Mathematics models of prediction of sorption and selectivity of herbicides in sugar cane in function of humidity and physico-chemical characteristics of the soil

• Grant number: 15/15321-2
• Support Opportunities: Scholarships abroad - Research Internship - Doctorate
• Start date: September 19, 2016
• End date: June 10, 2017
• Field of knowledge: Agronomical Sciences - Agronomy - Crop Science
• Principal Investigator: Pedro Jacob Christoffoleti
• Grantee: Paulo Vinicius da Silva
• Supervisor: Scott Jay Nissen
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Institution abroad: Colorado State University, United States
• Associated to the scholarship: 14/12127-8 - Behavior and environmental bioactivity on weeds herbicide residual applied on straw cane sugar in different soil water conditions, BP.DR

Abstract

The physico-chemical characteristics of the soil associated with their moisture condition, influence the sorption phenomena and availability of herbicides in the soil solution. This situation can affect the selectivity of herbicides in cropping systems with pre-sprouted seedlings of sugarcane (MPB), where the root system is in direct contact with the treated area of herbicide, resulting in greater absorption and translocation. Thus mathematical models of prediction of herbicides behaving in soil can provide safe herbicide applications regarding selectivity. Given the above, the study will aim to develop mathematical models of herbicides sorption prediction used in sugarcane and its selectivity for pre-sprouted seedlings (MPB), when applied to soils with different moisture conditions and physicochemical characteristics. To this will be carried out two experiments with Amicarbazone and indaziflan herbicides in a completely randomized design, with four replications in a factorial model 5 x 4, where five is the soils with different physicochemical characteristics and four is different soil moistures. In the first experiment, the experimental unit shall consist of test tubes with a capacity of 15 ml, where an amount equivalent of two grams of soil will be deposited, then the samples will receive different amounts of water aiming to establish the following humidity levels: 40, 60 80 and 100% of field capacity. Following, will be applied working solutions of amicarbazone herbicides (equivalent to 1.400 g a.i. / ha) and indaziflan (equivalent to 200 g a.i. / ha), which is a solution containing technical product and the radio herbicides labeled 14C. These treatments will be performed to calculate the Kd (sorption coefficient), Koc (sorption coefficient taking into account the organic carbon content) and Kf (Freundlich equation), and the availability of herbicides in the soil solution in these application conditions. In another experiment, 1.5 L vessel capacity will receive the herbicide solutions containing radio products marked and will be subsequently carried out the planting of pre-sprouted seedlings of sugarcane, the evaluations are qualitative (radiography of plants and visual evaluation fitoxicidade ) and quantitative (quantify residues linked to herbicides in water, soil and plants). There will also be analysis inherent of absorption, translocation and metabolism. The root system will be assessed by electron microscopy of light and color of the pulp. The data of selectivity in sugar cane; sorption of herbicides, availability in the soil solution, humidity and physicochemical characteristics of the soil will be associated to two regressions.