ROBERTO DOS ANJOS REIS JÚNIOR 2 e PAULO CEZAR REZENDE FONTES 3RESUMO -Com o objetivo de avaliar o efeito de época de amostragem e da adubação potássica sobre a morfologia e partição de assimilados na batateira (Solanum tuberosum L.), foram realizados dois experimentos no campo: o primeiro para avaliar o efeito de doses da adubação potássica e o segundo para avaliação do seu efeito residual. Foram aplicadas seis doses de K no campo (0, 60, 120, 240, 480 e 960 kg de K 2 O ha -1 ) na forma de sulfato de potássio, em delineamento de blocos casualizados, com quatro repetições. Tubérculos da cultivar Baraka, uniformemente brotados, foram plantados em espaçamento 0,8 x 0,3 m. Amostraram-se plantas aos 20 e 48 dias após emergência (DAE) para avaliação de área foliar, comprimento de caule, números e produções de matéria fresca e seca de folha, caule e tubérculo e teores de matéria seca de folha e caule. Apenas o comprimento de caule aumentou com as doses de K, resultando em menor sombreamento da batateira. No primeiro experimento, aos 20 DAE, a batateira apresentava, em média, 42 folhas, três hastes, 5.389 cm 2 de área foliar, 157,1 e 216,4 g de matéria fresca de caule e de folha, respectivamente, e 6,2 e 9,2% de teor de matéria seca de caule e de folha, respectivamente.Termos para indexação: Solanum tuberosum, nutrição mineral, produção de matéria fresca, produção de matéria seca. POTATO MORPHOLOGY AND DRY MATTER PARTITION IN RESPONSE TO SAMPLING TIME AND K LEVELSABSTRACT -This study was conducted in order to evaluate potato (Solanum tuberosum L.) morphology and dry matter partition in response to sampling time, K levels and its residue. Six K levels (0, 60, 120, 240, 480 and 960 kg K 2 O ha -1 ) were applied in the field as potassium sulfate, in randomized blocks design, repeated four times. Baraka potato tubers were seeded spaced 0.8 x 0.3 m. Plants were sampled at 20 and 48 days after its emergence (DAE) to estimate leaf area, stem length, number and fresh and dry matter yield of leaf, stem and tuber, and dry matter content of leaf and stem. Only stem length increased with K fertilization, resulting in smaller overshadow of plant. In the first experiment, at 20 DAE, potato was presenting, in media, 42 leaves, three stems, 5,389 cm 2 of leaf area, 157.1 and 216.4 g of fresh matter of stem and leaf, respectively, and 6.2 and 9.2% of dry matter content of stem and leaf, respectively.
Soybeans and maize are the most cultivated crops in tropical soils and require large amounts of phosphate fertilizers. The use of enhanced-efficiency fertilizers is a promising technology to minimize losses of P by fixation in highly weathered tropical soils. The objectives of this study were to evaluate morphological characteristics, soybean P and boron foliar content, yield and agronomic efficiency of P fertilizer in response to P rates and sources in maize and soybean crops. Two P fertilization experiments with the sources Mono-ammonium Phosphate (MAP) and Policote coated MAP were carried out, one in maize (0, 20, 40, 80, 120 and 160 kg P2O5 ha-1) and another in soybean crop (0, 20, 40, 80 and 120 kg P2O5 ha-1). The morphological characteristics, soybean P and boron foliar content, yield and agronomic P fertilizer efficiency were evaluated. The results showed that maize and soybean morphological characteristics, as well as soybean foliar P and boron contents were not influenced by fertilization. P fertilization increased soybean yield. Policote coated MAP was more efficient than MAP (conventional fertilizer) to produce higher maize and soybean yields and higher agronomic efficiency of P use. For higher productivity, we recommend the dose of 102.9 kg P2O5 ha-1 of Policote coated MAP for soybean and 97.6 kg P2O5 ha-1 for maize.
Nitrogen fertilizer has a significant participation in the cost of agricultural production. It is less efficient agronomically and requires more studies to find strategies to be absorbed by crop. Polymer-coated urea is an alternative for the production of increased efficiency fertilizers. Validation of this technology should be performed for safe adoption in agriculture. The objectives of this work were to evaluate the nitrogen losses by volatilization of ammonia and the nitrogen contents in the nitric (N-NO3-) and ammoniacal (N-NH4+) forms in the tropical soil after application of urea sources. Three greenhouse experiments with different soil moisture conditions were carried out after application of urea, urea treated with NBPT and urea coated with Policote polymer as treatments. Then volatilization of ammonia, N-NO3- and N-NH4+ contents in the soil was evaluated. The volatilization of ammonia was observed after using Policote-coated urea, which was similar to urea treated with NBPT. However, both of which were lower than that observed under urea application. In dry or very humid soil, the ammonia volatilization rate was low. The reduction of the volatilization of ammonia in the soil with Policote-coated urea was related on the humidity, whereas more effective when the conditions were more propitious to the volatilization of ammonia. The Policote-coated urea increased the content of N-NH4+ in the tropical soil compared to urea. The content of N-NH4+ in the soil was higher than N-NO3- after application of fertilizers due to the low organic matter content.
