[PDF] Impact Of Cover Crops On Weed Abundance And Nitrogen Contribution In Broccoli Brassica Oleracea Var Italica Production Systems In The Maritime Pacific Northwest eBook

Author : Timothy John O'Brien
Publisher :
Page : 192 pages
File Size : 25,38 MB
Release : 1997
Category : Broccoli
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Field and greenhouse experiments were conducted in 1996 and 1997 to evaluate the effects of integrating conservation tillage and cover cropping on broccoli production as well as agroecological parameters. A field experiment was conducted during 1996-97 at the Oregon State University Horticulture Research farm near Corvallis, OR. The specific objectives of the research project were: To evaluate the effects of the integration and management of cover crops and strip-tillage on: 1) broccoli yield, 2) weed populations, and 3) relative abundance of earthworms. The experimental design was a split-split-plot in randomized complete blocks with 3 replications. Two tillage types (strip and conventional) constituted the main effects; two cover crops comprised the sub-effects. Time of cover crop suppression (early or late glyphosate) constituted the second sub-effect within the cover crop treatments. Strip-till plots had significantly lower total weed density than conventional till plots. 'Dacold' rye and vetch plots in combination with early glyphosate and strip-tillage had the highest broccoli yield. An on-farm research experiment was conducted during the summer of 1996 at Crestview Farms, Inc. near Molalla, OR. to compare strip-till and conventional tillage on broccoli yield. After the fall sown (1995) cover crop mixture 'Steptoe' barley / common vetch was chemically suppressed in the spring, two tillage regimes consisting of: striptillage and disc/harrow tillage were evaluated for their impact on broccoli yield, relative earthworm abundance, and relative Carabidae and Staphylinidae beetle abundance. The experimental design was a randomized complete block with three replications. No significant differences were detected for broccoli yields between the two tillage regimes, nor were statistical differences detected for Carabidae beetle relative abundance under the different tillage regimes. The carabid sampling period was only two weeks thus not allowing for justifiable conclusions to be drawn. Significantly higher densities of earthworms were detected in the strip-till plots on the first sample date but no earthworms were found on the second sampling date. A field experiment was conducted during 1996-97 in a cherry (Prunus avium) orchard at the Botany and Plant Pathology Research Farm near Corvallis, OR. The objective of this research was: 1) To evaluate the effectiveness of formalin, xylene, and ground cooking mustard in estimating relative abundance of the earthworm, Lumbricus terrestris, and 2) To evaluate the effectiveness of the three expulsion materials at three different times of the year. The mustard treatment extracted statistically similar numbers of L. terrestris as the formalin treatment in the fall and winter experiments but fewer worms in the spring experiment. The xylene treatment extracted significanlty fewer L. terrestris than formalin and mustard in all three sample dates. Three greenhouse studies were conducted in 1996 and 1997 to evaluate the effects of two agricultural by-products (meadowfoam meal and hydrolyzed com gluten) and a cover crop 'Monida' oat (Avena sativa) on the biomass accumulation of broccoli (Brassica oleraceae var. italica (direct seeded and transplanted), sweet corn (Zea mais), barnyardgrass (Echinichloa crus-gali), and pigweed (Amaranthus retrqflexus). The addition of meadowfoam meal to sterile greenhouse potting mix significantly reduced broccoli biomass (direct seed by 34% and transplanted by 50%) when compared to controls. Hydrolyzed corn gluten significantly reduced sweet corn biomass by 46% when compared to controls.'Monica' oat reduced the biomass of both weeds as well as broccoli (direct seeded). Results suggest that hydrolyzed corn gluten and meadowfoam meal inhibit the biomass accumulation of barnyardgrass and pigweed.

