Critical period of weed interference in carrot crop

Abstract

This research was conducted in Centro Hortícola of the Facultad of Ciencias Agrarias, Universidad Nacional of Asunción, San Lorenzo, Paraguay, with the objective of evaluate the effects of different periods of coexistence and weed control on carrot crop productivity and determine the periods of weed interference. Experimental randomized complete block design was used, factorial (2*14) (coexistence and weed control and 14 periods), with four replications. Each experimental unit consisted of four rows of growing 2.5 m in length. Phytosociology of infesting community, the dry mass of the crop, length, diameter and the commercial productivity of roots was evaluated. The variables were subjected to analysis of variance and comparison of means by Tukey 5%. The period prior to the interference (PAI), the total period of the prevention of interference (PTPI) and the critical period interference (PCI), was determined by analyzing sigmoidal regression Boltzmann, considering a maximum allowable loss of 5% in the commercial productivity of roots. Weeds with greater relative importance were: Coronopus didymus, Gamochaeta coarctata, Amaranthus retroflexus, Eleusine indica and Galinsoga parviflora. A maximum loss of 93.3% in the commercial performance of roots in permanent coexistence with weeds was obtained. The PAI was set at 2.7 weeks (19 days); the PTPI in ten weeks (70 days) and PCI between 19 and 70 days after crop emergence.