Plant population
Plant population or plant density is very important for tuber yield and quality. The unit of population in potato is the main stem number and about 25 main stems per square meter is advocated, High density results in greater number of small size tubers and lower yield per plant, while low density decreases the yield per unit area. Moreover, varying the plant density changes the gross to net yield relationship and with increase in gross yield the net yield need not necessarily increase. Hence, an optimum plant density is required to be worked out depending upon the variety, purpose of the crop, season etc. Higher plant population is required in seed crop to get small sized seed tubers while for processing a lower plant population is desirable to get a higher proportion of large sized tubers. The plant population can be manipulated by changing the planting geometry by adjusting the inter and intra row spacings.
In general, when planting medium size tubers (40-45 g), 1,11,000 plants/ha are optimum for maximum production of seed size tubers. This can be achieved by planting the seed tubers at 60 X 15 cm. When small size seed tubers (10-20 g) are planted, a density of 1,66,000/ha is the optimum for more number of seed size tuber production. For achieving maximum yield of tubers weighing less than 50 g in the produce, a planting density of 2,50,000/ha is required and this can be achieved by planting small tubers (10-20 g) at 40 X 10 cm.
For ware potato production, a plant density of 1,66,000 plants/ha is optimum when using small tubers (10-20 g), which can be achieved by planting manually at 40 X 15 cm. For medium size tubers a plant population of 83,000 to 1,11,000 plants/ha is optimum which can be obtained by planting at 60 X 20 cm or 60 X 15 cm. Large size tubers of more than 50 g may be cut into two to three pieces to economise on seed rate and then used to achieve planting density of at least 1,00,000 plants/ ha. When cut seed pieces are used, planting should be delayed so that maximum temperature is not above 250C to prevent seed piece decay.