1. WATER STRESS Low moisture availability High demand (heat, wind, excess N) Low capacity (poor root system)

2. STRESS-RELATED PROBLEMS Requirements for Expression Susceptible variety + Stress conditions Potato Production Systems

3. IMPACT OF RESISTANCE ON STRESS MANAGEMENT Intensity of Management Required Resistance LevelInput Level HighLowModerate LowHigh

4. RUSSET BURBANK Common DefectsStress MalformationsHeat, drought Growth cracksMoisture stress, erratic growth Sugar endsHeat Hollow heartCold soil, low tuber set Vascular disc.Rapid vine kill, heat Low solidsHeat, early death Potato Production Systems

5. COMMON DISORDERS Potato Production Systems

6. During stress low availability of sugars and the imbalance in top/tuber growth can temporarily stop tuber growth. When growth resumes, it occurs at the site of most active cell growth. The end result is malformed tubers that may have knobs Around the eyes and bud end is where growth resumes

7. SHAPE Related to time of stress  Bottleneck bud end = late season stress  Bottleneck stem end = early season stress Consistent supply of water and nitrogen is the main key to management.

8. How does stress impact internal tuber quality? Potato Production Systems

9. Source: Kincaid et al., 1993 R 2 = 0.42 Irrigation Frequency Relationship between soil temperature and sugar ends

10. WE 75.7% 36.6% 50.4% 63.4% 0” 8” 4” Percentage of 10 Tuber Sample with Sugar Ends Impact of row orientation on Russet Burbank quality

11. CAUSES OF QUALITY PROBLEMS  Wide fluctuations or deficiencies of:  water  temperature  nutrients

12. DON’T CONTRIBUTE TO ENVIRONMENTAL STRESS WITH MANAGEMENT STRESS! Poor root development  Compaction and late cultivation Poor vine development  Erratic stands and early senescence Excess vine development - Too much N

13. 1 ft SOURCE: MODIFIED FROM WEAVER (1926) 2 ft 3 ft Healthy potato root system Compaction layer Root Pruning

14. HOW DOES A STAND LIKE THIS IMPACT SOIL TEMPERATURE? Photo courtesy of W. Bohl

15. EARLY VINE DEATH ALSO LEADS TO WARMER SOIL TEMPERATURES AT END OF SEASON

16. EXCESS NITROGEN FERTILITY CAN LEAD TO AN IMBALANCE IN VINE AND ROOT GROWTH