Resumo -O objetivo deste trabalho foi avaliar a interferência da adubação potássica em parâmetros fisiológicos de duas cultivares de soja, sob diferentes regimes hídricos. O experimento foi realizado em condições de casa de vegetação, em Presidente Prudente, SP. Utilizou-se o delineamento experimental inteiramente casualizado, em arranjo fatorial 2x2x3, com as cultivares BR-16 (tolerante ao estresse hídrico) e Embrapa 48 (suscetível), regimes hídricos com reposição diária de água de 100% (controle) e de 40% da capacidade de campo, e três níveis de suplementação com K (0, 90 e 180 mg dm -3). Duas semanas após a imposição da restrição hídrica, foram avaliados: conteúdo relativo de água, potencial fotossintético e rendimento de biomassa. As plantas que se desenvolveram sob restrição hídrica tiveram sua capacidade fotossintética reavaliada após 12 horas de reidratação. Em condições de restrição hídrica, a adubação potássica não interferiu significativamente nos parâmetros fisiológicos e de crescimento avaliados. A suplementação com potássio promoveu melhor eficiência dos parâmetros fisiológicos, no regime sem deficiência hídrica, nas duas cultivares, e as principais variáveis influenciadas pelo nutriente foram: condutância estomática, taxa máxima de carboxilação da Rubisco e assimilação máxima de CO 2 . A suplementação com K melhora a recuperação fotossintética das plantas após a reidratação, especialmente na cultivar Embrapa 48.Termos para indexação: Glycine max, biomassa, deficit hídrico, fotossíntese, nutrição. Physiological responses of soybean cultivars to potassium fertilization under different water regimesAbstract -The objective of this work was to evaluate the interference of potassium fertilization on the physiological parameters of soybean cultivars under different water regimes. The experiment was carried out in greenhouse at Presidente Prudente, SP, Brazil. The experimental design was a completely randomized block in a 2x2x3 factorial arrangement, with the soybean cultivars BR-16 (tolerante ...) and Embrapa 48 (suscept...), water regimes with daily replacements of 100% (control) and 40% of the field capacity, and three levels of K supplementation (0, 90, and 180 mg dm -3). Relative water content, photosynthetic potential, and biomass yield were evaluated two weeks after the initiation of water restriction. Plants grown under water restriction had their photosynthetic potential reevaluated after 12 h of rehydration. Under water restriction conditions, potassium fertilization did not significantly affect the assessed growth and physiological parameters. Supplementation with potassium promoted a better efficiency of the physiological parameters, in water deficit control, in both cultivars, and the main variables influenced by the nutrient were: stomatal conductance, maximum rate of Rubisco carboxylation, and maximum CO 2 assimilation. Potassium supplementation improves photosynthetic recovery of plants after rehydration, especially in the Embrapa 48 cultivar.Index terms: Glycine max, biomass, water deficit...

The objective of this work was to evaluate the nutrition, accumulation of nutrients in residual straw, pure seed yield, and seed quality of the tropical forage grasses 'Mombaça' and 'Xaraés' subjected to topdressing with nitrogen fertilizer management. Field experiments were carried out in the municipalities of Rancharia and Presidente Prudente, in the state of São Paulo, Brazil. The treatments included a control (without N topdressing) and four N fractionation forms at different forage stages: 150 kg ha-1 N, at the vegetative phase (VP); 150 kg ha-1 N, at the beginning of the reproductive phase (RP), between panicle initiation and the prebooting stages; 100 kg ha-1 N, at VP plus 50 kg ha-1 N at RP; and 50 kg ha-1 N at VP plus 100 kg ha-1 N at RP. Fertilization with N as topdressing, regardless of the N fractionation form, increased N concentration in the flag leaf and in residual straw, and the quantities of N accumulated by 'Mombaça' and 'Xaraés' forage grasses. The application of all or most N in the VP increased the quantities of residual straw and of P and K accumulated by the 'Mombaça' forage grasses. The application of all or most N in the RP provided a greater pure seed yield and N use efficiency in both forage grasses. The seed physiological quality of the forages is not affected by fertilization with N topdressing.

