ABSTRACT. The objective of this work was to study the biomass production and chemical composition of the different parts of the cassava plant during the first and second vegetative cycles, with the aim of providing data that can contribute to the understanding of the response of cassava cultivars to different harvest ages. The experimental design consisted of randomized blocks in split plot scheme. Plots were represented by cultivars IAC 90 and IAC 118-95 and subplots by crop age (2, 4, 6, 8, 10, 12, 14, 16, and 18 months after planting). Our results showed that the ‘IAC 90’ allocated a higher proportion of assimilates to the leaves, stem and planted cutting than the ‘IAC 118-95’, which was more efficient in allocating dry matter to the storage roots. Storage roots showed an increase of more than 50% in starch content 14 months after planting. The cultivar IAC 118-95 is distinguished by the higher harvest index, allowing earlier harvesting, with possible valorisation of the leaves as industrial raw material. Variables showed different degrees of inter-relationships amongst themselves. Total plant fresh matter and dry matter yields were positively correlated with growth parameters and root starch for both cultivars. Harvest time and cultivar are key factors that should be considered to increase profits in the cassava agro-industrial chain. ABSTRACT cycles ages scheme 9 11895 118 95 118-9 2, 2 (2 4 6 8 10 12 16 1 planting . planting) 11895, , 118-95’ 50 index harvesting material interrelationships inter relationships themselves agroindustrial agro chain 1189 11 118- ( 5

Abstract BRS Boitatá and BRS Ocauçu cassava cultivars for the industry have high root and starch yields and high starch contents in first-cycle and second-cycle harvests, medium tolerance to the main diseases, adequate architecture for mechanized planting and stability in starch contents. firstcycle first cycle secondcycle second harvests diseases

ABSTRACT: The application of zinc fertilizers in the soil has been an agronomic practice to correct Zn deficiency in plants, aiming to increase productivity and/or nutritional quality. This study evaluated how zinc sulfate fertilization affects plant growth, yield performance and nutrient accumulation in the cassava ‘IAC 576-70’. The experimental design was in randomized blocks with eight replications. The treatments consisted of 0, 1.5, 3.0, 4.5 and 6.0 g p1-1 ZnSO4. Results showed improvement in yield with soil fertilization with ZnSO4, with the optimal dose of 2.5 g pl-1. The uptake of nutrients in plant parts is favored with lower doses of zinc fertilizer, with maximum points ranging from 0.8 to 3.2 g pl-1 for macronutrients and 1.6 to 3.6 g pl-1 for micronutrients. The Zn content in tuberous roots increases by more than 40% with fertilization up to 2.8 g pl-1 of fertilizer, which contributes to the nutritional value of roots. ABSTRACT plants andor or quality growth IAC 57670. 57670 576 70 . 576-70’ replications 0 15 1 5 1.5 30 3 3.0 45 4 4. 60 6 6. p11 p p1 p1- ZnSO4 ZnSO 25 2 2. pl1. pl1 pl 1. fertilizer 08 8 0. 32 3. pl- 16 36 micronutrients 40 28 5767 57 7 576-70 576-7 576-

RESUMO: A aplicação de fertilizantes com zinco no solo tem sido uma prática agronômica para corrigir a deficiência de Zn nas plantas, visando aumentar a produtividade e/ou a qualidade nutricional. O objetivo deste estudo foi avaliar como a fertilização com sulfato de zinco afeta o crescimento da planta, o desempenho produtivo e o acúmulo de nutrientes na mandioca ‘IAC 576-70’. O delineamento experimental foi em blocos casualizados com oito repetições. Os tratamentos consistiram de 0, 1,5, 3,0, 4,5 e 6,0 g p1-1 ZnSO4. Os resultados mostraram melhoria no rendimento com a fertilização via solo com ZnSO4, com a dose ótima em 2,5 g pl-1. A absorção de nutrientes nas partes da planta é favorecida com menores doses de fertilizante de zinco, com pontos de máximo variando de 0,8 a 3,2 g pl-1 para macro e 1,6 a 3,6 g pl-1 para micronutrientes. O conteúdo de Zn nas raízes tuberosas tem aumento superior a 40% com a fertilização até 2,8 g pl-1 de fertilizante, o que contribui para o valor nutricional da mandioca. RESUMO plantas eou ou IAC 57670. 57670 576 70 . 576-70’ repetições 0 15 1 5 1,5 30 3 3,0 45 4 4, 60 6 6, p11 p p1 p1- ZnSO4 ZnSO 25 2 2, pl1. pl1 pl 1. 08 8 32 3, pl- 16 1, 36 micronutrientes 40 28 5767 57 7 576-70 576-7 576-

