Interpretive Summaries:

Banana requires large doses of potassium (K) to produce top yields of quality fruit. However, high K rates could imbalance soil calcium (Ca) and magnesium (Mg) and thereby reduce yield. A field study designed to determine the best K:Ca:Mg ratio to maintain high yields and sustain an adequate use of K was planted in a high K soil, representative of banana soils of the region. Earlier research proved that normal banana production needs an annual application of K to sustain yields, even in soils with high content.

First year yields were high (average of 2,800 exportable boxes/ha/year), but did not show a significant difference between K rates. However, soil K content dropped from 1.38 cmol₍₊₎/kg to 0.52 in the control plot at the beginning of the second year. Soil K content at the end of the second production cycle increased in all treatments, including the check, due to recycling of nutrients from residues produce in the first cycle. Despite the increase in the control, the residue effect failed to raise the soil K content to normal levels (0.83 cmol₍₊₎/kg).

Application of 600 kg K₂O/ha maintained a constant soil K content (1.0 cmol₍₊₎/kg) in the first and second cycles, which sustained banana yields. Yields in the second cycle were stable, and there was no response to K. The effect of K mining in the check and low K rate treatments was not yet evident due to the influence of K recycling from crop residues. There was no effect of K application on Ca and Mg content in the plant at this point in the experiment. COSTA RICA-07