• Authors:
    • Ferguson, R. B.
    • Liska, A. J.
    • Wortmann, C. S.
    • Lyon, D. J.
    • Klein, R. N.
    • Dweikat, I.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 1
  • Year: 2010
  • Summary: Sweet sorghum [SS; Sorghum bicolor (L.) Moench] is a potential biofuel crop for the Great Plains. Sweet sorghum was compared with corn [ Zea mays (L.)] and grain sorghum for potential ethanol yield, energy use efficiency, and greenhouse gas (GHG) emissions at seven dryland site-years in Nebraska. Seasonal rainfall ranged from approximately 340 to 660 mm. Soils were deep with medium texture at all site-years. The effects of seeding rate, N rate, and cultivar on SS performance were evaluated. Sweet sorghum sugar yield was not affected by seeding rate and N application at six of seven site-years, but yield was increased by 19% at one site-year. Calculated ethanol yield and net energy yield were 33 and 21% more, respectively, with the grain crops compared with SS, but mean net energy yield of an earlier-maturing SS cultivar was comparable with the grain crops. The mean ratio of energy produced in ethanol per total energy invested was 23% less for grain crops compared with SS. Mean life cycle GHG emissions were 53% and 66 to 69% less compared with gasoline for SS and grain crops, respectively. Very efficient use of the ethanol coproducts was assumed for the grain crops while SS bagasse was assumed to be returned to the field. At least one SS cultivar is competitive with grain crops for some biofuel criteria, but SS is not competitive with grain crops for total or net liquid transportation fuel produced per hectare.
  • Authors:
    • Bagwan, N.
  • Source: International Journal of Plant Protection
  • Volume: 3
  • Issue: 2
  • Year: 2010
  • Summary: Crop root exudates of 20 crops like groundnut, soybean, pigeonpea, green gram, black gram, chickpea, pea, cowpea, mustard, cotton, castor, sunflower, safflower, sesamum, sorghum, pearl millet, maize, wheat, onion, and garlic were used in this study. Large variations of inhibitory effect of root exudates on S. rolfsii were observed. Low concentrations of root exudates (5% and 10%) had no effect on inhibition of mycelial growth and germination of sclerotia while, at high concentration (20%) inhibited the mycelial growth and germination of sclerotia. Mycelial growth, dry mycelium weight and sclerotial germination were recorded lowest in root exudates of sunflower, maize, pearl millet, sorghum, safflower, garlic, and onion. Mycelial growth, dry mycelium weight and sclerotial germination was recorded highest in root exudates of soybean, groundnut, green gram, black gram, pigeonpea, chickpea, pea and cowpea. It was observed that the root exudates of maize, sunflower and pearl millet showed a highest percentage of inhibition of mycelial growth and sclerotial germination. Another interesting of thing was observed that root exudates of groundnut, soybean and pea stimulate the mycelial growth and germination of sclerotia as compared to control. The results of this study suggested that the intercropping or crop rotation of safflower, maize, pearl millet, sorghum, sunflower, garlic, and onion with groundnut may be useful for the management of stem rot of groundnut and also for reduction of soil population of S. rolfsii in groundnut field. Similarly intercropping or crop rotation of soybean, green gram, black gram, chickpea, pea and cowpea with groundnut should be avoided. Based on these findings, it is hypothesized that root exudates of some crops contain antifungal compounds, while other stimulate the growth of fungal pathogens. Cultivation of safflower, maize, pearl millet and sorghum with groundnut could lead to a reduction in the occurrence of stem rot disease, especially when chemical control is not effective and economically costly. However, further investigation is necessary for isolation and identification of antifungal compounds in root exudates related to host-pathogen interaction.
  • Authors:
    • Yaduraju, N. T.
    • Das, T. K.
    • Tadesse, B.
