Dryland Winter Wheat Response to Tillage and Nitrogen within an Annual Cropping System

Abstract

Winter wheat ( Triticum aestivum L.) can add diversity to dryland crop rotations in the northern Great Plains, but it is susceptible to winterkill in low surface residue environments. A 12‐year study was conducted to determine the response of two winter wheat cultivars, Roughrider and Norstar, to tillage system (conventional‐till, CT; minimum‐till, MT: and no‐till, NT) and N fertilizer rate (34, 67, and 101 kg N ha −1 ) in a dryland spring wheat–winter wheat–sunflower ( Helianthus annuus L.) rotation. Grain yields were greater with MT (1968 kg ha −1 ) and NT (2022 kg ha −1 ) than with CT (1801 kg ha −1 ), but tillage system effects on grain yield varied among years. Increasing N rate from 34 kg N ha −1 to 67 kg N ha −1 increased grain production from 1844 to 1953 kg ha −1 , but yield response to N rate varied among years. The greatest overall grain yield (2111 kg ha −1 ) was obtained with NT and application of 101 kg N ha −1 . Grain yields were lowest during years when plant‐available water (PAW) was <300 mm. In years with >400 mm PAW, leaf spot disease incidence was greatest, particularly at the lowest N rate with NT. Application of adequate N reduced the disease incidence in all tillage treatments. Cultivar differences were significant 3 out of 12 years, but not consistent. Winterkill was a factor for both cultivars in only 1 year in the CT and MT plots. Winter wheat performed well as a rotational crop in this cropping system when using MT and NT systems and adequate N fertility. Our long‐term results indicate that producers in the northern Great Plains can use winter wheat successfully in annual cropping systems that do not include a fallow period, particularly if NT is used with adequate N fertilization.