No-till Corn Research Articles

Subsurface banding of poultry litter influence on runoff nutrient losses in a no-tillage maize cropping system

Poultry litter (PL) is often used as an alternative nutrient source to inorganic fertilization for crop production in the southeastern US. Historically, PL has been broadcast applied on the soil surface, leaving the nutrients susceptible to runoff. Developments made in recent years allow for placing PL in narrow bands below the soil surface with minimal disturbance. This technological advancement could reduce the transport of P in surface water runoff from fields managed under conservation agricultural systems. Thus, a study was conducted to evaluate the influence of banding PL into a no-tillage corn (Zea Mays L.) field on P loss. Treatments consisted of surface banded PL, subsurface banded PL (3–5 cm below the surface), broadcasted PL, broadcasted commercial fertilizer (CF), and a nonfertilized control. The PL treatments were applied based on an N rate of 168 kg total N ha−1. For the CF, inorganic N was applied at a rate of 168 kg total N ha-1 and P at a rate of 45 kg P ha−1. Runoff events (40 min) were created using rainfall simulations (rainfall was applied at 89 mm hr−1). The greatest losses of dissolved reactive P and inorganic N occurred with the surface broadcast treatments. Subsurface band applying PL reduced P concentration losses and loading in surface water runoff to levels of the control. No differences were observed in runoff volume between treatments. Thus, total P losses mimic those observed for dissolved reactive P concentration in surface water runoff and loads. Approximately 60–80% of the total P concentration was dissolved reactive P regardless of application method. Subsurface band application reduced total P concentration by 95% when compared to surface broadcasted litter. These results show that subsurface band-applied PL can greatly reduce the impact of P loss to the environment when compared to conventional surface-applied PL and CF practices.

Ammonia Volatilization Loss and Corn Nitrogen Nutrition and Productivity with Efficiency Enhanced UAN and Urea under No-tillage

New urease and nitrification inhibitors and polymer coatings were introduced in recent years, but their effects on N loss and plant N nutrition were scarcely examined in agronomic no-tillage production systems. A field experiment of urea treated with efficiency enhancers was conducted on no-tillage corn (Zea mays L.) in Tennessee, the USA during 2013–2015. A field experiment on urea and ammonium nitrate (UAN) treated with efficiency enhancers was carried out on no-tillage corn in Tennessee in 2014 and 2015. Urea treated with N-(n-butyl) thiophosphoric triamide (NBPT) at concentrations of 20% (NBPT1), 26.7% (NBPT2), or 30% (NBPT3) and polymer coated urea (PCU) were effective but maleic-itaconic copolymer treated urea was ineffective in reducing ammonia volatilization loss and improving N nutrition, grain yield, and N agronomic use efficiency of corn compared with untreated urea. Specifically, NBPT1, NBPT2, or NBPT3 treated urea and PCU reduced the total ammonia volatilization loss by 29.1–78.8%, 35.4–81.9%, 77.3–87.4%, and 59.1–83.3% during the 20 days after N applications, but increased grain yield by 15.6–31.4%, 12.9–34.8%, 18.7–19.9%, and 14.6–41.1%, respectively. The inhibitory effect of NBPT on ammonia volatilization did not improve with NBPT concentration increased from 20% to 30%. UAN treated with NBPT3 or a combination of urease and nitrification inhibitors resulted in 16.5–16.6% higher corn yield than untreated UAN only when they were surface applied. In conclusion, when urea-containing fertilizers are surface applied without any incorporation into the soil under no-tillage, their use efficiencies and performances on corn can be enhanced with an effective urease inhibitor in areas and years with noticeable urea N losses.

