Nitrogen rate, cover crop, and tillage practice alter soil chemical properties

Long-term management practices can influence many physical and chemical soil properties. Th is study investigated the influence of 14 yr of continuous cotton (Gossypium hirsutum L.) management systems on soil pH, soil organic C (SOC), and exchangeable cations. Management practices consisted of varying N rate, tillage (no-tillage [NT] or disk tillage [DT]), and cover crop on a Lexington silt loam soil (Ultic Hapludalf) in the absence of lime additions. Lower soil pH was present in NT, hairy vetch (Vicia villosa L.) cover treatments and with increasing N rate but similar between 0- to 7.5- and 0- to 15-cm sample depths. Soil pH decreased between 0.23 to 0.37 units for each 34 kg N ha^–1 added and 0.46 units with hairy vetch cover. Hairy vetch cover and 101 kg N ha^–1 resulted in pH <5 and increased SOC and exchangeable Mn. Exchangeable Al values were >0.30 cmol_c kg^–1 with 101 kg N ha^–1 and hairy vetch cover and with 101 kg N ha^–1 under NT, but they were £0.13 cmolc kg^–1 for all other treatments. Exchangeable Al increased at pH <5 for NT with hairy vetch cover, while changes were insignificant for all other treatments. the hairy vetch cover contributed acidity equivalent to 42 to 68 kg N ha^–1 as NH₄NO₃. Although stratification of SOC occurred under NT, no other measured properties varied with depth in NT treatments, and different recommendations are not necessary for NT crop production. Appropriate N credits from hairy vetch cover will reduce excessive acidity, production costs, and potential environmental concerns.