Effect of Planting Depth and Time of Earthing-up on Potato (Solanum Tuberosum L.) Yield and Yield Components at Jimma University College of Agriculture and Veterinary Medicine, South West Ethiopia

Abstract

Potato (Solanum tuberosum L.) is the fastest growing staple food crop and source of cash income for smallholder farmers in Ethiopia. An experiment was conducted at Jimma, Southwest Ethiopia during 2014/15 cropping season to determine the effect of different planting depth and time of earthing-up on yield and yield components of Jalane potato variety. The treatments consisted of 3 levels of planting depth (10, 12 and 14 cm) and four time of earthing-up (no earthing-up, at 15, 30 and 45 days after plant emergence) were applied to Jalane potato variety. A 3x4 factorial experiment was laid out with 3 replications. Data collected on yield, and yield components were analyzed using SAS Version 9.2 statistical software. Earthing-up at 15 days combined with planting depth of 10 and 12 cm recorded significantly (P<0.01) the highest total tuber number. Planting at 12 cm depth resulted in significantly the highest tuber weight, where as 10cm planting depth gave the highest unmarketable yield. Earthing-up at 15 days produced significantly (P<0.01) the highest main stem number. Moreover, earthing up at 15 days produced average tuber weight of 10.28%, which is higher as compared to the no earthing-up. Earthing-up at 15 days, 30 days and 45 days showed reduced unmarketable tuber yield by 13.62%, 7.51% and 3.52 %, respectively as compared to no earthing-up. Time of earthing-up  with depth of planting at (15days x10cm, 15days x12cm, 15days x14cm, 30days x12cm, 30days x14cm and 45days x14cm)  recorded the minimum number of green tubers (1.48, 1.16, 0.63, 1.23, 1, 1.56) respectively.  Earthing-up at 15 days and at planting depth 12 cm produced the highest marketable yield (23.92 and 23.57ton/ha, respectively),also earthing up at 15 days and planting depth at 12 cm produced the highest total tuber yield (28.28 and 26.72ton/ha, respectively). Even though early earthing-up was superior when compared to very late earthing-up and no earthing-up with regard to different parameters, where as no earthing-up and shallow planting depth performed very poorly. Correlation analysis result showed that the association between all parameters was positive and highly significant. While the number of green tuber and unmarketable yield was negatively and highly significantly (P<0.01) correlated. Therefore, based on the result of this investigation, optimum planting depth at 12cm and earthing up at 15 day is recommended for the potato growers in the study area.. Since, the present study was done only for one season at one location; it would be advisable to repeat the experiment at various agro-ecological conditions to come up with conclusive result leading to a recommendation.

Keywords: Jalane potato, planting depth, Time of earthing-up, Yield, Yield Components.