Viable Weed Seeds Research Articles

Impact of Inoculums of Dry Batch Type Digesters on Resultant Compost Quality

Anaerobic digestion (AD) of municipal solid waste is significant in terms of energy and material recovery. The resultant sludge from AD is 100% organic and used as a fertiliser. The batch type biogas digesters established by National Engineering Research and Development Center in Dikowita in Wattala is one of the waste to energy projects established in the Western Province in Sri Lanka. Pre-sorted market and green waste in the area are used as the substrate while three cow dung layers (as top, middle and bottom) are applied as inoculums in the digesters. However, continuous supply of cow dung to the plant has become a challenge at present. Hence, the top cow dung layer is replaced by one month old previously generated sludge by the plant. After generating biogas, sludge is composted by means of windrow composting and sent to the market. The aim of the present study was to assess the quality of resultant compost due to the replacement of top inoculum layer by previously generated sludge. Nine laboratory digester tanks were set up and filled representing three treatments (with three replicates), in which Treatment-1, Treatment-2 and control had cow dung, previously generated sludge and organic waste respectively as top inoculum layer. After completion of AD process, resultant organic sludge samples were air dried. The resultant compost samples from digesters were sieved through 4.75 mm aperture (mesh no.4). Physical, chemical and biological parameters of resultant compost were analysed. The results were subjected to One-Way ANOVA followed by Tukey‟s test to see whether there were significant differences among three treatments and compared with Sri Lanka Standard 1246:2003. The results revealed that, the potassium contents (K2O%) in the samples were insufficient (<1.0%). The moisture of Treatment-1, Treatment-2 and Control were 44.42%, 47.34% and 51.83% respectively and significantly different from each other (p≤0.05; ANOVA). However, the colour, odour, particle size, sand content, pH, organic carbon, total nitrogen, phosphorous, C/N ratio and viable weed seeds were comparable to Sri Lanka Standard 1246:2003, suggesting that the resultant compost could be used as a soil amendment. Keywords: Biogas, Compost, Digestion, Waste, Cow dung layer

COMPOST FROM MARKET GARBAGE AND THE FEASIBILITY OF REDUCING THE TIME REQUIRED USING AERATION AND LOCALLY ACCLI MATIZEC' MICROORGANISMS

Solid waste collection and disposal is a major problem faced by all local authorities in SriLanka.The bulk of the waste, about 83%, is organic materials from vegetable markets andhouseholds. The predominant organic matter in waste makes itself ideal for biological treatmentprocess of waste management. The process of composting can be used to convert the waste to astable "humus like" product commonly known as compost, which could be used as a soilconditioner. This study was conducted using market garbage as the major ingredient, whichcontain 70% -90% moisture content and it was mainly directed to use low cost technology Themain objective was to reduce the production time and improve the quality of compost producedwith the use of inoculums and aerationSix different types of treatments were carried out during the experimental period. The windrowmethod was used to prepare compost under indoor environmental conditions. Vegetable garbage,air-dried grass clippings, saw dust, cow dung and coir dust were used as the raw organicmaterials. The initial total weight of waste was 250Kg (by wet weight). The experimental unitwas 1.5m x 1.5m x 1m (length x width x height). Two percentages of stabilized compost (2.5%,5%) were used as the inoculums. Hollow triangular wooden frame was used to facilitate aerationand mixing was carried out once a week.During the composting process physical changes (temperature, bulk density, changes indistribution of particle sizes), chemical changes (pH, organic matter, conductivity, C/N ratio) andbiological changes (C02 evolution, number of total coliform, invertebrates, weed seed viability,germination test) were determined to evaluate the em ctiveness of composting process.The results showed that composting of market garbage using stabilized compost as seeding andaeration helped to produce good compost at the end of two months. The high temperature stagecaused the destruction of the pathogenic organisms (number of coliforms), viability of weedseeds and fly larvae. Weed seed (Ameranthes seeds) lost their viability when exposed to highertemperature (&gt;60 DC) for about three days. The drop i_7lC/N ratio is rapid at the initial stages andslows down during maturation stage, whereas the temperature increased and then decreasedfaster. The decline in temperature and -e/N ratio are somewhat similar. In all cases, thecomposting occurred under alkaline conditions and finally it reached neutral values.The final weights were approximately half of their original weights and the volume shrieked to1/3 of their initial volume. The bioassay indicated the level of completeness of compostingprocess and T2, T3 and T4 showed 100% germination at the end of 2 months.When composting, high moisture, organic materials under tropical environmental conditions, itis necessary to add bulking material with frequent turning. When composting process is properlyoperated and managed final product can be obtained in 8 weeks.

