Master of Science / Department of Agronomy / Ignacio Ciampitti / Soybean [Glycine max (L.) Merr.] yields have continuously increased over time. Seed yields are determined by the genotype, environment, and management practices (G × E × M) interaction. Closing yield gaps require a continuous improvement in the use of the available resources, which must be attained via implementation of better management decisions. Linear relationships between seed yield and nitrogen (N) demand are reported in the scientific literature. Main sources of N to the plant are the biological N fixation (BNF) and the soil mineralization processes. On overall, only 50-60% of soybean N demand is met by the BNF process. An unanswered scientific knowledge is still related to the ability of the BNF to satisfy soybean N demand at varying yield levels. Seed N demand not met by N fixation plus soil mineral N, is then fulfilled by the remobilization of N from vegetative organs during the seed filling period. An early remobilization process reduces the photosynthetic activity (leaves) and can limit seed yield. The objectives of this project were to: i) study yield improvements and contribution of N via utilization of contrasting N conditions under historical and modern soybean genotypes, and ii) quantify main seed N sources during the seed filling period. For objective one, four field experiments were conducted during the 2016 and 2017 growing seasons in Kansas, United States (US) and Santa Fe Province, Argentina (ARG). Those experiments investigated twenty-one historical and modern soybean genotypes with release decades from 1980s to 2010s. As for objective two, three field experiments were conducted during the 2015 and 2016 growing seasons in Kansas, US, studying three soybean genotypes: non-roundup ready (RR), released in 1997; RR-1, released in 2009; and RR-2, released in 2014. Across all studies, seeds were inoculated and tested under three N management strategies: i) control without N application (Zero-N); ii) 56 kg N ha-1 applied at reproductive growth stages (Late-N); and iii) 670 kg ha-1 equally split at three timings (Full-N). As for yield improvements and N limitation, soybean yield improvements from the 1980s to 2010s were documented, representing 29% increases in the US and 21% in ARG. Regarding N management, the Full-N fertilization produced a 12% increase in seed yields in the US and 4% in ARG. As for main seed N sources in objective two, remobilization accounted for 59% of seed N demand, and was negatively related to new N uptake occurring during the seed filling period. Seed N demand for greater yields was dependent on both, N remobilization and new N uptake, while for lower yields, seed N demand was mainly supported by the N remobilization process. These results suggest that: a) high seed yields are somehow limited by the availability of N to express their potential, although the question about N application still remains to be fully investigated, as related to the timing and the environment by plant interactions that could promote a N limitation in soybeans; b) remobilization accounts for majority (59%) of N sourced to the seed, and c) high yielding soybean (modern genotypes) rely on diverse N sources: the N remobilization process plus new uptake of N.

Made available in DSpace on 2016-05-02T13:54:21Z (GMT). No. of bitstreams: 1 AndreVilelaPortugal-dissertacao.pdf: 317174 bytes, checksum: 65c3cef9f280c4503fc3dcc6e9c97aa0 (MD5) Previous issue date: 2012-10-23 / In corn crop, nitrogen is the nutrient most required, which further affects their productivity and which further onerous the cost of production. The purpose of this study was to evaluate sources of nitrogen in corn growth in tillage system. The experiment was conducted at the Vitoria farm, located in the city of Alfenas - MG, in a area of the first year of tillage system. For this, it was used the transgenic corn hybrid Impact of Syngenta, and it was employed random blocks design experimental, with7 treatments and 4 replications, totaling 28 plots. The treatments applied consisted: Control (without nitrogen in coverage); 100 Kg ha-1 of nitrogen in coverage, with ammonium nitrate, without incorporation; 100 Kg ha-1 of nitrogen in coverage, with urea, without incorporation; 100 Kg ha-1 of nitrogen in coverage, with urea and incorporation; 100 Kg ha-1 of nitrogen in coverage, with ammonium sulfate, without incorporation; 100 Kg ha-1 of nitrogen in seeding, with controlled release fertilizer, without incorporation; 50 Kg ha-1 of nitrogen in seeding, with controlled release fertilizer, without incorporation. The assessments of the experiment were performed, after 154 days, according to the parameters: grains productivity, number of grain rows per cob, weight of 1,000 grains, number of grains/row in each cob and number of grains per cob. With this study it can conclude that: the common urea, ammonium sulfate and ammonium nitrate showed similar performance and economic returns in corn crop tillage system; the incorporation of urea did not improve