RESUMO O rendimento médio nacional da batata-doce está abaixo do potencial produtivo da cultura, principalmente devido ao cultivo de variedades locais e não melhoradas que apresentam baixos rendimentos. Para melhorar essa condição, junto com tratamentos culturais adequados, deve-se buscar cultivares mais produtivas. Assim, objetivou-se caracterizar genótipos de batata-doce obtidos por meio de cruzamentos. O experimento foi conduzido de janeiro a maio de 2019 em Selvíria, Mato Grosso do Sul, Brasil. O delineamento experimental foi em blocos casualizados com 264 (genótipos) + Controle (‘Beauregard’), com duas repetições. A colheita de todas as plantas começou 127 dias após o plantio dos propágulos. Após a colheita, as raízes foram lavadas e colocadas para secar em área coberta para avaliação. Foram avaliados: rendimento total, comercial e não comercial; número total, comercial e não comercial da raiz; teor de matéria seca de raízes; e a produtividade de matéria seca. Os genótipos CERAT16-20, CERAT31-1 e CERAT21-2 são promissores para a produção de raízes para consumo doméstico devido à alta produtividade das raízes comerciais. Os acessos CERAT16-20, CERAT31-1, CERAT25-17, CERAT25-12, CERAT21-2, CERAT29-26, CERAT34-4, CERAT31-11 e CERAT24-8 são promissores para a indústria devido à alta produção de massa seca por hectare. Os componentes principais, número total de raízes comerciais, produção de raízes não comerciais, massa de raízes comerciais, produção total de massa seca de raízes, massa de raízes e produção total de raízes têm baixa contribuição para discriminação dos genótipos, portanto, sua análise pode ser descartada em trabalhos futuros, sob mesmas condições edafoclimáticas, reduzindo o trabalho, despesas e tempo.

ABSTRACT The average national sweet potato yield of Brazil falls below the productive potential of the crop because of the cultivation of local and unimproved varieties. To improve this, more productive cultivars must be adopted along with adequate culture treatments. This study was conducted between January and May 2019 in Selvíria, Mato Grosso do Sul, Brazil, to characterize sweet potato genotypes obtained through crossbreeding. The experimental design consisted of randomized blocks containing 264 genotypes, the control (‘Beauregard’), and two replicates. Plant harvesting began 127 d after planting. After harvesting, the roots were washed and dried in a covered area ready for evaluation. The total, commercial, and non-commercial yield; total, commercial, and non-commercial root number; root dry matter content; and dry matter productivity were evaluated. The genotypes CERAT16-20, CERAT31-1, and CERAT21-2 are promising in terms of root production for household consumption because of their high productivity of commercial roots. In contrast, genotypes CERAT16-20, CERAT31-1, CERAT25-17, CERAT25-12, CERAT21-2, CERAT29-26, CERAT34- 4, CERAT31-11, and CERAT24-8 are promising for industry because of the high production of dry mass per hectare. The main components, total number of commercial roots, production of non-commercial roots, mass of commercial roots, total production of dry mass of roots, mass of roots, and total production of roots have a low contribution to the discrimination of the genotypes; therefore, their analysis can be discarded in future studies, under the same soil and climate conditions, thus reducing workload, expense, and time.

