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Fluid Journal : Fluid Journal 1996-1998
2 Fluid Journal Summer 1996 Economics promising As shown in Figure 3, gross dollar return on 4 to 10 oz tubers is a clear indication that investment in KTS applications can be worth every penny. The yield improvement produced by KTS in the grower's potato fields increased gross dollar return $329/A when compared to check. Return on investment like this has the potential of paying handsomely where it ultimately counts: the grower's bank account. Management critical The cultivar we picked was Russet Norkotah, a short-season variety with a small, shallow root system. The cultivar requires high levels of fertility, coupled with critical nutrient and water management. A carefully established protocol was followed in managing this field trial. Trial design. The center pivot test field was divided into three areas for different treatments: • On one half of the circle, KCI was banded below the seed at 56 lbs/A as a total K recommendation • On inner half of other half of circle, one half of K recommendation was banded as KTS (28 lbs/A) at planting, followed by four sprinkler KTS applications at 13, 11.3, 7.9, and 9 lbs/A. • On outer half of other half of circle, the total K recommendation was banded as KTS at planting, followed by the same four sprinkler applications. The four sprinkler applications above began on July 6 at tuber initiation (38 days after planting), and continued on July 17, August 1 and August 18. Soil samples were collected and analyzed before planting to determine nutrient levels. Planting took place on May 15, 1995. Plant spacing was 12 inches. Row spacing was 34 inches. Fertilizer was applied at planting at the following lbs/A rates: N, 200; P, 40; 5, 40; and Zn, 3.5. Post planting applications took place through the sprinkler at the following lbs/A rates: N, 21, 21, and 8.6; and 5, 9.2, 7, 5.4, and 6.5. Petiole samples for nutrient analysis were collected on July 11, July 20, August 1, and August 16. Pesticides were the herbicide Turbo applied by ground, plus the fungicide Super Tin. Harvest began on September 25 and was completed in three days. Yield estimates were based on four truckload samples within each treatment area. During the harvest operation, the number of row feet to fill each sample truck was recorded, and the trucks were weighed. While unloading each sample truck, random tuber samples were collected to determine size and quality. Samples were graded by hand. More work needed The need for K and its role in potato production has yet to be fully explored. Sustaining a balanced, readily available nutrient supply to the potato plant shows potential as an untapped means of expanding yields and improving disease control. KTS may be the tool that is needed to achieve this. An on-farm study this year will compare biweekly application of KTS from planting to vine death to no supplemental K in any form. This will test the prevailing philosophy that Colorado soils intrinsically have sufficient K for potato production, and demonstrate the flexibility and efficacy of KTS. Dr. Zink is extension potato specialist at the San Luis Valley Research Center Colorado State University.
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