Sudangrass Sorghum Research Articles

Development of SSR Markers Linked to Low Hydrocyanic Acid Content in Sorghum-Sudan Grass Hybrid Based on BSA Method.

Sorghum-Sudan grass hybrid containing high hydrocyanic acid content can cause hydrocyanic acid poisoning to the livestock and limit the popularization of this forage crop. Molecular markers associated with low hydrocyanic acid content can speed up the process of identification of genotypes with low hydrocyanic acid content. In the present study, 11 polymorphic SSR primers were screened and used for bulked segregant analysis and single marker analysis. Three SSR markers Xtxp7230, Xtxp7375 and Bnlg667960 associated with low hydrocyanic acid content were rapidly identified by BSA. In single marker analysis, six markers Xtxp7230, Xtxp7375, Bnlg667960, Xtxp67-11, Xtxp295-7 and Xtxp12-9 were linked to low hydrocyanic acid content, which explained the proportion of phenotypic variation from 7.6 % to 41.2 %. The markers identified by BSA were also verified by single marker analysis. The three SSR marker bands were then cloned and sequenced for sequence homology analysis in NCBI. It is the first report on the development of molecular markers associated with low hydrocyanic acid content in sorghum- Sudan grass hybrid. These markers will be useful for genetic improvement of low hydrocyanic acid sorghum-Sudan grass hybrid by marker-assisted breeding.

Propagation technique of arbuscular mycorrhizal fungi isolated from coastal reclamation land

Arbuscular mycorrhizal fungi (AMF) are well known for their plant growth promoting potential and stress tolerance ability. AMF promotes plant growth even at adverse environmental conditions and improve plant nutrient uptake. This study aimed to propagate AMF using a single spore inoculation technique. Soil samples were collected from salt affected Saemangeum reclaimed land. Collected soil samples were subjected to soil analysis. In the single spore inoculation method, sorghum sudangrass (Sorghum bicolor L.) was inoculated with a single spore. Among the 150 inoculants, six spores were able to germinate in vitro. Geminated spores were transferred to 1 kg pots containing sterilized field soil. After 120 days, the contents were mixed and transferred to 2.5 kg pots and maintained for another 120 days. After 240 days, spore count and colonization were checked. The propagated spores were identified using nested PCR followed by sequencing. The 18S rDNA sequencing of spores revealed that the spores belonged to Gigaspora margarita and Claroideoglomus lamellosum. Among the 6 inoculants, Claroideoglomus lamellosum S-11 (391 spore per 100 g of soil) had the highest spore count followed by Gigaspora margarita S-23 (235 spore per 100 g of soil). Slide method allowed visual monitoring of spore germination in vitro as well as being able to mass produce pure cultures of AMF for bio-inoculation purposes.

The effects of phosphorus addition on phytoavailability of zinc by diffusive gradientsin thin films (DGT)

Diffusive gradients in thin films (DGT) have been used for the assessment of Zn phytoavailability. Phosphorus is of particular interest in soils having Zn toxicity because of the Zn-P interaction. A greenhouse study was carried out to assess the influence of different P rates on the Zn phytoavailability to sorghum-Sudan grass (Sorghum vulgare var. Sudanese) in soil systems by DGT. Soil was amended with ZnSO4 at 0, 150, 300, 600, and 1200 mg Zn kg-1 in order to create various levels of Zn phytoavailability. Phosphorus was applied to soil at 0, 100, and 200 mg P kg-1 as KH2PO4. Plant nutrients were added as Hoagland's solution. In general, plant tissue Zn concentrations were elevated by increasing Zn concentration in soils, and they decreased by increasing P concentrations. However, this reduction was not found in C-DGT results. In other words, DGT did not predict the effects of P additions compared to Zn. P application decreased plant Zn concentrations and increased plant biomass yields. The highest relative yield in shoot tissue was with P200 × Zn150 treatment, while the lowest one was with P0 × Zn1200 treatment. In general, increasing P concentrations in the soil increased shoot yields relative to control, while increasing Zn concentrations decreased the relative shoot yields where no P was added. P addition might be an alternative strategy for remediation of Zn contaminated soil, since addition of P decreased Zn phytoavailability and enhanced plant growth.

