Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 95-96. / by William Kensett Nuttle. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 163-166. / by Theodore von Rosenvinge IV. / M.S.

Variabilities of hydraulic and solute transport properties of soil are examined at three scales: pore-scale, sample volume-scale, and field-scale. Undisturbed soil cores were taken at 19 subsites spaced logarithmically along a 150 m line transect in a Groseclose mapping unit near Blacksburg; Virginia. Three core sizes were taken at each subsite at the soil surface and 0.5 m depth. 'Small' cores were-40x54 mm; 'medium' cores were 60X100 mm; and 'large' cores were 100x150 mm. Macropore effects on solute transport were evaluated using monocontinuum and bicontinuum models. Bicontinuum-predicted solute breakthrough curves (BTC) closely agreed with observed BTC data with mean errors of reduced concentrations </- 0.05 for 97% of the samples, Monocontinuum predicted BTC's had comparable fits with 80% of the samples having mean errors </- 0.07. The simpler monocontinuum model was chosen for estimating dispersion coefficients for all samples on the basis that seven percent error in concentration is acceptable for the purpose of making field predictions in light of high spatial variability. Sample volume did not significantly affect the low variation (coefficients of variation, (CV) of 7-20%) soil properties bulk density or moisture retention characteristics in Ap or Bt horizons. Large cores are recommended for assessing high variation (CV of 60-280%) fluid transport parameters, saturated hydraulic conductivity (Ks), pore water velocity and dispersion coefficients (D) since they yielded less variance than the smaller cores. Ranges of about 25 m were determined for log-transformed Ks and D from semivariograms. Monte Carlo simulations were used to predict field-average BTC's. / Master of Science

A laboratory study was conducted to determine nitrogen removal rates from a land-applied wastewater as a function of the length of time the wastewater remained in the root zone. A digital simulation model was used as an aid in describing soil water (and wastewater) movement through the root zone under wet conditions (i.e. root zone 50- 75% saturated). A procedure was developed to predict the rate and volume of drainage as a function of initial soil moisture content, amount of liquid applied, and time after liquid application. An exact relationship between nitrogen removals and wastewater residence time in the root zone could not be developed. However, removals of up to 95% of applied NH₄-N were demonstrated in an 18-cm deep root zone with residence times as short as 2 hours. The exact nature of these removals was not determined. / Ph. D.

Modern pig farming production may over burden the environment with organic substances, exposure of bacterial pathogens and introduction of resistance gene. This may be caused by the pig’s droppings, lack of seepage management or accidental spillage of seepage which may impact on the environment and its physicochemical parameters. The objective of this study is to determine and assess the level of bacteriological pollution emanating from the pig farm and their impact on the physicochemical parameters of soil and water as well as to identify the presence of antibiotic resistance gene of these prevailing bacteria. Soil and water samples were collected monthly for a period of six months (March- August 2013). Samples were collected at pig enclosures, soil 20 m and 100 m away from pig enclosures, constructed wetland used for treating pig farm wastewater, soil 20m and 100 m away from constructed wetland. Procedure followed for analysing soil and water samples includes physicochemical analyses, viable cell counts of 10-1 to 10-8 dilutions, identification of bacteria using API 20E test kit, antibiotic susceptibility analyses, and identification of resistance gene using molecular procedures. The media that were used for viable cell counts were, Nutrient agar, MacConkey Agar, Xylose Lysine Deoxycholate agar (XLD agar), and Eosin Methylene Blue (EMB). Physicochemical parameters of water showed unacceptable high levels of analysed parameters for BOD (163 mg/L to 3350 mg/L), TDS (0.77 g/L to 6.48 mg/L), COD (210 mg/L to 9400 mg/L), NO3 (55 mg/L to 1680 mg/L), NO2 (37.5 mg/L to 2730 mg/L), and PO43− (50 mg/L to 1427 mg/L) were higher than the maximum permissible limits set by Department of Water Affairs and Forestry (DWAF). For soil samples TDS (0.01g/L to 0.88 g/L), COD (40 mg/L to 304 mg/L), NO3 (32.5 mg/L to 475 mg/L), and NO2 (7.35 mg/L to 255 mg/L) and PO43- (32.5 mg/L to 475 mg/L ) were observed to be higher than recommended limits set by Federal Ministry for the Environmental (FME). The viable cells in soil samples 30cm depth ranged from 0 cfu/mL to 2.44 x 1010cfu/mL, in soil 5cm depth ranged from 1.00 x 101 cfu/mL to 1.91 x 1010 cfu/mL, and in water samples viable cells ranged from 5.00 x 101 to 5.05 x 109. Pseudomonas luteola (Ps. luteola), Escherichia vulneris (E. vulneris), Salmonella choleraesuis spp arizonae, Escherichia coli 1(E. coli 1), Enterobacter cloacae, Pseudomonas flourescens/putida (Ps. flourescens/putida), Enterobacter aerogenes, Serratia ordoriferal, Pasteurella pneumotropica, Ochrobactrum antropi, Proteus vulgaris group, Proteus vulgaris, Salmonella spp, Aeromonas Hydrophila/caviae/sobria1, Proteus Mirabillis, Vibrio fluvials, Rahnella aquatillis, Pseudomonas aeruginosa (Ps. aeruginosa), Burkholderia Cepacia, Stenotrophomonas maltophilia (St. maltophilia), Shwenella putrefaciens, Klebsiela pneumonia, Cedecea davisa, Serratia liquefaciens, Serratia plymuthica, Enterobacter sakaziki, Citrobacter braakii, Enterobacter amnigenus 2, Yersinia pestis, Serratia ficaria, Enterobacter gergoriae, Enterobacter amnigenus 1, Serratia marcescens, Raoutella terrigena, Hafnia alvei 1, Providencia rettgeri, and Pantoa were isolated from soil and water samples from the pig farm. Isolates were highly resistant to Penicillin G, Sulphamethaxazole, Vancomycin, Tilmocozin, Oxytetracycline, Spectinomycin, Lincomycin, and Trimethoprim. The most resistance genes detected in most isolates were aa (6’)-le-aph (2”)-la, aph (2”)-lb, aph (3”)-llla, Van A, Van B, Otr A and Otr B. Pig farm seepage is causing bacterial pollution which is impacting negatively on the natural environment in the vicinity of pig farm by introducing bacterial pathogens that have an antibiotic resistance gene and is increasing the physicochemical parameters for soil and water in the natural environment at the pig farm. It is therefore recommended that pig farms should consider the need to implement appropriate regulatory agencies that may include the regular monitoring of the qualities of final effluents from waste water treatment facilities. In addition there is a need to limit soil pollution in order to safe guard the natural environment in the vicinity of pig farm from bacteriological pollution and introduction of antibiotic resistance gene. It is also recommended that more advanced technologies should be introduced that will assist pig farms to manages the seepage properly. / Environmental Sciences / M. Sc. (Environmental Sciences)

Understanding the transport and retention of radionuclides in the environment is important for protecting freshwater supplies and minimizing impact to biologic systems. Technetium-99 (Tc⁹⁹) is a radionuclide of interest due to its long half-life (2.13 x 10⁵ years) and toxicity. In the form of pertechnetate (TcO₄⁻), Tc is expected to move nearly unretarded in the subsurface. Under reducing conditions Tc can precipitate in low solubility Tc oxide (TcO₂·nH₂O) and/or Tc sulfide (Tc₂S[subscript x]) phases. The studies presented in this dissertation investigate the physiochemical mechanisms for the transport and retention of Tc. Transport studies determined that TcO₄⁻ would move at pore water velocity in unsaturated sediments. Geochemical studies of contaminated sediments determined that nearly ~ 25 % of the total Tc was retained in phases associated with iron oxide and aluminosilicate minerals, thus reducing the mobility of Tc. Studies of Tc₂S[subscript x] mineral phases, generated using nano Zero Valent Iron (nZVI) and sulfide (HS-) in sediments, determined that Tc could be stabilized in mineral phases as Tc₂S[subscript x] that were slower to reoxidize than TcO₂·nH₂O phases. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Feb. 14, 2013 - Feb. 14, 2014

Modern pig farming production may over burden the environment with organic substances, exposure of bacterial pathogens and introduction of resistance gene. This may be caused by the pig’s droppings, lack of seepage management or accidental spillage of seepage which may impact on the environment and its physicochemical parameters. The objective of this study is to determine and assess the level of bacteriological pollution emanating from the pig farm and their impact on the physicochemical parameters of soil and water as well as to identify the presence of antibiotic resistance gene of these prevailing bacteria. Soil and water samples were collected monthly for a period of six months (March- August 2013). Samples were collected at pig enclosures, soil 20 m and 100 m away from pig enclosures, constructed wetland used for treating pig farm wastewater, soil 20m and 100 m away from constructed wetland. Procedure followed for analysing soil and water samples includes physicochemical analyses, viable