On farm biogas production: A method to reduce GHG emissions and develop more sustainable livestock operations

We describe the potential contribution of on-farm biogas production to reducing greenhouse gas (GHG) emissions and other environmental impacts related to livestock operations. GHG are reduced by production of renewable energy as a substitute for fossil fuels via reduction of fugitive GHG emissions from stored and land applied manures, as well as by reduction in use of chemical fertilizers in crop production. Anaerobic digestion (AD) biotechnologies produce biogas at average rates of 0.30, 0.25 and 0.48L/g volatile solids from swine, bovine and poultry slurries, respectively. The biogas produced is of high quality with a CH4 concentration of 60–80%. AD may be an acceptable solution to management of P surplus by precipitating up to 25% of it in batch or semi-batch operated bioreactors, and by precipitating and concentrating up to 70% of bioreactor effluent P in long term storage bottom sludge. Effluents from AD are better balanced to meet crop needs than raw manure slurries, thereby reducing the need for supplementary chemical N and P fertilizers. Both capture of energy and reduced needs for chemical fertilizers will substantially decrease the C footprint of livestock food products. On-farm biogas production contributes to more sustainable livestock operations by substantially reducing other environmental impacts related to manure management. It reduces the risk of water pollution associated with animal manure slurries (i.e., eutrophication) by removing 0.80–0.90 of soluble chemical oxygen demand. In addition, some AD eliminate zoonotic pathogens and parasites in livestock manures. AD also improves human/farm cohabitation in rural regions by reducing odour emissions by 70–95%. This reduction allows more frequent and better timing of manure land application. Both timing of application and improved nutrient balance have the potential to increase nutrient uptake by crops and minimize nutrient losses to the environment. Reduction in the viability of weed seeds during AD reduces the need for herbicides and makes bioreactor effluent more acceptable to organic farmers. Inadequate regulatory polices and incentives are obstacles to widespread implementation of AD in developed and developing countries. However, adoption of AD is an alternative which could substantially reduce the C and environmental footprint of housed livestock operations.This article is part of the special issue entitled: Greenhouse Gases in Animal Agriculture – Finding a Balance between Food and Emissions, Guest Edited by T.A. McAllister, Section Guest Editors; K.A. Beauchemin, X. Hao, S. McGinn and Editor for Animal Feed Science and Technology, P.H. Robinson.

Soil steaming effects on weed seedling emergence under the influence of soil type, soil moisture, soil structure and heat duration

Soil steaming applied in bands is a new technology with the potential to radically lower the burden of hand-weeding intra-row weeds in non-herbicidal vegetable cropping. Preliminary studies with band-steaming have shown effective control of viable weed seeds when the maximum soil temperatures reach 60–80°C. This temperature range has a particular agronomic interest, and the present study aimed at investigating the influence of soil factors and heat duration on weed seed mortality of soil steaming targeting 60–80°C. Two soil types (sand versus sandy loam) and two moisture levels (moist versus dry) were studied in one experiment (expt) while two levels of structure of a sandy loam (coarse versus fine) were included in a second experiment. A third experiment was focussing on the significance of heat duration expressed as the speed of cooling-down after steaming had been stopped. Weed control efficacy was generally greater in sand than in sandy loam and soil irrigation further improved weed control. Steam application to the finely structured soil improved weed control efficacy relative to that obtained with the coarse soil of larger aggregate size. The rapidity of cooling from the maximum temperature did not affect the efficacy of the treatment on weed seed mortality. Based on these experiments, a maximum soil temperature of 80°C should ensure satisfactory weed control under moist soil conditions, especially if the soil is cultivated prior to steaming.