Response of four spring-seeded cover crops to residues of selected herbicides.

Yu, L., Van Eerd, L. L., O'Halloran, I., Sikkema, P. H. and Robinson, D. E. 2015. Response of four spring-seeded cover crops to residues of selected herbicides. Can. J. Plant Sci. 95: 303-313. Although herbicide labels provide crop rotation restrictions, information is limited on the influence of herbicide residues on cover crops. Field experiments were conducted in 2011/2012 and 2012/2013 in Ontario, Canada, to characterize the effects of soil residues of selected herbicides on establishment and growth of buckwheat (Fagopyrum esculentum Moench), annual ryegrass (Lolium multiflorum Lam.), sorghum sudangrass [Sorghum bicolor (L.) Moench×Sorghum sudanense (P.) Stapf], and spring wheat (Triticum aestivum L.) spring-seeded cover crops planted 1 yr after application. Imazethapyr (100 and 200 g ha-1) was applied pre-emergence (PRE) to processing peas (Pisum sativum L.), while S-metolachlor/atrazine plus mesotrione (2880+140 and 5760+280 g ha-1) and saflufenacil/dimethenamid-P (735 and 1470 g ha-1) were applied ...

Forage Performance and Soil Quality in Forage Systems under Organic Management in the Southeastern United States

Interest is increasing in organic forage production and sod‐based rotations in the southeastern United States, but research‐based information is limited. A replicated field study was established to evaluate productivity and soil quality changes in five organically‐managed forage systems over 2 yr. Systems included four regionally‐adapted perennial systems and one warm‐ and cool‐season annual rotation: (i) alfalfa (Medicago sativa L.), (ii) red clover (Trifolium pratense L.), (iii) alfalfa/orchardgrass (Dactylis glomerata L.), (iv) red clover/orchardgrass, and (v) an annual system of wheat (Triticum aestivum L.)/crimson clover (T. incarnatum L.) followed by sorghum–sudangrass [Sorghum bicolor × S. bicolor var. sudanense (Piper) Stapf.]. Soil quality was compared to two annual vegetable systems, one managed organically and one managed conventionally. Poultry litter was applied to organically‐managed systems in September 2010 (9 Mg ha−1) and in September 2011 (4.5 Mg ha−1). Mean annual forage yield was greatest from wheat/crimson clover and sorghum–sudangrass (12.4 Mg ha−1 yr−1), intermediate from red clover, red clover/orchardgrass, and alfalfa/orchardgrass (10.0–10.3 Mg ha−1 yr−1), and least from alfalfa (7.6 Mg ha−1 yr−1). Soil C (total and particulate organic matter‐C) increased over 2 yr in all forage systems which were similar, and was in most cases significantly lower in vegetable systems. Soil N (total and particulate organic matter‐N) increased in all forage systems and was highest in alfalfa and treatments containing red clover, and lowest in vegetable systems. Results suggest these short‐term forage systems are viable options for regional organic rotations.

Improving Productivity of Managed Potato Cropping Systems in Eastern Canada: Crop Rotation and Nitrogen Source Effects

Strategies to improve sustainability are important in intensively managed potato (Solanum tuberosum L.) systems. This study has assessed rotation systems and N sources to mitigate potato yield and soil organic matter decline in Prince Edward Island (PEI), Canada. Three‐year potato rotation systems were initiated in 2006: continuous potato (CP); potato–barley (Hordeum vulgare L.) underseeded with red clover (Trifolium pratense L.)–red clover (PBR); and potato–barley–sorghum sudan grass ([Sorghum bicolor L.) used as green manure])/winter rape (Brassica napus subsp. rapifera) (PBSW); and potato–barley–canola ([Brassica napus susbsp. napus] used as green manure)/winter rape (PBCW). Three different N sources (mineral N fertilizer, liquid hog manure, and lobster flake) were applied in a split‐plot fashion during the potato phase. Potatoes were grown in 2006, 2009, 2012, and again in 2013 to evaluate residual effects. In 2012, total N or total C in the whole soil, in particulate organic matter or in the slurry fractions were not affected by N sources or rotation systems. The PBSW and PBCW rotations generated significantly higher potato yields in 2009 and 2013, whereas the CP rotation produced significantly lower potato yields in 2 of 4 yr. The addition of lobster flake suppressed yield compared with other N sources in 3 of 4 yr. The PBR rotation, which is common in PEI can increase nitrate losses over winter. Alternatively, the PBSW and PBCW rotations may represent a good substitute to the PBR rotation as they can increase potato yield while minimizing nitrate losses.

