays L.) yield. Percentage of dry medium (1−2 mm) aggregates was highest in NT, but contrary to our hypothesis, MP had a high percentage of dry large (2–4.75 mm) aggregates similar to NT. Increased tillage intensity decreased aggregate stability indicating that a high percentage of large sized aggregates in MP does not necessarily translate into aggregate stability. Aggregate-associated carbon (C) and nitrogen (N) percentages were higher in NT than other treatments but the C:N ratio was similar among all treatments at all depths. Disturbing the soil periodically (AT) disrupted C or N accrual compared with continuous NT while AT had the lowest amount of aggregate associated permanganate oxidizable C (POXC) accumulation. Therefore, practicing no-till and periodically deep-tilling can be as detrimental to soil structure as practicing yearly reduced tillage (CD), if not more. No-till greatly increased the C, N and POXC concentrations only in the topsoil layer (0−5 cm), highlighting a need for additional management tactics to increase C, N and POXC concentrations deeper in the soil profile. Tillage practices did not significantly influence corn yield. We concluded that AT offered improvements in aggregate size and stability, but was outperformed by CD, and that benefits of NT are limited to the topsoil. Therefore, integrated management practices are needed to build soil organic C (SOC) beyond topsoil. When a long-term NT system is disturbed, it could result in a greater loss of built soil resources such as soil C, N, and POXC. Future research should focus on evaluating the effect of alternating NT with CD on soil aggregation, and SOC buildup in combination with integrated practices with potential to build C beyond topsoil.

Impacts of tillage practices on soil carbon stocks in the US corn-soybean cropping system during 1998 to 2016

Tillage alters the thermal and wetness conditions in soil, which facilitates soil organic matter oxidation and water transportation, leading to rapid depletion of soil carbon (C). Little is known about tillage intensity change (TIC) and its impacts in the US corn-soybean rotation system over the past two decades. Using time-series tillage maps developed from a private survey and a process-based land ecosystem model, here we examined how tillage intensity has changed across the nation and affected soil organic carbon (SOC) storage from 1998 to 2016. Results derived from the combination of tillage survey data and cropland distribution maps show that total corn-soybean area consistently increased from 62.3 Mha in 1998 to 66.8 Mha in 2008 and to 73.1 Mha in 2016, among which the acreage under no-till system increased from 16.9 Mha in 1998 to 28.9 Mha in 2008, while conservation and conventional tillage decreased by 3.8 and 3.9 Mha, respectively. The extent of no-till practice in corn-soybean lands shrank by 2.6 Mha from 2008 to 2016, while conservation and conventional tillage increased by 2.8 and 6.1 Mha in the same period. Modeling simulations reveal that historical tillage practices led to a soil C loss of 10.3 (spring till only) to 15.2 (tilled in both spring and fall) Tg C yr−1 in the study area from 1998 to 2016. In addition, reduced tillage intensity in corn-soybean cropland contributed to SOC accumulation at 1.0 Tg C yr−1 (1.6 g C m−2 yr−1) from 1998 to 2008, but the SOC gain was offset by SOC reduction at 2.4 Tg C yr−1 (3.4 g C m−2 yr−1) from increased tillage intensity during the period 2008–2016. For both periods, TIC-induced hydrological C loss accounted for 15% of the SOC change, while the rest was attributed to gaseous-C loss.

Traditional manual tillage significantly affects soil redistribution and CO2 emission in agricultural plots on the Loess Plateau

