|Anderson, Randal - Randy|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/4/2004
Publication Date: 11/10/2004
Citation: Tanaka, D.L., Anderson, R.L., Rao, S.C. 2004. Crop sequencing to improve use of precipitation and synergize crop growth. Agronomy Journal 97:385-390. Interpretive Summary: Sustainable cropping systems have changed over the years. Since the 1930's, fallow techniques in the Great Plains to store precipitation during fallow have improved fallow efficiencies from 20% to about 40% in the late 1980's. Still, at least 60% of the precipitation is lost to evaporation. The purpose of this paper is to evaluate the impact of crop sequencing on precipitation use and show how crop sequencing accentuates synergistic interaction among crops. One problem producers have is how to choose and sequence crops in intensive-diverse cropping systems. Temperature and precipitation patterns are factors that determine the crops used in cropping systems. In the southern Great Plains, researchers have taken advantage of the bimodal annual precipitation pattern to produce a winter wheat crop as well as a pigeon pea forage crop during the non-crop period between winter wheat harvest and seeding without adverse influences to winter wheat. Water-use efficiency of winter wheat was improved by 18 to 56% when diversifying intensive cropping systems with a broadleaf crop in the central Great Plains. In the northern Great Plains, cropping systems tend to have greater crop diversity making crop sequencing critical. During years when growing season precipitation was about average (26 cm), canola, crambe, dry bean, flax, safflower, soybean, spring wheat, and barley seed yields were influenced by the previous crop. For six of the ten crops, the lowest seed yield occurred when the previous crop was either canola or crambe. Cropping systems of the future will need to take advantage of crop sequences through synergism and polyculture.
Technical Abstract: Current cropping systems will not be sustainable without change. The broad scope problem associated with developing sustainable cropping systems is how to choose and sequence crops in cropping systems. Our objectives were two-fold: 1) evaluate the impact of crop sequencing on precipitation use and 2) show how crop sequencing can accentuate synergistic interactions among crops. Crop-fallow systems that developed in the Great Plains have resulted in precipitation storage efficiencies of about 20% in the early 1930s to about 40% in the late 1980s. While fallow techniques have improved precipitation storage efficiencies, at least 60% of the precipitation is still lost to evaporation during fallow. Integrated crop/livestock systems have been developed in the southern Great Plains to take advantage of the bimodal annual precipitation pattern to produce high quality pigeon pea (Cajanus cajan L. Millsp.) forage during the non-crop period between winter wheat harvest and seeding. Pigeon pea can be grown after winter wheat harvest in mid-June because pigeon pea has a deep rooting system that uses soil water below the effective rooting depth of wheat and precipitation that occurs from mid-June to late September. Soil water content at winter wheat seeding was the same for non-crop treatments and treatments where pigeon pea was grown. In the central Great Plains, water-use efficiency of winter wheat was improved 18 to 56% by including broadleaf crop in a grass-based rotation. Cropping systems in the northern Great Plains tend to be more diverse and research at Mandan, ND suggest that seed yield of flax (Linum usitatissium L.) can be tripled with a safflower (Carthamus tinctorius L.)-flax crop sequence verses a flax-flax crop sequence. Great Plains cropping systems of the future will not only need to take advantage of crop sequences through synergism, but also take advantage of the interactions associated with diversity in space (polyculture) as we enter an era of greater environmental awareness.