Thesis (M.Agric. (Agricultural Economics)) --University of Limpopo, 2011 / Maize is the most important cereal crop grown in South Africa. This crop is produced throughout the country under diverse environments. The study only focuses on the technical efficiency because it is an important subject in developing agriculture where resources are limited, but high population growth is very common. Technical efficiency is the ability of a farmer to obtain output from a given set of physical inputs. Farmers have a tendency of under and/or over- utilising the factors of production. The main aim of this study was to analyse the technical efficiency of small-scale maize producers in Ga-Mothiba rural community of Limpopo Province. The objective of the study was to determine the level of technical efficiency of small- scale maize producers and to identify the socio-economic characteristics that influence technical efficiency of small-scale maize producers in Ga-Mothiba. Purposive and Snowball sampling techniques were used to collect primary data from 120 small-scale farmers. Cobb-Douglas production function was used to determine the level of technical efficiency and Logistic regression model was used to analyse the variables that have influence the technical efficiency of maize production. Cobb-Douglas results reveal that small-scale farmers in Ga-Mothiba are experiencing technical inefficiency in maize production due to the decreasing return to scale, which means they are over-utilising factors of production. Logistic regression results indicate that out of 13 variables included in the analysis as socio-economic factors, 10 of them (level of education, income of the household on monthly basis, farmer`s farming experience, farm size, cost of tractor hours, fertiliser application, purchased hybrid maize seeds, membership to farmers` organisation, is maize profitable) were found to be significant and 3 (gender, age and hired labour) are non-significant. However, farm size was found to be the most significant variable at 99% level, showing a positive relationship to small- scale maize producer`s technical efficiency.Therefore, it is recommended that government should do the on-farm training since farmers mainly depend on trial and error and farmers` should have access to enough arable land and tractor services. However, farmers need to be trained on matters relating to fertiliser application, on the amount of seeds a farmer should apply per ha, and the importance of using hybrid seed.

Thesis (M.Sc. Agric.) --University of Limpopo, 2011 / Maize is the most important cereal crop grown in South Africa. This crop is produced throughout the country under diverse environments. The study only focuses on the technical efficiency because it is an important subject in developing agriculture where resources are limited, but high population growth is very common. Technical efficiency is the ability of a farmer to obtain output from a given set of physical inputs. Farmers have a tendency of under and/or over- utilising the factors of production. The main aim of this study was to analyse the technical efficiency of small-scale maize producers in Ga-Mothiba rural community of Limpopo Province. The objective of the study was to determine the level of technical efficiency of small- scale maize producers and to identify the socio-economic characteristics that influence technical efficiency of small-scale maize producers in Ga-Mothiba. Purposive and Snowball sampling techniques were used to collect primary data from 120 small-scale farmers. Cobb-Douglas production function was used to determine the level of technical efficiency and Logistic regression model was used to analyse the variables that have influence the technical efficiency of maize production. Cobb-Douglas results reveal that small-scale farmers in Ga-Mothiba are experiencing technical inefficiency in maize production due to the decreasing return to scale, which means they are over-utilising factors of production. Logistic regression results indicate that out of 13 variables included in the analysis as socio-economic factors, 10 of them (level of education, income of the household on monthly basis, farmer`s farming experience, farm size, cost of tractor hours, fertiliser application, purchased hybrid maize seeds, membership to farmers` organisation, is maize profitable) were found to be significant and 3 (gender, age and hired labour) are non-significant. However, farm size was found to be the most significant variable at 99% level, showing a positive relationship to small- scale maize producer`s technical efficiency. Therefore, it is recommended that government should do the on-farm training since farmers mainly depend on trial and error and farmers` should have access to enough arable land and tractor services. However, farmers need to be trained on matters relating to fertiliser application, on the amount of seeds a farmer should apply per ha, and the importance of using hybrid seed.

