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Title: POLYMER COATED SLOW RELEASE NITROGEN FERTILIZER FOR IRRIGATED POTATO

Author
item DAVENPORT, J - WSU
item Alva, Ashok
item WHITLEY, K - WSU
item Jabro, Jalal - Jay

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2000
Publication Date: 11/1/2000
Citation: DAVENPORT, J.R., ALVA, A.K., WHITLEY, K.M., JABRO, J.D. POLYMER COATED SLOW RELEASE NITROGEN FERTILIZER FOR IRRIGATED POTATO. AGRONOMY ABSTRACTS, P. 269. 2000.

Interpretive Summary: Irrigated areas of Columbia Basin in the Pacific Northwest area provide ideal potato production conditions with high per acre yields. This could require application of high levels of inputs including water and nutrients. Poor management of these inputs can result in leaching of water carrying nutrients below the rootzone and into groundwater, particuluarly in coarse textured soils with low water and nutrient retention capacity. Controlled release fertilizer (with polymer coating to facilitate slow release of nutrients over an extended period of time) provide an alternative source of fertilizer to minimize its leaching losses. In this study, conventional fertilizer and polymer coated fertilizer were compared on Russet Burbank cultivars in a sandy soil at 0, 170, 340, and 500 kg N/ha rates. In the conventional practice, 1/3 of annual dose was applied at planting and the remaining 2/3 delivered at in-season applications at weekly intervals for 10 weeks, through center pivot irrigation after the row closure. The polymer coated fertilizer was applied in a single dose at planting. The potato yield and quality were low with either 0 or 500 kg N/ha rates. Tuber yield and quality at 170 kg N/ha of controlled release fertilizer were equal to those with 340 kg N/ha of conventional fertilizer application.

Technical Abstract: Potato (Solanum tuberosum L.) grown under irrigated conditions in the arid Columbia Basin produces very high yields but at a cost of intensive N fertilizer inputs. Growers apply between 30 - 50% N prior to planting and the remaining N is applied through the irrigations system during the active growth period. It is recognized that there is a high potential that N management practices in potato affect groundwater quality as a number of rural wells in potato production areas have nitrate levels that exceed federal drinking water standards. To establish if polymer-coated slow release fertilizers could offer an alternative management tool, Russet Burbank potatoes were grown for 3 years with 0, 170, 340, and 500 kg N/ha with both polymer-coated urea or conventional soluble urea in split applications throughout the growing season. Both potato yield and quality were reduced when 500 kg N/ha was applied. Yield was consistently reduced in the 0 N treatment, but 170 kg N/ha as slow release material produced tuber yield and quality equivalent to using either conventional or slow relese N at the 340 kg/ha rate.