Survival of weed seeds subjected to sheep rumen digestion

Haidar MA, Gharib C &amp; Sleiman FT (2010). Survival of weed seeds subjected to sheep rumen digestion. Weed Research50, 467–471.SummaryAn experiment was conducted to examine the effect of sheep rumen digestion on the viability of the seeds of eight weed and two crop species common in Lebanon. Seed samples were put in small monofilament polyester bags and placed in the rumen of fistulated sheep for 1, 2, 3 and 4 days. The viability of the seeds 4 days after placement in the rumen was 85% for Cuscuta campestris, 76% for Amaranthus retroflexus, 31% for Convolvulus arvensis, 17% for Chenopodium album, 10% for Eleusine indica, and 1.3% for Setaria viridis, compared with the control. Seeds of Lolium multiflorum and Raphanus raphanistrum died 2 days after placement in the rumen, while seeds of Lens culinaris and Hordeum vulgare, which were tested for comparison, died 1 day after placement in the rumen. The seeds most tolerant to incubation were Cuscuta campestris and Amaranthus retroflexus, followed by Convolvulus arvensis, Chenopodium album and Eleusine indica. The results indicate that sheep could be an important vector for dispersing viable weed seeds, particularly hard‐coated seeds. Thus, sheep should be kept in pens for about 4 days before being released into new fields, to reduce the risk of weed infestation and spread.

Efeito do arejamento no processo de compostagem da fracção sólida do chorume de pecuária leiteira

Manure surpluses in dairy farms can be reduced by separation of the solid fraction from slurry whereas composting allows the stabilization of the organic matter of the solid fraction. The solid fraction can be exported to other farms with a high demand for organic amendments after composting because this turns cattle slurry solids into a uniform, easily handled, organically stable, without pathogens or viable weed seeds that can be land applied and marketed as a soil amendment. However, when 60% moisture content of solids is exceeded, and this is the situation for most separated slurry solids, oxygen movement is somewhat restricted. Therefore, the effect of turning the compost pile must be researched since it provides oxygen for the decomposition process. Dairy cattle slurry solids from two different farms located at the NW Portugal (Vila do Conde), with 70% and 78% moisture contents, were removed from the tank using an auger encased in a perforated stainless steel screen, allowing removal of excess water. Twelve pile treatments of 15 m3 of freshly separated solids were placed in bare soil. The effects of using straw as a framework and of turning with a tractor-mounted front-end loader were evaluated through chemical analysis on pile samples collected over a 15 week period. Thermophilic temperatures were achieved soon after separation for 70% moisture solids, but these temperatures were attained for 78% moisture solids only once mixed with straw, indicating that differences in bedding material affects the temperature and oxygen concentration during composting. Moreover, solids with initial 70% moisture had a faster rate of composting and took shorter time to reach maturity than solids with 78% moisture. Although chemical evolution based on parameters such as pH, electrical conductivity and C/N ratio provided substantial evidence that agronomical suitable compost can be obtained, future challenges include optimizing the process to minimize the loss of nitrogen in the form of ammonia gas, given that pH ranged from 8 to 9 throughout the compost process.

