The economic viability of using summer-seeded legume cover crops (crimson clover, red clover, hairy vetch) as a primary nitrogen (N) source for an organic corn (Zea mays L.)-soybean (Glycine max (L.) Merr.)-winter wheat (Triticum aestivum L.) rotation was determined on a sandy loam soil in southwestern Ontario, Canada, by comparing gross profit for organic production (organic sources of N and phosphorus, no herbicides) to conventional production (no cover crops, synthetic fertilizers and herbicides added). Profits were determined for the initial three-year transition period from conventional to organic production (2015-2017), and for five years of certified organic production (2018-2022). During the transition period when conventional crop prices applied to both production systems, organic production profits (CAD $1148-1869 ha-1 per rotation) were lower than conventional profits (CAD $2126 ha-1 per rotation). During the certified organic period when price premiums were applied, organic soybean and corn profits (CAD $1995-2274 ha-1 and $2819-3195 ha-1 per year, respectively) were significantly greater than conventional soybean and corn profits (CAD $536 ha-1 and $1926 per ha-1, respectively). Winter wheat profits were slightly higher for organic production (CAD $426 to $825 ha-1 per year) than for conventional production (CAD $371 ha-1 per year). During the certified organic production period, profits from the three year rotations were CAD $5533-6153 ha-1 for organic production, and CAD $2860 ha-1 for conventional production. It was concluded that an organic rotation of corn-soybean-winter wheat/legume cover crop can be economically viable and more profitable than conventional production on sandy loam soil in southwestern Ontario.

Context: Canada has targeted a 30% reduction in N2O emissions from fertilizer by 2030 in its commitments to reduce greenhouse gas emissions. To help achieve these commitments, a 'Pipes & Valves' conceptual visualization of the DNDC model was combined with the DeNitrification-DeComposition (DNDC) model to evaluate a suite of nutrient management and conservation practices. Objectives: The objectives were to meet the 30% reduction targets in N2O emissions as well as other reactive-N species (N2O, NI-13 and NO3- leaching) to provide a systems approach while increasing corn yields. This was accomplished by: 1) developing a 'Pipes & Valves' conceptual visualization model; 2) evaluating a full system DNDC model with 3-years of NI-13 volatilization, N2O emission, inorganic N, crop yield and N uptake data; 3) applying the 'Pipes & Valves' DNDC system to identify N-management strategies that mitigate N-loss and improve yields. Methods: The DNDC model compared simulated and measured N-loss and crop performance over 3 years for Nmanagement practices including pre-plant versus side-dress UAN injection with either no inhibitors, a urease inhibitor or a dual urease and nitrification inhibitor. A Pipe and Valves conceptual visualization model was developed and used with the DNDC model to simulate 14 management scenarios based on moldboard plow tillage versus conservation tillage, and fertilizer management including fertilizer type (urea vs. urea ammonium nitrate, UAN), inhibitor (none, nitrification inhibitor, urease inhibitor or both), placement (broadcast vs. injection), timing (at planting vs. split application), and N rate (recommended vs. 15% reduction). Results: The DNDC model was evaluated using field data and had excellent performance for yields, cumulative N2O emissions and soil temperature while soil water predictions were fair using standard performance metrics. Multiple nutrient management and/or conservation tillage practices decreased NI-13 losses by 36-96% compared to broadcast urea. A pre-plant broadcast urea and nitrification inhibitor treatment and a conservation tillage treatment with side-dressed injected UAN with a dual urease and nitrification inhibitor reduced N2O losses by 37-40%. Conclusions: Although several management practices reduced one N-loss pathway by >= 30%, only side-dress injected UAN with urease plus nitrification inhibitors under conservation tillage achieved multiple reductions of 40%, 93% and 62% in N2O, NI-13 and reactive-N, respectively while increasing corn grain yields by 7%. Significance: Combining the 'Pipes & Valves' conceptual visualization model with DNDC modelling was effective for determining how 4R nutrient management and conservation tillage can be stacked and used worldwide to meet N-loss reduction targets without compromising yields.