Response of four spring-seeded cover crops to residues of selected herbicides

Yu, L., Van Eerd, L. L., O'Halloran, I., Sikkema, P. H. and Robinson, D. E. 2015. Response of four spring-seeded cover crops to residues of selected herbicides. Can. J. Plant Sci. 95: 303–313. Although herbicide labels provide crop rotation restrictions, information is limited on the influence of herbicide residues on cover crops. Field experiments were conducted in 2011/2012 and 2012/2013 in Ontario, Canada, to characterize the effects of soil residues of selected herbicides on establishment and growth of buckwheat (Fagopyrum esculentum Moench), annual ryegrass (Lolium multiflorum Lam.), sorghum sudangrass [Sorghum bicolor (L.) Moench×Sorghum sudanense (P.) Stapf], and spring wheat (Triticum aestivum L.) spring-seeded cover crops planted 1 yr after application. Imazethapyr (100 and 200 g ha−1) was applied pre-emergence (PRE) to processing peas (Pisum sativum L.), while S-metolachlor/atrazine plus mesotrione (2880+140 and 5760+280 g ha−1) and saflufenacil/dimethenamid-P (735 and 1470 g ha−1) were applied PRE to sweet corn (Zea mays L.). Imazethapyr residues from 200 g ha−1 caused 75 and 48% visible injury in buckwheat and sorghum sudangrass, respectively. Plant light attenuation, shoot dry weight, and nitrate-nitrogen content were reduced up to 82, 64 and 67% in buckwheat, and 40, 11 and 24% in sorghum sudangrass, respectively, by residues from imazethapyr. S-metolachlor/atrazine plus mesotrione residues caused up to 53% visible injury to annual ryegrass and reduced plant light attenuation, shoot dry weight, and nitrate-nitrogen content by as much as 59, 48, and 55%, respectively. There were no observable adverse effects of visible injury, light attenuation, shoot dry weight, and nitrate-nitrogen content on spring wheat regardless of herbicide or rate. These results indicate that buckwheat and sorghum sudangrass should not be grown in the year following imazethapyr, and that annual ryegrass should not be grown in the year after application of S-metolachlor/atrazine plus mesotrione. However, no restrictions are needed for growing spring wheat following these herbicides.

Cover-Crop Species as Distinct Biotic Filters in Weed Community Assembly

Cover crops represent a potentially important biological filter during weed community assembly in agroecosystems. This filtering could be considered directional if different cover-crop species result in weed communities with predictably different species composition. We examined the following four questions related to the potential filtering effects of cover crops in a field experiment involving five cover crops grown in monoculture and mixture: (1) Do cover crops differ in their effect on weed community composition? (2) Is competition more intense between cover crops and weeds that are in the same family or functional group? (3) Is competition more intense across weed functional types in a cover-crop mixture compared with cover crops grown in monocultures? (4) Within a cover-crop mixture, is a higher seeding rate associated with more effective biotic filtering of the weed community? We found some evidence that cover crops differentially filtered weed communities and that at least some of these filtering effects were due to differential biomass production across cover-crop species. Monocultures of buckwheat and sorghum–sudangrass reduced the number of weed species relative to the no-cover-crop control by an average of 36 and 59% (buckwheat) and 25 and 40% (sorghum–sudangrass) in 2011 and 2012, respectively. We found little evidence that competition intensity was dependent upon the family or functional classification of the cover crop or weeds, or that cover-crop mixtures were stronger assembly filters than the most effective monocultures. Although our results do not suggest that annual cover crops exert strong directional filtering during weed community assembly, our methodological framework for detecting such effects could be applied to similar future studies that incorporate a greater number of cover-crop species and are conducted under a greater range of cover-cropping conditions.