Thesis (M. A. Agricultural Management (Agricultural Extension)) -- University of Limpopo, 2019 / Smallholder farmers’ need for regular supply of adequate, quality and affordable seed led to the establishments of Community-Based Maize Seed Production Schemes (CBSPSs) in most developing countries, including South Africa. In view of the important influence of perception on the adoption and continued use of an innovation, this study was undertaken to evaluate farmers’ perceptions of CBSPSs in Polokwane and Lepelle-Nkumpi Local Municipalities of Limpopo province. The conceptualization of perception used in this study was based on the Düvel (1991) framework. The evaluation focused on whether planting the scheme’s main product, improved Open-Pollinated Varieties (improved OPV maize) seed meets farmers’ needs based on their perceptions and the extent of farmers’ planting of improved OPV maize. A census approach was used in view of the small numbers of seed producers in the schemes; all scheme members (50) were, therefore, interviewed between 27 March and 21 April 2017. To allow for comparison, an equal number of farmers (50) who were not members of the scheme were also interviewed. Data was collected from farmers using a semi-structured questionnaire. Descriptive and inferential statistics were applied to analyze the data using SPSS software. A binary logistic model was used to analyze factors that influence farmer perceptions on OPV benefits. The study findings showed that there is a significant relationship between awareness knowledge of improved OPV maize and planting of improved OPV maize. Furthermore, the results showed that farmers perceptions of the advantages and disadvantages of improved OPV maize seed were not different among scheme and non-scheme members as they were all in agreement that improved OPV maize have more benefits than their own previously recycled seeds. Finally, findings showed that respondents municipality and scheme membership had a significant, effect on the positive perception of planting improved OPV maize seeds. Other explanatory variables such as sex, farming experience, years of viii schooling, farm size, income and age of participants had no significant effect on farmer perceptions. It is therefore recommended that improved OPV maize be made widely available and promoted based on its advantages to enhance its adoption. Future studies on these seed schemes could look into the production and financial analysis of CBSPSs to ascertain their profitability and sustainability. / Agricultural Research Council (ARC)

Made available in DSpace on 2017-07-10T17:40:42Z (GMT). No. of bitstreams: 1 Neusa_Francisca_Michelon_Herzog_Tese.pdf: 1684844 bytes, checksum: 1dea8e85b06380395c232da8430d6092 (MD5) Previous issue date: 2012-11-08 / Pinhão-manso (Jatropha curcas L.) belonging to the Euphorbiaceae family from Americas has been disseminated in tropical and sub-tropical regions in the globe and also largely distributed in Asiatic and African continents. This specie has its seeds as the main way of spreading itself. Generally the reproductive material (seeds and fruit) is strongly influenced by the genitor plants, by the local climatic conditions that act on the development that comprises since the pollination process, the physiological maturity of the seed, to the plantation success. Due to its importance, this research aimed to characterize the flower and fruit production of the specie in an intercropped and monocultivation system, as well as to determine the production, the physical quality of the Jatropha curcas L. seeds, in Pato Bragado city in West of Paraná state. The study assessment period took 13 months and started in December 2010. The field experiment was set in areas of intercropped with Tifton and in a monocultivation system. The emission of floral buds and the flower and fruit abortion were weekly registered computing the formed fruit and quantifying the developed seeds. The number of locules was evaluated with formed seeds in fruitage, and some aspects related to the seeds were measured such as: the weight in grams, the length and the width in centimeters. The quality tests in the seeds were: germination in sand, germination speed index and tetrazolium test. The variance was analyzed by the Sisvar program, and the statistic difference between the average were compared by the Tukey test of 5% of error probability. The monocultivation favored the productivity. Four periods of flourishing were observed and the most expressive one occurred during the August to November period. The tendency to concentrate a bigger number of female flowers was noticed since the trees got older, and the most vigorous seed were produced during August to November period / O pinhão-manso (Jatropha curcas L.) pertencente à família Euphorbiaceae, é nativo das Américas, apresenta-se disseminado nas regiões tropicais e subtropicais do globo e amplamente distribuído