Submitted to: CSA News
Publication Type: Popular Publication
Publication Acceptance Date: 9/15/2015
Publication Date: 10/1/2015
Citation: Liebig, M.A. 2015. Timely precipitation drives cover crop outcomes. CSA News. 60:10. p.14.
Interpretive Summary: Cover crops can improve nutrient-use efficiency, reduce pests, and increase yields and yield stability. Documenting such potential benefits within semi-arid cropping systems remains elusive, however. Researchers from the USDA-ARS Northern Great Plains Research Laboratory quantified agroecosystem responses to late-summer seeded cover crops under no-till management, with particular emphasis on soil properties. The study was conducted from 2008-2011 on the Area IV Soil Conservation Districts Research Farm near Mandan, North Dakota. Aboveground cover crop biomass was highly variable throughout the study (96-1430 kg/ha), and was strongly affected by precipitation received within two weeks of cover crop seeding. Late-summer seeded cover crops were effective in reducing the amount of available soil N in the spring, particularly during 2009 and 2011 when biomass production the preceding year was abundant. Cover crops did not induce soil water deficiencies for cash crops in the following spring, nor did they affect near-surface soil properties or soil coverage by residue. Based on conditions observed during the study, late-summer seeded cover crops may provide forage production and N conservation within semi-arid cropping systems, but achieving such outcomes consistently depends on timely precipitation after cover crop seeding.
Technical Abstract: Cover crops can expand ecosystem services, though sound management recommendations for their use within semi-arid cropping systems is currently constrained by a lack of information. This study was conducted to determine agroecosystem responses to late-summer seeded cover crops under no-till management, with particular emphasis on soil attributes. Short-term effects of late-summer seeded cover crops on soil water, available N, near-surface soil quality, and residue cover were investigated during three consecutive years on the Area IV Soil Conservation Districts Research Farm near Mandan, ND, USA. Mean aboveground cover crop biomass was highly variable across years (1430, 96, and 937 kg/ha in 2008, 2009, and 2010, respectively), and was strongly affected by precipitation received within 14 d following cover crop seeding. During years with appreciable biomass production (2008 and 2010), cover crops significantly reduced available N in the 0.9 m depth the following spring (P=0.0291 and 0.0464, respectively). Cover crop effects on soil water were subtle, and no differences in soil water were found between cover crop treatments and a no cover crop control prior to seeding cash crops the following spring. Late-summer seeded cover crops did not affect near-surface soil properties or soil coverage by residue. Soil responses to late-summer seeded cover crops did not differ between cover crop mixtures and monocultures. Late-summer seeded cover crops may enhance ecosystem services provided by semi-arid cropping systems through biomass production and N conservation, though achieving these benefits in a consistent manner appears dependent on timely precipitation following cover crop seeding.