Traditional manual tillage using hand tools is widely used by local farmers in hilly and mountainous regions in China and many South-east Asian countries. Manual tillage could result in severe soil erosion, redistributing slopes from upslope areas (erosion) to lower slopes (deposition). This soil redistribution process may potentially affect the soil carbon cycle, but few studies have quantified soil CO2 emission under different manual tillage practices. In the present study we evaluated the soil redistribution and its effects on in situ CO2 emission as affected by manual tillage of different intensities on three short slopes representing typical cultivated landscapes on the Loess Plateau. Soils were removed at 2, 6 and 10 cm depths by three types of hand tools, namely a hoe, mattock and spade respectively, from the upslope and subsequently accumulated at the downslope to simulate soil erosion and deposition processes by traditional manual tillage. Across the tilled hillslopes, soil CO2 emission was reduced at sites of erosion but enhanced at sites of deposition. Tillage with greater intensity (i.e. hoeing < mattocking < spading) resulted in greater change in CO2 emission. This change in soil CO2 emission was largely associated with the depletion of soil organic carbon (SOC) stocks at erosion sites and the increments of SOC available for decomposition at deposition sites. Moreover, with increasing tillage intensity, soil redistribution by manual tillage shifted the hillslope from a C sink to C neutral or even a C source. Furthermore, manual tillage resulted in substantial changes in soil CO2 emission and redistributed soil in amounts that dwarf animal-powered tillage. The results of the present study imply that manual tillage-induced soil redistribution could have a large effect on the C balance across the local landscape and therefore may have considerable implications for estimates of regional and global C budgets.

Impact of tillage erosion on water erosion in a hilly landscape

Little has been known of the interaction between tillage erosion and water erosion, while the two erosion processes was independently studied. Can tillage-induced soil redistribution lead to exaggerated (or retarded) runoff flow and sediment concentrations in steeply sloping fields? A series of simulated tillage and artificial rainfall events were applied to rectangular runoff plots (2m×8m) with a slope of 15° to examine the impacts of tillage erosion intensities on water erosion in the Yangtze Three Gorges Reservoir Area, China. Mean flow velocity, effective/critical shear stress, and soil erodibility factor K were calculated to analyze the differences in hydrodynamic characteristics induced by tillage. Our experimental results suggest that mean runoff rates were 2.26, 1.19, and 0.65Lmin−1 and that mean soil detachment rates were 1.53, 1.01, and 0.61gm−2min−1 during the 70-min simulated rainfall events for 52-, 31-, and 10-year tillage, respectively. A significant difference (P<0.05) in cumulative detachment amounts was found among different tillage intensities. Compared with the soil flux of 0kgm−1, cumulative detachment amounts for the soil fluxes of 9.86 and 24.72kgm−1 increased by 40.02% and 100.94%, respectively, during the 30-min rainfall event. The results imply that soil and water losses tended to increase with increasing tillage intensity. A significant difference in mean flow velocity occurred near the upper and lower slope boundaries of the field, while significant differences (P<0.05) in runoff depth and effective shear stress were observed among different slope positions. Soil erodibility factor K for the soil fluxes of 9.86 and 24.72kgm−1 were 2.40 and 5.11 times higher, respectively, than that for the soil flux of 0kgm−1. As tillage intensity increased, critical shear stress trended to gradually decrease for all soil fluxes. Our results indicate that tillage erosion increases soil erodibility and delivers the soil for water erosion in sloping fields, accelerating water erosion.

Soil compaction and controlled traffic considerations in Australian cotton-farming systems

A literature review was conducted to collate best practice techniques for soil compaction management within cotton-farming systems in Australia. Universally negative effects of traffic-induced soil compaction on the whole-farm system and the wider environment include: (i) increased gap between attainable and potential yields, (ii) increased costs of energy and labour, (iii) reduced fertiliser-use efficiency, (iv) reduced water use efficiency (irrigation and rainfall), (v) increased tillage intensity. Knowledge gaps that merit research priority, and research strategies, are suggested. These include: (i) identifying wider impacts on farm economics to guide decision-making and development of decision support systems that capture the effects of compaction on fertiliser, water, and energy use efficiency; (ii) predicting risks at the field or subfield scale and implementing precision management of traffic compaction; (iii) canopy management at terminal stages of the crop cycle to manipulate soil-moisture deficits before crop harvest, thereby optimising trafficability for harvesting equipment; (iv) the role of controlled traffic farming (CTF) in mitigating greenhouse gas emissions and loss of soil organic carbon, and in enhancing fertiliser and water-use efficiencies; (v) recent developments in tyre technology, such as low ground-pressure tyres, require investigation to assess their cost-effectiveness compared with other available options; and (vi) catchment-scale modelling incorporating changes in arable land-use, such as increased area under CTF coupled with no- or minimum-tillage, and variable rate technology is suggested. Such modelling should assess the potential of CTF and allied technologies to reduce sediment and nutrient losses, and improve water quality in intensively managed arable catchments. Resources must be efficiently managed within increasingly sophisticated farming systems to enable long-term economic viability of cotton production. Agronomic and environmental performance of cotton farming systems could be improved with a few changes, and possibly, at a reasonable cost. Key to managing soil compaction appears to be encouraging increased adoption of CTF. This process may benefit from financial support to growers, such as agri-environmental stewardships, and it would be assisted by product customisation from machinery manufacturers.