Soil Health and Soil Fertility Assessment by the Haney Soil Health Test in an Agricultural Soil in West Tennessee

ABSTRACTThe Haney Soil Health Test (HSHT) is a recent approach to quantify soil health by focusing mostly on soil biology. It uses a new extractant (H3A) for the extraction of plant available nutrients, a new method of soil respiration measurement (24-hr CO2 burst) using Solvita® gel system, and a new approach in determining bioavailable carbon (C) and nitrogen (N) namely water extractable organic C (WEOC) and water extractable organic N (WEON). A soil health score is calculated by combining Solvita® respiration, WEOC, and WEON data. The objective of this study was to test the feasibility of HSHT to detect the management-induced changes in soil nutrient levels and soil health in the production systems of west Tennessee. We tested soils collected from a cover crop field trial established in 2013 on a no-till corn (Zea mays L.) – soybean [Glycine max (L.) Merr.] rotation. Compared to Mehlich-1 and Mehlich-3, H3A extracted the lowest amount of soil extractable phosphorus, potassium, calcium and magnesium. Neither the soil health score nor its component parameters showed significant differences between cover crop treatments and the control. In addition, the Solvita® CO2 data did not provide a reliable estimation of potentially mineralizable N. Overall, the HSHT did not detect differences in soil health due to cover cropping in west Tennessee. We conclude that HSHT, though a promising concept due to its focus on linking soil biology with soil fertility and soil health, may need extensive field evaluation and refinement in contrasting soils and climates across the US.

Long-term effect of cover crop on rainwater balance components and use efficiency in the no-tilled and rainfed corn and soybean rotation system

Incorporating cover crops into row crop production systems can affect soil water dynamics and crop production. However, the effect of this practice has not been well investigated in the northeast Mississippi USA. We calibrated and validated the cropping system model (Root Zone Water Quality Model, RZWQM2) using 4-yr (2014–2017) field data in the humid Mississippi Blackland Prairie, and also used this model to simulate the long-term (1938–2017) effects of a winter wheat (Triticum aestivum L.) cover crop on hydrological variables, crop yield, and water use efficiency (WUE, grain yield per unit of evapotranspiration) in a rainfed and no-tilled corn (Zea mays L.) and soybean (Glycine max L.) cropping system. Compared to no cover crop scenarios, long-term simulation demonstrates that average annual percolation under the cover crop system was decreased by 36 mm. Average annual actual evapotranspiration were 36 mm higher under cover crop system than no cover crop system. Simulated annual runoff for cover crop scenario was not different from values simulated for no cover crop scenario. Predicted actual evaporation during cash crop growth periods under cover crop plots was 25% less than under no cover crop plots due to mulch cover when averaged over the whole modeling period. Compared with no cover crop scenarios, the estimated crop evapotranspiration under cover crop scenario was reduced by 6.6% (31 mm) during corn growth period and by 3.7% (19 mm) during soybean growth period. Yearly predicted crop yields for corn and soybean did not improve, respectively, in the cover crop-based cropping system. Compared to the plots with no cover crop, the simulation of WUE for corn and soybean were respectively improved by 6.4% (1.49 kg m−3 versus 1.40 kg m−3) and by 5.0% (0.63 kg m−3 versus 0.60 kg m−3) for the plots with cover crop, largely due to the decrease in surface evaporation without sacrificing crop growth. These results suggest that long-term use of wheat cover crop to summer crops rotation is a promising practice to decrease deep percolation and restrict surface evaporation, and also improved crops WUE in the corn and soybean rotation in subtropical agro-system.

Dedicated Bioenergy Crops and Water Erosion.

Information on the water quality impact of perennial warm-season grasses (WSGs) when grown in marginal lands as dedicated energy crops is limited. We studied how WSGs affected runoff, sediment, and nutrient losses and related near-surface soil properties to those of no-till corn ( L.) on an eroded soil in southwestern Iowa and a center pivot corner in east-central Nebraska. The experiment at the eroded soil was established in 2012, and treatments included 'Liberty' switchgrass ( L.) and no-till continuous corn. The experiment at the pivot corner was established in 2013 with 'Liberty' switchgrass, 'Shawnee' switchgrass, low-diversity grass mixture, and corn. We simulated rainfall at 63.5 ± 2.8 mm h for 1 h to portray 5-yr return periods and measured water erosion in spring 2017. Time to runoff start and runoff depth did not differ between WSGs and corn. On the eroded soil, sediment and nutrient losses did not differ between treatments. At the pivot corner, sediment (0.71 vs. 0.15 Mg ha) and PO-P (0.037 vs. 0.006 kg ha) losses were five times higher in corn than in WSGs. Near-surface soil properties did not differ on the eroded soil, but at the pivot corner, wet aggregate stability was four times higher and residue cover was 34% higher in WSGs than in corn. Water-stable aggregates were negatively correlated with NO-N and PO-P losses. Overall, WSGs can improve water quality in marginally productive croplands, but their effectiveness appears to be site specific.

