Agriculture, Ecosystems and Environment 79 2000 129–142
Water use patterns and agronomic performance for some cropping systems with and without fallow crops in a semi-arid environment of
northwest China
Li Fengrui
a,∗
, Zhao Songling
a
, G.T. Geballe
b
a
State Key Laboratory of Arid Agroecology, Lanzhou University, Lanzhou Gansu province 730000, PR China
b
School of Forestry and Environmental Studies, Yale University, 205 Prospect Street, New Haven, CT 06511, USA Received 28 January 1999; received in revised form 12 July 1999; accepted 8 November 1999
Abstract
Winter wheat Triticum aestivum L. monoculture, characterized by a 2–3 month summer fallow from the wheat harvest in early July to sowing in late September, not only lowers the overall precipitation-use efficiency because of the large amount
of water evaporated from the bare soil during the fallow period but also has a high risk of the erosive action of rainstorms. To develop effective cropping systems as alternatives for farmers, thirty-two 3-year crop rotation systems with and without
fallow crops were established and their water use pattern, agronomic performance and soil conservation characteristics were evaluated in a semi-arid region of northwest China. Compared with wheat monoculture, the 16 rotations without fallow crops
produced more grain yield and greater water-use efficiency. Among the 16 rotations with fallow crops, seven patterns were significantly greater in grain yield and five patterns were significantly higher in water-use efficiency than wheat monoculture.
Cropping systems showed a marked increase in evapotranspiration when fallow crops were added to the rotation largely because of better utilization of seasonal precipitation. On average, the 16 rotations with fallow crops utilized 17 and 27
more precipitation than the 16 rotations without fallow crops and wheat monoculture. The use of the fallow crops did not greatly influence the quantity of water stored in the soil for use by the subsequent wheat crop because their growth depends
only on growing-season precipitation. From a perspective of soil conservation and productivity improvement, it appears highly viable to cultivate winter wheat followed by a 2–3 month fallow crop in 1 year and a summer crop cultivation in the next. This
system allows the soil to be covered during both easily-eroded rainy periods but lies bare 6 months every 2 years. As most of this 6-month period is winter, not only is soil evaporation reduced but also the danger of erosion is low. © 2000 Elsevier
Science B.V. All rights reserved.
Keywords: Wheat monoculture; Rotation system; Fallow crop; Agronomic performance; Water use patterns; Soil conservation requirement; NW China
∗
Corresponding author. Present address: Center for Arid Agroe- cological Economics, Gansu Academy of Social Sciences, 9
Jiankang Road, Anning District, Lanzhou 730070, Gansu province, PR China.
E-mail address: wangsfnwnu.edu.cn L. Fengrui
1. Introduction
In China’s semi-arid loess region, soil erosion and limited water availability are two major constraints to
sustainable crop production. This region is strongly governed by the monsoon climate. Not only is rain-
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130 L. Fengrui et al. Agriculture, Ecosystems and Environment 79 2000 129–142
fall often inadequate but also over 60 of annual pre- cipitation occurs in the 3 months between July and
September, often in the form of intense thunderstorms which cause tremendous amounts of erosion. Hence
the problem for agricultural production is not so much the absolute scarcity of rainfall but rather its uneven
seasonal distribution Li, 1998.
In the prevailing rainfed farming system, winter wheat Triticum aestivum L. monoculture is a com-
mon practice. This practice is characterized by a 2–3 month summer fallow from the wheat harvest in
end of June or early July through to sowing in late September and is generally considered to increase
soil water storage that is available for use by the subsequent crops. However, it often lowers the over-
all precipitation-use efficiency because of the large amount of water evaporated from the bare soil during
the fallow period Gao and Zhang, 1992; Zhu et al., 1994. The reason is that the fallow period closely
parallels the rainy season and lies in the height of summer-time in the region, thereby having a high
evaporative demand under high rainfall and temper- ature. Moreover, the soil lies bare during the fallow
period and will be at risk to the erosive action of heavy rainstorms. So severe soil erosion during this
period is also a great threat to sustainable production. Another negative effect of wheat monoculture on crop
production stems from pest, weed and disease infes- tation Hanley and Ridgman, 1978; Al-Fakhry, 1990;
Cook, 1990; Gao and Zhang, 1992; Zhang, 1992. It is widely recognized that the practices of crop rotation
are among most effective methods for alleviating ero- sion, improving the water availability and maintaining
high yields Follett and Stewart, 1985; Williams and Renard, 1985; Wang, 1989; Francis and Clegg, 1990;
Amir et al., 1991; Caporali and Onnis, 1992; Liu and Liu, 1992; Shan, 1993. However, the successful im-
plementation of crop rotation practices hinges upon certain environmental e.g. geographic, climatic and
edaphic, technological and socio-economic factors. Particularly, environmental factors almost completely
dictate the crop and its management selection. In semi-arid climates, choosing proper crop types and
cultivars is of great importance to the development of effective cropping systems and management prac-
tices. This choice often entails taking into account not only crop productivity and water-use efficiency but
also the time of sowing, duration of the growth cycle, growth property of seedlings and soil conservation
requirements. On the other hand, a successful crop rotation system is not only a profitable agricultural
system but also a beneficial soil conservation tool.
As part of a long-term research effort aimed at establishing a sustainable rainfed farming system in
the semi-arid and sub-humid regions of northwest China, this paper presents a detailed study on the
water use patterns and agronomic performance for some cropping systems with and without fallow crops
in a semi-arid environment. The objectives of this study were to: 1 determine the grain and above-
ground biomass production and water-use efficiency of individual crops grown in the rotation; 2 analyze
the seasonal and inter-annual patterns of soil water storage and utilization as well as water stress for
the four major rotation crops such as winter wheat, corn, potato and millet; 3 determine the grain and
aboveground biomass production and water-use effi- ciency for different rotation systems and evaluate the
capacities of the rotation systems with and without fallow crops to utilize soil water storage in conjunc-
tion with seasonal precipitation; 4 establish whether the introduction of fallow crops into the wheat mono-
culture significantly influences the quantity of water stored in the soil that will be used by the subsequent
wheat crop; and 5 discuss the characteristics of soil conservation for different rotation systems.
2. Materials and methods