Author : Amy Michelle Garrett
Publisher :
Page : 208 pages
File Size : 15,15 MB
Release : 2010
Category : Broccoli
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Legume cover crops can serve as important sources of nitrogen (N) in sustainable agriculture and can be economically beneficial when fertilizer inputs are reduced without a yield reduction. Synchronizing N mineralization from organic materials with the needs of the subsequent crop is a challenge for organic growers. Predicting plant available nitrogen from cover crop residue enables N fertilizer inputs to be adjusted for optimum economic yield and reduced environmental risk. An experiment was conducted near Corvallis, OR in 2006 through 2008 to evaluate cover crop and N effects in organic broccoli production in western Oregon. The specific objectives of this experiment were to: 1) evaluate biomass production and N accumulation from selected cover crop treatments; 2) compare the effects of selected cover crops grown as sole crops and as mixtures on broccoli yield, yield components, and net economic benefit; 3) estimate the quantity of feather meal N replaced by cover crops 4) estimate plant available nitrogen from cover crop residue in an organic broccoli production system; 5) evaluate soil NO3−N and petiole NO3−N as predictors of broccoli yield; and 6) evaluate models derived from laboratory incubation of cover crop residue to predict apparent nitrogen recovery (ANR) from cover crop residue in the field. The cover crop treatments included common vetch (Vicia sativa), phacelia (Phacelia tanacetifolia), 'Monida' oats (Avena sativa L.), phacelia plus common vetch, and 'Monida' oats plus common vetch. A fallow treatment was used as the control. Prior to incorporation, cover crop samples were collected from each block and frozen for later use in laboratory aerobic incubations. After the cover crops were flail-mowed and incorporated, four N rates (0, 100, 200, and 300 kg N ha−1) were randomized within each cover crop treatment in a split plot design. All cover crop treatments produced much less biomass and accumulated less N in 2008 than in 2007. Planting vetch with oats or phacelia increased biomass production and N accumulation compared to sole crops in 2007 but not in 2008. Common vetch as a sole crop or in a mixture increased broccoli yield with 0 and 100 kg N ha−1 applied compared to fallow. Legume cover crop mixtures with 100 kg N ha−1 produced similar net economic returns for organic compared to fallow treatments with 300 kg N ha−1. Nitrogen fertilizer input can be reduced by at least 100 kg N ha−1 if common vetch is in the mixture and produces more than 5000 kg ha−1 of biomass (130-180 kg N ha−1). Vetch as a sole crop produced higher levels of soil NO3−N than the fallow treatments up to 80 days after soil incorporation in 2007. Oats and phacelia as sole crops, however, reduced soil NO3−N compared to fallow for up to 68 days after incorporation. Vetch mixtures with oats or phacelia produced intermediate levels of soil NO3−N between vetch as a sole crop and the fallow. Treatment effects were similar in 2008, but differences were less due to reduced cover crop biomass compared to 2007. Broccoli petiole nitrate levels were not affected by cover crop treatment in 2007, and there was no correlation with yield. In 2008, the oat cover crop treatment reduced broccoli petiole nitrate levels compared to the fallow. Petiole nitrate levels were strongly correlated with broccoli yield, with highest yields associated with petiole NO3− N greater than 10,000 ppm. In the aerobic incubations with cover crop mixtures, a quadratic model described the relationship of percent N in the mixture to the apparent nitrogen recovery (ANR) at both 4 and 10 weeks. The highest ANR (about 40 percent) was similar for both extraction days. Net mineralization occurred when the percent N of the cover crop mixture was 1.5-1.8 percent. There was a strong correlation in 2007 between the ANR predicted by the incubation-derived model and the ANR in the soil and in the aboveground broccoli biomass. The model over predicted the ANR in the field soil, however the model more accurately predicted ANR in the broccoli biomass. The incubation model correctly predicted negative ANR values for the oat and phacelia cover-crop treatments. In 2008, the laboratory-predicted ANR and the field soil ANR were correlated (r2=.45), and the laboratory model over predicted the field ANR. The incubation model gave a poor prediction of broccoli biomass ANR.

