Fluxo de emergência e controle químico de arroz-vermelho em soja RR™ cultivada em solo hidromórfico

Abstract

It is believed that the productive potential of irrigated rice production is of 10,000 kg ha-1. However, the productivity achieved today is still below the expected. This is mainly due to unsatisfactory control of weeds, among them, red rice. If not done properly control, this will remain weed plants, which produce seeds. So are necessary management strategies for cultural and chemical controls this weed. One option is the cultivation of soybeans in rotation with irrigated rice. It is a culture that has cultivars that are adapted to this type of soil, achieving similar yields when grown in the highlands. Besides being a different cultural management, chemical management can also be done differently, using herbicides with other mechanisms of action, either for drying, pre-or post-emergence soybean. Therefore, the aim of this study was to evaluate the chemical control of red rice and its flow of emergency after the combination of herbicide desiccation, pre and / or post-emergence in soybeans grown in hydromorphic soil. This work was carried out during the crop seasons 2011/2012 and 2012/2013, consists of 17 treatments and four blocks, the experiment was a randomized block design. Of these 17 courses, 15 received treatment in dryness, and the other two control treatments, weeded manually and without any control. And these 15 treatments, some received pre-emergence herbicides in soybean crop and others only in post-emergence. Herbicides were applied using a CO2 pressurized backpack sprayer, equipped bar with spray tips XT 110 015, the constant pressure of 1 bar (1.0197 kgf cm-2), applying a spray volume equivalent to 100 L ha-1. In hoeing, three interventions were made: the first before sowing, and the two sequent reinfestation from realizing 20 % of the share. Evaluations were made visual control red rice, using as a basis the system 0-100 for control and phytotoxicity. In the same plots, soil samples were collected at three depths, 0-5, 5-10 and 10-15 cm, with the aid of an auger cup with a diameter and height of 0.05 m. Samples were collected before application of treatments and desiccation after soybean harvest (harvest 2011/2012) and before application of treatments desiccation (season 2012/2013). Were six points per plot, the three depths. Each layer collected was homogenized and spread on a tray, which was watered daily for 90 days. Evaluation of plants germinated red rice was done weekly through its identification. The use of grass herbicides preemergence soybean crop helps reduce the seed bank in the deeper layers of the soil, either by inhibiting emergency or impracticability of seed, and in the layer of 5-10 cm, the reduction was 67%, ie, the first collection 76 seeds germinated, and in the second, 25 seeds of red rice. In the second collects the reduction was 36%, 30 germinating seeds in the first test and 19 in the second. And in relation to chemical control of red rice, treatments that joined desiccants glyphosate (3.0 L ha-1), paraquat (2.0 L ha-1) and glifosinato (2.0 L ha-1) with pre-emergent herbicides imazethapyr (1.0 L ha-1), s-metolachlor (2.5 L ha-1) and clomazone (2.0 L ha-1) or the herbicide glyphosate (3.0 L ha-1) and sethoxydim (1.5 L ha-1) applied post-emergence (V3 stage) controlled red rice up 90% and did not affect the stand and plant height (30 days) and grain yield.