RESUMO O objetivo do trabalho foi avaliar o efeito de diferentes doses de NPK nos componentes de produção do híbrido de mamão papaia 'Caliman 01'. O experimento foi realizado na empresa WG Fruticultura, localizada na região da Chapada do Apodi. Cinco doses de nitrogênio (75, 590, 837, 1088 e 1575 kg N ha-1), cinco doses de fósforo (10, 72, 96, 133 e 195 kg P2O5 ha-1) e cinco doses de potássio (527, 752, 978 e 1429 kg K2O ha-1), foram combinados de acordo com a matriz experimental Pan Puebla II, em 16 combinações e distribuídos em delineamento de blocos ao acaso, com cinco repetições. As parcelas foram constituídas por seis plantas, sendo avaliadas as quatro plantas centrais. Como fontes de N, P e K foram utilizados os fertilizantes ureia, fosfato monoamônico e cloreto de potássio, respectivamente. As doses de N e K foram divididas em trinta aplicações, uma a cada duas semanas. As doses de fósforo foram divididas em duas aplicações, a primeira aos 75 dias após o transplante (DAT) e a segunda aos 150 DAT. A produção de frutos foi avaliada durante oito meses. As doses de NPK que proporcionaram os melhores resultados em termos de produtividade foram 1088, 72 e 527 kg ha-1, respectivamente. O aumento das doses de N aumentou linearmente o número de frutos por planta e a produtividade, enquanto o aumento das doses de P e K reduziu o rendimento segundo modelos quadrático e linear, respectivamente. A combinação de doses de NPK 590, 72, 75 kg ha-1 proporcionou os melhores resultados econômicos com maior taxa de retorno na produção de mamão.

ABSTRACT The study aimed to evaluate the effect of different NPK doses on the yield components of papaya hybrid 'Caliman 01'. The experiment was carried at the company WG Fruticultura, located in the Chapada do Apodi region. Five nitrogen doses (94, 590, 837, 1088 and 1575 kg N ha-1), five phosphorus doses (10, 72, 96, 133 and 195 kg P2O5 ha-1) and five potassium doses (75, 527, 752, 978 and 1429 kg K2O ha-1), were combined according to the experimental matrix Pan Puebla II, in 16 combinations and distributed in a randomized block design, with five repetitions. The plots consisted of six papaya plants and the four central plants were evaluated. The fertilizers urea, monoammonium phosphate and potassium chloride were used as NPK sources, respectively. The doses of N and K were split into 30 applications, one every two weeks. Phosphorus doses were split into two applications, the first at 75 days after transplantation (DAT) and the second one at 150 DAT. Fruit production was evaluated during eight months. The best results were obtained for NPK doses of 1088, 72 and 527 kg ha-1, respectively. Increasing N doses linearly increased the number of fruits per plant and yield, while increasing P and K doses reduced yield by a quadratic and linear model, respectively. The combination of NPK doses 590-72-75 kg ha-1 provided the best economic results with the highest rate of return for papaya production.

RESUMO O presente trabalho teve como objetivo avaliar a adsorção de fósforo (P) e as mudanças ocorridas nas concentrações das formas orgânicas e inorgânicas de P em um Neossolo Quartzarênico após nove anos de cultivo sucessivos com cana-de-açúcar sem queima prévia do canavial para colheita. Para tanto, duas áreas, plantio de cana-de-açúcar e mata nativa de referência, situadas no município de Paraipaba-CE, foram selecionadas. Em cada uma das áreas foram coletadas amostras nas profundidades de 0 - 0,025; 0,025 - 0,05; 0,05 - 0,10; 0,10 - 0,20 e 0,20 - 0,30 m; determinando-se os teores de fósforo orgânico (Po) e inorgânico (Pi) obtidos através de extração sequencial, o fósforo remanescente (Prem) e a capacidade máxima de adsorção de fósforo (CMAP) do solo. De maneira geral, a permanência da palhada na superfície do solo sob cultivo de cana-de-açúcar promoveu a manutenção dos níveis de Po nas camadas superficiais do perfil. O Po acumulou -se predominantemente na fração biodisponível extraído com bicarbonato de sódio nas duas áreas. Com relação ao conteúdo de Pi, as mudanças foram mais evidentes devido ao efeito das sucessivas aplicações de fertilizantes fosfatados ao longo do cultivo, sendo a fração extraída com hidróxido de sódio 0,1 mol L-1, a mais representativa com maiores níveis de P acumulados. A adsorção de P foi influenciada pelo conteúdo inicial do nutriente no solo e nenhuma relação entre adsorção de P e o conteúdo de matéria orgânica foi observada. O maior valor de adsorção de P foi observado na camada inferior da área de mata (133,3 mg kg -1) e a menor adsorção na camada superficial da área sob cultivo de cana (59,5 mg kg-1).