nos continentes Asiático e Africano. Esta espécie tem as sementes como principal forma de dispersão. De modo geral, sabe-se que o material reprodutivo (sementes e frutos) é bastante influenciado pelas características das plantas genitoras, pelas condições climáticas do local em que atua sobre o desenvolvimento, que compreende desde a polinização, maturidade fisiológica da semente, ao sucesso do plantio. Dada a sua importância, esta pesquisa objetivou caracterizar a produção de flores e frutos da espécie, em cultivo consorciado e monocultivo, determinar a produção, a qualidade física e fisiológica das sementes de Jatropha curcas L., no município de Pato Bragado no Oeste do Paraná. O período das avaliações compreendeu 13 meses, tendo início em dezembro de 2010. O experimento à campo, foi realizado em áreas de cultivo consorciado com tifton e sistema de monocultivo. Semanalmente, a emissão de botões florais e abortamento de flores e frutos, foram anotados, computando os frutos formados, abortados e quantificando as sementes desenvolvidas. Em frutos, avaliou-se o número de lóculos com sementes formadas. Mensurou-se nas sementes: massa em gramas; comprimento e largura em centímetros. Os testes de qualidade em sementes foram: germinação em areia, índice de velocidade de germinação e teste de tetrazólio. Para a análise estatística, realizou-se análise de variância pelo programa Sisvar, no caso de diferença estatística entre as médias foram comparadas pelo teste de Tukey a 5% de probabilidade de erro. A monocultura favoreceu a produtividade. Foram observados quatro períodos de florescimento, sendo que o mais expressivo ocorreu no período de agosto a novembro. Houve tendência a concentrar maior número de flores femininas á medida que as árvores ficaram mais velhas. As sementes mais vigorosas, foram produzidas no período de agosto a novembro

Organic agriculture is an important and growing sector of U.S. and world food production. Consumers are increasingly aware of and interested in the production practices and impacts associated with agriculture and as such, are showing a preference for sustainably produced, raised, and harvested foods. In order to continue to meet the growing demand for organic produce, organic growers need cultivars that are optimally adapted to organic and low input conditions. Quality seed is the foundation of any functional and stable farming system. Unfortunately the lack of organically bred and produced seed is hindering the continued growth and success of organic farming. Meeting the needs of the organic sector has been a challenge for the seed industry; it is an industry that often doesn't understand the specific and unique requirements associated with the diversity of environmental and market demands of organic systems. However, organic farmers and the organic food systems they supply, require a robust organic seed system that is appropriately adapted to regional agronomic challenges and market needs, meets standards and regulations, and encompasses the social and ecological values of organic agriculture. One plausible approach to meeting the cultivar and seed needs of organic and low input production systems is through the use of participatory plant breeding (PPB). PPB is a collaborative approach for identifying and developing genetically diverse plant material and varieties involving partnerships among formal sector breeders and researchers, farmers, extension agents, educators, and end users. Participatory plant breeding fundamentally changes the way that formal breeding programs and farmers manage germplasm and plant genetic resources. Typically, formal breeding programs restrict access to germplasm and breeding materials and only supply farmers with finished varieties. In PPB, farmers are involved in the early stages of creation and evaluation of germplasm and breeding material, and stay engaged with the breeding process until new varieties are created. PPB is an excellent model for breeding specifically for organic systems because organic systems in developed countries have many similarities to low-input agricultural systems in the developing world. Some of these parallels include heterogeneous growing environments, a wide range of end uses and marketing strategies, lack of suitably adapted and/or derived varieties, lack of attention from the formal seed sector, and a reduced reliance on synthetic inputs (compared to conventional systems). Breeding for organic systems is a relatively young field and breeders in the formal sector do not have a good handle on what traits are important for robust production under organic conditions. Thus the opportunity to meld farmers' experience and knowledge with breeders' expertise is an effective way to breed for organic production systems. The purpose of this project was to investigate and explore the opportunities and challenges of organic plant breeding using participatory research methods. This