ABSTRACT This study evaluated the effects of the rates and timings of prohexadione-calcium (prohexadione-Ca) application on shoot growth, tuber yield, and quality of two potato cultivars (Agata and Mondial). An experiment with each cultivar was carried out in a greenhouse using a randomized block design with four replications. Treatments consisted of a control and single or sequential foliar applications of prohexadione-Ca at the rate of 50 or 100 g ha-1 (50 g ha-1 applied once, 50 g ha-1 applied twice, 50 g ha-1 applied three times, 100 g ha-1 applied once, 100 g ha-1 applied twice, and 100 g ha-1 applied three times). Prohexadione-Ca application changed the distribution pattern of tuber size in both cultivars. A rate of 100 g ha-1 prohexadione-Ca was applied three times between the stages of tuber initiation and tuber bulking, making the haulm length of the plants short for a long time. Prohexadione-Ca application did not alter the tuber yield and quality of the cultivar Agata, but 50 g ha-1 applied three times or 100 g ha-1 applied twice increased tuber yield in the cultivar Mondial. Only in the cultivar Mondial, 50 g ha-1 prohexadione-Ca applied three times increase tuber dry matter, starch, and protein contents.

ABSTRACT The excess of nitrogen (N) causes the overgrowth of sweet potato foliage, increasing the self-shading and reducing the root yield. Therefore, a combined N and paclobutrazol (PBZ) application can reduce the vegetative overgrowth and benefit the sweet potato yield. The purpose of this study was to evaluate the plant growth, yield, uptake and removal of N by sweet potato plants fertilized with N and treated with PBZ during two planting seasons. The treatments consisted of four N rates (0, 50, 100 and 200 kg·ha–1), three forms of PBZ application (PBZ-10: PBZ applied at 10 days after side-dressing N fertilization [DASNF]; PBZ-25: PBZ applied at 25 DASNF, and PBZ-10 + 25: PBZ applied at 10 plus 25 DASNF), and a control (without PBZ application). Paclobutrazol application temporarily reduced the length of the main branches of sweet potato planted in the rainy season, but it did not reduce the shoot biomass of plants in both planting seasons. A single application of PBZ at 10 DASNF increased the yield of fresh storage roots in the two planting seasons, but, during the rainy season, the increases were greater when two applications were carried out. The application of 50 kg·ha–1 N in the rainy season was sufficient to reach the maximum yield of fresh storage roots, but, in the dry season, the N fertilization increased the N uptake without benefiting the root yield.

ABSTRACT Phosphorus (P) is one of the most difficult nutrients for plants to acquire because of its low content in the soil solution. Cassava (Manihot esculenta Crantz) has a thick and sparse absorbent root system; therefore, it is dependent on its association with arbuscular mycorrhizal fungi (AMF) for P acquisition from the soil. Thus, inoculation of cassava with AMF can improve the development of this root crop. This study evaluated the effects of soil disinfection (disinfected vs. natural) and the spore rates of Rhizophagus clarus inoculation (0, 50, 100 and 200 spores per plant) in greenhouse conditions on the initial growth, yield, P acquisition, and P use efficiency of cassava, as well as to evaluate the contribution of the native AMF to P acquisition from the soil. For cassava production in P-deficient soil, inoculation with Rhizophagus clarus significantly increased cassava growth, P uptake, and storage root yield only when the soil was disinfected. When the soil is not disinfected, native AMF contributes up to 86 % of the P taken up by cassava. However, high spore rates of Rhizophagus clarus in natural soil cause detrimental consequences for native AMF by reducing the colonization of the absorbent roots. Therefore, for cassava grown in natural soil under greenhouse conditions, a rate of 50 spores per plant of Rhizophagus clarus is sufficient to promote a 14.5 % increase in the yield of fresh storage roots. A management strategy that favors the native AMF multiplication in the soil is a potential strategy to improve P uptake and yield of cassava in P-deficient soils.

