University of Idaho Field Trial Results

 

Field Trials Yield per Inch Variety

Yield Per Inch of Irrigation This study was designed to determine the most yield per inch of irrigation water for various varieties normally grown in Idaho under different reduced irrigation methods. Using 2002 data of 5 irrigation methods and 6 varieties. Yields were calculated then divided by the actual amount of irrigation applied. When water is limited, the most yield per inch of irrigation water would be planting GemStar and running 75% ET for the season or stepping down throughout the season. Rangers and Russet Burbanks are close.   2002 Aberdeen  5 Irrigation methods  6 varieties 2002 Aberdeen  5 Irrigation methods  6 varieties     2003 study 2003 study   Results: There is a direct correlation between reduction in irrigation and reduction in yield. Each reduction of one inch of irrigation reduced yield by about 24 cwt/a.      .94 R2 correlation.

 

Variety Choices for reduced water years Study was designed to determine which varieties do best under various reduced irrigation methods. For three years the study has consistently shown GemStar and Rangers as the best yielders, with the 75% reduced irrigation and the step down irrigation showing the best results when water is limited. If water is to be cutoff early, short season Norkotahs should be considered.     Evaluation of different varieties under different reduced irrigation methods Full Evapotranspiration Full Et cut off August 10 Reduced to 75% of ET 75% of ET cut off August 10 Step down 100% ET until July 15, 75% ET until Aug 10, 50% ET until September 10. GemStar yields best in almost all conditions. Because Norkotah has a relatively short season it does well when irrigation is cutoff in August. US Number 1 yield in Aberdeen 2002   US Number 1 yield in Aberdeen 2003 All irrigation in this 2004 trial was full season at various fraction of ET. Once again Gem Star yields best and rangers should be considered. US Number 1 yield in Aberdeen 2004   Experiments were designed to provide data for drought decisions . The first experiment was designed to determine the response of six different potato cultivars to different deficit water application scenarios. The resulting data shows appropriate cultivars/irrigation regimes that allow the grower maximum flexibility in managing his crop if drought develops. Data from three years of research have been collected for this experiment .  The experiment was conducted in 2002, 2003 and 2004 at the University of Idaho Research & Extension Center at Aberdeen. Six varieties were included, including Alturas, Summit Russet, Ranger Russet, Russet Burbank, GemStar and Russet Norkotah. These varieties represent a wide range of growth habits and water requirements. Each variety was exposed to five seasonal water allocation patterns.  Almost 19 inches were applied for the control (100% ET). One of the goals of the experiment was to explore the effects of using about 75% of ET for crop production. Three of the treatments resulted in a close approximation of this application goal. The 75% ET with a cut-off, used the least water with about 9 inches. From a variety standpoint, GemStar had the most tolerance to drought stress and produced a decent crop of potatoes, even with the most severe treatments. Russet Norkotah was little affected by the cut-off treatments, largely due to its early maturity. Alturas, on the other hand, showed negative yield response to any treatment that imposed late season stress, a result of its late maturity. Russet Burbank showed a strong decrease in No. 1 yield with both 75% ET treatments. Ranger Russet and Summit Russet had a strong negative reaction to the 75% cut-off treatment. Return to top

Effects of not Irrigating to match ET
This study shows that only by closely matching evapotranspiration can growers reach maximum yield either over or under irrigating reduces yield. Potatoes in Idaho use about 20 inches of irrigation so a difference of 3 inches from Et is about 15%.  The yield loss from under irrigation was also about 15%.
The effect of not matching ET on Russet Burbank Yields. Note: over irrigation reduces yield also.