Weed dry mass accumulation in response to the application of NPK fertilizers in cassava crop

Abstract

Fertilizers can be used to change competition relationships between crop and weed by promoting crop species growth, since rival species has a differentiated response to nutrients. We aimed to evaluate weed dry mass accumulation when or not NPK (nitrogen, phosphorus and potassium) fertilizers were applied to cassava crop. Therefore, weed samples were collected every 35 days, from 35 to 525 days after cassava planting, by randomly throwing a 0.25 m 2 metal square (0.5 m × 0.5 m) within useful area of the plots with and without fertilization. After each thrown, it was removed weed shoot, separated by species, then counted and weighed to determine number of plants and shoot dry mass. Fertilization did not influenced the weed population during most part of the crop cycle; however, promoted greater weed dry mass accumulation in the second crop year, 350 days after planting. Panicum maximum, Brachiaria plantaginea, Sida rhombifolia, Pavonia cancellata, Setaria parviflora and Cynodon dactylon, which were the most abundant weeds, had different responses to fertilization. P. maximum and B. plantaginea have outstood because of their shoot dry mass increase of 41.59 and 36.25%, respectively, when comparing fertilized and non-fertilized treatments.

<b>Manihot leaf abscission induced by ethrel

“…Leaf abscission is a process affected by several environmental factors, such as air temperature, water availability, pathogens, nutrition and mechanical injuries (Alves & May-De-Mio, 2008;Silva, Lilagres, Silva, Nick, & Castro, 2011). Minimum temperatures below 13 to 15°Chave been reported as leaf abscission induction factors in cassava plants (Singh, Khurana, Chakrabarti, Mukherjee, & Nedunchezhiyan, 2013;Moreira et al, 2014;Soares et al, 2015). The leaf abscission process overlaps with leaf emission as the temperature decreases, which can result in complete leaf abscission of the canopy.…”