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 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 Objetivou-se com este trabalho avaliar a eficiência de recuperação de nitrogênio (N), fósforo (P) e potássio (K) pela cultura da cenoura. Foram implantados dois experimentos em área de cultivo localizada em Rio Paranaíba - MG. A cultivar "Juliana" foi semeada no período de verão e a cultivar "Nayarit" no período do inverno. Os tratamentos consistiram de seis combinações de fertilizações N-P2O5-K2O (kg ha-1): sem N (0-500-450), sem P (100-0-450), sem K (100-500-0), padrão (100-500-450), maior que o padrão (100-700-600) e menor que a padrão (100-300-300). A colheita foi realizada quando a maior parte das raízes apresentavam-se dentro do padrão comercial mais aceito pelos consumidores. Quantificaram-se as matérias fresca e seca das raízes e das folhas e com base na matéria fresca de raízes calculou-se a produtividade. Determinaram-se os teores de N, P e K em folhas e raízes por ocasião da colheita e com bases nesses teores e na matéria seca de raízes e de folhas determinaram-se a absorção e a exportação de nutrientes. As fertilizações testadas influenciaram a produtividade comercial de ambas as cultivares. A omissão da fertilização com N, com P ou com K reduziu a produtividade da cultivar "Juliana". Para a cultivar "Nayarit" apenas a omissão de P reduziu a produtividade. Para essa cultivar o incremento de P e K aumentou a produtividade. A cultivar "Nayarit", mais produtiva que "Juliana", absorveu maiores quantidades de N, P e K. As eficiências de recuperação desses nutrientes por ambas cultivares de cenoura foram baixas.

ABSTRACT The objective of this work was to evaluate the carrot crop recovery efficiency of nitrogen, phosphorus and potassium from fertilizers. Two experiments were conducted in an experimental area in Rio Paranaiba - MG. The cultivar ("Juliana‟) was sown during the summer period and the cultivar "Nayarit‟ during the winter period. In both experiments, the treatments consisted of six fertilization combinations of N, P2O, K2O (kg ha-1): fertilization without N (0-500-450), without P (100-0-450), without K (100-500-0), standard (100-500-450), higher than standard (100-700-600) and lower than standard (100-300-300). The harvest was carried out when most of the roots presented commercial standard well accepted by the consumers. The fresh and dry matter of roots and leaves were quantified, and the yield was calculated based on the fresh matter. The analysis of N, P and K contents in leaves and roots were carried out by harvest time, and the nutrients absorption and exportation were determined based on these contents and on the dry matter of roots and leaves. N, P and K omissions reduced the yield of the cultivar "Juliana‟. For the cultivar "Nayarit‟, only P omission reduced and P and K fertilizations increased the yield. The cultivar "Nayarity‟, which is more productive than "Juliana", absorbed more quantities of N, P and K. Carrot recovery efficiency of nitrogen, phosphorus and potassium is low.

ABSTRACT Leaf analysis may identify nutrient deficiency or excess in plant tissue. The aim of this study was to determine reference values and generate nutritional diagnosis from the results of leaf analysis of the carrot crop (Daucus carota L.) by the methods of Critical Level, Sufficiency Range, Diagnosis and Recommendation Integrated System, and Compositional Nutrient Diagnosis. Contents of N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn were determined in 210 carrot fields in the 2012 and 2013 crop seasons in the Alto Paranaíba region, MG, Brazil. The whole plant shoot was sampled at harvest time to generate reference values for diagnosis. The high yielding subpopulation showed yield higher than 87.8 Mg ha-1. The four diagnostic methods generated similar reference values of nutrients, but different from those found in the literature. Leaf diagnosis through nutrient content in the shoot at harvest time indicated Mn as the most limiting nutrient for growing carrot, followed by Mg, K, and Ca.

A escolha da cultivar de cenoura deve ser planejada cuidadosamente pelo agricultor para o sucesso da exploração da cultura. O potencial produtivo da cultivar pode influenciar a demanda de nutrientes e deve ser conhecido para estabelecer o plano de fertilização. Objetivou-se, com este trabalho, avaliar o efeito de cultivares sobre a produtividade de cenoura, o teor e as quantidades alocadas de nutrientes em folhas e raízes. Foram implantados três experimentos em duas épocas de cultivo em Rio Paranaíba, MG. Na primeira época, caracterizada como verão típico, foram semeadas 10 cultivares de verão. Na segunda, evidenciada como verão-inverno (transição), instalaram-se dois experimentos, um com cultivares de verão; e outro, de inverno. Os tratamentos consistiram das cultivares de cenoura, distribuídos em blocos casualizados, com quatro repetições. Quantificaram-se a matéria fresca e a seca de raízes e folhas. Com base na matéria fresca de raízes, calculou-se a produtividade. Determinou-se o teor de nutrientes em folhas e raízes por ocasião da colheita. Calcularam-se, com bases nesses teores e na produção de matéria seca de raízes e folhas, a absorção e exportação de nutrientes. A maior média de produtividades total e comercial ocorreu no cultivo em condições de verão. A extração de N e K para a maioria das cultivares nos três experimentos superou as quantidades aplicadas via fertilizantes. Assim, houve contribuição dos nutrientes no solo para obter as produtividades alcançadas. Entretanto, para o P, a quantidade absorvida foi consideravelmente menor que a aplicada. Isso implicou que o solo teve sua fertilidade aumentada em P, após o cultivo. A época de cultivo e as cultivares influenciaram a produtividade, os teores de nutrientes nas folhas e raízes, a extração e a exportação de nutrientes pela cultura da cenoura.

