Abstract
In the North China Plain, groundwater tables have been dropping at unsustainable rates of 1 m per year due to irrigation of a double cropping system of winter wheat and summer maize. To reverse the trend, we examined whether alternative crop rotations could save water. Moisture contents were measured weekly at 20 cm intervals in the top 180 cm of soil as part of a 12-year field experiment with four crop rotations: sweet potato→ cotton→ sweet potato→ winter wheat-summer maize (SpCSpWS, 4-year cycle); peanuts → winter wheat-summer maize (PWS, 2-year cycle); ryegrass–cotton→ peanuts→ winter wheat-summer maize (RCPWS, 3-year cycle); and winter wheat-summer maize (WS, each year). We found that, compared to WS, the SpCSpWS annual evapotranspiration was 28% lower, PWS was 19% lower and RCPWS was 14% lower. The yield per unit of water evaporated improved for wheat within any alternative rotation compared to WS, increasing up to 19%. Average soil moisture contents at the sowing date of wheat in the SpCSpWS, PWS, and RCPWS rotations were 7, 4, and 10% higher than WS, respectively. The advantage of alternative rotations was that a deep rooted crop of winter wheat reaching down to 180 cm followed shallow rooted crops (sweet potato and peanut drawing soil moisture from 0 to 120 cm). They benefited from the sequencing and vertical complementarity of soil moisture extraction. Thus, replacing the traditional crop rotation with cropping system that involves rotating with annual shallow rooted crops is promising for reducing groundwater depletion in the North China Plain.
Highlights
Groundwater – the world’s largest freshwater resource is essential to global food security by supporting irrigation of crops in periods without sufficient rainfall (Piao et al, 2010)
This is the same trend as seen in a previous study (Yang et al, 2015b) with a 12th year data added
We examined here whether cropping systems that alternate shallow and deep rooted crops can save water compared to the traditional rotation of winter wheat and summer maize and how the crop sequence influenced
Summary
Groundwater – the world’s largest freshwater resource is essential to global food security by supporting irrigation of crops in periods without sufficient rainfall (Piao et al, 2010). How Crop Rotations Save Groundwater obvious at the regional scale, such as in highly intensified agricultural parts of India, China, and the United States (Aeschbach-Hertig and Gleeson, 2012). Food production in such regions is only sustainable in the long term if groundwater levels are stabilized. Without the change and adjustment of the conventional winter wheat-summer maize cropping system, the groundwater table will continue to fall, even though many agricultural water-saving technologies have been implemented during the past 20 years. We are especially interested in exploring how crop sequencing within alternative crop rotations influences water use and offers opportunities for control
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