Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry, Durban University of Technology, Durban, South Africa, 2015. / Fossil fuel reserves have been diminishing worldwide thus making them very scarce in the long term. These fuel sources and their by-products which are used commercially tend to produce large quantities of emissions. Some of them are believed to be toxic to flora and fauna. It is primarily for this reason that researchers worldwide have begun to seek out alternative sources of environmentally safe fuel. Biodiesel from algae is one of these sources that have been examined over the last few decades. Biodiesel has been produced from other plant-based material and waste oils in countries like America and Japan. However, the use of food based crops for biodiesel production has been challenged as it has an impact on food production on an international scale. Algae have only recently been investigated for their feasibility for biodiesel production on a large scale. The aim of this study was to investigate and develop technologies for biodiesel production from algae. The species of algae chosen were chlorella sp and scenedesmus sp., since they are indigeneous to Kwazulu Natal in South Africa. Samples were obtained from a local raceway pond and prepared for analysis. Drying protocols used freeze, oven and sun drying for initial preparation of the samples for analysis. Sun drying was the least energy intensive but most time consuming. At laboratory scale, oven drying was chosen as the best alternative. Lipid extraction methods investigated were the separating funnel method, the soxhlet method, microwave assisted extraction (MAE) and the expeller press. Thirteen solvents covering a range of polarities were used with the extraction methods to determine the efficiency of the solvent with these methods. Optimization of the MAE method was conducted using both the one factor at a time (OFAT) method and a design of experiment (DOE) statistical method. The shelf life of algal biomass was determined by ageing the samples for approximately three months. Direct and in-situ transesterification of lipid extracts to produce biodiesel was investigated using both acid and base catalysis. Qualitative and quantitative analyses were conducted using Fourier transform infra-red (FTIR) and gas chromatography (GC). Chemical and physical characterization of the biodiesel produced from the algal lipid extracts were compared to both local and international standard specifications for biodiesel. In terms of extraction efficiency, it was found that soxhlet and microwave assisted extraction methods were almost equally good. This was proved by the MAE method yielding an average of 10.0% lipids for chloroform, ethanol and hexane after 30 mL of solvent was used in an extraction time of 10 minutes, while the soxhlet method yielded 10.36% lipids using an extraction volume of 100 mL of solvent with an extraction time of 3 hours. Chloroform, ethanol and hexane were more efficient than the other ten solvents used. This was shown by these three solvents producing lipid quantities between 10% to 11% while all the other solvents produced lipid quantities between 2 and 10 %. The best extraction efficiency was achieved by the binary solvent mixture made up of chloroform and ethanol in a 1:1 ratio. Under the conditions optimized, this solvent ratio yielded a lipid content of 11.76%. The methods chosen and optimized for extraction are very efficient, but the actual cost of production of biodiesel need to be determined. Physical methods like the expeller press are not feasible for extraction of the type of biomass produced unless algae are pelletized to improve extraction. This will impact on the cost of producing biodiesel. The transesterification protocols investigated show that the base catalysis produced biodiesel with a ratio of saturates to unsaturates conducive to a good fuel product. The direct esterification method in this study proved to be better than the in-situ method for biodiesel production. The in-situ method was also more labour intensive. Chromatography was found to be a fast and efficient method for qualitative and quantitative determination of biodiesel. Characterization tests showed that the quality of biodiesel produced was satisfactory. It also showed that the methods used in this study were feasible for the satisfactory production of biodiesel which meets local and international specifications.