research had three goals: 1) to develop an open pollinated broccoli with contemporary quality traits for organic production systems using participatory strategies; 2) to compare broccoli selections made by formally trained plant breeders and farmer breeders; and 3) to capture the stories and experiences of the formal breeders and farmer breeders involved with this broccoli material in order to contribute to the growing wealth of knowledge on collaborative and organic breeding work. The Oregon State University Vegetable Breeding Program made significant progress towards decreasing the variability of the broccoli project material through three successive years of modified half-sibling selections. Evaluations and selections were based more strongly on quality traits rather than soley on production traits such as yield. Although progress was incremental and statistically verified in only three out of the fifteen quality traits, we observed trends in the data indicating progress towards an increasingly uniform, stable, and reliable open pollinated broccoli with specific adaptation for organic production systems. There were very few differences between broccoli materials developed by formally trained plant breeders and farmer breeders. This was especially true for the three cultivars developed in the Pacific Northwest (PNW) (one in Washington and two in Oregon). The 'East Coast' population, which had been collaboratively selected by formal and farmer breeders in New York, expressed significantly distinct differences from the PNW materials. When the farmer breeder and formal breeder materials were pooled together and compared to pooled check cultivars they expressed significant differences for nearly all traits across all years. This demonstrated that all of the collaboratively developed open pollinated materials are distinctly different from the F1 hybrids currently available. Our work has demonstrated a few of the myriad of positive outcomes achievable with the use of participatory plant breeding for organic production systems. The participatory nature of this project resulted in increased confidence and feelings of empowerment for all involved. Both farmers and breeders felt their involvement was socially beneficial and widened their networking and seed community circles. The farmer-bred cultivar 'Solstice' is now available as a result of Jonathan Spero's work, and a cultivar tentatively named 'Benton' is about to be released for sale through Oregon State University. Our results agree with previous study findings that formal and farmer breeder selections are often not distinctly different; thus providing evidence for continuing to support the involvement and education of farmers in plant breeding, especially in reference to organic production systems. This study demonstrates the potential of collaboratively developed and farmer-bred cultivars to become viable and vibrant open pollinated alternatives to the current open pollinated cultivars on the market today. / Graduation date: 2013

Interest in planting Jatropha curcas L. for the production of biodiesel is growing exponentially. The properties of the crop and its oil have persuaded investors to consider J. curcas oil as a substitute for fossil fuels. However, this plant is still undomesticated, basic agronomic properties are not thoroughly understood and the environmental effects on growth have not been investigated. This thesis investigated different approaches that may contribute to improving the productivity of this plant. Seed germination and methods of propagation are usually the first consideration in any plant development programme. The effects of aerosol smoke, smoke water, potassium nitrate, naphthalene acetic acid and indole-3-butyric acid on germination and seedling growth of J. curcas were investigated. Seed coat removal accelerated water imbibition and germination occurred within 48 h. Seeds exposed to aerosol smoke failed to germinate over the whole study period of three months. There were no significant differences in total germination between the treatments and the untreated control (intactand shelled-seed). However, shelled-seeds had a shorter mean germination time. The seedlings were subsequently sown in trays under shade house conditions and different seedling growth traits measured after three months. Smoke water, potassium nitrate and naphthalene acetic acid produced significantly heavier seedlings with longer stems and roots, wider stems and a higher vigour index compared to the control treatments. Smoke water, potassium nitrate and naphthalene acetic acid stimulated seedling growth and vigour of J. curcas. This opens the possibility of applying these treatments to produce quality seedlings for large scale planting and accelerated plant establishment in production orchards. Effective pollination is a prerequisite for many crops to increase seed-set and fruit production. Experiments were