grain productivity and components production in corn growth in tillage system, the controlled release fertilizer is not feasible from an economic standpoint in corn growth in tillage system. / Na cultura do milho, o nitrogênio é o nutriente mais exigido, que mais afeta sua produtividade e o que mais onera o custo de produção. Objetivou-se com o presente trabalho avaliar fontes de nitrogênio no cultivo de milho em sistema plantio direto. O experimento foi realizado na fazenda Vitória, situada no município de Alfenas MG, em uma área de primeiro ano de plantio direto. Para tanto, utilizou-se o híbrido de milho transgênico Impacto da Syngenta, e empregou-se delineamento experimental em blocos ao acaso, com 7 tratamentos e 4 repetições, totalizando 28 parcelas. Os tratamentos empregados foram constituídos por: Testemunha (ausência de N em cobertura); 100 Kg ha-1 de N em cobertura, com nitrato de amônio, sem incorporação; 100 Kg ha-1 de N em cobertura, com ureia, sem incorporação; 100 Kg ha-1 de N em cobertura, com ureia, com incorporação; 100 Kg ha-1 de N em cobertura, com sulfato de amônio, sem incorporação; 100 Kg ha-1 de N na semeadura, com fertilizante de liberação controlada, sem incorporação; 50 Kg ha-1 de N na semeadura, com fertilizante de liberação controlada, sem incorporação. As avaliações do experimento foram realizadas, após 154 dias, de acordo com os seguintes parâmetros: produtividade de grãos, número de fileira de grãos por espiga; peso de 1.000 grãos, número de grãos/fileira em cada espiga e número de grãos por espiga. Com o presente trabalho podemos concluir que: a ureia comum, o sulfato de amônio e nitrato de amônio apresentaram desempenho e retorno econômico semelhantes na cultura de milho em sistema plantio direto; a incorporação da ureia não favoreceu a produtividade de grãos e os componentes de produção no cultivo de milho em sistema plantio direto; o fertilizante de liberação controlada não é viável do ponto de vista econômico no cultivo de milho em sistema plantio direto.

During 1980-81, studies with crested wheatgrass (Agropyron desertorum) and fourwing saltbush (Atriplex canescens) were conducted in controlled environment growth chambers as well as under field conditions to achieve the following objectives: 1. To determine the effect of nitrogen fertilizer on the water use efficiency. 2. To determine the effects of various temperature, water stress and nitrogen treatments on the productivity, nitrogen content and carbohydrate reserves. 3. To determine the effects of N fertilization on fall and spring regrowth. Crested wheatgrass and fourwing saltbush plants were maintained in three growth chambers for 60 days under three temperature regimes (11/7, 19/7 and 27/7 C), two soil moisture stress regimes (-0.3 bars and -15 bars) and three N fertilizer levels (0, 50 and 100 kg of N/ha). During the study, tranpiration and plant biomass data were recorded. During the first week of September, 1980, crested wheatgrass and fourwing saltbush pastures at Nephi, Utah, were subjected to three nitrogen fertilizer levels (0, 50 and 100 kg N/ha). After 60 days the fall regrowth was clipped. In the first week of June 1981 spring regrowth of both species was measured. In the fall of 1981, a second experiment was laid out at Nephi where crested wheatgrass and fourwing saltbush plants were subjected to three soil moisture regimes (dry, medium and wet) and three nitrogen fertilizer levels. At the end of a 60 day study period, dry matter yield, root distribution, water content and soil samples at different incremental soil depths were collected. Under controlled environment conditions, the water use efficiency of both species was six percent more with the application of a moderate amount of nitrogen (50 kg/ha). A high temperature regime (27/7 C) and a high water stress regime (-15 bars) increased the water use efficiency of plants by eight and six percent respectively. Results of the growth chamber experiment revealed that nitrogen fertilization had a significant effect on plant biomass, nitrogen percent and total nonstructual carbohydrate reserves of crested wheatgrass and fourwing saltbush. The data further suggested that nitrogen fertilization can substitute for the adverse effects of low temperature and low soil moisture on plant growth. Nitrogen fertilization during fall increased plant biomass, nitrogen percent and total nonstructural carbohydrate reserves in crested wheatgrass and fourwing saltbush. Fall fertilization did not reduce spring regrowth. It is inferred that under limited soil moisture and low temperature during the fall growing season, a moderate amount of nitrogen fertilizer (50 kg N/ha) may increase the forage availability and water use efficiency of crested wheatgrass and fourwing saltbush to the level of plants maintained at moderate temperature and adequate soil moisture. Nitrogen fertilization (50 kg N/ha) of crested wheatgrass and fourwing saltbush during fall does not reduce plant nitrogen percent or carbohydrate reserves which may limit spring regrowth.