Author : George Yakubu Mahama
Publisher :
Page : pages
File Size : 18,91 MB
Release : 2015
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Leguminous cover crops systems have been envisaged as a critical component of sustainable agriculture due to their potential to increase soil productivity through cycling of carbon (C) and nitrogen (N) in agricultural systems. The objectives of this study were to evaluate the performance of leguminous summer cover crops; cowpea [Vigna unguiculata (L.) Walp.], pigeon pea [Cajanus cajan (L.) Millsp], sunn hemp (Crotalaria juncea L.) and double-cropped grain crops; grain sorghum [Sorghum bicolor (L.) Moench] and soybean [Glycine max (L.) Merr.] after winter wheat (Triticum aestivum L.) and to determine the effects of these crops and varying N rates in the cropping system on nitrous oxide (N2O) emissions, growth and yield of succeeding grain sorghum and maize (Zea mays L.) crop, soil aggregation, aggregate-associated C, and N. Field and laboratory studies were conducted for two years. The cover crops and double-cropped grain crops were planted immediately after winter wheat harvest. The cover crops were terminated at the beginning of flowering. Nitrogen fertilizer (urea 46% N) rates of 0, 45, 90, 135, and 180 kg N ha−1 were applied to grain sorghum or maize in fallow plots. Pigeon pea and grain sorghum had more C accumulation than cowpea, sunn hemp and double-cropped soybean. Pigeon pea and cowpea had more N uptake than sunn hemp and the double-cropped grain crops. Fallow with N fertilizer application produced significantly greater N2O emissions than all the cover crops systems. Nitrous oxide emissions were relatively similar in the various cover crop systems and fallow with 0 kg N ha−1. Grain yield of sorghum and maize in all the cover crop and double cropped soybean systems was similar to that in the fallow with 45 kg N ha−1. Both grain sorghum and maize in the double-cropped soybean system and fallow with 90 kg N ha−1 or 135 kg N ha−1 gave profitable economic net returns over the years. The double-cropped grain sorghum system increased aggregate-associated C and whole soil total C, and all the cover crop and the double-cropped soybean systems increased aggregate-associated N and soil N pools. Inclusion of leguminous cover crops without N fertilizer application reduced N2O emissions and provided additional C accumulation and N uptake, contributing to increased grain yield of the following cereal grain crop.

Author : Rickie Lee Holness
Publisher :
Page : 152 pages
File Size : 42,2 MB
Release : 2004
Category : Broccoli
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Studies the feasibility of supplementing nitrogen (N) needs of lettuce and broccoli with a cover crop under greenhouse conditions. Quantifies the N contribution of crimson clover and rye bi-culture to spring lettuce and broccoli. Attempts to better understand how cover crop influences soil N dynamics in short duration cropping systems. Determines the effects of different rates of fertilizer, cover crops, and fertilizer cover crops combination on spring broccoli and lettuce yields.

Author : Alexander John Hewitt
Publisher :
Page : 0 pages
File Size : 17,38 MB
Release : 2022
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Winter annual weeds can delay soil warming, inhibit planting operations, and compete for water and nutrients resulting in yield loss of spring planted cash crop. Understanding the timing and extent of weed emergence in different cropping systems is important to producers to be able to predict occurrence and to better manage weeds. The first objective of this research was to model the emergence of winter annual weed species in two different cropping systems based on the accumulation of thermal time. Results show that winter annual weed species composition and emergence timing can vary significantly between locations and are highly site-specific. Certain weeds such as henbit had predictable and consistent emergence timings across years in a no-tillage system in eastern Kansas but was more variable in southeast Kansas. This information can be used by farmers for weed management decisions, such as timing of control methods. The use of cover crop monocultures and mixes were evaluated for their physical and chemical weed suppressive capabilities. The second objective was to assess the levels of physical weed suppression by each cover crop treatment through weed biomass and weed density at the time of cover crop harvest. Cover crop monocultures and mixes composed entirely or mostly of aggressive grass species were found to be the most weed suppressive due to their high biomass accumulation. Certain varieties of cereal rye, annual ryegrass, winter oat, and mixes containing oat and ryegrass were found to be the highest biomass producers. Overall, cover crops provided superior weed control relative to a fallow with herbicide treatment that had no residual activity. Fertility regimes can impact cover crop biomass production and influence their allelopathic potential. The third objective was to investigate the role of nitrogen and sulfur fertilizers on cover crop weed suppression through allelopathy by conducting a weed seed germination bioassay. The results indicate that higher amounts of cover crop residues can potentially result in greater levels of weed suppression through inhibition of seed germination. Increasing soil fertility may decrease the allelopathic potential of cover crops, but can increase their biomass production, still resulting in adequate weed control.