Ammonia loss following nitrogen fertilization can degrade air quality and impact human health, whereas nitrous oxide (N2O) can contribute to global warming and climate change. Mitigation practices that target only one N-loss pathway can lead to pollution swamping; hence, practices targeting both N-losses are required. A 3-yearfield study examined fertilizer N-placement (broadcast urea, single-slot injection of urea ammonium nitrate [UAN], double-slot UAN injection) and N-metabolization inhibitors (with/without urease and nitrification inhibitors) impacts on NH3and N2O losses and corn yields. Ammonia volatilization was reduced (p<0.05) by 26% with single-slot UAN injection (10.6 kg N ha(-1)) and by 63% with double-slot UAN injection (5.32 kg N ha(-1)) compared to broadcast urea (14.3 kg N ha(-1)). Dual urease and nitrification inhibitors reduced NH3volatilization (0.84-3.86 kg N ha(-1)) by 57%-92% compared to no inhibitors (5.32-14.3 kg N ha(-1)). When no inhibitors were applied, N2O emissions from slot injection (6.43-7.62 kg N ha(-1)) were 2.6-3.1 times greater than from broadcast urea (2.43 kg N ha(-1)). Dual inhibitors reduced N2Oemis-sions by 43% from 6.43 to 3.66 kg N ha(-1)with double-slot injection. Double-slot UAN injection increased corn grain yields (9.73 t ha(-1)) by 12%-13% compared to single-slot UAN injection (8.71 t ha(-1)) and broadcast urea (8.6 t ha(-1)). Double-slot UAN injection effectively decreased NH(3 )losses and increased corn grain yields, but dual N inhibitors were required to also reduce N2O. Hence, combined productivity and environmental benefits were accrued only when fertilizer containing urease and nitrification inhibitors was combined with double-slot injection

With recent increases in energy costs, information on energy inputs is becoming a more important aspect in management decisions on selection of crop production systems. The effects of long-term (45-55 years) monocropping, rotation cropping, and fertilization on tillage energy (implement draft and tractor fuel consumption) were determined for a Brookston clay-loam soil in southwestern Ontario, Canada. Treatments included fertilized and unfertilized monocrop (continuous) corn (Zea mays L.), and a four year fertilized and unfertilized corn - oat (Avena sativa L.) - alfalfa (Medicago sativa L.) - alfalfa rotation with all phases of the rotation present in each year. The corn and second year alfalfa plots were moldboard plowed each fall after crop harvest, and then spring-tilled (disc, harrow) prior to planting; oat and first year alfalfa plots were not fall plowed or spring-tilled. Moldboard plow draft and tractor fuel consumption were measured annually from 2004 to 2014 using an instrumented tractor and the same plow and settings. Monocrop unfertilized corn consistently exhibited the greatest plow draft and tractor fuel consumption. Draft averaged over ten years was 13.0% higher for unfertilized than fertilized rotation corn, and 15.5% higher for fertilized than unfertilized second year alfalfa; fuel consumption was 10.4% higher for unfertilized than fertilized rotation corn and 5.1% higher for fertilized than unfertilized second year alfalfa. These differences were attributed to treatment-induced changes in soil strength. Both plow draft and fuel consumption were lower in rotation corn relative to monocrop corn, while plow draft was greater in fertilized alfalfa relative to unfertilized alfalfa due to greater root growth. This study demonstrated that long-term cropping systems can have substantial impacts on the energy required for tilling a clay loam soil.