Within Arkansas, Louisiana, Mississippi, Missouri, and Texas, rice acreage is rotated with soybean due to both crops’ adaptability to the clay soils of the midsouthern USA. Two row patterns, two maturity groups, and six seeding rates were examined at Stoneville, MS, in 2009-2010, with respect to soybean growth and yield produced on silt loam soil. Optimal yield for MG IV was 333,000 seed ha-1 (297,000 plants ha-1). Twin-row soybean increased seed yield 7 to 10% more than single-row due to greater LAI, NDVI, and node and pod production. Rice field experiments quantified N loss via ammonia volatilization and determined grain yield for various N sources and preflood application timing. Cumulative ammonia volatilization loss on Tunica clay was minimal (10% of applied N). Grain yields were 6% less when fertilizer was applied 10 days before flood (dbf) as compared to 1 dbf; N sources are available to minimize ammonia volatilization loss.

Cover crops are often planted during the fallow periods of cash crop harvests to cover the soil and reduce erosion but also to provide other ecosystem benefits including capturing residual nutrients and thus, reducing environmental losses of nitrogen (N) and phosphorus (P) in agroecosystems. Among these cover crops, winter rye (Secale cereale) is popular due to its winter hardiness and relatively cheap seed costs. However, growers in the Midwest, USA are reluctant to use winter rye prior to corn (Zea mays L.) due to the potential yield penalty in corn. This thesis introduces two strategies that could minimize winter rye’s effect on corn while providing nutrient loss reduction benefits are precision planting and reducing the seeding rate of winter rye ahead of corn. One study evaluates whether precision planting (planting winter rye strategically to avoid intersecting zones with corn) of winter rye at low seeding rate (37.5 kg ha-1) could produce similar cover crop biomass and quality to normal planted winter rye (50 kg ha-1) and if precision planting can improve performance and N requirement of corn (Chapter 1). The study was conducted in central Indiana during 2020-2021 (CIN21), and southern Illinois during 2021-2022 (SIL22), and 2022-2023 (SIL23) growing seasons. The experiment was arranged in a randomized block design with split plot arrangement. Main plots were three cover crops (a no-cover crop control (NoCC), conventional planted winter rye (CR), and precision planted winter rye (PR). Subplots were six rates of N fertilizer that ranged from 0-280 kg ha-1 for the CIN21 and 0-359 kg ha-1 for SIL22 and SIL23. Our results indicated that shifting from normal planting to precision planting resulted in similar cover crop biomass production with limited effect on winter rye quality [N concentration, Carbon (C):N ratio] and N and C accumulation. In CIN21, the no-cover crop control had higher yield and lower N requirements which was consistent with those of SIL22. The economic optimum rate of N (EORN) was below the typical recommended range for central Indiana and was above the recommended range for southern Illinois. Precision planting resulted in a slight increase in corn yield and N requirement, but overall was more profitable than normal planting due to a reduction in the number of seeds required and higher corn to fertilizer prices. Therefore, we recommend that (i) decision support tools for N management in corn should be revised for addition of cover crops in the Midwest, and (ii) precision planting should be implemented instead of normal planting for greater economic benefit. Future research should evaluate ecosystem services of precision vs. normal planting of winter rye over time. The other study evaluates whether planting method of winter rye (precision vs. conventional) at medium and low seeding rates of winter rye influence cover crop biomass