The agricultural importance of loess

Loess soils are among the most fertile in the world, principally because the abundance of silt particles ensures a good supply of plant-available water, good soil aeration, extensive penetration by plant roots, and easy cultivation and seedbed production. Also micaceous minerals in the silt and clay fractions provide an adequate supply of potassium for most crops. and the large amounts of total nitrogen in chernozems can maintain moderate yields of cereals without fertilizer additions, However, loess soils often contain little clay, which leads to loss of organic matter from soil types other than chernozems under arable cultivation; the resulting structural instability of the surface soil causes problems of crusting, poor germination of crops and erosion. This paper reviews early opinions of the fertility of loess, and summarises later scientific assessments of loess soils in USA, China, eastern Europe and Britain. In regions of thin but fairly extensive loess deposits, such as UK and parts of USA, loess probably plays an important role in maintaining yields of arable crops, and needs special measures to protect it from the increasing erosion noted in recent decades. (C) 2001 Elsevier Science B.V. All rights reserved.