TOWARDS A MARKETABLE SIZED SWEET POTATO (Ipomoea batatas) Jacklyn Broomes, Food Crop Agronomist Anderson Eversley, Extension Officer (Independents) ARVTU, BAMC

IMPORTANCE of SWEET POTATO to BAMC & BARBADOS Highest income earner among food crops at BAMC. Excellent crop for use in rotation with sugar-cane. Occupies large land areas. One of the few domestically produced commodities that is competitive with the imported product.

CONSTRAINTS Limited information regarding yields of local cultivars. Prevalence of large tubers (<500g) which are rejected by average householder. Few tubers per plant. Difficult to forecast yields per unit area.

RATIONALE To have an increase in the amount of marketable tubers produced at the BAMC. BAMC’s sweet potato is planted on single rows with 1 to 1.5 ft intra-row spacing and 5 ½ ft inter-row. As spacing increases, the total number of tubers decreases, while the yield of larger tubers increases. (Schultheis, Walters and Adams, 1999).

(Agronomic Trial)

OBJECTIVES To determine the effect of cultivar and single- and double-row planting on the yield of four sweet potato cultivars. To determine average yield per acre for each cultivar.

METHODOLOGY Trial established at Groves, St. George; smectoid clay, average drainage, responds well to tillage. Split plot design. Four (4) cultivars used: ‘Caroline Lee’ ‘CBS 32’ ‘CBS 49’ ‘C104’

Single-row: 1 ft intra-row; 5 ½ ft inter-row; middle of bed. Double-row: 1 ft intra-row; 2 rows on single bed 1 ½ ft apart. Fertilized with MAP at planting (2 bags/ acre). Tubers were harvested when the following were observed: Vine senescence. Flowering. Exudation of white latex from cut tuber.

Description of cultivars used Skin Colour Flesh Colour Shape of Tuber Time to Maturity 1. ‘Caroline Lee’ White/ Cream Round 3 - 4 months 2. ‘CBS 32’ Red-Brown Deep Orange Oval 3. ‘CBS 49’ Cream Orange Elongated 3months 4. ‘C104’ Red

‘C104’

‘Caroline Lee’

‘CBS 32’

‘CBS 49’

Left to right: ‘C104’, ‘Caroline Lee’, ‘CBS 32’, ‘CBS 49’ (washed)

Left to right: ‘CBS 49’, ‘CBS 32’, ‘Caroline Lee’, ‘C104’.

RESULTS AND DISCUSSION

EFFECT OF CULTIVAR ON YIELD Significant effect on tuber count/ plant, length and width of tuber (mm) and the average weight per tuber (g). ‘C104’ showed the greatest yield potential. ‘C104’ had the lowest number of tubers per plant at 4.9, highest average weight/ tuber (230.4 g), highest total weight of tubers per plant at 1008.1 g.

Cultivar ‘CBS 32’ averaged the highest number of tubers per plant at 6 Cultivar ‘CBS 32’ averaged the highest number of tubers per plant at 6.5 but lowest average weight/ tuber of 138.8 g and the lowest total weight of tubers per plant (876.4 g). The average weight of the tubers from all cultivars < 500 g. Tubers would be acceptable on the fresh market for household consumers.

Average Weight/ Tuber (g) Total Weight of Tubers per Plant (g) Effect of cultivar on yield Parameter Tuber Count/ Hole Length (mm) Width (mm) Average Weight/ Tuber (g) Total Weight of Tubers per Plant (g) ‘Caroline Lee’ 5.2±2.2 b 108.0±30.4 a 61.0±14.0 a 194.5±90.4 a 957.2±467.1 ‘CBS 32’ 6.5±2.4 a 104.6±13.3 a 51.1±9.1 c 138.8±61.2 b 876.4±484.7 ‘CBS 49’ 5.0±2.4 b 130.3±22.9 b 53.0±15.3 bc 220.3±170.7 a 946.5±568.9 ‘C104’ 4.9±1.8 b 125.4±57.5 b 58.2±29.6 ab 230.4±134.6 a 1008.1±525.6 Average 5.4±2.3 117.1±36.6 55.8±18.9 196.0±126.0 947.0±512.0

THE EFFECT OF SINGLE- AND DOUBLE-ROW PLANTING ON YIELD Significant effect on the all parameters of yield with the exception of width (mm). With an increase in rows per bed, there was a subsequent decrease in yield. The increase in rows resulted in increased competition for limited resources (Schultheis, Walters and Adams, 1999). Lead to production of smaller tubers.

Effect of single- and double-row planting on yield Parameter Tuber Count/ Hole Length (mm) Width (mm) Average Weight/ Tuber (g) Total Weight of Tubers per Plant (g) Single-row 6.3±2.3 a 124.7±31.2 a 58.9±13.9 246.7±160.4 a 1298.7±573.4 a Double-row 5.0±1.9 b 113.3±38.6 b 54.3±20.9 170.7±95.6 b 771.2±370.7 b Average 5.4±2.3 117.1±36.6 55.8±18.9 196.0±126.0 947.0±512.0

THE EFFECT OF THE INTERACTION OF CULTIVAR AND SINGLE- AND DOUBLE-ROW SPACING ON YIELD For most parameters, there was a decrease in the value from the single-row planting to double-row. The percentage change in the tuber count/ hole ranged from 1.9% for ‘CBS 49’ to 28.1% for ‘Caroline Lee’. ‘CBS 49’ is less responsive is terms of the number of tubers it produces with increased competition; cultivar trait.