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This study presents results from the first 5 years of an organic cropping trial in Ontario, Canada, where legume cover crops were the primary nitrogen source in a soybean-winter wheat/cover crop-corn rotation. Treatments included cover crop termination using moldboard plow (MP) or chisel plow (CP), a no-cover crop control under conventional production (CK-C), and four cover crops including summer-seeded crimson clover (CC, Trifolium incarnatum L.), summer-seeded hairy vetch (HV, Vicia villosa L. Roth), summer-seeded red clover (RC ss , Trifolium pratense L.), and frost-seeded red clover (RC fs ). Summer-seeding occurred after wheat harvest (July–August), and frost-seeding occurred in early spring (March–April). At cover crop termination, average aboveground cover crop biomass ranged from 5.9 to 8.1 Mg ha −1 , while accumulated biomass nitrogen ranged from 155 to 193 kg ha −1 . Corn grain yields were 11.6 Mg ha −1 for MP and 10.2 Mg ha −1 for CP tillage-termination method; and 13.3 Mg ha −1 for CK-C, 10.9 Mg ha −1 for RC fs , 10.6 Mg ha −1 for HV, 10.2 Mg ha −1 for CC, and 9.5 Mg ha −1 for RC ss . Organic winter wheat yields were nitrogen-limited, averaging 27% lower than CK-C. Winter wheat yields were 10–15% lower in the RC fs than in other summer-seeded cover crop treatments. Soybean yields were largely unaffected by the treatments. It was concluded that summer-seeded legume cover crops are an effective primary nitrogen source for corn, but not as effective for the winter wheat phase of the soybean-winter wheat-corn rotation.

Canadian agriculture produces a diversified supply of food, feed crop and livestock types supporting Canada’s economy. This production uses both fertilizer-N application and biological N-fixation sources, which have increased over time and can be vulnerable to environmental losses in the form of ammonia (NH3) & nitrous oxide (N2O) emissions along with nitrate (NO3-) leaching. This paper reports the spatial and temporal trends in N input, N output and N losses in Canadian farmland with a specific focus on the residual soil N, N2O and NH3 emissions and NO3- leaching loss at the provincial scales from 1981 to 2016. A Canadian Agricultural Nitrogen Budget for Reactive N (CANBNr) model was developed to estimate the soil N balance at 3487 soil landscape of Canada polygons. The CANBNr model estimated soil N export via crop N removal, as well as emissions of N2O and NH3 for different input sources. The NO3- leaching is estimated based on the quantity of residual soil N (RSN) and water drainage derived using the DNDC model. From 1981 to 2016, the N inputs from fertilizer and biological N fixation increased at a greater rate than N exported in harvested crops for all provinces of Canada, which resulted in increased RSN and N losses. In 2016, we concluded that the Prairie provinces (Alberta, Saskatchewan and Manitoba) had lower N losses (N2O, NH3 and NO3-) per hectare of farmland (11.7 kg N ha-1) compared with 43.2 and 76.5 kg N ha-1 in Central Canada (Ontario and Quebec) & Atlantic provinces. However, the Prairie provinces represented 84.3% of the total Canadian farmland (74.3% of total Canadian N input), while central Canada represented only 12.9% of Canadian farmland (21.7% of total Canadian N input). The total N2O loss was 39.5 and 21.0 Gg N, whereas total NH3 loss was 202.3 and 110.2 Gg N in the Prairie and central Canada provinces, respectively, as influenced by both emissions and land area. In the non-growing season, NO3- leaching losses were 97.3 and 87.5 Gg N in the Prairies and central Canada provinces compared with 66.2 and 36.7 Gg N in the growing season as impacted by drainage volumes, soil type and the RSN. Over 36 years, the total fertilizer N increased the most in the Prairies and cased significant increase in RSN and N losses that will require future interventions.

