Tony J. Vyn

Impacts of Zone Tillage and Red Clover on Corn Performance and Soil Physical Quality

benefits of conservation tillage with the yield benefits of conventional moldboard plow tillage (e.g., Pierce et Despite extensive research, reduced corn (Zea mays L.) performance is still encountered using conservation tillage on fine-textured al., 1992) for cool humid climatic zones. Here, a narrow soils in cool humid temperate climates. These problems are intensified zone 10 to 20 cm wide by 10 to 30 cm deep is conventionwhen corn is planted into residue from a previous crop such as winter ally tilled in the crop row while the rest of the soil surface wheat (Triticum aestivum L.). The objective of this 4-yr study was is left in an untouched no-till state. This supposedly to determine the influence of fall zone tillage (ZT), no tillage (NT), encourages the more favorable soil temperature, moisand conventional moldboard plow tillage (CT) (fall plowing) on corn ture, aeration, density, and strength conditions associperformance and soil physical quality under a winter wheat–corn– ated with conventional tillage in the narrow seedbed soybean (Glycine max L. Merr.) rotation with and without red clover (Trifolium pratense L.) (RC) underseeded in the wheat phase of the zones, while retaining the increased erosion resistance, rotation. A randomized complete block design (3 2 factorial, 4 organic matter protection and reduced energy inputs of replicates) was established on three adjacent fields in the fall of 1996 no tillage between the zones. Although there is much on a Brookston clay loam soil (fine loamy, mixed, mesic, Typic Argiainterest in the zone-till system, it has not yet been tested quoll) at Woodslee, ON Canada, and measurements were collected extensively in cool humid temperate climates, nor on during 1997 to 2000. Over both wet and dry growing seasons from the agriculturally important clay and clay loam soils of 1998-2000, zone tillage following underseeded RC produced average southern Ontario. In nearby Michigan, ZT on sandy corn grain yields (7.23 Mg ha 1) that were within 1% of those obtained using conventional tillage (7.33 Mg ha 1), and 36% higher than those loam soils did indeed improve potato (Solanum tuberoobtained using no tillage and RC (5.33 Mg ha 1). Zone tillage also sum L.) yields and soil physical conditions relative to improved soil quality as evidenced by generally lower soil strength conventional tillage in most years of a 4-yr study (Pierce than no tillage, and near-surface soil physical quality parameters that and Burpee, 1995); however, corn yields were not inwere equivalent to, or more favorable than, those of the other treatcreased by zone tillage in a similar 3-yr study, despite ments. It was concluded that corn production using zone tillage and substantially reduced soil strength (penetration resisRC underseeding is a viable option in Brookston clay loam soil, as it retains much of the soil quality benefit of conventional tillage but tance) within the 0to 30-cm depth range (Pierce et still achieves most of the yield benefit of conventional moldboard al., 1992). plow tillage. Red clover underseeded in cereals can produce large quantities of plant biomass and it fixes N in the nodules, which can in turn provide the equivalent of 90 to 125 C systems, such as no-till, have kg N ha 1 to the following crop (Bruulsema and Christie, been demonstrated to have several advantages 1987). In addition, RC can be effective in cool-temperover conventional moldboard plow systems, including ate climates for increasing microbial biomass, improving reduced soil erosion and surface runoff, slower loss of the structure of fine-textured soils (Drury et al., 1991), soil organic matter, and lower production costs. Howand for accelerating the decomposition of surface crop ever, there are many reports of reduced corn emergence residues (Drury et al., 1999). It was consequently hyand yields under no-till relative to conventional till on pothesized that including RC underseeding in a crop fine-textured soils in humid and cool temperate clirotation might further improve the potential yield and mates. This appears to be primarily a result of spring soil quality benefits of zone tillage on fine-textured soils. soil conditions that are cooler (Graven and Carter, 1991; The objective of this study was to determine, for a Fortin and Pierce, 1990; Fortin and Pierce, 1991) and clay loam soil in southern Ontario, if zone tillage and wetter (Fortin, 1993) relative to conventional tillage, RC underseeding could achieve corn yields comparable plus other factors such as increased soil bulk density with conventional moldboard plow tillage, but still reand strength (e.g., Hill, 1990; Pierce et al., 1992), detain most of the soil quality, environmental, and reduced creased soil air-filled porosity and saturated hydraulic energy inputs of no tillage. To accomplish this, convenconductivity (e.g., Pierce et al., 1992), and desiccation of seeds or seedlings through reopening of the planting tional moldboard plow tillage, no tillage, and zone-tillage slot produced by the no-till planter (Drury et al., 1999). systems were applied to a winter wheat–corn–soybean Zone tillage has been proposed as a possible alternarotation, with and without RC underseeded in the wintive tillage system that may combine the soil quality ter wheat. Evaluations were made on the basis of corn emergence, corn yield, and near-surface soil physical C.F. Drury, C.S. Tan, W.D. Reynolds, T.W. Welacky, S.E. Weaver, quality. and A.S. Hamill, Greenhouse & Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, ON, Canada N0R 1G0. T.J. Vyn, Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907Abbreviations: CHU, corn heat unit; CT, conventional moldboard 1150. Received 22 Jan. 2002. *Corresponding author (druryc@agr. plow tillage; FC, field capacity; NT, no tillage; PR, penetration resisgc.ca). tance; PWP, permanent wilting point; RC, red clover; WAS, wet aggregate stability; ZT, zone tillage. Published in Soil Sci. Soc. Am. J. 67:867–877 (2003).

