José de Anchieta Alves de Albuquerque

Interferência de plantas daninhas sobre a produtividade da mandioca (Manihot esculenta)

O manejo inadequado das plantas daninhas e uma das principais causas da baixa produtividade da cultura da mandioca no Brasil. Objetivou-se com este trabalho identificar as especies de plantas daninhas infestantes da cultura da mandioca e o grau de interferencia que estas exercem sobre o cultivo, em funcao do periodo de convivencia com a cultura. Dois experimentos foram realizados em areas adjacentes, no municipio de Vicosa-MG, utilizando-se o cultivar Cacauzinha, do grupo das mandiocas mansas. O delineamento experimental adotado foi em blocos casualizados, com sete tratamentos e quatro repeticoes. Os tratamentos do primeiro experimento foram compostos por periodos iniciais de convivencia da cultura com as plantas daninhas: 25, 50, 75, 100 e 125 dias apos o plantio (DAP); no segundo experimento, as plantas de mandioca, inicialmente, permaneceram livres das plantas daninhas pelos mesmos periodos. Em ambos os experimentos adotou-se o espacamento de 1,0 x 0,5 m, sendo a area util da parcela constituida pelas duas linhas centrais, deixando-se 1,0 m em cada extremidade como bordaduras frontais, totalizando 8,0 m2. As plantas daninhas foram avaliadas aos 25, 50, 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325 e 350 DAP. As caracteristicas produtividade de raizes, peso da parte aerea, indice de colheita, teor de amido e materia seca das raizes foram avaliadas aos 12 meses apos o plantio. As especies de plantas daninhas que predominaram na area experimental foram: Bidens pilosa, Raphanus raphanistrum, Cyperus rotundus e Commelina benghalensis, com a primeira delas predominando em quase todas as epocas de coletas. Os periodos de convivencia com as plantas daninhas nao interferiram nos indices de colheita, teor de amido e materia seca das raizes. Todavia, considerando a produtividade de raizes, o final do periodo anterior a interferencia foi proximo dos 25 dias, e o periodo critico de prevencao da interferencia situou-se entre 25 e 75 DAP. Cultivos realizados apos 75 DAP nao afetaram as caracteristicas da cultura da mandioca avaliadas.

Cultivo de mandioca e feijão em sistemas consorciados realizado em Coimbra, Minas Gerais, Brasil

The objective of this study was to evaluate the cultivation of cassava and the common bean (Phaseolus vulgaris) under different systems and plant arrangements. The experiment was carried out in Coimbra MG, Brazil, on the experimental campus of the Departamento de Fitotecnia da Universidade Federal de Vicosa. A randomized block design was adopted, with seven treatments and four replications. The treatments consisted of the following arrangements: a single row of cassava monoculture; a single row of cassava with a row of beans; a double row of cassava monoculture; a double row of cassava with a row of beans, a double row of cassava with two rows of beans; a double row of cassava with three rows of beans, and bean monoculture. The following variables were evaluated for the beans: grain yield, number of pods per plant, number of seeds per pod and 1,000 seed weight. Evaluated for the cassava, were root production, shoot mass, harvest index, number of roots per plant, root length, root diameter, root dry matter, starch content and area-equivalence index. Conclusions from the results showed that efficient land-use was observed in the intercropping arrangements of single rows of cassava with one row of beans, and of double rows of cassava with two or three rows of beans, and these are therefore recommended. Bean-plant productivity is reduced regardless of the system used when compared to monocultures, and there was no reduction in cassava yield when intercropped with beans.

Occurrence of weeds in Cassava savanna plantations in Roraima

O levantamento fitossociologico e o primeiro passo para implantacao do manejo integrado das plantas daninhas em culturas. Neste trabalho, objetivou-se avaliar a ocorrencia de plantas daninhas em plantios de mandioca na savana de Roraima. As coletas das plantas foram realizadas aleatoriamente 80 vezes em 10 lavouras, em quatro epocas (janeiro, fevereiro, marco e abril de 2012). As plantas coletadas foram cortadas ao nivel do solo e, depois disso, separadas por especie, identificadas, quantificadas e pesadas em balanca de precisao de 0,01 g. Em seguida foi feita a analise descritiva dos parâmetros fitossociologicos (frequencia, densidade, abundância, numero total de individuos por especie, frequencia relativa, densidade relativa, abundância relativa e indice de valor de importância) para as especies coletadas. Alem destes parâmetros, foram descritas as classes botânicas, familias, especies, tipo de propagacao, ciclo de vida, habito de crescimento, numero total de especies e massa seca por hectare. A composicao da comunidade da area levantada foi considerada heterogenea, apresentando 27 especies. As especies que apresentaram a maior densidade por hectare foram: Digitaria sanguinalis (210.500), Brachiaria brizantha (111.000), Brachiaria decumbens (86.500) e Brachiaria humidicola (69.000). Digitaria sanguinalis obteve maiores densidade relativa (28,08), abundância relativa (26,16) e indice de valor de importância (65,34). A maioria das plantas daninhas apresentou habito de crescimento herbaceo.