Summer-seeding legume cover crops can reduce erosion, mitigate nitrate leaching losses during the non-growing season, and provide bio-accumulated nitrogen (N) to the following crop. Very little information is available, however, on the most effective methods for terminating summer-seeded cover crops, or on the amount of N they can provide to subsequent crops. We therefore evaluated the impacts of selected legume cover crops and cover crop termination-tillage methods on corn (Zea mays L.) N credit and grain yield in a soybean (Glycine max Merr.) - winter wheat (Triticum aestivum L.)/cover crop - corn rotation over 3 consecutive years on a clay loam soil in southwestern Ontario. The cover crops were summer-seeded after wheat harvest, and included hairy vetch (Vicia villosa L. Roth), red clover (Trifolium pratense L.), white clover plus crimson clover mix (incarnatum and Trifolium alba L.), and a no cover crop control (CK). The cover crops were nested within termination-tillage method, including moldboard plow-down in fall, and herbicide spray-down in spring under strip-tillage or no-tillage then corn planting. Nitrogen fertilizer to corn was applied via side-dress at 200 kg N ha-1 to the CKs, and at 100 kg N ha-1 to the cover crops. Averaged over 3 years, above-ground biomass N level followed the pattern: hairy vetch > white clover plus crimson clover mix > red clover for fall plow-down termination. There were no significant differences in cover crop biomass N levels for spring termination. Corn response to cover crop was significantly affected by termination-tillage method and cover crop species, with poor corn stands after no-tillage, red clover and white plus crimson clover. Fall plow-down termination provided a range in N credit of 80-85 kg N ha-1, which was significantly greater than the N credit under herbicide spray-down in spring. Under spring strip-tillage and no-tillage, hairy vetch produced significantly greater corn grain yields than red clover and white plus crimson clover mix.

&lt;p&gt;Conservation tillage has become the core technology to&amp;#160;conquer&amp;#160;the degradation of black soil, the &amp;#8216;giant panda in arable land&amp;#8217;. Since soil is a home to a variety of organisms, it is very important to regard soil as a living system to evaluate the impact of conservation tillage on the health of black soil. Therefore, based on the long-term conservation tillage trial established by the Key Laboratory of Mollisols Agroecology of the Chinese Academy of Sciences,&amp;#160;the responses of soil biodiversity&amp;#160;and its function to conservation tillage were comprehensively elucidated in this study. Compared with conventional tillage, conservation tillage&amp;#160;strongly improved the&amp;#160;species richness&amp;#160;(1-8%), density&amp;#160;(25-57%), and biomass (30-50%) of the entire soil assemblages, including microorganisms, nematodes, collembolans, mites and earthworms, as well as the connectance&amp;#160;of soil food web&amp;#160;(14-32%). Furthermore, conservation tillage promotes the performance of soil biotic function in soil structure formation, soil carbon sequestration and nitrogen efficient utilization&amp;#160;and crop yield stability. These&amp;#160;results suggest&amp;#160;that conservation tillage can effectively utilize the functional potential of soil organisms, which is of great significance to supporting the healthy&amp;#160;and sustainable development of&amp;#160;agriculture in the black soil region&amp;#160;of northeast China.&lt;/p&gt;

Tile drainage and surface runoff are major pathways for pollution of water resources by agricultural nutrients and chemicals. Little is known, however, of the pathways and amounts of carbon entry into water resources from agricultural land. This paper evaluates dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) losses in tile drainage and surface runoff from a Brookston clay loam after more than a half century of monoculture maize ( Zea mays L.), continuous bluegrass sod ( Poa Pratensis L.), and maize-oat ( Avena sativa L.)–alfalfa ( Medicago sativa L.)–alfalfa rotation. Water loss in tile drainage and surface runoff accounted for 27%, 32%, and 18% of annual precipitation (876 mm) for rotation, monoculture maize, and continuous sod, respectively. Tile drainage comprised 66%–89% of water loss from rotation and continuous sod, but only 15% from monoculture maize, with the remaining 85% of water loss from monoculture maize due to surface runoff. On an annualized basis, the measured dissolved C loss was 79 and 83 kg C ha–1 yr–1) from rotation and continuous sod, respectively, while 49 kg C ha–1 yr–1 was lost from monoculture maize. As up to 9% off-gassing loss of CO2 from water samples was measured, total dissolved carbon losses in tile drainage and runoff water were likely greater. For Brookston clay loam soil, leaching into tile drains was the dominant mechanism for dissolved carbon loss from long-term continuous sod and crop rotation, while surface runoff was the dominant mechanism for dissolved carbon loss from long-term monoculture maize.

