Agriculture and Forestry: Split Nitrogen Applications for Potatoes

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Split Nitrogen Applications for Potatoes

Agdex #: 163/541

Author: District Agricultural Office.

History: Revised February 3, 2000

For a high yield of quality potatoes, nutrients must be supplied to the growing crop in adequate amounts at the time they are required by the plant. Although the plant requires nutrients throughout the growing season, traditionally all the fertilizer is applied at planting and is usually banded with the planter.

The practice of applying some of the required nutrients, especially nitrogen, during the growing season has gained popularity in recent years. This technique has gained wide acceptance in much of the major growing area of the Northwestern United States where irrigation systems are used widely and fertilizer is injected into irrigation water. Although conditions in Prince Edward Island are considerably different, the use of split applications of nitrogen has some advantage here.

Advantages:

Research at the Charlottetown and Fredericton Research Stations has shown that the conventional practice of banding all fertilizer at planting is very effective on the varieties they evaluated. There are a number of points, however, which make the practice of applying fertilizer in multiple or "split" applications a logical procedure to consider for many growers.

Nitrogen, particularly in the nitrate form, is subject to significant losses if heavy rains occur early in the season, before the crop's demand for nitrogen is high. By withholding a significant portion of the nitrogen application until the prebloom stage of growth, potential nitrogen losses can be minimized.

By withholding some of the fertilizer at planting, the total rate of application is reduced thereby reducing the need to transport as much fertilizer to the field during planting and the need to fill planters with fertilizer as often.

The increasing use of urea in blended fertilizers place limits on the amounts of nitrogen which should be banded with the seed. By splitting the nitrogen application, the lower application at seeding poses no threat of damage to emerging sprouts or roots.

The application of high rates of nitrogen at planting (in excess of 180 Kg/ha) can delay tuber initiation in some varieties such as Russet Burbank. This can effectively reduce the time available for tuber development and maturation. In cases where growers find high applications of nitrogen necessary, split applications are highly recommended.

Recommendations:

If, for any of the reasons outlined, it is decided that a split nitrogen application procedure is to be used, the following guidelines should be followed:

Apply 60-100 Kg/ha of nitrogen at planting, preferably banded with the planter. This will provide an adequate amount of nitrogen to sustain the crop to the early blossom stage of growth.

Apply the remainder of the annual nitrogen requirement as a broadcast or sidedressed application of granular fertilizer prior to the last, or next to last, hilling operation. Urea or ammonium nitrate can be used as the nitrogen source unless visual nitrogen deficiency symptoms are present, in which case ammonium nitrate or calcium nitrate should be used. It is desirable, but not essential, that this fertilizer be incorporated with a hilling or cultivation operation.

Monitor the nitrate-nitrogen levels in the potato crop at the early bloom stage of growth by plant tissue analysis. One more samplings two weeks later may be necessary. Based on the tissue analysis levels, additional nitrogen may be required and can be applied as a broadcast granular application or as a foliar application.

For more details and general information, contact:
Soil & Feed Laboratory at (902) 368-5628
or your District Agricultural Office.