  • Source: Weed Biology and Management
  • Volume: 10
  • Issue: 3
  • Year: 2010
  • Summary: Parthenium is widely distributed across the uncropped areas of the tropics. It has slowly encroached into many crops and causes considerable yield loss. It heavily infests sorghum, which is widely cultivated by the resource-poor farmers in Africa and Asia. Its interference and management in sorghum in these cropping systems is not well understood. Therefore, this experiment was undertaken to determine the appropriate parthenium management techniques to use in sorghum crops. All the studied weeds, in combination with parthenium, offered greater competition to sorghum than parthenium alone. Similarly, under a composite stand of weeds, parthenium was inferior in competitiveness to the other weeds until 60 days after sowing (DAS); by 90 DAS, it could accumulate a higher dry weight due to its consistent growth. A pre-emergence treatment of atrazine (0.75 kg ha -1) with wheat straw mulch (5.0 t ha -1) brought about a consistent and significant reduction in the parthenium growth and, consequently, increased the sorghum yield by 90.8%. Cowpea intercropping with and without pendimethalin (1.0 kg ha -1) as a pre-emergence treatment could not control parthenium between 0 and 60 DAS, but could reduce the parthenium growth during the later period of 60-90 DAS, which resulted in a significant increase in sorghum growth. These intercropping treatments increased the sorghum grain yield by 156.2% and 142.4%, respectively, over the unweeded control and by 18.5% and 12.1%, respectively, over the weed-free control. These treatments also promoted a higher uptake of N, P, and K by the sorghum crop. Thus, cowpea intercropping was the most effective method for parthenium management vis-a-vis sorghum yield improvement, followed by cowpea intercropping with pendimethalin and then by atrazine as a pre-emergence treatment with wheat straw mulch.
  • Authors:
    • Elliott, N.
    • Giles, K.
    • Phoofolo, M.
  • Source: Environmental Entolomology
  • Volume: 39
  • Issue: 3
  • Year: 2010
  • Summary: Creating conditions that enhance the abundance of resident populations of natural enemies in agroecosystems is considered critical to the efficiency of biological control of insect pests. We conducted a study to determine the potential of relay-intercropping for enhancing the abundance of aphidophagous lady beetles in sorghum. A relay-intercropping system consisting of alfalfa, winter wheat, and cotton as intercrops and sorghum as a main crop was compared with sorghum monoculture plots at two study sites in OK from 2003 to 2006. Lady beetles and aphids were sampled throughout the season using sticky traps and field counts on individual sorghum plants. Results from sticky traps and field counts show that differences in abundance and species composition of lady beetles between intercropped and monoculture sorghum were not statistically different during each year of study. Also, the lady beetle-greenbug ratios in relay-intercropped and monoculture plots were not significantly different. Lack of significant effects of relay-intercropping in our study may have been attributable to the confounding effects of spatial and temporal scale and the low number of aphids and other alternative prey in the intercrops compared with high incidence of corn leaf aphids in sorghum early in the season.
  • Authors:
    • Mitchell, J. P.
    • Summers, C. G.
    • Stapleton, J. J.
    • Prather, T. S.
  • Source: PHYTOPARASITICA
  • Volume: 38
  • Issue: 1
  • Year: 2010
  • Summary: Experiments were conducted in laboratory bioreactors and in field plots to test effects of certain cultivated members of the grass family (Poaceae=Gramineae), including wheat ( Triticum aestivum cv. Yolo), barley ( Hordeum vulgare cv. UC337), oats ( Avena sativa cv. Montezuma), triticale ( X Triticosecale), and a sorghum-sudangrass hybrid ( Sorghum bicolor * S. sudanense="sudex", cv. Green Grazer V) for soil disinfestation potential. Soilborne pest organisms tested for effects on survival and activity included the phytopathogens Sclerotium rolfsii, Pythium ultimum and Meloidogyne incognita, and a variety of weed taxa. Following soil amendment, bioreactors were incubated for 7 days at ambient (23°C) or elevated, but sublethal (38°C day/27°C night), soil heating regimens. Addition of each of the poaceous amendments to soil at 23°C resulted in inconsistently reduced tomato root galling (49-97%) by M. incognita, or reduced recovery of S. rolfsii and P. ultimum (0-100%) fungi in soil, after 7 days' incubation ( P≤0.05). When the organisms were exposed to the poaceous soil amendments at the 38°/27° temperature regimen, nematode galling and recovery of active fungi were consistently and significantly reduced by 98-100%. These results demonstrated feasibility of soil disinfestation ("biofumigation") by activity of poaceous amendments, further aided by combining plant residues with soil heating (e.g. solarization). Results from three field experiments with sudex cover crops, conducted throughout the growing season, demonstrated biocidal activity on a range of weedy plants, including Amaranthus retroflexus, Calandrinia ciliata, Cerastium arvense, Digitaria sanguinalis, Echinochloa crus-galli and Poa annua. Both shoots and roots of sudex provided allelopathic weed biomass reductions of 35-100%, and for at least 106 days after shredding. Deleterious activity of shredded residues incorporated in soil was less persistent. These properties in poaceous crops can be useful for soil disinfestation; however, harmful phytotoxicity to subsequent crops may also result. In order to take full advantage of these low-input measures for controlling soilborne diseases and pests, further understanding of their properties must be gained, and user guidelines developed.