ABSTRACT Sweet potato crops take up large amounts of nutrients, especially nitrogen. In low-fertility soils, the addition of nitrogen (N) increases the sweet potato yield. Green manure may be an alternative method for improving soil quality and supplying nutrients to this crop. This study aimed to evaluate the plant’s nutritional status and the amount of nutrients taken up and removed by sweet potato plants subjected to green manure and mineral N fertilization. The experiment was carried out in the field for two growing seasons using a randomized block design in a split-plot scheme with four replications. The plots consisted of a control treatment (spontaneous weeds) and the previous cultivation of Crotalaria spectabilis and Mucuna aterrima. The subplots consisted of four N rates (0, 50, 100, and 200 kg ha-1) that were applied to the sweet potato. The species M. aterrima is more suitable for use as green manure in the sweet potato than C. spectabilis. Nitrogen application rates promoted a greater increase in the biomass of the storage root, nutrient uptake, and removal in the sweet potatoes unfertilized with green manure. In the sweet potato fertilized with M. aterrima, mineral N supply in excess (above 50 kg ha-1) increases the nutrient uptake and removal without a significant increase in the biomass of the storage root. In the sweet potatoes unfertilized with green manure, high rates of N (greater than 120 kg ha-1) must be applied to obtain the utmost biomass of the storage root, nutrient uptake and removal.

Resumo: O objetivo deste trabalho foi avaliar o efeito de substâncias húmicas (SH) e adubo fosfatado sobre o crescimento, a absorção de fósforo (P), a produtividade de tubérculos, a recuperação do P do fertilizante (RPF) e a eficiência de uso do P aplicado (EUPA) de batateira (Solanum tuberosum) cultivada em um solo arenoso e em um argiloso. Em ambos os solos, o experimento foi realizado em delineamento de blocos ao acaso, em arranjo fatorial 4×3, com quatro repetições. Os tratamentos consistiram de quatro doses de P (0, 100, 200 e 400 kg ha-1 de P2O5) e de três de SH (0, 50 e 300 L ha-1). A adubação fosfatada aumentou a absorção de P e a produtividade de tubérculos da cultura da batateira em ambos os solos. As características do solo condicionaram o efeito da aplicação de SH. No solo arenoso, com menor conteúdo de matéria orgânica do que no solo argiloso, a aplicação de SH aumenta a absorção de P e a RPF, bem como proporciona maior produtividade de tubérculos e maior EUPA, especialmente na ausência de P ou em aplicação com dose reduzida de P. No solo argiloso, a aplicação de SH não afeta a resposta da cultura da batata à adubação fosfatada.

Abstract: The objective of this work was to evaluate the effect of humic substances (HS) and phosphorus fertilizer on the growth, P uptake, tuber yield, fertilizer P recovery (FPR), and applied P-use efficiency (APUE) of potato (Solanum tuberosum) cultivated in a sandy and in a clayey soils. In both soils, the experiment was carried out in a randomized complete block design, in a 4×3 factorial arrangement, with four replicates. The treatments consisted of four P rates (0, 100, 200, and 400 kg ha-1 P2O5) and of three HS rates (0, 50, and 300 L ha-1). Phosphate fertilization increased the P uptake and tuber yield of potato in both soils. Soil characteristics conditioned the effect of the addition of HS. In the sandy soil, with a lower content of organic matter (OM) than the clayey soil, the addition of HS increases the P uptake and FPR, besides providing a greater tuber yield and APUE, especially under the P absence or with the application of a reduced P rate. In the clayey soil, HS does not affect the response of potato to P fertilization.