The objective of this work was to evaluate the effect of applying N sources to leaves and N rates to the soil on the growth, N uptake, and grain and crude protein yields of the common bean (Phaseolus vulgaris) crop. Three experiments -two irrigated and one rainfed -were conducted during the 2012/2013 agricultural season, in a randomized complete block design with four replicates. The treatments consisted of the application of: four N rates (0, 45, 90, and 180 kg ha -1 ) to the soil, as topdressing in the V 4 stage; and five N sources/rates -i.e., control, without foliar N application; 2.5 kg ha -1 N as conventional urea (N-CU); 5.0 kg ha -1 N-CU; 2.5 kg ha -1 N as slow-release urea-formaldehyde (N-SR); and 5.0 kg ha -1 N-SR -to leaves, in the R 5 stage. Soil N fertilization, using rates between 124 and 180 kg ha -1 , increases shoot N content and uptake, number of pods per plant, grain yield, and protein content and yield. Regardless of the growing environment and N application to the soil, the foliar supply of N as slow-release urea-formaldehyde increases grain and protein yields, whereas the greatest rate of N as conventional urea also increases grain yield. Aplicação de nitrogênio via foliar e em cobertura na cultura do feijoeiro comumResumo -O objetivo deste trabalho foi avaliar o efeito da aplicação de fontes de N via foliar e de doses de N via solo no crescimento, na absorção de N e na produtividade de grãos e de proteína bruta da cultura do feijão comum (Phaseolus vulgaris). Foram conduzidos três experimentos -dois em condição irrigada e um em sequeiro -no ano agrícola 2012/2013, em delineamento de blocos ao acaso, com quatro repetições. Os tratamentos consistiram da aplicação de: quatro doses de N via solo (0, 45, 90 e 180 kg ha -1 ), em cobertura, no estádio V 4 ; e cinco fontes/doses de N via foliar -i.e., testemunha, sem N via foliar; 2,5 kg ha -1 de N na forma de ureia convencional (N-UC); 5,0 kg ha -1 de N-UC; 2,5 kg ha -1 de N na forma de ureia-formaldeído de liberação lenta (N-LL); e 5,0 kg ha -1 de N-LL -, no estádio R 5 . A adubação nitrogenada via solo, com doses entre 124 e 180 kg ha -1 , aumenta o teor e o acúmulo de N na parte aérea, o número de vagens por planta, a produtividade de grãos, e o teor e a produtividade de proteína. Independentemente do ambiente de cultivo e da aplicação de N via solo, o fornecimento de N na forma de ureia-formaldeído de liberação lenta via foliar aumenta a produtividade de grãos e de proteína, enquanto a aplicação da maior dose de N na forma de ureia convencional também aumenta a produtividade de grãos.Termos para indexação: Phaseolus vulgaris, adubação foliar, adubação nitrogenada, liberação lenta, ureiaformaldeído.

Nitrogen (N) fertilization management can affect the seed yield and quality of tropical forage grasses. Studies have shown the effect of N rates on tropical grass seed production, but no study has evaluated the effect of application timing of N on the N use efficiency (NUE) and seed yield and quality of creeping signalgrass [Urochloa humidicola (Rendle) Morrone & Zuloaga, syn. Brachiaria humidicola (Rendle) Schweick.]. Field experiments were conducted over two growing seasons in Santo Anastácio, São Paulo, Brazil, to evaluate the influence of N fertilization timing on plant nutrition, herbage mass, N uptake, NUE, and seed yield and quality of creeping signalgrass ‘Llanero’. The treatments included a control (no N application) and four treatments with N applied at different times (150 kg N ha−1 during the vegetative phase, 150 kg N ha−1 at panicle initiation [prebooting], 100 kg N ha−1 during the vegetative phase plus 50 kg N ha−1 at panicle initiation, and 50 kg N ha−1 during the vegetative phase plus 100 kg N ha−1 at panicle initiation). Topdressed N fertilization increased the concentration of N in the flag leaf by 35.9% (from 12.2 to 16.6 g kg−1) and increased the herbage N uptake by 99.7% (from 72 and 144 kg ha−1). Herbage mass was not affected by topdressed N fertilization. The greatest seed yield (64.2% or 136 kg ha−1 greater than the control, and an average of 22.5% or 64 kg ha−1 greater than the other N treatments) was observed in response to 100 kg N ha−1 applied during the vegetative phase plus 50 kg N ha−1 applied at panicle initiation, which resulted in improved NUE. Seed viability was greater in the treatments where all or most of the N was applied at panicle initiation. In addition, the seed germination percentage was positively affected by N fertilization, regardless of the N application timing.