Carbon debt of field-scale conservation reserve program grasslands converted to annual and perennial bioenergy crops

Over 5 million ha of US Conservation Reserve Program (CRP) grasslands have been converted to annual crops since 2000, driven mainly by demand for corn grain ethanol. Much of the soil carbon sequestered under CRP is lost upon conversion, creating a ‘carbon debt’ that is presumed to be repaid by future greenhouse gas (GHG) savings from ethanol’s substitution for petroleum. Model simulations, extrapolations, and national statistics rather than direct measurements have been used thus far to estimate the long-term global warming impact (GWI) of such conversions. Here we report measured GWIs for three 22-year-old CRP grassland fields and three conventionally tilled agricultural (AGR) fields (11–17 ha) converted to either annual no-till corn or perennial cellulosic (switchgrass or restored prairie) bioenergy crops. We assessed GWIs for each field over eight years using whole-system life cycle analysis (LCA) by measuring: (a) GHG fluxes via eddy covariance and static chamber methodologies, (b) farming operations and agronomic inputs, and (c) the fossil fuel offset by ethanol use. Payback times were much longer than those estimated by prior modeling efforts. After 8 years, cumulative GWIs of switchgrass, restored prairie, and corn at the CRP grasslands were, respectively, −2.6 ± 4.0, 6.9 ± 3.6 and 85.2 ± 5.1 Mg CO2-equivalent ha−1. The switchgrass system had repaid its carbon debt by year eight and the restored prairie will have likely repaid by year ten; however, the no-till corn system appears likely to require >300 years. The same bioenergy crops grown on former agricultural lands, with no sequestered carbon lost on conversion, repaid their carbon debts within two years. Results indicate that GWI estimates and carbon debt payback times due to conversion of CRP lands to annual bioenergy crops have been substantially underestimated by current models.

Effect of Tillage and Cultivar on Plant Population, Sudden Death Syndrome, and Yield of Soybean in Iowa

Conservation tillage has become a common practice of soybean farming in the Midwestern United States owing to the benefits of soil and moisture conservation. Field trials were established in a field with a history of sudden death syndrome (SDS; caused by Fusarium virguliforme) in Iowa in 2011 and evaluated for five consecutive years to determine the impact of tillage on SDS and yield. The experiment was laid out in a split-split-plot design with four replicates. The main plot factor was tillage (no-till both crops, no-till corn and chisel plow soybean, and disc corn and chisel plow soybean), and each main plot was divided into subplots of corn or soybeans (in a 2-year rotation). Each subplot was again divided into two subsubplots, in which two soybean cultivars, moderately susceptible (MS) and moderately resistant (MR) to SDS, were planted each year. Root rot and SDS disease index (FDX) differed among years, because some years were more favorable for the disease than the others. However, tillage did not affect any parameters, including yield, in any year (P > 0.05). Cultivar effect was significant for each parameter occasionally. When significant, the MR cultivar had lower root rot and FDX and greater yield than the MS cultivar. These data suggest planting resistant cultivars can be an effective management tactic, but tillage does not help for SDS management.

Impacts of Early- and Late-Terminated Cover Crops on Gas Fluxes.

