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Volume 13 Issue 1, December 2014
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Producers in eastern Kansas are beginning to use planters with 15-inch row spacing to plant hard red winter wheat (Triticum aestivum L.) vs. traditional 7- to 10-inch drill equipment. The objectives of this study were to evaluate weed emergence and wheat yield effects when sowing wheat with a 15-inch row planter vs. 7.5-inch row drill equipment at a seeding rate of 1.0 and 1.2 million seeds/acre. The experiments were duplicated each year, one with an herbicide application and one without herbicide. Henbit (Lamium amplexicaule L.), Carolina foxtail (Alopecurus carolinianus Walt.), smallflowered bittercress (Cardamine parviflora L.), and common chickweed [Stellaria media (L.) Vill.] emergence was greater in the 15-inch planter rows vs. the 7.5-inch drill rows. Wheat sown in the 15-inch planter rows in the herbicide-treated experiment yielded 17.4 bu/acre less than wheat sown with the 7.5-inch drill rows. Wheat sown with the 15-inch planter in the untreated herbicide experiment yielded 15.1 bu/acre less than wheat sown with the 7.5-inch drill. Yield losses for wheat in 15-inch planter rows in both experiments are attributed to too wide of a row spacing to maximize yields.
Separate field experiments were conducted in 2011 and 2012 to determine the influence of herbicide programs on the density of glyphosate-resistant (GR) giant ragweed, yield, and net return in glyphosate- and glufosinate-resistant soybean. In all experiments, preplant (PREPLT) applications were followed by (fb) a post-emergence (POST) herbicide program. In the GR soybean experiment, the highest density of GR giant ragweed observed 11 weeks after planting (WAP) was 244 plants per plot in response to a PREPLT application of glyphosate fb glyphosate plus fomesafen early post-emergence (EPOST) fb glyphosate late post-emergence (LPOST). All other programs resulted in 5 or less plants per plot when PREPLT applications contained a glyphosate tank-mix combination. Similarly, in the glufosinate-resistant soybean experiment, all herbicide programs resulted in 6 or less plants per plot 11 WAP. Few differences were observed in soybean yield and net return among herbicide programs that included an effective PREPLT treatment for GR giant ragweed control. Programs that contained an effective PREPLT tank-mix combination resulted in the highest yield and net return. For example, PREPLT herbicide treatments that contained more than one mode of action (MOA) provided net returns of $122.15 to $201.49/acre higher than glyphosate alone in GR soybean. Results from this research indicate that GR giant ragweed can be managed following an effective PREPLT and POST program in either soybean system.
Farmers have observed reduced early growth of corn in the presence of tansymustard [Descurainia pinnata (Walt.) Britt.], a winter annual weed of the Brassicaceae family. A greenhouse study was conducted to evaluate the effect of tansymustard on corn (Zea mays L.) emergence and early growth. Treatments included corn growing in pots with only tansymustard root residue, with only tansymustard shoot residue, and with whole tansymustard plant residue (roots plus shoots); tansymustard plants treated with glyphosate 2 days after planting (DAP) corn seeds; and a control (no tansymustard residue). Corn emergence was recorded and biomass measured after 4 weeks of growth. Time to 50% corn emergence was delayed by 1 to 2 days when tansymustard plants were treated with glyphosate. The number of emerged corn plants per pot, total corn biomass per pot, and corn height were not influenced by the presence of tansymustard residue, leading to the conclusion that relatively low quantities of tansymustard residue had no effect on corn growth in this study. The stunted corn development observed by farmers in the field may be due to competition rather than allelopathy, since tansymustard is often controlled several days after crop emergence.