conducted to determine factors that could influence seed production in this potential biofuel seed crop. Controlled pollination experiments showed that plants required pollinator visits for seed production and were genetically selfx compatible. Pollen-supplementation did not lead to increased fruit set, suggesting that seed production in the study population was not pollen-limited. Both male and female flowers produced nectar and were highly attractive to honeybees. These insects were effective pollinators of J. curcas, as shown by experiments in which flowers exposed to single or multiple visits by honeybees set significantly more fruit than those from which visits were precluded. Pollinator-mediated self-pollination led to marginally lower levels of seed production relative to cross-pollination. Progeny from selfed plants had significantly shorter roots than progeny of outcrossed plants. However, in general, there was little evidence of inbreeding depression. The present results provide empirical evidence that honeybees are effective pollinators of J. curcas. Fruit arising from selfpollination were almost as numerous and as large as those arising from crosspollination, suggesting that promotion of cross-pollination does not have to be a priority in orchard management for fruit yield. Manipulation of pollen development and function is of vital importance for crop development and improvement. Experiments were conducted to investigate pollen viability, in vitro pollen germination and in vivo pollen tube growth in J. curcas. Light and fluorescence microscopy were employed to examine the different developmental stages. It was possible to determine pollen viability and distinguish between fresh and dead pollen using 2,3,5-triphenyltetrazolium chloride (TTC). Pollen germination was significantly higher in an agar-based medium composed of sucrose, boric acid and calcium nitrate compared with the control treatment (distilled water). Supplementation of IAA to the different media significantly increased pollen germination and pollen length compared with the control treatment. Pollen from hermaphrodite flowers had a lower viability, lower germination rates and shorter pollen tubes, with abnormal shapes, compared to the pollen from male flowers. Pollen tubes from both self- and crosspollinated flowers entered the ovary within 8 hours after pollination (HAP). However, at 6 HAP, the pollen tube length and growth rate were significantly higher in crosscompared to self-pollinated pollen. Our results suggest that TTC is a reliable test for pollen viability; boric acid, calcium nitrate, sucrose and addition of IAA are essential and beneficial for pollen germination in this plant. Pollen germination and pollen tube growth were not inhibited, nor interfered with, as a result of self-pollination treatments. During, both types of pollination, fertility is maintained as evidenced by ovule penetration by pollen tubes. This suggests that type of pollination has no influence on the success of fertilization in J. curcas. Manual pruning is one of the major management practices in commercial plantations of J. curcas, resulting in production of more branches and thus increased potential for more inflorescences leading to a higher seed yield. Experiments were conducted to determine the response of J. curcas plants to manual pruning under summer and winter conditions. The results showed that manual pruning under both conditions significantly increased the number of branches per plant. However, there were no significant differences in number of branches between winter and summer manual pruning. Winter pruning, however, had a significantly wider crown diameter compared to the control and summer pruning. Both treatments produced significantly less fruits/per plant in the subsequent season compared to the un-pruned control. This study revealed that winter and summer manual pruning may be suitable practice to promote branching. Manual pruning, however, is time consuming, labour intensive and expensive. A study was conducted to determine the potential of different plant growth regulators (PGRs) to increase the number of lateral branches of J. curcas plants. A single foliar application of BA (benzyladenine) at 12 mmol l-1 significantly increased branches in both the pot (4) and field (13.2) trials compared to manual pruning (MP) (1.8 and 5.7 respectively) and control (no new branches) plants. In the field, treatment with TIBA (2,3,5-triiodobenzoic acid) (1 mmol l-1) significantly increased the number of branches (15.9) after seven months from application. Of all the PGRs examined, DK (Dikegulac) (2,3:4,6-di-Oisopropylidene- 2-keto-L-gulonic acid) at 2 mmol l-1 produced the maximum number of branches (18) in the field seven months after application. Concentrations of 2 and 3 mmol I-1 of MH (Maleic hydrazide) (1,2-dihydro-3,6-pyridazinedione, coline salt) significantly increased the number of branches, four