Nutritional diagnosis in cactus pear under different fertilization and harvest managements in semi-arid conditions

The nutritional management of cactus pear can be improved by the use of tissue analysis of cladodes, through the interpretation of results by the Kenworthy Balanced Index (KBI). The aim of this study was to evaluate the nutritional status diagnosis in cactus pear cv. Gigante (Opuntia ficus-indica), fertilized with combinations of nitrogen (10, 70, 100, 130, and 190 kg ha-1 yr-1 N) and phosphorus (10, 70, 100, 130, and 190 kg ha-1 yr-1 P2O5) under annual and biennial harvest frequencies, through the interpretation of the Kenworthy Balanced Index (KBI). The study was carried out under the semi-arid conditions of Quixadá and Tejuçuoca, state of Ceará, Brazil. A randomized complete block design was adopted in split-plot arrangement with four replications. In order to generate the diagnostic indexes by the KBI method, the population was divided into two sub-populations, based on productivity: above and below 1,786.0 and 8,150.1 kg ha-1 yr-1 for Quixadá and Tejuçuoca, respectively. In the conditions of Quixadá and Tejuçuoca, the combined levels of N and P, in the annual and biennial harvest frequencies, influenced the nutrient content in the cladodes of cactus pear. Generally, in both regions, the estimated contents of N, P, K, Ca, Mg, S, B, and Fe using levels for maximum production and 90% of maximum production are within the proper range (or with values very close to the normal range limits), as defined by the KBI. The diagnostic indexes (reference values) developed for interpretation of results of cladode analyses, were different between the regions of Quixadá and Tejuçuoca. In Quixadá, the diagnosis indicates greater nutritional limitation due to deficit of N and excess of S. In Tejuçuoca, the study shows Zn as the most limiting nutrient due to nutritional deficiency and Ca and Fe as the two most limiting due to excess.