Green Manure Crops for Management of Meloidogyne javanica and Pythium aphanidermatum

To determine the potential to suppress root-knot nematode Meloidogyne javanica, 10 genotypes of seven green manure species were evaluated in a greenhouse study. These species were: black hollyhock (Alcea rosea L.); canola (Brassica napus L.); cabbage (B. oleracea L.); French marigold (Tagetes patula L.), sorghum–sudangrass [Sorghum bicolor (L.) Moench nothosubsp. drummondii (Steud.) de Wet ex Davidse]; sunn hemp (Crotalaria juncea L.); and yellow mustard (Sinapis alba L.). Plants were inoculated with eggs of M. javanica and after 6 weeks, nematode eggs and reproduction factor (Rf = final egg population density/initial egg population density) were determined. Marigolds were non-hosts to M. javanica; other crop species that were poor hosts to M. javanica included canola cv. Dwarf Essex, sorghum–sudangrass cvs. Piper and Sordan 79, black hollyhock cv. Nigra, and sunn hemp. Based on low Rf, four groups of species were selected for further evaluation in the greenhouse to determine the response to both M. javanica and another crop pathogen, Pythium aphanidermatum. These four groups of green manure crops were: 1) seven marigold genotypes; 2) four Brassicaceae genotypes; 3) seven sorghum–sudangrass hybrids; and 4) four other species [black hollyhock, sunn hemp, elecampane (Inula helenium L.), and black-eyed Susan (Rudbeckia hirta L.)]. Plants were inoculated with a factorial combination of M. javanica and P. aphanidermatum (none, each alone, and in combination) and repeated four times in a split-plot experimental design (whole plots were factorial treatments and subplots were green manure crop genotypes). Six weeks after inoculation, plants were harvested and measured for fresh and dry weights of shoots and roots and Rf of M. javanica. Adverse effects of P. aphanidermatum were characterized by dead or dying roots and measured by reduced plant biomass. Negative synergistic effects were observed in several marigold and Brassicaceae genotypes, in which the combined effects of M. javanica and P. aphanidermatum reduced shoot and root growth more severely than either treatment alone. Marigold T. erecta cv. Orangeade, sorghum–sudangrass cvs. Graze-All, Piper, and Sordan 79, and sunn hemp appeared to be resistant to M. javanica and P. aphanidermatum, either alone or in combination. Based on results of greenhouse trials, eight green manure crops (yellow mustard cv. Ida Gold, French marigolds cvs. Nema-gone and Golden Guardian, sorghum–sudangrass cvs. Sordan 79 and Tastemaker, sunn hemp, unplanted plot, and a control plot with weed mat) were selected and grown for 3 months in a field trial in Pepeekeo, HI. Each treatment was replicated four times in a randomized complete block design. Shoot biomass was sampled at 1, 2, and 3 months after planting. Plant–parasitic nematodes were counted before planting and at 4 months after planting. Dry weight biomass averaged across three sampling dates was greatest for the two sorghum–sudangrass hybrids followed by those of two marigold cultivars that did not differ from them. No significant differences in populations of root-knot nematodes were found. Based on this field trial as well as greenhouse trials, marigold cultivars, sorghum–sudangrass hybrids, and sunn hemp appeared to be non-hosts or poor hosts to reniform (Rotylenchulus reniformis) as well as root-knot nematodes and well adapted to the environmental conditions found along the Hamakua Coast of the Hawaii Island.

Effects of Polymicrobial Bioinoculant on Yield, Quality and In Situ Digestibility of Sorghum Sudangrass in South Mississippi

Sorghum-Sudangrass was used in randomized complete block to test the effects of a bio-inoculant (BI) and nitrogen (N) application on dry matter (DM) yield determination and forage quality parameters (CP, TDN, ADF, NDF Ca, and P) and 72 h in situ digestibility at two harvest periods (H1 and H2). No effects of BI or N (P>0.05) were noted in any of the quality, yield or digestibility variables. An effect of H was noted in all quality, DM yield and digestibility data (P<0.01). Samples obtained at H1 were higher in quality (P<0.01), yielded less DM (P<0.01) and had greater in situ digestibility (P<0.01) A harvest x N interaction (P<0.05) existed for DM yield and digestibility. Moreover, a harvest x BI interaction existed (P<0.05), for digestibility.