ABSTRACT The objective of this study was to evaluate the adsorption of phosphorus (P) and changes in the concentrations of organic and inorganic forms of P in a Neossolo Quartzarênico (Typic Quartzipsamment) after 9 years of successive cultivation with sugar cane without burning to harvest. Therefore, two areas, one in which cane sugar was planted and a native forest reference area, located in the municipality of Paraipaba-CE, were selected. In each area, samples were collected at depths of 0−0.025, 0.025−0.05, 0.05−0.10, 0.10−0.20, and 0.20−0.30 m, and the levels of organic (Po) and inorganic (Pi) phosphorus obtained by sequential extraction, the remaining phosphorus, and the maximum adsorption capacity of phosphorus by the soil were determined. In general, the permanence of straw on the soil surface under sugarcane cultivation promoted the maintenance of Po levels in the surface layers of the profile. The Po accumulated predominantly in the Po fraction extracted with sodium bicarbonate in both areas. Regarding the Pi content, changes were more evident during cultivation due to the effect of successive phosphate fertilizer applications. The fraction extracted with 0.1 mol L -1 sodium hydroxide was the most representative, with the highest levels of P uptake. P adsorption was influenced by the initial content of the nutrient in the soil and no relationship between P adsorption and organic matter content was observed. The highest level of adsorption was observed in the bottom layer of the forest area (133.3 mg kg -1) and the lowest level of adsorption was observed on the surface layer of the area under sugarcane cultivation (59.5 kg mg-1).

RESUMO A permanência da palhada da cana-de-açúcar sobre a superfície do solo no sistema sem queima do canavial tem influência direta na dinâmica da matéria orgânica desses solos. Objetivou-se com este estudo avaliar as mudanças ocorridas nos conteúdos de carbono orgânico total (COT), carbono da matéria orgânica leve (CMOL) e carbono orgânico particulado (COP) e em seus respectivos estoques de carbono em um Neossolo Quartzarênico após nove anos de cultivo com cana-de-açúcar sem queima prévia do canavial em Paraipaba-CE. Foram coletadas amostras de solo deformado e indeformado nas profundidades de 0,0 - 0,025; 0,025 - 0,05; 0,05 - 0,10; 0,10 - 0,20 e 0,20 - 0,30 m em uma área sob cultivo de cana-de-açúcar e em uma área de mata nativa adjacente, quantificando-se os teores de COT, CMOL e COP, assim como os valores de estoques de carbono acumulados na camada de 0 - 0,30 m associados a essas frações: EstCOT, EstCMOL e EstCOP. Mudanças no conteúdo de COT após nove anos de cultivo de cana-de-açúcar sem queima foi observado apenas nas camadas de 0,10 - 0,20 e 0,20 - 0,30 m. Já o CMOL apresentou variação apenas para a camada de 0,025 - 0,05 m. As mudanças ocorridas no conteúdo de COP foram mais perceptíveis do que no conteúdo de COT e CMOL. O CMOL na área de cana apresentou uma elevada similaridade com o COT, o que pode tornar inviável sua quantificação em estudos para inferir sobre a dinâmica da matéria orgânica em solos. O cultivo de cana-de-açúcar aumentou o EstCOT, o EstCOP e o EstCMOL na camada de 0 - 0,30 m em comparação a área de mata nativa adjacente.

