Response of maize and sesame in relay cropping to phosphorus and potassium in La Maquina, Guatemala

A study was conducted at Semilla Nueva’s La Maquina Research Station in Guatemala on the response of maize and sesame to P and K. Three application rates of P (0, 100, and 200 kg P₂O₅/ha) and three of K (0, 100, and 200 kg K₂O/ha) were combined in a complete factorial arrangement, with three replications.

Maize grain (14%) yields were very low when no P was applied, regardless of the K rate: 390, 310, and 805 kg/ha for 0 P₂O₅+0 K₂O, 0 P₂O₅+100 K₂O, and 0 P₂O₅+200 K₂O kg/ha, respectively. Significant increases in yield were observed in plots treated with 100 kg P₂O₅/ha: 3,980 kg grain/ha when no K was applied, and 3,320 kg grain/ha when 200 kg K₂O/ha were also used. But the highest maize yields were measured when 200 kg P₂O₅/ha were applied: 5,140 kg/ha, when no K was applied, and 5,230 kg/ha when combined with 100 kg K₂O/ha. The latter grain yields were not statistically different among themselves, but significantly higher that when 100 kg P₂O₅/ha were used. The dramatic maize yield response to applied fertilizer is noteworthy (391 kg/ha in unfertilized soil compared with 5, 230 kg/ha). Sesame grain (6%) yields showed a significant response only to P application: 355, 798, and 809 kg/ha, for 0, 100, and 200 kg P₂O₅/ha.

These results confirm those found in other studies in the same location about the critical role of P for attaining a balanced nutrition either in maize or sesame, and the lack of response to potassium. These findings can be explained by the low natural P availability likely associated to the presence of volcanic amorphous high P-fixing minerals, and the relatively high exchangeable K level in the soils.