Nitrogen fertilization and cover crop effects on soil structural stability and corn performance

Abstract The effects of annual ryegrass (Lolium multiflorum L.), red clover (Trifolium pratense L.), and oilseed radish (Raphanus sativus L.) established in separate barley (Hordeum vulgare L.) and winter wheat (Triticum aestivum L.) plots which had received 0.5, 1.0, and 2.0 times the recommended nitrogen (N) rates (in Ontario) on soil structural stability and subsequent corn (Zea mays L.) growth and yield were investigated in field studies at Ayr and Woodstock, Ontario. Soil aggregate stability and corn growth and development were affected more by cover crops than applied N. Generally, aggregate stability was higher following cover crops than where no cover crops were used. Aggregate stability before spring tillage tended to be higher after oilseed radish than ryegrass and clover, a phenomenon which might be due to short‐term enrichment of soil stabilizing materials resulting from the over‐winter kill of oilseed radish and early decomposition. However, after spring chisel low, soil stability was higher ...

Influence of crop rotation and tillage on production of apothecia by Sclerotinia sclerotiorum

Field experiments were conducted at Marden and Arkell, in southwestern Ontario, from 1995 to 1998 to assess the influence of crop rotation and tillage on production of apothecia by Sclerotinia sclerotiorum. Treatments included five 2-year crop rotations of continuous soybean, corn–soybean, soybean–corn, winter wheat – soybean, and soybean – winter wheat in combination with minimum tillage, no tillage with residue chopped after harvest, or no tillage with no disturbance of residue after harvest. Crop rotation had a significant effect on the production of apothecia in all years at both sites (except for Arkell in 1998) and, in general, lower mean numbers of apothecia and (or) clumps of apothecia were recorded in plots planted with corn or winter wheat than with soybean. In all years, and at both sites (except Arkell in 1995), there were fewer apothecia and clumps of apothecia in the no-tillage treatments than in minimum tillage, although the difference was not statistically different in all years. Interactions between crop rotation and tillage were only significant in 1996 and 1997 at Marden where apothecia production was greatest in minimum-tillage plots planted with soybean, regardless of the preceding crop. Within the two no-tillage treatments, plantings of continuous soybean produced the highest number of apothecia and clumps of apothecia, and there was a 46.4 and 80.6% reduction in the numbers of apothecia at Marden in 1996 and 1997, respectively, in the no-tillage with chopped residue treatments when any crop rotation was followed compared with continuous cropping of soybean. The results of this study established that crop rotation and no tillage of soybean was the most useful combination of treatments that reduced the primary inoculum (e.g., apothecia) of S. sclerotiorum in infested soybean fields.

