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Alfalfa Root Development and Shoot Regrowth in Compact Soil of Wheel Traffic Patterns

Grimes, D. W., Sheesley, W. R., Wiley, P. L.
Agronomy journal 1978 v.70 no.6 pp. 955-958
Medicago sativa, Xerorthents, alfalfa, greenhouse experimentation, harvesting equipment, regrowth, root growth, sandy loam soils, shoots, soil compaction, soil density, traffic, wheels
Reduced growth and fewer plants are common in wheel paths of post harvest equipment in alfalfa (Medicago sativa L.) fields of the San Joaquin Valley. Up to 70% of the soil surface may be covered by equipment wheels in a single harvest. Field and glasshouse studies were conducted to quantify plant and soil responses to wheel traffic in confined paths scheduled to simulate harvest operations. Three field compaction treatments simulated harvest, postharvest, and harvest plus postharvest wheel traffic. A no-traffic area served as a control treatment. Compaction of a sandy loam soil (Typic Xerorthents) in traffic zones reduced root-length density (cm of root per cm³ of soil) as much as 60% in a 15-to-30-cm depth zone. Postharvest traffic reduced plant population and yield by damaging crowns and regrowth shoots. Field observations on soil-compaction root-growth relations were substantiated by a glasshouse study that char. acterized alfalfa root-length density (Rd, cm³ of root per cm³ of soil) as a function of soil bulk density (Dₛ, g cm⁻³) and time (T, days) as Rd = −23.51 +27.88Dₛ +0.2210T −9.135D,ₛ ² −0.0003548T² −0.08360DₛT, R² = 0.84. Root growth in a field study was enhanced by delaying the harvest for newly established seedings.