Effect of biochar and foliar of potassium and calcium applications on the concentration of nutrients and yield of grapes (Vitis venifera cv.Lal)

The use of crop residues in agricultural lands and foliar application of nutrients on the aerial parts of fruit trees can be a suitable alternative for supplying soil nutrients. An experiment was conducted in the form of a randomized block design with 6 treatments and 4 replications on Lael grape trees in one of private vineyards in Shahrood city. The treatments include control (C), biochar (BC) in the amount of 1 kg for each vine, potassium (FK) and calcium (FCa) fertilization in the amount of 100 grams of potassium sulfate and calcium sulfate for each vine, potassium (SK) and Calcium (SCa) was 10 grams each of the respective sulfates in 5 times. The results showed that the highest concentrations of potassium and calcium in soil solution were observed in the BC treatment. Fruit potassium concentration showed a significant increase in FK and SK treatments compared to the control. The calcium concentration of the fruit was the highest in the FCa treatment followed by the SCa treatment, and the highest number of clusters (20.75 clusters per vine) and yield (12.05 kg per vine) were observed in the SCa treatment, which increased the yield by 38% compared to the control. An important point is that in almost all treatments, the potassium concentration of grapes in the lower parts of the bunch was higher than in the upper parts, and the opposite situation was observed for calcium in the control and SK treatments. The ratio of potassium to calcium in the lower parts of the clusters in control and SK treatments was 7.8 and 8.3, respectively, which was much higher than other treatments. In addition, the two mentioned treatments showed the lowest yield among the treatments.