Perennial Crop Nurseries Treated with Methyl Bromide and Alternative Fumigants: Effects on Weed Seed Viability, Weed Densities, and Time Required for Hand Weeding

Data on the efficacy of alternative fumigants to methyl bromide for weed control in perennial crop nurseries in California are needed because few herbicides are registered for this purpose. Field studies were conducted from 2003 to 2006 in four commercial perennial crop nurseries in California. Treatments included a nonfumigated control; methyl bromide (98%) (MeBr) with high-density polyethylene (HDPE) film; iodomethane (50%) + chloropicrin (50%) with HDPE film; 1,3dichloropropene (1,3-D) with HDPE film; 1,3-D (61%) + chloropicrin (35%) with HDPE film; 1,3-D (62%) + chloropicrin (35%) subsurface drip; and 1,3-D (61%) + chloropicrin (35%) with virtually impermeable film (VIF). All the fumigants reduced the seed viability of common purslane, johnsongrass, and tall morningglory but were not as effective on little mallow and field bindweed. Although total weed densities and the level of control provided by each fumigant differed between locations, weed density was generally reduced by all the fumigation treatments, compared to the nonfumigated control. At three locations, alternative fumigation treatments usually resulted in hand-weeding time similar to MeBr. Reductions in weed seed viability, weed emergence, and weed densities suggest that these alternative fumigants will provide weed control similar to MeBr in perennial nurseries. Nomenclature: 1,3-dichloropropene; chloropicrin (trichloronitromethane); iodomethane; methyl bromide; common purslane, Portulaca oleracea L. POROL; field bindweed, Convolvulus arvensis L. CONAR; little mallow, Malva parviflora L. MALPA; johnsongrass, Sorghum halepense (L.) Pers. SORHA; tall morningglory, Ipomoea purpurea (L.) Roth PHBPU.

Fresh Parboiled Rice Hulls Serve as an Alternative to Perlite in Greenhouse Crop Substrates

Ten substrates were formulated by blending perlite or parboiled fresh rice hulls (PFH) at 20%, 30%, 40%, 50%, or 60% (v/v) with sphagnum peat. After 6 weeks, NH4+ concentrations were not significantly different among substrates containing perlite and those containing equivalent amounts of PFH. Nitrate concentrations were significantly higher in the 40% perlite substrate than in the 40% PFH substrate, but there were no significant differences in NO3- concentrations among the remaining substrates containing equivalent amounts of PFH or perlite. When tomato (Lycopersicon esculentum Mill.) was grown in the substrates for 5 weeks, tissue N concentrations were not significantly different between equivalent perlite and PFH-containing substrates. Non-parboiled fresh rice hulls produced organically contained a higher number of viable weed seeds than non-parboiled fresh rice hulls produced conventionally. No weed seeds germinated in the PFH. `Better Boy' tomato, `Bonanza Yellow' marigold (Tagetes patula L. French M.), `Orbit Cardinal' geranium (Pelargonium ×hortorum L.H. Bailey), `Cooler Blush' vinca (Catharanthus roseus L.G. Don), `Dazzler Rose Star' impatiens (Impatiens walleriana Hook. f.), and `Bingo Azure' pansy (Viola ×wittrockiana Gams) were grown in sphagnum peat-based substrates containing perlite or PFH at 10%, 15%, 20%, 25%, 30%, 35%, or 40% (v/v). Dry root weights of vinca and geranium were not significantly different among plants grown in the substrates. Tomato plants grown in 10%, 15%, 25%, 30%, and 35% PFH had significantly higher dry root weights than those grown in equivalent perlite-containing substrates. Impatiens grown in 35% PFH had higher dry root weights than those grown in 35% perlite. Marigold grown in 20% perlite had higher dry root weights than those grown in 20% PFH. However, there were no significant differences in impatiens or marigold dry root weights among the remaining substrates containing equivalent amounts of PFH or perlite. Dry root weights of pansy grown in 10%, 20% 25%, 35%, and 40% perlite were not significantly different from those grown in equivalent PFH-containing substrates. Across substrates, root dry weights of impatiens, marigold, and pansy grown in perlite-containing substrates were not significantly different from those grown in PFH-containing substrates. No significant difference in dry shoot weights of vinca, geranium, impatiens, and marigold occurred between equivalent perlite and PFH-containing substrates. Tomato plants grown in 20% to 40% perlite had significantly higher dry shoot weights than those grown in equivalent PFH-containing substrates. However, dry shoot weights of tomato grown in 10% to 15% perlite were not significantly different from those grown in equivalent PFH-containing substrates. Dry shoot weights of pansy grown in 10%, 25%, 30%, 35%, and 40% perlite were not significantly different from those grown in equivalent PFH substrates.