production, N and C concentrations and accumulations, and corn performance (Chapter 2). A trial was conducted in 7 site-yrs in Indiana and Illinois during 2020-2021, 2021-2022, and 2022-2023 growing seasons. The trial was arranged in a randomized complete block design with four replicates. Cover crops [conventional planting (CR) and precision planting (PR)] were factorially arranged with two seeding rates (18.75 vs. 37.5 kg ha-1) for PR and (25 vs. 50 kg ha-1) for CR. Two extra treatments were included as control which were no-cover crop with zero-N and a 224 kg N ha-1 addition to corn. Cover crop biomass, C, N, their uptake, and C:N ratio were evaluated along with corn plant population, and corn grain yield. Our results indicated that winter rye had similar aboveground biomass, N uptake, and C accumulation regardless of planting method and seeding rate suggesting a precision planting at low seeding rate is most economical for cover crop establishment. Corn plant population was only affected by winter rye in one site-yr (CIL23) in which precision planting did not help with minimizing the negative effect of winter rye on corn population. In this study, lack of N fertilization did not decrease corn population but significantly reduced corn grain yield in all site-yrs. Corn grain yield was similar among cover crop treatments (with exception of no cover crop no N) but in one of the site-yrs, precision planting at 18.75 kg ha-1 resulted in greater corn yield than the no-cover crop with 224 N ha-1. We concluded that growers that plant winter rye prior to corn could use precision planting at a seeding rate of 18.75 kg ha-1 to take up residual soil N with limited interference with corn production at a reduced cost compared to conventional winter rye management.

Tyrimai, siekiant išsiaiškinti, kaip keičiasi fotosintetinių rodiklių intensyvumas ir grūdų kokybė bei derlingumas priklausomai nuo augimo tarpsnio bei tręšimo azotinėmis trąšomis, atlikti 2009-2010 metais. Pigmentų ir tirpiųjų sacharidų kiekis tirtas Agrobiotechnologijos laboratorijoje, o grūdų kokybės rodikliai ištirti AB „Kauno grūdai“ laboratorijoje. Žieminiai kviečiai auginti Lietuvos žemės ūkio universiteto Bandymų stotyje, kur dirvožemis IDg8-k (LVg-p-w-cc) – karbonatingas sekliai glėjiškas išplautžemis (Calc(ar)i-Epihypogleyic Luvisols). Tyrimamas pasirinktos dvi žieminių kviečių veislės: labai gerų kepimo savybių ’Ada’ ir gerų kepimo savybių ’Tauras DS’. Buvo tiriama, kaip vegetacijos metu kinta pigmentų ir sacharidų kiekis augalų lapuose ir kaip azoto trąšos įtakojo baltymų, šlapiojo glitimo, sedimentacijos, krakmolo, kritimo skaičiaus pokyčius grūduose ir grūdų derlingumą. Azoto trąšos augaluose skatino bendrą pigmentų kiekio didėjimą, o tirpiųjų sacharidų kaupimuisi esminės įtakos neturėjo. Taip pat azoto trąšos beveik visuose variantuose patikimai skatino baltymų kaupimąsi grūduose, didino sedimentaciją ir šlapiojo glitimo kiekį, o krakmolo kiekis mažėjo atvirkščiai proporcingai baltymų kiekiui. Tręšimas azoto trąšomis visuose variantuose patikimai didino derlingumą. / The research was carried out in the period from 2009 to 2010 to determine the changes in the intensity of photosynthetic characteristics ,grain quality and yield, depending on the growth phase and fertilization with nitrogen fertilizer. The amount of pigments and soluble sugars was investigatd in the laboratory of Agrobiotechnology and the indicators of grain quality were explored in the laboratory of JSC „Kauno grūdai“. Winter wheat were grown in the Experimental Station of Lithuanian University of Agriculture, where the soil is IDg8 k (LVD-pw-cc) - calcareous shallow Luvisols (Calc (or) i Epihypogleyic Luvisols). Two varieties of winter wheat were selected for the experimental study: ’Ada’ with a very good baking properties and ’Tauras DS’ with good baking