Assessing sweet potato varieties for organic production of food and biofuel in Kentucky

JON CAMBRON, MICHAEL BOMFORD, TONY SILVERNAIL, JONI NELSON and College of Agriculture, Food Science and Sustainable Systems, Kentucky State University, 400 East Main St., Frankfort, KY 40601 (270)929-3036,

jon.cambron@kysu.edu

Abstract Kentucky State University’s College of Agriculture, Food Science and Sustainable Systems is dedicated to assisting small, limited-resource, and minority farmers. Organic sweet potato production is being explored as a high-value, low-input enterprise for Kentucky farmers selling into food markets, with culls used for on-farm production of ethanol fuel. Sweet potatoes suffer little pest pressure in Kentucky, have a low nitrogen requirement, and are drought tolerant. They produce up to three times more carbohydrate per acre than corn, the current dominant ethanol feedstock. Trials on organic land in 2011 and 2012 compared yield and quality characteristics of two experimental sweet potato varieties developed for ethanol feedstock production (CX-1 and 7-24); and two popular food varieties (Beauregard and Hernandez). An experimental food variety bred for high anthocyanin content (Stokes Purple) was also included in the trial in 2012. Hernandez and Stokes Purple produced the lowest yield, with 4 and 5.5 tons per acre, respectively. The biofuel variety CX-1 gave the highest yield, with just under 10 tons per acre in both years. The biofuel varieties averaged 20-25% dry matter, while the food varieties averaged 15-23%. The new biofuel varieties show promise for increasing both food and biofuel feedstock yields from low-input farms.

Introduction

Sweet potato • Drought tolerant • Low nitrogen requirements • Grows well in KY heat and humidity • High carbohydrates/acre • Long storage life

Varieties studied

Factors recorded for each variety • Yields • Number of tubers per acre

Beauregard CX-1

7-24 Stokes Purple

Hernandez

• Dry Matter Content • Rainfall per season

Results and Conclusions Materials and Methods In 2011, four varieties of sweet potatoes were grown and in 2012 five

varieties were grown on certified organic land.

Started w/ shoots of last year tubers Prepared with spader and rototiller

21 Shaped beds, 25’ long, spaced 6’ apart, with 12” between plants

Each bed had 25 plants of a single variety.

Prior to harvest, vines were flail mowed with a BCS flail mower.

Sides of beds were loosened with Farmall

belly mounted cultivators.

D10T Chain digger used to harvest tubers

Tubers were placed in separate bins to count and weigh

After count and weight was recorded a subsample (3 tubers) was taken from each bed. The subsamples were sliced and dried to obtain % dry matter content.

0

5

10

15

20

Cumulative rainfall (inches)

2011

2012

Conclusion CX-1 appears to show greater potential for biofuel production in Kentucky than other sweet potato varieties tested. Taste panels and nutritional analyses are needed to determine Its suitability for food production.

Bars labeled with the same letter are not significantly different (t-test, P<0.05 )

Bars labeled with the same letter are not significantly different (t-test, P<0.05)

Bars labeled with the same letter are not significantly different (Tukey, P<0.05)

Bars labeled with the same letter are not significantly different (Tukey, P<0.05)