Field studies were conducted from 2010 through 2012 in Oregon’s Willamette Valley to determine the effects of a strobilurin-containing fungicide applied at two growth stages on seed yield in tall fescue [Schedonorus phoenix (Scop.) Holub] crops. Stem rust (caused by Puccinia graminis subsp. graminicola) is the primary disease pest of tall fescue in the region, where seed yield losses can be as severe as 70% when the disease is not managed. Weather conditions were favorable for stem rust development in 2012; however, cool and wet conditions in 2010 and 2011 resulted in low pressure from stem rust. Strobilurin-containing fungicide treatments increased seed yield 17% over the untreated control across sites and years, but the greatest seed yield increases were noted when stem rust pressure was highest in 2012. Seed yield increases were attributable to a combination of increased seed number and weight. Cleanout was reduced by up to 18% with fungicide treatments. While fungicide treatment increased seed yield even with low disease incidence and severity, there were no effects on the plant growth or nitrogen metabolism of tall fescue. Tall fescue seed yield can be increased by application of strobilurin-containing fungicides, but the response is dependent on the incidence and severity of stem rust.
Yield and disease resistance are important components influencing potato growers’ variety selection. Potato appearance, nutritional content, and specific culinary uses often affect consumer selection. A 3-year study was conducted to investigate how red potato (Solanum tuberosum L.) yield and skin quality were affected by variety and previous crop and specifically if red potato varieties would benefit from a plowed-down high-glucosinolate mustard (HGM; Brassica spp.) cover crop. The three previous crops were barley (Hordeum vulgare L.), canola (Brassica napus L.), and HGM. Each season six red varieties were planted, and yield and skin quality were evaluated. Two red varieties were planted consistently across three growing seasons, and three were similar across two growing seasons. Potatoes were harvested, washed, graded, weighed, and rated for skin surface quality. Potato yields were influenced by variety and year (due to variable environmental conditions), but the previous crop only influenced yield in the wettest year, when potato yield increased by 19%, probably from the N released from the HGM biomass. For varieties grown across similar environments, HGM cover crops resulted in a 52% lower incidence of black scurf. Thus, HGM green manures can be used to reduce soilborne pathogens.
Interest in transitioning from perennial grasses to annual crops should increase because of renewed interest in including a perennial phase in annual crop rotations. Different tillage options for converting from perennial grasses to annual crops were evaluated at the Northern Great Plains Research Laboratory, USDA-ARS, in Mandan, ND. Previously, the study site evaluated intermediate wheatgrass [Thynopyrum intermedium (Host) Barkworth & D.R. Dewey] persistence when grazed at the early vegetative, mid-culm elongation, or late boot morphological stages. Soybeans [Glycine max (L.) Merr.] in 2005, corn (Zea mays L.) in 2006, flax (Linum usitatissimum L.) in 2007, and spring wheat (Triticum aestivum L.) in 2008 were seeded using either no-till (NT) or minimum till (MT). Tillage interacted with grazing history to impact soybean yields, total weed density in flax, and weedy grasses, such as green foxtail [Setaria viridis L. (Beauv.)], barnyardgrass [Echinochloa crus-galli L. (Beauv.)] and Kentucky bluegrass (Poa pratensis L.) in spring wheat. The use of NT generally resulted in greater yields and lower weed densities than MT, but even 4-years later, grazing still had an impact on weed populations. Our data suggest that producers should use NT rather than MT when converting from perennial grass to an annual cropping system.
Over the last 70 years, national corn yield gains have occurred because of superior genetic yield potentials and management improvements such as improved water management, higher plant densities, and earlier planting dates. Some management recommendations, such as those from seed companies that promote optimum plant densities, are often environment, hybrid, and/or yield-range specific. Nitrogen rate recommendations for corn are updated annually in the Corn Belt states and are sometimes adjusted for regions or soil zones within a state. In contrast, nutrient guidelines for nutrients other than N are assumed to be constant per unit of yield produced, and have generally not been updated in key corn-producing states. Some recent studies providing nutrient content values for corn grain and/or stover did not account for management practices and yield levels for which nutrient replacement recommendations would be pertinent. The purpose of this report is to illustrate how macro- and micronutrient contents for modern corn hybrids can change in the context of diverse plant densities, N rates, and accompanying yield range influences in certain environments. The information presented here can be used to better understand nutrient content and removal for more precisely implementing best nutrient management practices for current corn hybrids at diverse yield ranges.