cell counts of 10-1 to 10-8 dilutions, identification of bacteria using API 20E test kit, antibiotic susceptibility analyses, and identification of resistance gene using molecular procedures. The media that were used for viable cell counts were, Nutrient agar, MacConkey Agar, Xylose Lysine Deoxycholate agar (XLD agar), and Eosin Methylene Blue (EMB). Physicochemical parameters of water showed unacceptable high levels of analysed parameters for BOD (163 mg/L to 3350 mg/L), TDS (0.77 g/L to 6.48 mg/L), COD (210 mg/L to 9400 mg/L), NO3 (55 mg/L to 1680 mg/L), NO2 (37.5 mg/L to 2730 mg/L), and PO43− (50 mg/L to 1427 mg/L) were higher than the maximum permissible limits set by Department of Water Affairs and Forestry (DWAF). For soil samples TDS (0.01g/L to 0.88 g/L), COD (40 mg/L to 304 mg/L), NO3 (32.5 mg/L to 475 mg/L), and NO2 (7.35 mg/L to 255 mg/L) and PO43- (32.5 mg/L to 475 mg/L ) were observed to be higher than recommended limits set by Federal Ministry for the Environmental (FME). The viable cells in soil samples 30cm depth ranged from 0 cfu/mL to 2.44 x 1010cfu/mL, in soil 5cm depth ranged from 1.00 x 101 cfu/mL to 1.91 x 1010 cfu/mL, and in water samples viable cells ranged from 5.00 x 101 to 5.05 x 109. Pseudomonas luteola (Ps. luteola), Escherichia vulneris (E. vulneris), Salmonella choleraesuis spp arizonae, Escherichia coli 1(E. coli 1), Enterobacter cloacae, Pseudomonas flourescens/putida (Ps. flourescens/putida), Enterobacter aerogenes, Serratia ordoriferal, Pasteurella pneumotropica, Ochrobactrum antropi, Proteus vulgaris group, Proteus vulgaris, Salmonella spp, Aeromonas Hydrophila/caviae/sobria1, Proteus Mirabillis, Vibrio fluvials, Rahnella aquatillis, Pseudomonas aeruginosa (Ps. aeruginosa), Burkholderia Cepacia, Stenotrophomonas maltophilia (St. maltophilia), Shwenella putrefaciens, Klebsiela pneumonia, Cedecea davisa, Serratia liquefaciens, Serratia plymuthica, Enterobacter sakaziki, Citrobacter braakii, Enterobacter amnigenus 2, Yersinia pestis, Serratia ficaria, Enterobacter gergoriae, Enterobacter amnigenus 1, Serratia marcescens, Raoutella terrigena, Hafnia alvei 1, Providencia rettgeri, and Pantoa were isolated from soil and water samples from the pig farm. Isolates were highly resistant to Penicillin G, Sulphamethaxazole, Vancomycin, Tilmocozin, Oxytetracycline, Spectinomycin, Lincomycin, and Trimethoprim. The most resistance genes detected in most isolates were aa (6’)-le-aph (2”)-la, aph (2”)-lb, aph (3”)-llla, Van A, Van B, Otr A and Otr B. Pig farm seepage is causing bacterial pollution which is impacting negatively on the natural environment in the vicinity of pig farm by introducing bacterial pathogens that have an antibiotic resistance gene and is increasing the physicochemical parameters for soil and water in the natural environment at the pig farm. It is therefore recommended that pig farms should consider the need to implement appropriate regulatory agencies that may include the regular monitoring of the qualities of final effluents from waste water treatment facilities. In addition there is a need to limit soil pollution in order to safe guard the natural environment in the vicinity of pig farm from bacteriological pollution and introduction of antibiotic resistance gene. It is also recommended that more advanced technologies should be introduced that will assist pig farms to manages the seepage properly. / Environmental Sciences / M. Sc. (Environmental Sciences)

Foram utilizados os métodos de planejamento fatorial e de análise de superfície de resposta para obtenção e validação experimental de modelos estatísticos que simulam os efeitos dos elementos Cd, Cu, Fe e Zn contidos em um lodo de esgoto, utilizado na melhoria das condições de cultivo em solos. O lançamento de poluentes no ambiente tem estado sob severo controle nos países desenvolvidos, e vem crescendo a importância dada ao problema nos países em desenvolvimento, como o Brasil. O maior volume desses resíduos tem origem no lixo doméstico e no tratamento de esgotos. Lodo de esgoto (LE) ou biossólido é uma denominação genérica para o resíduo sólido gerado pelos sistemas de tratamento de águas residuárias. O LE pode apresentar, em sua composição, elementos químicos e biológicos indesejáveis do ponto de vista ambiental, ou seja, pode conter elementos que, em contato com o homem e/ou com a fauna e a flora, causem doenças e contaminações diversas. Portanto, qualquer decisão sobre um destino final mais apropriado para o LE depende da avaliação e minimização dos riscos de contaminação do ambiente e do homem. Neste trabalho, realizou-se experimento com a adição de concentrações diferenciadas de LE a um solo proveniente da Zona da Mata do estado de Pernambuco, Brasil. Procedeuse a