Desenvolvimento da cultura de mandioca sob interferência de plantas daninhas

One of the factors affecting the development of the cassava plant is the inadequate control of weeds. Thus, this work aimed to evaluate the development of the cassava plant under weed interference during different coexistence periods. Two experiments were installed in adjacent areas, in Vicosa, Minas Gerais - Brazil. In the first experiment, the treatments consisted of different periods of coexistence between the cassava culture and the weeds (25, 50, 75, 100 and 125 days after planting). In the second experiment, the cassava plants remained weed-free for the same pre-established periods. For both experiments, the 1.0 x 0.5 m spacing was adopted, being the useful portion area constituted by the two central lines, with 1.0 m being left at each extremity as front borders, adding 8.0 m2 up. Plant height and stem diameter were evaluated twelve times after planting at: 75, 100, 125, 150, 175, 200, 225, 250, 275, 300, 325 and 350 days. Plant number, root length and diameter evaluations were carried out 12 months after planting. Coexistence equal or superior to 50 day interval after planting caused drastic reduction in the stem diameter and height of the cassava plants. Weed control in cassava crop should be initiated around 25 days after planting.

Absorption of macronutrients by cassava in different harvest dates and dosages of nitrogen

A field experiment was carried out in 2010-2011 crop years in the experimental area of the Centro de Ciencias Agrarias of the Universidade Federal de Roraima, in Boa Vista, Roraima, Brazil. This study aimed to evaluate the effect of nitrogen availability on the concentrations of N, P, K, Ca, Mg and S in cassava, cultivar Aciolina, in different harvest times. A randomized block design was used in split-plot, with four replications. Dosages of N in cover were applied randomly on the plots (0, 30, 60, 150 and 330 kg ha-1), and in the subplot the harvest dates 120, 150, 180, 210, 240, 270 and 300 days after emergence (DAE). The vegetal material was collected, ground and then underwent an analysis for determination of nutrients concentrations in the leaves (N, P, K, Ca Mg and S). The harvest dates and dosages of N affect the nutrient concentrations in the cassava leaves, cv. Aciolina. The macronutrients dosage in the leaves, 120 DAE, is a good indicator of the nutritional status of the cassava plant. The dosage of 150 kg ha-1 of N raises the tubers roots per plant. The sequence of the macronutrients concentration in the leaves of the cassava, cv. Aciolina is N>Ca>K>Mg>P>S.

Cultivation of cassava and cowpea in intercropping systems held in Roraima’s savannah, Brazil

The objective of this work was to assess the cultivation of cassava and cowpea in different systems and arrangements of plants in Roraima’s savannah, Brazil. The experiment was performed at the experimental field of the Department of Soil and Climate at the UFRR, Boa Vista (Roraima). The experimental design adopted was in randomized blocks, with seven treatments and four replications. The treatments were: 1) a single row of cassava in monoculture; 2) a single row of cassava plus a row of cowpea; 3) a double row of cassava in monoculture; 4) a double row of cassava plus a row of cowpea; 5) a double row of cassava plus two rows of cowpea; 6) a double row of cassava plus three rows of cowpea; and 7) cowpea in monoculture. For the cassava were assessed the following variables: yield of roots, fresh weight of shoot, harvest index, number of roots per plant, roots length, roots diameter, root dry matter, starch content and index of area equivalence. For the cowpea were assessed: yield of the grains (kg ha-1), number of pods per plant, number of seeds per pod, weight of 1000 seeds, and index of area equivalence. The double rows cropping systems of cassava with two and three rows of cowpea allow obtaining equivalent yield to the monoculture of cassava in single rows. The intercropping, regardless of the arrangement, reduces grain yield of cowpea. All treatments in intercropping systems exhibit a satisfactory area equivalence index, with an average of 1.55.

Ácido cianídrico em tecidos de mandioca em função da idade da planta e adubação nitrogenada

O objetivo deste trabalho foi avaliar o teor de acido cianidrico em tecidos de mandioca, em funcao da idade da planta e niveis de adubacao nitrogenada. Utilizou-se o delineamento experimental de blocos ao acaso, em arranjo de parcelas subdivididas, com quatro repeticoes. As doses de nitrogenio em cobertura (0, 30, 60, 150 e 330 kg ha -1 ) foram alocadas nas parcelas, e as epocas de avaliacao (90, 120, 150, 180, 240, 300 e 360 dias apos o plantio), nas subparcelas. Os teores de acido cianidrico foram avaliados em tecidos da folha, caule, polpa e cortex da raiz da cultivar Aciolina. Os efeitos das doses de N e das epocas de avaliacao foram independentes. Doses entre 219 e 241 kg ha -1 de N em cobertura proporcionam os maiores teores de acido cianidrico, que variaram de 332 a 401 mg kg -1 de materia fresca nos tecidos avaliados. O teor de acido cianidrico nos tecidos reduz-se linearmente com a idade da planta. O cortex da raiz acumula o maior teor de acido cianidrico, e a polpa da raiz o menor. Por ocasiao da colheita, aos 360 dias apos o plantio, essa cultivare classificada como mandioca mansa.