Agronomic evaluation of citrus (Cleopatra mandarin) rootstock seedlings to various herbicides used in the nursery in Ibadan, Nigeria

Abstract

Weeds are a major problem in citrus nursery. A trial was conducted to evaluate weed control options in citrus root stock (Var. Cleopatra mandarin) seedlings. Prior to transplanting the root stocks herbicides were applied into treatment plots replicated three times and laid out in Randomised Complete Block Design. There were 10 Treatments: Metolachlor at 1.0 kg ai ha-1 , Metolachlor at 1.5 kg ai ha-1, Metolachlor 1.16kg ai ha-1+ Atrazine at 1.48kg ai ha-1, Metolachlor at 1.33 kg ai ha-1+ Terbutryn at 0.66 kg ai ha-1, Metolachlor at 1.67kg ai ha-1 + Terbutryn at 0.83kg ai ha-1, Diuron at 1.5 kg ai ha-1, Diuron at 2.0 kg ai ha-1, Pendemethalin at 1.0 kg ai ha-1, Monthly weeding (control 1), No weeding (control 2). Six months old root stocks seedlings were transplanted two weeks after herbicide application. Data were collected on seedling survival and growth rates and weed infestation fortnightly. Application of Diuron at 2.0 kg a.i. ha-1 and tank mixture of Metolachlor plus Atrazine at 1.16 + 0.83 kg a.i ha-1 caused high seedling motality of 19.12 and 13.97 % respectively while tank mixtures of Metolachlor plus Terbutryn at 1.67+0.83kga.i/ha caused the lowest mortality of 4.2%. Stem diameter at 20 weeks after ransplanting (WAT) was largest (1.09 cm) with Metolachlor plus atrazine at 1.16+1.48 kga.i ha-1 but smallest (0.72 cm) with Metolachlor at 1.0 kg a.i ha-1. Application of Metolachlor with Terbutryne at 1.67 + 0.83 kg a.i ha-1 resulted in the tallest plants (91.26 cm) while the shortest plant (73.23cm) were caused by Metlachlor at 1.0 kg a.i/ha. Number of leaves was highest (137) with diuron application and lowest (74) in the weedy check. Application of diuron at 2.0 kg a.i/ha and pendimethalin at 1.0 kg a.i/ha as well as hoe weeding effectively reduced weed population in the trial and enhance growth of citrus seedlings by reducing competitions.