  • Authors:
    • Chotte, J.
    • Djigal, D.
    • Sall, S.
    • Pablo, A.
    • Saj, S.
    • Villenave, C.
    • Bonzi, M.
  • Source: Biology and Fertility of Soils
  • Volume: 46
  • Issue: 7
  • Year: 2010
  • Summary: Soil degradation has led crop yield to decline in many Sahelian countries and is a fundamental agricultural and economical threat for local populations. In Saria, Burkina Faso, long-term experiments are being performed to find efficient soil management practices that could improve soil fertility. A randomized block experiment comprising organic amendment (unamended control, straw at 8.3 t ha -1, manure at 10 t ha -1) coupled with mineral fertilization (no urea, urea at 60 kg ha -1) was started in 1980 with a continuous sorghum ( Sorghum bicolor) cropping system. Twenty-six years after the settlement of the treatments, we compared their effects on nematode populations, community structure, and ecological indices, as well as soil physical and chemical properties at three stages of sorghum's cropping cycle. The addition of manure led to significantly higher soil C, N, and P content and produced a higher sorghum grain yield in comparison to unamended or straw-amended soils. The number of plant-parasitic nematodes (mainly Pratylenchus and Tylenchorhynchus) was significantly higher in plots fertilized with manure in comparison to unamended or straw-amended plots. They were also significantly more abundant when urea was added. Mineral nitrogen fertilization had little impact on free-living nematodes, regardless of S. bicolor development stage, whereas organic amendment significantly raised the abundance of bacterivorous and fungivorous nematodes. Moreover, microphagous nematodes were significantly more numerous in plots amended with straw than with manure. Our results show that, on the long-term, only manure amendment seemed able both to store C and nutrients whereas both manure and straw led to greater microphagous nematode communities.
  • Authors:
    • Haar, M.
    • Lindquist, J.
    • Wortman, S.
    • Francis, C.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 25
  • Issue: 4
  • Year: 2010
  • Summary: While weed management is consistently a top priority among farmers, there is also growing concern for the conservation of biodiversity. Maintaining diverse weed communities below bioeconomic thresholds may provide ecosystem services for the crop and the surrounding ecosystem. This study was conducted to determine if weed diversity, density and biomass differ within and among organic and conventional crop rotations. In 2007 and 2008, we sampled weed communities in four long-term crop rotations near Mead, Nebraska using seedbank analyses (elutriation and greenhouse emergence) and above-ground biomass sampling. Two conventional crop rotations consisted of a corn ( Zea mays) or sorghum ( Sorghum bicolor)-soybean ( Glycine max)-sorghum or corn-soybean sequence and a diversified corn or sorghum-sorghum or corn-soybean-wheat ( Triticum aestivum) sequence. Two organic rotations consisted of an animal manure-based soybean-corn or sorghum-soybean-wheat sequence and a green manure-based alfalfa ( Medicago sativa)-alfalfa-corn or sorghum-wheat sequence. Species diversity of the weed seedbank and the above-ground weed community, as determined by the Shannon diversity index, were greatest in the organic green manure rotation. Averaged across all sampling methods and years, the weed diversity index of the organic green manure rotation was 1.07, followed by the organic animal manure (0.78), diversified conventional (0.76) and conventional (0.66) rotations. The broadleaf weed seedbank density in the tillage layer of the organic animal manure rotation was 1.4*, 3.1* and 5.1* greater than the organic green manure, diversified conventional and conventional rotations, respectively. The grass weed seedbank density in the tillage layer of the organic green manure rotation was 2.0*, 6.1* and 6.4* greater than the organic animal manure, diversified conventional and conventional rotations, respectively. The above-ground weed biomass was generally greatest in the organic rotations. The broadleaf weed biomass in sorghum and wheat did not differ between organic and conventional rotations (CRs), but grass weed biomass was greater in organic compared to CRs for all crops. The above-ground weed biomass did not differ within CRs, and within organic rotations the grass weed biomass was generally greatest in the organic green manure rotation. The weed seedbank and above-ground weed communities that have accumulated in these rotations throughout the experiment suggest a need for greater management in long-term organic rotations that primarily include annual crops. However, results suggest that including a perennial forage crop in organic rotations may reduce broadleaf weed seedbank populations and increase weed diversity.