properties. The research focused on how vegetation changes affect the pigment and sugars content in the plant leaves, as well as the influence of nitrogen fertilizers on the grain yield and changes in content of protein, wet gluten, sedimentation and starch in the investigated grain. The results suggest that the nitrogenous fertilizers stimulated the overall growth of the cultivar, the pigment content but it had no significant effect on the accumulation of soluble sugars .Moreover, almost in all cases of the nitrogen fertilizer treatments it significantly promoted the accumulation of grain protein, increased sedimentation and wet gluten content however the starch content decreased inversely with the protein. The grain... [to full text]

A fixação biológica de nitrogênio (FBN) apresenta-se como uma alternativa sustentável e viável, na produção de gramíneas, através do uso de bactérias do gênero Azospirillum, um microrganismo potencial promotor do crescimento das plantas. Neste sentido, o presente trabalho foi realizado com o objetivo de estudar o efeito do uso da bactéria diazotrófica Azospirillum brasilense, inoculada via sementes, em associação ou não com doses de nitrogênio, na entressafra, no teor e rendimento de óleo em genótipos de milho. Os ensaios foram realizados em duas épocas de semeadura em um delineamento experimental de blocos casualizados (DBC) com 30 tratamentos e três repetições. Em cada época, os tratamentos foram dispostos em um esquema fatorial 2x3x5, representado por dois processos de inoculação das sementes (com e sem inoculação das sementes), três genótipos de milho (Orion e Al Bandeirante, variedades de polinização aberta, e o Híbrido Duplo (AG-1051) e cinco doses de nitrogênio N (0, 50, 100, 150 e 200 kg ha-1) realizadas em cobertura. Foram avaliadas o teor de óleo dos grãos (%) e o rendimento de óleo (kg ha-1). Foi realizada análise de variância individual e, posteriormente, análise conjunta. O uso da bactéria Azospirillum brasilense, acompanhada ou não de doses de nitrogênio, promoveu aumento no teor e no rendimento de óleo nos grãos. A variedade Orion foi a que mais se destacou quando inoculada com a bactéria Azospirillum, sendo também a mais eficiente quando cultivada sob baixo nitrogênio. A adoção desta prática não substitui o uso de fertilizantes nitrogenados, mas poderá ser uma alternativa para reduzir os custos do produtor. / Biological nitrogen fixation (FBN) is presented as a viable and sustainable in the production of grasses, through the use of bacterium of the genus Azospirillum, microorganisms potential plant growth promoter. In this sense, the present work was to study the effect of using the diazotrophic bacterium Azospirillum brasilense, inoculated in seeds, in association or not with nitrogen, in the off season, the content and oil yield in corn genotypes. The tests were performed at two sowing times in a randomized complete block design (DBC) with 30 treatments and three replications. In every age, the treatments were arranged in a factorial 2x3x5, represented by two seed inoculation processes (with and without seed inoculation) Three genotypes (Orion and Al Bandeirante, open-pollinated varieties, and the Hybrid Double (AG-1051) and five doses of nitrogen N (0, 50, 100, 150 and 200 kg ha-1) held in coverage. The grain oil content were evaluated (%) and oil yield (kg ha-1). individual variance analysis was performed and subsequently pooled analysis. The use of bacterium Azospirillum brasilense, with or without nitrogen, promoted an increase in content and oil yield in grains. The variety Orion was the one that stood out when inoculated with Azospirillum bacterium, and is the most efficient when grown under low nitrogen. The adoption of this practice does not replace the use of nitrogen fertilizers, but can be an alternative to reduce producer costs.

