Influence of combined application of potassium and sulfur on yield, quality, and storage behavior of potato

In a sand culture study, potato (Solanum tuberosum L.) was grown to maturity in the greenhouse to study the effects of factorial application of four levels, each of potassium (K) (2, 4, 8, and 12 meq L(-1)) and sulfur (S) (1, 2, 4, and 6 meq L(-1)), on yield, quality, and storage behavior of tubers. In general, the effect of K was more pronounced than that of S on overall crop performance. Increasing K and S levels in the nutrient medium increased tuber yield as well as dry matter content. The highest tuber yield and percent dry matter content was recorded at 8 meq K L(-1), which surpassed the lowest K level by 73% in tuber yield and by 2.5% in percent dry matter content. As compared to the lowest S level, application at 4 and 6 meq S L(-1) enhanced average tuber yield and percent dry matter content by 28 and 0.41%, respectively. Similarly, percent starch and protein content of the tuber were also highest at 8 and 12 meq K L(-1), surpassing the lowest K level by 8.3-8.4% and 3.2-3.3%, respectively. The effect of S levels was nonsignificant on starch content, while 6 meq S L(-1) exceeded the lowest S level by 1.8% in protein content. In contrast, reducing sugars of the tuber decreased gradually with the increase in applied K, revealing the role of K in lowering the tuber reducing sugars content of potato, important for maintaining commercially viable color of potato chips. However, increase in S application did not affect the tuber reducing sugars significantly. Leaf N content was highest at 12 meq L(-1), increasing progressively with increasing N levels. Whereas, leaf K and S contents were highest at 8 and 4 meq K L(-1), respectively, decreasing significantly thereafter. Increasing S levels increased S content, but decreased tissue K content, significantly. Nitrogen levels increased with 2 meq S L(-1), but did not increase thereafter with increasing levels of applied sulfur. 8 meq K x 6 meq S L(-1) proved the best Interaction both for tuber yield and dry matter content. Potassium, applied with sulfur, also improved the shelf life of tubers, determined as the percent weight loss of tubers after the storage of four weeks at room temperature, the best interaction with lowest tuber moisture loss being 12 meq K L(-1) x 6 meq S L(-1).