东北黑土区承担着国家粮食安全“稳压器”的重要责任。然而，由于长期超负荷开发利用导致黑土日益退化，黑土资源的永续利用受到严重制约。理论与实践证明，保护性耕作是保护黑土地、推动黑土耕地质量和耕作效益绿色增长的发展模式。综述了保护性耕作的基本内涵及其在东北黑土区的发展现状与技术概况，从保护性耕作在土壤保持、保墒效益、结构改善、固碳培肥和土壤生物多样性增加、节本增效等方面系统评估了东北黑土区实施保护性耕作后的生态与经济效益，提出黑土区实施保护性耕作存在的问题与未来发展方向，以促进黑土地保护与利用协调发展、推动保护性耕作高质量跨越式发展。

Crop residue input plays a central role in regulating soil organic carbon (SOC) storage. Ten long-term field experiments were used to ascertain the changes in SOC in response to differing rates of crop residues. The amount of C input from crop residues varied significantly between and within sites due to soil-environmental conditions, management and cropping systems. Initial SOC stocks ranged from 45 to 165 t C ha- 1 in the 0-30 cm soil depth. Four soil C models, Campbell, ICBM, IPCC Tier 2 steady state (IPCC) and RothC with their default parameterization were used to simulate the SOC. Two model ensemble approaches, a mean (Ens_Avg) and a weighted mean (Ens_Weighted) of the model predictions were also included in the evaluation. Individual model performance was evaluated on the model's ability to capture the SOC stock and change in SOC (& UDelta;SOC). Across sites, the Ens_Weighted approach had the lowest overall RMSE for total SOC (5.2 t C ha(-1)) and delta SOC (5.5 t C ha(-1)) followed by Ens_Avg. Ensemble models which had the lowest bias (PE) and model prediction error (d-index). Within individual models, Campbell and IPCC performed better than other models with the lowest RMSE of 5.8 and 6.3 (t C ha(-1)) for SOC stocks. In general, ICBM and Campbell underestimated, and RothC overestimated the & UDelta;SOC per unit of C input to the soil with the IPCC model close to the average observations. The use of weighted and average ensemble approaches reduced estimation errors. Nonetheless, our results indicate that regional calibration and validation is warranted for the effective quantification of regional SOC dynamics.

Estimating soil nitrogen (N) mineralization is critical to balance fertilizer N requirements and their environmental impacts. In this study, net N mineralization was examined in soils under different crop rotations with each phase of the rotation present every year with biologically based incubations in 2011 and 2015. Net N mineralization was significantly different among treatments when the current crop was soybean, and the effect was dependent upon the previous crop and the cropping sequence. In particular, net increases in inorganic N were greater when the previous crop was winter wheat with or without red clover than if it were corn, and greater for the first year of soybean compared with the second year for rotations with two consecutive years of soybean in the 2011 incubation. However, cropping history did not influence net soil N mineralization when the current crop was corn, winter wheat, or winter wheat with red clover. In 2015, the presence of red clover in the rotation increased net N mineralization in all phases of the rotation. These results suggest both current and previous crops should be considered when estimating the N supplying capacity (net mineralization) of the soil. Net mineralizable N was found to be significantly correlated with total amino sugars (P < 0.001), glucosamine (P < 0.001), and galactosamine (P = 0.003), which suggests that amino sugars could be used as an indicator of the N supplying capacity of soil.