and seven months after spraying in both the pot trial in the shade house and field respectively. Under field conditions J. curcas plants responded better to all the PGRs (DK < TIBA < BA < MH) when treated once, with insignificant variations of other growth parameters. This study indicates that a single foliar application of PGRs under field conditions can be an alternative method to MP for increasing the number of lateral branches of J. curcas plants. The field chemical pruning experiment was continued to determine the potential subsequent effects of the different PGRs on seed production. In the subsequent year following the single foliar application, the parameters of flowering, fruit set, fruit characteristics, total oil content and free fatty acid (FFA) content were evaluated. Number of flowers per plant and number of fruits per bunch were significantly affected by the different treatments. However, there were no variations in the degree of fruit set. A single foliar application of BA (6-benzylaminopurine) produced more flowers per plant, more fruits per bunch, heavier and bigger fruits and seeds with more oil compared to MP (manual pruning). TIBA (2,3,5-Triiodobenzoic acid) produced significantly more flowers per plant and heavier fruits compared to the control and MP treatments. However, it produced significantly bigger fruits with more seeds and a higher oil content than MP. DK (Dikegulac) (2,3:4,6-di-O-isopropylidene-2-keto-Lgulonic acid) produced more flowers per plant and seeds with high oil content compared to the control and MP. However, it produced more fruit per bunch and more seeds per fruit compared to MP. MH (Maleic hydrazide) produced more flowers per plant, heavier and bigger fruits with numerous, heavier and oil rich seeds compared to the control and MP. This study indicates that foliar application of PGRs can be used in J. curcas to increase seed production and improve fruit quality. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

The overall aim of this PhD study was to develop protocols to improve the efficiency of eucalypt controlled pollinations (CPs) in order to make it more cost-effective for forestry companies to perform them on a commercial scale on small-flowered species. To achieve this, three research areas were explored, namely pollen handling, breeding systems and controlled pollination technique. Study species were Eucalyptus grandis, E. dunnii, E. smithii, E. nitens, E. urophylla and E. macarthurii. The first specific aim of the study was to identify a suitable liquid in vitro germination medium for reliably testing pollen viability of all six study species. Six levels of sucrose [0, 10, 20, 30, 40 and 50% (w/v)] were tested, both with (0.15 mg l-1) and without boric acid. The optimal sucrose concentration was found to be 30% (w/v), with boric acid stimulating pollen tube growth. A second aim was to determine temperatures suitable for the short-, medium- and long-term storage of E. smithii, E. nitens and E. grandis pollen. Pollen samples were stored at room (25oC), refrigerator (4oC), freezer (-10oC) and liquid nitrogen (-196oC) temperatures, and pollen viability tested every two months over a 12-month period. There was a rapid decline in the germination of pollen stored at 25oC, while temperatures cooler than 4oC appeared to maintain pollen viability for the duration of the 12-month study. Recommendations were thus to use a refrigerator for short-term (< 2 months), a freezer for medium-term (up to 10 months) and cryopreservation for longer-term storage. In the second part of the study, breeding systems of E. urophylla and E. grandis were examined by studying pollen-tube growth in the style after single-donor self- and cross-pollinations. Results showed that, in addition to both species exhibiting reduced seed yields following self-pollination, pollen tubes from self-pollen took significantly longer than those from cross-pollen to grow to the base of the style. This suggested the presence of both late-acting self-incompatibility and cryptic self-incompatibility (CSI) as possible mechanisms responsible for outcrossing in these two species. In a follow-up study, the siring ability of self- and cross-pollen was examined after single- and mixed-donor pollinations were performed on E. grandis. Once again, single-donor cross-pollinations resulted in a significantly higher number of seeds compared to self-pollinations. In addition, microsatellite molecular markers revealed that 100% of the progeny from mixed (self + outcross) pollinations were outcrossed, confirming the competitive advantage of cross-pollen. To date, CSI has never been associated with Eucalyptus, making this the first study to suggest its presence in the genus. For the final study area, three CP-techniques were compared, namely the Conventional method, One Stop Pollination (OSP) and Artificially Induced Protogyny (AIP), in E. grandis, E. smithii and