Soil organic carbon and microbial communities respond to vineyard management

AbstractThe farming practices in vineyards vary widely, but how does this affect vineyard soils? The main objective of this study was to evaluate the effects of vineyard management practices on soil organic matter and the soil microbial community. To this end, we investigated three adjacent vineyards in the Traisen valley, Austria, of which the soils had developed on the same parent material and under identical environmental/site conditions but were managed differently (esp. tillage, fertilizer application, cover crops) for more than 10 yrs. We found that topsoil bulk density (BD) decreased with increasing tillage intensity, while subsoil BD showed the opposite trend. Soil organic carbon (SOC) stocks in 0–50 cm depth increased from 10 kg m−2 in an unfertilized and frequently tilled vineyard to 17 kg m−2 in a regularly fertilized but less intensively tilled vineyard. Topsoil microbial biomass per unit SOC, estimated by the sum of microbial phospholipid fatty acids (PLFAs), followed this trend, albeit not statistically significantly. Principal component analysis of PLFA patterns revealed that the microbial communities were compositionally distinct between different management practices. The fungal PLFA marker 18:2ω6,9 was highest in the vineyard with the lowest amount of extractable Cu (by 0.01 m CaCl2), and the bacterial‐to‐fungal biomass ratio was positively correlated with extractable Cu. Our results indicate that tillage and fertilizer application of vineyards can strongly affect vineyard soil properties such as BD and SOC stocks and that the application of Cu‐based fungicides may impair soil fungal communities.

Dryland Soil Carbon and Nitrogen after Thirty Years of Tillage and Cropping Sequence Combination

Little is known about the long‐term management impact on soil C and N contents in the northern Great Plains. We evaluated the 30‐yr effect of tillage and cropping sequence combination on dryland crop biomass yield and soil bulk density, soil organic carbon (SOC), soil inorganic carbon (SIC), soil total nitrogen (STN), NH4–N, and NO3–N contents at the 0‐ to 120‐cm depth in a Dooley sandy loam (fine loamy, mixed, frigid Typic Argiboroll) in eastern Montana. Treatments were no‐till continuous spring wheat (Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat–barley (Hordeum vulgare L., 1984–1999) followed by spring wheat–pea (Pisum sativum L., 2000‐2013) (FSTW–B/P), and spring till spring wheat–fallow (STW–F, traditional system). Mean annualized crop biomass returned to the soil was 23 to 30 % greater in NTCW, STCW, FSTCW, and FSTW–B/P than STW–F. At 0 to 7.5 cm, bulk density was 13 to 21% greater in STW–F, but SOC, SIC, and STN were 12 to 98% greater in STCW than other treatments. Ammonium‐N and NO3–N contents were 25 to 74 % greater in FSTCW than other treatments. At other depths, SOC, SIC, STN, NH4–N and NO3–N contents varied among treatments. Reduced tillage with increased crop residue returned to the soil increased soil C and N storage in NTCW and STCW, but increased tillage intensity increased mineral N content in FSTCW compared with STW–F. Improved management practices, such as NTCW and STCW, may be adopted to improve dryland soil C and N stocks.

