Soil Water Storage in Dryland Cropping Systems: The Significance of Cropping Intensification

Abstract

Soil and water conservation is essential to the sustainability of Great Plains dryland agriculture. We hypothesized that cropping intensification improves the efficient use of precipitation. We evaluated long‐term observations of soil water at three locations in eastern Colorado for a range of pan evaporations (1050–1900 mm), soils, and cropping systems. Soils at various locations were mostly of the Argiustoll subgroup except for one Ustochrept and one Haplargid, both at the higher evaporation location. Normal precipitation at the three locations ranges from 400 to 425 mm yr‐1. Systems included a 2‐yr winter wheat (Triticum aestivum L.)‐fallow (WF) and more intense 3‐yr winter wheat‐corn (Zea mays L.)‐fallow and winter wheat‐sorghum [Sorghum bicolor (L.) Moench]‐fallow and 4‐yr rotations. To quantify the effectiveness of the intensified systems at utilizing precipitation, we introduce the System‐Precipitation‐Storage Index (SPSI) and System‐Precipitation‐Use Index (SPUI). Mean SPSI values were 0.19 and 0.28 for 2‐ and 3‐yr systems, respectively, meaning that the fallow periods in the 3‐yr rotation were collectively 47% more efficient at storing precipitation than fallow in WF. Inclusion of a summer crop, such as corn or sorghum, increased the fraction of precipitation allocated to growing‐season crop production (i.e., SPUI) from 0.43 in WF to 0.56 (i.e., an increase of 30%) in 3‐yr systems. The gains in efficient use of precipitation with intensification resulted from (i) reducing the frequency of the inefficient fallow preceding wheat, and (ii) using water for transpiration that would otherwise be lost during fallow through soil evaporation, runoff, and deep percolation.

Productivity and residual benefits of grain legumes to sorghum under semi-arid conditions in southwestern Zimbabwe

“…This is an accepted practice when variations in profile characteristics with depth influence water storage in the profile and prevent calibration of the neutron probe for absolute values (e.g. Farahani et al 1998).…”

Soil organic matter dynamics under grain farming in Northern Kazakhstan

“…This practice is also commonly applied in the steppe area of North America, in which the annual precipitation is below 500 mm (e.g. Farahani et al 1998). Unfortunately, it has often been reported that such agricultural practices on Chernozem soils had accelerated organic matter decomposition (Buyanovsky et al 1987;Srivastava and Meyer 1998;Mikhailova et al 2000;Karbozova-Saljnikov et al 2004).…”

Soil and Water Conservation: Our History and Future Challenges

“…This soil, water, and crop management system has dominated U.S. Great Plains agriculture for nearly a century, but is it a sustainable soil and crop management practice? The wheat-fallow system evolved as a management practice to achieve higher wheat yields by capturing and storing soil water during the fallow period and increasing available N. However, based on our experiences (e.g., Farahani et al, 1998aFarahani et al, , 1998bHalvorson et al, 2002;Lamb et al, 1985;McGee et al, 1997;Peterson et al, 1996;Peterson and Westfall, 2004;Power and Peterson, 1998;Unger et al, 2006), the system is neither sustainable nor capable of meeting the productivity demands of the 21st century.…”