Effect of interaction of cultivar and single and double-row planting on yield % Change* in Tuber Count/ Plant % Change in Length of Tuber % Change in Width of Tuber % Change in Average Weight/ Tuber % Change in Total Weight of Tubers/ Plant ‘Caroline Lee’ (28.1) (21.3) 0.7 (35.7) ‘CBS 32’ (27.5) 2.7 (7.6) (16.8) (43.5) ‘CBS 49’ (1.9) (10.7) (26.2) (31.4) (44.7) ‘C104’ (18.1) (2.4) 4.1 (16.7) (38.5) Total (20.6) (9.1) (7.8) (30.8) (40.6)

Projected average yields per acre Cultivar Plants per Acre (Single-Row) Average Yield per Acre (kg) – Single-Row (Double-Row) Average Yield per Acre (kg) – Double-Row % Increase in Yield ‘Caroline Lee’ Approx. 7 920 9945.1 15 840 12798.7 28.7 ‘CBS 32’ 9775.7 11048.4 13.0 ‘CBS 49’ 10680.9 11807.1 10.5 ‘C104’ 10740.3 13212.1 23.0

Total yield per acre (kg) increases from single- to double-row planting for each cultivar. The doubling of the number of plants within the acre aided the increase in the total yield per acre. Although these increased yields are encouraging, an economic analysis of the spacing data should be undertaken to determine true benefit (Schultheis, Walters and Adams, 1999).

CONCLUSIONS ‘C104’ showed greatest yield potential while ‘CBS 32’ shows the least. Double-rows resulted in lower yields per plant among sweet potato cultivars but resulted in increased average yields per acre. Both single- and double-row planting resulted in tubers that are ideal for sale on the local fresh market. Suggestions should not be made toward double-row planting for an increase in yield until an economic analysis of all factors is conducted.

(Economic Analysis)

RATIONALE “Technical efficiency”. Measures the ability of a farm to obtain maximal output from a given set of inputs (output-oriented measures); or use the minimum feasible amount of inputs to produce a given level of output (input-oriented measures).”

OBJECTIVES To quantify economic feasibility of double-row planting of sweet potato as a production method within the BAMC setting.

RESULTS AND DISCUSSION

ENTERPRISE BUDGET Rain-fed double-row production on a per acre basis. Revenue sweet potato-1584(4) rods per acre@ $10.00 per rod = $15840.00 The cost per acre of growing double-row sweet potato is $2826.91. A return of $13013.09 is made from in field sales at the farm gate from this activity.

Partial Budget: Substitution of one acre of sugar cane for one acre of double-row sweet potato LOSSES GAINS Income Lost New Income One acre of sugarcane-CPC@ 25 tns @ $ 60.00 per tonne $1500.00 One acre of sweet potatoes 1584 rods per acre@ $10:00/rod $15840.00 New Costs Costs saved Disc ridging/ acre of sweet potatoes =$49.25 Manual weeding /acre of sweet potatoes 2 manual weeding-4 workers @ $100.00=$200.00 Ploughing 1 pass/acre of sugar cane- =$71.64 Rock picking/ acre of sugar cane - =$98.87 Fertilizer application/acre of sugar cane =$421.54 2 manual sprayings of sugarcane =$ 195.78 Pest/ disease Control of sweet potatoes –pesticide control- 2 applications $ 75.36 Spring-tining/ acre of sugar cane =$13.25 Infield sales of sweet potatoes 1employee( 5 days ) = $323.20 Mechanical reaping/acre of sugar cane =$841.12 Total Costs: $2147.81 Total benefits: $17482.20 Net gain $15334.39 Net loss TOTALS: $17482.20 $17482.20

Crop Biol. yield/ acre (kgs) Sales Rev. Cost of Product Net Returns Price Unit(kg) Cost/ Unit (kg) Ave. Yield per rod/kgs (Rod) Net returns % Returns ‘C. Lee’ 12798 $15840 $2826 $13013 $1.23 $0.22 8.08 $1.78 $1.01 82.15 ‘CBS 32’ 11048 $1.43 $0.26 6.98 $1.18 ‘CBS 49’ 11807 $1.34 $0.24 7.45 $1.10 ‘C104’ 13212 $1.20 $0.21 8.34 $0.98

CONCLUSIONS Double-row sweet potato production is a land saving device with tangible output and revenue enhancing benefits. Local and international research indicates that double-row sweet potato production results in a more marketable tuber with enhanced saleable value. Double row sweet potato production has the potential to increase revenue gained from sales on a per acre basis to the producer.

RECOMMENDATIONS Replication of the double-row sweet potato study within different agro-ecological areas to closely examine links between individual cultivars and yield. Full commercialization of the double-row system of production by BAMC food crop unit, once further agronomic and economic research and evaluation validates its productive worth to BAMC.

ACKNOWLEDGEMENTS Dr. S. Bellamy – Unit Head, ARVTU. Technical and Field Staff, ARVTU. CBS – Supply of planting material.

THE END Thank you! jacklyn.broomes@gmail.com everzley@gmail.com