Wednesday, November 15, 2006

Effects of Within-Field Management Zones, Rates and Time of Fertilizer Nitrogen on Tuber Quality and Yield of Solanum tuberosum L.

Athyna N. Cambouris, Pedology & Precision Ag Lab, 979, De Bourgogne Ave, Quebec, QC G1W 2L4, Canada, Bernie J. Zebarth, Potato Research Centre, 850 Lincoln Road, PO Box 20280, Fredericton, NB E3B4Z7, Canada, Michel Nolin, 979 de Bourgogne Ave. Room #140, Agriculture and Agri-Food Canada, Agriculture & Agri-Food Canada, Pedology & Presision Agric. Lab., Ste Foy, QC G1W 2L4, CANADA, and Marc R. Laverdière, Institute of Research and Development in Agri-Environment, 2700, Einstein St, Quebec, QC G1P 3W8, Canada.

Appropriate rate and timing of N fertilization is critical for optimizing potato (Solanum tuberosum L.) yield and quality, however significant spatial variation in crop response to N fertilization is often observed. This study compared potato tuber yield and quality response to the rate and time of N fertilization on two management zones (MZ) delineated within a commercial potato field using soil electrical conductivity. The MZ differed primarily in terms of soil water holding capacity as controlled by the depth to the clayey substratum, and are designated SMZ (shallow clayey substratum) and DMZ (deep clayey substratum). Trials were established in each MZ from 1999 to 2001. Each trial used a RCBD with four blocks and 21 treatments. Treatments included four N rates (60, 120, 180, 240 kg ha-1), applied at each of five application timings (100:0, 75:25, 50:50, 25:75 and 0:100 where values are percentage of N applied at planting and hilling, respectively), plus a control which received no fertilizer N. Total and marketable tuber yields and tuber specific gravity of the SMZ were always higher than those of the DMZ. The proportion of large tubers and the proportion of tubers without rhizoctonia were always higher in the DMZ than in the SMZ. The total and marketable tuber yield increased curvilinearly with fertilizer N rates. The N rates required to reach maximum yield were MZ specific in 2000 and 2001. Those results were explained by the better growing conditions (higher SOM and water supplies) of the SMZ. Application of all N fertilizer at planting or at hilling decreased the total and marketable yield compared with split application. In this study, differences in tuber yield, specific gravity, and crop response to the rate and timing of N fertilization were often sufficiently large between MZ to justify different fertilizer N management strategies.