Compost Recipe Development and Weed Seed Viability Evaluation with Cranberry Leaves

A small-pile demonstration study was conducted to evaluate the possibility of composting cranberry leaves on commercial cranberry farms in Southeastern Massachusetts. The recipe ratios tested were: 20:0:0 (cranberry leaves only), 10:10:2, and 10:10:1 (leaves:horse manure and bedding:fish hydrolysate). Both mixed recipes generated thermophilic temperatures (between 43-66°C for at least 20 d), conditions known to destroy many plant pathogens and weed seeds. Analysis of leaf samples indicated that all three recipes were more acidic than most other types of compost (values below pH 6). Nitrogen levels were at or below the low-end (0.45-0.75% N) of the typical level seen with most compost (1% N). The final C:N ratios (22:1 to 38:1) were within the acceptable range for many uses. The mixed piles attained thermophilic temperatures for sufficient duration to prevent germination of the seven species of weeds tested. Leaf residue levels for eight common cranberry pesticides were also determined. The insecticide, chlorpyrifos, and the metabolite of the herbicide dichlobenil, BAM (2,6-dichlorobenzamide), were detected at levels below food tolerance and slightly above the food tolerance threshold, respectively. These levels were within a range that would allow the pursuit of commercial development of the compost since ingestion is not an anticipated end-product use. The data from this preliminary demonstration study would suggest that the composted product would be acceptable for use on-farm as well as for distribution to other off-farm sites, but additional replicated research studies are warranted.

TWO METHODS OF COMPOSTING GIN TRASH

The ginning of cotton (Gossypium hirsutum L.) results in the accumulation of approximately 90 kg of gin trash per bale of cotton ginned. In the past, disposal of raw gin trash was by burning, land application and feeding to livestock, but problems with clean air standards, weed seeds and diseases, and chemical residues, respectively, make each of these methods unacceptable. Composting the gin trash would alleviate certain problems associated with land application on farm fields. Experiments were conducted to investigate windrow composting. A split plot experiment with five reps was initiated to evaluate turning times, nitrogen (N) fertilization and bacterial inoculation. Composite samples were collected and analyzed for nutrients and selected chemicals. Another experiment was established to compare timing and physical methods of turning windrows. The Lipsey®-gin-trash-composting system was investigated by sampling three compost piles at three different cotton gins. The chemical composition and weed seed germination were investigated. Results indicate that windrow composting does not solve the weed seed or plant disease problem; otherwise, the product was satisfactory. The Lipsey®-gin-trash-composting system resulted in a pile of material whose outside 0 to 15 cm depths contained viable weed seeds and disease organisms, but none survived below this exterior. This system resulted in an incomplete composting material with offensive odors.

Viability of Weed Seeds Following Manure Windrow Composting

Introduction of weed seeds is a concern when using animal manure as a nutrient source on croplands. The viability of weed seeds can be reduced through composting. Experiments were conducted in 1996 and 1997 to determine the effects of manure windrow composting on seed viability of eight weed species. Weed seeds were placed in nylon bags and buried at 25 and 75-cm within the composting windrows of dairy manure and beef cattle feedlot manure with or without water addition. After one turning a week later, the seeds of most weed species survived the composting conditions in the dairy cattle manure. Following the four to five month dairy manure composting process, all weed seeds lost viability except for 14% of the velvetleaf (Abutilon theophrasti) seeds. This occurred even though the temperature within the composting dairy manure windrow never reached 60°C, which is considered necessary for weed seed destruction. In the watered beef feedlot manure, all weed seeds lost viability after one turning. However, seeds of most species survived after the first turning of the unwatered beef feedlot manure. The temperature in the feedlot manure windrows with water addition was higher and stayed high longer than other manure windrows. Composting process that generates high temperature (≥60°C) can destroy seed viability after only one turning. When the composting materials are moist for most of the composting period, the viability of weed seeds can be reduced even though the critical temperature is not achieved possibly because of compost phytotoxins.

