Effects of moisture stress and nitrogen fertilization on tuber nitrate-nitrogen content

Moisture stress in potato plants results in a significant increase in tuber NO_3?N levels. Research plots with three irrigation treatments and four nitrogen fertilizer rates (0, 100, 200, and 500 lb N/A) (0, 112, 224, and 560 kg N/ha) were established to test the influence of soil moisture and nitrogen rate on tuber NO_3?N content. Data from these plots showed that regardless of nitrogen rate, potato tubers from plants subjected to moisture stress had NO_3?N levels approximately twice as high as tubers from plants under optimum or excessive irrigation. With low nitrogen fertilizer rates, tuber NO_3?N levels were 78 to 80 ppm under optimum and excessive irrigation treatments as compared to 144 ppm under the deficient irrigation treatment. With excessive nitrogen fertilizer rates, tuber NO_3?N levels were 151 to 154 ppm under optimum and excessive irrigation treatments compared to 370 ppm under deficient irrigation. Correlation between tuber NO_3?N and petiole NO_3?N levels suggest that moisture stressed plants have a different relationship between tuber and petiole than plants under proper to high soil moisture conditions.