Thesis (PhD(Agric))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The energy paradigm shift from fossil fuels to renewable energy sources is driven, among others, by a growing sustainability awareness, necessitating more sophisticated measurements in terms of a wider range of criteria. Technical efficiency, financial profitability, environmental friendliness and social acceptance are some of the factors determining the sustainability of renewable energy systems. The resulting complexity and conflicting decision criteria, however, constitute major barriers to processing the information and decision-making based on the information. Seeking to implement local bioenergy systems, policymakers of the Cape Winelands District Municipality (CWDM), South Africa, are confronted with such a problem. Following a case study approach, this study illustrates how life-cycle assessment (LCA), multi-period budgeting (MPB) and geographic information systems (GIS) can aid the decision-making process by providing financial-economic, socio-economic and environmental friendliness performance data in a structured and transparent manner, allowing for a comparison of the magnitude of each considered criterion along the life-cycle. However, as the environmental impacts cannot readily be expressed in monetary terms on a cardinal scale, these considerations are given less attention or are omitted completely in a market economy. By measuring the various considerations on an ordinal scale and by attaching weights to them using the multi-criteria decision analysis (MCDA) approach, this study, illustrates how to internalise externalities as typical market failures, aiding policymakers of the CWDM to choose the most sustainable bioenergy system. Following the LCA approach, 37 lignocellulosic bioenergy systems, encompassing different combinations of type of harvesting and primary transport, type of pretreatment (comminution, drying, and fast pyrolysis) and location thereof (roadside or landing of the central conversion plant), type of secondary transport from the roadside to the central conversion plant, and type of biomass upgrading and conversion into electricity, were assessed against five financial-economic viability criteria, three socio-economic potential criteria and five environmental impact criteria. The quantitative performance data were then, as part of the MCDA process, translated into a standardised ‘common language’ of relative performance. An expert group attached weights to the considered criteria using the analytical hierarchy process (AHP). The ‘financial-economic viability’ main criterion received a weight of almost 60%, ‘socio-economic potential’, nearly 25% and ‘lowest environmental impact’, the remainder of around 16%. Taking the prerequisite of financial-economic viability into consideration, the preferred option across all areas of the CWDM (despite various levels of productivity) comprises a feller-buncher for harvesting, a forwarder for primary transportation, mobile comminution at the roadside, secondary transport in truck-container-trailer combinations and an integrated gasification system for the conversion into electricity. / AFRIKAANSE OPSOMMING: Die energie paradigma verandering van fossielbrandstowwe na hernubare energiebronne word gedryf deur ‘n groeiende klem op volhoubaarheid, wat ook meer gesofistikeerde meting in terme van ‘n wyer verskeidenheid maatstawwe vereis. Tegniese doeltreffendheid, finansiële winsgewendheid, omgewingsvriendelikheid en sosiale aanvaarbaarheid is sommige van die faktore wat die volhoubaarheid van hernubare energie stelsels bepaal. Die verskeidenheid oorwegings bring egter kompleksiteit en konflik mee by die verwerking van inligting en die besluitneming wat daarop berus. Beleidmakers van die Kaapse Wynland Distriksmunisipaliteit wat ten doel het om plaaslik bio-energie stelsels te implementeer, word met hierdie probleem gekonfronteer. Hierdie ondersoek illustreer aan die hand van ‘n gevallestudie benadering hoe lewensiklus analise, multiperiode begroting en geografiese inligtingstelsels besluitneming kan ondersteun deur die voorsiening van finansieel-ekonomiese, sosio-ekonomiese (indiensneming) en omgewingsvriendelikheid prestasie data op ‘n gestruktureerde en deursigtige wyse. Dit maak die vergelyking van die waardes van al die kriteria by elke fase van die lewensiklus moontlik. Aangesien die omgewingseffekte nie geredelik in monetêre terme op ‘n kardinale skaal gemeet kan word nie, kry hulle binne die markekonomie minder aandag of word selfs buite rekening gelaat. Deur hierdie verskeidenheid kriteria op ‘n ordinale skaal te meet en gewigte met behulp van multikriteria besluitneming aan hulle toe te ken, toon hierdie ondersoek hoe om eksternaliteite as tipiese markmislukkings te internaliseer om beleidmakers van die Kaapse Wynland Distriksmunisipaliteit in staat te stel om die mees volhoubare bio-energie stelsel te kies. Met behulp van lewensiklus analise is 37 lignosellulose bio-energie stelsels geïdentifiseer as verskillende kombinasies van oes van die bome, primêre vervoer van houtstompe, vooraf verwerking (verspaandering, droging, vinnige pirolise), die ligging van hierdie aktiwiteite (langs ‘n plantasie of by ‘n sentrale omsettingsaanleg), tipe sekondêre vervoer van houtspaanders vanaf die plantasie na die sentrale omsettingsaanleg en tipe biomassa opgradering en omsetting van die houtspaanders na elektrisiteit. Die verskillende stelsels is gemeet aan die hand van vyf finansieel-ekonomiese kriteria, drie indiensneming potensiaal kriteria en vyf omgewingsimpak kriteria. Die kwantitatiewe metings is deur middel van multikriteria besluitneming omgeskakel na ’n gestandaardiseerde “gemeenskaplike taal” van relatiewe prestasie. Lede van ‘n ekspertgroep het gewigte is aan die onderskeie kriteria met behulp van die analitiese hierargie proses toegeken. Aan die finansieel-ekonomiese lewensvatbaarheid hoof kriterium is ‘n gewig van by die 60% toegeken, aan die indiensnemingspotensiaal bykans 25% en aan omgewingsvriendelikheid sowat 16%. Die voorkeur kombinasie vir al die areas van die Kaapse Wynland Distriksmunisipaliteit sluit in ‘n saag-bondelaar vir die oesproses, ‘n plantasie-vragmotor vir primêre vervoer, mobiele verspaandering langs die plantasie, ‘n vragmotor-skeepshouer-treiler kombinasies vir die sekondêre vervoer van houtspaanders en ‘n geïntegreerde vergassingstelsel vir die omsetting van houtspaanders na elektrisiteit.

