Morphophysiological and productive responses of spineless forage cactus to salinity levels in irrigation water and soil cover with organic residue

The objective of this study was to evaluate the effects of water salinity levels (0.1, 2.5, 5.0, 7.5 and 10 dS.m-1) and soil cover with rice husk on morphophysiology and productivity of spineless forage cactus cultivar IPA Sertânia (Nopalea cochenillifera) under water supplementation for two annual cycles. The experiment was conducted in Apodi-RN, Brazil. The treatments were randomized in strip-plot blocks. The salinity levels were applied in the plots, and the soil cover (presence or absence) in the subplots, with four replicates. Data were subjected to analysis of variance, regression and test of means, at 5% probability. The average drip irrigation depth was 4.0 mm week-1. The interaction between salinity levels and years was significant (P < 0.05) for fresh (FMP) and dry matter productivity (DMP), water use efficiency (WUE) and cladode thickness, with a negative response to the highest salinity levels in the first year and no effects in the second year (117 and 7 Mg ha-1 yr-1 of FMP and DMP, respectively). Soil cover promoted higher FMP (96 Mg ha-1 yr-1), number of cladodes per plant (10 units), thickness (2.1 cm) and area of cladodes (323 cm2) and lower dry matter content ( DM = 78 g kg-1). The second production cycle favored plant height (74 cm) and width (89 cm), number of cladodes (11 units), thickness (2.39 cm), perimeter (72 cm), length (31 cm), width (15 cm) and area of cladodes (323 cm2), but the DM content was lower (59 g kg-1). In this sense, the second productive cycle provided larger plants and cladodes. Rice husk cover and saline water could be used, provided under similar management and monitoring conditions as those applied in this trial, with replacement of soil cover, saline water of similar characteristics, water suppplementation and soil with satisfactory drainage.