It is well known that mechanochemically activated phosphate rock (MAPR) could improve extractable phosphorus (P) (extracted in 2% citric acid) greatly in an ecological way. To evaluate the agronomic effectiveness of MAPR, we conducted a field experiment using spring maize in Luvisol (pH 6.47) soil in Northeast China for three consecutive years. Treatments consist of variation of P levels for substitution of triple superphosphate (TSP) (100% TSP, 10% MAPR, 20% MAPR, 50% MAPR, 100% MAPR). Compared with 100% TSP, all the combined applications of MAPR and TSP were as effective on straw yield. Treatments of 10% MAPR and 20% MAPR had similar effect on grain yield and P uptake, while 50% MAPR and 100% MAPR were significantly lower. For P partial nutrient productivity and apparent P recovery with the treatment of 20% MAPR had equal effectivity, likewise. For soil P-Olsen, treatment of 10% MAPR was equally operative, while 20% MAPR had the similar performance only in the last year (i.e. 2016). It is concluded that 10-20% of TSP can be effectively replaced by MAPR without affecting spring maize yield in soil with neutral pH.

保护性耕作是攻克黑土地保护和利用的核心技术之一.研究立足中国科学院黑土区农业生态重点试验室保护性耕作长期定位试验基地,系统梳理总结了农田黑土土壤生物多样性对保护性耕作的响应特征.与传统耕作相比,保护性耕作显著增加各生物类群(微生物、线虫、跳虫、螨类及蚯蚓)的物种丰富度(1％～8％)、数量(25％～57％)和生物量(30％～50％),提高食物网网状结构的复杂性及各营养级间的连通性(14％～32％),促进土壤生物在固土蓄水、土壤碳固存、氮素高效利用以及稳定作物产量四方面生态功能的可持续性发挥.研究结果表明,实施保护性耕作可有效利用土壤生物的功能潜力,实现东北黑土区农田生态系统的健康发展、服务国家粮食安全产业带建设和现代农业发展.

The Weibull function is applied extensively in the life sciences and engineering but underused in agriculture. The function was consequently adapted to include parameters and metrics that increase its utility for characterizing agricultural processes. The parameters included initial and final dependent variables (Y0 and YF, respectively), initial independent variable (x0), a scale constant (k), and a shape constant (c). The primary metrics included mode, integral average, domain, skewness, and kurtosis. Nested within the Weibull function are the Mitscherlich and Rayleigh functions where c is fixed at 1 and 2, respectively. At least one of the three models provided an excellent fit to six example agricultural datasets, as evidenced by large adjusted coefficient of determination (RA2 ≥ 0.9266), small normalized mean bias error (MBEN ≤ 1.49%), and small normalized standard error of regression (SERN ≤ 8.08%). The Mitscherlich function provided the most probable (PX) representation of corn (Zea mays L.) yield (PM = 87.2%); Rayleigh was most probable for soil organic carbon depth profile (PR = 96.4%); and Weibull was most probable for corn seedling emergence (PW = 100%), nitrous oxide emissions (PW = 100%), nitrogen mineralization (PW = 58.4%), and soil water desorption (PW = 100%). The Weibull fit to the desorption data was also equivalent to those of the well-established van Genuchten and Groenevelt–Grant desorption models. It was concluded that the adapted Weibull function has good potential for widespread and informative application to agricultural data and processes.

Many studies haveexamined soil-borne nitrous oxide (N2O) emissions from crops, but little effort has gone into determining the N2O emissions from each phase of a crop rotation. A 4-yr study on a long-term field experiment compared growing season N2O emissions from continuous corn (CC; Zea mays L.) and a 4-yr crop rotation involving corn (RC), oat (Avena Sativa L.) underseeded to alfalfa (Medicago sativa L.) (RO), and 2 yr of alfalfa (RA1, RA2). Molecular microbial biomass (DNA yield), as well as N-cycling functioning genes (mineralization, nitrification, and denitrification), were also evaluated. Although 4-yr cumulative N2O emissions from RC (9.25 kg N ha(-1)) were significantly greater than from CC (7.94 kg N ha(-1)), cumulative emissions from the entire rotation were 54% lower (3.69 kg N ha(-1)) than CC because of low emissions from RO (3.1 kg N ha(-1)), RA1, and RA2 (1.11-1.27 kg N ha(-1)). Years that had substantial early-season precipitation combined with high soil inorganic N from alfalfa plow-down contributed to elevated N2O emissions from RC. Improved soil conditions and fertility under rotation increased RC grain yields by 35% (9.45 Mg ha(-1)) compared with CC (7.01 Mg ha(-1)). Microbial biomass was 73% greater in RC compared with CC. Nitrogen mineralization genes were 19% greater in RC but they were not correlated to N2O emissions, whereas bacterial nitrifiers were positively correlated. Denitrification was likely responsible for N2O emissions under CC, while nitrifier-denitrification appeared to be the primary pathway under RC. The N2O emissions and microbial processes from all phases of a rotation should be considered for environmental modeling and policy decisions.