  • Authors:
    • Prasad, V.
    • Staggenborg, S.
    • Assefa, Y.
  • Source: Crop Management
  • Issue: November
  • Year: 2010
  • Summary: Because sorghum is a drought-tolerant crop, it is often preferred by producers in cases of expected water stress. The objectives of this review were to summarize the water requirements, effect of water stress, and hybrid variation in drought tolerance of grain sorghum, and to suggest possible solutions that could help narrow the gap between potential and actual dryland sorghum yield. We reviewed more than 70 reports in peer-reviewed journals, extension publications, books, and websites. Grain sorghum tolerates and avoids drought more than many other cereal crops, but the drought response of sorghum does not come without a yield loss. Water stress at the vegetative stage alone can reduce yield more than 36%, and water stress at the reproductive stage can reduce yield more than 55%. Eighty percent of sorghum production in the world is under dryland conditions. We deduced that by focusing on techniques that can improve water availability in sorghum growing season alone, we can double the current dryland sorghum yield with the existing genetic potential. Results of this review suggest the existence of genotypic variation in drought tolerance among sorghum hybrids due to possible physiological differences or vice versa. We concluded by presenting possible management options to reduce the effects of water stress in dryland conditions and suggesting possible areas of research.
  • Authors:
    • Franti, T. G.
    • Drijber, R. A.
    • Wortmann, C. S.
  • Source: Agronomy Journal
  • Volume: 102
  • Issue: 4
  • Year: 2010
  • Summary: Continuous no-till (NT) can be beneficial relative to tillage with fewer field operations, reduced erosion, and surface soil improvement. Field research was conducted at two locations for 5 yr in eastern Nebraska to test the hypotheses that one-time tillage of NT can result in increased grain yield, reduced stratification of soil properties persisting for at least 5 yr, a net gain in soil organic carbon (SOC), and a restoration of the soil microbial community to NT composition. Stratification of soil test P, SOC, and bulk density was similar for all tillage treatments at 5 yr after tillage. Water stable soil aggregates (WSA) were not affected by tillage treatments except that there was more soil as macroaggregates at one location in the 5- to 10-cm depth with moldboard plow tillage (MP) compared with NT. Tillage treatments had no effect on SOC mass in the 0- to 30-cm depth. Soil microbial biomass was greater at the 0- to 5-cm compared with the 5- to 10-cm depth. Biomass of bacteria, actinomycetes, and arbuscular mycorrhizal fungi was greater with NT compared with one-time MP at one location but not affected by the one-time tillage at the other location. Microbial community structure differed among tillage treatments at the 0- to 5-cm depth at one location but not at the other location. Grain yield generally was not affected by tillage treatment. One-time tillage of NT can be done without measureable effects on yield or soil properties.
  • Authors:
    • Radford, B. J.
    • Thornton, C. M.
    • Huth, N. I.
    • Thorburn, P. J.
  • Source: Agriculture, Ecosystems & Environment
  • Volume: 136
  • Issue: 3-4
  • Year: 2010