Effect of duration of heat exposure on upland weed seed viaility.

A study was conducted to determine the length of exposure to heat necessary to kill water-imbibing weed seeds at 55 and 60°C. The examination covered ten upland weed species: Solanum carolinense L., S. americanum Mill., Abutilon theophrasti Medic., Phytolacca americana L., Amaranthus spinosus L., A. patulus Bertoloni, Persicaria lapathifolia (L.) S. F. Gray, Panicum dichotomiflorum Michx, Echinochloa crus-galli (L.) Beauv. var. crus-galli and Digitaria ciliaris (Retz.) Koeler. All seeds of each species were killed by exposure to heat at 55°C for 72hr and at 60°C for 24hr except for those of Abutilon theophrasti (dormant seed rate 80%) which were killed by exposure for 120 and 30hr at the respective temeratures.These weed species fell into four groups, categorized by a combination of short-duration heat-tolerance (SDHT) and long-duration heat-tolerance (LDHT). SDHT was determined by the viability of weed seeds when treated at 60°C for 3hr, with low and high subcategories of tolerance. LDHT was detemined by the duration required to kill all the seeds at 1% level of significance when treated at 60°C, into three subcategories (low, medium and high tolerance). Persicaria lapathifolia, E. crus-galli, and D. ciliaris were low for both SDHT and LDHT (Group I), and Amaranthus spinosus and Panicum dichotomiflorum were low-SDHT and medium-LDHT (Group II). Solanum species, Phytolacca americana, and Amaranthus patulus were high-SDHT and medium-LDHT (Group III), while Abutilon theophrasti was low-SDHT and high-LDHT (Group IV). The viability of seeds at short-duration heat treatment for Group I, II and IV was low, but the durations required to kill all seeds were different among the groups. Group III consisted of species for which the viability of seeds at short-duration heat treatment was high, and the fatal duration was medium.For Abutilon teophrasti which required the longest duration of heat exposure to kill all seeds at each temperature, 95% confidence intervals of LD90 values were calculated using the probit method, and were 42 to 58 and 10 to 17hr at 55 and 60°C, respectively.

Duration of Composting of Yard Wastes Affects Both Physical and Chemical Characteristics of Compost and Plant Growth

Windrows of municipal yard and landscape waste at three commercial composting sites in California were sampled at ≈3-week intervals through 12 to 15 weeks of composting to observe changes in physiochemical and biological characteristics of importance to horticulture. Initial C, N, P, and K content averaged 30%, 1.3%, 0.20%, and 0.9%, respectively. Carbon concentration declined rapidly through the first 6 to 9 weeks, while N, P, and K remained relatively stable throughout the sampling period. Few viable weed seeds were found in any compost. A high level of phytotoxicity, as measured by a tomato (Lycopersicon esculentum Mill.) seed bioassay, was observed at only one site; overall, the degree of phytotoxicity declined with compost age. Short-term net N immobilization (in a 2-week aerobic incubation) was observed in nearly all samples, with an overall trend toward decreased immobilization with increased compost age. In a 16-week pot study in which fescue (Festuca arundinacea Shreb.) was grown in compost-amended soil, net N mineralization averaged only 2% to 3% of compost total N content. Neither composting site nor duration of composting significantly affected either N mineralization rate or fescue growth. Growth of vinca (Catharanthus roseus Don.) in a blend of 1 compost : 1 perlite increased with increasing compost age. Overall, at least 9 to 12 weeks of composting were required to minimize the undesirable characteristics of immature compost.

