Response of the maize-sesame-pigeon pea association to N, P, and K at La Máquina, Guatemala

La Máquina is an important agricultural area in the Southwestern coast of Guatemala. Maize is usually grown in association with sesame, and increasingly with pigeon pea. This project was started in 2014 at the Semilla Nueva Experiment Station to determine the response of maize, sesame and pigeon pea to N, P and K.

The soil had pH of 6.2, 2.6% organic matter, <10 ppm Mehlich-3 P, a cation exchange capacity of 12.3 cmol/kg, 0.39 cmol/kg K, 8.31 cmol/kg Ca, 3.6 cmol/kg Mg, 7 mg/L S, 5 mg/L Cu, 172 mg/L Mn, and 1.6 mg/L Zn. The following nutrient rates were arranged in a complete factorial design with three reps: N (0, 100 and 250 kg/ha); P₂O₅(0, 100 and 200 kg/ha); and K₂O (0, 100 and 200 kg/ ha). All the P and K were applied at planting. Nitrogen was split: 50% at planting and 50% 30 days later. The fertilizers were placed in 5-cm deep holes located 5 cm from the plants. Urea, triple superphosphate, and potassium chloride were the sources.

The average maize yield (2.0 t/ha) was low because of the severe drought that affected the region. Only significant effects from N and P were detected on maize yield, whereas sesame yield was not statistically affected by the treatments. Maize yield peaked at an application of 142 kg N/ha, whereas it increased significantly with 200 kg P₂O₅/ha as could be expected from the very low available P in the soil. Maize leaf analysis results consistently showed B as the most limiting nutrient. All the N use efficiency indicators showed low values. The lack of water might have limited N utilization as indicated by the low NUEs. Higher N rates could have led to greater soil water depletion, through the promotion of greater vegetative growth before the drought, which could explain the yield decrease observed.