Effect of Sources and Rates of Potassium on Quality and Yield of Mulberry Leaves in Gilan

A completely randomized complete block experiment with three replications using three rates of potassium (100,200,300 kg K₂O/ha) and two potassium sources (potassium chloride and potassium sulfate) and one treatment without any potassium as the control was carried out in four locations, namely, Rasht, Fuman, Sumehsara and Langeroud of Gilan province during 1998-99 growing seasons to study the effect of potassium sources and rates on the yield and quality of mulberry leaves. The soil available potassium levels were below 250 mg/kg at all locations. The results of 2- year experiment show that: There was no significant difference in the weight of mulberry leaves at Pasikhan farm of Rasht region. However, the greatest weight of mulberry leaves and twigs was obtained with A₃B₂ (300 kg/ha K₂O as potassium chloride) which was significantly (at 1-% level) different from A₁B₁ (100 kg K2O/ha as potassium sulfate) and the control (without any potassium application), but statistically the same as the yield from other treatments. There was also a significant difference (at 1-% level) in terms of leaf potassium contents between the control and all the other treatments, while treatment 5, A3B1, with a leaf potassium of 1.6% yielded the highest (the leaf K for the control was 1.0 per cent). There were no significant differences in the weight of leaves or leaves and twigs among the various treatments for the experiment at the Parand farm in Fuman region. However, there was a significant difference (at 1-% level) in leaf potassium contents between various treatments, so that treatment 3, A₂B₁ (200 kg K₂O/ha as potassium sulfate) and treatment 5, A₃B₁ (300 kg K₂O/ha as potassium sulfate) with 1.7% potassium produced the best results while the control (no potassium) with 0.97% leaf K was the lowest level. There were no significant differences in leaf weights or leaf potassium contents among the treatments at the Parnian farm of Sumehsara. However, there were significant differences (at 5-% level) in the weight of leaves and twigs between the treatments so that treatment 5, A₃B₁ with a yield of 6.73 kg/tree was significantly different from treatment 2, A₁B₂ with a yield of 4.45 kg/tree and from the control (no potassium) with a yield of 4.47 kg/tree. There were significant differences among the different treatments for parameters measured at the Shalman location of Langeroud, so that treatment 5, A₃B₁, produced 4.16 kg leaves per tree, which was significantly more than those of other treatments (at 1-% level) and was by comparison 49% more than the yield of 2.79 kg/tree obtained with the control. Treatment 5, A3B1 also produced the greatest weight of leaves and twigs, or 7.15 kg/tree, which was significantly (at 5-% level) higher than the values obtained with treatments 1, 2, and the control. With respect to leaf potassium contents every treatment produced results that were significantly different from that of the control (at 1-% level). It must be pointed out in conclusion that the observed differences measured with different factors were significant only with respect to the rates of applied potassium but not with respect to the two sources of potassium.