Atributos físicos de um latossolo, sistema radicular e produtividade da soja sob tráfego controlado em plantio direto no sul do Brasil

Abstract

Soil compaction occurs due to the disorderly passages of machines verified in traditional traffic. Matching traffic lines, working width and gauge of agricultural machinery allow the adoption of controlled traffic farming. This type of traffic aims to concentrate the compaction in the same places in all agricultural activities, seeking to keep the places without traffic in favorable conditions to the development of plants. The objective of this study was to analyze: physical attributes of a typic Hapludox soil, root system length, and soybean and oat yields, subjected to different types of agricultural traffic under a no-tillage system (NT). The study was conducted in a 89 ha field (on-farm research), in the municipality of Carazinho, RS, managed under NT over the last 20 years. Two sources of variation were investigated, traffic types and intensities. For traffic types the levels were: traditional traffic (TT), controlled traffic (CTF) and annual alternate traffic (AAT). For traffic intensities the levels were: maximum traffic (Tma), maximum traffic one year ago (Tma1), maximum traffic two years ago (Tma2), medium traffic (Tme), medium traffic one year ago (Tme1), medium traffic two years ago (Tme2) and without traffic (WT). This study firstly presented changes in the soil physicohydraulic parameters and its association with and soybean seed yield and oat aboveground dry mass production (ADMP). Evaluations were performed for soil bulk density, macroporosity, microporosity, total porosity at four times; penetration resistance at seven times; soil water infiltration rate at twice. Soybean seed yield was evaluated during three growing seasons, from 2015 to 2018, and oat ADMP in 2017. As a second section, it was explored the relationship between the traffic intensities, root development and soybean seed yield in the 2017/18 growing season. Lastly, the results of the first and second studies were standardized to a hectare base, and they were evaluated dependently for each type of traffic, as well as the profitability and payback. In the first study were observed, soil bulk density reductions and macroporosity increases in the soil surface. The accumulated infiltration increased in the places without traffic for CTF and AAT treatments. Soybean seed yield in the 2016/17 growing season increased in the treatments WT, Tme1 and Tma1. The most productive ADMP oat treatments was AAT WT. In the second study the effect of the shanks under the old traffic lines was temporary, not being perceived after two years of the displacement of the traffic lines. There was no significant difference for root length and for soybean seed yield. For the third study was verified an increase in the accumulated yield for the CTF and AAT traffics, while the highest profitability and the shortest time for the payback was observed in the CTF treatment. Thus, it was verified that AAT should be evaluated for a longer period in order to determine the beneficial of performing traffic lines planned changes in the soil. In summary. The adoption of CTF provided improvements in the physical structure of the soil, increased the accumulated infiltration and the profitability promoting a productive increment.