ABSTRACT. The selectivity and efficacy of protoporphyrinogen oxidase (PROTOX) inhibitor herbicides in cassava varieties depend on product formulation, dosage, and soil texture. The aim of this study was to assess the selectivity and efficacy of flumioxazin and sulfentrazone in the cassava variety ‘IPR B36’ and the clone ‘VN 117’. Two experiments were carried out: one in a clayey soil and one in a sandy soil. Both experiments were laid in a split-plot randomized block design with three replicates. The two cassava varieties were used as main plots, with subplots consisting in 10 treatments including, flumioxazin at 50, 75, 100, and 125 g ha-1; sulfentrazone at 250, 500, 750, and 1000 g ha-1; one weed-free control, and one unweeded control. Flumioxazin (≥75 g ha-1) and sulfentrazone (≥250 g ha-1) achieved mean weed control rates > 70 and 90% in both types of soil for up to 90 days after application. Flumioxazin exhibited fewer residual effects on the cassava varieties than sulfentrazone, particularly in clayey soil. Flumioxazin was selective to the different cassava varieties planted in both soil types, whereas sulfentrazone was more selective in clayey soil. PROTOX inhibitors were effective in controlling weed growth in cassava plots, and there were no varietal differences in herbicide selectivity; however, the use of sulfentrazone should be restricted to maximum spray rates of 250 g ha-1 in sandy soils.

Resumo ‒ O objetivo deste trabalho foi avaliar a produtividade de mandioca (Manihot esculenta), bem como a densidade e o teor de carbono do solo, sob cultivo em plantio direto e convencional, em rotação com capim-marandu (Urochloa brizantha) submetido a pastejo. Os tratamentos consistiram de mandioca cultivada como a seguir: em plantio convencional após dois (CC-2P) e quatro (CC-4P) anos de pastagem; em plantio direto após dois (NTC-2P) e quatro (NTC-4P) anos de pastagem; e com pastagem perene (PP) de capim-marandu. O tratamento CC-2P apresentou maior produtividade de mandioca no ano-safra de 2016/2017 (63,29 Mg ha-1) do que o NTC-2P (47,85 Mg ha-1). No ano-safra de 2018/2019, não foram observadas diferenças significativas quanto à produtividade entre CC-4P (60,95 Mg ha-1) e NTC-4P (60,68 Mg ha-1). Entre 2012 e 2019, o teor de carbono no solo (0-10 cm) diminuiu no tratamento CC-2P. Em 2019, o estoque de carbono foi maior para o NTC-4P, em comparação aos de CC-4P e CC-2P, tendo aumentado de 16,41 Mg ha-1 a 21,46 Mg ha-1. A produtividade da mandioca varia conforme o ano-safra, enquanto o teor de carbono no solo diminui após o tratamento CC-2P, mas aumenta após o NTC-4P.

Abstract The objective of this work was to evaluate cassava (Manihot esculenta) crop yield, as well as soil density and carbon content, under no tillage and conventional cultivation, in rotation with palisade grass (Urochloa brizantha) subjected to grazing. Treatments consisted of cassava cultivated as follows: in conventional tillage after 2 (CC-2P) and 4 (CC-4P) years of pasture; in no-tillage after 2 (NTC-2P) and 4 (NTC-4P) years of pasture; and with perennial pasture (PP) of palisade grass. The CC-2P treatment showed higher cassava yield in the 2016/2017 crop year (63.29 Mg ha-1) than NTC-2P (47.85 Mg ha-1). However, in the 2018/2019 crop year, no significant yield differences were observed between CC-4P (60.95 Mg ha-1) and NTC-4P (60.68 Mg ha-1). Between 2012 and 2019, soil carbon content (0-10 cm) decreased in the CC-2P treatment. In 2019, carbon stock was higher for NTC-4P compared with CC-4P and CC-2P, increasing from 16.41 to 21.46 Mg ha-1 between 2012 and 2019. Cassava yield varies depending on crop year, whereas soil carbon content decreases after CC-2P, but increases after NTC-4P.

O programa de melhoramento de plantas no IAPAR iniciou-se em 1972, logo após sua fundação, e tem como objetivo principal o desenvolvimento de cultivares superiores, com alto potencial de rendimento, resistência genética aos principais fatores bióticos e abióticos adversos e boa qualidade nutricional e tecnológica. Ao longo desses quarenta anos o IAPAR tem disponibilizado para os agricultores 184 cultivares de diferentes espécies, resultando em aumento de produtividade, maior disponibilidade de alimentos, redução dos impactos ambientais, agregação de valor para as propriedades agrícolas e melhoria de vida dos agricultores e consumidores. A instituição cumpre assim com sua missão de gerar tecnologia contribuindo para o desenvolvimento da agropecuária paranaense e nacional, uma vez que muitas das cultivares desenvolvidas são utilizadas em diferentes regiões produtoras do país.

The plant breeding program at IAPAR started in 1972, soon after its foundation, and has as main objective the development of superior cultivars with high yield potential, genetic resistance to major biotic and abiotic adverse factors and good nutritional and technological quality. Over these forty years, IAPAR has made available to farmers 184 cultivars of different species, resulting in an increase in the productivity, greater availability of food, decrease in environmental impacts, addition of value to agricultural properties and life improvement of farmers and consumers. Thus, the institution fulfills its mission of generating technology, contributing to the development of agriculture in Paraná and in other parts of Brazil, since many of the cultivars developed are used in different regions of the country.

Este trabalho teve por objetivo avaliar o efeito da poda da parte aérea, realizada em três épocas distintas, sobre alguns parâmetros fitotécnicos da mandioca (Manihot esculenta Crantz). Todos os tratamentos foram plantados em outubro de 1991. Em 1992, efetuaram-se as podas da parte aérea em maio, julho e outubro. A testemunha foi conduzida sem poda. Em maio de 1993, todos os tratamentos foram colhidos. As produções da parte aérea na poda, foram alteradas pela quantidade de folhas. As produções fresca e seca das raízes e da parte aérea e o índice de colheita, foram modificados após a poda, em relação ao tratamento sem poda. O stand final e o número de raízes por planta, não foram alterados pela poda.

This work was undertaken with the objetive of evaluating the effect of pruning the aerial part in three distinct times upon the culture of cassava. All treatments were planted in October, 1991. In 1992, the canops pruned in three different times: May, June and July. A control treatment was cultivated without pruning. In May, 1993, all treatment were harvested. In comparision with the control, the three times of pruning resulted in alterations that modified the productions of fresh and dry root and canops matter as well was the harvest index. The final stand and the number of roots per plant were not altered by pruning. The differences in the production of canops on the pruning were altered due to the great variability in quantity of leaves

The present work had the objective of evaluating the effect of different line spacing upon some agronomic parameters of cassava (Manihot esculenta Crantz) culture. The experiment was conducted in county of Palotina, in the west region of Paraná State, Brazil. The studied spacing were 0.8, 1.0, 1.4 e 1.6 m between lines and 0.6 m between plants, which rendered population densities of 20,830, 16,660, 13,880, 11,900 and 10,410 plants/ha. For the production of fresh and dry root matter and stem fresh matter, the best space between lines was 1.0 m. The highest number of tuberous roots per plant, obtained with the space of 1.40 m between lines did not guarantee the highest productivity of root matter/ha. The production of the vegetative portion was not influenced by space between lines.