lixiviação do solo contendo teores diferenciados de LE para simular a ocorrência de chuvas durante o período dos experimentos. Através da análise da variância das medidas de concentração de Cd, Cu, Fe e Zn, retidos no solo, foram testadas as validades de modelos estatísticos para simular a retenção desses elementos do LE. Os resultados demonstraram que a modelagem estatística de análise de resposta constitui-se ferramenta indispensável e, desde que não se conheça bem o fenômeno estudado, a modelagem estatística pode reforçar o papel dos modelos empíricos na análise preliminar de qualquer fenômeno / Optimized mathematical models relative to the effects of the use of sewage sludge in the cultivation in the soils, Brazil, will be elaborated and validated here. The releasing of pollutants in the environment has been under severe control in developed countries, and there has been given greater importance to the matter in developing ones, such as Brazil. The greatest volume of it comes from domestic waste and from the wastewater treatment. Sewage sludge (SS) is a general denomination to the solid waste generated by the wastewater treatment system. The SS may present in its composition undesirable, from the environmental point of view, biological and chemical elements, that is, it may contain elements that may cause several diseases and contaminations in contact with men or with the fauna and the flora. Thus, any decision about the most appropriate final destination of the SS depends on the evaluation and the minimization of contamination risks to men and to the environment. There are plenty of these elements, and they may be classified in two groups: chemical contaminants and biological contaminants (many of them are pathogen organisms, which cause human diseases). Among the pollutants of the SS, the chemical contaminants (heavy metals) constitute the greatest group and must be constantly monitored because of the risks of contamination to men, animals and plants. Among the several existing alternatives to the disposition of the SS, it seems that the most convenient and one of the most promising, mainly from the economic point of view, is the agricultural utilization, not only because of its potential as conditioner and fertilizer of soils, but also because of the fact that the soils have, in general, a high power of clearance. In this work, it will be presented strategies to the definition of adequate conditions of experiments by means of planning techniques and of experimental optimization. From this methodology, it is hopeful to get the definition of working optimized conditions in a way that it may be obtained models of simulation to the effects of the sewage sludge in the cultivation of spices in the soils

Made available in DSpace on 2017-06-01T18:20:27Z (GMT). No. of bitstreams: 1 Pre-textuais e Capitulo I.pdf: 7232754 bytes, checksum: c4a84d355f5c2392ff0089b4dbb125f3 (MD5) Previous issue date: 2008-06-05 / Optimized mathematical models relative to the effects of the use of sewage sludge in the cultivation in the soils, Brazil, will be elaborated and validated here. The releasing of pollutants in the environment has been under severe control in developed countries, and there has been given greater importance to the matter in developing ones, such as Brazil. The greatest volume of it comes from domestic waste and from the wastewater treatment. Sewage sludge (SS) is a general denomination to the solid waste generated by the wastewater treatment system. The SS may present in its composition undesirable, from the environmental point of view, biological and chemical elements, that is, it may contain elements that may cause several diseases and contaminations in contact with men or with the fauna and the flora. Thus, any decision about the most appropriate final destination of the SS depends on the evaluation and the minimization of contamination risks to men and to the environment. There are plenty of these elements, and they may be classified in two groups: chemical contaminants and biological contaminants (many of them are pathogen organisms, which cause human diseases). Among the pollutants of the SS, the chemical contaminants (heavy metals) constitute the greatest group and must be constantly monitored because of the risks of contamination to men, animals and plants. Among the several existing alternatives to the disposition of the SS, it seems that the most convenient and one of the most promising, mainly from the economic point of view, is the agricultural utilization, not only because of its potential as conditioner and fertilizer of soils, but also because of the fact that the soils have, in general, a high power of clearance. In this work, it will be presented