The Brazilian Savanna (Cerrado) ecosystem concentrates most of the area under cotton cultivation in the country, and is characterized, predominantly, by low fertility soils. Nitrogen (N) is the most extracted nutrient from the soil by most crops, while sulfur (S) fertilization has been little explored in studies with cotton plants. This study aimed to evaluate the effects of N and S fertilization on the N content of leaf, weight of 30 bolls, productivity, and agronomic efficiency of cotton plants grown in an Oxisol from the Brazilian Cerrado region. Two independent field experiments were carried out simultaneously in a completely randomized block design with four replications. The first experiment was composed of five levels of N (17, 100, 150, 200 and 250 kg ha -1 ) and the second with five levels of S (24, 50, 75, 100 and 125 kg ha -1 ). The leaf N content of the cotton plants increased linearly with the supply of up to 250 kg ha -1 of N in the soil. The weight of 30 bolls and the seed-cotton productivity were considerably increased with the increase of the N and S levels in the soil. The maximum agronomic efficiency of the N and S fertilization was obtained with the application of 150 and 100 kg ha -1 of N and S, respectively. Therefore, this study clearly showed the positive effects of the adequate fertilization of N and S on the productivity of cotton in soils from the Brazilian Cerrado region.Key words: boll, fertilization, Gossypium hirsutum, leaf content, low fertility soil Produtividade e eficiência agronômica do algodoeiro em resposta ao suprimento de nitrogênio e enxofre RESUMO A região de Cerrado do Brasil, onde se concentra a maior parte da área de algodão plantada no País, possui, predominantemente, solos de baixa fertilidade. O nitrogênio (N) é o nutriente mais extraído do solo pela maioria das culturas enquanto a adubação com enxofre (S) tem sido pouco explorada em estudos com algodoeiro. O objetivo deste estudo foi avaliar os efeitos da adubação nitrogenada e sulfatada sobre o teor foliar de nitrogênio, peso de 30 capulhos, produtividade e eficiência agronômica, em algodoeiro cultivado em um Latossolo da região de Cerrado Brasileiro. Dois experimentos de campo, independentes, foram conduzidos simultaneamente em delineamento em blocos completos casualizados, com quatro repetições, em que o primeiro experimento foi composto por cinco níveis de N (17, 100, 150, 200 e 250 kg ha ). O teor de N nas folhas do algodoeiro aumentou de forma linear com o fornecimento de até 250 kg ha -1 de N no solo. O peso de 30 capulhos e a produtividade de algodão em caroço foram incrementados consideravelmente com o acréscimo dos níveis de N e S no solo. A máxima eficiência agronômica das adubações nitrogenada e sulfatada foi obtida com a aplicação de 150 e 100 kg ha -1 de N e S, respectivamente. Este estudo mostrou claramente os efeitos positivos da fertilização adequada de N e S sobre a produtividade do algodoeiro em solos da região de Cerrado do Brasil.Palavras-chave: capulho, fertilização, Gossypium hirsutu...
Urea fertilizers coated with polymers are used to optimize nitrogen (N) uptake by crops. However, there are many types of polymers that can be used for coating, leading to differences in observed results. Consequently, validation of this technology to guarantee its viability in agriculture is necessary. The objective of this study was to evaluate effects of ammonium- and nitrate-N levels in the soil, maize yield and nutritional status, N fertilization efficiency with Policote® urea coating, and different N doses under various soil and climatic conditions. Three field experiments were carried out to compare the performance of common urea with Policote® coated urea. A (2 x 4) + 1 factorial design with two N sources (common urea and Policote® coated urea), four N doses, and a control treatment (without N) was used. The results showed that Nitrate-N levels in the soil were not affected by the treatments. However, the ammonium-N levels was increased with N fertilization. Higher levels of soil ammonium-N contents were observed in treatments with Policote® coated urea. Foliar nitrogen levels were increased linearly with N doses only in one of the experiments. Nitrogen fertilization significantly increased maize yield. Higher yield and N fertilization efficiency were observed in treatments with Policote® coated urea than with common urea.
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