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The cycle and grain yield of bean crops can be influenced by several factors, among them sowing season and bean cultivar. The objective of this work is to evaluate the development, production components, and grain yield of common bean cultivars in function of sowing seasons. The experiment was conducted at the Experimental Farm of Universidade do Oeste Paulista in the municipality of Presidente Bernardes, São Paulo state, in 2016. The experimental design was randomized blocks in a 4 x 4 factorial design with four replications. The treatments were four sowing seasons (SS1 -April 12; SS2 -May 14; SS3 -June 11; and SS4 -July 14), and four common bean cultivars (BRS Estilo, BRS Pérola, BRS Requinte, and IPR Campos Gerais). The phenological stages V4, R6 and R9, plant height, plant population, number of pods per plant, mass of 100 grains, and grain yield were influenced by sowing seasons and bean cultivars. The highest grain yields for the cv. BRS Estilo, BRS Requinte and IPR Campos Gerais were obtained at SS2. However, for the cv. BRS Pérola, it occurred at SS4. At SS1, the highest grain yield was obtained by the cv. BRS Estilo, and other sowing seasons by the cv. BRS Pérola.

Nitrogen (N) is the nutrient most required by common bean, and the response to N fertilization may be variable among genotypes. The objective of this work was to evaluate the N nutrition, grain yield, grain size, and crude protein concentration of common bean cultivars in response to topdressing N rates. Two experiments were conducted on a Typic Rodudalf, under two growth conditions ("dry" and "rainy" seasons). A randomized complete block design with a 7 × 4 factorial arrangement and four replicates was used. The treatments consisted of seven cultivars (Pérola, BRS Ametista, BRS Notável, IPR Campos Gerais, IPR Tangará, IAC Formoso, and IAC Imperador) and four N rates (0, 35, 70, and 140 kg ha-1). The experiments were analyzed jointly. The application of N did not affect the cycle, plant population, and number of grains per pod, but increased the leaf N concentration, number of pods per plant, grain size, and grain yield, regardless of the cultivar. The responses of common bean cultivars to N rates varied according to the growth condition, with response to N only in the "rainy" season experiment, under conditions of lower N and higher C/N ratio in the straw of the preceding crop. The crude protein concentration in the grains was influenced in an inconsistent manner by the factors studied.

Soil acidity and low concentrations of exchangeable Ca and Mg are among the main factors that limit the Arabica coffee (Coffea arabica L.) yield in Brazil. Constant fertilizations, especially with ammonium‐based N, contribute to acidification in the soil region where they are applied. Coffee producers wonder if limestone and phosphogypsum, isolated or combined, can increase coffee yields. A field experiment was conducted from 2015 to 2020 in southeastern Brazil to evaluate the effect of sole application of limestone and phosphogypsum, or their combined application to young coffee trees (2‐yr old), on plant nutrition, yield, and profitability of Arabica coffee crop. Treatments included three limestone rates (0, 2,100, and 4,200 kg ha−1), two phosphogypsum rates (0 and 2,300 kg ha−1), and their combinations, which were band applied under coffee plant canopy. Limestone, in association with phophogypsum or when sole‐applied, increased the pH and the concentration of Ca and Mg in the soil, whereas the application of phosphogypsum increased Ca and SO4–S concentration. Coffee yields were increased by the sole application of limestone and phosphogypsum (to a lesser extent), but not when they were combined. The most successful treatment was the sole application of limestone, with increases of up to 44% (613 kg ha−1 yr−1 on average) in yield and 43% in economic returns.