Long-term tillage management affects claypan soil properties and soybean cyst nematode

Use of cover crops with conservation tillage systems can affect soil chemical and biological properties. The objectives of this research were to evaluate the effect of long-term (1994-2016) no-till (NT) and reduced-till (RT) cropping systems on soil chemical properties and soybean cyst nematode (SCN, Heterodera glycines Ichinohe) egg population densities on claypan soils in northeast Missouri. Treatments included a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-wheat (Triticum aestivum L.) rotation with three tillage-cropping systems: (a) NT corn-soybean-wheat with double-crop soybean (NTDCS), (b) NT corn-soybean-wheat with frost-seeded red clover (Trifolium pretense L.) cover crop (NTFSC), and (c) RT corn-soybean-wheat. Each crop (corn, soybean, and wheat) and tillage system (NTDCS, NTFSC, and RT) was represented every year in nine large plots and replicated four times. Soil was sampled to a 15 cm depth to evaluate soil chemical properties (1994, 2002-2016) and SCN egg densities (2002-2015). Soil test pH(s), P, and K were ranked RT = NTDCS > NTFSC, RT > NTDCS = NTFSC and RT > NTFSC > NTDCS, respectively. Long-term NTFSC cover crop had the greatest soil organic matter levels in four of the 16 yr. When combined over years, SCN egg densities were lowest in NTFSC following corn, soybean, or wheat, which indicates the benefit of NT and extended crop rotations to help manage this pest.