Changes in soil organic carbon and aggregate stability after conversion to conservation tillage for seven years in the Huang-Huai-Hai Plain of China

Soil aggregate stability and organic carbon (OC) are regarded as effective indicators of soil structure and quality. A long-term field experiment was established in 2006 to examine the influence of tillage systems on soil aggregation and OC in a sandy loam soil in the Huang-Huai-Hai Plain of China. The study involved eight treatments: plowing every year with (TS) and without residue (T), plowing every 2 years with (2TS) and without residue (2T), plowing every 4 years with (4TS) and without residue (4T), and no plowing with (NTS) and without residue (NT). In 2013, soil samples were collected at depths of 0–5, 5–10 and 10–20 cm, and separated into three aggregate-size classes: macroaggregates (>250 μm), microaggregates (53–250 μm) and the silt+clay fraction (<53 μm) using wet sieving method. Soil parameters measured were water-stable aggregates, geometric mean diameter (GMD), mean weight diameter (MWD) and OC concentrations in different aggregate-size fractions and in bulk soil. The tillage treatments significantly (P<0.05) influenced soil aggregate stability and OC distribution. Higher MWD and GMD were observed in 2TS, 4TS and NTS as compared to T. With increasing soil depth, the amount of macroaggregates and MWD and GMD values were increased, while the proportions of microaggregates and the silt+clay fraction were declined. The OC concentrations in different aggregate fractions at all soil depths followed the order of macroaggregates>microaggregates>silt+clay fraction. In the 0–5 cm soil layer, concentrations of macroaggregate-associated OC in 2TS, 4TS and NTS were 14, 56 and 83% higher than for T, whereas T had the greatest concentration of OC associated with the silt+clay fraction in the 10–20 cm layer. Soil OC concentrations under 4TS and NTS were significantly higher (P<0.05) than that of T in the 0–10 cm layer. Residue retention promoted formation of macroaggregates, increased macroaggregate-associated OC concentrations and thus increased total soil OC stock. The macroaggregate-associated OC was positively correlated (R2=0.96) with soil OC concentration, while the silt+clay fraction-associated OC was negatively correlated (R2=0.82) with soil OC concentration. The concentration of soil OC was positively correlated with MWD (R2=0.94) and GMD (R2=0.92). We concluded that increasing tillage intensity led to a loss of carbon (C)-rich macroaggregates and an increase of C-depleted silt+clay fraction. The conservation tillage system, especially NTS and 4TS, increased soil aggregate stability and promoted OC accumulation in macroaggregates, provided the potential to improve soil C sequestration and soil structure in the Huang-Huai-Hai Plain of China.

Effects of tillage and biomass on soil quality and productivity of lowland rice cultivation by small scale farmers in North Eastern India

Intensive tillage-based production systems along with residue removal, grazing and/or burning of crop residues/biomass and poor nutrient replenishment through inadequate fertilizer and manure use are the major causes of soil degradation and unsustainable agriculture in hills of North Eastern India. Thus, a 4-year study (2003–07) was conducted during rainy (wet) seasons at Indian Council of Agricultural Research (ICAR) Research Complex for North Eastern Hill (NEH) Region, Umiam, India (950m a.s.l.). Objective of the study was to assess the effect of different tillage systems (individual or combinations of spading, trampling and hand weeding) on rice (Oryza sativa L.) productivity and soil (Typic Paleudalf) quality under in-situ residue management in lowland conditions. Transplanting in manually weeded unpuddled field was termed no-till (NT). In comparison, individual or combinations of spading, trampling (one partial manual puddling to incorporate weeds) and weeding was termed minimum tillage (MT). Treatment involving the maximum tillage included 4 spading+2 trampling+2 weedings, and was termed the conventional tillage (CT). The latter is practiced widely by farmers' in the region. Nine tillage treatments were laid out in a Randomized Block Design (RBD) and replicated thrice in a fixed plot size of 5m×5m. Increasing tillage intensity (combinations of spading along with trampling and weeding) increased grain yields. Agronomic yields obtained with 2 spading+1 trampling+1 weeding (MT option) was statistically (p=0.05) similar to that under CT. In general, the weed biomass was more under NT and MT than CT, and also contributed 2–4, 0.8–2 and 0.78–1.9 times more N, P and K, respectively, towards nutrient recycling than that under CT. However, the amount of N, P and K recycled through rice straw was more under CT than MT and NT. Weed biomass played a major role as a nutrient source in MT systems and contributed towards yield stabilization and improvement in soil quality. The soil organic carbon (25.2g/kg), soil microbial biomass carbon (198.7μg/g dry soil) and dehydrogenase activity (25.84μg TPF/g dry soil) in NT were 11.5, 17 and 107%, respectively, more than those under CT. These parameters under MT systems were 6–13, 2–15 and 35–88%, respectively, more compared to those under CT. The bulk density (ρb) under CT (1.18Mg/m3) was significantly higher than those observed under MT systems of only one spading or one trampling (1.15Mg/m3). The net return was the highest with MT system comprising of 2 spading+1 trampling+2 weeding ($367.5/ha), and that was 25.5% higher than that with CT. The net return per dollar (NRP) invested decreased with increasing tillage intensity. In-situ rice residue retention along with weed biomass recycling (MT) for 4-years improved soil quality, reduced cost of production and stabilized productivity in a low-input marginal (marginal soil and small scale farmers) hill agriculture.