Thesis (MScFor (Forest and Wood Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The purpose of the study was to investigate the potential tree taxa that could be grown as a source of biomass in the Cape Winelands region. The trials comprises of two different aspects. The first being the estimation of potential volume, density and biomass of a pair of six year-old stands of E. gomphocephala and E. cladocalyx families at two climatically different sites within the study region. The second part of the study was the early growth assessment of alternative taxa that could be planted in the region compared to the regional mainstay E. cladocalyx. The volume of families was estimated using appropriate volume equations and using the form height were none were available. The best volume yield varied from 4.6 to 11.2 m3 ha-1a-1, at the dry and sub-humid sites, respectively. Wood density, estimated from non-destructive samples at both sites, varied from 620 (sub-humid) to 588 kg m-3 (dry site). The estimated biomass production rate of the top producing families yielded 2.7 and 6.9 t ha -1a -1 at the dry and sub-humid sites, respectively. In terms of estimated biomass and survival, E. gomphocephala was more suited to the dry site, while E. cladocalyx displayed superior yield than E. gomphocephala on the sub-humid site, but not significantly so. Early growth assessment of the trial of alternative taxa found that the hybrid E. grandis × camldulensis and E. grandis × urophylla had superior biomass indices, but were more susceptible to infestation by Thaumastocoris peregrinus and Gonipterus scuttelatus. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om potensiële boom taksa vir gebruik as ’n bron van biomassa in die Kaapse Wynlandstreek te ondersoek. Die proewe behels twee aspekte: eerstens die beraming van die potensiële volume, digtheid en biomassa van sesjaaroue opstande met families van E. gomphocephala en E. cladocalyx by twee klimatologies verskillende groeiplekke in die studiegebied; tweedens die beoordeling van die vroeë groei van alternatiewe taksa wat in die streek geplant kan word in vergelyking met die streek se historiese staatmaker-spesie E. cladocalyx. Die volume van die families is beraam deur gebruik te maak van toepaslike volumevergelykings, en met behulp van ’n vormfaktor waar vergelykings nie beskikbaar was nie. Die volume aanwas by die droë en sub-humiede groeiplekke was onderskeidelik 4.6 en 11.2 m3 ha-1j-1. Houtdigtheid is beraam deur nie-destruktiewe monsters uit die opstand te neem. Gemiddelde digthede het variëer van 588 (sub-humied) tot 620 kg m-3 (droë groeiplek). Die beraamde biomassaproduksie van die top-families beloop onderskeidelik 2.7 en 6.9 t ha -1j -1 vir die droë en sub-humiede groeiplekke. In terme van beraamde biomassa en oorlewing, is E. gomphocephala meer geskik vir droër groeiplekke , terwyl E. cladocalyx by die sub-humiede groeiplek ’n hoër opbrengs as E. gomphocephala getoon het, hoewel nie betekenisvol nie. Beramings van die vroeë groei by die proef met alternatiewe taksa het getoon dat die basters E. grandis × camldulensis en E. grandis × urophylla hoër biomassa-indekse het, maar meer vatbaar is vir besmetting deur Thaumastocoris peregrinus en Gonipterus scuttelatus. / Centre for Renewable and Sustainable Energy Studies

Biomass gasification has attracted the interest of researchers because it produces zero carbon to the atmosphere. This technology does not only produce syngas but also the byproducts which can be used for various application depending on quality.The study conducted at Melani village in Alice in the Eastern Cape of South Africa was aimed at investigating the possible applications of the gasification byproducts instead of being thrown away. Pine wood was employed as the parent feedstock material for the gasifier. Biomass gasification by-products were then collected for further analysis. The studied by-products included tar(condensate), char, soot and resin. These materials were also blended to produce strong materials.The essence of the blending was to generate ideal material that is strong but light at the same time.The elemental analysis of the samples performed by CHNS analyser revealed that carbon element is in large quantities in all samples. The FTIR spectra showed almost similar results for all the studied samples, since the samples are end products of lignocellulosegasification. SEM gave the sticky images of resin as well as porous char structures. Char showed a higher heating value of 35.37MJ/Kg when compared to other by-products samples.

