Soils originating from the Caiuá sandstone formation have low soil organic matter (SOM), clay content, and cation exchange capacity (CEC). The predominance of one component over the other might decisively influence the CEC of these soils. Particle size distribution and selective dissolution procedures associated to a suit of methods to determine the exchangeable capacity properties might clarify the relative importance of each soil component. The objective of this work was to evaluate the contribution of the different components of the solid fraction and their intrinsic attributes to the CEC of sandy-loam soils and their relation to the total organic carbon (TOC), C:N ratio, and soil mineralogy. For this purpose, 34 soil samples were selected from the Caiuá sandstone formation with significant variation in the carbon content. Clay size fraction was characterized by X-ray diffraction, routine chemical analysis, and total specific surface area-SSA T using EGME, before and after the removal of SOM with sodium hypochlorite solution. Different values of CEC and effective cation exchange capacity (ECEC) were determined following standard procedures. The soils presented high sand content (82.9 ± 5.9 %) and the mineralogy of the clay fraction is dominated by kaolinite (>80 %) with the presence of illite, 2:1 clay minerals, and small amounts of iron and aluminum oxides. The CEC and ECEC values at pH 7.0 and ~5.6, respectively due to the SOM are 408.6 and 148.7 cmol c kg-1 of carbon, respectively. The SOM was responsible for 32 to 84 % (average 52 %) and 24 to 67 % (average of 46 %) of the CEC and ECEC of the soils, respectively. The CEC and ECEC of the inorganic fraction are 2.32 and 0.78 cmol c kg-1 of minerals, respectively. The CEC of the clay fraction increased with the TOC but decreased exponentially with the clay content. The total carbon content increased linearly with the C/N ratio. The SSA T showed a significant (p<0.05) and positive correlation with the TOC and with the CEC of the soils.

A utilização de lodo industrial inorgânico em substratos comerciais ou como fonte de nutrientes, é prática bem recente. O lodo produzido pela indústria de galvanoplastia-zincagem apresenta elevados teores de nutrientes como Zn, Fe, e Ca que, dependendo das doses utilizadas em solos e substratos, podem causar toxidez às plantas. No presente experimento foi utilizado um substrato comercial onde foram adicionadas doses crescentes do lodo industrial de galvanoplastia-zincagem para o cultivo de crisântemo, variedade Rage, em cultivo protegido. As doses do lodo industrial utilizadas foram de 0,0; 0,38; 0,75; 1,50; 3,0; 6,0; 9,0 e 12,0 g L-1 de substrato. Após 12 semanas de cultivo foram avaliadas as seguintes variáveis: pH e condutividade elétrica do substrato, teor de Zn na parte aérea da planta e no substrato, altura da planta (ALT), massa seca da parte aérea (MSPA), massa seca das inflorescências (MSF) e massa seca do sistema radicular (MSR). A adição do lodo industrial no substrato, na dose de 0,38 g L-1, promoveu um pequeno incremento de ALT, MSPA e MSR. Este comportamento indica que o lodo industrial pode fornecer nutrientes à cultura. Nas doses superiores a 3 g L-1 ocorreu acentuada queda da produção devido ao desbalanço nutricional associado à fitotoxidez de Zn e elevada condutividade elétrica do substrato.

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.

Adequate plant nutrition is very important to soybean and cotton crops to express its potential production. Among plant nutrients, potassium (K) plays an important role in plants to achieve high yields. Potassium fertilization is an important tool for soybean and cotton high yields achieving because K absence reduces foliar K content and plant growth. Several strategies have been used to increase the efficiency of K fertilization. Among them, the use of enhanced efficiency K fertilizers has been studied more often recently. Owing to the lack of information related to the use of enhanced K fertilizers, the present study aimed at evaluating potassium leaching and soybean and cotton K foliar content, yield and agronomic efficiency in response to K rates and sources. To evaluate K leaching, a factorial 310 (three K sources and 10 irrigations levels) was carried out, under greenhouse conditions. Three soybean field trials and one cotton field trial were carried out to evaluate soybean K foliar content, soybean 100-grain weight, cotton 10balls weight, K agronomic efficiency and yield. Increasing irrigation levels increased potassium leaching, which was mitigated by the Policote coated K fertilizer. Potassium fertilization increased soybean and cotton yields. Higher potassium agronomic efficiency index with Policote coated KCl explained higher yields obtained with this enhanced efficiency K fertilizer. Results show that Policote coated fertilizer is a more efficient way to deliver required potassium to plants. The use of enhanced efficiency fertilizers is an emerging technology to increase the potassium use efficiency of crops in the field. The observed changes in potassium use efficiency among potassium fertilizers increased our understanding of enhanced efficiency fertilizers.

The citrus blackfly Aleroucanthus woglumi Ashby, (Hemiptera Aleyrodidae) is an important pest that occurs in citrus groves, native to south-east Asia. In Brazil, according to the Ministry of Agriculture, this is a quarantine pest (A2) under official control IN 52, 2007 (MAPA) and is not widespread in the country. The insect can infest more than 300 host plants, including cultivated plants, ornamentals and weeds, but mostly occurs in the plants of the genus citrus. This paper is the first report of citrus blackfly in the State of Paraná.