Response to fertilization and nutrient deficiency diagnostics in peach palm in Central Amazonia

Abstract

Peach palm (Bactris gasipaes Kunth) is increasingly grown in the tropics for its heart-of-palm and fruit. Determining fertilization response and diagnosing nutrient status in peach palm may require methods that consider the particularities in nutrient acquisition and recycling of perennial crops. Responses to nutrient additions, and the diagnostic value of soil and foliar analyses were examined in three field experiments with three-year old peach palm stands on Oxisols in Central Amazonia. To diagnose P-deficiency levels in soils, samples from 0–5 cm and 5–20 cm depth were analyzed for available P by different methods (Mehlich-1, Mehlich-3 and Modified Olsen). The second and fifth leaves were analyzed to assess N, P and K deficiencies. Field experiments involved several combinations of N (from 0 to 225 kg ha⁻¹ yr⁻¹), K (from 0 to 225 kg ha⁻¹ yr⁻¹) and P (from 0 to 59 kg ha⁻¹ yr⁻¹). Palms on control plots (unfertilized) and those receiving 225 kg ha⁻¹ yr⁻¹ N and 2 Mg ha⁻¹ of lime yielded between 4 and 19% of the maximum growth which was obtained with N, P and K applications. In one of the experiments, yield of heart-of-palm was positively related to N additions at the lowest levels of P (8.6 kg ha⁻¹ yr⁻¹) and K (60 kg ha⁻¹ yr⁻¹) additions. In one experiment, critical leaf N level was 2.5% for the second leaf and 2.2% for the fifth leaf. Some growth responses to P additions at constant N and K levels were observed (e.g., 797 kg ha⁻¹ yr⁻¹ of heart-of-palm with 39.3 kg ha⁻¹ yr⁻¹ of applied P, and 632 kg ha⁻¹ yr⁻¹ of heart-of-palm with 10.9 kg ha⁻¹ yr⁻¹ of applied P in one experiment, and 2334 kg ha⁻¹ yr⁻¹ of heart-of-palm with 39.3 kg ha⁻¹ yr⁻¹ of P and 1257 kg ha⁻¹ yr⁻¹ of heart-of-palm with 19.7 kg ha⁻¹ yr⁻¹ of P in another trial). In the experiment for fruit production from peach palm, total plant height did not respond to P additions between 19.7 and 59 kg ha⁻¹ yr⁻¹ and K additions between 75 and 225 kg ha⁻¹ yr⁻¹. Leaf P levels were found to be above the proposed critical levels of 0.23% for the third leaf and 0.16% for the fifth leaf. Plants in this experiment, however, showed evident symptoms of Mg deficiency, which was associated with a steep gradient of increasing Mg concentration from the fifth leaf to the second leaf. Standard leaf diagnostic methods in most cases proved less useful to show plant N and P status and growth responses to N and P additions. Soil P determined by common extractions was in general too variable for prediction of growth.