Low cover crop biomass production is a major obstacle to the success of conservation agriculture currently promoted as panacea to the inherent problem of soil erosion and loss of soil productivity in the Eastern Cape (EC). Therefore, this study evaluated cover crop management strategies for optimizing biomass production for better soil cover, soil nitrogen (N) and phosphorus (P) fertility, weed control and maize yields. The strategies tested are cover crop bicultures, selection of an adapted lupin cultivar and seeding rate, and the feasibility of rain fed winter cover cropping. The cover crop experiments were carried in rotation with summer maize between the winter of 2009 and summer of 2010/2011. Biculture trial was carried out by seeding oat (Avena sativa) and vetch (Vicia dasycarpa) at three mixture ratios and as sole crops under irrigation. On a separate irrigated trial, two lupin cultivars (Lupinus angustifolius var Mandelup & Qualinock) were seeded to a range of seeding rate, 40 to 220 kg ha-1. To study the feasibility of rain fed winter cover cropping, oat, vetch, rye (Lolium multiflorum), barley (Hordeum vulgare), radish (Raphanus sativa) and triticale (Triticale secale) were relayed into a maize crop in February, March and April of 2010. The irrigated trials were followed with SC701 maize cultivar, whilst the rain fed trial was followed with DKC61-25 maize cultivar. Bicultures gave higher cover crop biomass than sole vetch, increasing with an increase in the oat component of the mixture. Increased N and P uptake was observed with bicultures compared to sole oat, however, the levels were comparable to sole vetch. Sole vetch increased soil inorganic N and P at maize planting, whilst the slow decomposition by sole oat residue resulted in mineral lock up. Bicultured cover crop residues had intermediate decomposition rates and resulted in optimum levels of inorganic N and P for prolonged periods compared to sole crops. Weed suppression by the bicultures was comparable to sole cover crops. Biculturing technology significantly (P<0.05) increased maize grain yield compared to sole oat and the yields were comparable to those from sole vetch. For lupins, 206 kg ha-1 seeding rate gave the optimum biomass yield. Weed dry weights in both cover crop and maize crop decreased with an increase in lupin biomass. Comparable soil total N and inorganic P values at maize planting, were observed from plots planted to 120, 180 and 220 kg ha-1. Maize grain yield increased with an increase in lupin seeding rate. The study on rain fed winter cover cropping had most cover crop species’ biomass decreasing with each delay in planting except for radish, which increased. Vetch produced the highest amounts of biomass from February and March planting whilst radish had the highest biomass in April planting. The two species resulted in the greatest N improvement compared to the other species. Regardless of the grazing, the grass specie residues managed to persist to the next cropping season and the residue remaining were comparable to that of radish and vetch. Late-planted cover crops had the greatest residue remaining than early-planted, as a result, April planted cover crops provided better weed suppression than March and April planted. Vetch provided the highest maize grain yield (4005 kg ha-1) whilst all other species tested had comparable grain yields. The results suggested that bicultures could be grown to give sufficient biomass for both weed suppression and soil fertility improvement. Furthermore, increasing lupin plant densities improve its function as a cover crop with respect to weed suppression, soil fertility improvement and maize yields. The study also showed that for dry land systems, February and March planted vetch and April planted radish can provide the greatest biomass and maize yield improvement.