A fescue hay field in the Ozark Highlands received phosphorus (P) and potassium (K) fertilizer to build up soil test levels above target levels. Fertilizer rates were applied to build the soil test P and K levels in one, four, or eight years. Averaged across eight years, hay yields were not significantly different between build-up timings. However, compared to the untreated control, hay yield and quality were significantly increased by applying P and K.
Sudangrass [Sorghum bicolor (L.) Moench var. sudanense] is an increasingly popular forage and cover crop, but farmers have questions about how to manage sudangrass residues for maximum weed suppression. The objective of this greenhouse study was to quantify the relative contribution of sudangrass root exudates (e.g., sorgoleone) and decomposing shoot residue to green foxtail [Setaria viridis (L.) P. Beauv.] suppression across a range of soil mixtures. Green foxtail emergence was reduced by up to 76% by shoot residues and by up to 55% by root exudates. Synergism between decomposing shoot residues and root exudates was observed as the combination of treatments delayed time to >50% green foxtail emergence by 4 to 12 days. Results suggest that the weed suppressive potential of sudangrass is driven by independent and synergistic effects of decomposing shoot residue and root exudates in the soil. Thus, farmers removing sudangrass shoot residue by grazing or haying could experience reduced weed suppressive benefits from this crop.
Hard red winter wheat (Triticum aestivum L.) in the U.S. Southern Plains is subject to yield losses due to a wide range of pests. Foliar-applied pesticides are commonly used to control damaging insect populations, but rescue application of foliar pesticides generally occurs at or above threshold infestation levels, commonly leading to yield losses. Further, excessive precipitation, high winds, or producer labor constraints can delay foliar application beyond economically-optimal thresholds. Insecticide seed treatment offers a method to potentially reduce wheat yield losses due to pest infestations and avoid timing and efficacy issues sometimes associated with foliar applications. Many wheat seed treatments also include a fungicide that protects wheat yield by enhancing seedling emergence, increasing early-season vigor, and preventing or reducing fall establishment of fungal diseases such as leaf rust. Our purposes here were to investigate the impact of insecticide and fungicide seed treatment on grain yield, grain volume weight, and economic return of hard red winter wheat in Oklahoma. A three-year study (2008, 2011, and 2012) was conducted at three to five western Oklahoma locations per year. In addition to seed treatment, stocker cattle were used to graze at some locations during winter months, and our analyses also considered the impact of winter grazing on yield, test weight, and economic return.
This study evaluated the influence of fall planting date on winter rye (Secale cereale L.) anthesis at three Minnesota locations for five dates from late August through October. This represents the time when fall-planted cover crops would likely be seeded in Minnesota. Earliness to anthesis is important in organic production systems where timing of rye management is affected by rye growth stage. The relationships among growing degree days (GDD), growth stage, and aboveground biomass were evaluated to predict how these factors influence anthesis date and how late in the fall rye could be planted without delaying anthesis. The study occurred in 2006 and 2007, which happened to have abnormally warm and cool growing seasons, with the earliest anthesis dates in 2007 being 25 May, 28 May, and 5 June at St. Paul, Lamberton, and Roseau, respectively, and dates in 2008 of 10 June, 11 June, and 17 June. Our results indicate that there was no fall biomass requirement but also that it was critical to accumulate at least 309 GDD in the fall so as not to delay spring anthesis. This information enables growers to choose appropriate planting dates for rye that will not delay anthesis. The optimal planting date corresponded to planting by late September (∼20) in southern and early September (∼8) in northern Minnesota.
This study measured the within-swath uniformity of both spinner and pneumatic spreaders over a range of material application rates commonly associated with precision agriculture schemes (25 to 200 lb/acre). Although small pan sampling is not appropriate for spreader rate calibration, results suggested that five of the spreaders delivered rates ranging from 50 to 200 lb/acre with reasonable accuracy. Four of the five spreaders also appeared capable of delivering an even lower rate, 25 lb/acre. Within swath coefficients of variability (CV) values ranged from 16 to 30% for the most uniform of the spreaders tested, and from 45 to 122% for the least uniform. When different products were applied by multi-bin spreaders, substantial fluctuation in measured product ratios occurred for bulk bin products. For a single spreader evaluated with a micronutrient bin, micronutrient application rates and variability were relatively consistent regardless of the co-applied bulk bin product rate. The type of spreader (spinner or pneumatic) did not appear to determine the uniformity of application. Our data suggests a within-swath CV of 20 to 30% as a reasonable uniformity target for granular fertilizer spreaders under North Carolina commercial farm conditions.