strategies to the definition of adequate conditions of experiments by means of planning techniques and of experimental optimization. From this methodology, it is hopeful to get the definition of working optimized conditions in a way that it may be obtained models of simulation to the effects of the sewage sludge in the cultivation of spices in the soils / Foram utilizados os métodos de planejamento fatorial e de análise de superfície de resposta para obtenção e validação experimental de modelos estatísticos que simulam os efeitos dos elementos Cd, Cu, Fe e Zn contidos em um lodo de esgoto, utilizado na melhoria das condições de cultivo em solos. O lançamento de poluentes no ambiente tem estado sob severo controle nos países desenvolvidos, e vem crescendo a importância dada ao problema nos países em desenvolvimento, como o Brasil. O maior volume desses resíduos tem origem no lixo doméstico e no tratamento de esgotos. Lodo de esgoto (LE) ou biossólido é uma denominação genérica para o resíduo sólido gerado pelos sistemas de tratamento de águas residuárias. O LE pode apresentar, em sua composição, elementos químicos e biológicos indesejáveis do ponto de vista ambiental, ou seja, pode conter elementos que, em contato com o homem e/ou com a fauna e a flora, causem doenças e contaminações diversas. Portanto, qualquer decisão sobre um destino final mais apropriado para o LE depende da avaliação e minimização dos riscos de contaminação do ambiente e do homem. Neste trabalho, realizou-se experimento com a adição de concentrações diferenciadas de LE a um solo proveniente da Zona da Mata do estado de Pernambuco, Brasil. Procedeuse a lixiviação do solo contendo teores diferenciados de LE para simular a ocorrência de chuvas durante o período dos experimentos. Através da análise da variância das medidas de concentração de Cd, Cu, Fe e Zn, retidos no solo, foram testadas as validades de modelos estatísticos para simular a retenção desses elementos do LE. Os resultados demonstraram que a modelagem estatística de análise de resposta constitui-se ferramenta indispensável e, desde que não se conheça bem o fenômeno estudado, a modelagem estatística pode reforçar o papel dos modelos empíricos na análise preliminar de qualquer fenômeno

The current interest in conservation agriculture (CA) technologies is a result of the need to reduce excessive land degradation in most crop producing areas as well as to enhance sustainable food production. Cover crops that are usually grown under CA to provide soil cover, may offer secondary benefits, depending on the farming system. The concept of growing cover crops is a relatively new phenomenon to smallholder farmers. Production of large biomass yields and weed suppression from cover crops were major challenges affecting success and uptake of CA technologies by smallholder irrigation farmers. Coupled with this, low soil fertility limit maize productivity and reduce water use efficiency on smallholder irrigation schemes in what is largely a water strained agro-ecology in South Africa. While cover cropping can increase maize productivity, benefits of different types of mulch are not well understood, leading to challenges in selecting the most appropriate cover crop species to grow in the Eastern Cape Province (EC) of South Africa (SA) which has a warm temperate climate. With respect to any new technology, smallholder farmers are more interested in the economic benefits. Cover crops have been defined as leguminous or non-leguminous plants used for ground cover in various temporal and special configurations used in crop or animal production systems. The purpose of these cover crops is to improve on or more of the following: soil erosion, availability and cycling of N, P, K, Ca and other nutrients, soil moisture and water infiltration, and weed or pest control (Eilitta et al., 2004).. Improvement of animal or human diet may be additional goals. This definition accommodates diverse systems which may include intercrop and sole-cropping systems. In the Eastern Cape Province of South Africa, a government initiative has promoted the growing of winter cover crops in smallholder irrigation schemes (Allwood, 2006). In other parts of Africa, legume food crops have been simultaneously grown with cereal staples to improve both soil cover and human diet (Eilitta et al., 2004). Winter experiments were undertaken in 2007 and 2008 to evaluate biomass accumulation, C and N uptake, weed suppression and response to fertilization. Winter cover crops planted included; oats (Avena sativa), grazing vetch (Vicia dasycarpa), faba bean (Vicia faba), forage peas (Pisum sativum) and lupin (Lupinus angustifolius). After cover crops were terminated, the effects of residues on