Com o objetivo de caracterizar a variação temporal de fitomassa seca de raízes, hastes, folhas e órgãos reprodutivos, e de verificar o efeito da adubação nitrogenada no rendimento de grãos e na produção de fitomassa seca dos diferentes órgãos da cultura de feijão (Phaseolus vulgaris L.) no florescimento, conduziu- se um experimento na área do Departamento de Produção Vegetal, Esalq, Universidade de São Paulo, Piracicaba-SP. O solo foi classificado como NITOSSOLO VERMELHO Eutroférrico; a variedade cultivada foi IAC-Carioca Tybatã (hábito de crescimento indeterminado), e o delineamento estatístico foi o inteiramente casualizado. Os tratamentos foram constituídos de combinações dos fatores doses de nitrogênio (0, 60 e 120 kg.ha -1 ) e épocas de avaliação (nove estádios feno lógicos). Os seguintes parâmetros foram avaliados: fenologia da cultura, a fitomassa seca de raízes, hastes, folhas e órgãos reprodutivos, em cada estádio fenológico, e o rendimento de grãos e seus componentes. Para descrever o padrão de variação da fitomassa seca de raízes, hastes, folhas, órgãos reprodutivos e fitomassa seca total, foram ajustados modelos não lineares utilizando o procedimento NLIN (Non LINear regression) do SAS â System (SAS Institute, 1998). De acordo com o que foi discutido, os resultados permitem concluir que: (i) os modelos propostos são adequados para caracterizar a variação de fitomassa seca de raízes, hastes, folhas e órgãos reprodutivos durante o ciclo da cultura de feijão (Phaseolus vulgaris L.), (ii) no florescimento e na colheita, a fitomassa seca dos diferentes órgãos da cultura de feijão e o rendimento de grãos, respectivamente, variam com a adubação nitrogenada segundo uma função quadrática, (iii) o máximo rendimento de grãos é obtido com a dose de 60 kg.ha -1 de nitrogênio, e (iv) a variação da fitomassa seca relativa em função do desenvolvimento relativo da cultura de feijão apresenta o mesmo padrão de comportamento independentemente da dose de nitrogênio, o que possibilita extrapolar e comparar resultados de experimentos cond uzidos em diferentes locais e épocas. / With the purpose of characterizing the temporal variation of the roots, stems, leaves and reproductive organs dry mass of the common bean (Phaseolus vulgaris L.), and of verifying the effect of nitrogen fertilization on its grain yield and dry mass accumulated into the different plant organs at flowering, an field experiment was carried out at Crop Science Department, Esalq, University of São Paulo, Piracicaba, Brazil. The soil was classified as Rhodic kandiustalfs; the cultivar was IAC-Carioca Tybatã (indeterminate genotype) and the statistical experimental design was completely randomized. The treatments were nitrogen doses (0, 60 and 120 kg.ha -1 ) associated with nine crop phenological stages. The following parameters were evaluated: crop phenology; roots, stems, leaves and reproductive organs dry mass for each phenological stage; and the grain yield and its components. Non linear models were used to describe the standard variation of roots, stems, leaves, reproductive organs and total dry mass using the NLIN procedure (Non LINear regression) of the SAS â System (SAS Institute, 1998). According to the discussion, the results allowed to conclude that: (i) the proposed models are appropriate to characterize the roots, stems, leaves and reproductive organs dry mass variation during the common bean (Phaseolus vulgaris L.) crop cycle, (ii) the dry mass of all organs and grain yield of common bean, in response to nitrogen fertilization at flowering and harvest, respectively, follow a quadratic function, (iii) the maximum grain yield is obtained with 60 kg.ha -1 of nitrogen, and (iv) the relative dry mass as function of the common bean development stage presents the same performance independently of the nitrogen dose, therefore, the results can be extrapolated and compared with data obtained in different situations.

