Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/1999
Publication Date: 3/15/2000
Citation: Halvorson, A.D., Black, A.L., Krupinsky, J.M., Merrill, S.D., Wienhold, B.J., Tanaka, D.L. 2000. Spring wheat response to tillage system and n ferilization within a crop-fallow system. Agronomy Journal. 92(2):288-294.
Interpretive Summary: Spring wheat (SW) is generally produced in the northern Great Plains using conventional mechanical tillage (CT) techniques and a crop-fallow system. Limited information is available on the long-term effects of minimum-till (MT)and no-till (NT)systems on spring wheat yields within a SW-F system. This 12-year study examined the response of two spring wheat cultivars, Butte86' and Stoa', to tillage system (CT, MT, NT) and N fertilizer rate (0, 22, and 45 kg N ha-1) in a dryland spring wheat-fallow rotation (SW-F). Grain yields were in the order CT>MT>NT averaged over 12 years, N rates and cultivars, but tillage system effects on yield varied from year to year. Nitrogen mineralized during the 20 month fallow period was nearly adequate to satisfy the N needs of SW with all tillage systems. Responses to N fertilization varied with year. Cultivar yield differences were not significant, but did interact with tillage, N, and year for a significant 4-way interaction. The results indicate that farmers in the northern Grea Plains can successfully produce SW in a SW-F system using MT and NT systems, but yields may be slightly reduced when compared with CT systems. Based on this study, MT and NT systems may not be suitable for crop-fallow systems. Producers need to consider changing to more intensive cropping systems to really reap the benefits of the MT and NT systems.
Technical Abstract: Spring wheat (Triticum aestivum L.) is generally produced in the northern Great Plains using mechanical tillage and a crop-fallow system. A 12-yr study was conducted to determine the response of two spring wheat cultivars, Butte86' and Stoa', to tillage system [conventional-till (CT), minimum-till (MT), and no-till (NT)] and N fertilizer rate (0, 22, and 45 kg N ha-1) in a dryland spring wheat-fallow rotation (SW-F). Grain yield were CT (2227 kg ha-1) > MT (2167 kg ha-1) > NT (2101 kg ha-1), but tillage system effects on grain yield varied among years. Increasing N rate from 0 to 45 kg N ha-1 increased grain production from 2110 to 2212 kg ha-1, but yield response to N rate varied among years. Grain yields were lowest during years when total plant-available water (TPAW) was < 400 mm. In years with >500 mm TPAW, leaf spot disease incidence was greater, reducing yields of all tillage systems. Grain yields were influenced by a significant tillage x N rate x cultivar x year interaction. Averaged over years, the influence of cultivar on yield was very small and of little practical significance. These results indicate that farmers in the northern Great Plains can successfully produce SW in a SW-F system using MT and NT systems, but yields may be slightly reduced when compared with CT systems. Use of NT without adequate N fertilization may result in lower yields than with CT or MT systems.