Autumn Cover Crops Increase Deep Root Growth of Soybean in no-Tillage System

Abstract

Root growth is crucial in crop production and is influenced by soil attributes, but also affects soil chemical, physical and biological quality, along with management and conservation practices. In this paper, soybean root growth data from a field study at Guarapuava, Paraná State, Brazil are examined. In 2019, at a farm with over 35 years of no-tillage system (NT) adoption, three management sets were established in 1,1 ha macroplots: 1) farmer's NT standard (FNT), without terraces, with downhill farming and with autumn fallow; 2) autumn cover crops and contour farming added to FNT, as best management practices (BMP); 3) terraces and contour farming (TC) added to FNT. Soybean was sowed in November 2020 and 2021, and minirhizotron tubes (1 m long, 7 cm wide) were installed into the soil just after soybean emerged in 2020. Root length, area, volume, and diameter were evaluated with the help of a root scanner. Data were submitted to descriptive statistics. The added conservation practices improved root length, area and volume, significantly for BMP in the subsoil (40-60 cm) compared to FNT standard. Minirhizotron enabled the study of roots in the field, but data variability was high, so that for annual crops with pivoting roots like soybean, root observation points (6 per plot) must be increased, and crop stand close to the observation points is a critical font of error.

Keywords:
Glycine max; Root Length; Green Manure; Contour Farming; Terrace

HIGHLIGHTS

Cover crops under contour farming significantly improved soybean root growth in subsoil after two years.

Minirhizotron technic enables root study of annual crops in the field, but high root data variability demands special care with plant stand close to the tubes after sowing, and high replication number.