The overall objective of the whole study was to assess whether conservation agriculture (CA) systems can work in the Eastern Cape Province (EC). The CA systems were engaged through cover cropping to address land degradation problems by emphasizing high biomass production in order to realize short term benefits such as moisture conservation, weed suppression and soil fertility benefits under rainfed conditions in the central region of the Eastern Cape province. Since rainfall is the most limiting factor to crop production in the EC, a within season rainfall distribution analysis was conducted to expose the quality of the season (onset, end and duration) and hence the feasibility of CA systems to guide agronomic decisions by farmers in EC. To assess season parameters, thirty four years of daily rainfall was collected from the University of Fort Hare Research station and used to conduct the rainy pentad (5 day rainfall totals) analysis and the daily rainfall analysis using INSTAT software programme. Based on the pentad analysis, results showed that Alice does not have a rainy season in 1 out of 2 years (50% probability) but has one in 1 out of 4 years (25% probability level). This criterion proved to be harsher and conservative when compared to the daily rainfall approach which is more precise in measuring trends on season parameters. The daily rainfall analysis indicated a 65% feasibility for the dry land cropping systems in the EC. The pentad analysis however was effective in illustrating seasonality and it showed that the wet season begins on the 1st of November, ending on the 22nd of March lasting for 140 days. Though the season duration appeared too long, the existence of dry spells during critical growth stages adversely affects the quality of the season. The daily rainfall analysis also managed to derive a signal which can guide planting decisions. For planting to be successful, this analysis determined that 20 mm of rain should be received in two consecutive days after the 1st of November. A screening trial for cover crop biomass production and weed suppression was conducted on-station Fort Hare Research Farm (32°46' S and 26° 50' E), and Msobombvu village (MSBV) (32°44' S, and 26° 55' E) over two seasons (2007/08 and 2008/09). Six summer cover crops i.e. cowpea (Vigna unguiculata), dolichos lablab (Dolichos argenteus), sunnhemp (Crotalaria juncea), buckwheat (Fagopyrum sagittatum), forage sorghum (Sorghum bicolor) and sunflower (Helianthus annus) were evaluated for biomass yield, and weed suppression. Decomposition rates, moisture conservation and residual effects of these cover crops on the succeeding main crop were also evaluated under dryland conditions. The screening trial was laid in randomized complete block design replicated three times. Forage sorghum (Sorghum bicolor) and sunflower (Helianthus annus) were identified as high biomass producers and their dry matter yields ranged from 8 -12 t ha-1. These cover crops can be useful in generating high biomass in rainfed cropping systems in the EC. Other cover crops produced 3 - 4 t ha-1 of biomass which fell short of the 6 t ha-1 expected benchmark. However, these biomass yields were important in weed management since all cover crop species showed a similar degree of weed suppression which surpassed the weed fallow treatment. As dead mulches, the cover crops failed to show residual moisture conservation and weed control benefits for the succeeding maize crop mainly because of poor residue persistence, and low harvestable fallow rainfall. Buckwheat (Fagopyrum esculentum), was selected for further investigations in a follow up trial on station in 2008/09 season because of its weed smothering qualities, suitability to short cycle rotations, and possible allelopathic properties. The trial aimed at finding weed and cost effective management options of buckwheat that are none detrimental to the succeeding maize crop. Results showed that cropping systems where buckwheat is followed by a main crop may not work as they are unprofitable with respect to R100 rand invested. Though perceived to have allelopathic properties, buckwheat failed to demonstrate the possibilities of allelopathic action against weeds. Intercropping trial was conducted on-station in 2007/8-2008/09 seasons to try and find better ways of fitting legume cover crops into maize based cropping systems without compromising production of staple cereals on limited landholdings. The trials evaluated three factors in factorial combination, cover crop planting date, intercropping strategy, and cover crop species. The trial was laid as 2 x 2 x 3 factorial arranged in a split-split plot design. The main plot factor was cover crop planting date, cover crops simultaneously planted with maize and cover crop planted two weeks after planting maize (DKC 61-25). The sub-plot factor was intercropping strategy, strip intercropping and betweenrow intercropping. The sub-sub-plot factor was cover crop species, Dolichos lablab (Dolichos argenteus (Highworth), and Cowpea Vigna ungiculata (Agrinawa) plus control plots of sole maize. Results showed that same time planting of leguminous cover crops with maize using the in-between row intercropping patterns can derive appreciable system biomass (maize/cover crop) yields, utilize land efficiently whilst getting favourable maize grain yield. Based on the rainfall analysis, results showed that the probability of success when relay seeding cover crops after two weeks into standing maize is low (15% chances of success). This suggests that relay intercropping strategies would not work due to the unavailability of a good quality season.