Submitted by Gabriela Lopes (gmachadolopesufpel@gmail.com) on 2017-03-31T13:45:54Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Tais Barbosa Becker.pdf: 1060596 bytes, checksum: 0f90b7287d92bbaef370fc137f99cea5 (MD5) / Approved for entry into archive by Aline Batista (alinehb.ufpel@gmail.com) on 2017-04-24T13:09:51Z (GMT) No. of bitstreams: 2 Dissertação Tais Barbosa Becker.pdf: 1060596 bytes, checksum: 0f90b7287d92bbaef370fc137f99cea5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-04-24T13:09:51Z (GMT). No. of bitstreams: 2 Dissertação Tais Barbosa Becker.pdf: 1060596 bytes, checksum: 0f90b7287d92bbaef370fc137f99cea5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / A fase de produção de mudas é uma etapa importante dentro da cadeia produtiva do morangueiro, uma vez que as plantas em cultivo no solo precisam ser renovadas anualmente, devido ao acúmulo de doenças e pragas de um ano de cultivo para outro, acarretando em baixa produtividade. O estudo teve como objetivo avaliar o efeito da concentração de nitrogênio na produção e na qualidade de mudas envasadas (com torrão) produzidas a partir de matrizes suspensas cultivadas fora do solo e avaliar o comportamento dessas mudas no campo com diferentes datas de plantio para Pelotas-RS. Os fatores avaliados foram: cultivar (Aromas, Camarosa, Festival e Oso Grande), solução nutritiva (padrão ‘1’ e metade da quantidade de nitrogênio ‘2’) no experimento 1 e cultivar (Aromas, Camarosa, Festival e Oso Grande) e datas de plantio (16/03; 01/04 e 01/04) no experimento 2, conduzidos em área experimental pertencente a Embrapa Clima Temperado, em Pelotas, RS, durante os anos de 2015 e 2016. O sistema de produção de mudas fora do solo estudado neste período é eficiente, pois as cultivares Camarosa, Festival e Oso Grande expressam seu potencial produtivo, no que diz respeito ao elevado número de propágulos produzidos pela planta-matriz, obtido em Pelotas-RS. Além de fornecer plantas antecipadamente para a cadeia de produção. A menor quantidade de nitrogênio fornecida favorece maior produção de estolões e mudas por planta matriz. O plantio entre março e abril (precoce para a região, pois normalmente ocorre entre o final de maio e início de junho, quando as mudas importadas chegam aos produtores) é uma alternativa viável aos produtores, para obter uma produção precoce em um período em que o produto é mais valorizado. As produções obtidas são altas, e quanto mais antecipada a data de plantio maior a produção por planta, sendo 'Camarosa' e 'Festival' as cultivares mais produtivas nas condições do estudo. / The seedling production phase is an important step in the strawberry production chain, since the plants in soil cultivation need to be renewed annually, due to the accumulation of diseases and pests from one year of cultivation to another, resulting in low productivity. The study aimed to evaluate the effect of nitrogen concentration on the production and quality of botted plant produced from suspended matrices under cultivation soilless and assess the behavior of these seedlings in the field with different planting dates for the Pelotas-RS city. The evaluated factors were: cultivar (Aromas, Camarosa, Festival and Oso Grande), nutrient solution (standard '1' and half of the amount of nitrogen '2') in experiment 1 and cultivar (Aromas, Camarosa, Festival and Oso Grande), and planting dates (03/16, 04/01 and 04/16) in experiment 2, conducted in an experimental area belonging to Embrapa Clima Temperado, in Pelotas, RS, during the years of 2015 and 2016. The system of production of seedlings soilless studied in this period is efficient, because the cultivars Camarosa, Festival and Oso Grande express their productive potential, in relation to the high number of propagules produced by the matrix plant, obtained in PelotasRS. In addition to supplying plants in advance to the production chain. The smaller amount of nitrogen provided favors greater production of stolons and seedlings per plant. Planting between march and april (early for the region, normally occurs between the May late and early June, when the imported seedlings arrive to the growers) is a viable alternative to the growers, to obtain an early production and in a period in which the product is more valued and reach more profit. The early and total productions obtained are high, and how more anticipated the plantinning date is better production per plant is obtained, being 'Camarosa' and 'Festival' the most productive under the conditions of the study.

