Role of Potassium in Modifying the Potato Physiological Responses to Irrigation Regimes Under Different Planting Patterns

The evaluation of potato’s responses to potassium fertilizer and planting pattern under water shortage condition may help identify the factors affecting plant resistance to water deficit. In this regard, an experiment was conducted with three replications aiming to explore the effects of different levels of irrigation (60, 80 and 100% of crop water requirement) and potassium sulphate fertilizer (0, 75 and 150 kg K2SO4 ha−1; 0, 36 and 72 kg K ha−1) on some physiological parameters of potato in different planting patterns (double-rows, dense double-rows and zigzag double-rows) during the 2016 and 2017 cropping seasons. The results showed that the planting pattern had a significant effect on leaf potassium content and tuber yield, with the greatest values observed in the zigzag pattern. There was a significant reduction in chlorophyll a and b, leaf potassium contents and tuber yield and an increase in the amount of proline and phenol when plants were supplied with 60% of their required water. Applying potassium sulphate helped plants maintain chlorophyll content under these conditions through enhancing potassium uptake. When plants faced water shortage conditions, the amount of soluble sugars increased, with the lowest increase in plants supplied with 150 kg ha−1 potassium sulphate. Using 150 kg K2SO4 ha−1 led to the greatest tuber yield (27 and 30 t ha−1 in the first and second year, respectively), while the lowest tuber yield (24 t ha−1 in both years) was produced without potassium application. In general, it seems supplying potato plants with potassium sulphate can alleviate, at least partly, harmful effects of water shortage.