Nitrogen Management for Irrigated Potato Production under Different Tillage

Authors: Alva, Ashok; Collins, Harold; Boydston, Rick

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2009
Publication Date: 4/1/2009
Citation: Alva, A.K., Collins, H.P., Boydston, R.A. 2009. Nitrogen Management for Irrigated Potato Production under Different Tillage. Soil Science Society of America Journal. 73:1-8.

Interpretive Summary: The current industry standard potato production practices require about 8-9 heavy equipment passes through the field from land preparation through harvesting potatoes. Potato is generally rotated with sweet corn or field corn. In the case of sweet corn, the current industry practices require six passes of heavy equipment. A four-year field study was conducted in a sandy soil with potato – two years of sweet corn rotation to evaluate the above industry standard tillage practice (CT) verses reduced tillage (RT), by elimination of four and three equipment passes for potato (‘Ranger Russet’ cultivar) and sweet corn, respectively as compared to that for the CT treatment for respective crops. For potatoes, different pre-plant (either 56, 112, or 168 kg N/hectare rates) and in-season (either 112, 224, 280, or 336 kg N/hectare rates) nitrogen management treatments were also evaluated under each tillage treatment. In-season nitrogen was delivered as five fertigations at two-week intervals, four weeks after seedling emergence, except in one treatment 224 kg in-season nitrogen.(with 112 kg pre-plant N) was delivered in ten fertigations at weekly intervals. Total tuber yield or yields in different size grades were similar under both tillage treatments as well as most nitrogen management treatments, except some yield reduction at 56 kg per hectare pre-plant nitrogen treatments. Elimination of four equipment passes in the RT treatment without sacrificing tuber yield or quality is of considerable interest for reducing the energy cost for production. Further, the soil quality as well as soil biology benefits under RT are being evaluated.

Technical Abstract: Four years of potato (Solanum tuberosum) field study was conducted under center pivot irrigation using large size plots and standard industry cultural practices to evaluate the affects of reduced or conventional tillage and different N management practices; i.e. pre-plant N rates of either 56, 112, or 168 kg/ha; and in-season N rates of either 112, 224, 280 or 336 kg/ha. Despite the high tuber yield (up to 80 Mg/ha) growing conditions; total tuber yields, tubers in different size grades, as well as tuber specific gravity were similar across both tillage practices and different N management programs with minor exceptions only in one out of four years. Reduced tillage avoided four equipment passes as compared to the conventional tillage. The tuber yield as well as quality were similar across pre-plant N rates of 56, 112, or 168 kg/ha, for a total N rate of either 224, 336, or 448 kg/ha. Increasing the frequency of in-season N application (from 5 to 10) at a given N rate did not support increased tuber yield or tuber quality. This study demonstrated no negative effects of reduced tillage for irrigated potato production, and that optimal N program appears to be 112 kg/ha pre-plant application and similar in-season N rate in five applications at two-week interval beginning four weeks after seedling emergence. Therefore, reduced tillage offers an option for saving energy and labor costs, without compromising tuber yield and/or quality, thus provides an economic incentive in addition to benefits of reducing soil erosion and enhancing soil biology and/or soil quality.