Nutrição mineral e seletividade de herbicida na cultura da palma forrageira (Nopalea cochenillifera) (L.) Salm – Dick cv miúda

Abstract

The objective of this work was to evaluate the types of use of nitrogen, phosphorus and potassium (NPK) and the selectivity of herbicides in the cultivation of forage palm (Nopalea cochenillifera) (L.) small Salm - Dick cv and to evaluate the selectivity of herbicides. For this, two separate experiments were carried out in the same experimental area next to each other at the UFAL Campus of Engineering and Agricultural Sciences. Before that, soil analysis was carried out for the purpose of recommending fertilization and liming. The soil preparation was carried out mechanically with plowing and harrowing and the furrows were opened manually. The planting lines were composed of 10 plants spaced 1.20 x 0.20 m between rows and plants respectively, totaling a density of 41,666 plants per hectare. The experimental plots were composed of 3 rows of plants, the useful area being represented by the central row. The first experiment used a randomized block design with 8 treatments represented by the types of formulation (00-00-00), (40-00-00), (40-00-120), (00-00-120), (00-200-00), (40-200-00), (00-200-120), (40-200-120) and 4 blocks totaling 32 experimental plots. Biometric, physiological and production variables were evaluated. In the second experiment, a randomized block design with 5 treatments Oxyfluorfen (1,240 g.i.a/ha), Sulfentrazone (600 g.i.a/ha), Ametrina (4,000 g.i.a/ha) and Hexazinone (375 g.i.a / ha) + control (without herbicide). The variables analyzed were (potential yield of photosystem II (Fv/Fm), injuries caused by herbicides, ability to control weeds by herbicides and productivity of green and dry mass of aerial part of forage palm. In the first experiment, all variables analyzed were influenced by the types of formulation, the treatments that received phosphorus, regardless of containing N or K, were superior to those that did not receive. The use of P in fertilization provided an increase of 174% in the number of cladodes per plant and per hectare, 74% and 225% in the height and width of the plants in that order, 365.38% in the IAC, 265.76% in the productivity of green mass and 228.78% in dry mass productivity. The use of P in fertilization also provided an increase in the accumulation of N in the dry mass of the aerial part of the small palm of 37.8%. In the second experiment, the variable (Fv/Fm) was not influenced by the herbicides and the plants showed values within the range considered normal, that is, there was no photoinhibitory damage. The treated plants did not present injuries regardless of the evaluation period, only those that received oxyfluorfen application from the fourth day after application, but over time they recovered. The herbicides ametrine and oxyfluorfen were efficient in controlling weeds up to 45 days after application (DAA), hexazinone showed moderate control until 45 DAA, sulfentrazone was not efficient in controlling weeds that emerged in the area during the evaluation period. Plants treated with herbicides also did not show a reduction in average productivity. In view of the above, it is evident that the small forage palm (N. cochenillifera) cv responds positively to phosphate fertilization and does not respond to nitrogen and potassium fertilization in isolation or intercropped when phosphorus is a limiting factor in the soil, and it is also possible to conclude that the herbicides sulfentrazone, ametrine and hexazinone are selective for the small forage palm, whereas oxyfluorfen is selective only when applied in a directed way between the lines of the crop or when the plants of the forage palm are in vegetative rest.