The agricultural importance of loess

Loess soils are among the most fertile in the world, principally because th e abundance of silt particles ensures a good supply of plant-available wate r, good soil aeration, extensive penetration by plant roots, and easy culti vation 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 t han chernozems under arable cultivation; the resulting structural instabili ty of the surface soil causes problems of crusting, poor germination of cro ps 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 ro le in maintaining yields of arable crops, and needs special measures to pro tect it from the increasing erosion noted in recent decades. (C) 2001 Elsev ier Science B.V. All rights reserved.