ABSTRACT. In no-till (NT), liming and urea fertilization are performed on the soil surface, which can increase nitrogen (N) losses via ammonia volatilization. On the basis of N fertilization management, gypsum application provides a promising alternative for improving N uptake by plants. Therefore, the objective of this study was to evaluate the N behavior loss by NH3-N volatilization, the soil pH at a depth of 0 - 0.05 m, leaf N content, and N uptake by second-season corn after lime and gypsum application in a Rhodic Ferralsol under NT. Overall, the treatments consisted of a 4 × 4 factorial arrangement with four lime rates (0, 2.6, 5.4, and 8.1 Mg ha-1) and four gypsum rates (0, 4, 8, and 12 Mg ha-1). During the study period, second-season corn was cultivated for two years and fertilized with urea, for which the N losses through ammonia volatilization, soil pH, leaf N content, and N uptake values were quantified. The losses through ammonia volatilization were subjected to nonlinear regression using a logistic model, and the other variables were subjected to linear regressions. The lime applied by broadcasting on the soil surface in the NT increased the pH of the topsoil and increased N losses via NH3-N volatilization in the second-season corn. Further, the N losses in the NT treated with lime accounted for 58% of the applied N, which increased by 2.3 to 2.5% for each Mg ha-1 of lime applied. Therefore, lime or gypsum application did not improve the status of N in second-season corn in soils with low acidity and no S deficiency.

ABSTRACT Oxisols ( Latossolos ) are widely distributed in tropical zones and generally characterized by high levels of surface and subsurface acidity. In Brazil, most Oxisols are managed under no-till conditions with surface application of acidity amendments. This study aimed to evaluate lime application strategies (incorporated and surface) for achieving the desired soil base saturation (BS%) levels (44, 60, 70, and 90 %) and the effect of phosphogypsum + lime application on soil chemical properties as well as wheat and corn yield in southern Brazil. Lime incorporation was more effective in reducing the soil acidity and increasing Ca2+ and Mg2+ despite a decrease in organic matter at the soil surface. Phosphogypsum application increased S-SO42- and Ca2+ availability throughout the deeper soil layers and reduced the Mg2+ content in the surface layer. Wheat yield under incorporated lime conditions increased with BS% up to 75, but there was no response to surface application. When phosphogypsum was applied, the wheat yield increased by 8.4 %. For corn, incorporated lime increased the yield up to 445 kg ha-1, which was equivalent to the yield after phosphogypsum application. An increase in the S-SO42- level was the main factor related to the increase in crop yields. In the short term, our results suggest that phosphogypsum applied along with lime is more appropriate than incorporating lime under no-till management conditions.

Resumo: Alternativas para evitar perdas e impactos desnecessários no meio ambiente são alcançadas no manejo agrícola. A preparação de sementes com nanofertilizantes antes do plantio reduz as preocupações com a dispersão não-alvo; no entanto, formulações e concentrações devem ser cuidadosamente selecionadas para evitar efeitos indesejados. Aqui, avaliou-se a germinação e o desenvolvimento de plântulas após a iniciação das sementes com CuO NPs, CuO bulk e CuCl2. As sementes foram imersas em soluções primárias de 0, 20, 40, 80 e 160 mg.L-1 para as três fontes de Cu. Após 8 horas de preparação, as sementes foram avaliadas quanto à germinação e vigor (primeira contagem de germinação). Os comprimentos de raiz e parte aérea foram medidos, bem como a biomassa seca de parte aérea e de raízes. A fonte de nanopartículas de cobre não apresenta efeitos tóxicos no crescimento do milho e promove maior biomassa quando comparada às demais fontes. Por outro lado, fontes de CuCl2 mostraram alguns impactos negativos tóxicos nas raízes e parte aérea do milho para todas as doses testadas. Esses achados apoiam o tratamento de sementes com NPs como uma alternativa à entrega de micronutrientes essenciais, como o cobre.