RESUMO A batata (Solanum tuberosum L.) é uma cultura nutricionalmente exigente e o fósforo (P) é um dos nutrientes que exerce grande efeito sobre a produtividade de tubérculos. Porém, como a disponibilidade de P é influenciada pela textura do solo, existem dúvidas de como o fornecimento de P afeta o crescimento e a produtividade das plantas de batata em solos de texturas diferentes. Assim, objetivou-se com esta pesquisa avaliar o efeito da adubação fosfatada e da textura do solo na nutrição, crescimento, produtividade e eficiência de uso (EU) do P das plantas de batata. O experimento foi conduzido em casa de vegetação no delineamento de blocos casualizados em esquema fatorial 4×2, com cinco repetições. Os tratamentos foram representados por quatro doses de P (10, 50, 100 e 200 mg dm-3 P) e duas texturas de solo (argiloso e arenoso). Os teores foliares de P, Ca e Mg foram maiores no solo arenoso e as doses de P aumentaram os teores de N, P e Ca nas folhas. A adubação fosfatada aumentou o crescimento das plantas, a quantidade de P acumulada na parte aérea e a produtividade de tubérculos em ambos os solos, porém, de forma mais expressiva e até maiores doses na batata cultivada no solo argiloso. A EU do P aplicado não foi afetada pela textura do solo. Na batata cultivada no solo arenoso, a EU do P absorvido foi reduzida em função da diminuição na produção de MS e aumento nos teores de P nos órgãos da planta com fornecimento de altas doses de P.

ABSTRACT Potato (Solanum tuberosum L.) is a nutritionally demanding crop, and phosphorus (P) is a nutrient that exerts a large effect on tuber yield. However, as the availability of P is influenced by soil texture, there are doubts about how P supplementation affects the growth and yield of potato plants in different soil textures. Thus, here we aimed to evaluate the effect of P fertilization and soil texture on the nutrition, growth, tuber yield, and P use efficiency (PUE) of potato plants. The experiment was conducted under greenhouse conditions in a randomized block design with a 4×2 factorial scheme and five replications. The treatments were represented by four P rates (10, 50, 100, and 200 mg dm-3 P) and two soil textures (clayey and sandy). The concentrations of P, Ca, and Mg in the leaves were higher in sandy soil, and P rates increased the concentrations of N, P, and Ca in the leaves of potato plants. Phosphorus fertilization increased plant growth, the amount of P accumulated in the shoot, and tuber yield in both soils; this trend was stronger in the potato cultivated in the clayey soil than in the sandy soil. The applied-PUE was not affected by soil texture. In the potato cultivated in the sandy soil, the taken up-PUE was reduced due to the decrease in dry matter production and an increase in P concentration in the organs of the plant with higher P fertilizer rates.

ABSTRACT Studies in the past decades have focused on how tuber yield of potato grown on different types of soil is affected by phosphate fertilizer rates. However, little is known about the effects of phosphorus availability in the soil and of phosphate fertilization on nutrient uptake and removal by the main potato cultivars currently grown in Brazil. Thus, in this study we investigated the influence of P fertilization rates on dry matter (DM) yield and nutrient uptake and removal in five potato cultivars grown on soils with different levels of P availability. Experiments were conducted on soil with low (14 mg dm-3), medium (36 mg dm-3), and high (70 mg dm-3) P availability, in randomized complete blocks with a 5 × 5 factorial arrangement with four replications. The treatments consisted of five potato cultivars (Agata, Asterix, Atlantic, Markies, and Mondial) and five P rates (0, 125, 250, 500, and 1,000 kg ha-1 P2O5) applied in the planting furrow. In soils with low, medium, and high P availability, P fertilization increased plant growth and tuber DM yield up to rates of 500, 250, and 125 kg ha-1 P2O5, respectively. At a specific initial P availability, all potato cultivars responded to the same P rate for plant growth, tuber yield, and nutrient uptake and removal. At the highest P fertilization rates, leaf analysis showed that the nutritional status of potato plants was not significantly changed and no nutritional deficiency was induced, regardless of the soil P availability levels. However, in the soils with higher P availability, P fertilization decreased plant Mn and Zn and tuber Mn concentrations in a linear manner. The increases in the uptake of N, K, Ca, Mg, S, B, Cu, and Fe and the removal of most nutrients in response to P fertilization were related more to the increase in plant biomass and tuber DM yield than to changes in concentrations of these nutrients in the plant. Application of P at high rates in soil with high P availability caused luxury P uptake, which reduced Mn uptake by 10 % and prevented higher Zn uptake, by reducing plant Zn concentrations, despite the increase in plant biomass.