weeds, fertility, moisture conservation and maize productivity were undertaken in the 2007/08 and 2008/09 summer seasons. Field studies were also done in the 2007/08 and 2008/09 summer seasons to investigate effects of strip intercropping patterns (3:2; 4:2; and 6:2 patterns) of maize (cv. PAN 6479) with mucuna (Mucuna pruriens) or sunnhemp (Crotalaria juncea) on maize productivity and summer cover crop biomass production. In a separate experiment effects of relay intercropping sunnhemp, mucuna and sorghum (Sorghum bicolor) on biomass accumulation and maize productivity were investigated. Decomposition, N and P release from both winter cover crops and summer cover crops were also assessed in laboratory incubation experiments. Oats, grazing vetch and forage peas cover crops produced mean dry mass of 13873 kg/ha, 8945.5 kg/ha and 11073 kg/ha, respectively, while lupin had the lowest dry mass of 1226 kg/ha over the two seasons. Oats responded to fertilization while, there was little or no response from the other winter cover crops. Oats and grazing vetch also reduced weed density by 90 % and 80 % respectively while lupin only reduced weed density by 23 % in relation to the control plots. Nitrogen uptake was 254 kg N/ha for oats while it was 346 kg N /ha for grazing vetch. In the subsequent summer season, grazing vetch and forage pea residues significantly (P < 0.01) improved soil inorganic N. Oat and grazing vetch residues significantly (P < 0.05) reduced weed dry masss and weed species diversity compared to plots with lupin residues and the control. Lack of maize fertilization tended to reduce maize yields but not for maize grown on grazing vetch residues. From an economic perspective, grazing vetch resulted in the highest returns. Decomposition of winter cover crops was much faster for grazing vetch followed by forage peas and lastly oats. Oats had 40 % ash free dry mass remaining after 124 days while grazing vetch and forage peas had 7 % and 16 % respectively. Maximum net mineralized N and P were greater for grazing vetch (84.8 mg N/kg; 3.6 mg P/kg) compared to forage peas (66.3 mg N/kg; 2.7 mg P/ha) and oats (13.7 mg N/kg; 2.8 mg P/kg). In the strip intercropping trials, sunnhemp achieved the highest biomass yield of 4576 kg/ha in the 3:2 pattern while mucuna achieved 1897 kg/ha for the same strip pattern. The 3:2 strip intercropping pattern slightly depressed yields, however, yield reduction was more pronounced in the first season where water stress was experienced. Growing maize on previous cover crop strips failed to increase maize productivity probably due to weed growth during the fallow reducing mineral N in these strips. Decomposition was faster in sunnhemp leaves and mucuna compared to sunnhemp stems. Sunnhemp stems had about 65 % of ash free dry mass remaining after the end of the experiment at 132 days while just over 10 % of mucuna and sunnhemp leaves still remained. Mucuna mineralized 60 mg N/kg and 3.2 mg P/kg and sunnhemp mineralized 45 mg N/kg and 3.5 mg P/kg. Relay intercropping did not significantly (P > 0.05) affect maize biomass and grain yield. Sorghum experienced the largest drop in biomass when relay-intercropped with maize. Mucuna resulted in the highest N uptake (271 kg N/ha) in sole cropping while sorghum had the lowest (88 kg N/ha). Grazing vetch results in high biomass yields with minimal fertilizer application in a warm-temperate climate. Grazing vetch mulch is also the most cost effective mulch for better early weed control, improving soil mineral N status, water conservation and ultimately enhanced maize productivity in smallholder irrigation maize-based systems. The 3:2 pattern maximizes summer cover crop biomass yields compared to the 6:2 and 4:2 patterns. However, the 3:2 pattern may slightly depress yields in a water stressed environment. Relay intercropping mucuna, sunnhemp and sorghum into a maize crop at 42 days after maize sowing has no effect on maize productivity while cover crop biomass yields are low. Having a long winter fallow period after maize harvesting, a common practice in the study area, reduces the positive impact of legume cover crops on soil mineral N. Results suggest that winter cover crops may result in weed control, soil fertility and maize yield improvement benefits while a long fallow period may cancel-out these benefits for summer cover crops. Grazing vetch is a cost effective cover crop that produces high maize yields with minimal fertilizer input. Maize growing on oat mulch requires more fertilizer application than crops growing on grazing vetch mulch. Conservation agriculture systems in which summer cover crops are grown alongside the maize crop with a long winter fallow period do not produce the intended CA benefits.