ABSTRACT The permanence of sugarcane straw on the soil surface, in systems without the pre-harvest straw burning practice, directly affects the soil organic matter dynamics. The objective of this work was to evaluate the changes in total organic carbon (TOC), carbon in the light organic matter (CLOM) and particulate organic carbon (POC), and their carbon stocks in a typic Quartzipsamment cultivated for nine years with sugarcane crops, which were conducted without the pre-harvest straw burning practice, in Paraipaba, State of Ceará, Brazil. Disturbed and undisturbed soil samples were collected at depths of 0.0-0.025, 0.025-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.30 m, in the sugarcane crop area and in an adjacent native forest area, in order to quantify the TOC, CLOM and POC, as well as the carbon stocks accumulated in the layer 0.0-0.30 m related to these fractions (TOCSt, CLOMSt and POCSt). TOC content changes after nine years of sugarcane crops, conducted without pre-harvest straw burning, were found only in the layers 0.10-0.20 and 0.20-0.30 m. The CLOM varied only in the layer 0.025-0.05 m. The POC content changes were more noticeable than the changes in TOC and CMOL. The CLOM of the sugarcane crop area presented high similarity with TOC, which may affect their quantification in studies related to the soil organic matter dynamics. The sugarcane crop increased the TOCSt, POCSt and CLOMSt in the layer 0.0-0.30 m, compared with the adjacent native forest area.

Com o objetivo de avaliar a interferência da relação fósforo-zinco sobre o crescimento inicial de pitaia para fornecer informações que subsidiem a definição de sistemas de produção mais adequados para a exploração desta cultura no Brasil, realizou-se o experimento, testando cinco doses de P (0; 75; 150; 225 e 300 mg dm-3) e Zn (0; 2; 4; 6 e 8 mg dm-3), sendo os níveis de cada nutriente arranjados em esquema fatorial 5x5, com quatro blocos. Para a interação significativa (p<0,05), procedeu-se ao ajuste em superfícies de resposta do tipo Y = β0 + β1(A) + β2(A)² + β3(B) + β4(B)² + β5(A).( B) + e. As estimativas das correlações fenotípicas foram obtidas considerando apenas o intervalo das doses de P e Zn que promoveram as melhores respostas do acesso de pitaia para os caracteres estudados. A aplicação de P e Zn, e a interação P x Zn afetam a disponibilidade de ambos os nutrientes no substrato, sistema radicular e parte aérea, influenciando, assim, o crescimento inicial de plantas de pitaia. Os rendimentos mais satisfatórios ocorrem quando há 60 - 75 mg de P dm-3 e 3,0 - 4,0 mg de Zn dm-3 no substrato, e 4,5 - 6,0 g kg-1 de P e 150 mg de Zn kg-1 na parte aérea. Esses níveis foram obtidos para a combinação de 150 - 225 mg dm-3 de P, com 4 - 6 mg dm-3 de Zn. Os teores de P e Zn na parte aérea e o somatório do comprimento dos cladódios (SCC) säo os caracteres explicativos que apresentam maiores efeitos diretos sobre a massa seca dos cladódios (MSC).

With the aim to evaluate the role of zinc-phosphorus ratio in the initial growth of pitaia for provide information that supports the definition of production systems more suitable for the exploitation of this crop in Brazil an experiment was carried out, testing five levels of P (0, 75, 150, 225 and 300 mg dm-3) and Zn (0, 2, 4, 6 and 8 mg dm-3) were each nutrient levels, arranged in 5x5 factorial design with four blocks. For significant interaction (p <0.05) proceeded adjustment in response surfaces of type Y = β0 + β1 (A) + β2 (A)² + β3 (B) + β4 (B) ² + β5 (A). (B) + e. Estimates of phenotypic correlations were obtained considering only the range of doses of P and Zn that promoted the best answers to the access pitaya traits. Application of P and Zn, and P x Zn interaction affect both the availability of nutrients in the soil, roots and shoots, thus influencing the early growth of pitaya. The most satisfactory yields occur when there is 60 - 75 mg P dm-3 and 3.0 - 4.0 mg dm-3 of Zn in the soil and 4.5 to 6.0 g kg-1 and 150 mg of P Zn kg-1 in shoots. These levels were obtained for the combination of 150 to 225 mg dm-3 with P 4 - 6 mg dm-3 of Zn. The levels of P and Zn in the shoot and the sum of the length of cladodes (SCC) are the characters that have greater explanatory direct effects on dry weight of cladodes (MSC).

The growth and nutrient assimilation was evaluated in CaCl2- and CaSO4-supplemented cowpea plants subjected to salt stress (75 mM NaCl). The salinity significantly reduced the cowpea vegetative growth. The addition of CaCl2 in the growth medium did not significantly affect plant growth, while for the CaSO4, the beneficial effects of Ca2+ were moderate. Salinity increased the Na+, K+, Cl-, N and P content in the plants, however it decreased the content of Ca2+ and Mg2+. Increases in Ca2+ concentration in the nutrient solution caused decreases in the Na+ and Mg2+ contents and increases in Ca2+, K+, P, and Cl- contents. The supplemental Ca2+ may alleviate the Na+ toxicity and may improve nutritional and ionic balance in cowpea, but it cannot overcome the osmotic effects associated with the increased total salt concentration.