High‐temperature Effects on Germination and Viability of Weed Seeds in Soil

AbstractThe control of weeds by solar heating of the soil using transparent polyethylene (PE) sheets was studied in the field during the summers of 1994 and 1995. The maximum soil temperature under plastic cover at 5 cm depth averaged 53°C. At 5 cm soil depth, solarization increased temperature by about 9°C. In the non‐solarized soils, such high‐temperature days were fewer. A temperature of 55°C at 5 cm soil depths was recorded both in irrigated and non‐irrigated mulched soils. However, mulched soil recorded 70% of the treatment period compared with 43% in unirrigated and mulched soils. Lower depths of 10 and 15 cm did not attain a temperature 55°C or 60°C on any day during the experimental period.Solarization treatment with PE sheets significantly increased NO−3—N and NH+4—N in comparison with non‐solarized plots. While uncovered plots showed significant increase in available phosphorus and marginally increased in potassium and electrical conductivity. Organic carbon content and pH did not vary under different treatments.PE mulching for 30 days significantly reduced the number of weed seeds, specifically Avena fatua L. and Phalaris minor Retz., while Trianthema monogyna Linn, and Asphodelus tenuifolius Cav. were not affected much in comparison with the former. Melilotus indica (L.) All, was not at all affected by the solarization treatment studied. The solarization reduction index (SRI) was calculated for each weed species studied and it was concluded that weeds having a low SRI can be controlled more effectively than weeds with high SRI values. The heating effect from solarization decreased significantly with soil depth. The 30 days’ soil solarization treatment in moist soil was more effective than the 10 and 20 days’ heating treatment in moist and dry soils for weed control.

The Effect of Temperature on the Viability Of Weed Seeds in Compost

In this study, the effect of different constant temperatures on the viability of weed seed contaminants of municipal composted waste was determined. Seeds of eight weed species were buried in moist compost in small recoverable packets. The seeds were subjected to three constant temperatures, typical of the composting process, removed after 3, 21 and 84 days and their germination and viability determined. At 55°C all of the recovered weed seeds failed to germinate and were found to be non-viable. At 35°C and 45°C an effect of incubation period was noticeable, and it was evident that there were significant differences between species in tolerance to temperature. The study showed that three days at 55°C was sufficient to destroy all the selected weed species. It was concluded that, among the species studied, seeds that survive the composting process do so as a result of localized “cool spots” caused by inefficient turning of the windrow. Alternatively wind blown species could be entering the outer parts of the windrow, immediately prior to packaging.

Viability of Weed Seeds in Feed Pellet Processing

Federal and state agencies in several western states now require the use of noxious weed-free or noxious weed seed-free forage to hinder the spread of noxious weeds. Forage can be certified as noxious weed-free through state administered programs. Processed feeds such as pellets or cubes made from noncertified hay and uncleaned grain are some of the forage products that may be potential sources of weed infestations. This study was conducted to determine levels of weed seed contamination in alfalfa hay/grain feed pellets manufactured with commercial-grade equipment. Seeds of whitetop [Cardaria draba (L.) Hand.], spotted knapweed (Centaurea maculosa Lam.), Canada thistle [Cirsium arvense (L.) Scop.], leafy spurge (Euphorbia esula L.), and common yellow sweetclover [Melilotus officinalis (L.) Lam.] were added in known quantities to alfalfa/grass mixed hay and to barley. The hay was ground in a hammermill through a screen with 7.9-mm diameter perforations, and the barley was ground to pass through a 2.4-mm screen. In a second experiment, uncertified 'Ladak 65' alfalfa (Medicago sativa L.) seeds were ground with alfalfa/grass mixed hay in a hammermill and extruded through a pellet die before being ground in another hammermill with barley grain followed by extrusion through a pellet die. The Montana Department of Agriculture collected pelleted feed from various manufacturers in the state during 1993 and 1994 to estimate potential weed contamination frequency. Grinding of weed seeds with alfalfa hay or barley grain reduced emergence by 98 to 100%. Grinding and pelleting reduced emergence of alfalfa seed by over 99%. Weed seedlings emerged from 11% of random feed pellet samples collected from Montana manufacturers. Rigorous processing such as occurs when manufacturing hay/grain pellets reduces the risk of disseminating weed seeds from pelleted feed.