RESUMO: O nitrogênio (N) é o segundo nutriente mais absorvido pela mandioquinha-salsa. No entanto, ainda existem dúvidas sobre a influência que esse nutriente pode exercer sobre o crescimento da planta e a qualidade das raízes de reserva. Assim, objetivou-se com este trabalho avaliar a influência da adubação nitrogenada no crescimento da planta e na qualidade físico-química e nutricional das raízes de mandioquinha-salsa. O experimento foi conduzido em um Latossolo Vermelho distrófico de textura arenosa, no delineamento experimental de blocos ao acaso, com quatro repetições. Os tratamentos foram constituídos pelas doses de 0, 50, 100 e 200kg ha-1 de N. O crescimento das partes vegetativas da planta de mandioquinha-salsa aumentou linearmente com a adubação nitrogenada, mas a massa média e a produtividade das raízes de reserva aumentaram até as doses estimadas de 121 e 148kg ha-1 de N, respectivamente. A adubação nitrogenada aumentou os teores de amido e de proteína das raízes e diminuiu os teores de açúcares totais, porém, sem influenciar a qualidade nutricional delas.

ABSTRACT: Nitrogen (N) is the second most absorbed nutrient by Arracacha. However, there are still doubts about the influence that this nutrient can have on plant growth and the quality of the storage roots. Thus, the aim of this research was to evaluate the influence of nitrogen fertilization on plant growth and physical-chemical and nutritional quality of storage roots of Arracacha. The experiment was conducted on an Oxisol of sandy texture, in a randomized complete block design, with four replications. The treatments consisted of rates of 0, 50, 100, and 200kg ha-1 N. Growth of vegetative parts of Arracacha increased linearly with nitrogen fertilization, but the storage root mean weight and the yield of storage roots increased up to estimated rates of 121 and 148kg ha-1 N, respectively. Nitrogen fertilization increased the starch and protein content of the storage roots and reduced the content of total sugar, but without affecting the nutritional quality of the same.

ABSTRACT Modern high-yielding rice cultivars possibly take up and remove greater quantities of macronutrients than traditional and intermediate cultivars. This study was carried out with the aim of evaluating the extraction and removal of macronutrients by upland rice cultivars. These information are of utmost importance for the correct fertilizer management. The treatments consisted of three upland rice cultivars (Caiapó, a traditional type; BRS Primavera, an intermediate type; and Maravilha, a modern type). Macronutrient accumulation by rice cultivars up to the end of tillering (46 DAE) accounted for only 25 % of the total N and P, and between 35-45 % of the total K, Ca, Mg, and S; after that time, accumulation was intensified. In all of the cultivars, the period of greatest nutrient uptake occurred from 45 to 60 DAE for K, Ca, Mg, and S, and after 65 DAE for N. Phosphorus was taken up at greater rates at 70 DAE by the cultivar BRS Primavera and after 90 DAE by the cultivars Caiapó and Maravilha. The cultivars of the traditional (Caiapó) and intermediate (BRS Primavera) groups took up greater amounts of Ca (143 kg ha-1), Mg (46-53 kg ha-1), and S (45-52 kg ha-1), but amounts of N (147-156 kg ha-1) and P (18-19 kg ha-1) were similar to those of the cultivar of the modern group (Maravilha). Caiapó cultivar took up more K (245 kg ha-1) than other cultivars (204-207 kg ha-1). The cultivars Caiapó and Maravilha showed similar grain yield (4,157 and 4,094 kg ha-1); however, this was lower than the grain yield of cultivar BRS Primavera (6,010 kg ha-1). Cultivars with greater yield levels did not necessarily exhibit a greater uptake and removal of nutrients per area, even if they had greater capacity for conversion of the nutrients taken up into the biomass.