Farmers must carefully choose the cultivar to be grown for a successful carrot crop. The yield potential of the cultivar may influence nutrient demand and should be known to plan for fertilization application. The aim of this study was to evaluate the cultivar effect on carrot yield and on the nutrient content and quantities allocated to leaves and roots. Three experiments were set up in two crop seasons in Rio Paranaíba, MG, Brazil. In the first season, typical summer, 10 summer cultivars were sown. In the second season, summer-winter (transition), two experiments were set up, one with summer cultivars and the other with winter cultivars. The treatments consisted of the carrot cultivars distributed in randomized blocks with four replications. Fresh and dry matter of the roots and leaves was quantified. Yield was calculated based on fresh matter of the roots. The nutrient content in leaves and roots was determined at the time of harvest. These contents and the dry matter production of roots and leaves were used to calculate nutrient uptake and export. The greatest average for total and commercial yield occurred in the crop under summer conditions. Extraction of N and K for most of the cultivars in the three experiments went beyond the amounts applied through fertilizers. Thus, there was contribution of nutrients from the soil to obtain the yields observed. However, the amount of P taken up was considerably less than that applied. This implies that soil P fertility will increase after cropping. The crop season and the cultivars influenced yield, nutrient content in the leaves and roots, and extraction and export of nutrients by the carrot crop.

Inocular sementes de trigo com Azospirillum brasilense pode ser benéfico à cultura do trigo, bem como reduzir a necessidade de aplicação de N. No entanto, são escassos trabalhos que mensurem o benefício dessa prática no trigo irrigado com expectativa de alta produtividade e demanda de N. Objetivou-se com este trabalho avaliar a produtividade e o conteúdo de N na planta do trigo irrigado, submetido a doses de N, com ou sem a inoculação com A. brasilense. Foram conduzidos dois experimentos em 2011 e repetidos em 2012. Em cada ano de cultivo, instalou-se um experimento na área considerada de baixa disponibilidade de N no solo (cultivo em sucessão ao milho) e outro na com alta disponibilidade (cultivo em sucessão à soja ou cenoura). Os tratamentos consistiram de cinco doses de N e da inoculação ou não com A. brasilense. As doses de N testadas foram 20, 60, 100, 140 e 180 kg ha-1 na área com baixa disponibilidade de N e 20, 50, 80, 110 e 140 kg ha-1 na com alta disponibilidade. O teor de N na folha índice foi aumentado pela inoculação com A. brasilense. Entretanto, o N absorvido não foi influenciado pela inoculação da bactéria. As doses de N aumentaram a produtividade do trigo e esse aumento foi mais evidente no cultivo na área com baixa disponibilidade de N no solo.

Inoculating wheat seeds with nitrogen-fixing bacteria such as Azospirillum brasilense may be beneficial to the crop and reduce the need for N application. Nevertheless, few studies have measured the benefit of this practice on irrigated wheat with the expectation of high yield and demand for N. The objective of this study was to evaluate the yield and N content of irrigated wheat under different N application rates, with and without inoculation with A. brasilense. Two experiments were carried out in 2011 and reevaluated in 2012. In each crop year, one experiment was set up in an area with low N availability in the soil (growing in succession to maize) and another with high availability (growing in succession to soybean or carrots). The treatments consisted of five N application rates, and inoculation or no inoculation with A. brasilense. The N rates tested were 20, 60, 100, 140, and 180 kg ha-1 in the area with low N availability, and 20, 50, 80, 110, and 140 kg ha-1 in the area with high N availability. Yield, grains per spike, dry matter accumulation in the shoots, N content in the index leaf and in the grain, and N uptake and export were evaluated. The N content in the index leaf increased through inoculation with A. brasilense, However, the N taken up was not affected by inoculation of the bacteria. The N applied increased wheat yield, and this increase was more evident in the area with low N availability in the soil.