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Effects of Applied Mechanical Stress on Plant Growth and Nutrient Uptake¹

The ever-increasing size of farm tillage machinery is contributing to increased soil compaction. Does this compaction affect dry matter production and nutrient uptake of growing plants? To better understand the consequences of increased mechanical stress on the root system, the effects of confining external stresses on root growth and nutrient uptake by pregerminated pea seedlings (Pisum sativum L. cv. Alaska) were studied in the laboratory. The application of stresses up to 269 kPa around the rooting medium (Dickinson loam, Typic Hapludoll) of pea seedlings reduced root growth and nutrient uptake. In relatively loose soil (1.16 g cm^–3), the application of a 90 kPa stress (post-planting) which resulted in a bulk density of 1.28 g cm^–3, reduced Ca, K, Mg, and Mn uptake compared to another treatment where the soil was compacted to 1.30 g cm^–3 before seeding. Such stresses, which are often applied to soils during field cultivations, also resulted in reduced root growth and distribution. In another experiment, the increased soil strength of a naturally dense subsoil, which resulted from lowering the soil water potential from –10 to –33 kPa, was associated with a 50% reduction in root length and a 21% reduction in K uptake by pea seedlings. The slower root development and reduced nutrient accumulation will affect the plant's ability to withstand environmental stresses during later stages of development.

Key Words: Soil compaction • Soil tillage • Plant nutrition • Root growth • Shoot growth

² Former research assistant, Soil Science Dep., Univ. of Minnesota, now with FUSAGRI, Apartado 2224, Caracas, Venezuela; soil scientist, USDA-SEA-AR, and professor, Univ. of Minnesota, St. Paul; soil scientist, USDA-SEA-AR, Purdue Univ., West Lafayette, Ind.; and soil scientist, USDA-SEA-AR, and professor, Univ. of Minnesota, St. Paul.

Received for publication June 1, 1981.