Use of enhanced-efficiency N fertilizers (EENFs) in row crop agriculture has not been well studied despite increasing interest in these N sources to increase crop yield while decreasing N loss. A field study was conducted in Central Alabama from 2009 to 2011 to compare EENFs to standard N sources in a high-residue conservation cotton production system. Nitrogen fertilizers evaluated were: urea; ammonium sulfate; urea-ammonium sulfate; controlled-release, polymer-coated urea (Environmenally Smart Nitrogen, ESN); stabilized urea (SuperU); poultry litter; poultry litter + AgrotainPlus; and an unfertilized control. Detailed plant growth characteristics were determined before defoliation. Generally, standard fertilizers resulted in the largest number of bolls and the highest boll dry weight. ESN tended to perform as well as the standards. Both poultry litter treatments performed poorly during the first year; however, poultry litter + AgrotainPlus was similar to the standards by the third year of study. In this study, the more expensive EENFs produced yields similar to those of standard fertilizers, suggesting that the former may be economically impractical at present. However, EENFs could become viable alternative fertilizer sources given their ability to reduce N loss from agricultural fields via leaching, runoff, and nitrous oxide flux. Additional research is needed on the benefits of EENFs in row-crop production systems.
Furrow diking is the practice of installing earthen dams to form small basins between crop rows to reduce water runoff and improve water retention. Furrow-diking equipment is operated shortly after planting and has been used extensively in the southern Great Plains. Research evaluating crop response to furrow diking is limited in North Carolina and other southeastern states. Experiments were conducted to determine cotton (Gossypium hirsutum L.) and peanut (Arachis hypogaea L.) yields following furrow diking in conventional and strip tillage systems. Corn (Zea mays L.) response to furrow diking was determined only in conventional tillage systems. In the experiments where tillage was compared, variability in cotton and peanut response to tillage was observed, whereas diking did not affect yield of these crops. In separate experiments with conventional tillage only, peanut and corn yields were not affected by the diking treatment. However, in one experiment conducted at five sites in conventional tillage only, cotton yield increased by 7% when furrow diking was included. Although these results indicate that peanut and corn may be nonresponsive to furrow diking on coarse-textured soils in the coastal plain of North Carolina, additional research is needed to make a concrete assessment of potential of furrow diking on these crops. While variability was noted when comparing experiments, cotton responded favorably to furrow diking.
The variability of soil productivity is a problem in many agricultural experiment station fields, where field uniformity is needed for research conducted in small plots. The objective of this study was to evaluate the effects of applied amendments on the spatial variability of selected soil chemical properties and crop yield. Between 1993 and 1997, soil samples were collected from the top 6-inches of a 5-acre production field in a grid pattern and physical and chemical properties of the soil were determined following the application of ag-lime or S to adjust soil pH and fertilizer P and K to adjust soil test P and K availability index values. The initial soybean (Glycine max [L.] Merr.) seed yield ranged from 7.9 to 34.8 bu/acre with a CV of 20%, whereas the final soybean seed yield was significantly greater than that in 1993, ranging from 28.4 to 49.0 bu/acre, and had a lower CV of 11%. While field means for soil-test P and K were generally significantly greater in subsequent years compared to 1993 values, their uniformity did not improve greatly. Uniformity of soil pH and yield increased as measured by a decrease in the range and CV of these properties. Spatially applied soil amendments can be used effectively to improve crop yield uniformity, particularly in agricultural experiment station fields that require uniform soil-surface properties for small-plot research.