The fallow period as a weed-break in shifting cultivation (tropical wet forests)

In the wet tropics weeds can grow all year round. In shifting cultivation systems the fallow period is used to restrain the development of weeds because they threaten the re-use of the land. Overhead shade suppresses the heliophytic weeds growing on the site and interrupts the continuous re-seeding of the field. This is the first phase of weed suppression. During the second phase, shade cover is maintained to allow the reduction of viable weed seeds in the soil. In the Taï farm system, Côte d'Ivoire, little weeding is carried out because optimum use is made of the natural fallow vegetation as a weed-break. The first phase took 6–12 months, the second 10 years. The shading out of weeds is cheap and effective yet demands much land. Those farm systems under the pressure of land shortage are likely to be infested by weeds. They suffer from weeds because shade-producing plants are eliminated from the system. Intensive use of the land is sometimes possible when shade plants are preserved (as stumps, tubers) during the period the field is covered by heliophytic crops, and are allowed to grow out afterwards.

The Viability of Seeds in Feed Pellets

Seed response to grinding in a hammer mill or extrusion through a pellet die was determined. Less than 1% of spotted knapweed, sulfur cinquefoil, timothy, and alfalfa seeds were intact after grinding to pass through a 1-mm screen. Intact seeds of all tested species except sulfur cinquefoil were able to germinate after grinding. Extruding unground alfalfa seed through a die to make hay pellets decreased viability 60 to 63%. After grinding and extrusion through a grain pellet die, 53% of intact alfalfa seeds in the pellets were viable. These data demonstrate that feed pellets can contain viable weed seeds.

The Effect of Farmyard Manure Anaerobic Treatment on Weed Seed Viability

ABSTRACT Weed encroachment is a serious problem of contemporary agriculture. Farmyard manure and other organic fertilizers can be major sources of weed seeds that get into the soil. One of the methods for eliminating weed seed germination is the technology of anaerobic treatment of the farmyard manure with a simultaneous production of biogas, the so called “Olomouc method”. Before anaerobic fermentation seeds of all 11 species under study (i.e. Tripleurospermum maritimum, Echinochloa crus-galli, Plantago major, Chenopodium album, Chenopodium strictum, Thlaspi arvense, Avena fatua, Rumex obtusifolius, Amaranthus retroflexus, Agropyron repens and Polygonum lapathifolium) manifested a high germination power. The seeds positioned in the lower layers of the fermentation unit (1,800 mm) lost their germination power after one month's treatment. In the sub-surface layers (400 mm) of the farmyard manure there was only a small proportion of viable seeds belonging to 4 species. The germination rate of Echinochloa crus-galli, Chenopodium album, Rumex obtusifolius and Amaranthus retroflexus was 36%, 9%, 19% and 4%, respectively.

Effect of Ensiling and Rumen Digestion by Cattle on Weed Seed Viability

Studies were conducted to determine the effect of ensiling and/or rumen digestion by cattle on the germination and viability of several common weed species. Seed survival of grass species subjected to ensiling and/or rumen digestion tended to be less than that of broadleaf species. Downy brome, foxtail barley, and barnyardgrass were nonviable after either ensiling for 8 weeks or rumen digestion for 24 h. Some green foxtail (17%) and wild oats (0 to 88%) seeds survived digestion in the rumen but were killed by the ensiling process. Varying percentages of seeds of kochia, redroot pigweed, common lambsquarters, wild buckwheat, round-leaved mallow, and field pennycress remained viable after ensiling (3 to 30%), rumen digestion (15 to 98%), and ensiling plus rumen digestion (2 to 19%). A time course study of rumen digestion indicated that loss of seed viability often was not a gradual process. With some species, there was an initial lag phase while degradation of the protective seed coat likely occurred, followed by a rapid decline in embryo viability. The diet fed to livestock appeared to affect viability losses caused by rumen digestion. Estimates of seed survival with varying rates of passage through the rumen due to differing ratios of grain to forage in the diet are presented.