Cover crops (CCs) could alter soil processes, but the effects of early versus late termination of CCs on gas fluxes are not well known. We evaluated temporal changes in fluxes of CO, NO, and CH and related soil properties in no-till corn ( L.) with and without winter rye ( L.) CCs that were terminated early (30 d before planting) or late (at planting) in a rainfed silty clay loam and an irrigated silt loam in Nebraska from April 2016 to June 2017. Gas fluxes, soil temperature, and soil water content were measured biweekly to monthly, and wet aggregate stability and particulate organic matter concentrations were measured seasonally. We also compared our results with a global literature review. Late-terminated CCs did not affect CH fluxes but increased daily CO fluxes by 59% compared with no CC at both sites and NO fluxes by 92% at the rainfed site only. Early termination did not affect gas fluxes. Termination date did not affect cumulative fluxes and had minimal effects on soil properties. The literature review supports our study results, which indicate that CC effects on (i) CO fluxes are driven by plant respiration during the CC growing period, and (ii) NO and CH fluxes are minimal under grass CCs. Overall, under no-till, CC termination date has small effects on NO and CH fluxes, but late CC termination can increase CO fluxes in spring due to greater biomass yield compared with early termination.

Effects of clothianidin-treated seed on the arthropod community in a mid-Atlantic no-till corn agroecosystem.

Nearly all corn seed in the US is coated with neonicotinoid insecticides to protect against soil and foliar arthropod pests. Exposure in the soil and the systemic activity in the plant can pose non-target risks. We assessed the community-level effects of clothianidin-treated seed on the diversity and abundance of arthropod communities in a no-till corn agroecosystem over a single growing season. Epigeal and foliage-dwelling communities were disturbed by the clothianidin seed treatment, with significant negative and positive changes in taxa abundances. Clothianidin reduced the abundance of minute pirate bugs by 66.2%, lady beetles by 44.7%, ants by 43.4%, ground beetle adults and larvae by 31.7%, and rove beetles by 44.1% during the early corn growth stages. Herbivores, particularly thrips, were more negatively affected by clothianidin than other trophic groups. In contrast, some groups, such as collembolans and leafhoppers, exhibited significantly higher abundances in the seed treated plots. Clothianidin primarily influenced arthropod communities during the 4 weeks following planting, with disruptions to major natural enemy taxa, but communities showed trends toward recovery at the later corn stages. While the insecticide suppressed multiple herbivores, none were economically damaging to corn; thus, the pest suppression benefits of clothianidin observed in this study did not justify the non-target impacts. © 2018 Society of Chemical Industry.

Nitrogen Recovery Efficiency from Urea Treated with NSN Co-Polymer Applied to No-Till Corn

Nitrogen (N) rate increases used by many farmers produce a reduced or null effect on N recovery efficiency (RE) by crops. Therefore, management practices to reduce N losses and increase RE are necessary. Co-polymer maleic itaconic acid (NSN) have become available for use with urea and has shown potential in reducing N losses. The objective of this study was to evaluate the effectiveness of urea treated with NSN on grain yield and RE in a no-till corn. A field experiment was carried out at Balcarce, Argentina over three years, evaluated treatments were urea and urea + NSN at 120 N kg ha−1, and additional 0 N treatment was included. Urea + NSN was effective to reduce total ammonia volatilization losses, and the average of two years were 1.4 (1.1% to N applied) and 8.7 kg ha−1 (7.2% to N applied) for urea + NSN and urea, respectively. However, while grain yield and N grain removal were not affected by urea + NSN, the N rate significantly increased grain yield and N grain removal. Nitrogen recovery efficiency was not affected by urea + NSN, RE (average of three years) was 29.0% and 27.8% for urea and urea + NSN, respectively. In conclusion, there was no advantage of using urea treated with NSN in no-till corn overgrain yield, N grain removal, or RE.

Control of glyphosate-resistant giant ragweed (Ambrosia trifida L.) with premix of iodosulfuron/thiencarbazone applied alone or in tank mixtures in no-till corn (Zea mays L.)