Effect of Nitrogen and Phosphorus Fertilizer on Yield and Nutritional Quality of Jumbo Grass (Sorghum Grass x Sudan Grass)

Effect of Nitrogen and Phosphorus Fertilizer on Yield and Nutritional Quality of Jumbo Grass (Sorghum Grass x Sudan Grass)

Chemical fractionation of Cu, Zn, Cd, Cr, and Pb in sewage sludge amended soils at the end of 65-d sorghum-sudan grass growth

Heavy metals are potentially toxic to human life and the environment. Metal toxicity depends on chemical associations in soil. Understanding the chemical association of trace elements in soils amended with biosolids is very important since it determines their availability within rhizosphere and mobility beyond the rhizosphere. A sequential extraction method was used to determine the various chemical associations [labile (exchangeable + sorbed), organic, carbonates, and sulfides] of Cu, Zn, Cd, Cr, and Pb at the end of sorghum-sudan grass growth (65d) in Candler fine sand (pH = 6.8) and in Ogeechee loamy sand (pH = 5.2) amended with wastewater treatment sludge (WWTS) obtained from two different sources at application rates of 0, 24.7, 49.4, 98.8, and 148.2 Mg ha−1. Results of this study indicated that irrespective of the soil type, Cu, Cd, Cr, and Pb in the labile fractions (exchangeable + sorbed) were in the range of 0–3.0 mg kg−1 and the amount for Zn was in the range of 0.2–6.6 mg kg−1. Therefore, their availability to plants and mobility beyond rhizosphere would be substantially low unless further transformations occur from other fractions. Results also indicated that the presence of substantial amounts of trace elements studied were in sulfide (HNO3) fraction and in organic (NaOH) fraction irrespective of soil type with the exception of Pb which was mainly present as carbonate (Na2EDTA) fraction and the remaining Pb equally as sulfide (HNO3) and organic (NaOH) fractions. Furthermore, results indicated that Cd was mainly present as carbonate (Na2EDTA) fraction. Irrespective of soil type, source and rate of WWTS application, summation of quantities of various fractions of all the trace elements studied through sequential extraction procedure were 1 to 25 % lower than that of total recoverable quantities of these trace elements determined on acid digestion described by US EPA method 3050 B. It was further evident that growing sorghum sudan grass for 65-d following the application of WWTS either depleted labile fractions or shifted the solid phases containing the trace elements in soils away from those extractable with more severe reagents, such as 4M HNO3 to those extractable with milder reagents such as dilute NaOH and Na2EDTA.

Physical barriers for suppression of movement of adult stink bugs into cotton.

Nezara viridula (L.), Euschistus servus (Say), and Chinavia hilaris (Say) (Heteroptera: Pentatomidae) are economic pests of cotton in the southeastern USA. Because adult stink bugs exhibit edge-mediated dispersal at crop-to-crop interfaces as they colonize cotton, strategic placement of physical barriers at these interfaces could manage these pests. The objective of this study was to determine the effectiveness of a physical barrier, either synthetic or plant-based, at the peanut-to-cotton interface for suppressing stink bugs that would move to cotton. In 2012 and 2013, sorghum sudangrass (2.4 and 2.1 m high, respectively) was significantly taller than cotton (1.4 and 1.3 m high, respectively) which was taller than peanut (0.4 and 0.5 m high, respectively). Buckwheat (0.6 m high), planted only in 2012, was significantly taller than peanut, but shorter than cotton. For both years of the study, sorghum sudangrass and a 1.8-m-high polypropylene barrier wall effectively deterred dispersal of stink bugs into cotton. Because each of these barriers was taller than cotton, their success in protecting cotton likely was due to disruption of the flight of stink bugs from low-growing peanut into cotton. The shortest barrier wall (0.6-m-high) did not suppress stink bug dispersal into cotton probably because it was approximately the same height as peanut. In 2012, flowering buckwheat increased the efficacy of Trichopoda pennipes (F.) attacking N. viridula in cotton although it did not deter dispersal of stink bugs. In conclusion, a barrier at least as tall as cotton can effectively retard the entry of stink bug adults into cotton.