Growers in the low-rainfall, winter wheat (Triticum aestivum L.)–summer fallow region of the Pacific Northwest (PNW) need an alternative crop to diversify markets, manage pests, and increase wheat yields. Winter canola (Brassica napus L.) may be a viable option for this region. However, agronomic research for winter canola in this region has not been conducted, and growers are reluctant to produce winter canola because of poor stand establishment. This study evaluated various winter canola planting dates and rates on stand establishment and yield. Research and grower experience has indicated that winter canola needs to be planted in August with postplant temperatures ≤85°F for successful stand establishment and an acceptable yield (>1500 lb/acre). Canola planted in September (or very late August), unless covered by snow, either did not survive freezing temperatures or yielded <900 lb/acre. Winter survival ranged from 56 to 83%. In general, the 4 lb/acre seeding rate was sufficient for stand establishment and yield, and higher seeding rates did not improve yield. A spring plant population of 2 to 4 plants/ft2 will yield optimally. Integration of winter canola into the low-rainfall, wheat-fallow region of the PNW will increase farm sustainability by improved pest management strategies and diversified production systems and markets.
Farm-scale experiments were conducted in North Carolina during 2006–2009 in continuous cotton (Gossypium hirsutum L.), continuous soybean [Glycine max (L.) Merr.], and corn (Zea mays L.)–soybean rotation crop systems to compare growers’ standard weed management practice (SP) with best management practice (BMP) recommended by university weed scientists to delay or prevent the evolution of herbicide-resistant weeds. The BMP included a greater diversity of herbicides and number of herbicide applications over the 4 years of the experiment. For the continuous cotton–soybean crop systems, increases in herbicide cost, crop yield, and economic return were noted with the BMP compared with the SP. Soybean yields increased with the BMP in the corn–soybean rotation. However, corn yield and economic return of the rotation did not increase with the BMP. The diversity of herbicide active ingredients, often reflecting diversity of herbicide modes of action (MOA), increased with the BMP. Weed population density was lower with the BMP before postemergence (POST) herbicide application for continuous cotton and soybean but did not differ for the corn–soybean rotation. These data suggest that the more intensive and herbicide-diverse BMP was at least as cost effective as the lower-priced SP. The economic benefits of the BMP increased as crop price increased.
Weed management imposes the largest constraint on field crop production under organic management systems. Research was conducted to identify winter wheat genotypes with good yield potential that are competitive with weeds for use in organic systems. Thirty winter wheat genotypes were evaluated over two years for ability to compete against weeds and for grain yield production in southeastern South Dakota. Genotypes evaluated showed significant differences in suppression of weed production and in grain yield performance; however, genotype-by-season interaction was significant suggesting that different environmental conditions between the two seasons influenced genotype rankings. Weed biomass showed a negative relationship with crop shoot biomass. Certain released cultivars (Jerry and Scout66 winter wheat) and advanced breeding lines (NE03490 winter wheat, and NE42G2T and NT01451 winter triticale) showed promising results in terms of weed suppression and acceptable grain yield.
Peanut (Arachis hypogaea L.) rotation systems most often include corn (Zea mays L.) and cotton (Gossypium hirsutum L.). However, more diverse rotation systems can be found in some regions of North Carolina, and rotations of peanut with clary sage (Salvia sclarea L.), snap bean (Phaseolus vulgaris L.), and sweet potato [Ipomoea batatas (L.) Lam.] have increased in recent years. Research was conducted to determine visible estimates of disease expressed in the peanut canopy, plant parasitic nematode population in soil, and yield of peanut after rotations including clary sage, corn, cotton, soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.). The percentage of the peanut canopy reflecting symptoms associated with a combination of Cylindrocladium black rot and tomato spotted wilt was not affected by rotation but was 8% higher for the peanut cultivar Phillips compared with the cultivar Bailey. Peanut yield was affected by rotation and cultivar but not the interaction of these treatment factors. Peanut yield following a rotation of cotton–corn–sweet potato exceeded that of cotton–corn–cotton. In contrast, yield following the rotation of snap bean-wheat-clary sage was lower than yield following cotton-corn-cotton. Rotation affected density of lesion and ring nematodes but density did not relate to differences in peanut yield. Results from this experiment indicate that peanut can be grown immediately following sweet potato but not following the rotation of snap bean, wheat, and clary sage without a reduction in peanut yield.