The objectives of this study were to evaluate the efficacy of a new premix of iodosulfuron (6%)/thiencarbazone (45%) applied alone or tank-mixed with 2,4-D, dicamba, glyphosate, or metribuzin in the fall and (or) early spring followed by preemergence (PRE) and postemergence (POST) herbicide applications for control of glyphosate-resistant giant ragweed and their effect on corn yield. Field experiments were conducted in no-till corn fields infested with glyphosate-resistant giant ragweed (20–30 plants m−2) near Clay Center and McCool Junction, NE, in 2013 and 2014, respectively. A premix of iodosulfuron/thiencarbazone applied alone or in split applications in the fall and early spring controlled glyphosate-resistant giant ragweed <60% and resulted in a density of 14 giant ragweed plants m−2, which was comparable to the untreated control at 28 d after early spring treatment (DAEST). Metribuzin or 2,4-D applied alone resulted in <75% giant ragweed control at 28 DAEST; however, 2,4-D or dicamba tank-mixed with iodosulfuron/thiencarbazone provided ≥92% control. Treatments including 2,4-D or dicamba led to 85%–98% reduction in giant ragweed biomass at 28 DAEST. A follow-up application of a premix of isoxaflutole/thiencarbazone tank-mixed with atrazine applied PRE was not effective, although a POST application of tembotrione + atrazine resulted in >91% control at 28 d after postemergence treatment. The premix applied alone did not provide effective control of giant ragweed in corn primarily because lack of residual activity.

Soil Carbon Response to Projected Climate Change in the US Western Corn Belt.

The western US Corn Belt is projected to experience major changes in growing conditions due to climate change over the next 50 to 100 yr. Projected changes include increases in growing season length, number of high temperature stress days and warm nights, and precipitation, with more heavy rainfall events. The impact these changes will have on soil organic carbon (SOC) needs to be estimated and adaptive changes in management developed to sustain soil health and system services. The process-based model CQESTR was used to model changes in SOC stocks (0-30 cm) of continuous corn ( L.) and a corn-soybean [ (L.) Merr.] rotation under disk, chisel, ridge, and no-tillage using projected growing season conditions for the next 50 yr. Input for the model was based on management and harvest records from a long-term tillage study (1986-2015) in eastern Nebraska, and model output was validated using measured changes in SOC from 1999 to 2011 in the study. The validated model was used to estimate changes in SOC over 17 yr under climatic conditions projected for 2065 under two scenarios: (i) crop yields increasing at the observed rate from 1971 to 2016 or (ii) crop yields reduced due to negative effects of increasing temperature. CQESTR estimates of SOC agreed well with measured SOC ( = 0.70, < 0.0001). Validated model simulated changes in SOC under projected climate change differed among the three soil depths (0-7.5, 7.5-15, and 15-30 cm). Summed over the 0- to 30-cm depth, there were significant three-way interactions of year × rotation × yield ( = 0.014) and year × tillage × yield ( < 0.001). As yield increased, SOC increased under no-tillage continuous corn but was unchanged under no-tillage corn-soybean and ridge tillage regardless of cropping system. Under chisel and disk tillage, SOC declined regardless of cropping system. With declining yields SOC decreased regardless of tillage or cropping system. These results highlight the interaction between genetics and management in maintaining yield trends and soil C.

Profitability of Enhanced Efficiency Urea Fertilizers in No‐Tillage Corn Production

Core Ideas Urea + NBPT and PCU provided significantly higher mean yields and net returns than conventional urea. Urea + NBPT and PCU provided significantly lower yields and net returns than ammonium nitrate. Urea + NBPT and PCU offer greater potential to improve net returns than urea + MICP. This study determined the effects of enhanced efficiency (EE) urea fertilizers relative to ammonium nitrate (AN) on no‐tillage (NT) corn (Zea mays L.) yields and net returns (NRs) in Tennessee. Corn yields were from experiments conducted at two N fertilization rates of 123 and 168 kg ha−1 with four replications in a split‐plot design from 2013 through 2015 at three locations in middle (Springfield) and west Tennessee (Milan and Jackson). ANOVA analyses were used to identify differences in EE urea treatment yields and NRs. Breakeven and sensitivity analysis was used to compare yield and identify the threshold of positive NR of EE urea fertilizers relative to AN for a given premium price over conventional urea. Results indicated that urea + 20% or 26.7% N‐(n‐butyl)‐thiophosphoric triamide (NBPT) and polymer‐coated urea (PCU) provided significantly higher mean yields (2.0 Mg ha−1 more on average) and NRs ($283 ha−1 more) than conventional urea. Notwithstanding, these EE urea fertilizers had lower yields and produced lower benefits than AN in the course of this study. On the other hand, mean yield (8.7 Mg ha−1) and NR ($1012 ha−1) for urea + maleic–itaconic acid copolymer (MICP) were not significantly different from conventional urea (8.3 Mg ha−1 and $959 ha−1). In general, N fertilizer sources behaved similarly among N rates and locations. Given the growing reliance on urea fertilizer in NT corn production in Tennessee, urea + NBPT and PCU offer the greatest potential to improve expected NRs relative to conventional urea.

