Temporal and spatial soil water management: a case study in the Heilonggang region, PR China

Long-term over-extraction of groundwater since the 1980s in the Heilonggang region, the East Hebei Plain of North China, has led to serious environmen tal problems such as seawater or saline water invasion into fresh water, la nd subsidence, etc. The conflicts between socio-economic development, water shortage and environmental degradation have become increasingly critical. Agriculture, the largest water user in the area and requiring 84% of total water supplied, is creating an unsustainable demand. Soil water is a very i mportant resource in the Heilonggang region as 76% of mean annual precipita tion becomes soil water. Effective use of this soil water is, thus, a key f or full rational utilisation of water resources in the area. A concept of t emporal and spatial management of soil water (TSMSW) is proposed, here as a means to ensure effective use of soil water, viz.: management of soil wate r in full time and possible space dimensions and readjustment of crop distr ibution in order to harmonise as much as possible crop water demand and soi l water availability. Four aspects are included: readjusting crop structure s and rotations to fit changes in soil water, increasing the soil water res ources, reducing soil water evaporation and managing soil water to meet tem poral and spatial crop water demand. Field experiments show that temporal a nd spatial management of soil water can significantly increase water use ef ficiency (WUE). For cotton, adopting an integration of micro-topography and plastic mulch has increased WUE from 0.49 to 0.76-0.86 kg/m(3); stalk mulc h with manure for winter wheat reached to 2.41 kg/m(3) and straw mulch with deep furrows (micro-topography) for summer maize increased it from 2.06 to 2.34 kg/m(3). (C) 1999 Elsevier Science B.V. All rights reserved.