Effects of various tillage systems on soil CO2-C fluxes and on bacteria and fungi populations in Zea mays

The objective of this study is to determine the effects of strip tillage and full-width tillage treatments on soil carbon (IV) oxide-carbon (CO2-C) fluxes, bacterial and fungal populations in growing period of Zea mays. A row-crop rotary hoe with C type blades was used to create three strip widths by changing the connection of blades of the rotary hoe on the flanges. Strip widths were 22.5 (T30), 30 (T40) and 37.5 cm (T50). The full-width tillage practice (moldboard plow + disc harrow + leveler) gave 100% surface soil disturbance (T100) and was included in the experiment to make comparisons with the strip tillage system. During the growth of theZea mays, periodic measurements of CO2-C fluxes, bacterial and fungal populations were made. Statistically significant differences in CO2-C fluxes, microbial populations and soil bulk density were observed between the different tillage systems. Highest CO2-C fluxes and bacteria populations were observed with the full-width T100 treatment and the lowest values were observed in the T30 treatment during flowering and harvesting periods. Increasing tillage intensity increased soil CO2-C fluxes and bacteria population, but decreased fungi population and soil bulk density. Key words: Carbon IV oxide-carbon flux, strip tillage, strip width.

Effects of strip and full-width tillage on soil carbon IV oxide-carbon (CO2-C) fluxes and on bacterial and fungal populations in sunflower

In strip tillage system, planting lines are cultivated while the inter-row spaces are left undisturbed. The objective of this study is to determine the effects of strip tillage and full-width tillage treatments on soil carbon IV oxide-carbon (CO 2 -C) fluxes, bacterial and fungal populations in growing period of sunflower ( Helianthus annus ). A row-crop rotary hoe with C type blades was used to create three strip widths by changing the connection of blades of the rotary hoe on the flanges. Strip widths were 22.5 (T30), 30.0 (T40) and 37.5 cm (T50). The full-width tillage practice (moldboard plow + disc harrow + leveler) gave 100% surface soil disturbance (T100) and was included in the experiment to make comparisons with the strip tillage system. A randomized complete block design with three replications was used. During the growth of the sunflower, periodic measurements of CO 2 -C fluxes and bacterial and fungal populations were made. Significant (p < 0.01) differences in CO 2 -C fluxes, microbial populations, soil bulk density and total porosity were observed between the different tillage systems. Highest CO 2 -C fluxes, bacteria populations and total porosity were observed in the full-width T100 application and the lowest values were observed in the T30 treatment during flowering and harvesting periods. Increasing tillage intensity increased soil CO 2 -C fluxes and bacteria population, but decreased fungi population and soil bulk density. Key words : Carbon IV oxide-carbon flux, soil bacteria and fungi, strip tillage, full-width tillage, sunflower.