Hybrid seed corn costs rose from about $35.00/acre in 1998 to more than $100.00 by 2010 primarily because of genetic modification with multiple traits for both insect and herbicide resistance, known as gene stacking. This study compared costs, yields, net returns per acre, and yield components for ten hybrids (four stacked-gene, four glyphosate-tolerant, and two non-genetically modified organisms [GMO]) in a 2-year, furrow irrigated experiment at Stoneville, MS. The site was a Tunica clay (clayey over loamy, smectitic, nonacid, thermic Vertic Haplaquept). The stacked-gene, glyphosate-tolerant, and non-GMO hybrids did not differ in input costs, yield, or net returns per acre within a year. Yields and net returns were greater in 2011 than 2012. Drought during May and two later prolonged cloudy periods in 2012 contributed to lower stands (a reduction of 2500 plants/acre) and fewer kernels per plant (533 vs. 292 for 2011 and 2012, respectively), which reduced yields (∼25%) and net returns (∼50%) compared with 2011. Non-GMO hybrids had yields and net returns similar to most stacked-gene hybrids both years when insect pressure was negligible and postemergence weed control was unnecessary. Production of some non-GMO hybrids requiring preemergence herbicides should help protect against glyphosate-resistant weeds and sustain the insect resistance of Bt genotypes by providing a refuge without an economic penalty.
In northern climates, establishment of fall cover crops after corn or soybean harvest is difficult due to cold and dry conditions. This study examined an alternative option: in-season cover crop seeding, timed for plants to emerge just following the critical weed-free period of corn (Zea mays L.) to allow establishment and growth without compromising yield. Crimson clover (Trifolium incarnatum L.), lentil (Lens culinaris Medik.), and winter wheat (Triticum aestivum L.) seed was blended and either drill (DRL) or broadcast (BRD) seeded into corn at the five-leaf (V5; late June) growth stage at three South Dakota sites (7 site years) and at V3 at one site in 2 years. Visual observations in mid-July verified establishment, and aboveground live (e.g., green) biomass was quantified at about R4 (soft dough), prior to corn grain harvest. Cover crop establishment and growth were superior with DRL seeding, which had rapid establishment and more aboveground biomass compared with BRD seeding. Although the total biomass in the V3 and V5 DRL treatments was similar, corn yield was reduced 10% in the V3 seeded plots but was unaffected by V5 seeding. Soil microbial communities were similar to the no-cover-crop control. Our results suggest that cover crops can be established successfully in standing corn at the V5 growth stage without compromising grain yield.
High-residue farming and crop diversification practices are replacing conventional tillage and crop-fallow in the Great Plains. Our objective was to determine if cultivar ranking changed when six barley (Hordeum vulgare L.) cultivars were grown following canola (Brassica napus L.), corn (Zea mays L.), pea (Pisum sativum L. subsp. sativum), and spring wheat (Triticum aestivum L. emend. Thell.) from 2010 through 2013 in southwestern North Dakota. An interaction between the previous crop and barley cultivar was detected in 2011 and 2013 for grain yield (P < 0.10). However, one cultivar in 2011 and three cultivars in 2013 produced equal or greater yields than those produced by other cultivars, regardless of previous crop. Grain yield was comparable with or greater following field pea to that following other crops in 2010 and 2012 when a previous crop × cultivar interaction did not exist. Interactions between the previous crop and barley cultivar occurred in only 2 of 12 instances for grain quality traits, and even then at least one cultivar was among the top performers consistently after each previous crop treatment. These results suggest that the previous crop is not an important consideration when making barley cultivar recommendations.
Panicle caterpillars are economically important pests of sorghum throughout the Great Plains of the United States. Sorghum producers, crop consultants, and extension professionals desire to manage panicle caterpillars to minimize economic loss. To manage panicle caterpillars in this manner, sorghum fields must be sampled to facilitate optimal control decisions for this pest complex. The decision support system (DSS) described here contains a simple expert system to calculate the economic threshold for panicle caterpillars in any sorghum field. This article reports the development of the DSS, which is based on a knowledge representation model that is easy to use and requires no specialized training. Our web-based DSS application is accessible through most web browsers on personal computers having access to the Internet.
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