Soybean (Glycine max L.) is known to contribute to soil N reserves when grown in rotation with other high-value crops such as corn (Zea mays L.) and winter wheat (Triticum aestivum L.). However, continuous soybean and "short" soybean rotations (e.g., corn-soybean, wheat-soybean) may cause declining soybean yields and degrading soil health over time. In this long-term field study, we determined crop rotation effects on soybean yield and soil health indicators for a cool, humid, clay loam soil in southwestern Ontario. The study used nine soybean rotations, which included continuous soybean (S), corn-soybean (C-S), corn-soybean-soybean (C-S-S), and six rotations where winter wheat (WW) was grown with red clover (Trifolium pratense L.) (+RC) and without underseeded red clover (i.e., winter wheat-soybean [WW-S, WW+RC-S], corn-soybean-winter wheat [C-S-WW, C-S-WW+RC], and winter wheat-soybean-soybean [WW-S-S, WW+RC-S-S]). Ten soil health indicators during the first and second soybean phase of each rotation were measured in 2018, whereas soybean yield was measured from 2002 to 2018. Soybean yields in 2- and 3-yr rotations were 39-44% and 48-52% greater, respectively, relative to continuous soybean excluding the rotations with 2 of 3 yr of soybean (C-S-S, WW-S-S, WW+RC-S-S), which were only 22-35% greater than continuous soybean. Partial least squares regression indicated that inorganic N, particulate organic matter N, particulate organic matter C, potentially mineralizable N, total C, soil respiration rate, and water extractable organic soil C were the most important soil health indicators, explaining 34% of the total variation in soybean yields. It was concluded that soybean grown in 3-yr rotations with corn and winter wheat produced the largest soybean yields and the greatest positive impacts on soil health indicators likely owing to cereal crops enhancing C inputs into soil.

Corn (Zea mays L.) stover is an increasingly important feedstock for biofuel and bioproduct production; however, excessive harvest of corn stover from agricultural fields may affect corn seedling emergence and subsequent plant population which may reduce corn growth and yield. Field experiments were conducted over four consecutive growing seasons in southwestern Ontario to determine under continuous corn cropping system the effects of no-tillage (NT), conventional tillage (CT), and five rates of stover harvest (0, 25, 50, 75, and 100 wt. %) on corn seedling emergence in a Harrow sandy loam and in a Brookston clay loam. Time to achieve 50% seedling emergence (t(0.5)), emergence rate constant (k(G)), and final seedling population (M-G) were adequately simulated using the Gompertz function. Irrespective of stover removal rate and soil type, t(0.5) was 2 d longer, and k(G) was 32% lower, under NT compared to CT. In Harrow sandy loam, stover removal from NT reduced t(0.5) in 1 out of 4 yr. The 100% removal reduced t(0.5) relative to 0, 25, 50, and 75% removal by 1.1-2.2 d in 2015. Averaged across both tillages and all removal rates, k(G) was greater in Harrow sandy loam than in Brookston clay loam. Stover removal rates had no effect on M-G but averaged over all removal rates and soil types, M-G was 9% lower for NT compared to CT in 2016. No-tillage practice under corn production can impede seedlings emergence early in the growing season and stover removal from the field can help mitigate against this effect.