Effect of two additives on the fermentation, in vitro digestibility and aerobic security of Sorghum–sudangrass hybrid silages

AbstractTwo additives (Silo Guard (SG) and propionic acid (PA)) were tested for their effects on the quality and aerobic security of sorghum–sudangrass hybrid silages (JC‐1 and WC‐2). Two sorghum–sudangrass hybrid varieties were harvested for ensiling without additives (CK) or after the following treatments: SG at 0·5% of fresh forage or PA at 0·5% of fresh forage, with three replicates per treatment. The addition of SG and PA both affected the fermentation quality and chemical composition of the silages by lowering pH and NH3‐N/TN and increasing lactic acid, the LA/TA ratio, WSC and CP concentrations compared with the untreated silages. In vitro DM digestibility (IVDMD), in vitro NDF digestibility (IVNDFD) and in vitro CP digestibility (IVCPD) were increased by SG in the JC‐1 silages and WC‐2 silages. Both additives improved the aerobic stability of sorghum–sudangrass hybrid silages. Furthermore, the additives reduced the mould counts and the aflatoxin and zearalenone levels compared with the untreated silages following aerobic exposure. Therefore, ensiling two sorghum–sudangrass hybrid varieties resulted in high‐quality silages. The addition of SG and PA improved silage quality, in vitro digestibility and aerobic security.

Complete Utilization of Spent Coffee Grounds To Produce Biodiesel, Bio-Oil, and Biochar

This study presents the complete utilization of spent coffee grounds to produce biodiesel, bio-oil, and biochar. Lipids extracted from spent grounds were converted to biodiesel. The neat biodiesel and blended (B5 and B20) fuel properties were evaluated against ASTM and EN standards. Although neat biodiesel displayed high viscosity, moisture, sulfur, and poor oxidative stability, B5 and B20 met ASTM blend specifications. Slow pyrolysis of defatted coffee grounds was performed to generate bio-oil and biochar as valuable co-products. The effect of feedstock defatting was assessed through bio-oil analyses including elemental and functional group composition, compound identification, and molecular weight and boiling point distributions. Feedstock defatting reduced pyrolysis bio-oil yields, energy density, and aliphatic functionality, while increasing the number of low-boiling oxygenates. The high bio-oil heteroatom content will likely require upgrading. Additionally, biochar derived from spent and defatted grounds were analyzed for their physicochemical properties. Both biochars displayed similar surface area and elemental constituents. Application of biochar with fertilizer enhanced sorghum–sudangrass yields over 2-fold, indicating the potential of biochar as a soil amendment.

EFFECT OF THE SOWING TIME ON SOME BIO–PRODUCTIVE PARAMETERS OF ANNUAL SUMMER FORAGE MIXTURE

During the 2010–2012 periods in the Research Institute of Mountain Stockbreeding and Agriculture (RIMSA) in Troyan the effect of sowing time on some bio–productive parameters of the forage from annual summer mixture was performed. It was established that the most optimal time for sowing of annual summer mixture from sorghum–Sudan grass hybrid and horse bean grown under the foothill conditions of Central Balkan Mountains (Troyan region) is period from 1 to 10 of July. The received forage amounted to 2.20 t. ha green mass and 0.50 t. ha dry matter, which exceeded the later sowing periods from 7.55% (from 11 to 20 July) to 61.93% (from 1 to 10 August) and from 16.28 to 65.98%. There was a least weed infestation of mixture at last sowing period (from 1 to 10 August) and reached 3.03–3.85%.