Legacy effects of land use on soil nitrous oxide emissions in annual crop and perennial grassland ecosystems

Land use conversions into and out of agriculture may influence soil-atmosphere greenhouse gas fluxes for many years. We tested the legacy effects of land use on cumulative soil nitrous oxide (N2 O) fluxes for 5yr following conversion of 22-yr-old Conservation Reserve Program (CRP) grasslands and conventionally tilled agricultural fields (AGR) to continuous no-till corn, switchgrass, and restored prairie. An unconverted CRP field served as a reference. We assessed the labile soil C pool of the upper 10cm in 2009 (the conversion year) and in 2014 using short-term soil incubations. We also measured insitu soil N2 O fluxes biweekly from 2009 through 2014 using static chambers except when soils were frozen. The labile C pool was approximately twofold higher in soils previously in CRP than in those formerly in tilled cropland. Five-year cumulative soil N2 O emissions were approximately threefold higher in the corn system on former CRP than on former cropland despite similar fertilization rates (~184kg N·ha-1 ·yr-1 ). The lower cumulative emissions from corn on former cropland were similar to emissions from switchgrass that was fertilized less (~57kg N·ha-1 ·yr-1 ), regardless of former land use, and lowest emissions were observed from the unfertilized restored prairie and reference systems. Findings support the hypothesis that soil labile carbon levels modulate the response of soil N2 O emissions to nitrogen inputs, with soils higher in labile carbon but otherwise similar, in this case reflecting land use history, responding more strongly to added nitrogen.

Ecosystem carbon exchange on conversion of Conservation Reserve Program grasslands to annual and perennial cropping systems

Land use changes into and out of agricultural production may substantially influence ecosystem carbon (C) balance for many years. We examined ecosystem C balances for eight years after the conversion of 22 year-old Conservation Reserve Program (CRP) grasslands and formerly tilled agricultural fields (AGR) to annual (continuous no-till corn) and perennial (switchgrass and restored prairie) cropland. An unconverted CRP field (CRP-Ref) was maintained as a historical reference. Ecosystem C balance was assessed using adjusted net ecosystem carbon exchange (NEEadj) calculated by adding C removed in harvested biomass to NEE measured using eddy covariance method. The cumulative NEEadj of the corn and perennial systems on former CRP fields showed that these systems were a net C source to the atmosphere over the 8-year period while on former AGR fields, the perennial systems were net C sinks and the corn system near-neutral. The CRP-Ref was near neutral until a drought year when it became a net source. The corn system on the CRP field will likely reach a new lower soil C equilibrium at least 14 years after conversion but will never regain the C lost upon conversion under current no-till management with residue partially removed. On the other hand, the perennial systems could fully regain in ∼14 years the C lost following conversion. The cumulative NEEadj of the corn systems exhibited a higher C emission than did the perennial systems within the same land use histories, reflecting the dominant role of crop type and management in agricultural ecosystem C balance. Results suggest that converting croplands to grasslands results in immediate C gains whereas converting grasslands to croplands results in permanent (no-till corn with partial residue removal) or temporary (perennial herbaceous crops) net C loss to the atmosphere. This has a significant implications for global climate change mitigation where biomass production from annual and perennial crops is promoted to avoid fossil-fuel C emissions (biofuel) or to remove CO2 from the atmosphere (bioenergy C capture and storage).

Understanding N timing in corn yield and fertilizer N recovery: An insight from an isotopic labeled-N determination.

