Soil irrigation frequencies, compaction, air porosity and shear stress effects on soybean root development

Résumé 0

Effect of soil compaction on the root development of soybean plants (Glycine max L. Merrill cv. San Baiba), subjected to different treatments of irrigation frequencies, air porosity and shear stress of a sandy loam soil were performed. Soybeans are important agricultural crop of the area, where the soil is incompressible and easy deformable. The objectives were to determine: (a) Consequences of water content, compaction and air porosity over the root length, root volume, and root fresh mass; and (b) Results of air content, shear stress and normal strain on root growth. The methods used were the Proctor test, triaxial, water meters, watering frequency and 30 cm x 30 cm x 1.5 cm plastic cylinders. The randomized block was used in simple factorial arrangement with four levels of compaction per layer (0, 12, 24, 36) and four soil water content through four irrigation frequencies (daily, inter-day, every two days and each three days). The findings were: (a) Root length between 24 cm and 79.5 cm; (b) Root volume from 2 cm³ to 40 cm³; (c) Root fresh mass between 7.58 g and 34.04 g, with a higher values tendency for daily and inter-day irrigation frequencies. The daily and inter day irrigation frequencies average results were above the grand mean (52.31 cm) of root length for the four levels of compaction. It was concluded that the soybeans root system was positively influenced by water content, more than compaction and the other variables under study.