Submitted to: Agronomy Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/12/2007
Publication Date: 6/5/2007
Citation: Merrill, S.D., Tanaka, D.L., Krupinsky, J.M., Liebig, M.A., Hanson, J.D. 2007. Dynamic Cropping Systems for Sustainable Crop Production in the Northern Great Plains. Agron. J. 99:904-911. Interpretive Summary: The concept of Dynamic Agricultural Systems as developed by scientists at the USDA-ARS Northern Great Plains Research Laboratory is a strategy for farmers and ranchers to achieve longer-term sustainability by responding flexibly through annual-scale management decisions in response to changing conditions. For dryland crop production, applying these principles leads to Dynamic Cropping Systems, which means for northern Great Plains, planting a diversity of crops species in continuous (non-fallowing) rotations under conservation tillage. As water is overall the most constraining factor to crop production in the region, knowledge of comparative water use by crop species is key information for producers to have. The present paper reports on differences in water use among ten crop species observed in the second of a series of crop sequence experiments which were conducted under no-till management. Soil water contents were monitored over three cropping seasons to determine patterns of seasonal (May to Sept.) soil water depletion (SWD) and overwinter (next April) soil water recharge (SWR). Differences among the crops in SWD were more important than differences in SWR in determining differences in amounts of water in the soil in the following spring. Deeply rooted sunflower consistently used the most water, leaving the least in the soil the next spring. Corn was also a heavier water user, shorter-season legumes dry pea and lentil had the lowest water use, and spring wheat was intermediate. Spring wheat was the best at capturing snow overwinter, and was second only to dry pea in level of spring soil water. The up to 4 inches more soil water left in the soil in the spring after dry pea compared to a prior sunflower crop can have negative consequences on following crops if rainfall is deficient. These differences can also have both positive and negative effects on landscape water effects, such as equipment trafficability in low field areas and runoff and erosion.
Technical Abstract: The principles of dynamic cropping systems require that producers consider climatic, market, ecological, and other factors on an annual basis in making crop choices. One of the factors that must be considered in dryland management is the amount of soil profile water available in the spring for growing a crop. Soil water depletion (SWD; May to September) and soil water recharge (SWR; observed mid-April) were determined by neutron moisture meter to a depth of 1.8 m for 3 years in a crop sequence project under no-till management on Pachic Haplustoll soil and land in central North Dakota. Crops depleted soil water in the following order, from highest to lowest: sunflower, corn (maize), grain sorghum, spring wheat, canola, buckwheat, proso millet, chickpea, lentil, and dry pea. During the cropping season, sunflower and spring wheat depleted 8 and 5 cm more soil water on average, respectively, than dry pea. With precipitation being below average, overwinter SWR was 36% and 54% of SWD in 2002-2003 and 2003-2004, respectively. Overwintrer SWD increased soil water, with sunflower leaving the least amount of water in the soil profile in the spring, and dry pea leaving the most, about 10 cm more than sunflower on average. With one exception, SWR did not greatly alter differences in springtime soil water generated by prior crops’ water use. Superior overwinter snow capture by spring wheat caused it to rank 2nd only to dry pea in April soil water amount, 10 cm greater than sunflower on average. Higher SWD by crops such as sunflower and corn has been observed here and by producers to have negative effects on following crops when rainfall is inadequate. The large differences in amounts of springtime soil water following growth of various crops the previous year – from 5 to 10 cm more for spring wheat, lentil, and dry pea compared to corn and sunflower – are expected to have considerable on-field landscape effects – more or less hillslope erosion and areas with trafficability problems – as well as off-field hydrologic effects such as increase or decrease of water, nutrient and agrochemical flows to ephemeral wetlands.