Potatoes are tubers that grow underneath the ground. The most important abiotic factors that affect the growth of tubers like potatoes are the - water supply, photo-period, and the temperature.
Since Suzy and Sara, both planted the potatoes at the same time in the same area, it is obvious that their plants were growing in conditions with the same temperature and photoperiod. However, the water supply, compost, and nutrients in the soil could have been taken up by one row of the plants. This would have left little water and nutrients available for the second set of plants. So, 1 set of plants grew well and gave big round potatoes, while another set did not give any potatoes.
