Gustavo Antônio Mendes Pereira

Crescimento da mandioca e plantas daninhas em resposta à adubação fosfatada

Growth of cassava and weed in response to phosphate fertilizer Fertilizers may be used to change the competitive relations, favoring the crop species, providing the competing species have different responses to the nutrient application. Thus, the aim of this study was to evaluate the growth of Cassava plant, Bidens pilosa L. and Brachiaria decumbens Stapf, as a function of the amount of P supplied at planting. The experiment was conducted in a greenhouse and the, treatments were arranged in a 3 x 4 factorial, involving the three species studied and four levels of phosphate fertilization (absence of P 2 O 5 , 80 kg ha -1 , 800 kg ha 1 and 4000 kg ha -1 P 2 O 5 , equivalent to 0, 1, 10 and 50 times the phosphorus dose recommended, respectively). A randomized block design was used, with five replications. The application of phosphate fertilizer promoted larger growth of the species evaluated, and cassava had higher growth of the shoot with the increased availability of phosphorus. In general, weeds showed higher responses to lower doses of phosphorus.

Fitossociologia de plantas daninhas em cultivos de feijão sobre diferentes manejos de herbicidas

Knowledge on changes in weeds communities caused by weeds management practices is important when effective strategies for the control of these species are set. A field experiment was conducted to assess the effects of herbicides applications with different sprayer boom heights on the weeds dynamics and beans yield. A 3x4+1 factorial arrangement was adopted, comprised of the combination of three herbicides (fomesafen. fluazifop-p-butyl and a mixture of both) and four different boom heights (0.20; 0.30; 0.40 and 0.50 m above target) and one control (non-weeded check). Thirty days after application (DAA), the following phytosociological indices were determined: relative frequency, relative density, relative dominance, and importance value. Sixty days DAA, yield rates were determined. Prior to the experiment installation, 22 species were identified in the entire experimental area. The species Alternanthera tenella , C helidonium majus , D igitaria horizontalis and Bidens pilosa dominated the area where there was no weed control. Reduced boom heights for application of fomesafen diminished the importance of dicot species. In the plots with fomesafen + fluazifop-p-butyl applications, the number of dicot weeds was greater than the other species, with predominance of A. tenella e B. pilosa . In general, the similarity index between the different herbicides and different boom heights was low, which indicates that the treatments used result in different weeds populations. Bean crops reduces the weeds diversity, and the application of herbicides has a positive effect on weeds infestation, with consequent gains in productivity.

Crescimento inicial da cultura da mandioca em sistema de policultivo

One of the main reasons why farmers in different regions prefer polycultures is that very often you can get higher yields in an area sown in polyculture than in monoculture with an equivalent area. Thus in systems polycultures the plants are in a state of permanent competition causing a reduction in plant growth consorts. The competition affects the production quantitatively and qualitatively, because it changes the efficiency of utilization of environmental resources such as water, light and nutrients, settling between culture and plants of other species existing on site. This competition also occurs between individuals of the same species or between biotypes prevalent in the area. Thus, the aim of this study was to evaluate the growth of two cultivars of cassava intercropped with crops of corn, beans and green manure (gaundu dwarf beans). Treatments consisted of the consortium is cassava ( Manihot esculenta ), IAC-12, with green manure, dwarf pigeonpea ( Cajanus cajan ), maize ( Zea mays ) and beans ( Phaseolus vulgaris ) beyond cropping of cassava with and without weed control. The development of cultivars was negatively influenced by weed infestation. Cultivation in consortium with two cultivars of maize, beans and faba bean dwarf caused no significant effects on cassava as compared to the same crop grown in single system with weeding.