Early fertilizer nitrogen (N) application on cover crops or their residues during the off-season is a practice adopted in Brazil subtropical conditions under no-tillage corn (Zea mays L.) systems. However, the effect of early N application on yield, plant N content, and N recovery efficiency (NRE) for corn is not yet well documented. Five fertilizer N timings in an oat-corn system were evaluated in two studies utilizing an isotopic-labeled N determination, 15N isotope. The N fertilization timings were: (i) oat tillering, (ii) 15 days before corn planting time, over the oat residues, (iii) at corn planting time, (iv) in-season at the three-leaf growth stage (V3), and (v) in-season split application at V3 and six-leaf (V6) growth stages. Based on the statistical analysis, the N fertilization timings were separated into three groups: 1) N-OATS, designated to N applied at oat; 2) N-PLANT, referred to pre-plant and planting N applications; and 3) N-CORN, designated to in-season corn N applications. Corn yield was not affected by the N fertilization timing. However, the N-CORN N fertilization timings enhanced NRE by 17% and 35% and final N recovery system (plant plus soil) by 16% and 24% all relative to N-OATS and N-PLANT groups, respectively. Overall, N-OATS resulted in the largest N derived from fertilizer (NDFF) amount in the deeper soil layer, in overall a delta of 10 kg N ha-1 relative to the rest of the groups. Notwithstanding corn yield was not affected, early N fertilization under subtropical conditions is not a viable option since NRE was diminished and the non-recovery N increased relative to the in-season N applications.

Energy use and greenhouse gas emissions in organic and conventional grain crop production: Accounting for nutrient inflows

Agriculture is a large source of greenhouse gas (GHG) emissions and has large energy requirements. Previous research has shown that organic farming and conservation tillage practices can reduce environmental impacts from agriculture. We used the Farm Energy Analysis Tool (FEAT) to quantify the energy use and GHG emissions on area (ha) and crop yield (kg crop) bases for five cropping systems that comprise the Farming Systems Project (FSP) at the USDA-Agricultural Research Service (ARS), Beltsville Agricultural Research Center in Maryland, US. The FSP consists of five grain cropping systems that mimic those used in the mid-Atlantic region of the US: 1) a 3-year conventional no-till corn (Zea mays L.)–soybean (Glycine max (L.) Merr)–wheat (Triticum aestivum L.)/soybean rotation (NT), 2) a 3-year conventional chisel-till corn–soybean–wheat/soybean rotation (CT), 3) a 2-year organic corn–soybean rotation (Org2), 4) a 3-year organic corn–soybean–wheat rotation (Org3), and 5) a 6-year organic corn–soybean–wheat–alfalfa (Medicago sativa L.) rotation (Org6). We accounted for nutrient inflows into organic systems by using a mass-energy allocation method, which accounts for the total energy and GHG emissions from the original production of nutrients found in poultry litter through synthetic fertilizer production (N) and nutrient mining (P and K). We believe this is the first attempt to quantify energy use and GHG emissions from nutrients applied in organic systems that originated through industrial processes used in conventional agriculture. Energy use was greatest in the conventional systems when expressed on a per area basis, with energy costs of producing synthetic N fertilizer accounting for 45 to 46% of total energy use. When expressed per unit of crop yield, energy use was greatest in Org2, lowest in Org6, and similar in Org3, NT and CT. Energy use decreased with increasing crop rotation length and complexity among organic systems whether expressed on an area or yield basis. Greenhouse gas emissions were higher in the Org2 and Org3 systems than in the conventional systems and were lowest in Org6 whether expressed on an area or yield basis. Our results indicate that organic management consistently had lower energy use than conventional management on an area basis, but not when expressed on a crop yield basis. Of particular interest is that diversifying grain cropping systems to include perennials was a more effective management strategy than organic management per se to reduce energy use and GHG emissions in agriculture.

English

The soil is the most important carbon reservoir, but agricultural practices involved in tillage systems decrease the soil carbon stock. This study aims to evaluate the effect of no-tillage (NT) on carbon and microbiological attributes of the soil in corn plantations in Manaus-AM, Brazil. Soil was sampled in a secondary forest (SF) and in corn grown under different tillage systems, including conventional tillage (CT), which makes use of plowing and harrowing operations, and no-tillage (NT). Soil variables studied included, carbon content, soil microbial carbon and basal respiration, metabolic and microbial quotients. The data were analyzed by analysis of variance and Tukey's test. The results demonstrated that NT resulted higher carbon, lower basal respiration, and lower metabolic quotient than CT and SF. However, soil microbial carbon was similar in all tillage systems studied. We conclude that NT corn cropping increased soil carbon content more than CT, while it decreased basal respiration and metabolic quotient when compared to NT and SF. Moreover, soil microbial biomass in corn was similar in all tillage systems studied. This research demonstrated the importance of NT to soil carbon conservation and soil management in corn cropping. Key words: Tillage systems, land use, microbial soil biomass, basal respiration.