Harvesting Downed Sorghum Sudangrass for Bioenergy Production

<abstract><title><italic>Abstract.</italic></title> The Southern United States has sufficient rainfall and appropriate climate to supply a significant portion of the energy needs of our nation. However, harvesting large biomass crops can be difficult given the intense rainfall and high winds that can accompany hurricanes and tropical depressions. These weather events can flatten bioenergy crops leaving them difficult to harvest. This study examined the potential of using existing hay equipment to harvest artificially flattened sorghum sudangrass, a potential bioenergy crop. Results showed that rotary-type windrowers were better able to harvest downed bioenergy crops than sickle-type windrowers. Additionally, no significant differences in harvested biomass was found in the direction the windrowers were operated in relation to the downed bioenergy crops, regardless of the harvesting direction. Our major conclusion was that completely flattened biomass resulted in the highest losses with more than 20% of the bioenergy crop remaining in the field after harvest. Even though existing agricultural equipment was capable of harvesting large amounts of bioenergy crops that have been downed, improvements may be necessary to increase their capability for handling this problematic scenario.

Smother Crop Mixtures for Canada Thistle (Cirsium arvense) Suppression in Organic Transition

Canada thistle poses a particular threat to organic producers in temperate agriculture due to its ability to reproduce through an extensive system of underground roots. The Canada thistle life cycle, growth, and development are seasonally affected, and exploiting this biology may be useful for weed management. The objective of this study was to evaluate smother crop mixtures, seeded at different times, for Canada thistle control. Field trials were established in 2009 and 2010 to evaluate the ability of smother crop mixtures to suppress Canada thistle growth and development. Canada thistle aboveground biomass was suppressed 50% in 2009 and 87% in 2010 by the sorghum–sudangrass mixture, averaged over planting times. The oat mixture suppressed annual weed biomass more than 58% in 2009 and 67% in 2010 in all planting dates. Percent cover of Canada thistle was affected by crop mixture in 2009 and 2010, with sorghum–sudangrass being the most suppressive. The sorghum–sudangrass mixture was more suppressive of Canada thistle, probably because it included soybean and sunflower, all high-biomass, competitive crops. Planting date affected smother crop suppression of Canada thistle growth, but the effect was not consistent between 2009 and 2010 due to differences in weather conditions.

Evaluation of wastewater treatment by-products as soil amendment: Growth of sorghum-sudan grass and trace elements concentrations

Wastewater treatment by-products (WTBP), such as sewage sludge (SS) may be used to enhance soil chemical, physical, and biological properties. These enhanced soil properties, in turn, could from its source of production to its site of application. These concerns may be mitigated by incineration of the SS to produce ash (SSA) and dissolved in water and stored in ponds as contribute to an increase in plant growth, production, mineral nutrition. Some SS is difficult to handle due to bad odor in its raw state and has large mass, hence expensive for transportation weathered SSA (WSSA). A greenhouse study was conducted using Candler fine sand CFS; (CFS; pH = 6.8) and Ogeechee loamy sand OLS; (pH = 5.2) with application of either 0, 24.7, 49.4, 98.8, or 148.2 Mg ha−1 as either SS, SSA, or WSSA to evaluate the biomass production and elemental composition responses of sorghum-sudan grass (Sorghum vulgaris var. Sudanese hitche). Shoot and root biomass were 2 to 3 fold greater in the soil amended with SS, than either SSA or WSSA. Concentrations of nutrient and trace elements in the shoots and roots increased with increasing rates of amendments. Application of these by-products up to 98.8 Mg ha−1 rate did not adversely affect growth or accumulation of trace elements in sorghum-sudan grass. Long-term field studies are recommended to investigate the potential leaching of various elements from the amended soils in addition to evaluation of plant growth and production responses to determine the acceptable rates of these by-products as amendments to agricultural soils.

Effect of Cover Crops on Aphids, Whiteflies, and Their Associated Natural Enemies in Organic Squash

Field experiments conducted in fall 2006 and 2007 evaluated the effects of monoculture and diculture cover crops on aphids, whiteflies and beneficials in organic squash. Insect populations were assessed using in situ and leaf disc counts, blue pan traps and unbaited yellow sticky traps. High levels of parasitoids and coccinellids were found in sorghum sudangrass (SSG) plots. The grass monoculture pearl millet had lower aphid populations than other treatments in 2006. The diculture sunnhemp/pearl millet treatment and the grass cover crop SSG had low whitefly populations in 2006. Therefore, the potential use of cover crops in organic agriculture is discussed.