Carbon and Nitrogen Fractions in Dryland Soil Aggregates Affected by Long‐term Tillage and Cropping Sequence

Tillage and cropping sequence may influence C and N sequestration, microbial activities, and N mineralization in dryland soil aggregates. We evaluated the 21‐yr effect of tillage and cropping sequence combinations on C and N fractions in aggregates of a Dooley sandy loam (fine‐loamy, mixed, superactive, frigid Typic Argiustolls) at the 0‐ to 20‐cm depth in eastern Montana. Tillage and cropping sequences were no‐tilled continuous spring wheat (NTCW) (Triticum aestivum L.), spring‐tilled continuous spring wheat (STCW), fall‐ and spring‐tilled continuous spring wheat (FSTCW), fall‐ and spring‐tilled spring wheat‐barley (Hordeum vulgare L.) (1984–1999) followed by spring wheat‐pea (Pisum sativum L.)(2000–2004)(FSTW‐B/P), and spring‐tilled spring wheat‐fallow (STW‐F). Carbon and N fractions were soil organic C (SOC), total N (STN), particulate organic C and N (POC and PON), microbial biomass C and N (MBC and MBN), potential C and N mineralization (PCM and PNM), NH4–N, and NO3–N. Aggregate proportion was greater in NTCW than in FSTCW in the 4.75‐ to 2.00‐mm aggregate‐size class at 0 to 5 cm but was greater in STW‐F than in STCW in the 2.00‐ to 0.25‐mm size class at 5 to 20 cm. After 21 yr, STW‐F reduced SOC, STN, POC, and PON concentrations in aggregates by 34 to 42% at 0‐ to 5‐cm and by 20 to 32% at 5‐ to 20‐cm compared with NTCW and STCW. The PCM and MBC were greater in NTCW and STCW than in STW‐F in the &lt;2.00‐mm size class at 0 to 5 cm but MBN varied with treatments, aggregate‐size classes, and soil depths. Compared with other treatments, NH4–N concentration was lower in STW‐F in the 4.75‐ to 0.25‐mm size class but PNM and NO3–N were greater in FSTW‐B/P in the &lt;2.00‐mm size class. Long‐term reduced tillage with continuous spring wheat increased soil aggregation, C and N sequestration, and microbial biomass and activities in all aggregates but increased tillage intensity with spring wheat‐barley/pea rotation increased N mineralization and availability in small aggregates compared with the conventional STW‐F.

RZWQM simulated effects of crop rotation, tillage, and controlled drainage on crop yield and nitrate-N loss in drain flow

Accurate simulation of agricultural management effects on N loss in tile drainage is vitally important for understanding hypoxia in the Gulf of Mexico. An experimental study was initiated in 1978 at Nashua, Iowa of the USA to study long-term effects of tillage, crop rotation, and N management practices on subsurface drainage flow and associated N losses. The Root Zone Water Quality Model (RZWQM) was applied to evaluate various management effects in several previous studies. In this study, the simulation results were further analyzed for management effects (tillage, crop rotation, and controlled drainage) on crop production and N loss in drain flow. RZWQM simulated the observed increase in N concentration in drain flow with increasing tillage intensity from NT (no-till) to RT (ridge till) to CP (chisel plow) and to MP (moldboard plow). It also adequately simulated tillage effects on yearly drain flow and yearly N loss in drain flow. However, the model failed to simulate lower corn and soybean yields under NT than under MP, CP, and RT. On the other hand, RZWQM adequately simulated lower yearly drain flow and lower flow-weighted N concentration in drain flow under CS (corn–soybean) and SC (soybean–corn) than under CC (continuous corn). The model adequately simulated higher corn yield under CS and SC than under CC. Applying the newly suggested N management practice for the Midwest of controlled drainage, the model simulated a 30% reduction in drain flow and a 29% decrease in N losses in drain flow under controlled drainage (CD) compared to free drainage (FD). With most of the simulations in reasonably close agreement with observations, we concluded that RZWQM is a promising tool for quantifying the relative effects of tillage, crop rotation, and controlled drainage on N loss in drainage flow. Further improvements on simulated management effects on crop yield and N mineralization are needed, however.