ABSTRACT Upland rice cultivars manifest different nutritional demands. A field study was conducted to quantify the extraction, distribution, and removal of micronutrients and silicon by the upland rice cultivars. The experiment was arranged in a randomized complete block-split plot design. Plots consisted of three cultivars (Caiapó – traditional, BRS Primavera – intermediate, and Maravilha – modern) of upland rice. Split-plots consisted of plant samplings, which occurred at 39, 46, 55, 67, 75, 83, 92, 102, 111, 118, and 125 days after emergence (DAE). Up to the end of tillering (46 DAE), all cultivars exhibited low demand for most micronutrients and Si, and took up less than 24 % of the total B, Cu, and Si, but around 31 % of the total Zn. The period of greatest uptake of micronutrients and Si occurred from 65 to 80 DAE in the Caiapó and BRS Primavera cultivars, and after 80 DAE in the Maravilha cultivar. The Caiapó and BRS Primavera cultivars took up their necessary demand of B, Mn, and Fe in the first 98 DAE and Cu, Zn, and Si up to 105 DAE, but the Maravilha cultivar took up these nutrients for two to three weeks longer. The quantities of micronutrients and Si taken up by cultivars Caiapó, BRS Primavera, and Maravilha did not exhibit large differences, and these cultivars took up between 98-135 g B, 103-110 g Cu, 1,157-1,460 g Fe, 1,278-1,424 g Mn, 240-285 g Zn, and 111-124 kg Si per hectare. The BRS Primavera cultivar showed greater removal of nutrients, with average amounts per hectare of 19.7 g B, 25.8 g Cu, 200 g Fe, 234.2 g Mn, 102.4 g Zn, and 32.6 kg Si, while the other cultivars removed smaller amounts per hectare (14.4 g B, 19.9 g Cu, 160.7 g Fe, 136.3 g Mn, 67 g Zn, and 21.9 kg Si). The BRS Primavera showed a greater removal of nutrients because it has a higher yield and allocates a greater quantity of nutrients to the panicles.

RESUMO: O crescimento excessivo da parte aérea do feijoeiro pode aumentar o acamamento das plantas e promover fechamento muito rápido da cultura, limitando a produtividade de grãos. O uso de reguladores de crescimento, como o ácido 2,3,5-triiodobenzoico (TIBA), pode reduzir o crescimento das plantas, porém, não existem informações sobre o uso dessa tecnologia na cultura do feijão. Objetivou-se com este trabalho avaliar o efeito de doses de TIBA (0, 8, 16, 32, 64 e 128g do i.a. ha-1) sobre o crescimento e a produtividade de grãos de duas cultivares de feijão ('IAC Alvorada' e 'IAC Jabola'). O delineamento experimental foi o de blocos ao acaso, em esquema de parcelas subdivididas, com quatro repetições. A aplicação de TIBA reduziu o comprimento da maior haste de ambas as cultivares, até a dose média estimada de 100g ha-1 de TIBA. A altura de inserção da primeira vagem foi reduzida apenas na cultivar IAC Alvorada até a dose de 88g ha-1 de TIBA. A aplicação de TIBA reduziu em 10% o número de grãos por vagem. A utilização de TIBA não afetou a produtividade de grãos, sendo uma alternativa para diminuir o porte das plantas de feijão.

ABSTRACT: The excessive aboveground growth of common bean can increase plant lodging and promote very rapid canopy closing, limiting grain yield. The use of growth regulators, such as 2,3,5-triiodobenzoic acid (TIBA), can reduce plant growth, however, there is no information on the use of this technology in the common bean crop. The objective of this study was to evaluate the effect of TIBA rates (0, 8, 16, 32, 64, and 128g a.i. ha-1) on growth and grain yield of two common bean cultivars ('IAC Alvorada' and 'IAC Jabola'). The experimental design used was randomized blocks, in a split plot scheme, with four replications. The application of TIBA reduced the stem length of both cultivars, to the average estimated rate of 100 g ha-1 TIBA. Height of insertion of the first pod was reduced only in IAC Alvorada up to rate of 88 g ha-1 TIBA. Application of TIBA reduced by 10% the number of grains per pod. The use of TIBA did not affect grain yield, being an alternative to reduce the size of the common bean plants.