Evaluation of strip tillage systems for corn production in Ontario

Abstract Strip tillage, which involves cultivation of a narrow strip in the row area, has the potential advantages of providing a suitable seedbed for corn ( Zea mays L.) production with minimum energy expenditures, while leaving surface residues in the interrow area to reduce soil erosion. A study was conducted where three rotary tillage implements (Howard Rotaspike, Howard Rotavator, and Lely Roterra, The Lely Corporation, Suffolk, UK) and a former interrow cultivator were modified to cultivate a strip 25 cm wide in the row area. These strip tillage implements were compared with fall moldboard plow, fall chisel plow, and no-till tillage systems for 3 years of continuous corn production on sandy loam, silt loam, and clay loam soils in southern Ontario. The strip tillage treatments left significantly higher amounts of surface residue than either the moldboard plow or the chisel plow and thus provided potential soil conservation benefits. The moldboard plow system resulted in a greater proportion of fine aggregates in the seedbed than strip tillage, and strip tillage generally had more fine aggregates than no-till. Plant growth with strip tillage tended to be delayed compared with the moldboard plow treatment on all three soils. Average strip tillage yields were 10.3 and 12% lower than the moldboard plow treatments for the silt loam and clay loam soils, respectively. On the clay loam soil, differences were not significant between the strip tillage and chisel plow or no-till treatments. On the sandy loam soil, average strip tillage yields were significantly lower than the moldboard plow treatment in 1 year out of 3, equal to chisel plow in all 3 years, and higher than no-till in 2 years out of 3. Among the strip tillage treatments, the Howard Rotaspike and Howard Rotavator often resulted in finer seedbeds, better plant growth, and higher yields than the Lely Roterra and strip-till cultivator. The Howard strip tillage implements tended to compare most favorably with the moldboard plow tillage system.

Nitrous oxide emissions in Midwest US maize production vary widely with band-injected N fertilizer rates, timing and nitrapyrin presence

Nitrification inhibitors have the potential to reduce N2O emissions from maize fields, but optimal results may depend on deployment of integrated N fertilizer management systems that increase yields achieved per unit of N2O lost. A new micro-encapsulated formulation of nitrapyrin for liquid N fertilizers became available to US farmers in 2010. Our research objectives were to (i) assess the impacts of urea‐ammonium nitrate (UAN) management practices (timing, rate and nitrification inhibitor) and environmental variables on growing-season N2O fluxes and (ii) identify UAN treatment combinations that both reduce N2O emissions and optimize maize productivity. Field experiments near West Lafayette, Indiana in 2010 and 2011 examined three N rates (0, 90 and 180 kg N ha 1 ), two timings (pre-emergence and side-dress) and presence or absence of nitrapyrin. Mean cumulative N2O‐N emissions (Q10 corrected) were 0.81, 1.83 and 3.52 kg N2O‐N ha 1 for the rates of 0, 90 and 180 kg N ha 1 , respectively; 1.80 and 2.31 kg N2O‐N ha 1 for pre-emergence and side-dress timings, respectively; and 1.77 versus 2.34 kg N2O‐N ha 1 for with and without nitrapyrin, respectively. Yield-scaled N2O‐N emissions increased with N rates as anticipated (averaging 167, 204 and 328 g N2O‐N Mg grain 1 for the 0, 90 and 180 kg N ha 1 rates), but were 22% greater with the side-dress timing than the pre-emergence timing (when averaged across N rates and inhibitor treatments) because of environmental conditions following later applications. Overall yield-scaled N2O‐N emissions were 22% lower with nitrapyrin than without the inhibitor, but these did not interact with N rate or timing.

Spatial Analysis of Yield Monitor Data: Case Studies of On-farm Trials and Farm Management Decision-making

A 3-year case study was undertaken of how North American farmers use yield monitors for on-farm trials in farm management decision making. Case study methods were used because relatively few farmers quantitatively analyze yield monitor data. At this early research stage, insufficient farm management information about the data was available to ask the right questions in a large-scale survey. In addition to the formal case study of farmers experienced at using yield monitors to collect on-farm trial data, the study evaluated the effect of yield monitor data quality on farm decisions. Two levels of yield data quality included standard output where the default settings of farm-level mapping software were accepted and where filtering of the data was undertaken. Results indicated that yield data quality affects farm management decisions. In addition, farmers receiving a spatial analysis of their on-farm trial data tended to use split-field designs instead of replicated split-planter designs. They were also more confident in their decisions than before participation in the spatial analysis project, and made decisions more quickly.

Maize Plant Resilience to N Stress and Post-silking N Capacity Changes over Time: A Review