E. macarthurii maternal parents. Although the AIP technique produced the highest seed yields in all three species, it also resulted in high self- and foreign-pollen contamination (determined using microsatellite markers). This necessitated exploration of different methods of isolating the pollinated flower, and this led to the identification of a novel method which uses sodium alginate gel. Flowers hand-pollinated and isolated with sodium alginate produced progeny that were 100% outcrossed with the applied pollen, confirming the superiority of this innovative isolation technique compared to the currently used exclusion bag. Sodium alginate isolation also increased the efficiency of CPs as the gel was naturally shed, removing the need for operators to return to the tree to remove the isolation material, and thereby reducing the cost per seed. Application of these results should make commercial CP-seed production of small-flowered eucalypts a practical reality. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

Made available in DSpace on 2016-06-02T19:51:21Z (GMT). No. of bitstreams: 1 DissRARJ.pdf: 1930702 bytes, checksum: a1b0d68f6f193815099874af8118a5e1 (MD5) Previous issue date: 2006-05-23 / The production of corn seeds involves a complex agro-industrial production chain whose main agents must offer products of high quality and low price to stay competitive. Efficient tools to coordinate this chain are thus essential to fulfill these conditions. This work proposes a linear programming model for the strategic planning of production, storing and transportation, designed to minimize production, transportation and tax costs. The model is a function of crop planning, capacity and client demand restrictions. Although relevant to the product s final cost, taxes are not traditionally considered by the planning methods currently used by the seed industry. The raw material is generally sent to the industrial unit closest to the farm; proximity to the end consumer is of secondary importance. The main productive processes and features of the seed industry described here are based on literature and visits to plants that produce corn seeds. The mathematical model detailed in this work is implemented using the GAMS programming language and the resulting system of equations solved with CPLEX. The model was validated by using different scenarios with real-world data collected during the visits to the plants; the results were consistent with those expected. Next, the results given by the model of a case study with data for an entire season were compared against those obtained by one of the companies employing the traditional method of shortest distance between farm and industrial unit. The proposed model showed a substantial decrease in total cost when compared to the traditional method. This study also confirmed the importance of integrating taxes with production and transportation planning at the logistics level. / A produção de sementes de milho envolve uma cadeia de produção agroindustrial complexa cujos agentes devem primar por oferecer produtos de alta qualidade a um baixo custo para se manterem competitivos no mercado. Instrumentos eficientes para a coordenação dessa cadeia são fundamentais para atender a esta exigência, orientando seus agentes para o cumprimento dos objetivos comuns. Neste trabalho um modelo de programação linear é proposto para realizar o planejamento tático da produção, estocagem e de transportes de forma a minimizar custos de produção, transportes e fiscais, atendendo ao mesmo tempo às restrições de programação da colheita, de capacidade e de demanda. Tradicionalmente, não são considerados nos métodos de planejamento do setor custos fiscais, como o de ICMS, que se mostram relevantes no custo unitário do produto final. A matéria-prima, em geral, é enviada para a unidade mais próxima ao campo de produção agrícola, deixandose para um segundo plano a proximidade da demanda. As principais características do processo produtivo e do setor são descritas de acordo com a literatura e visitas a empresas produtoras de sementes. Utilizou-se a linguagem GAMS e o solver CPLEX para resolver o modelo matemático. O modelo foi implementado e testado com dados realistas das empresas visitadas em diferentes cenários, verificando-se coerência nas respostas obtidas. Realizou-se um estudo de caso em uma das empresas estudadas utilizando-se os dados completos de uma safra e os resultados obtidos com o modelo proposto foram comparados com o método empregado na empresa, que considerava apenas a menor distância entre a região agrícola e a unidade industrial. Os resultados dessa comparação foram bastante satisfatórios, proporcionando uma redução significativa dos custos considerados. Além disso, foi confirmada, também para este caso, a importância de incorporar os custos fiscais na disciplina de logística integrando planejamento tributário com o de produção e dos transportes.