Achieving high biomass yields of cover crops has been a challenge to the success of Conservation Agriculture (CA) practices in the Eastern Cape (EC). A study was conducted to evaluate strategies for optimizing cover crop biomass production. Trials were carried out to screen summer and winter cover crops, as well as evaluate intercropping patterns and planting dates for biomass, weed suppression and subsequent maize yield under irrigation. Four summer legume cover crop species were evaluated under a Randomised Complete Block Design (RCBD) design. The cover crops were fertilized with 13.34 kg ha-1 of N, 20 kg ha-1 P and 26.66 kg ha-1 K. In the 2008/09 summer season a maize crop was superimposed on the 2007/08 screening trial under no-till. The crop was fertilized with 60 kg ha-1 of N. An intercropping trial was conducted over two seasons as a way of investigating the best way of incorporating cover crops into farmers cropping systems. This was done bearing in mind the limitation of resources such as land. The trial evaluated 3 factors laid as a 2 x 2 x 3 factorial arranged in a split-plot design. The main factor was cover crop planting date (planting at maize planting or 2 weeks after maize planting). The sub plot factor was intercropping pattern (strip intercropping and between row intercropping). A trial was also conducted to evaluate the effect of planting date (End of April and mid May) and four winter legume cover crop species on cover crop biomass, weed suppression and maize grain yield. The experiment was laid out as a Randomised Complete Block Design (RCBD) replicated 3 times. In the subsequent summer season a maize crop was superimposed on the winter trial to test the residual effects of the cover crop species. Another study was conducted to evaluate winter cereal cover crop species for biomass accumulation, weed suppression and subsequent maize grain yield. The cover crops as well as a weedy fallow control plot treatments were laid out as a Randomised Complete Block Design replicated 3 times. In the subsequent summer season a maize crop was superimposed on the site under no-till to evaluate the residual effect of the cover crops on maize. The results showed sunhemp, cowpea and lablab as the best cover crops with high biomass and weed suppression whilst mucuna was the least. Sunhemp consistently yielded higher cover biomass averaging 11200 kg ha-1 over the two seasons whilst mucuna had a consistently lowest average biomass yield of 4050 kg ha-1. These cover crops were above the critical 6 t ha-1 for effective weed suppression. There was a significant (p<0.01) relationship of cover crop dry weight and weed dry weight in both seasons. Subsequent maize grain yield was significantly higher in the sunhemp plots (64.2 %) than the weedy fallow plot. Mucuna, lablab and cowpea had maize grain yield increases of 16.6%, 33% and 43.2% respectively. Intercropping cover crops at maize planting yielded higher cover crop dry weights than a delay in intercropping cover crops. A delay in intercropping resulted in significantly higher average maize grain yield of 4700 kg ha-1 compared to intercropping at maize planting (3800 kg ha-1) and sole maize (4300 kg ha-1) over the two seasons. Strip intercropping also yielded higher (5000 kg ha- 1) average maize grain yield compared to row intercropping (3600 kg ha-1) and sole maize (4300 kg ha-1). There was a significant (p<0.05) relationship between cover crop dry weight in the 2007/08 season and maize grain yield in the 2008/09 season. Early planting grazing vetch gave the highest biomass yield of 8100 kg ha-1 whilst early planted red clover had the lowest biomass of 635 kg ha-1. Low weed dry weights were also obtained from the early planted grazing vetch as opposed to the other treatments. There was a significant (p<0.001) relationship of cover crop dry weight and weed dry weight. In the subsequent 2008/09 summer season early planted grazing vetch had the highest maize yield of 7500 kg ha-1 which was 56.3 % more than the weedy fallow plot had 4800 kg ha-1. The weedy fallow plot also had high weed infestation than the cover crop plots. There were significant (p<0.01) relationships between cover crop dry weight and maize grain yield, winter weed dry weight and maize grain yield and summer weed dry weight and maize grain yield. The results also showed triticale (13900 kg ha-1) as the best winter cover crop for biomass production. Italian ryegrass (6500 kg ha-1) produced the least amount of biomass. In The subsequent maize crop white oats gave highest maize grain yield (6369 kg ha-1) which was 33 % more than the weedy fallow plot (4784 kg ha- 1). There were also significant (p< 0.01) relationships of maize grain yield and winter weed dry weight, maize grain yield and summer growing weeds. The various studies demonstrated that there is opportunity for high biomass production under small scale farmers irrigated conditions using cover crops both in winter and summer. Best bet cover crops were sunhemp, cowpea and lablab for summer and triticale, white oats, barley, Italian ryegrass and grazing vetch for winter. Cover crops can also be incorporated into farmers cropping systems as sole crops or intercrops within the maize based cropping systems. Strip intercropping can be used by farmers as a way of introducing cover crops. Critical to achievement of high biomass is the time of planting cover crops with high biomass when planting is done early. A 2 week delay in strip intercropping cover crop into maize can be used as a way of incorporating cover crops into farmers cropping systems with minimal maize yield reduction.