Influence of planting depth and intra row spacing on Growth, seed tuber yield and quality of potato (solanum tuberosum l.) At holetta condition, central Highlands of Ethiopia

Planting depth and intra row spacing are among the important agronomic practices in potato seed production. However, farmers in Ethiopia often use haphazard planting depth and intra row spacing, which contributes to the low yield. Thus, the study was conducted to assess the effect of planting depth and intra row spacing on growth, seed tuber yield and quality of potato under Holetta condition, during 2015 off growing season. Four levels planting depth (12cm, 15cm, 18cm and 21cm) and intra row spacing (15cm, 20cm, 25cm and 30cm) were combined in 4x4 factorial arrangements and laid out in randomized complete block design with three replications. Data were collected on growth, seed tuber yield and physical quality parameters and analyzed using SAS Version 9.0 statistical software. Results revealed that both the main and interaction effect of planting depth and intra row spacing significantly (P< 0.05) influenced most parameters studied except for main stem number, specific gravity and dry matter content. Deeper planting (21cm) delayed emergence, flowering and physiological maturity by about 6.16, 8.76 and 8.08 days, respectively, and plant height decreased by 3.67cm compared to planting depth of 12cm. Similarly, heaviest average tuber weight and high number of large sized tubers were gained from depth of 21cm while depth of 18cm resulted in higher a verge tuber yield. Plants grown at intra row space of 30cm took significantly longest days to flower and physiological maturity and the shortest in plant height than those grown intra row spacing of 15cm. The average tuber yield per hill, average tuber weight, large sized tuber number and yield produced at intra row spacing of 30cm is significantly (P<0.05) higher than those obtained from intra row spacing of 15cn by 33.37,23.16,47.64 and 36.67 %, respectively. The interaction of 18cm x30cm depth and intra row spacing resulted in highest average number of tubers while combination of closer intra row (15cm) with deeper (21cm) and shallow depth (12cm) resulted in the lowest one. The highest number and yield of total and marketable tuber number and yield were harvested at the interaction of 18cm x 15cm depth. Whereas, the lowest marketable number and yield of tubers was obtained from the shallow depth (12cm) combined with wider intra row spacing (30cm). Similarly, potato planted at 18cm x15cm depth and intra row spacing resulted in maximum number and yield of under, small and medium sized tubers. In conclusion, most studied yield and quality parameters of the tested variety had superior response to interaction effect of 18cm x 15cm, 15cmx15cm and 18x20cm depth and intra row spacing. Therefore, planting depth of 15cm and 18cm combined with intra row of 15and 20cm can be used as preliminary information for further investigation of high marketable and better quality seed tuber yield. However, the present study was done only for one season at one location; it would be advisable to repeat the experiment for more number of years and locations to come up with comprehensive recommendations