Thesis (M. Agricultural Management (Agronomy)) -- University of Limpopo, 2018 / A survey study identified indigenous leafy vegetables (ILVs) utilized by rural communities in Limpopo Province in the three districts of Capricorn, Sekhukhune and Vhembe focusing on their availability, agronomic practices, marketing, medicinal and cultural roles, as well as their nutritional value. An ILV that was highly preferred and with good marketing potential was identified for further studies on its response to planting density and nitrogen fertilizer rate. A questionnaire survey was used to gather information about types of ILVs utilised, their production practices, marketing of ILVs and their importance in medicinal and cultural roles. Data collected were subjected to analysis using the Statistical Package for Social Sciences (SPSS) using descriptive statistics. Results showed that there were 45 different types of ILVs identified from the three districts in Limpopo Province. Farmers indicated that cultivation of these vegetables was mostly done from October to January in Sekhukhune and Capricorn district while in Vhembe it was practiced all year round. Most of farmers in Vhembe district used inorganic fertilizer during planting while farmers in Sekhukhune and Capricorn districts used organic fertilizers such as cattle manure. Irrigation was commonly used in Vhembe district through furrow irrigation system whereas in Capricorn and Sekhukhune districts most farmers relied on rainfall. Farmers indicated that harvesting was done at an early growing stage of the crop. Indigenous leafy vegetables were mostly marketed in local communities. Several ILVs were identified as preferred and regularly consumed as vegetables. Spider plant (Cleome gynandra) and nightshade (Solanum retroflexum) were identified as the most consumed ILVs in the three districts. Comparing the market potential of the two vegetables, S. retroflexum was chosen for further studies on its response to plant density and nitrogen fertilizer rate. The first study investigated the effect of varying plant density (inter and intra-row spacing) and the second study evaluated the response of intra-row spacing and nitrogen fertilizer (LAN-28%N) rate on growth and yield of S. retroflexum during 2014 (April to May) and 2015 (March to May) growing seasons. The plant density experiment was laid out as a 3 x 4 factorial arrangement in a randomised complete block design (RCBD) with three replications. The treatment factors were 3 inter-row spacings of 30, 45 and 60 cm and 4 intra-row spacings of vi 7.5, 15, 22.5 and 30 cm. The data collected included plant height, plant vigour, number of leaves and branches per plant as well as plant leaf yield. Data were subjected to analysis of variance (ANOVA) using STATISTIX 10.0 package and mean treatments were separated using Turkey HSD at 5% probability level. The results revealed that growth parameters (plant height, plant vigour, number of branches and leaves) and plant leaf yield were significantly influenced by the combined inter and intra-row spacings. Closer inter-row spacings of 30 cm and 45 cm, and intra-row spacings of 7.5 and 15 cm produced the highest values of parameters and plant leaf yield. The combined spacings of 30 x 7.5 cm produced the highest plant leaf yield. The second study was also laid out as a randomised complete block design (RCBD) with three replications. The treatments were 6 x 2 factorial arrangement: 6 levels of nitrogen (LAN-28%N) at 0, 20, 40, 60, 80 and 100 kg N/ha and two intra-row spacings of 15 and 30cm. Inter-row spacing of 30 cm was used. The nitrogen fertilizer was applied a week after transplanting and repeated a week after first harvesting. Data was subjected to analysis of variance (ANOVA) using STATISTIX 10.0 package. Where significant differences were detected, means were separated using Turkey HSD at 5% propability level. The results suggested that both nitrogen fertilizer and spacing can be used to enhance growth and leaf yield of S. retroflexum vegetable. Nitrogen fertilizer rate and plant density significantly (P≤0.05) affected plant growth and plant leaf yields. Growth parameters and leaf yield were optimised using closer spacing of 15 cm and applying nitrogen at 60 kg N/ha. The application of 60 kg N/ha and 15 cm spacing was therefore recommended for the production of S. retroflexum as a vegetable, if planted at 30 cm inter-row spacing. Key words: Indigenous leafy vegetables, agronomic practices, Solanum retroflexum, planting density, nitrogen fertilizer, planting date