The present study evaluated the accumulation and export of nutrients in cactus pear (Opuntia ficus-indica) cv. Gigante, fertilized with combinations of nitrogen (10, 70, 100, 130, and 190 kg ha −1 year −1 N) and phosphorus (10, 70, 100, 130, and 190 kg ha −1 year −1 P 2 O 5) under annual and biennial harvests, in Quixadá and Tejuçuoca, using a split-plot randomized block design with four replications. In Quixadá, under annual and biennial harvests, the following orders of accumulation of macronutrients (in kg ha −1 year −1) were found, respectively:

The objective of this work was to evaluate the effects of combined phosphorus and nitrogen fertilization and of harvesting frequency on the chemical composition of 'Gigante' cactus pear (Opuntia ficus-indica) cladodes. The experiment was carried out in two municipalities, Quixadá and Tejuçuoca, in the state of Ceará, Brazil. Fertilization with nitrogen (urea) and phosphorus (single superphosphate) was done with nine doses, respectively: 10 and 70, 70 and 10, 70 and 70, 70 and 130, 100 and 100, 130 and 70, 130 and 130, 130 and 190, and 190 and 130 kg ha-1 per year, besides 100 kg ha-1 N and P2O5 per year as the control. The harvesting frequencies evaluated were annual and biannual. A randomized complete block design was adopted, in split plot, with four replicates. The effect of fertilization on the contents of total dry matter, crude protein, neutral detergent fiber, organic matter, and total carbohydrates in the cladodes varies with harvesting frequency and site. Regarding harvesting frequency, there were higher contents of organic matter, total carbohydrates, and neutral detergent fiber, but lower contents of crude protein for the biannual harvesting in both municipalities. Annual harvesting improves the nutritional quality of primary and secondary cladodes in the municipality of Quixadá and of secondary and tertiary cladodes in Tejuçuoca.

The objective of this study was to find a group of independent variables that would influence and estimate maize (Zea mays L.) productivity, modeled by multiple linear regression. For that, an experimental delinquency in random order was used in a 2 × 2 factorial scheme, from two populations (45,000 and 65,000 ha-1 plants) and two spacings (0.45 and 0.90 m), with 20 replicates. Soil attributes and maize production components were evaluated. The soil attributes evaluated were bulk density, macroporosity, microporosity, total porosity, soil moisture and mechanical resistance to penetration, at depths of 0-0.15 and 0.15-0.30 m. The maize production components were plant height (PH), height of the first ear insertion (HEI), stalk diameter (SD), number of rows per ear (NRE) and number of grains per row (NGR). There was a positive correlation between the variables and production per hectare, except for grain moisture, soil moisture, macroporosity (0.15-0.30 m) and microporosity (0.00-0.15 m). The number of ears per hectare, the number of grains per row and the 100-grain weight served to estimate maize productivity. The methodology applied in this study was adequate for estimating production with an accuracy of 98% and can be applied to other experiments.

Qualidade da semeadura do arroz em função do preparo do solo e velocidade operacional do conjunto mecanizadoRice seeding quality as a preparation of the soil and operational speed of the mechanized assembly RESUMO O processo de semeadura pode ser interferido por diversos fatores, entre eles podemos citar a velocidade e o preparo do solo. Objetivou-se com esse trabalho avaliar a qualidade da distribuição de sementes de uma semeadora-adubadora de fluxo contínuo em função dos preparos do solo e escalonamento de marchas, bem como a determinação da correlação entre as variáveis estudadas. Utilizou-se a semeadora-adubadora de fluxo contínuo, tracionada por um trator 4x2 TDA. O delineamento experimental foi em blocos casualizados, em arranjo fatorial 2x3 com 4 repetições. Os tratamentos foram constituídos por dois preparos de solo e três escalonamentos de marchas. Os dados foram submetidos à análise de variância que quando significativos ao nível de 5% de significância. Para comparação de médias realizou-se o teste de Tukey a 5% probabilidade. Os dados também foram submetidos a uma análise de correlação a 5% pelo teste t, que quando significativo realizou-se uma análise gráfica. A semeadora-adubadora apresentou melhor qualidade de semeadura no solo escarificado e na marcha 1, com a distribuição de sementes na quantidade mais próximo da regulagem utilizada.Palavras-chave: Profundidade, Escalonamento de marchas, Oryza sativa L. ABSTRACTThe sowing process can be interfered by several factors, among them we can mention the speed and the soil preparation. The objective of this study was to evaluate the quality of seed distribution of a continuous-flow seeder-fertilizer as a function of soil tillage and staging, as well as to determine the correlation between the variables studied. It was used the continuous flow fertilizer sower, pulled by a 4x2 TDA tractor. The experimental design was in randomized blocks in a 2x3 factorial arrangement with 4 replications. The treatments consisted of two soil tillage and three gear shifts. Data were subjected to analysis of variance when significant at the 5% significance level. For comparison of means the Tukey test was performed at 5% probability. The data were also submitted to a 5% correlation analysis by the t-test, which when significant was performed a graphical analysis. The seeder-fertilizer had better sowing quality in the scarified soil and in gait 1, with the seed distribution in the amount closest to the used regulation.

This study aimed to evaluate the effects of nitrogen (N) and phosphorus (P) associated with dry and rainy seasons on the photochemical activity of Opuntia ficus-indica (L.) Mill. cv. Gigante. Combinations of N (10.0, 70.0, 100.0, 130.0, and 190.0 kg ha −1 yr −1 ) and P 2 O 5 (10.0, 70.0, 100.0, 130.0, and 190.0 kg ha −1 yr −1 ) were evaluated in the dry and rainy seasons in semi-arid regions. A completely randomized block design with split-plot arrangement was adopted with four replications. In Quixadá, the maximum potential quantum efficiency of photosystem II (Fv/Fm) was 0.82, observed in third-order cladodes (rainy season and N/P 75.6/10.0 kg ha −1 yr −1 ), while in Tejuçuoca, the maximum Fv/Fm was 0.81, found in 2nd/3rd order cladodes (rainy season and N/P 10.0/190.0 kg ha −1 yr −1 ). In Quixadá, the maximum electron transport rate (ETR) was 31.6 μmol m −2 s −1 in 2nd/3rd order cladodes (rainy season and N/P 10.0/190.0 kg ha −1 yr −1 ), and in Tejuçuoca, the maximum ETR was 24.1 μmol m −2 s −1 , in second-order cladodes (rainy season and N/P 110.1/10.0 kg ha −1 yr −1 ). In Quixadá and Tejuçuoca, higher values of Fv/Fm and ETR were observed in the rainy season. In Quixadá, the maximum fluorescence decrease ratio (FDR) was 4.04 in third-order cladodes (rainy season and N/P 10.0/114.8 kg ha −1 yr −1 ), while in Tejuçuoca, the maximum FDR was 6.93, found in 2nd/3rd order cladodes (rainy season and N/P 190.0/10.0 kg ha −1 yr −1 ). In Quixadá and Tejuçuoca, there was predominance of higher FDR values in the rainy season. Nitrogen, phosphorus, and water status modulate the photochemical efficiency of cladodes of cactus pear cv. Gigante in semi-arid regions.