Urease Inhibitor and Irrigation Management to Mitigate Ammonia Volatilization from Urea in No-Till Corn

High nitrogen (N) losses by ammonia (NH3) volatilization from urea can compromise nitrogen fertilization efficiency and corn yield. The purpose of this study was to assess the effects of irrigation management and the addition of the urease inhibitor N-(n-butyl)thiophosphoric triamide (NBPT) on NH3-N losses from urea and on corn yield. To this end, two experiments were carried out in the 2011/12 crop season on a sandy clay loam Acrisol in the Central Basin region of Rio Grande do Sul, southern Brazil. Experiment I consisted of two different N sources (urea and urea plus the inhibitor) at a rate of 200 kg ha-1 N and two corn sowing times [viz., an early time (Sept. 3, 2011) and an intermediate time (Oct. 3, 2011)]. Experiment II considered a combination of three irrigation management systems (viz., without irrigation on the fertilization day and on the next 7 days; 20 mm of water immediately before N fertilization; and 20 mm water after N fertilization) and two N sources (urea and urea plus the inhibitor) at 150 kg ha-1 N. A control treatment without topdressed N fertilization was also performed in parallel with the two experiments. The NH3-N losses from common urea increased with increasing soil moisture in Experiment I (25 % applied N), and with irrigation before N fertilization in Experiment II (27 % applied N). The inhibitor reduced NH3-N losses from urea by 46 to 80 %. Also, irrigation after fertilization reduced ammonia volatilization by 83 % on average, with little effect from the inhibitor. The effects of the inhibitor and post-fertilization irrigation on the mitigation of NH3 losses by volatilization from urea were not additive; in addition, they led to no increase in corn yield.

Integrated Weed Management Strategies in Cover Crop–based, Organic Rotational No-Till Corn and Soybean in the Mid-Atlantic Region

Cover crop–based, organic rotational no-till (CCORNT) corn and soybean systems have been developed in the mid-Atlantic region to build soil health, increase management flexibility, and reduce labor. In this system, a roller-crimped cover crop mulch provides within-season weed suppression in no-till corn and soybean. A cropping system experiment was conducted in Pennsylvania, Maryland, and Delaware to test the cumulative effects of a multitactic weed management approach in a 3-yr hairy vetch/triticale–corn–cereal rye–soybean–winter wheat CCORNT rotation. Treatments included delayed planting dates (early, intermediate, late) and supplemental weed control using high-residue (HR) cultivation in no-till corn and soybean phases. In the no-till corn phase, HR cultivation decreased weed biomass relative to the uncultivated control by 58%, 23%, and 62% in Delaware, Maryland, and Pennsylvania, respectively. In the no-till soybean phase, HR cultivation decreased weed biomass relative to the uncultivated treatment planted in narrow rows (19 to 38 cm) by 20%, 41%, and 78% in Delaware, Maryland, and Pennsylvania, respectively. Common ragweed was more dominant in soybean (39% of total biomass) compared with corn (10% of total biomass), whereas giant foxtail and smooth pigweed were more dominant in corn, comprising 46% and 22% of total biomass, respectively. Common ragweed became less abundant as corn and soybean planting dates were delayed, whereas giant foxtail and smooth pigweed increased as a percentage of total biomass as planting dates were delayed. At the Pennsylvania location, inconsistent termination of cover crops with the roller-crimper resulted in volunteer cover crops in other phases of the rotation. Our results indicate that HR cultivation is necessary to achieve adequate weed control in CCORNT systems. Integration of winter grain or perennial forages into CCORNT systems will also be an important management tactic for truncating weed seedbank population increases.