We conducted a synthesis analysis on data from 86 published field experiments conducted from 1903 to 2014 to explore the specific consequences of post-silking N accumulation (PostN) in New Era vs. Old Era hybrids on grain yield (GY) and recovery from plant N stress at flowering (R1 stage). The Old Era encompassed studies using genotypes released before, and including, 1990 and the New Era included all studies using genotypes released from 1991 to 2014. Mean N fertilizer rates for experiments in the Old and New Era were similar (170 and 172 kg ha−1, respectively), but plant densities averaged 5.0 plants m−2 in the Old Era vs. 7.3 plants m−2 in the New Era studies. Whole-plant N stress at R1 for each hybrid, environment and management combination was ranked into one of three categories relative to the N Nutrition Index (NNI). The key findings from this analysis are: (i) New Era genotypes increased the proportion of the total plant N at maturity accumulated post-silking (%PostN) as N stress levels at R1 increased—demonstrating improved adaptability to low N environments, (ii) New Era hybrids maintained similar GY on a per plant basis under both low and high N stress at R1 despite being subject to much higher population stress, (iii) PostN is more strongly correlated to GY (both eras combined) when under severe R1 N stress than under less acute N stress at R1, (iv) the New Era accumulated more total N (an increase of 30 kg N ha−1) and higher %PostN (an increase from 30% in Old to 36% in New Era), and (v) the change in stover dry weight from silking to physiological maturity (ΔStover) has a positive, linear relationship with PostN in the Old Era but less so in the New Era. This increased understanding of how modern genotypes accumulate more N in the reproductive stage and have more PostN and GY resilience to mid-season N stress, even when grown at much higher plant densities, will assist trait selection and N management research directed to improving maize yields and N efficiencies simultaneously.

Mapping Density Response in Maize: A Direct Approach for Testing Genotype and Treatment Interactions

Maize yield improvement has been strongly linked to improvements in stress tolerance, particularly to increased interplant competition. As a result, modern hybrids are able to produce kernels at high plant population densities. Identification of the genetic factors responsible for density response in maize requires direct testing of interactions between genetic effects and density and evaluation of that response in multiple traits. In this article we take a broad view of the problem and use a general approach based upon mixed models to analyze data from eight segmental inbred lines in a B73 background and their crosses to the unrelated parent Mo17 (hybrids). We directly test for the interaction between treatment effects and genetic effects instead of the commonly used overlaying of results on a common map. Additionally, we demonstrate one way to handle heteroscedasticity of variances common in stress responses. We find that some SILs are consistently different from the recurrent parent regardless of the density, while others differ from the recurrent parent in one density level but not in the other. Thus, we find positive evidence for both main effects and interaction between genetic loci and density in cases where the approach of overlapping results fails to find significant results. Furthermore, our study clearly identifies segments that respond differently to density depending upon the inbreeding level (inbred/hybrid).

Direct mapping of density response in a population of B73 × Mo17 recombinant inbred lines of maize ( Zea Mays L.)

Maize yield per unit area has dramatically increased over time as have plant population densities, but the genetic basis for plant response to density is unknown as is its stability over environments. To elucidate the genetic basis of plant response to density in maize, we mapped QTL for plant density-related traits in a population of 186 recombinant inbred lines (RILs) derived from the cross of inbred lines B73 and Mo17. All RILs were evaluated for growth, development, and yield traits at moderate (50 000 plants per hectare) and high (100 000 plants per hectare) plant densities. The results show that genetic control of the traits evaluated is multigenic in their response to density. Five of the seven loci significant for final height showed statistical evidence for epistatic interactions. Other traits such as days to anthesis, anthesis-to-silking interval, barrenness, ears per plant, and yield per plant all showed statistical evidence for an epistatic interaction. Locus by density interactions are of critical importance for anthesis-to-silking interval, barrenness, and ears per plant. A second independent experiment to examine the stability of QTL for barrenness in a new environment clearly showed that the multilocus QTL were stable across environments in their differential response to density. In this verification experiment, the four-locus QTL was used to choose lines with the four unfavorable alleles and compare them with the lines with four favorable alleles and the effect was confirmed.

Wheat straw placement effects on total phenolic compounds in soil and corn seedling growth

The effects of placement of wheat (Triticum aestivum L.) straw on the release of phenolic compounds potentially phytotoxic to corn (Zea mays L.) seedling growth were examined in plastic pots under controlled conditions in growth cabinets. The treatments were soil only (control), soil with straw only in the top 2.5 cm, and soil with mixed straw. Each of these treatments was either sown or not sown with corn. Corn radicle length and seedling biomass were significantly reduced, relative to other treatments, when wheat straw was present only in the top layer of soil. Water extracts from soil with surface straw had higher amounts of total phenolic compounds than the other treatments at each of the sampling times. The concentration of phenolic compounds increased with time, with average amounts at 14 and 28 d being 53 and 77%, respectively, of the concentration at 42 d. The presence of corn reduced the amount of phenolic compounds at 14 and 42 d compared with when corn was absent (P = 0.01). Water extracts prep...