CHEMICAL ATTRIBUTES OF SOILS SUBJECTED TO NO-TILL CROPPING WITH RYE COVER CROPS

Rye (Secale cereale L.) cover crops are often promoted to supply additional residue in no-till production situations; however, the effect of inclusion of rye on soil chemical properties is largely unknown. Soils were sampled, 20 cm deep, from four 4-yr studies in which no-till corn (Zea mays L.) and soybean (Glycine max L. Merr.) were grown continuously or in rotation on a Canfield silt loam (fine-loamy, mixed, mesic Aquic Fragiudalf) or in rotation only on a Hoytville silty clay (fine, illitic, mesic Mollic Ochraqualf), with and without a winter rye cover crop. Corn had been fertilized each spring with 224 kg N ha-1 as either injected anhydrous ammonia or surface-broadcast urea-ammonium nitrate (UAN) solution. All plots sampled showed greater concentrations of organic C, exchangeable K, and Bray-1 extractable P in the surface 5-cm increment of soil than deeper in the sampled profile. Exchangeable Ca and Mg concentrations were often less at this depth than deeper in the profile, particularly when N was applied as surface-broadcast UAN solution. Soil pH was generally lowest in the zone of N application. Addition of the rye cover crop had little effect on the distribution of chemical attributes, other than increasing concentrations of exchangeable K near the soil surface in several comparisons.