El cultivo de coco variedad Anão viene creciendo en el Estado de Ceará (Brasil) como respuesta a la creciente demanda de este producto por las grandes industrias. El objetivo del presente estudio fue evaluar los efectos de dosis de nitrógeno y potasio sobre el número de flores femeninas, de frutos, de racimos, peso del fruto, volumen de agua del coco y sólidos solubles (ºBrix), en palmas de coco variedad Anão verde de Jiqui, con 4 años de edad, aplicadas bajo fertirrigación en un suelo litoral. El trabajo fue desarrollado en un suelo Neossolo Quartzarênico distrófico en el período de enero a diciembre de 2003. El diseño experimental utilizado fue de bloques aleatorios, con 4 repeticiones, considerando 5 dosis de N y 5 de K combinadas. Con excepción del número de racimos por palma, los otros parámetros estudiados mostraron valores superiores de producción, en relación con la dosis aplicada. Los resultados más significativos, con relación a la máxima eficiencia de respuesta, para las variables número de flores femeninas, de fruto, peso del fruto, volumen de agua del coco y sólidos solubles totales, tuvo el tratamiento con 2,10 kg N y 3,50 kg K por planta y año que parece ser la dosis óptima en todas las variables analizadas.

The culture of the dwarfed coconut palm has been growing in the Ceará State (Brasil) as a response of the growing demand for this product by the great industries. The objective of the present study was to evaluate the effects of nitrogen and potassium fertilizer rates on the number of female flowers, fruits, coconut clusters, fruit weight, coconut water content and ºBrix, in a plantation of dwarfed coconut palm ‘Anão verde de Jiqui‘ with 4 year old plants, applied via fertigation in a soil of the littoral region of the State of the Ceará. The experiment was conducted in a soil classified as Neossolo Quartzarênico dystrophic in the period between January and December of 2003. The statistical design was a randomized block with 4 replications consisted of combination of 5 rates N and 5 ones of K. With exception to the number of coconut clusters, all variables were higher than the production averages with relation to determined applied rate. The most significant results, in terms of maximum production responses, were related to the variables number of female flowers, coconut clusters, fruits, and ºBrix, where the treatment with 2.10 kg N and 3.50 kg K per plant and year might be the optimal one for all studied variables.

Trata-se de um trabalho de incubação, em vasos, feito com a finalidade de verificar a influência da adição de sulfato de amônio sobre a evolução de carbono, nitrogênio e relação C/N em três solos argilosos do município de Piracicaba. Várias conclusões foram tiradas, sen do a principal a seguinte: A evolução do teor de carbono e da relação C/N podem ser tomadas como parâmetros na avaliação das fases de decomposição da matéria orgânica.

The experiment was carried out in pots using three clayish soils from the municipality of Piracicaba, SP, Brazil. The objective of this work was to obtain information on the decay of organic residue (corn culture trash applied at the proportion of 50 ton/ha) and the influence of nitrogen sulphate at the levels of 0, 50, 100 and 150 kg N/ha on the added organic material rate of de cay. The experiment was installed at room conditions and protected from rain. The evaluation of the decay was made by determinations of the carbon content and of the C/N ratio of the soils during the incubation period (70 days). The samples were collected and analyzed weekly. The moisture of the soils was mantained at the level of 70% of the water retained at 1/3 atm. The main conclusions are as follows: 1) The addition of mineral nitrogen in the soils accelerated the losses of carbon from the soils, showing a greater effect during the initial incubation period. 2) The addition of nitrogen affected the content of residual carbon in the final incubation period. Increasing levels of added nitrogen lowered the remaining carbon content in the soil at the end of the incubation period. 3) The addition of nitrogen affected the reaction of the C/N ratios in all the used soil. The treatments that received mineral nitrogen showed closer C/N ratios during the incubation period. The amount of mineral nitrogen applied was related to the narrowing speed of the values in the initial incubation period. 4) There is a strong indication that little increments of the total nitrogen (with peaks at the 28th day) are related to the addition of mineral nitrogen in all the soils. 5) The evolution of the carbon content and of the C/N ratios can be taken as parameters in the evaluation of the organic material rates of decay for the used soils and within an incubation period of 70 days.