Abstract: Fertilizer formulation alternatives that avoid unnecessary losses and environmental impacts are being investigated in agricultural management. Seed priming with nanofertilizers prior to planting, reduces concerns about non-target dispersion; however, priming formulations and concentrations must be carefully selected to avoid undesired effects. Here, seed germination and seedling development were evaluated after seed priming with CuO nanoparticles (NPs), CuO bulk and CuCl2. The seeds were immersed in priming solutions of 0, 20, 40, 80 and 160 mg.L−1 Cu for the three Cu sources. Following 8 hours priming, the seeds were evaluated for germination and vigor (first germination count). Root and shoot lengths were measured as well as shoot and root dry biomass. The copper NP did not show any toxic effects on corn seed germination and growth, and also promoted higher biomass when compared to the other Cu sources. On the other hand, CuCl2 primed seeds exhibited Cu-toxicity in roots and shoots for all concentrations tested. Bulk Cu priming results indicated the better role of NPs size effects. These findings support NP-seed priming as an alternative to delivery of essential micronutrients, such as copper, to corn seedlings.

Baixos teores de matéria orgânica no solo podem limitar o desenvolvimento da soja, devido a baixa disponibilidade de enxofre (S) no solo e pela alta demanda deste nutriente pelas plantas. Uma alternativa para complementar esta necessidade é a aplicação S foliar. O objetivo foi avaliar o efeito da aplicação de fertilizante foliar à base de enxofre na cultura da soja, em diferentes épocas e doses. Os tratamentos foram: (1) 0,0 kg ha-1 de S foliar; (2) 0,5 kg ha-1 de S foliar no estágio de início do florescimento (R1); (3) 0,5 kg ha-1 foliar no estágio de início do enchimento de grãos (R5.1); (4) 0,5 kg ha-1de S foliar nos estádios R1 e R5.1; (5) 1 kg ha-1de S foliar no estádio R1; (6) 1 kg ha-1de S foliar no estádio R5.1; (7) 1 kg ha-1de S foliar nos estádios R1 e R5.1, delineados em blocos ao acaso com 4 repetições. As variáveis respostas foram: massa de mil grãos, produtividade e teores de macro e micronutrientes nos grãos. A produtividade dos grãos aumentou 614 kg ha-1 com aplicação de S foliar em relação à testemunha. A dose que obteve a melhores resultados foi de 0,5 kg ha-1 aplicado nos estádios R3 ou R5.1. A utilização de enxofre elementar via foliar pode ser uma alternativa de complementação.

Low levels of organic matter in soil may limit the soybean crop development due to the low availability of sulfur (S) and the high demand of this nutrient by plants. The foliar fertilization is an alternative to supplement plant request. This study aimed at assessing the effect of applying foliar sulfur fertilizer in the soybean at different time and doses. The treatments studied were: (1) 0.0 kg ha-1 of S foliar; (2) 0.5 kg ha-1 of foliar S in beginning bloom (R1) stage; (3) 0.5 kg ha-1 of foliar at beginning seed (R5.1) stage; (4) 0.5 kg ha-1 of foliar S in R1 and R5.1; (5) 1 kg ha-1 of foliar S in R1; (6) 1 kg ha-1 of S foliar in R5.1; (7) 1 kg ha-1 of foliar S in R1 and R5.1 using randomized block design with 4 replicates. The variables analyzed were: one thousand grain mass, yield and the macro and micronutrient contents in the grains. The soybean yield increased 614 kg ha-1 with the application of foliar sulfur in relation to the control. The dose that obtained the best results was 0.5 kg ha-1 applied into the R3 or R5.1 stage. The use of elemental sulfur via foliar may be an alternative of sulfur supplementation.

ABSTRACT Brazilian soybean producers commonly apply maintenance potassium (K) fertilization during cultivation to restore the K taken up by plants; however, this measure can modify the morphophysiological plant characteristics, since the functions of K are closely related with plant growth and development. This study assessed the morphological changes in soybean plants in response to K rates, sowing fertilization, and the application periods of K fertilization in a Latossolo Vermelho eutroférrico (Oxisol) under a no-tillage system, located in the municipality of Floresta, Paraná. A randomized block design was used in the experiment with four replications in a fully crossed factorial design (5 × 2 × 2). The experiment was carried out in two growing seasons (2015/2016 and 2016/2017), with a total of 80 experimental units. The rates corresponded to the first factor (0, 40, 80, 120, and 160 kg ha-1 of K). The application periods (pre-sowing and post-sowing) were the second factor, and sowing fertilization (0 and 30 kg ha-1 of K) the third. The following variables were measured: shoot dry weight, leaf dry weight, stem dry weight, leaf area, specific leaf area, leaf area ratio, and leaf area index, and these biometric parameters were correlated with soybean yield. The results showed that plants well-supplied with K exploited the environment better and this may be reversed for higher yields since there were correlations between grain yield and the biometric parameters. At lower water availability, the biometric changes were more evident.