Nutritional value of cactus pear grown under different levels of nitrogen and phosphorus and two harvest frequencies

This study evaluated the effects of N/P fertilization on the chemical, mineral composition, and in vitro degradation kinetics of cactus pear cv. Gigante. The research was conducted in Quixada and Tejucuoca, CE, Brazil. Nine N/P combinations were evaluated from five levels of N (10, 70, 100, 130, and 190 kg ha(-1) year(-1)), five levels of P2O5 (10, 70, 100, 130, and 190 kg ha(-1) year(-1)), and two harvest frequencies (annual and biannual). The experiment was performed in a split plot completely randomized block design, with four replications. The maximum CP content was obtained in biannual harvest in Quixada and Tejucuoca with the combined levels N/P2O5 of 190/190 and 130.03/190 kg ha(-1) year(-1), respectively. Calcium content was reduced by fertilization, which allowed to reduce the Ca:P ratio to 9.72:1.00 with the N/P2O5 combination at 190/10 kg ha(-1) year(-1) in the biannual harvest. The increase in N and P levels results in higher S and Mn content and higher digestibility. The annual harvest improves quality in Quixada. However, it has weaker influence on quality in Tejucuoca. In Tejucuoca, Mg, Cu, and Mn contents are lower under annual harvest. Sulfur content is lower under annual harvest in both sites.